Commit | Line | Data |
---|---|---|
b10d79f7 | 1 | acpi= [HW,ACPI,X86,ARM64] |
03d926f8 | 2 | Advanced Configuration and Power Interface |
6a1f5471 | 3 | Format: { force | on | off | strict | noirq | rsdt | |
e58d154b | 4 | copy_dsdt } |
1da177e4 | 5 | force -- enable ACPI if default was off |
6a1f5471 | 6 | on -- enable ACPI but allow fallback to DT [arm64] |
1da177e4 LT |
7 | off -- disable ACPI if default was on |
8 | noirq -- do not use ACPI for IRQ routing | |
a9913044 | 9 | strict -- Be less tolerant of platforms that are not |
1da177e4 | 10 | strictly ACPI specification compliant. |
237889bf | 11 | rsdt -- prefer RSDT over (default) XSDT |
aa2110cb | 12 | copy_dsdt -- copy DSDT to memory |
6a1f5471 AB |
13 | For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force" |
14 | are available | |
1da177e4 | 15 | |
151f4e2b | 16 | See also Documentation/power/runtime_pm.rst, pci=noacpi |
1da177e4 | 17 | |
a1fdcc0d LB |
18 | acpi_apic_instance= [ACPI, IOAPIC] |
19 | Format: <int> | |
20 | 2: use 2nd APIC table, if available | |
21 | 1,0: use 1st APIC table | |
4e381a4f | 22 | default: 0 |
a1fdcc0d | 23 | |
c3d6de69 | 24 | acpi_backlight= [HW,ACPI] |
5fd769c2 RD |
25 | { vendor | video | native | none } |
26 | If set to vendor, prefer vendor-specific driver | |
c3d6de69 TR |
27 | (e.g. thinkpad_acpi, sony_acpi, etc.) instead |
28 | of the ACPI video.ko driver. | |
5fd769c2 RD |
29 | If set to video, use the ACPI video.ko driver. |
30 | If set to native, use the device's native backlight mode. | |
31 | If set to none, disable the ACPI backlight interface. | |
c3d6de69 | 32 | |
b2ca5dae CIK |
33 | acpi_force_32bit_fadt_addr |
34 | force FADT to use 32 bit addresses rather than the | |
35 | 64 bit X_* addresses. Some firmware have broken 64 | |
36 | bit addresses for force ACPI ignore these and use | |
37 | the older legacy 32 bit addresses. | |
38 | ||
ef69449b DB |
39 | acpica_no_return_repair [HW, ACPI] |
40 | Disable AML predefined validation mechanism | |
41 | This mechanism can repair the evaluation result to make | |
42 | the return objects more ACPI specification compliant. | |
43 | This option is useful for developers to identify the | |
44 | root cause of an AML interpreter issue when the issue | |
45 | has something to do with the repair mechanism. | |
46 | ||
a0d84a92 BH |
47 | acpi.debug_layer= [HW,ACPI,ACPI_DEBUG] |
48 | acpi.debug_level= [HW,ACPI,ACPI_DEBUG] | |
1da177e4 | 49 | Format: <int> |
a0d84a92 BH |
50 | CONFIG_ACPI_DEBUG must be enabled to produce any ACPI |
51 | debug output. Bits in debug_layer correspond to a | |
52 | _COMPONENT in an ACPI source file, e.g., | |
866d6cdf | 53 | #define _COMPONENT ACPI_EVENTS |
a0d84a92 BH |
54 | Bits in debug_level correspond to a level in |
55 | ACPI_DEBUG_PRINT statements, e.g., | |
56 | ACPI_DEBUG_PRINT((ACPI_DB_INFO, ... | |
e76f4276 | 57 | The debug_level mask defaults to "info". See |
cb1aaebe | 58 | Documentation/firmware-guide/acpi/debug.rst for more information about |
e76f4276 | 59 | debug layers and levels. |
a0d84a92 | 60 | |
e76f4276 BH |
61 | Enable processor driver info messages: |
62 | acpi.debug_layer=0x20000000 | |
a0d84a92 BH |
63 | Enable AML "Debug" output, i.e., stores to the Debug |
64 | object while interpreting AML: | |
65 | acpi.debug_layer=0xffffffff acpi.debug_level=0x2 | |
a0d84a92 BH |
66 | Enable all messages related to ACPI hardware: |
67 | acpi.debug_layer=0x2 acpi.debug_level=0xffffffff | |
68 | ||
69 | Some values produce so much output that the system is | |
70 | unusable. The "log_buf_len" parameter may be useful | |
71 | if you need to capture more output. | |
f989106c | 72 | |
ef69449b DB |
73 | acpi_enforce_resources= [ACPI] |
74 | { strict | lax | no } | |
75 | Check for resource conflicts between native drivers | |
76 | and ACPI OperationRegions (SystemIO and SystemMemory | |
77 | only). IO ports and memory declared in ACPI might be | |
78 | used by the ACPI subsystem in arbitrary AML code and | |
79 | can interfere with legacy drivers. | |
80 | strict (default): access to resources claimed by ACPI | |
81 | is denied; legacy drivers trying to access reserved | |
82 | resources will fail to bind to device using them. | |
83 | lax: access to resources claimed by ACPI is allowed; | |
84 | legacy drivers trying to access reserved resources | |
85 | will bind successfully but a warning message is logged. | |
86 | no: ACPI OperationRegions are not marked as reserved, | |
87 | no further checks are performed. | |
88 | ||
4fc0a7e8 LZ |
89 | acpi_force_table_verification [HW,ACPI] |
90 | Enable table checksum verification during early stage. | |
91 | By default, this is disabled due to x86 early mapping | |
92 | size limitation. | |
93 | ||
0cb55ad2 RD |
94 | acpi_irq_balance [HW,ACPI] |
95 | ACPI will balance active IRQs | |
96 | default in APIC mode | |
97 | ||
98 | acpi_irq_nobalance [HW,ACPI] | |
99 | ACPI will not move active IRQs (default) | |
100 | default in PIC mode | |
101 | ||
102 | acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA | |
103 | Format: <irq>,<irq>... | |
104 | ||
105 | acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for | |
106 | use by PCI | |
107 | Format: <irq>,<irq>... | |
108 | ||
6dddd7a7 | 109 | acpi_mask_gpe= [HW,ACPI] |
9c4aa1ee LZ |
110 | Due to the existence of _Lxx/_Exx, some GPEs triggered |
111 | by unsupported hardware/firmware features can result in | |
6dddd7a7 TB |
112 | GPE floodings that cannot be automatically disabled by |
113 | the GPE dispatcher. | |
9c4aa1ee LZ |
114 | This facility can be used to prevent such uncontrolled |
115 | GPE floodings. | |
d3121e64 | 116 | Format: <byte> or <bitmap-list> |
9c4aa1ee | 117 | |
08e1d7c0 LZ |
118 | acpi_no_auto_serialize [HW,ACPI] |
119 | Disable auto-serialization of AML methods | |
22b5afce BM |
120 | AML control methods that contain the opcodes to create |
121 | named objects will be marked as "Serialized" by the | |
122 | auto-serialization feature. | |
08e1d7c0 LZ |
123 | This feature is enabled by default. |
124 | This option allows to turn off the feature. | |
22b5afce | 125 | |
ef69449b DB |
126 | acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump |
127 | kernels. | |
128 | ||
a94e88cd LZ |
129 | acpi_no_static_ssdt [HW,ACPI] |
130 | Disable installation of static SSDTs at early boot time | |
131 | By default, SSDTs contained in the RSDT/XSDT will be | |
132 | installed automatically and they will appear under | |
133 | /sys/firmware/acpi/tables. | |
134 | This option turns off this feature. | |
135 | Note that specifying this option does not affect | |
136 | dynamic table installation which will install SSDT | |
137 | tables to /sys/firmware/acpi/tables/dynamic. | |
0cb55ad2 | 138 | |
3f9e12e0 JD |
139 | acpi_no_watchdog [HW,ACPI,WDT] |
140 | Ignore the ACPI-based watchdog interface (WDAT) and let | |
141 | a native driver control the watchdog device instead. | |
142 | ||
ef69449b DB |
143 | acpi_rsdp= [ACPI,EFI,KEXEC] |
144 | Pass the RSDP address to the kernel, mostly used | |
145 | on machines running EFI runtime service to boot the | |
146 | second kernel for kdump. | |
4dde507f | 147 | |
0cb55ad2 RD |
148 | acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS |
149 | Format: To spoof as Windows 98: ="Microsoft Windows" | |
150 | ||
18d78b64 RW |
151 | acpi_rev_override [ACPI] Override the _REV object to return 5 (instead |
152 | of 2 which is mandated by ACPI 6) as the supported ACPI | |
153 | specification revision (when using this switch, it may | |
154 | be necessary to carry out a cold reboot _twice_ in a | |
155 | row to make it take effect on the platform firmware). | |
156 | ||
0cb55ad2 | 157 | acpi_osi= [HW,ACPI] Modify list of supported OS interface strings |
5dc17986 LZ |
158 | acpi_osi="string1" # add string1 |
159 | acpi_osi="!string2" # remove string2 | |
741d8128 | 160 | acpi_osi=!* # remove all strings |
5dc17986 LZ |
161 | acpi_osi=! # disable all built-in OS vendor |
162 | strings | |
a707edeb LZ |
163 | acpi_osi=!! # enable all built-in OS vendor |
164 | strings | |
0cb55ad2 RD |
165 | acpi_osi= # disable all strings |
166 | ||
5dc17986 LZ |
167 | 'acpi_osi=!' can be used in combination with single or |
168 | multiple 'acpi_osi="string1"' to support specific OS | |
169 | vendor string(s). Note that such command can only | |
170 | affect the default state of the OS vendor strings, thus | |
171 | it cannot affect the default state of the feature group | |
172 | strings and the current state of the OS vendor strings, | |
173 | specifying it multiple times through kernel command line | |
741d8128 LZ |
174 | is meaningless. This command is useful when one do not |
175 | care about the state of the feature group strings which | |
176 | should be controlled by the OSPM. | |
5dc17986 LZ |
177 | Examples: |
178 | 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent | |
179 | to 'acpi_osi="Windows 2000" acpi_osi=!', they all | |
180 | can make '_OSI("Windows 2000")' TRUE. | |
181 | ||
182 | 'acpi_osi=' cannot be used in combination with other | |
183 | 'acpi_osi=' command lines, the _OSI method will not | |
184 | exist in the ACPI namespace. NOTE that such command can | |
185 | only affect the _OSI support state, thus specifying it | |
186 | multiple times through kernel command line is also | |
187 | meaningless. | |
188 | Examples: | |
189 | 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)' | |
190 | FALSE. | |
191 | ||
741d8128 LZ |
192 | 'acpi_osi=!*' can be used in combination with single or |
193 | multiple 'acpi_osi="string1"' to support specific | |
194 | string(s). Note that such command can affect the | |
195 | current state of both the OS vendor strings and the | |
196 | feature group strings, thus specifying it multiple times | |
197 | through kernel command line is meaningful. But it may | |
198 | still not able to affect the final state of a string if | |
199 | there are quirks related to this string. This command | |
200 | is useful when one want to control the state of the | |
201 | feature group strings to debug BIOS issues related to | |
202 | the OSPM features. | |
203 | Examples: | |
204 | 1. 'acpi_osi="Module Device" acpi_osi=!*' can make | |
205 | '_OSI("Module Device")' FALSE. | |
206 | 2. 'acpi_osi=!* acpi_osi="Module Device"' can make | |
207 | '_OSI("Module Device")' TRUE. | |
208 | 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is | |
209 | equivalent to | |
210 | 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"' | |
211 | and | |
212 | 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!', | |
213 | they all will make '_OSI("Windows 2000")' TRUE. | |
214 | ||
6cececfc | 215 | acpi_pm_good [X86] |
0cb55ad2 RD |
216 | Override the pmtimer bug detection: force the kernel |
217 | to assume that this machine's pmtimer latches its value | |
218 | and always returns good values. | |
219 | ||
4af94f39 RD |
220 | acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode |
221 | Format: { level | edge | high | low } | |
222 | ||
4af94f39 RD |
223 | acpi_skip_timer_override [HW,ACPI] |
224 | Recognize and ignore IRQ0/pin2 Interrupt Override. | |
225 | For broken nForce2 BIOS resulting in XT-PIC timer. | |
226 | ||
227 | acpi_sleep= [HW,ACPI] Sleep options | |
74d95555 DW |
228 | Format: { s3_bios, s3_mode, s3_beep, s4_hwsig, |
229 | s4_nohwsig, old_ordering, nonvs, | |
230 | sci_force_enable, nobl } | |
151f4e2b | 231 | See Documentation/power/video.rst for information on |
4af94f39 RD |
232 | s3_bios and s3_mode. |
233 | s3_beep is for debugging; it makes the PC's speaker beep | |
234 | as soon as the kernel's real-mode entry point is called. | |
74d95555 DW |
235 | s4_hwsig causes the kernel to check the ACPI hardware |
236 | signature during resume from hibernation, and gracefully | |
237 | refuse to resume if it has changed. This complies with | |
238 | the ACPI specification but not with reality, since | |
239 | Windows does not do this and many laptops do change it | |
240 | on docking. So the default behaviour is to allow resume | |
241 | and simply warn when the signature changes, unless the | |
242 | s4_hwsig option is enabled. | |
4af94f39 | 243 | s4_nohwsig prevents ACPI hardware signature from being |
74d95555 | 244 | used (or even warned about) during resume. |
4af94f39 RD |
245 | old_ordering causes the ACPI 1.0 ordering of the _PTS |
246 | control method, with respect to putting devices into | |
247 | low power states, to be enforced (the ACPI 2.0 ordering | |
248 | of _PTS is used by default). | |
72ad5d77 RW |
249 | nonvs prevents the kernel from saving/restoring the |
250 | ACPI NVS memory during suspend/hibernation and resume. | |
d7f0eea9 ZR |
251 | sci_force_enable causes the kernel to set SCI_EN directly |
252 | on resume from S1/S3 (which is against the ACPI spec, | |
253 | but some broken systems don't work without it). | |
57044031 RW |
254 | nobl causes the internal blacklist of systems known to |
255 | behave incorrectly in some ways with respect to system | |
256 | suspend and resume to be ignored (use wisely). | |
4af94f39 RD |
257 | |
258 | acpi_use_timer_override [HW,ACPI] | |
259 | Use timer override. For some broken Nvidia NF5 boards | |
260 | that require a timer override, but don't have HPET | |
261 | ||
4af94f39 RD |
262 | add_efi_memmap [EFI; X86] Include EFI memory map in |
263 | kernel's map of available physical RAM. | |
264 | ||
0cb55ad2 RD |
265 | agp= [AGP] |
266 | { off | try_unsupported } | |
267 | off: disable AGP support | |
268 | try_unsupported: try to drive unsupported chipsets | |
269 | (may crash computer or cause data corruption) | |
270 | ||
bcfde334 | 271 | ALSA [HW,ALSA] |
1ca2c806 | 272 | See Documentation/sound/alsa-configuration.rst |
bcfde334 | 273 | |
d944d549 RK |
274 | alignment= [KNL,ARM] |
275 | Allow the default userspace alignment fault handler | |
276 | behaviour to be specified. Bit 0 enables warnings, | |
277 | bit 1 enables fixups, and bit 2 sends a segfault. | |
278 | ||
dfb09f9b BP |
279 | align_va_addr= [X86-64] |
280 | Align virtual addresses by clearing slice [14:12] when | |
281 | allocating a VMA at process creation time. This option | |
282 | gives you up to 3% performance improvement on AMD F15h | |
283 | machines (where it is enabled by default) for a | |
284 | CPU-intensive style benchmark, and it can vary highly in | |
285 | a microbenchmark depending on workload and compiler. | |
286 | ||
8360ee2f BP |
287 | 32: only for 32-bit processes |
288 | 64: only for 64-bit processes | |
dfb09f9b BP |
289 | on: enable for both 32- and 64-bit processes |
290 | off: disable for both 32- and 64-bit processes | |
291 | ||
55034cd6 SRRH |
292 | alloc_snapshot [FTRACE] |
293 | Allocate the ftrace snapshot buffer on boot up when the | |
294 | main buffer is allocated. This is handy if debugging | |
295 | and you need to use tracing_snapshot() on boot up, and | |
296 | do not want to use tracing_snapshot_alloc() as it needs | |
297 | to be done where GFP_KERNEL allocations are allowed. | |
298 | ||
ead7de46 WD |
299 | allow_mismatched_32bit_el0 [ARM64] |
300 | Allow execve() of 32-bit applications and setting of the | |
301 | PER_LINUX32 personality on systems where only a strict | |
302 | subset of the CPUs support 32-bit EL0. When this | |
303 | parameter is present, the set of CPUs supporting 32-bit | |
304 | EL0 is indicated by /sys/devices/system/cpu/aarch32_el0 | |
305 | and hot-unplug operations may be restricted. | |
306 | ||
702f4387 WD |
307 | See Documentation/arm64/asymmetric-32bit.rst for more |
308 | information. | |
309 | ||
89e0b9a3 | 310 | amd_iommu= [HW,X86-64] |
54b4cbd2 JR |
311 | Pass parameters to the AMD IOMMU driver in the system. |
312 | Possible values are: | |
1d479f16 | 313 | fullflush - Deprecated, equivalent to iommu.strict=1 |
a5235725 JR |
314 | off - do not initialize any AMD IOMMU found in |
315 | the system | |
5abcdba4 JR |
316 | force_isolation - Force device isolation for all |
317 | devices. The IOMMU driver is not | |
318 | allowed anymore to lift isolation | |
319 | requirements as needed. This option | |
320 | does not override iommu=pt | |
b1e650db JR |
321 | force_enable - Force enable the IOMMU on platforms known |
322 | to be buggy with IOMMU enabled. Use this | |
323 | option with care. | |
afa9fdc2 | 324 | |
c099cf17 SK |
325 | amd_iommu_dump= [HW,X86-64] |
326 | Enable AMD IOMMU driver option to dump the ACPI table | |
327 | for AMD IOMMU. With this option enabled, AMD IOMMU | |
328 | driver will print ACPI tables for AMD IOMMU during | |
329 | IOMMU initialization. | |
330 | ||
3928aa3f SS |
331 | amd_iommu_intr= [HW,X86-64] |
332 | Specifies one of the following AMD IOMMU interrupt | |
333 | remapping modes: | |
334 | legacy - Use legacy interrupt remapping mode. | |
335 | vapic - Use virtual APIC mode, which allows IOMMU | |
336 | to inject interrupts directly into guest. | |
337 | This mode requires kvm-amd.avic=1. | |
338 | (Default when IOMMU HW support is present.) | |
339 | ||
1da177e4 LT |
340 | amijoy.map= [HW,JOY] Amiga joystick support |
341 | Map of devices attached to JOY0DAT and JOY1DAT | |
342 | Format: <a>,<b> | |
1752118d | 343 | See also Documentation/input/joydev/joystick.rst |
1da177e4 LT |
344 | |
345 | analog.map= [HW,JOY] Analog joystick and gamepad support | |
346 | Specifies type or capabilities of an analog joystick | |
347 | connected to one of 16 gameports | |
348 | Format: <type1>,<type2>,..<type16> | |
349 | ||
a9913044 RD |
350 | apc= [HW,SPARC] |
351 | Power management functions (SPARCstation-4/5 + deriv.) | |
1da177e4 LT |
352 | Format: noidle |
353 | Disable APC CPU standby support. SPARCstation-Fox does | |
354 | not play well with APC CPU idle - disable it if you have | |
355 | APC and your system crashes randomly. | |
356 | ||
64e05d11 | 357 | apic= [APIC,X86] Advanced Programmable Interrupt Controller |
806654a9 | 358 | Change the output verbosity while booting |
1da177e4 LT |
359 | Format: { quiet (default) | verbose | debug } |
360 | Change the amount of debugging information output | |
361 | when initialising the APIC and IO-APIC components. | |
64e05d11 DL |
362 | For X86-32, this can also be used to specify an APIC |
363 | driver name. | |
364 | Format: apic=driver_name | |
365 | Examples: apic=bigsmp | |
a9913044 | 366 | |
b7c4948e HK |
367 | apic_extnmi= [APIC,X86] External NMI delivery setting |
368 | Format: { bsp (default) | all | none } | |
369 | bsp: External NMI is delivered only to CPU 0 | |
370 | all: External NMIs are broadcast to all CPUs as a | |
371 | backup of CPU 0 | |
372 | none: External NMI is masked for all CPUs. This is | |
373 | useful so that a dump capture kernel won't be | |
374 | shot down by NMI | |
375 | ||
b0f83b28 | 376 | autoconf= [IPV6] |
19093313 | 377 | See Documentation/networking/ipv6.rst. |
b0f83b28 | 378 | |
9636bc05 CG |
379 | show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller |
380 | Limit apic dumping. The parameter defines the maximal | |
381 | number of local apics being dumped. Also it is possible | |
382 | to set it to "all" by meaning -- no limit here. | |
383 | Format: { 1 (default) | 2 | ... | all }. | |
384 | The parameter valid if only apic=debug or | |
385 | apic=verbose is specified. | |
386 | Example: apic=debug show_lapic=all | |
387 | ||
1da177e4 | 388 | apm= [APM] Advanced Power Management |
71f77055 | 389 | See header of arch/x86/kernel/apm_32.c. |
1da177e4 | 390 | |
1da177e4 LT |
391 | arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards |
392 | Format: <io>,<irq>,<nodeID> | |
393 | ||
93ad55b7 MZ |
394 | arm64.nobti [ARM64] Unconditionally disable Branch Target |
395 | Identification support | |
396 | ||
f8da5752 MZ |
397 | arm64.nopauth [ARM64] Unconditionally disable Pointer Authentication |
398 | support | |
399 | ||
7a062ce3 YL |
400 | arm64.nomte [ARM64] Unconditionally disable Memory Tagging Extension |
401 | support | |
402 | ||
504ee236 MZ |
403 | arm64.nosve [ARM64] Unconditionally disable Scalable Vector |
404 | Extension support | |
405 | ||
b3000e21 MZ |
406 | arm64.nosme [ARM64] Unconditionally disable Scalable Matrix |
407 | Extension support | |
408 | ||
1da177e4 LT |
409 | ataflop= [HW,M68k] |
410 | ||
411 | atarimouse= [HW,MOUSE] Atari Mouse | |
412 | ||
1da177e4 LT |
413 | atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess, |
414 | EzKey and similar keyboards | |
415 | ||
416 | atkbd.reset= [HW] Reset keyboard during initialization | |
417 | ||
a9913044 RD |
418 | atkbd.set= [HW] Select keyboard code set |
419 | Format: <int> (2 = AT (default), 3 = PS/2) | |
1da177e4 LT |
420 | |
421 | atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar | |
422 | keyboards | |
423 | ||
424 | atkbd.softraw= [HW] Choose between synthetic and real raw mode | |
425 | Format: <bool> (0 = real, 1 = synthetic (default)) | |
a9913044 RD |
426 | |
427 | atkbd.softrepeat= [HW] | |
428 | Use software keyboard repeat | |
1da177e4 | 429 | |
a106fb0c | 430 | audit= [KNL] Enable the audit sub-system |
11dd2666 GE |
431 | Format: { "0" | "1" | "off" | "on" } |
432 | 0 | off - kernel audit is disabled and can not be | |
433 | enabled until the next reboot | |
d7961148 EP |
434 | unset - kernel audit is initialized but disabled and |
435 | will be fully enabled by the userspace auditd. | |
11dd2666 GE |
436 | 1 | on - kernel audit is initialized and partially |
437 | enabled, storing at most audit_backlog_limit | |
438 | messages in RAM until it is fully enabled by the | |
439 | userspace auditd. | |
a106fb0c | 440 | Default: unset |
f3411cb2 | 441 | |
f910fde7 RGB |
442 | audit_backlog_limit= [KNL] Set the audit queue size limit. |
443 | Format: <int> (must be >=0) | |
444 | Default: 64 | |
445 | ||
1c532e00 AT |
446 | bau= [X86_UV] Enable the BAU on SGI UV. The default |
447 | behavior is to disable the BAU (i.e. bau=0). | |
448 | Format: { "0" | "1" } | |
449 | 0 - Disable the BAU. | |
450 | 1 - Enable the BAU. | |
451 | unset - Disable the BAU. | |
452 | ||
1da177e4 LT |
453 | baycom_epp= [HW,AX25] |
454 | Format: <io>,<mode> | |
a9913044 | 455 | |
1da177e4 LT |
456 | baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem |
457 | Format: <io>,<mode> | |
458 | See header of drivers/net/hamradio/baycom_par.c. | |
459 | ||
a9913044 RD |
460 | baycom_ser_fdx= [HW,AX25] |
461 | BayCom Serial Port AX.25 Modem (Full Duplex Mode) | |
1da177e4 LT |
462 | Format: <io>,<irq>,<mode>[,<baud>] |
463 | See header of drivers/net/hamradio/baycom_ser_fdx.c. | |
464 | ||
a9913044 RD |
465 | baycom_ser_hdx= [HW,AX25] |
466 | BayCom Serial Port AX.25 Modem (Half Duplex Mode) | |
1da177e4 LT |
467 | Format: <io>,<irq>,<mode> |
468 | See header of drivers/net/hamradio/baycom_ser_hdx.c. | |
469 | ||
389cfd96 RD |
470 | bert_disable [ACPI] |
471 | Disable BERT OS support on buggy BIOSes. | |
472 | ||
473 | bgrt_disable [ACPI][X86] | |
474 | Disable BGRT to avoid flickering OEM logo. | |
475 | ||
080506ad PG |
476 | blkdevparts= Manual partition parsing of block device(s) for |
477 | embedded devices based on command line input. | |
898bd37a | 478 | See Documentation/block/cmdline-partition.rst |
080506ad | 479 | |
bfe8df3d RD |
480 | boot_delay= Milliseconds to delay each printk during boot. |
481 | Values larger than 10 seconds (10000) are changed to | |
482 | no delay (0). | |
483 | Format: integer | |
484 | ||
7495e092 SRV |
485 | bootconfig [KNL] |
486 | Extended command line options can be added to an initrd | |
487 | and this will cause the kernel to look for it. | |
488 | ||
489 | See Documentation/admin-guide/bootconfig.rst | |
490 | ||
1da177e4 | 491 | bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards) |
a9913044 RD |
492 | bttv.radio= Most important insmod options are available as |
493 | kernel args too. | |
32e2eae2 | 494 | bttv.pll= See Documentation/admin-guide/media/bttv.rst |
395cf969 | 495 | bttv.tuner= |
1da177e4 | 496 | |
4e89a2d8 WS |
497 | bulk_remove=off [PPC] This parameter disables the use of the pSeries |
498 | firmware feature for flushing multiple hpte entries | |
499 | at a time. | |
500 | ||
1da177e4 LT |
501 | c101= [NET] Moxa C101 synchronous serial card |
502 | ||
cd4f0ef7 | 503 | cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection. |
1da177e4 LT |
504 | Sometimes CPU hardware bugs make them report the cache |
505 | size incorrectly. The kernel will attempt work arounds | |
506 | to fix known problems, but for some CPUs it is not | |
507 | possible to determine what the correct size should be. | |
508 | This option provides an override for these situations. | |
509 | ||
3fc46fc9 MK |
510 | carrier_timeout= |
511 | [NET] Specifies amount of time (in seconds) that | |
512 | the kernel should wait for a network carrier. By default | |
513 | it waits 120 seconds. | |
514 | ||
ffb70f61 DK |
515 | ca_keys= [KEYS] This parameter identifies a specific key(s) on |
516 | the system trusted keyring to be used for certificate | |
517 | trust validation. | |
32c4741c | 518 | format: { id:<keyid> | builtin } |
ffb70f61 | 519 | |
fd1bb4c9 FF |
520 | cca= [MIPS] Override the kernel pages' cache coherency |
521 | algorithm. Accepted values range from 0 to 7 | |
522 | inclusive. See arch/mips/include/asm/pgtable-bits.h | |
523 | for platform specific values (SB1, Loongson3 and | |
524 | others). | |
525 | ||
6dddd7a7 | 526 | ccw_timeout_log [S390] |
8b4a503d | 527 | See Documentation/s390/common_io.rst for details. |
1da177e4 | 528 | |
3958e2d0 SB |
529 | cgroup_disable= [KNL] Disable a particular controller or optional feature |
530 | Format: {name of the controller(s) or feature(s) to disable} | |
ca0bdbb5 QH |
531 | The effects of cgroup_disable=foo are: |
532 | - foo isn't auto-mounted if you mount all cgroups in | |
533 | a single hierarchy | |
534 | - foo isn't visible as an individually mountable | |
535 | subsystem | |
3958e2d0 SB |
536 | - if foo is an optional feature then the feature is |
537 | disabled and corresponding cgroup files are not | |
538 | created | |
ca0bdbb5 QH |
539 | {Currently only "memory" controller deal with this and |
540 | cut the overhead, others just disable the usage. So | |
541 | only cgroup_disable=memory is actually worthy} | |
3958e2d0 SB |
542 | Specifying "pressure" disables per-cgroup pressure |
543 | stall information accounting feature | |
8bab8dde | 544 | |
3fc9c12d TH |
545 | cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1 |
546 | Format: { { controller | "all" | "named" } | |
547 | [,{ controller | "all" | "named" }...] } | |
1619b6d4 JW |
548 | Like cgroup_disable, but only applies to cgroup v1; |
549 | the blacklisted controllers remain available in cgroup2. | |
3fc9c12d TH |
550 | "all" blacklists all controllers and "named" disables |
551 | named mounts. Specifying both "all" and "named" disables | |
552 | all v1 hierarchies. | |
1619b6d4 | 553 | |
f7e1cb6e JW |
554 | cgroup.memory= [KNL] Pass options to the cgroup memory controller. |
555 | Format: <string> | |
556 | nosocket -- Disable socket memory accounting. | |
04823c83 | 557 | nokmem -- Disable kernel memory accounting. |
f7e1cb6e | 558 | |
8d6d51ed | 559 | checkreqprot= [SELINUX] Set initial checkreqprot flag value. |
1da177e4 LT |
560 | Format: { "0" | "1" } |
561 | See security/selinux/Kconfig help text. | |
a9913044 RD |
562 | 0 -- check protection applied by kernel (includes |
563 | any implied execute protection). | |
1da177e4 LT |
564 | 1 -- check protection requested by application. |
565 | Default value is set via a kernel config option. | |
a9913044 | 566 | Value can be changed at runtime via |
d41415eb | 567 | /sys/fs/selinux/checkreqprot. |
e9c38f9f | 568 | Setting checkreqprot to 1 is deprecated. |
a9913044 | 569 | |
661ca0da | 570 | cio_ignore= [S390] |
8b4a503d | 571 | See Documentation/s390/common_io.rst for details. |
d2fc83c1 | 572 | |
88a61892 | 573 | clearcpuid=X[,X...] [X86] |
d2fc83c1 RD |
574 | Disable CPUID feature X for the kernel. See |
575 | arch/x86/include/asm/cpufeatures.h for the valid bit | |
88a61892 LT |
576 | numbers X. Note the Linux-specific bits are not necessarily |
577 | stable over kernel options, but the vendor-specific | |
d2fc83c1 | 578 | ones should be. |
88a61892 LT |
579 | X can also be a string as appearing in the flags: line |
580 | in /proc/cpuinfo which does not have the above | |
581 | instability issue. However, not all features have names | |
582 | in /proc/cpuinfo. | |
583 | Note that using this option will taint your kernel. | |
d2fc83c1 RD |
584 | Also note that user programs calling CPUID directly |
585 | or using the feature without checking anything | |
586 | will still see it. This just prevents it from | |
587 | being used by the kernel or shown in /proc/cpuinfo. | |
588 | Also note the kernel might malfunction if you disable | |
589 | some critical bits. | |
590 | ||
1e435256 OJ |
591 | clk_ignore_unused |
592 | [CLK] | |
e156ee56 MT |
593 | Prevents the clock framework from automatically gating |
594 | clocks that have not been explicitly enabled by a Linux | |
595 | device driver but are enabled in hardware at reset or | |
596 | by the bootloader/firmware. Note that this does not | |
597 | force such clocks to be always-on nor does it reserve | |
598 | those clocks in any way. This parameter is useful for | |
599 | debug and development, but should not be needed on a | |
600 | platform with proper driver support. For more | |
18bcaa4e | 601 | information, see Documentation/driver-api/clk.rst. |
661ca0da | 602 | |
cd4f0ef7 | 603 | clock= [BUGS=X86-32, HW] gettimeofday clocksource override. |
734efb46 | 604 | [Deprecated] |
3f6dee9b | 605 | Forces specified clocksource (if available) to be used |
734efb46 | 606 | when calculating gettimeofday(). If specified |
3f6dee9b | 607 | clocksource is not available, it defaults to PIT. |
1da177e4 LT |
608 | Format: { pit | tsc | cyclone | pmtmr } |
609 | ||
592913ec | 610 | clocksource= Override the default clocksource |
3d6ac984 RD |
611 | Format: <string> |
612 | Override the default clocksource and use the clocksource | |
613 | with the name specified. | |
614 | Some clocksource names to choose from, depending on | |
615 | the platform: | |
616 | [all] jiffies (this is the base, fallback clocksource) | |
617 | [ACPI] acpi_pm | |
618 | [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2, | |
619 | pxa_timer,timer3,32k_counter,timer0_1 | |
9863c90f | 620 | [X86-32] pit,hpet,tsc; |
3d6ac984 RD |
621 | scx200_hrt on Geode; cyclone on IBM x440 |
622 | [MIPS] MIPS | |
623 | [PARISC] cr16 | |
624 | [S390] tod | |
625 | [SH] SuperH | |
626 | [SPARC64] tick | |
627 | [X86-64] hpet,tsc | |
628 | ||
46fd5c6b WD |
629 | clocksource.arm_arch_timer.evtstrm= |
630 | [ARM,ARM64] | |
631 | Format: <bool> | |
632 | Enable/disable the eventstream feature of the ARM | |
633 | architected timer so that code using WFE-based polling | |
634 | loops can be debugged more effectively on production | |
635 | systems. | |
636 | ||
db3a34e1 PM |
637 | clocksource.max_cswd_read_retries= [KNL] |
638 | Number of clocksource_watchdog() retries due to | |
639 | external delays before the clock will be marked | |
1a562067 WL |
640 | unstable. Defaults to two retries, that is, |
641 | three attempts to read the clock under test. | |
db3a34e1 | 642 | |
fa218f1c PM |
643 | clocksource.verify_n_cpus= [KNL] |
644 | Limit the number of CPUs checked for clocksources | |
645 | marked with CLOCK_SOURCE_VERIFY_PERCPU that | |
646 | are marked unstable due to excessive skew. | |
647 | A negative value says to check all CPUs, while | |
648 | zero says not to check any. Values larger than | |
649 | nr_cpu_ids are silently truncated to nr_cpu_ids. | |
650 | The actual CPUs are chosen randomly, with | |
651 | no replacement if the same CPU is chosen twice. | |
652 | ||
1253b9b8 PM |
653 | clocksource-wdtest.holdoff= [KNL] |
654 | Set the time in seconds that the clocksource | |
655 | watchdog test waits before commencing its tests. | |
656 | Defaults to zero when built as a module and to | |
657 | 10 seconds when built into the kernel. | |
658 | ||
5ea3b1b2 | 659 | cma=nn[MG]@[start[MG][-end[MG]]] |
c372e741 | 660 | [KNL,CMA] |
5ea3b1b2 AM |
661 | Sets the size of kernel global memory area for |
662 | contiguous memory allocations and optionally the | |
663 | placement constraint by the physical address range of | |
f0d6d1f6 JD |
664 | memory allocations. A value of 0 disables CMA |
665 | altogether. For more information, see | |
0b1abd1f | 666 | kernel/dma/contiguous.c |
c64be2bb | 667 | |
b7176c26 | 668 | cma_pernuma=nn[MG] |
bc47190d | 669 | [ARM64,KNL,CMA] |
b7176c26 BS |
670 | Sets the size of kernel per-numa memory area for |
671 | contiguous memory allocations. A value of 0 disables | |
672 | per-numa CMA altogether. And If this option is not | |
673 | specificed, the default value is 0. | |
674 | With per-numa CMA enabled, DMA users on node nid will | |
675 | first try to allocate buffer from the pernuma area | |
676 | which is located in node nid, if the allocation fails, | |
677 | they will fallback to the global default memory area. | |
c64be2bb | 678 | |
14f966e7 RJ |
679 | cmo_free_hint= [PPC] Format: { yes | no } |
680 | Specify whether pages are marked as being inactive | |
681 | when they are freed. This is used in CMO environments | |
682 | to determine OS memory pressure for page stealing by | |
683 | a hypervisor. | |
684 | Default: yes | |
685 | ||
c7909509 MS |
686 | coherent_pool=nn[KMG] [ARM,KNL] |
687 | Sets the size of memory pool for coherent, atomic dma | |
e9da6e99 | 688 | allocations, by default set to 256K. |
c7909509 | 689 | |
1da177e4 | 690 | com20020= [HW,NET] ARCnet - COM20020 chipset |
a9913044 RD |
691 | Format: |
692 | <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]] | |
1da177e4 LT |
693 | |
694 | com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers) | |
695 | Format: <io>[,<irq>] | |
696 | ||
a9913044 RD |
697 | com90xx= [HW,NET] |
698 | ARCnet - COM90xx chipset (memory-mapped buffers) | |
1da177e4 LT |
699 | Format: <io>[,<irq>[,<memstart>]] |
700 | ||
701 | condev= [HW,S390] console device | |
702 | conmode= | |
a9913044 | 703 | |
1da177e4 LT |
704 | console= [KNL] Output console device and options. |
705 | ||
706 | tty<n> Use the virtual console device <n>. | |
707 | ||
708 | ttyS<n>[,options] | |
f1a1c2dc | 709 | ttyUSB0[,options] |
1da177e4 | 710 | Use the specified serial port. The options are of |
f1a1c2dc RD |
711 | the form "bbbbpnf", where "bbbb" is the baud rate, |
712 | "p" is parity ("n", "o", or "e"), "n" is number of | |
713 | bits, and "f" is flow control ("r" for RTS or | |
714 | omit it). Default is "9600n8". | |
715 | ||
e52347bd | 716 | See Documentation/admin-guide/serial-console.rst for more |
f1a1c2dc | 717 | information. See |
d9d6ef25 | 718 | Documentation/networking/netconsole.rst for an |
f1a1c2dc | 719 | alternative. |
1da177e4 | 720 | |
18a8bd94 YL |
721 | uart[8250],io,<addr>[,options] |
722 | uart[8250],mmio,<addr>[,options] | |
bd94c407 | 723 | uart[8250],mmio16,<addr>[,options] |
ca782f16 PH |
724 | uart[8250],mmio32,<addr>[,options] |
725 | uart[8250],0x<addr>[,options] | |
1da177e4 LT |
726 | Start an early, polled-mode console on the 8250/16550 |
727 | UART at the specified I/O port or MMIO address, | |
ca782f16 PH |
728 | switching to the matching ttyS device later. |
729 | MMIO inter-register address stride is either 8-bit | |
bd94c407 MY |
730 | (mmio), 16-bit (mmio16), or 32-bit (mmio32). |
731 | If none of [io|mmio|mmio16|mmio32], <addr> is assumed | |
732 | to be equivalent to 'mmio'. 'options' are specified in | |
733 | the same format described for ttyS above; if unspecified, | |
ca782f16 PH |
734 | the h/w is not re-initialized. |
735 | ||
a2fd6419 KRW |
736 | hvc<n> Use the hypervisor console device <n>. This is for |
737 | both Xen and PowerPC hypervisors. | |
1da177e4 | 738 | |
96b02f2f RD |
739 | { null | "" } |
740 | Use to disable console output, i.e., to have kernel | |
741 | console messages discarded. | |
742 | This must be the only console= parameter used on the | |
743 | kernel command line. | |
744 | ||
6dddd7a7 TB |
745 | If the device connected to the port is not a TTY but a braille |
746 | device, prepend "brl," before the device type, for instance | |
f7511d5f ST |
747 | console=brl,ttyS0 |
748 | For now, only VisioBraille is supported. | |
749 | ||
cca10d58 SS |
750 | console_msg_format= |
751 | [KNL] Change console messages format | |
752 | default | |
753 | By default we print messages on consoles in | |
754 | "[time stamp] text\n" format (time stamp may not be | |
755 | printed, depending on CONFIG_PRINTK_TIME or | |
756 | `printk_time' param). | |
757 | syslog | |
758 | Switch to syslog format: "<%u>[time stamp] text\n" | |
759 | IOW, each message will have a facility and loglevel | |
760 | prefix. The format is similar to one used by syslog() | |
761 | syscall, or to executing "dmesg -S --raw" or to reading | |
762 | from /proc/kmsg. | |
763 | ||
f324edc8 | 764 | consoleblank= [KNL] The console blank (screen saver) timeout in |
ac0a314c | 765 | seconds. A value of 0 disables the blank timer. |
6dddd7a7 | 766 | Defaults to 0. |
f324edc8 | 767 | |
4cb0e11b HK |
768 | coredump_filter= |
769 | [KNL] Change the default value for | |
770 | /proc/<pid>/coredump_filter. | |
cd4ca341 | 771 | See also Documentation/filesystems/proc.rst. |
4cb0e11b | 772 | |
62a31ce1 LY |
773 | coresight_cpu_debug.enable |
774 | [ARM,ARM64] | |
775 | Format: <bool> | |
776 | Enable/disable the CPU sampling based debugging. | |
777 | 0: default value, disable debugging | |
778 | 1: enable debugging at boot time | |
779 | ||
389cfd96 RD |
780 | cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver |
781 | Format: | |
782 | <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>] | |
783 | ||
784 | cpu0_hotplug [X86] Turn on CPU0 hotplug feature when | |
785 | CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off. | |
786 | Some features depend on CPU0. Known dependencies are: | |
787 | 1. Resume from suspend/hibernate depends on CPU0. | |
788 | Suspend/hibernate will fail if CPU0 is offline and you | |
789 | need to online CPU0 before suspend/hibernate. | |
790 | 2. PIC interrupts also depend on CPU0. CPU0 can't be | |
791 | removed if a PIC interrupt is detected. | |
792 | It's said poweroff/reboot may depend on CPU0 on some | |
793 | machines although I haven't seen such issues so far | |
794 | after CPU0 is offline on a few tested machines. | |
795 | If the dependencies are under your control, you can | |
796 | turn on cpu0_hotplug. | |
797 | ||
62027aea LB |
798 | cpuidle.off=1 [CPU_IDLE] |
799 | disable the cpuidle sub-system | |
800 | ||
61cb5758 RW |
801 | cpuidle.governor= |
802 | [CPU_IDLE] Name of the cpuidle governor to use. | |
803 | ||
d82f2692 LB |
804 | cpufreq.off=1 [CPU_FREQ] |
805 | disable the cpufreq sub-system | |
806 | ||
8412b456 QP |
807 | cpufreq.default_governor= |
808 | [CPU_FREQ] Name of the default cpufreq governor or | |
809 | policy to use. This governor must be registered in the | |
810 | kernel before the cpufreq driver probes. | |
811 | ||
d68921f9 LB |
812 | cpu_init_udelay=N |
813 | [X86] Delay for N microsec between assert and de-assert | |
814 | of APIC INIT to start processors. This delay occurs | |
815 | on every CPU online, such as boot, and resume from suspend. | |
816 | Default: 10000 | |
817 | ||
389cfd96 RD |
818 | crash_kexec_post_notifiers |
819 | Run kdump after running panic-notifiers and dumping | |
820 | kmsg. This only for the users who doubt kdump always | |
821 | succeeds in any situation. | |
822 | Note that this also increases risks of kdump failure, | |
823 | because some panic notifiers can make the crashed | |
824 | kernel more unstable. | |
1da177e4 | 825 | |
6f21e646 AD |
826 | crashkernel=size[KMG][@offset[KMG]] |
827 | [KNL] Using kexec, Linux can switch to a 'crash kernel' | |
828 | upon panic. This parameter reserves the physical | |
829 | memory region [offset, offset + size] for that kernel | |
830 | image. If '@offset' is omitted, then a suitable offset | |
b9ac3849 | 831 | is selected automatically. |
be3a5b0e | 832 | [KNL, X86-64] Select a region under 4G first, and |
b9ac3849 DY |
833 | fall back to reserve region above 4G when '@offset' |
834 | hasn't been specified. | |
330d4810 | 835 | See Documentation/admin-guide/kdump/kdump.rst for further details. |
dc009d92 | 836 | |
fb391599 BW |
837 | crashkernel=range1:size1[,range2:size2,...][@offset] |
838 | [KNL] Same as above, but depends on the memory | |
839 | in the running system. The syntax of range is | |
840 | start-[end] where start and end are both | |
841 | a memory unit (amount[KMG]). See also | |
330d4810 | 842 | Documentation/admin-guide/kdump/kdump.rst for an example. |
fb391599 | 843 | |
adbc742b | 844 | crashkernel=size[KMG],high |
5832f1ae | 845 | [KNL, X86-64, ARM64] range could be above 4G. Allow kernel |
55a20ee7 YL |
846 | to allocate physical memory region from top, so could |
847 | be above 4G if system have more than 4G ram installed. | |
848 | Otherwise memory region will be allocated below 4G, if | |
849 | available. | |
850 | It will be ignored if crashkernel=X is specified. | |
adbc742b | 851 | crashkernel=size[KMG],low |
be3a5b0e | 852 | [KNL, X86-64] range under 4G. When crashkernel=X,high |
adbc742b | 853 | is passed, kernel could allocate physical memory region |
c729de8f YL |
854 | above 4G, that cause second kernel crash on system |
855 | that require some amount of low memory, e.g. swiotlb | |
c6045031 BH |
856 | requires at least 64M+32K low memory, also enough extra |
857 | low memory is needed to make sure DMA buffers for 32-bit | |
5832f1ae | 858 | devices won't run out. Kernel would try to allocate |
c6045031 | 859 | at least 256M below 4G automatically. |
8f0f104e | 860 | This one lets the user specify own low range under 4G |
c729de8f YL |
861 | for second kernel instead. |
862 | 0: to disable low allocation. | |
adbc742b | 863 | It will be ignored when crashkernel=X,high is not used |
55a20ee7 | 864 | or memory reserved is below 4G. |
c729de8f | 865 | |
5832f1ae ZL |
866 | [KNL, ARM64] range in low memory. |
867 | This one lets the user specify a low range in the | |
868 | DMA zone for the crash dump kernel. | |
8f0f104e ZL |
869 | It will be ignored when crashkernel=X,high is not used |
870 | or memory reserved is located in the DMA zones. | |
5832f1ae | 871 | |
9e5c9fe4 | 872 | cryptomgr.notests |
6dddd7a7 | 873 | [KNL] Disable crypto self-tests |
9e5c9fe4 | 874 | |
1da177e4 LT |
875 | cs89x0_dma= [HW,NET] |
876 | Format: <dma> | |
877 | ||
878 | cs89x0_media= [HW,NET] | |
879 | Format: { rj45 | aui | bnc } | |
a9913044 | 880 | |
8d0968cc JG |
881 | csdlock_debug= [KNL] Enable debug add-ons of cross-CPU function call |
882 | handling. When switched on, additional debug data is | |
883 | printed to the console in case a hanging CPU is | |
884 | detected, and that CPU is pinged again in order to try | |
885 | to resolve the hang situation. | |
a5aabace JG |
886 | 0: disable csdlock debugging (default) |
887 | 1: enable basic csdlock debugging (minor impact) | |
888 | ext: enable extended csdlock debugging (more impact, | |
889 | but more data) | |
8d0968cc | 890 | |
a9913044 | 891 | dasd= [HW,NET] |
1da177e4 LT |
892 | See header of drivers/s390/block/dasd_devmap.c. |
893 | ||
894 | db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port | |
895 | (one device per port) | |
896 | Format: <port#>,<type> | |
1752118d | 897 | See also Documentation/input/devices/joystick-parport.rst |
1da177e4 LT |
898 | |
899 | debug [KNL] Enable kernel debugging (events log level). | |
900 | ||
3672476e TH |
901 | debug_boot_weak_hash |
902 | [KNL] Enable printing [hashed] pointers early in the | |
903 | boot sequence. If enabled, we use a weak hash instead | |
904 | of siphash to hash pointers. Use this option if you are | |
905 | seeing instances of '(___ptrval___)') and need to see a | |
906 | value (hashed pointer) instead. Cryptographically | |
907 | insecure, please do not use on production kernels. | |
908 | ||
cae2ed9a | 909 | debug_locks_verbose= |
5831c0f7 PZ |
910 | [KNL] verbose locking self-tests |
911 | Format: <int> | |
cae2ed9a IM |
912 | Print debugging info while doing the locking API |
913 | self-tests. | |
5831c0f7 PZ |
914 | Bitmask for the various LOCKTYPE_ tests. Defaults to 0 |
915 | (no extra messages), setting it to -1 (all bits set) | |
916 | will print _a_lot_ more information - normally only | |
917 | useful to lockdep developers. | |
cae2ed9a | 918 | |
3ac7fe5a TG |
919 | debug_objects [KNL] Enable object debugging |
920 | ||
3e8ebb5c KM |
921 | no_debug_objects |
922 | [KNL] Disable object debugging | |
923 | ||
c0a32fc5 SG |
924 | debug_guardpage_minorder= |
925 | [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this | |
926 | parameter allows control of the order of pages that will | |
927 | be intentionally kept free (and hence protected) by the | |
928 | buddy allocator. Bigger value increase the probability | |
929 | of catching random memory corruption, but reduce the | |
930 | amount of memory for normal system use. The maximum | |
931 | possible value is MAX_ORDER/2. Setting this parameter | |
932 | to 1 or 2 should be enough to identify most random | |
933 | memory corruption problems caused by bugs in kernel or | |
934 | driver code when a CPU writes to (or reads from) a | |
935 | random memory location. Note that there exists a class | |
936 | of memory corruptions problems caused by buggy H/W or | |
937 | F/W or by drivers badly programing DMA (basically when | |
938 | memory is written at bus level and the CPU MMU is | |
939 | bypassed) which are not detectable by | |
940 | CONFIG_DEBUG_PAGEALLOC, hence this option will not help | |
941 | tracking down these problems. | |
942 | ||
031bc574 | 943 | debug_pagealloc= |
3972f6bb VB |
944 | [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this parameter |
945 | enables the feature at boot time. By default, it is | |
946 | disabled and the system will work mostly the same as a | |
947 | kernel built without CONFIG_DEBUG_PAGEALLOC. | |
8974558f VB |
948 | Note: to get most of debug_pagealloc error reports, it's |
949 | useful to also enable the page_owner functionality. | |
031bc574 JK |
950 | on: enable the feature |
951 | ||
a24c6f7b PE |
952 | debugfs= [KNL] This parameter enables what is exposed to userspace |
953 | and debugfs internal clients. | |
954 | Format: { on, no-mount, off } | |
955 | on: All functions are enabled. | |
956 | no-mount: | |
957 | Filesystem is not registered but kernel clients can | |
958 | access APIs and a crashkernel can be used to read | |
959 | its content. There is nothing to mount. | |
960 | off: Filesystem is not registered and clients | |
961 | get a -EPERM as result when trying to register files | |
962 | or directories within debugfs. | |
963 | This is equivalent of the runtime functionality if | |
964 | debugfs was not enabled in the kernel at all. | |
965 | Default value is set in build-time with a kernel configuration. | |
966 | ||
d3af01f1 TG |
967 | debugpat [X86] Enable PAT debugging |
968 | ||
2d27a966 | 969 | decnet.addr= [HW,NET] |
1da177e4 | 970 | Format: <area>[,<node>] |
9a69fb9c | 971 | See also Documentation/networking/decnet.rst. |
1da177e4 | 972 | |
0cb55ad2 | 973 | default_hugepagesz= |
282f4214 MK |
974 | [HW] The size of the default HugeTLB page. This is |
975 | the size represented by the legacy /proc/ hugepages | |
976 | APIs. In addition, this is the default hugetlb size | |
977 | used for shmget(), mmap() and mounting hugetlbfs | |
978 | filesystems. If not specified, defaults to the | |
979 | architecture's default huge page size. Huge page | |
980 | sizes are architecture dependent. See also | |
981 | Documentation/admin-guide/mm/hugetlbpage.rst. | |
982 | Format: size[KMG] | |
55ff9780 | 983 | |
25b4e70d RH |
984 | deferred_probe_timeout= |
985 | [KNL] Debugging option to set a timeout in seconds for | |
986 | deferred probe to give up waiting on dependencies to | |
987 | probe. Only specific dependencies (subsystems or | |
2b28a1a8 SK |
988 | drivers) that have opted in will be ignored. A timeout |
989 | of 0 will timeout at the end of initcalls. If the time | |
990 | out hasn't expired, it'll be restarted by each | |
991 | successful driver registration. This option will also | |
25b4e70d RH |
992 | dump out devices still on the deferred probe list after |
993 | retrying. | |
994 | ||
d2fc83c1 RD |
995 | delayacct [KNL] Enable per-task delay accounting |
996 | ||
1b089084 AW |
997 | dell_smm_hwmon.ignore_dmi= |
998 | [HW] Continue probing hardware even if DMI data | |
999 | indicates that the driver is running on unsupported | |
1000 | hardware. | |
1001 | ||
1002 | dell_smm_hwmon.force= | |
1003 | [HW] Activate driver even if SMM BIOS signature does | |
1004 | not match list of supported models and enable otherwise | |
1005 | blacklisted features. | |
1006 | ||
1007 | dell_smm_hwmon.power_status= | |
1008 | [HW] Report power status in /proc/i8k | |
1009 | (disabled by default). | |
1010 | ||
1011 | dell_smm_hwmon.restricted= | |
1012 | [HW] Allow controlling fans only if SYS_ADMIN | |
1013 | capability is set. | |
1014 | ||
99fdc587 AW |
1015 | dell_smm_hwmon.fan_mult= |
1016 | [HW] Factor to multiply fan speed with. | |
1017 | ||
1018 | dell_smm_hwmon.fan_max= | |
1019 | [HW] Maximum configurable fan speed. | |
1020 | ||
c65e6815 MZ |
1021 | dfltcc= [HW,S390] |
1022 | Format: { on | off | def_only | inf_only | always } | |
1023 | on: s390 zlib hardware support for compression on | |
1024 | level 1 and decompression (default) | |
1025 | off: No s390 zlib hardware support | |
1026 | def_only: s390 zlib hardware support for deflate | |
1027 | only (compression on level 1) | |
1028 | inf_only: s390 zlib hardware support for inflate | |
1029 | only (decompression) | |
1030 | always: Same as 'on' but ignores the selected compression | |
1031 | level always using hardware support (used for debugging) | |
1032 | ||
1da177e4 LT |
1033 | dhash_entries= [KNL] |
1034 | Set number of hash buckets for dentry cache. | |
a9913044 | 1035 | |
faf78829 OH |
1036 | disable_1tb_segments [PPC] |
1037 | Disables the use of 1TB hash page table segments. This | |
1038 | causes the kernel to fall back to 256MB segments which | |
1039 | can be useful when debugging issues that require an SLB | |
1040 | miss to occur. | |
1041 | ||
82a1b8ed NP |
1042 | stress_slb [PPC] |
1043 | Limits the number of kernel SLB entries, and flushes | |
1044 | them frequently to increase the rate of SLB faults | |
1045 | on kernel addresses. | |
1046 | ||
b0f83b28 | 1047 | disable= [IPV6] |
19093313 | 1048 | See Documentation/networking/ipv6.rst. |
b0f83b28 | 1049 | |
b275bfb2 AK |
1050 | disable_radix [PPC] |
1051 | Disable RADIX MMU mode on POWER9 | |
1052 | ||
bf6b7661 AK |
1053 | radix_hcall_invalidate=on [PPC/PSERIES] |
1054 | Disable RADIX GTSE feature and use hcall for TLB | |
1055 | invalidate. | |
1056 | ||
2275d7b5 NP |
1057 | disable_tlbie [PPC] |
1058 | Disable TLBIE instruction. Currently does not work | |
1059 | with KVM, with HASH MMU, or with coherent accelerators. | |
1060 | ||
151e0c7d HD |
1061 | disable_cpu_apicid= [X86,APIC,SMP] |
1062 | Format: <int> | |
1063 | The number of initial APIC ID for the | |
1064 | corresponding CPU to be disabled at boot, | |
1065 | mostly used for the kdump 2nd kernel to | |
1066 | disable BSP to wake up multiple CPUs without | |
1067 | causing system reset or hang due to sending | |
1068 | INIT from AP to BSP. | |
1069 | ||
6dddd7a7 | 1070 | disable_ddw [PPC/PSERIES] |
255bf90f | 1071 | Disable Dynamic DMA Window support. Use this |
4e8b0cf4 NA |
1072 | to workaround buggy firmware. |
1073 | ||
b0f83b28 | 1074 | disable_ipv6= [IPV6] |
19093313 | 1075 | See Documentation/networking/ipv6.rst. |
b0f83b28 | 1076 | |
95ffa243 | 1077 | disable_mtrr_cleanup [X86] |
95ffa243 YL |
1078 | The kernel tries to adjust MTRR layout from continuous |
1079 | to discrete, to make X server driver able to add WB | |
0cb55ad2 | 1080 | entry later. This parameter disables that. |
95ffa243 | 1081 | |
093af8d7 | 1082 | disable_mtrr_trim [X86, Intel and AMD only] |
99fc8d42 JB |
1083 | By default the kernel will trim any uncacheable |
1084 | memory out of your available memory pool based on | |
1085 | MTRR settings. This parameter disables that behavior, | |
1086 | possibly causing your machine to run very slowly. | |
1087 | ||
6cececfc | 1088 | disable_timer_pin_1 [X86] |
0cb55ad2 RD |
1089 | Disable PIN 1 of APIC timer |
1090 | Can be useful to work around chipset bugs. | |
1091 | ||
ce14c583 PB |
1092 | dis_ucode_ldr [X86] Disable the microcode loader. |
1093 | ||
0cb55ad2 RD |
1094 | dma_debug=off If the kernel is compiled with DMA_API_DEBUG support, |
1095 | this option disables the debugging code at boot. | |
1096 | ||
1097 | dma_debug_entries=<number> | |
1098 | This option allows to tune the number of preallocated | |
1099 | entries for DMA-API debugging code. One entry is | |
1100 | required per DMA-API allocation. Use this if the | |
1101 | DMA-API debugging code disables itself because the | |
1102 | architectural default is too low. | |
1103 | ||
1745de5e JR |
1104 | dma_debug_driver=<driver_name> |
1105 | With this option the DMA-API debugging driver | |
1106 | filter feature can be enabled at boot time. Just | |
1107 | pass the driver to filter for as the parameter. | |
1108 | The filter can be disabled or changed to another | |
1109 | driver later using sysfs. | |
1110 | ||
1ea61b68 | 1111 | driver_async_probe= [KNL] |
f79f662e SK |
1112 | List of driver names to be probed asynchronously. * |
1113 | matches with all driver names. If * is specified, the | |
1114 | rest of the listed driver names are those that will NOT | |
1115 | match the *. | |
1ea61b68 FT |
1116 | Format: <driver_name1>,<driver_name2>... |
1117 | ||
53fd40a9 | 1118 | drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>] |
96206e29 BP |
1119 | Broken monitors, graphic adapters, KVMs and EDIDless |
1120 | panels may send no or incorrect EDID data sets. | |
1121 | This parameter allows to specify an EDID data sets | |
1122 | in the /lib/firmware directory that are used instead. | |
da0df92b CE |
1123 | Generic built-in EDID data sets are used, if one of |
1124 | edid/1024x768.bin, edid/1280x1024.bin, | |
1125 | edid/1680x1050.bin, or edid/1920x1080.bin is given | |
1126 | and no file with the same name exists. Details and | |
1127 | instructions how to build your own EDID data are | |
cd4ca341 | 1128 | available in Documentation/admin-guide/edid.rst. An EDID |
da0df92b CE |
1129 | data set will only be used for a particular connector, |
1130 | if its name and a colon are prepended to the EDID | |
96206e29 BP |
1131 | name. Each connector may use a unique EDID data |
1132 | set by separating the files with a comma. An EDID | |
1133 | data set with no connector name will be used for | |
1134 | any connectors not explicitly specified. | |
da0df92b | 1135 | |
1da177e4 LT |
1136 | dscc4.setup= [NET] |
1137 | ||
a2b05b7a NP |
1138 | dt_cpu_ftrs= [PPC] |
1139 | Format: {"off" | "known"} | |
1140 | Control how the dt_cpu_ftrs device-tree binding is | |
1141 | used for CPU feature discovery and setup (if it | |
1142 | exists). | |
1143 | off: Do not use it, fall back to legacy cpu table. | |
1144 | known: Do not pass through unknown features to guests | |
1145 | or userspace, only those that the kernel is aware of. | |
1146 | ||
58c5475a LW |
1147 | dump_apple_properties [X86] |
1148 | Dump name and content of EFI device properties on | |
1149 | x86 Macs. Useful for driver authors to determine | |
1150 | what data is available or for reverse-engineering. | |
1151 | ||
29e36c9f | 1152 | dyndbg[="val"] [KNL,DYNAMIC_DEBUG] |
307e3ee9 | 1153 | <module>.dyndbg[="val"] |
29e36c9f | 1154 | Enable debug messages at boot time. See |
787e3075 SM |
1155 | Documentation/admin-guide/dynamic-debug-howto.rst |
1156 | for details. | |
29e36c9f | 1157 | |
06976945 DH |
1158 | nopku [X86] Disable Memory Protection Keys CPU feature found |
1159 | in some Intel CPUs. | |
1160 | ||
ae39e9ed SK |
1161 | <module>.async_probe[=<bool>] [KNL] |
1162 | If no <bool> value is specified or if the value | |
1163 | specified is not a valid <bool>, enable asynchronous | |
1164 | probe on this module. Otherwise, enable/disable | |
1165 | asynchronous probe on this module as indicated by the | |
1166 | <bool> value. See also: module.async_probe | |
f2411da7 | 1167 | |
56aeeba8 MS |
1168 | early_ioremap_debug [KNL] |
1169 | Enable debug messages in early_ioremap support. This | |
1170 | is useful for tracking down temporary early mappings | |
1171 | which are not unmapped. | |
1172 | ||
0cb55ad2 | 1173 | earlycon= [KNL] Output early console device and options. |
0d3c673e | 1174 | |
e18409c0 CH |
1175 | When used with no options, the early console is |
1176 | determined by stdout-path property in device tree's | |
1177 | chosen node or the ACPI SPCR table if supported by | |
1178 | the platform. | |
5664f764 | 1179 | |
c41251b1 ST |
1180 | cdns,<addr>[,options] |
1181 | Start an early, polled-mode console on a Cadence | |
1182 | (xuartps) serial port at the specified address. Only | |
1183 | supported option is baud rate. If baud rate is not | |
1184 | specified, the serial port must already be setup and | |
1185 | configured. | |
6fa62fc4 | 1186 | |
0cb55ad2 RD |
1187 | uart[8250],io,<addr>[,options] |
1188 | uart[8250],mmio,<addr>[,options] | |
1917ac76 | 1189 | uart[8250],mmio32,<addr>[,options] |
6e63be3f | 1190 | uart[8250],mmio32be,<addr>[,options] |
ca782f16 | 1191 | uart[8250],0x<addr>[,options] |
0cb55ad2 RD |
1192 | Start an early, polled-mode console on the 8250/16550 |
1193 | UART at the specified I/O port or MMIO address. | |
16290246 | 1194 | MMIO inter-register address stride is either 8-bit |
6e63be3f NC |
1195 | (mmio) or 32-bit (mmio32 or mmio32be). |
1196 | If none of [io|mmio|mmio32|mmio32be], <addr> is assumed | |
1197 | to be equivalent to 'mmio'. 'options' are specified | |
1198 | in the same format described for "console=ttyS<n>"; if | |
ca782f16 | 1199 | unspecified, the h/w is not initialized. |
0cb55ad2 | 1200 | |
0d3c673e | 1201 | pl011,<addr> |
3b78fae7 | 1202 | pl011,mmio32,<addr> |
0d3c673e RH |
1203 | Start an early, polled-mode console on a pl011 serial |
1204 | port at the specified address. The pl011 serial port | |
1205 | must already be setup and configured. Options are not | |
3b78fae7 TT |
1206 | yet supported. If 'mmio32' is specified, then only |
1207 | the driver will use only 32-bit accessors to read/write | |
1208 | the device registers. | |
0d3c673e | 1209 | |
4bc2bd5a SH |
1210 | liteuart,<addr> |
1211 | Start an early console on a litex serial port at the | |
1212 | specified address. The serial port must already be | |
1213 | setup and configured. Options are not yet supported. | |
1214 | ||
736d5538 AF |
1215 | meson,<addr> |
1216 | Start an early, polled-mode console on a meson serial | |
1217 | port at the specified address. The serial port must | |
1218 | already be setup and configured. Options are not yet | |
1219 | supported. | |
1220 | ||
0efe7296 SB |
1221 | msm_serial,<addr> |
1222 | Start an early, polled-mode console on an msm serial | |
1223 | port at the specified address. The serial port | |
1224 | must already be setup and configured. Options are not | |
1225 | yet supported. | |
1226 | ||
1227 | msm_serial_dm,<addr> | |
1228 | Start an early, polled-mode console on an msm serial | |
1229 | dm port at the specified address. The serial port | |
1230 | must already be setup and configured. Options are not | |
1231 | yet supported. | |
1232 | ||
e36361d7 AF |
1233 | owl,<addr> |
1234 | Start an early, polled-mode console on a serial port | |
1235 | of an Actions Semi SoC, such as S500 or S900, at the | |
1236 | specified address. The serial port must already be | |
1237 | setup and configured. Options are not yet supported. | |
1238 | ||
c10b1332 MS |
1239 | rda,<addr> |
1240 | Start an early, polled-mode console on a serial port | |
1241 | of an RDA Micro SoC, such as RDA8810PL, at the | |
1242 | specified address. The serial port must already be | |
e36361d7 AF |
1243 | setup and configured. Options are not yet supported. |
1244 | ||
82f12ab3 PD |
1245 | sbi |
1246 | Use RISC-V SBI (Supervisor Binary Interface) for early | |
1247 | console. | |
1248 | ||
d50d7269 RH |
1249 | smh Use ARM semihosting calls for early console. |
1250 | ||
b94ba032 TF |
1251 | s3c2410,<addr> |
1252 | s3c2412,<addr> | |
1253 | s3c2440,<addr> | |
1254 | s3c6400,<addr> | |
1255 | s5pv210,<addr> | |
1256 | exynos4210,<addr> | |
1257 | Use early console provided by serial driver available | |
1258 | on Samsung SoCs, requires selecting proper type and | |
1259 | a correct base address of the selected UART port. The | |
1260 | serial port must already be setup and configured. | |
1261 | Options are not yet supported. | |
1262 | ||
ec84aa0a MB |
1263 | lantiq,<addr> |
1264 | Start an early, polled-mode console on a lantiq serial | |
1265 | (lqasc) port at the specified address. The serial port | |
1266 | must already be setup and configured. Options are not | |
1267 | yet supported. | |
1268 | ||
1d59b382 SA |
1269 | lpuart,<addr> |
1270 | lpuart32,<addr> | |
1271 | Use early console provided by Freescale LP UART driver | |
1272 | found on Freescale Vybrid and QorIQ LS1021A processors. | |
1273 | A valid base address must be provided, and the serial | |
1274 | port must already be setup and configured. | |
1275 | ||
7fe068db JN |
1276 | ec_imx21,<addr> |
1277 | ec_imx6q,<addr> | |
1278 | Start an early, polled-mode, output-only console on the | |
1279 | Freescale i.MX UART at the specified address. The UART | |
1280 | must already be setup and configured. | |
1281 | ||
f7c864e7 | 1282 | ar3700_uart,<addr> |
30530791 WD |
1283 | Start an early, polled-mode console on the |
1284 | Armada 3700 serial port at the specified | |
1285 | address. The serial port must already be setup | |
1286 | and configured. Options are not yet supported. | |
1287 | ||
43f1831b KR |
1288 | qcom_geni,<addr> |
1289 | Start an early, polled-mode console on a Qualcomm | |
1290 | Generic Interface (GENI) based serial port at the | |
1291 | specified address. The serial port must already be | |
1292 | setup and configured. Options are not yet supported. | |
1293 | ||
69c1f396 AB |
1294 | efifb,[options] |
1295 | Start an early, unaccelerated console on the EFI | |
1296 | memory mapped framebuffer (if available). On cache | |
1297 | coherent non-x86 systems that use system memory for | |
1298 | the framebuffer, pass the 'ram' option so that it is | |
1299 | mapped with the correct attributes. | |
1300 | ||
09864c1c | 1301 | linflex,<addr> |
9905f32a | 1302 | Use early console provided by Freescale LINFlexD UART |
09864c1c SM |
1303 | serial driver for NXP S32V234 SoCs. A valid base |
1304 | address must be provided, and the serial port must | |
1305 | already be setup and configured. | |
1306 | ||
4ba66a97 | 1307 | earlyprintk= [X86,SH,ARM,M68k,S390] |
1da177e4 | 1308 | earlyprintk=vga |
89175cf7 | 1309 | earlyprintk=sclp |
2482a92e | 1310 | earlyprintk=xen |
1da177e4 | 1311 | earlyprintk=serial[,ttySn[,baudrate]] |
147ea091 | 1312 | earlyprintk=serial[,0x...[,baudrate]] |
ea3acb19 | 1313 | earlyprintk=ttySn[,baudrate] |
9780bc41 | 1314 | earlyprintk=dbgp[debugController#] |
d2266bbf | 1315 | earlyprintk=pciserial[,force],bus:device.function[,baudrate] |
1b5aeebf | 1316 | earlyprintk=xdbc[xhciController#] |
1da177e4 | 1317 | |
147ea091 DH |
1318 | earlyprintk is useful when the kernel crashes before |
1319 | the normal console is initialized. It is not enabled by | |
1320 | default because it has some cosmetic problems. | |
1321 | ||
a9913044 | 1322 | Append ",keep" to not disable it when the real console |
1da177e4 LT |
1323 | takes over. |
1324 | ||
82850028 | 1325 | Only one of vga, serial, or usb debug port can |
72548e83 | 1326 | be used at a time. |
1da177e4 | 1327 | |
147ea091 DH |
1328 | Currently only ttyS0 and ttyS1 may be specified by |
1329 | name. Other I/O ports may be explicitly specified | |
1330 | on some architectures (x86 and arm at least) by | |
1331 | replacing ttySn with an I/O port address, like this: | |
1332 | earlyprintk=serial,0x1008,115200 | |
1333 | You can find the port for a given device in | |
1334 | /proc/tty/driver/serial: | |
1335 | 2: uart:ST16650V2 port:00001008 irq:18 ... | |
1da177e4 LT |
1336 | |
1337 | Interaction with the standard serial driver is not | |
1338 | very good. | |
1339 | ||
82850028 | 1340 | The VGA output is eventually overwritten by |
72548e83 | 1341 | the real console. |
1da177e4 | 1342 | |
42bc9716 | 1343 | The xen option can only be used in Xen domains. |
2482a92e | 1344 | |
89175cf7 HC |
1345 | The sclp output can only be used on s390. |
1346 | ||
d2266bbf FT |
1347 | The optional "force" to "pciserial" enables use of a |
1348 | PCI device even when its classcode is not of the | |
1349 | UART class. | |
1350 | ||
c700f013 CG |
1351 | edac_report= [HW,EDAC] Control how to report EDAC event |
1352 | Format: {"on" | "off" | "force"} | |
1353 | on: enable EDAC to report H/W event. May be overridden | |
1354 | by other higher priority error reporting module. | |
1355 | off: disable H/W event reporting through EDAC. | |
1356 | force: enforce the use of EDAC to report H/W event. | |
1357 | default: on. | |
1358 | ||
1da177e4 | 1359 | edd= [EDD] |
8c4dd606 | 1360 | Format: {"off" | "on" | "skip[mbr]"} |
1da177e4 | 1361 | |
d2f7cbe7 | 1362 | efi= [EFI] |
c03f739f HS |
1363 | Format: { "debug", "disable_early_pci_dma", |
1364 | "nochunk", "noruntime", "nosoftreserve", | |
fb1201ae | 1365 | "novamap", "no_disable_early_pci_dma" } |
c03f739f HS |
1366 | debug: enable misc debug output. |
1367 | disable_early_pci_dma: disable the busmaster bit on all | |
1368 | PCI bridges while in the EFI boot stub. | |
5a17dae4 MF |
1369 | nochunk: disable reading files in "chunks" in the EFI |
1370 | boot stub, as chunking can cause problems with some | |
1371 | firmware implementations. | |
5ae3683c | 1372 | noruntime : disable EFI runtime services support |
b617c526 DW |
1373 | nosoftreserve: The EFI_MEMORY_SP (Specific Purpose) |
1374 | attribute may cause the kernel to reserve the | |
1375 | memory range for a memory mapping driver to | |
1376 | claim. Specify efi=nosoftreserve to disable this | |
1377 | reservation and treat the memory by its base type | |
1378 | (i.e. EFI_CONVENTIONAL_MEMORY / "System RAM"). | |
c03f739f | 1379 | novamap: do not call SetVirtualAddressMap(). |
4444f854 MG |
1380 | no_disable_early_pci_dma: Leave the busmaster bit set |
1381 | on all PCI bridges while in the EFI boot stub | |
d2f7cbe7 | 1382 | |
8c58bf3e RW |
1383 | efi_no_storage_paranoia [EFI; X86] |
1384 | Using this parameter you can use more than 50% of | |
1385 | your efi variable storage. Use this parameter only if | |
1386 | you are really sure that your UEFI does sane gc and | |
1387 | fulfills the spec otherwise your board may brick. | |
1388 | ||
0f96a99d TI |
1389 | efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86] |
1390 | Add arbitrary attribute to specific memory range by | |
1391 | updating original EFI memory map. | |
1392 | Region of memory which aa attribute is added to is | |
1393 | from ss to ss+nn. | |
199c8471 | 1394 | |
0f96a99d TI |
1395 | If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000 |
1396 | is specified, EFI_MEMORY_MORE_RELIABLE(0x10000) | |
1397 | attribute is added to range 0x100000000-0x180000000 and | |
1398 | 0x10a0000000-0x1120000000. | |
1399 | ||
199c8471 DW |
1400 | If efi_fake_mem=8G@9G:0x40000 is specified, the |
1401 | EFI_MEMORY_SP(0x40000) attribute is added to | |
1402 | range 0x240000000-0x43fffffff. | |
1403 | ||
0f96a99d | 1404 | Using this parameter you can do debugging of EFI memmap |
199c8471 | 1405 | related features. For example, you can do debugging of |
0f96a99d | 1406 | Address Range Mirroring feature even if your box |
199c8471 DW |
1407 | doesn't support it, or mark specific memory as |
1408 | "soft reserved". | |
0f96a99d | 1409 | |
475fb4e8 OP |
1410 | efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT |
1411 | that is to be dynamically loaded by Linux. If there are | |
1412 | multiple variables with the same name but with different | |
1413 | vendor GUIDs, all of them will be loaded. See | |
cb1aaebe | 1414 | Documentation/admin-guide/acpi/ssdt-overlays.rst for details. |
475fb4e8 OP |
1415 | |
1416 | ||
1da177e4 LT |
1417 | eisa_irq_edge= [PARISC,HW] |
1418 | See header of drivers/parisc/eisa.c. | |
1419 | ||
d2fc83c1 RD |
1420 | ekgdboc= [X86,KGDB] Allow early kernel console debugging |
1421 | Format: ekgdboc=kbd | |
1422 | ||
1423 | This is designed to be used in conjunction with | |
1424 | the boot argument: earlyprintk=vga | |
1425 | ||
1426 | This parameter works in place of the kgdboc parameter | |
1427 | but can only be used if the backing tty is available | |
1428 | very early in the boot process. For early debugging | |
1429 | via a serial port see kgdboc_earlycon instead. | |
1430 | ||
cd4f0ef7 | 1431 | elanfreq= [X86-32] |
1da177e4 | 1432 | See comment before function elanfreq_setup() in |
71f77055 | 1433 | arch/x86/kernel/cpu/cpufreq/elanfreq.c. |
1da177e4 | 1434 | |
d3bf3795 | 1435 | elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390] |
a9913044 | 1436 | Specifies physical address of start of kernel core |
d3bf3795 MH |
1437 | image elf header and optionally the size. Generally |
1438 | kexec loader will pass this option to capture kernel. | |
330d4810 | 1439 | See Documentation/admin-guide/kdump/kdump.rst for details. |
1da177e4 | 1440 | |
0cb55ad2 RD |
1441 | enable_mtrr_cleanup [X86] |
1442 | The kernel tries to adjust MTRR layout from continuous | |
1443 | to discrete, to make X server driver able to add WB | |
1444 | entry later. This parameter enables that. | |
1445 | ||
ca1eda2d | 1446 | enable_timer_pin_1 [X86] |
0cb55ad2 RD |
1447 | Enable PIN 1 of APIC timer |
1448 | Can be useful to work around chipset bugs | |
1449 | (in particular on some ATI chipsets). | |
1450 | The kernel tries to set a reasonable default. | |
1451 | ||
8d6d51ed | 1452 | enforcing= [SELINUX] Set initial enforcing status. |
1da177e4 LT |
1453 | Format: {"0" | "1"} |
1454 | See security/selinux/Kconfig help text. | |
1455 | 0 -- permissive (log only, no denials). | |
1456 | 1 -- enforcing (deny and log). | |
1457 | Default value is 0. | |
d41415eb SS |
1458 | Value can be changed at runtime via |
1459 | /sys/fs/selinux/enforce. | |
1da177e4 | 1460 | |
a08f82d0 HY |
1461 | erst_disable [ACPI] |
1462 | Disable Error Record Serialization Table (ERST) | |
1463 | support. | |
1464 | ||
1da177e4 LT |
1465 | ether= [HW,NET] Ethernet cards parameters |
1466 | This option is obsoleted by the "netdev=" option, which | |
1467 | has equivalent usage. See its documentation for details. | |
1468 | ||
7102ebcd MZ |
1469 | evm= [EVM] |
1470 | Format: { "fix" } | |
1471 | Permit 'security.evm' to be updated regardless of | |
1472 | current integrity status. | |
1473 | ||
de1ba09b | 1474 | failslab= |
2c739ced | 1475 | fail_usercopy= |
de1ba09b AM |
1476 | fail_page_alloc= |
1477 | fail_make_request=[KNL] | |
1478 | General fault injection mechanism. | |
1479 | Format: <interval>,<probability>,<space>,<times> | |
395cf969 | 1480 | See also Documentation/fault-injection/. |
de1ba09b | 1481 | |
316cdaa1 MB |
1482 | fb_tunnels= [NET] |
1483 | Format: { initns | none } | |
1484 | See Documentation/admin-guide/sysctl/net.rst for | |
1485 | fb_tunnels_only_for_init_ns | |
1486 | ||
1da177e4 | 1487 | floppy= [HW] |
e7751617 | 1488 | See Documentation/admin-guide/blockdev/floppy.rst. |
1da177e4 | 1489 | |
f13ae30e AC |
1490 | force_pal_cache_flush |
1491 | [IA-64] Avoid check_sal_cache_flush which may hang on | |
1492 | buggy SAL_CACHE_FLUSH implementations. Using this | |
1493 | parameter will force ia64_sal_cache_flush to call | |
1494 | ia64_pal_cache_flush instead of SAL_CACHE_FLUSH. | |
1495 | ||
6dddd7a7 | 1496 | forcepae [X86-32] |
69f2366c CB |
1497 | Forcefully enable Physical Address Extension (PAE). |
1498 | Many Pentium M systems disable PAE but may have a | |
1499 | functionally usable PAE implementation. | |
1500 | Warning: use of this parameter will taint the kernel | |
1501 | and may cause unknown problems. | |
1502 | ||
d9e54076 | 1503 | ftrace=[tracer] |
2af15d6a | 1504 | [FTRACE] will set and start the specified tracer |
d9e54076 PZ |
1505 | as early as possible in order to facilitate early |
1506 | boot debugging. | |
1507 | ||
380af29b SRG |
1508 | ftrace_boot_snapshot |
1509 | [FTRACE] On boot up, a snapshot will be taken of the | |
1510 | ftrace ring buffer that can be read at: | |
1511 | /sys/kernel/tracing/snapshot. | |
1512 | This is useful if you need tracing information from kernel | |
1513 | boot up that is likely to be overridden by user space | |
1514 | start up functionality. | |
1515 | ||
cecbca96 | 1516 | ftrace_dump_on_oops[=orig_cpu] |
2af15d6a | 1517 | [FTRACE] will dump the trace buffers on oops. |
cecbca96 FW |
1518 | If no parameter is passed, ftrace will dump |
1519 | buffers of all CPUs, but if you pass orig_cpu, it will | |
1520 | dump only the buffer of the CPU that triggered the | |
1521 | oops. | |
2af15d6a SR |
1522 | |
1523 | ftrace_filter=[function-list] | |
1524 | [FTRACE] Limit the functions traced by the function | |
25942e5e | 1525 | tracer at boot up. function-list is a comma-separated |
2af15d6a SR |
1526 | list of functions. This list can be changed at run |
1527 | time by the set_ftrace_filter file in the debugfs | |
16290246 | 1528 | tracing directory. |
2af15d6a SR |
1529 | |
1530 | ftrace_notrace=[function-list] | |
1531 | [FTRACE] Do not trace the functions specified in | |
1532 | function-list. This list can be changed at run time | |
1533 | by the set_ftrace_notrace file in the debugfs | |
1534 | tracing directory. | |
d9e54076 | 1535 | |
369bc18f SA |
1536 | ftrace_graph_filter=[function-list] |
1537 | [FTRACE] Limit the top level callers functions traced | |
1538 | by the function graph tracer at boot up. | |
25942e5e | 1539 | function-list is a comma-separated list of functions |
369bc18f SA |
1540 | that can be changed at run time by the |
1541 | set_graph_function file in the debugfs tracing directory. | |
1542 | ||
0d7d9a16 NK |
1543 | ftrace_graph_notrace=[function-list] |
1544 | [FTRACE] Do not trace from the functions specified in | |
25942e5e | 1545 | function-list. This list is a comma-separated list of |
0d7d9a16 NK |
1546 | functions that can be changed at run time by the |
1547 | set_graph_notrace file in the debugfs tracing directory. | |
1548 | ||
65a50c65 TB |
1549 | ftrace_graph_max_depth=<uint> |
1550 | [FTRACE] Used with the function graph tracer. This is | |
1551 | the max depth it will trace into a function. This value | |
1552 | can be changed at run time by the max_graph_depth file | |
1553 | in the tracefs tracing directory. default: 0 (no limit) | |
1554 | ||
8375e74f SK |
1555 | fw_devlink= [KNL] Create device links between consumer and supplier |
1556 | devices by scanning the firmware to infer the | |
1557 | consumer/supplier relationships. This feature is | |
1558 | especially useful when drivers are loaded as modules as | |
1559 | it ensures proper ordering of tasks like device probing | |
1560 | (suppliers first, then consumers), supplier boot state | |
1561 | clean up (only after all consumers have probed), | |
1562 | suspend/resume & runtime PM (consumers first, then | |
1563 | suppliers). | |
1564 | Format: { off | permissive | on | rpm } | |
1565 | off -- Don't create device links from firmware info. | |
1566 | permissive -- Create device links from firmware info | |
1567 | but use it only for ordering boot state clean | |
1568 | up (sync_state() calls). | |
1569 | on -- Create device links from firmware info and use it | |
1570 | to enforce probe and suspend/resume ordering. | |
1571 | rpm -- Like "on", but also use to order runtime PM. | |
1572 | ||
19d0f5f6 SK |
1573 | fw_devlink.strict=<bool> |
1574 | [KNL] Treat all inferred dependencies as mandatory | |
1575 | dependencies. This only applies for fw_devlink=on|rpm. | |
1576 | Format: <bool> | |
1577 | ||
1da177e4 LT |
1578 | gamecon.map[2|3]= |
1579 | [HW,JOY] Multisystem joystick and NES/SNES/PSX pad | |
1580 | support via parallel port (up to 5 devices per port) | |
1581 | Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5> | |
1752118d | 1582 | See also Documentation/input/devices/joystick-parport.rst |
1da177e4 LT |
1583 | |
1584 | gamma= [HW,DRM] | |
1585 | ||
be3a5b0e | 1586 | gart_fix_e820= [X86-64] disable the fix e820 for K8 GART |
aaf23042 YL |
1587 | Format: off | on |
1588 | default: on | |
1589 | ||
2521f2c2 PO |
1590 | gcov_persist= [GCOV] When non-zero (default), profiling data for |
1591 | kernel modules is saved and remains accessible via | |
1592 | debugfs, even when the module is unloaded/reloaded. | |
1593 | When zero, profiling data is discarded and associated | |
1594 | debugfs files are removed at module unload time. | |
1595 | ||
47512cfd TG |
1596 | goldfish [X86] Enable the goldfish android emulator platform. |
1597 | Don't use this when you are not running on the | |
1598 | android emulator | |
1599 | ||
3eb52226 AD |
1600 | gpio-mockup.gpio_mockup_ranges |
1601 | [HW] Sets the ranges of gpiochip of for this device. | |
1602 | Format: <start1>,<end1>,<start2>,<end2>... | |
6984a320 AD |
1603 | gpio-mockup.gpio_mockup_named_lines |
1604 | [HW] Let the driver know GPIO lines should be named. | |
3eb52226 | 1605 | |
1da177e4 | 1606 | gpt [EFI] Forces disk with valid GPT signature but |
6c5de79b DB |
1607 | invalid Protective MBR to be treated as GPT. If the |
1608 | primary GPT is corrupted, it enables the backup/alternate | |
1609 | GPT to be used instead. | |
1da177e4 | 1610 | |
6cec9b07 AL |
1611 | grcan.enable0= [HW] Configuration of physical interface 0. Determines |
1612 | the "Enable 0" bit of the configuration register. | |
1613 | Format: 0 | 1 | |
1614 | Default: 0 | |
1615 | grcan.enable1= [HW] Configuration of physical interface 1. Determines | |
1616 | the "Enable 0" bit of the configuration register. | |
1617 | Format: 0 | 1 | |
1618 | Default: 0 | |
1619 | grcan.select= [HW] Select which physical interface to use. | |
1620 | Format: 0 | 1 | |
1621 | Default: 0 | |
1622 | grcan.txsize= [HW] Sets the size of the tx buffer. | |
1623 | Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0. | |
1624 | Default: 1024 | |
1625 | grcan.rxsize= [HW] Sets the size of the rx buffer. | |
1626 | Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0. | |
1627 | Default: 1024 | |
1628 | ||
d2fc83c1 RD |
1629 | hardened_usercopy= |
1630 | [KNL] Under CONFIG_HARDENED_USERCOPY, whether | |
1631 | hardening is enabled for this boot. Hardened | |
1632 | usercopy checking is used to protect the kernel | |
1633 | from reading or writing beyond known memory | |
1634 | allocation boundaries as a proactive defense | |
1635 | against bounds-checking flaws in the kernel's | |
1636 | copy_to_user()/copy_from_user() interface. | |
1637 | on Perform hardened usercopy checks (default). | |
1638 | off Disable hardened usercopy checks. | |
1639 | ||
55537871 JK |
1640 | hardlockup_all_cpu_backtrace= |
1641 | [KNL] Should the hard-lockup detector generate | |
1642 | backtraces on all cpus. | |
f117955a | 1643 | Format: 0 | 1 |
55537871 | 1644 | |
1da177e4 LT |
1645 | hashdist= [KNL,NUMA] Large hashes allocated during boot |
1646 | are distributed across NUMA nodes. Defaults on | |
16290246 | 1647 | for 64-bit NUMA, off otherwise. |
a9913044 | 1648 | Format: 0 | 1 (for off | on) |
1da177e4 LT |
1649 | |
1650 | hcl= [IA-64] SGI's Hardware Graph compatibility layer | |
1651 | ||
1652 | hd= [EIDE] (E)IDE hard drive subsystem geometry | |
1653 | Format: <cyl>,<head>,<sect> | |
1654 | ||
ea8c071c HY |
1655 | hest_disable [ACPI] |
1656 | Disable Hardware Error Source Table (HEST) support; | |
1657 | corresponding firmware-first mode error processing | |
1658 | logic will be disabled. | |
1659 | ||
d2fc83c1 RD |
1660 | hibernate= [HIBERNATION] |
1661 | noresume Don't check if there's a hibernation image | |
1662 | present during boot. | |
1663 | nocompress Don't compress/decompress hibernation images. | |
1664 | no Disable hibernation and resume. | |
1665 | protect_image Turn on image protection during restoration | |
1666 | (that will set all pages holding image data | |
1667 | during restoration read-only). | |
1668 | ||
1da177e4 LT |
1669 | highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact |
1670 | size of <nn>. This works even on boxes that have no | |
1671 | highmem otherwise. This also works to reduce highmem | |
1672 | size on bigger boxes. | |
1673 | ||
54cdfdb4 TG |
1674 | highres= [KNL] Enable/disable high resolution timer mode. |
1675 | Valid parameters: "on", "off" | |
1676 | Default: "on" | |
1677 | ||
0cb55ad2 RD |
1678 | hlt [BUGS=ARM,SH] |
1679 | ||
5a704629 DM |
1680 | hostname= [KNL] Set the hostname (aka UTS nodename). |
1681 | Format: <string> | |
1682 | This allows setting the system's hostname during early | |
1683 | startup. This sets the name returned by gethostname. | |
1684 | Using this parameter to set the hostname makes it | |
1685 | possible to ensure the hostname is correctly set before | |
1686 | any userspace processes run, avoiding the possibility | |
1687 | that a process may call gethostname before the hostname | |
1688 | has been explicitly set, resulting in the calling | |
1689 | process getting an incorrect result. The string must | |
1690 | not exceed the maximum allowed hostname length (usually | |
1691 | 64 characters) and will be truncated otherwise. | |
1692 | ||
0cb55ad2 RD |
1693 | hpet= [X86-32,HPET] option to control HPET usage |
1694 | Format: { enable (default) | disable | force | | |
1695 | verbose } | |
1696 | disable: disable HPET and use PIT instead | |
1697 | force: allow force enabled of undocumented chips (ICH4, | |
1698 | VIA, nVidia) | |
1699 | verbose: show contents of HPET registers during setup | |
1700 | ||
3d035f58 PB |
1701 | hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET |
1702 | registers. Default set by CONFIG_HPET_MMAP_DEFAULT. | |
1703 | ||
282f4214 MK |
1704 | hugepages= [HW] Number of HugeTLB pages to allocate at boot. |
1705 | If this follows hugepagesz (below), it specifies | |
1706 | the number of pages of hugepagesz to be allocated. | |
1707 | If this is the first HugeTLB parameter on the command | |
1708 | line, it specifies the number of pages to allocate for | |
b5389086 ZY |
1709 | the default huge page size. If using node format, the |
1710 | number of pages to allocate per-node can be specified. | |
1711 | See also Documentation/admin-guide/mm/hugetlbpage.rst. | |
1712 | Format: <integer> or (node format) | |
1713 | <node>:<integer>[,<node>:<integer>] | |
282f4214 MK |
1714 | |
1715 | hugepagesz= | |
1716 | [HW] The size of the HugeTLB pages. This is used in | |
1717 | conjunction with hugepages (above) to allocate huge | |
1718 | pages of a specific size at boot. The pair | |
1719 | hugepagesz=X hugepages=Y can be specified once for | |
1720 | each supported huge page size. Huge page sizes are | |
1721 | architecture dependent. See also | |
1722 | Documentation/admin-guide/mm/hugetlbpage.rst. | |
1723 | Format: size[KMG] | |
6902aa84 | 1724 | |
389cfd96 RD |
1725 | hugetlb_cma= [HW,CMA] The size of a CMA area used for allocation |
1726 | of gigantic hugepages. Or using node format, the size | |
1727 | of a CMA area per node can be specified. | |
1728 | Format: nn[KMGTPE] or (node format) | |
1729 | <node>:nn[KMGTPE][,<node>:nn[KMGTPE]] | |
1730 | ||
1731 | Reserve a CMA area of given size and allocate gigantic | |
1732 | hugepages using the CMA allocator. If enabled, the | |
1733 | boot-time allocation of gigantic hugepages is skipped. | |
1734 | ||
e9fdff87 | 1735 | hugetlb_free_vmemmap= |
47010c04 | 1736 | [KNL] Reguires CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP |
e9fdff87 | 1737 | enabled. |
dff03381 | 1738 | Control if HugeTLB Vmemmap Optimization (HVO) is enabled. |
e9fdff87 | 1739 | Allows heavy hugetlb users to free up some more |
e7d32485 | 1740 | memory (7 * PAGE_SIZE for each 2MB hugetlb page). |
dff03381 | 1741 | Format: { on | off (default) } |
e9fdff87 | 1742 | |
dff03381 MS |
1743 | on: enable HVO |
1744 | off: disable HVO | |
e9fdff87 | 1745 | |
47010c04 | 1746 | Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y, |
e6d41f12 MS |
1747 | the default is on. |
1748 | ||
66361095 MS |
1749 | Note that the vmemmap pages may be allocated from the added |
1750 | memory block itself when memory_hotplug.memmap_on_memory is | |
1751 | enabled, those vmemmap pages cannot be optimized even if this | |
1752 | feature is enabled. Other vmemmap pages not allocated from | |
1753 | the added memory block itself do not be affected. | |
4bab4964 | 1754 | |
a49d9c0a OS |
1755 | hung_task_panic= |
1756 | [KNL] Should the hung task detector generate panics. | |
f117955a | 1757 | Format: 0 | 1 |
cef7125d | 1758 | |
b467f3ef | 1759 | A value of 1 instructs the kernel to panic when a |
a49d9c0a OS |
1760 | hung task is detected. The default value is controlled |
1761 | by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time | |
1762 | option. The value selected by this boot parameter can | |
1763 | be changed later by the kernel.hung_task_panic sysctl. | |
1764 | ||
6dddd7a7 TB |
1765 | hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC) |
1766 | terminal devices. Valid values: 0..8 | |
1767 | hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs. | |
1768 | If specified, z/VM IUCV HVC accepts connections | |
1769 | from listed z/VM user IDs only. | |
3a025de6 YS |
1770 | |
1771 | hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations | |
1772 | which allow the hypervisor to 'idle' the | |
1773 | guest on lock contention. | |
1774 | ||
7bf69395 FDN |
1775 | keep_bootcon [KNL] |
1776 | Do not unregister boot console at start. This is only | |
1777 | useful for debugging when something happens in the window | |
1778 | between unregistering the boot console and initializing | |
1779 | the real console. | |
1780 | ||
6dddd7a7 TB |
1781 | i2c_bus= [HW] Override the default board specific I2C bus speed |
1782 | or register an additional I2C bus that is not | |
1783 | registered from board initialization code. | |
1784 | Format: | |
1785 | <bus_id>,<clkrate> | |
3a853fb9 | 1786 | |
36d95739 | 1787 | i8042.debug [HW] Toggle i8042 debug mode |
e1443d28 SCP |
1788 | i8042.unmask_kbd_data |
1789 | [HW] Enable printing of interrupt data from the KBD port | |
1790 | (disabled by default, and as a pre-condition | |
1791 | requires that i8042.debug=1 be enabled) | |
1da177e4 | 1792 | i8042.direct [HW] Put keyboard port into non-translated mode |
84eb8d06 ML |
1793 | i8042.dumbkbd [HW] Pretend that controller can only read data from |
1794 | keyboard and cannot control its state | |
1da177e4 LT |
1795 | (Don't attempt to blink the leds) |
1796 | i8042.noaux [HW] Don't check for auxiliary (== mouse) port | |
945ef0d4 | 1797 | i8042.nokbd [HW] Don't check/create keyboard port |
75d08c78 JK |
1798 | i8042.noloop [HW] Disable the AUX Loopback command while probing |
1799 | for the AUX port | |
1da177e4 | 1800 | i8042.nomux [HW] Don't check presence of an active multiplexing |
e55a3366 | 1801 | controller |
1da177e4 LT |
1802 | i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX |
1803 | controllers | |
24775d65 | 1804 | i8042.notimeout [HW] Ignore timeout condition signalled by controller |
930e1924 MPS |
1805 | i8042.reset [HW] Reset the controller during init, cleanup and |
1806 | suspend-to-ram transitions, only during s2r | |
1807 | transitions, or never reset | |
1808 | Format: { 1 | Y | y | 0 | N | n } | |
1809 | 1, Y, y: always reset controller | |
1810 | 0, N, n: don't ever reset controller | |
1811 | Default: only on s2r transitions on x86; most other | |
1812 | architectures force reset to be always executed | |
1da177e4 | 1813 | i8042.unlock [HW] Unlock (ignore) the keylock |
6dddd7a7 | 1814 | i8042.kbdreset [HW] Reset device connected to KBD port |
9222ba68 TI |
1815 | i8042.probe_defer |
1816 | [HW] Allow deferred probing upon i8042 probe errors | |
1da177e4 LT |
1817 | |
1818 | i810= [HW,DRM] | |
1819 | ||
4dca20ef | 1820 | i915.invert_brightness= |
7bd90909 CE |
1821 | [DRM] Invert the sense of the variable that is used to |
1822 | set the brightness of the panel backlight. Normally a | |
4dca20ef CE |
1823 | brightness value of 0 indicates backlight switched off, |
1824 | and the maximum of the brightness value sets the backlight | |
1825 | to maximum brightness. If this parameter is set to 0 | |
1826 | (default) and the machine requires it, or this parameter | |
1827 | is set to 1, a brightness value of 0 sets the backlight | |
1828 | to maximum brightness, and the maximum of the brightness | |
1829 | value switches the backlight off. | |
1830 | -1 -- never invert brightness | |
1831 | 0 -- machine default | |
1832 | 1 -- force brightness inversion | |
7bd90909 | 1833 | |
1da177e4 LT |
1834 | icn= [HW,ISDN] |
1835 | Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]] | |
1836 | ||
0cb55ad2 | 1837 | |
f039b754 | 1838 | idle= [X86] |
69fb3676 | 1839 | Format: idle=poll, idle=halt, idle=nomwait |
ada9cfdd RD |
1840 | Poll forces a polling idle loop that can slightly |
1841 | improve the performance of waking up a idle CPU, but | |
1842 | will use a lot of power and make the system run hot. | |
1843 | Not recommended. | |
ada9cfdd | 1844 | idle=halt: Halt is forced to be used for CPU idle. |
c1e3b377 | 1845 | In such case C2/C3 won't be used again. |
ada9cfdd | 1846 | idle=nomwait: Disable mwait for CPU C-states |
a9913044 | 1847 | |
03d939c7 DJ |
1848 | idxd.sva= [HW] |
1849 | Format: <bool> | |
1850 | Allow force disabling of Shared Virtual Memory (SVA) | |
1851 | support for the idxd driver. By default it is set to | |
1852 | true (1). | |
1853 | ||
ade8a86b DJ |
1854 | idxd.tc_override= [HW] |
1855 | Format: <bool> | |
1856 | Allow override of default traffic class configuration | |
1857 | for the device. By default it is set to false (0). | |
1858 | ||
503943e0 MR |
1859 | ieee754= [MIPS] Select IEEE Std 754 conformance mode |
1860 | Format: { strict | legacy | 2008 | relaxed } | |
1861 | Default: strict | |
1862 | ||
1863 | Choose which programs will be accepted for execution | |
1864 | based on the IEEE 754 NaN encoding(s) supported by | |
1865 | the FPU and the NaN encoding requested with the value | |
1866 | of an ELF file header flag individually set by each | |
1867 | binary. Hardware implementations are permitted to | |
1868 | support either or both of the legacy and the 2008 NaN | |
1869 | encoding mode. | |
1870 | ||
1871 | Available settings are as follows: | |
1872 | strict accept binaries that request a NaN encoding | |
1873 | supported by the FPU | |
1874 | legacy only accept legacy-NaN binaries, if supported | |
1875 | by the FPU | |
1876 | 2008 only accept 2008-NaN binaries, if supported | |
1877 | by the FPU | |
1878 | relaxed accept any binaries regardless of whether | |
1879 | supported by the FPU | |
1880 | ||
1881 | The FPU emulator is always able to support both NaN | |
1882 | encodings, so if no FPU hardware is present or it has | |
1883 | been disabled with 'nofpu', then the settings of | |
1884 | 'legacy' and '2008' strap the emulator accordingly, | |
1885 | 'relaxed' straps the emulator for both legacy-NaN and | |
1886 | 2008-NaN, whereas 'strict' enables legacy-NaN only on | |
1887 | legacy processors and both NaN encodings on MIPS32 or | |
1888 | MIPS64 CPUs. | |
1889 | ||
1890 | The setting for ABS.fmt/NEG.fmt instruction execution | |
1891 | mode generally follows that for the NaN encoding, | |
1892 | except where unsupported by hardware. | |
1893 | ||
79290822 IM |
1894 | ignore_loglevel [KNL] |
1895 | Ignore loglevel setting - this will print /all/ | |
1896 | kernel messages to the console. Useful for debugging. | |
0eca6b7c YZ |
1897 | We also add it as printk module parameter, so users |
1898 | could change it dynamically, usually by | |
1899 | /sys/module/printk/parameters/ignore_loglevel. | |
79290822 | 1900 | |
d977d56c KK |
1901 | ignore_rlimit_data |
1902 | Ignore RLIMIT_DATA setting for data mappings, | |
1903 | print warning at first misuse. Can be changed via | |
1904 | /sys/module/kernel/parameters/ignore_rlimit_data. | |
1905 | ||
1da177e4 LT |
1906 | ihash_entries= [KNL] |
1907 | Set number of hash buckets for inode cache. | |
1908 | ||
2fe5d6de | 1909 | ima_appraise= [IMA] appraise integrity measurements |
2faa6ef3 | 1910 | Format: { "off" | "enforce" | "fix" | "log" } |
2fe5d6de MZ |
1911 | default: "enforce" |
1912 | ||
41475a3e | 1913 | ima_appraise_tcb [IMA] Deprecated. Use ima_policy= instead. |
07f6a794 MZ |
1914 | The builtin appraise policy appraises all files |
1915 | owned by uid=0. | |
1916 | ||
d68a6fe9 MZ |
1917 | ima_canonical_fmt [IMA] |
1918 | Use the canonical format for the binary runtime | |
1919 | measurements, instead of host native format. | |
1920 | ||
3323eec9 | 1921 | ima_hash= [IMA] |
e7a2ad7e MZ |
1922 | Format: { md5 | sha1 | rmd160 | sha256 | sha384 |
1923 | | sha512 | ... } | |
3323eec9 MZ |
1924 | default: "sha1" |
1925 | ||
e7a2ad7e MZ |
1926 | The list of supported hash algorithms is defined |
1927 | in crypto/hash_info.h. | |
1928 | ||
24fd03c8 | 1929 | ima_policy= [IMA] |
33ce9549 | 1930 | The builtin policies to load during IMA setup. |
9e67028e | 1931 | Format: "tcb | appraise_tcb | secure_boot | |
03cee168 | 1932 | fail_securely | critical_data" |
33ce9549 MZ |
1933 | |
1934 | The "tcb" policy measures all programs exec'd, files | |
1935 | mmap'd for exec, and all files opened with the read | |
1936 | mode bit set by either the effective uid (euid=0) or | |
1937 | uid=0. | |
1938 | ||
1939 | The "appraise_tcb" policy appraises the integrity of | |
41475a3e | 1940 | all files owned by root. |
24fd03c8 | 1941 | |
503ceaef MZ |
1942 | The "secure_boot" policy appraises the integrity |
1943 | of files (eg. kexec kernel image, kernel modules, | |
1944 | firmware, policy, etc) based on file signatures. | |
24fd03c8 | 1945 | |
9e67028e MZ |
1946 | The "fail_securely" policy forces file signature |
1947 | verification failure also on privileged mounted | |
1948 | filesystems with the SB_I_UNVERIFIABLE_SIGNATURE | |
1949 | flag. | |
1950 | ||
03cee168 LR |
1951 | The "critical_data" policy measures kernel integrity |
1952 | critical data. | |
1953 | ||
24fd03c8 | 1954 | ima_tcb [IMA] Deprecated. Use ima_policy= instead. |
5789ba3b EP |
1955 | Load a policy which meets the needs of the Trusted |
1956 | Computing Base. This means IMA will measure all | |
1957 | programs exec'd, files mmap'd for exec, and all files | |
1958 | opened for read by uid=0. | |
1959 | ||
6dddd7a7 | 1960 | ima_template= [IMA] |
9b9d4ce5 | 1961 | Select one of defined IMA measurements template formats. |
989dc725 MZ |
1962 | Formats: { "ima" | "ima-ng" | "ima-ngv2" | "ima-sig" | |
1963 | "ima-sigv2" } | |
9b9d4ce5 RS |
1964 | Default: "ima-ng" |
1965 | ||
c2426d2a | 1966 | ima_template_fmt= |
6dddd7a7 | 1967 | [IMA] Define a custom template format. |
c2426d2a RS |
1968 | Format: { "field1|...|fieldN" } |
1969 | ||
3bcced39 DK |
1970 | ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage |
1971 | Format: <min_file_size> | |
1972 | Set the minimal file size for using asynchronous hash. | |
1973 | If left unspecified, ahash usage is disabled. | |
1974 | ||
1975 | ahash performance varies for different data sizes on | |
1976 | different crypto accelerators. This option can be used | |
1977 | to achieve the best performance for a particular HW. | |
1978 | ||
6edf7a89 DK |
1979 | ima.ahash_bufsize= [IMA] Asynchronous hash buffer size |
1980 | Format: <bufsize> | |
1981 | Set hashing buffer size. Default: 4k. | |
1982 | ||
1983 | ahash performance varies for different chunk sizes on | |
1984 | different crypto accelerators. This option can be used | |
1985 | to achieve best performance for particular HW. | |
1986 | ||
1da177e4 LT |
1987 | init= [KNL] |
1988 | Format: <full_path> | |
1989 | Run specified binary instead of /sbin/init as init | |
1990 | process. | |
1991 | ||
1992 | initcall_debug [KNL] Trace initcalls as they are executed. Useful | |
1993 | for working out where the kernel is dying during | |
1994 | startup. | |
1995 | ||
7b0b73d7 PB |
1996 | initcall_blacklist= [KNL] Do not execute a comma-separated list of |
1997 | initcall functions. Useful for debugging built-in | |
1998 | modules and initcalls. | |
1999 | ||
e7cb072e RV |
2000 | initramfs_async= [KNL] |
2001 | Format: <bool> | |
2002 | Default: 1 | |
2003 | This parameter controls whether the initramfs | |
2004 | image is unpacked asynchronously, concurrently | |
2005 | with devices being probed and | |
2006 | initialized. This should normally just work, | |
2007 | but as a debugging aid, one can get the | |
2008 | historical behaviour of the initramfs | |
2009 | unpacking being completed before device_ and | |
2010 | late_ initcalls. | |
2011 | ||
1da177e4 LT |
2012 | initrd= [BOOT] Specify the location of the initial ramdisk |
2013 | ||
694cfd87 RM |
2014 | initrdmem= [KNL] Specify a physical address and size from which to |
2015 | load the initrd. If an initrd is compiled in or | |
2016 | specified in the bootparams, it takes priority over this | |
2017 | setting. | |
2018 | Format: ss[KMG],nn[KMG] | |
2019 | Default is 0, 0 | |
2020 | ||
6471384a AP |
2021 | init_on_alloc= [MM] Fill newly allocated pages and heap objects with |
2022 | zeroes. | |
2023 | Format: 0 | 1 | |
2024 | Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON. | |
2025 | ||
2026 | init_on_free= [MM] Fill freed pages and heap objects with zeroes. | |
2027 | Format: 0 | 1 | |
2028 | Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON. | |
2029 | ||
be3a5b0e | 2030 | init_pkru= [X86] Specify the default memory protection keys rights |
acd547b2 DH |
2031 | register contents for all processes. 0x55555554 by |
2032 | default (disallow access to all but pkey 0). Can | |
2033 | override in debugfs after boot. | |
2034 | ||
1da177e4 LT |
2035 | inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver |
2036 | Format: <irq> | |
2037 | ||
be3a5b0e | 2038 | int_pln_enable [X86] Enable power limit notification interrupt |
6bb2ff84 | 2039 | |
d726d8d7 MZ |
2040 | integrity_audit=[IMA] |
2041 | Format: { "0" | "1" } | |
2042 | 0 -- basic integrity auditing messages. (Default) | |
2043 | 1 -- additional integrity auditing messages. | |
2044 | ||
ba395927 | 2045 | intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option |
0cd5c3c8 KM |
2046 | on |
2047 | Enable intel iommu driver. | |
ba395927 KA |
2048 | off |
2049 | Disable intel iommu driver. | |
2050 | igfx_off [Default Off] | |
2051 | By default, gfx is mapped as normal device. If a gfx | |
2052 | device has a dedicated DMAR unit, the DMAR unit is | |
2053 | bypassed by not enabling DMAR with this option. In | |
2054 | this case, gfx device will use physical address for | |
2055 | DMA. | |
5e0d2a6f | 2056 | strict [Default Off] |
1d479f16 | 2057 | Deprecated, equivalent to iommu.strict=1. |
6dd9a7c7 YS |
2058 | sp_off [Default Off] |
2059 | By default, super page will be supported if Intel IOMMU | |
2060 | has the capability. With this option, super page will | |
2061 | not be supported. | |
792fb43c LB |
2062 | sm_on |
2063 | Enable the Intel IOMMU scalable mode if the hardware | |
2064 | advertises that it has support for the scalable mode | |
2065 | translation. | |
2066 | sm_off | |
2067 | Disallow use of the Intel IOMMU scalable mode. | |
bfd20f1c SL |
2068 | tboot_noforce [Default Off] |
2069 | Do not force the Intel IOMMU enabled under tboot. | |
2070 | By default, tboot will force Intel IOMMU on, which | |
2071 | could harm performance of some high-throughput | |
2072 | devices like 40GBit network cards, even if identity | |
2073 | mapping is enabled. | |
2074 | Note that using this option lowers the security | |
2075 | provided by tboot because it makes the system | |
2076 | vulnerable to DMA attacks. | |
2e92c7ad MI |
2077 | |
2078 | intel_idle.max_cstate= [KNL,HW,ACPI,X86] | |
2079 | 0 disables intel_idle and fall back on acpi_idle. | |
22c6bbe4 | 2080 | 1 to 9 specify maximum depth of C-state. |
2e92c7ad | 2081 | |
6dddd7a7 TB |
2082 | intel_pstate= [X86] |
2083 | disable | |
2084 | Do not enable intel_pstate as the default | |
2085 | scaling driver for the supported processors | |
2086 | passive | |
2087 | Use intel_pstate as a scaling driver, but configure it | |
2088 | to work with generic cpufreq governors (instead of | |
2089 | enabling its internal governor). This mode cannot be | |
2090 | used along with the hardware-managed P-states (HWP) | |
2091 | feature. | |
2092 | force | |
2093 | Enable intel_pstate on systems that prohibit it by default | |
2094 | in favor of acpi-cpufreq. Forcing the intel_pstate driver | |
2095 | instead of acpi-cpufreq may disable platform features, such | |
2096 | as thermal controls and power capping, that rely on ACPI | |
2097 | P-States information being indicated to OSPM and therefore | |
2098 | should be used with caution. This option does not work with | |
2099 | processors that aren't supported by the intel_pstate driver | |
2100 | or on platforms that use pcc-cpufreq instead of acpi-cpufreq. | |
2101 | no_hwp | |
2102 | Do not enable hardware P state control (HWP) | |
2103 | if available. | |
2104 | hwp_only | |
2105 | Only load intel_pstate on systems which support | |
2106 | hardware P state control (HWP) if available. | |
2107 | support_acpi_ppc | |
2108 | Enforce ACPI _PPC performance limits. If the Fixed ACPI | |
2109 | Description Table, specifies preferred power management | |
2110 | profile as "Enterprise Server" or "Performance Server", | |
2111 | then this feature is turned on by default. | |
2112 | per_cpu_perf_limits | |
2113 | Allow per-logical-CPU P-State performance control limits using | |
2114 | cpufreq sysfs interface | |
6be26498 | 2115 | |
d1423d56 | 2116 | intremap= [X86-64, Intel-IOMMU] |
d1423d56 CW |
2117 | on enable Interrupt Remapping (default) |
2118 | off disable Interrupt Remapping | |
2119 | nosid disable Source ID checking | |
41750d31 SS |
2120 | no_x2apic_optout |
2121 | BIOS x2APIC opt-out request will be ignored | |
b7d20631 | 2122 | nopost disable Interrupt Posting |
d1423d56 | 2123 | |
0cb55ad2 RD |
2124 | iomem= Disable strict checking of access to MMIO memory |
2125 | strict regions from userspace. | |
2126 | relaxed | |
2127 | ||
be3a5b0e | 2128 | iommu= [X86] |
0cb55ad2 RD |
2129 | off |
2130 | force | |
2131 | noforce | |
2132 | biomerge | |
2133 | panic | |
2134 | nopanic | |
2135 | merge | |
2136 | nomerge | |
0cb55ad2 | 2137 | soft |
be3a5b0e RD |
2138 | pt [X86] |
2139 | nopt [X86] | |
4e287840 TLSC |
2140 | nobypass [PPC/POWERNV] |
2141 | Disable IOMMU bypass, using IOMMU for PCI devices. | |
bcb71abe | 2142 | |
3542dcb1 RM |
2143 | iommu.forcedac= [ARM64, X86] Control IOVA allocation for PCI devices. |
2144 | Format: { "0" | "1" } | |
2145 | 0 - Try to allocate a 32-bit DMA address first, before | |
2146 | falling back to the full range if needed. | |
2147 | 1 - Allocate directly from the full usable range, | |
2148 | forcing Dual Address Cycle for PCI cards supporting | |
2149 | greater than 32-bit addressing. | |
2150 | ||
531353e6 | 2151 | iommu.strict= [ARM64, X86] Configure TLB invalidation behaviour |
68a6efe8 ZL |
2152 | Format: { "0" | "1" } |
2153 | 0 - Lazy mode. | |
2154 | Request that DMA unmap operations use deferred | |
2155 | invalidation of hardware TLBs, for increased | |
2156 | throughput at the cost of reduced device isolation. | |
2157 | Will fall back to strict mode if not supported by | |
2158 | the relevant IOMMU driver. | |
712d8f20 | 2159 | 1 - Strict mode. |
68a6efe8 ZL |
2160 | DMA unmap operations invalidate IOMMU hardware TLBs |
2161 | synchronously. | |
e96763ec RM |
2162 | unset - Use value of CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT}. |
2163 | Note: on x86, strict mode specified via one of the | |
2164 | legacy driver-specific options takes precedence. | |
68a6efe8 | 2165 | |
fccb4e3b | 2166 | iommu.passthrough= |
c8fb436b | 2167 | [ARM64, X86] Configure DMA to bypass the IOMMU by default. |
fccb4e3b WD |
2168 | Format: { "0" | "1" } |
2169 | 0 - Use IOMMU translation for DMA. | |
2170 | 1 - Bypass the IOMMU for DMA. | |
9d723b4c | 2171 | unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH. |
0cb55ad2 | 2172 | |
7c42376e | 2173 | io7= [HW] IO7 for Marvel-based Alpha systems |
0cb55ad2 RD |
2174 | See comment before marvel_specify_io7 in |
2175 | arch/alpha/kernel/core_marvel.c. | |
2176 | ||
6cececfc | 2177 | io_delay= [X86] I/O delay method |
6e7c4025 IM |
2178 | 0x80 |
2179 | Standard port 0x80 based delay | |
2180 | 0xed | |
2181 | Alternate port 0xed based delay (needed on some systems) | |
b02aae9c | 2182 | udelay |
6e7c4025 IM |
2183 | Simple two microseconds delay |
2184 | none | |
2185 | No delay | |
b02aae9c | 2186 | |
1da177e4 | 2187 | ip= [IP_PNP] |
3eb30c51 | 2188 | See Documentation/admin-guide/nfs/nfsroot.rst. |
1da177e4 | 2189 | |
5ac893b8 WL |
2190 | ipcmni_extend [KNL] Extend the maximum number of unique System V |
2191 | IPC identifiers from 32,768 to 16,777,216. | |
2192 | ||
fbf19803 | 2193 | irqaffinity= [SMP] Set the default irq affinity mask |
2d13e6ca | 2194 | The argument is a cpu list, as described above. |
fbf19803 | 2195 | |
0962289b MZ |
2196 | irqchip.gicv2_force_probe= |
2197 | [ARM, ARM64] | |
2198 | Format: <bool> | |
2199 | Force the kernel to look for the second 4kB page | |
2200 | of a GICv2 controller even if the memory range | |
2201 | exposed by the device tree is too small. | |
2202 | ||
f736d65d MZ |
2203 | irqchip.gicv3_nolpi= |
2204 | [ARM, ARM64] | |
2205 | Force the kernel to ignore the availability of | |
2206 | LPIs (and by consequence ITSs). Intended for system | |
2207 | that use the kernel as a bootloader, and thus want | |
2208 | to let secondary kernels in charge of setting up | |
2209 | LPIs. | |
2210 | ||
bc3c03cc JT |
2211 | irqchip.gicv3_pseudo_nmi= [ARM64] |
2212 | Enables support for pseudo-NMIs in the kernel. This | |
2213 | requires the kernel to be built with | |
2214 | CONFIG_ARM64_PSEUDO_NMI. | |
2215 | ||
200803df AC |
2216 | irqfixup [HW] |
2217 | When an interrupt is not handled search all handlers | |
2218 | for it. Intended to get systems with badly broken | |
2219 | firmware running. | |
2220 | ||
2221 | irqpoll [HW] | |
2222 | When an interrupt is not handled search all handlers | |
2223 | for it. Also check all handlers each timer | |
2224 | interrupt. Intended to get systems with badly broken | |
2225 | firmware running. | |
2226 | ||
1da177e4 | 2227 | isapnp= [ISAPNP] |
a9913044 | 2228 | Format: <RDP>,<reset>,<pci_scan>,<verbosity> |
1da177e4 | 2229 | |
d94d1053 | 2230 | isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance. |
b0d40d2b FW |
2231 | [Deprecated - use cpusets instead] |
2232 | Format: [flag-list,]<cpu-list> | |
2233 | ||
2234 | Specify one or more CPUs to isolate from disturbances | |
2235 | specified in the flag list (default: domain): | |
2236 | ||
2237 | nohz | |
2238 | Disable the tick when a single task runs. | |
083c6eea FW |
2239 | |
2240 | A residual 1Hz tick is offloaded to workqueues, which you | |
2241 | need to affine to housekeeping through the global | |
2242 | workqueue's affinity configured via the | |
2243 | /sys/devices/virtual/workqueue/cpumask sysfs file, or | |
2244 | by using the 'domain' flag described below. | |
2245 | ||
2246 | NOTE: by default the global workqueue runs on all CPUs, | |
2247 | so to protect individual CPUs the 'cpumask' file has to | |
2248 | be configured manually after bootup. | |
2249 | ||
b0d40d2b FW |
2250 | domain |
2251 | Isolate from the general SMP balancing and scheduling | |
2252 | algorithms. Note that performing domain isolation this way | |
2253 | is irreversible: it's not possible to bring back a CPU to | |
2254 | the domains once isolated through isolcpus. It's strongly | |
2255 | advised to use cpusets instead to disable scheduler load | |
2256 | balancing through the "cpuset.sched_load_balance" file. | |
2257 | It offers a much more flexible interface where CPUs can | |
2258 | move in and out of an isolated set anytime. | |
2259 | ||
2260 | You can move a process onto or off an "isolated" CPU via | |
2261 | the CPU affinity syscalls or cpuset. | |
2262 | <cpu number> begins at 0 and the maximum value is | |
2263 | "number of CPUs in system - 1". | |
2264 | ||
11ea68f5 ML |
2265 | managed_irq |
2266 | ||
2267 | Isolate from being targeted by managed interrupts | |
2268 | which have an interrupt mask containing isolated | |
2269 | CPUs. The affinity of managed interrupts is | |
2270 | handled by the kernel and cannot be changed via | |
2271 | the /proc/irq/* interfaces. | |
2272 | ||
2273 | This isolation is best effort and only effective | |
2274 | if the automatically assigned interrupt mask of a | |
2275 | device queue contains isolated and housekeeping | |
2276 | CPUs. If housekeeping CPUs are online then such | |
2277 | interrupts are directed to the housekeeping CPU | |
2278 | so that IO submitted on the housekeeping CPU | |
2279 | cannot disturb the isolated CPU. | |
2280 | ||
2281 | If a queue's affinity mask contains only isolated | |
2282 | CPUs then this parameter has no effect on the | |
2283 | interrupt routing decision, though interrupts are | |
2284 | only delivered when tasks running on those | |
2285 | isolated CPUs submit IO. IO submitted on | |
2286 | housekeeping CPUs has no influence on those | |
2287 | queues. | |
1da177e4 | 2288 | |
11ea68f5 | 2289 | The format of <cpu-list> is described above. |
1da177e4 | 2290 | |
a9913044 | 2291 | iucv= [HW,NET] |
1da177e4 | 2292 | |
be3a5b0e | 2293 | ivrs_ioapic [HW,X86-64] |
7d8bfa26 | 2294 | Provide an override to the IOAPIC-ID<->DEVICE-ID |
bbe3a106 SS |
2295 | mapping provided in the IVRS ACPI table. |
2296 | By default, PCI segment is 0, and can be omitted. | |
2297 | For example: | |
2298 | * To map IOAPIC-ID decimal 10 to PCI device 00:14.0 | |
2299 | write the parameter as: | |
7d8bfa26 | 2300 | ivrs_ioapic[10]=00:14.0 |
bbe3a106 SS |
2301 | * To map IOAPIC-ID decimal 10 to PCI segment 0x1 and |
2302 | PCI device 00:14.0 write the parameter as: | |
2303 | ivrs_ioapic[10]=0001:00:14.0 | |
7d8bfa26 | 2304 | |
be3a5b0e | 2305 | ivrs_hpet [HW,X86-64] |
7d8bfa26 | 2306 | Provide an override to the HPET-ID<->DEVICE-ID |
bbe3a106 SS |
2307 | mapping provided in the IVRS ACPI table. |
2308 | By default, PCI segment is 0, and can be omitted. | |
2309 | For example: | |
2310 | * To map HPET-ID decimal 0 to PCI device 00:14.0 | |
2311 | write the parameter as: | |
7d8bfa26 | 2312 | ivrs_hpet[0]=00:14.0 |
bbe3a106 SS |
2313 | * To map HPET-ID decimal 10 to PCI segment 0x1 and |
2314 | PCI device 00:14.0 write the parameter as: | |
2315 | ivrs_ioapic[10]=0001:00:14.0 | |
7d8bfa26 | 2316 | |
be3a5b0e | 2317 | ivrs_acpihid [HW,X86-64] |
ca3bf5d4 | 2318 | Provide an override to the ACPI-HID:UID<->DEVICE-ID |
bbe3a106 SS |
2319 | mapping provided in the IVRS ACPI table. |
2320 | ||
2321 | For example, to map UART-HID:UID AMD0020:0 to | |
2322 | PCI segment 0x1 and PCI device ID 00:14.5, | |
2323 | write the parameter as: | |
2324 | ivrs_acpihid[0001:00:14.5]=AMD0020:0 | |
2325 | ||
2326 | By default, PCI segment is 0, and can be omitted. | |
2327 | For example, PCI device 00:14.5 write the parameter as: | |
ca3bf5d4 SS |
2328 | ivrs_acpihid[00:14.5]=AMD0020:0 |
2329 | ||
1da177e4 | 2330 | js= [HW,JOY] Analog joystick |
1752118d | 2331 | See Documentation/input/joydev/joystick.rst. |
1da177e4 | 2332 | |
65fe935d KC |
2333 | nokaslr [KNL] |
2334 | When CONFIG_RANDOMIZE_BASE is set, this disables | |
2335 | kernel and module base offset ASLR (Address Space | |
2336 | Layout Randomization). | |
24f2e027 | 2337 | |
b0845ce5 MR |
2338 | kasan_multi_shot |
2339 | [KNL] Enforce KASAN (Kernel Address Sanitizer) to print | |
2340 | report on every invalid memory access. Without this | |
2341 | parameter KASAN will print report only for the first | |
2342 | invalid access. | |
2343 | ||
0cb55ad2 RD |
2344 | keepinitrd [HW,ARM] |
2345 | ||
342332e6 | 2346 | kernelcore= [KNL,X86,IA-64,PPC] |
a5c6d650 DR |
2347 | Format: nn[KMGTPE] | nn% | "mirror" |
2348 | This parameter specifies the amount of memory usable by | |
2349 | the kernel for non-movable allocations. The requested | |
2350 | amount is spread evenly throughout all nodes in the | |
2351 | system as ZONE_NORMAL. The remaining memory is used for | |
2352 | movable memory in its own zone, ZONE_MOVABLE. In the | |
2353 | event, a node is too small to have both ZONE_NORMAL and | |
2354 | ZONE_MOVABLE, kernelcore memory will take priority and | |
2355 | other nodes will have a larger ZONE_MOVABLE. | |
2356 | ||
2357 | ZONE_MOVABLE is used for the allocation of pages that | |
2358 | may be reclaimed or moved by the page migration | |
2359 | subsystem. Note that allocations like PTEs-from-HighMem | |
2360 | still use the HighMem zone if it exists, and the Normal | |
ed7ed365 MG |
2361 | zone if it does not. |
2362 | ||
a5c6d650 DR |
2363 | It is possible to specify the exact amount of memory in |
2364 | the form of "nn[KMGTPE]", a percentage of total system | |
2365 | memory in the form of "nn%", or "mirror". If "mirror" | |
342332e6 TI |
2366 | option is specified, mirrored (reliable) memory is used |
2367 | for non-movable allocations and remaining memory is used | |
a5c6d650 DR |
2368 | for Movable pages. "nn[KMGTPE]", "nn%", and "mirror" |
2369 | are exclusive, so you cannot specify multiple forms. | |
ed7ed365 | 2370 | |
4fe1da4e JW |
2371 | kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port. |
2372 | Format: <Controller#>[,poll interval] | |
2373 | The controller # is the number of the ehci usb debug | |
2374 | port as it is probed via PCI. The poll interval is | |
2375 | optional and is the number seconds in between | |
2376 | each poll cycle to the debug port in case you need | |
2377 | the functionality for interrupting the kernel with | |
2378 | gdb or control-c on the dbgp connection. When | |
2379 | not using this parameter you use sysrq-g to break into | |
2380 | the kernel debugger. | |
2381 | ||
84c08fd6 | 2382 | kgdboc= [KGDB,HW] kgdb over consoles. |
ada64e4c JW |
2383 | Requires a tty driver that supports console polling, |
2384 | or a supported polling keyboard driver (non-usb). | |
65b5ac14 JW |
2385 | Serial only format: <serial_device>[,baud] |
2386 | keyboard only format: kbd | |
2387 | keyboard and serial format: kbd,<serial_device>[,baud] | |
2388 | Optional Kernel mode setting: | |
2389 | kms, kbd format: kms,kbd | |
2390 | kms, kbd and serial format: kms,kbd,<ser_dev>[,baud] | |
6cdf6e06 | 2391 | |
f71fc3bc DA |
2392 | kgdboc_earlycon= [KGDB,HW] |
2393 | If the boot console provides the ability to read | |
2394 | characters and can work in polling mode, you can use | |
2395 | this parameter to tell kgdb to use it as a backend | |
2396 | until the normal console is registered. Intended to | |
2397 | be used together with the kgdboc parameter which | |
2398 | specifies the normal console to transition to. | |
2399 | ||
2400 | The name of the early console should be specified | |
2401 | as the value of this parameter. Note that the name of | |
2402 | the early console might be different than the tty | |
2403 | name passed to kgdboc. It's OK to leave the value | |
2404 | blank and the first boot console that implements | |
2405 | read() will be picked. | |
2406 | ||
84c08fd6 JW |
2407 | kgdbwait [KGDB] Stop kernel execution and enter the |
2408 | kernel debugger at the earliest opportunity. | |
2409 | ||
497de97e | 2410 | kmac= [MIPS] Korina ethernet MAC address. |
9bed90c6 FF |
2411 | Configure the RouterBoard 532 series on-chip |
2412 | Ethernet adapter MAC address. | |
2413 | ||
04f70336 CM |
2414 | kmemleak= [KNL] Boot-time kmemleak enable/disable |
2415 | Valid arguments: on, off | |
2416 | Default: on | |
47aeeddc MI |
2417 | Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y, |
2418 | the default is off. | |
04f70336 | 2419 | |
970988e1 MH |
2420 | kprobe_event=[probe-list] |
2421 | [FTRACE] Add kprobe events and enable at boot time. | |
2422 | The probe-list is a semicolon delimited list of probe | |
2423 | definitions. Each definition is same as kprobe_events | |
2424 | interface, but the parameters are comma delimited. | |
2425 | For example, to add a kprobe event on vfs_read with | |
2426 | arg1 and arg2, add to the command line; | |
2427 | ||
2428 | kprobe_event=p,vfs_read,$arg1,$arg2 | |
2429 | ||
2430 | See also Documentation/trace/kprobetrace.rst "Kernel | |
2431 | Boot Parameter" section. | |
2432 | ||
de190555 JL |
2433 | kpti= [ARM64] Control page table isolation of user |
2434 | and kernel address spaces. | |
2435 | Default: enabled on cores which need mitigation. | |
2436 | 0: force disabled | |
2437 | 1: force enabled | |
2438 | ||
fef07aae AP |
2439 | kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs. |
2440 | Default is 0 (don't ignore, but inject #GP) | |
2441 | ||
a3fe5dbd DM |
2442 | kvm.eager_page_split= |
2443 | [KVM,X86] Controls whether or not KVM will try to | |
2444 | proactively split all huge pages during dirty logging. | |
2445 | Eager page splitting reduces interruptions to vCPU | |
2446 | execution by eliminating the write-protection faults | |
2447 | and MMU lock contention that would otherwise be | |
2448 | required to split huge pages lazily. | |
2449 | ||
2450 | VM workloads that rarely perform writes or that write | |
2451 | only to a small region of VM memory may benefit from | |
2452 | disabling eager page splitting to allow huge pages to | |
2453 | still be used for reads. | |
2454 | ||
2455 | The behavior of eager page splitting depends on whether | |
2456 | KVM_DIRTY_LOG_INITIALLY_SET is enabled or disabled. If | |
2457 | disabled, all huge pages in a memslot will be eagerly | |
2458 | split when dirty logging is enabled on that memslot. If | |
cb00a70b DM |
2459 | enabled, eager page splitting will be performed during |
2460 | the KVM_CLEAR_DIRTY ioctl, and only for the pages being | |
2461 | cleared. | |
a3fe5dbd | 2462 | |
ada51a9d | 2463 | Eager page splitting is only supported when kvm.tdp_mmu=Y. |
a3fe5dbd DM |
2464 | |
2465 | Default is Y (on). | |
2466 | ||
c4ae60e4 LA |
2467 | kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface. |
2468 | Default is false (don't support). | |
2469 | ||
b8e8c830 PB |
2470 | kvm.nx_huge_pages= |
2471 | [KVM] Controls the software workaround for the | |
2472 | X86_BUG_ITLB_MULTIHIT bug. | |
2473 | force : Always deploy workaround. | |
2474 | off : Never deploy workaround. | |
2475 | auto : Deploy workaround based on the presence of | |
2476 | X86_BUG_ITLB_MULTIHIT. | |
2477 | ||
2478 | Default is 'auto'. | |
2479 | ||
2480 | If the software workaround is enabled for the host, | |
2481 | guests do need not to enable it for nested guests. | |
2482 | ||
1aa9b957 JS |
2483 | kvm.nx_huge_pages_recovery_ratio= |
2484 | [KVM] Controls how many 4KiB pages are periodically zapped | |
2485 | back to huge pages. 0 disables the recovery, otherwise if | |
2486 | the value is N KVM will zap 1/Nth of the 4KiB pages every | |
4dfe4f40 JS |
2487 | period (see below). The default is 60. |
2488 | ||
2489 | kvm.nx_huge_pages_recovery_period_ms= | |
2490 | [KVM] Controls the time period at which KVM zaps 4KiB pages | |
2491 | back to huge pages. If the value is a non-zero N, KVM will | |
2492 | zap a portion (see ratio above) of the pages every N msecs. | |
2493 | If the value is 0 (the default), KVM will pick a period based | |
2494 | on the ratio, such that a page is zapped after 1 hour on average. | |
1aa9b957 | 2495 | |
fef07aae | 2496 | kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM. |
8475f94a | 2497 | Default is 1 (enabled) |
fef07aae AP |
2498 | |
2499 | kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU) | |
2500 | for all guests. | |
16290246 | 2501 | Default is 1 (enabled) if in 64-bit or 32-bit PAE mode. |
fef07aae | 2502 | |
d8b369c4 DB |
2503 | kvm-arm.mode= |
2504 | [KVM,ARM] Select one of KVM/arm64's modes of operation. | |
2505 | ||
b6a68b97 MZ |
2506 | none: Forcefully disable KVM. |
2507 | ||
1945a067 MZ |
2508 | nvhe: Standard nVHE-based mode, without support for |
2509 | protected guests. | |
2510 | ||
d8b369c4 DB |
2511 | protected: nVHE-based mode with support for guests whose |
2512 | state is kept private from the host. | |
d8b369c4 | 2513 | |
53e8ce13 AE |
2514 | Defaults to VHE/nVHE based on hardware support. Setting |
2515 | mode to "protected" will disable kexec and hibernation | |
2516 | for the host. | |
d8b369c4 | 2517 | |
e23f62f7 MZ |
2518 | kvm-arm.vgic_v3_group0_trap= |
2519 | [KVM,ARM] Trap guest accesses to GICv3 group-0 | |
2520 | system registers | |
2521 | ||
182936ee MZ |
2522 | kvm-arm.vgic_v3_group1_trap= |
2523 | [KVM,ARM] Trap guest accesses to GICv3 group-1 | |
2524 | system registers | |
2525 | ||
ff89511e MZ |
2526 | kvm-arm.vgic_v3_common_trap= |
2527 | [KVM,ARM] Trap guest accesses to GICv3 common | |
2528 | system registers | |
2529 | ||
a7546054 MZ |
2530 | kvm-arm.vgic_v4_enable= |
2531 | [KVM,ARM] Allow use of GICv4 for direct injection of | |
2532 | LPIs. | |
2533 | ||
aed26eeb SR |
2534 | kvm_cma_resv_ratio=n [PPC] |
2535 | Reserves given percentage from system memory area for | |
2536 | contiguous memory allocation for KVM hash pagetable | |
2537 | allocation. | |
2538 | By default it reserves 5% of total system memory. | |
2539 | Format: <integer> | |
2540 | Default: 5 | |
2541 | ||
fef07aae AP |
2542 | kvm-intel.ept= [KVM,Intel] Disable extended page tables |
2543 | (virtualized MMU) support on capable Intel chips. | |
2544 | Default is 1 (enabled) | |
2545 | ||
2546 | kvm-intel.emulate_invalid_guest_state= | |
0ff29701 SC |
2547 | [KVM,Intel] Disable emulation of invalid guest state. |
2548 | Ignored if kvm-intel.enable_unrestricted_guest=1, as | |
2549 | guest state is never invalid for unrestricted guests. | |
2550 | This param doesn't apply to nested guests (L2), as KVM | |
2551 | never emulates invalid L2 guest state. | |
2552 | Default is 1 (enabled) | |
fef07aae AP |
2553 | |
2554 | kvm-intel.flexpriority= | |
2555 | [KVM,Intel] Disable FlexPriority feature (TPR shadow). | |
2556 | Default is 1 (enabled) | |
2557 | ||
e1a72ae2 SL |
2558 | kvm-intel.nested= |
2559 | [KVM,Intel] Enable VMX nesting (nVMX). | |
2560 | Default is 0 (disabled) | |
2561 | ||
fef07aae AP |
2562 | kvm-intel.unrestricted_guest= |
2563 | [KVM,Intel] Disable unrestricted guest feature | |
2564 | (virtualized real and unpaged mode) on capable | |
2565 | Intel chips. Default is 1 (enabled) | |
2566 | ||
a399477e KRW |
2567 | kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault |
2568 | CVE-2018-3620. | |
2569 | ||
2570 | Valid arguments: never, cond, always | |
2571 | ||
2572 | always: L1D cache flush on every VMENTER. | |
2573 | cond: Flush L1D on VMENTER only when the code between | |
2574 | VMEXIT and VMENTER can leak host memory. | |
2575 | never: Disables the mitigation | |
2576 | ||
2577 | Default is cond (do L1 cache flush in specific instances) | |
2578 | ||
fef07aae AP |
2579 | kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification |
2580 | feature (tagged TLBs) on capable Intel chips. | |
2581 | Default is 1 (enabled) | |
2582 | ||
b7fe54f6 BS |
2583 | l1d_flush= [X86,INTEL] |
2584 | Control mitigation for L1D based snooping vulnerability. | |
2585 | ||
2586 | Certain CPUs are vulnerable to an exploit against CPU | |
2587 | internal buffers which can forward information to a | |
2588 | disclosure gadget under certain conditions. | |
2589 | ||
2590 | In vulnerable processors, the speculatively | |
2591 | forwarded data can be used in a cache side channel | |
2592 | attack, to access data to which the attacker does | |
2593 | not have direct access. | |
2594 | ||
2595 | This parameter controls the mitigation. The | |
2596 | options are: | |
2597 | ||
2598 | on - enable the interface for the mitigation | |
2599 | ||
d90a7a0e JK |
2600 | l1tf= [X86] Control mitigation of the L1TF vulnerability on |
2601 | affected CPUs | |
2602 | ||
2603 | The kernel PTE inversion protection is unconditionally | |
2604 | enabled and cannot be disabled. | |
2605 | ||
2606 | full | |
2607 | Provides all available mitigations for the | |
2608 | L1TF vulnerability. Disables SMT and | |
2609 | enables all mitigations in the | |
2610 | hypervisors, i.e. unconditional L1D flush. | |
2611 | ||
2612 | SMT control and L1D flush control via the | |
2613 | sysfs interface is still possible after | |
2614 | boot. Hypervisors will issue a warning | |
2615 | when the first VM is started in a | |
2616 | potentially insecure configuration, | |
2617 | i.e. SMT enabled or L1D flush disabled. | |
2618 | ||
2619 | full,force | |
2620 | Same as 'full', but disables SMT and L1D | |
2621 | flush runtime control. Implies the | |
2622 | 'nosmt=force' command line option. | |
2623 | (i.e. sysfs control of SMT is disabled.) | |
2624 | ||
2625 | flush | |
2626 | Leaves SMT enabled and enables the default | |
2627 | hypervisor mitigation, i.e. conditional | |
2628 | L1D flush. | |
2629 | ||
2630 | SMT control and L1D flush control via the | |
2631 | sysfs interface is still possible after | |
2632 | boot. Hypervisors will issue a warning | |
2633 | when the first VM is started in a | |
2634 | potentially insecure configuration, | |
2635 | i.e. SMT enabled or L1D flush disabled. | |
2636 | ||
2637 | flush,nosmt | |
2638 | ||
2639 | Disables SMT and enables the default | |
2640 | hypervisor mitigation. | |
2641 | ||
2642 | SMT control and L1D flush control via the | |
2643 | sysfs interface is still possible after | |
2644 | boot. Hypervisors will issue a warning | |
2645 | when the first VM is started in a | |
2646 | potentially insecure configuration, | |
2647 | i.e. SMT enabled or L1D flush disabled. | |
2648 | ||
2649 | flush,nowarn | |
2650 | Same as 'flush', but hypervisors will not | |
2651 | warn when a VM is started in a potentially | |
2652 | insecure configuration. | |
2653 | ||
2654 | off | |
2655 | Disables hypervisor mitigations and doesn't | |
2656 | emit any warnings. | |
5b5e4d62 MH |
2657 | It also drops the swap size and available |
2658 | RAM limit restriction on both hypervisor and | |
2659 | bare metal. | |
d90a7a0e JK |
2660 | |
2661 | Default is 'flush'. | |
2662 | ||
65fd4cb6 | 2663 | For details see: Documentation/admin-guide/hw-vuln/l1tf.rst |
d90a7a0e | 2664 | |
1da177e4 LT |
2665 | l2cr= [PPC] |
2666 | ||
a78bfbfc RB |
2667 | l3cr= [PPC] |
2668 | ||
cd4f0ef7 | 2669 | lapic [X86-32,APIC] Enable the local APIC even if BIOS |
a9913044 | 2670 | disabled it. |
1da177e4 | 2671 | |
622381e6 | 2672 | lapic= [X86,APIC] Do not use TSC deadline |
279f1461 SS |
2673 | value for LAPIC timer one-shot implementation. Default |
2674 | back to the programmable timer unit in the LAPIC. | |
622381e6 | 2675 | Format: notscdeadline |
279f1461 | 2676 | |
6cececfc | 2677 | lapic_timer_c2_ok [X86,APIC] trust the local apic timer |
ada9cfdd | 2678 | in C2 power state. |
e585bef8 | 2679 | |
fcb71f6f FC |
2680 | libata.dma= [LIBATA] DMA control |
2681 | libata.dma=0 Disable all PATA and SATA DMA | |
2682 | libata.dma=1 PATA and SATA Disk DMA only | |
2683 | libata.dma=2 ATAPI (CDROM) DMA only | |
16290246 | 2684 | libata.dma=4 Compact Flash DMA only |
fcb71f6f FC |
2685 | Combinations also work, so libata.dma=3 enables DMA |
2686 | for disks and CDROMs, but not CFs. | |
16290246 | 2687 | |
20308871 MP |
2688 | libata.ignore_hpa= [LIBATA] Ignore HPA limit |
2689 | libata.ignore_hpa=0 keep BIOS limits (default) | |
2690 | libata.ignore_hpa=1 ignore limits, using full disk | |
fcb71f6f | 2691 | |
78e70c23 DJ |
2692 | libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume |
2693 | when set. | |
2694 | Format: <int> | |
2695 | ||
fa82cabb DLM |
2696 | libata.force= [LIBATA] Force configurations. The format is a comma- |
2697 | separated list of "[ID:]VAL" where ID is PORT[.DEVICE]. | |
2698 | PORT and DEVICE are decimal numbers matching port, link | |
2699 | or device. Basically, it matches the ATA ID string | |
2700 | printed on console by libata. If the whole ID part is | |
2701 | omitted, the last PORT and DEVICE values are used. If | |
2702 | ID hasn't been specified yet, the configuration applies | |
2703 | to all ports, links and devices. | |
33267325 TH |
2704 | |
2705 | If only DEVICE is omitted, the parameter applies to | |
2706 | the port and all links and devices behind it. DEVICE | |
2707 | number of 0 either selects the first device or the | |
2708 | first fan-out link behind PMP device. It does not | |
2709 | select the host link. DEVICE number of 15 selects the | |
2710 | host link and device attached to it. | |
2711 | ||
2712 | The VAL specifies the configuration to force. As long | |
fa82cabb | 2713 | as there is no ambiguity, shortcut notation is allowed. |
33267325 TH |
2714 | For example, both 1.5 and 1.5G would work for 1.5Gbps. |
2715 | The following configurations can be forced. | |
2716 | ||
2717 | * Cable type: 40c, 80c, short40c, unk, ign or sata. | |
2718 | Any ID with matching PORT is used. | |
2719 | ||
2720 | * SATA link speed limit: 1.5Gbps or 3.0Gbps. | |
2721 | ||
2722 | * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7]. | |
2723 | udma[/][16,25,33,44,66,100,133] notation is also | |
2724 | allowed. | |
2725 | ||
fa82cabb DLM |
2726 | * nohrst, nosrst, norst: suppress hard, soft and both |
2727 | resets. | |
2728 | ||
2729 | * rstonce: only attempt one reset during hot-unplug | |
2730 | link recovery. | |
2731 | ||
2732 | * [no]dbdelay: Enable or disable the extra 200ms delay | |
2733 | before debouncing a link PHY and device presence | |
2734 | detection. | |
2735 | ||
33267325 TH |
2736 | * [no]ncq: Turn on or off NCQ. |
2737 | ||
fa82cabb DLM |
2738 | * [no]ncqtrim: Enable or disable queued DSM TRIM. |
2739 | ||
2740 | * [no]ncqati: Enable or disable NCQ trim on ATI chipset. | |
2741 | ||
2742 | * [no]trim: Enable or disable (unqueued) TRIM. | |
2743 | ||
2744 | * trim_zero: Indicate that TRIM command zeroes data. | |
2745 | ||
2746 | * max_trim_128m: Set 128M maximum trim size limit. | |
2747 | ||
2748 | * [no]dma: Turn on or off DMA transfers. | |
2749 | ||
2750 | * atapi_dmadir: Enable ATAPI DMADIR bridge support. | |
2751 | ||
2752 | * atapi_mod16_dma: Enable the use of ATAPI DMA for | |
2753 | commands that are not a multiple of 16 bytes. | |
2754 | ||
2755 | * [no]dmalog: Enable or disable the use of the | |
2756 | READ LOG DMA EXT command to access logs. | |
2757 | ||
2758 | * [no]iddevlog: Enable or disable access to the | |
2759 | identify device data log. | |
2760 | ||
2761 | * [no]logdir: Enable or disable access to the general | |
2762 | purpose log directory. | |
2763 | ||
2764 | * max_sec_128: Set transfer size limit to 128 sectors. | |
2765 | ||
2766 | * max_sec_1024: Set or clear transfer size limit to | |
2767 | 1024 sectors. | |
d7b16e4f | 2768 | |
fa82cabb DLM |
2769 | * max_sec_lba48: Set or clear transfer size limit to |
2770 | 65535 sectors. | |
05944bdf | 2771 | |
fa82cabb | 2772 | * [no]lpm: Enable or disable link power management. |
ca6d43b0 | 2773 | |
fa82cabb DLM |
2774 | * [no]setxfer: Indicate if transfer speed mode setting |
2775 | should be skipped. | |
43c9c591 | 2776 | |
fa82cabb | 2777 | * dump_id: Dump IDENTIFY data. |
966fbe19 | 2778 | |
b8bd6dc3 RJ |
2779 | * disable: Disable this device. |
2780 | ||
33267325 TH |
2781 | If there are multiple matching configurations changing |
2782 | the same attribute, the last one is used. | |
2783 | ||
6b99e6e6 | 2784 | load_ramdisk= [RAM] [Deprecated] |
1da177e4 | 2785 | |
a6b25b67 RD |
2786 | lockd.nlm_grace_period=P [NFS] Assign grace period. |
2787 | Format: <integer> | |
1da177e4 | 2788 | |
a6b25b67 RD |
2789 | lockd.nlm_tcpport=N [NFS] Assign TCP port. |
2790 | Format: <integer> | |
2791 | ||
2792 | lockd.nlm_timeout=T [NFS] Assign timeout value. | |
2793 | Format: <integer> | |
2794 | ||
2795 | lockd.nlm_udpport=M [NFS] Assign UDP port. | |
2796 | Format: <integer> | |
1da177e4 | 2797 | |
000d388e MG |
2798 | lockdown= [SECURITY] |
2799 | { integrity | confidentiality } | |
2800 | Enable the kernel lockdown feature. If set to | |
2801 | integrity, kernel features that allow userland to | |
2802 | modify the running kernel are disabled. If set to | |
2803 | confidentiality, kernel features that allow userland | |
2804 | to extract confidential information from the kernel | |
2805 | are also disabled. | |
2806 | ||
ec4518aa PM |
2807 | locktorture.nreaders_stress= [KNL] |
2808 | Set the number of locking read-acquisition kthreads. | |
2809 | Defaults to being automatically set based on the | |
2810 | number of online CPUs. | |
2811 | ||
2812 | locktorture.nwriters_stress= [KNL] | |
2813 | Set the number of locking write-acquisition kthreads. | |
2814 | ||
2815 | locktorture.onoff_holdoff= [KNL] | |
2816 | Set time (s) after boot for CPU-hotplug testing. | |
2817 | ||
2818 | locktorture.onoff_interval= [KNL] | |
2819 | Set time (s) between CPU-hotplug operations, or | |
2820 | zero to disable CPU-hotplug testing. | |
2821 | ||
2822 | locktorture.shuffle_interval= [KNL] | |
2823 | Set task-shuffle interval (jiffies). Shuffling | |
2824 | tasks allows some CPUs to go into dyntick-idle | |
2825 | mode during the locktorture test. | |
2826 | ||
2827 | locktorture.shutdown_secs= [KNL] | |
2828 | Set time (s) after boot system shutdown. This | |
2829 | is useful for hands-off automated testing. | |
2830 | ||
2831 | locktorture.stat_interval= [KNL] | |
2832 | Time (s) between statistics printk()s. | |
2833 | ||
2834 | locktorture.stutter= [KNL] | |
2835 | Time (s) to stutter testing, for example, | |
2836 | specifying five seconds causes the test to run for | |
2837 | five seconds, wait for five seconds, and so on. | |
2838 | This tests the locking primitive's ability to | |
2839 | transition abruptly to and from idle. | |
2840 | ||
ec4518aa PM |
2841 | locktorture.torture_type= [KNL] |
2842 | Specify the locking implementation to test. | |
2843 | ||
2844 | locktorture.verbose= [KNL] | |
2845 | Enable additional printk() statements. | |
2846 | ||
1da177e4 LT |
2847 | logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver |
2848 | Format: <irq> | |
2849 | ||
2850 | loglevel= All Kernel Messages with a loglevel smaller than the | |
2851 | console loglevel will be printed to the console. It can | |
2852 | also be changed with klogd or other programs. The | |
2853 | loglevels are defined as follows: | |
2854 | ||
2855 | 0 (KERN_EMERG) system is unusable | |
2856 | 1 (KERN_ALERT) action must be taken immediately | |
2857 | 2 (KERN_CRIT) critical conditions | |
2858 | 3 (KERN_ERR) error conditions | |
2859 | 4 (KERN_WARNING) warning conditions | |
2860 | 5 (KERN_NOTICE) normal but significant condition | |
2861 | 6 (KERN_INFO) informational | |
2862 | 7 (KERN_DEBUG) debug-level messages | |
2863 | ||
c756d08a | 2864 | log_buf_len=n[KMG] Sets the size of the printk ring buffer, |
23b2899f LR |
2865 | in bytes. n must be a power of two and greater |
2866 | than the minimal size. The minimal size is defined | |
2867 | by LOG_BUF_SHIFT kernel config parameter. There is | |
2868 | also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter | |
2869 | that allows to increase the default size depending on | |
2870 | the number of CPUs. See init/Kconfig for more details. | |
1da177e4 | 2871 | |
accaa24c RD |
2872 | logo.nologo [FB] Disables display of the built-in Linux logo. |
2873 | This may be used to provide more screen space for | |
2874 | kernel log messages and is useful when debugging | |
2875 | kernel boot problems. | |
2876 | ||
1da177e4 LT |
2877 | lp=0 [LP] Specify parallel ports to use, e.g, |
2878 | lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses | |
2879 | lp=reset first parallel port). 'lp=0' disables the | |
2880 | lp=auto printer driver. 'lp=reset' (which can be | |
2881 | specified in addition to the ports) causes | |
2882 | attached printers to be reset. Using | |
2883 | lp=port1,port2,... specifies the parallel ports | |
2884 | to associate lp devices with, starting with | |
2885 | lp0. A port specification may be 'none' to skip | |
2886 | that lp device, or a parport name such as | |
2887 | 'parport0'. Specifying 'lp=auto' instead of a | |
2888 | port specification list means that device IDs | |
2889 | from each port should be examined, to see if | |
2890 | an IEEE 1284-compliant printer is attached; if | |
2891 | so, the driver will manage that printer. | |
2892 | See also header of drivers/char/lp.c. | |
2893 | ||
2894 | lpj=n [KNL] | |
2895 | Sets loops_per_jiffy to given constant, thus avoiding | |
2896 | time-consuming boot-time autodetection (up to 250 ms per | |
2897 | CPU). 0 enables autodetection (default). To determine | |
2898 | the correct value for your kernel, boot with normal | |
2899 | autodetection and see what value is printed. Note that | |
2900 | on SMP systems the preset will be applied to all CPUs, | |
2901 | which is likely to cause problems if your CPUs need | |
2902 | significantly divergent settings. An incorrect value | |
2903 | will cause delays in the kernel to be wrong, leading to | |
2904 | unpredictable I/O errors and other breakage. Although | |
2905 | unlikely, in the extreme case this might damage your | |
2906 | hardware. | |
2907 | ||
2908 | ltpc= [NET] | |
2909 | Format: <io>,<irq>,<dma> | |
2910 | ||
9b8c7c14 KC |
2911 | lsm.debug [SECURITY] Enable LSM initialization debugging output. |
2912 | ||
79f7865d KC |
2913 | lsm=lsm1,...,lsmN |
2914 | [SECURITY] Choose order of LSM initialization. This | |
89a9684e | 2915 | overrides CONFIG_LSM, and the "security=" parameter. |
79f7865d | 2916 | |
16290246 | 2917 | machvec= [IA-64] Force the use of a particular machine-vector |
a9913044 | 2918 | (machvec) in a generic kernel. |
df43acac | 2919 | Example: machvec=hpzx1 |
1da177e4 | 2920 | |
42769488 RD |
2921 | machtype= [Loongson] Share the same kernel image file between |
2922 | different yeeloong laptops. | |
3209e70e WZ |
2923 | Example: machtype=lemote-yeeloong-2f-7inch |
2924 | ||
59bdbbd5 | 2925 | max_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory greater |
0cb55ad2 | 2926 | than or equal to this physical address is ignored. |
1da177e4 LT |
2927 | |
2928 | maxcpus= [SMP] Maximum number of processors that an SMP kernel | |
7c142bfe BH |
2929 | will bring up during bootup. maxcpus=n : n >= 0 limits |
2930 | the kernel to bring up 'n' processors. Surely after | |
2931 | bootup you can bring up the other plugged cpu by executing | |
2932 | "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus | |
2933 | only takes effect during system bootup. | |
2934 | While n=0 is a special case, it is equivalent to "nosmp", | |
2935 | which also disables the IO APIC. | |
1da177e4 | 2936 | |
d134b00b KS |
2937 | max_loop= [LOOP] The number of loop block devices that get |
2938 | (loop.max_loop) unconditionally pre-created at init time. The default | |
2939 | number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead | |
2940 | of statically allocating a predefined number, loop | |
2941 | devices can be requested on-demand with the | |
2942 | /dev/loop-control interface. | |
2b2c3750 | 2943 | |
cd4f0ef7 | 2944 | mce [X86-32] Machine Check Exception |
1da177e4 | 2945 | |
cb1aaebe | 2946 | mce=option [X86-64] See Documentation/x86/x86_64/boot-options.rst |
909dd324 | 2947 | |
1da177e4 | 2948 | md= [HW] RAID subsystems devices and level |
e52347bd | 2949 | See Documentation/admin-guide/md.rst. |
a9913044 | 2950 | |
1da177e4 LT |
2951 | mdacon= [MDA] |
2952 | Format: <first>,<last> | |
2953 | Specifies range of consoles to be captured by the MDA. | |
a9913044 | 2954 | |
bc124170 TG |
2955 | mds= [X86,INTEL] |
2956 | Control mitigation for the Micro-architectural Data | |
2957 | Sampling (MDS) vulnerability. | |
2958 | ||
2959 | Certain CPUs are vulnerable to an exploit against CPU | |
2960 | internal buffers which can forward information to a | |
2961 | disclosure gadget under certain conditions. | |
2962 | ||
2963 | In vulnerable processors, the speculatively | |
2964 | forwarded data can be used in a cache side channel | |
2965 | attack, to access data to which the attacker does | |
2966 | not have direct access. | |
2967 | ||
2968 | This parameter controls the MDS mitigation. The | |
2969 | options are: | |
2970 | ||
d71eb0ce JP |
2971 | full - Enable MDS mitigation on vulnerable CPUs |
2972 | full,nosmt - Enable MDS mitigation and disable | |
2973 | SMT on vulnerable CPUs | |
2974 | off - Unconditionally disable MDS mitigation | |
bc124170 | 2975 | |
64870ed1 WL |
2976 | On TAA-affected machines, mds=off can be prevented by |
2977 | an active TAA mitigation as both vulnerabilities are | |
2978 | mitigated with the same mechanism so in order to disable | |
2979 | this mitigation, you need to specify tsx_async_abort=off | |
2980 | too. | |
2981 | ||
bc124170 TG |
2982 | Not specifying this option is equivalent to |
2983 | mds=full. | |
2984 | ||
5999bbe7 TG |
2985 | For details see: Documentation/admin-guide/hw-vuln/mds.rst |
2986 | ||
75c05fab MR |
2987 | mem=nn[KMG] [HEXAGON] Set the memory size. |
2988 | Must be specified, otherwise memory size will be 0. | |
2989 | ||
1da177e4 | 2990 | mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory |
f3cd4c86 BH |
2991 | Amount of memory to be used in cases as follows: |
2992 | ||
2993 | 1 for test; | |
2994 | 2 when the kernel is not able to see the whole system memory; | |
2995 | 3 memory that lies after 'mem=' boundary is excluded from | |
2996 | the hypervisor, then assigned to KVM guests. | |
75c05fab MR |
2997 | 4 to limit the memory available for kdump kernel. |
2998 | ||
2999 | [ARC,MICROBLAZE] - the limit applies only to low memory, | |
3000 | high memory is not affected. | |
3001 | ||
3002 | [ARM64] - only limits memory covered by the linear | |
3003 | mapping. The NOMAP regions are not affected. | |
f3cd4c86 | 3004 | |
fbb97d87 WC |
3005 | [X86] Work as limiting max address. Use together |
3006 | with memmap= to avoid physical address space collisions. | |
3007 | Without memmap= PCI devices could be placed at addresses | |
3008 | belonging to unused RAM. | |
1da177e4 | 3009 | |
f3cd4c86 BH |
3010 | Note that this only takes effects during boot time since |
3011 | in above case 3, memory may need be hot added after boot | |
3012 | if system memory of hypervisor is not sufficient. | |
3013 | ||
75c05fab MR |
3014 | mem=nn[KMG]@ss[KMG] |
3015 | [ARM,MIPS] - override the memory layout reported by | |
3016 | firmware. | |
3017 | Define a memory region of size nn[KMG] starting at | |
3018 | ss[KMG]. | |
3019 | Multiple different regions can be specified with | |
3020 | multiple mem= parameters on the command line. | |
3021 | ||
cd4f0ef7 | 3022 | mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel |
1da177e4 LT |
3023 | memory. |
3024 | ||
389cfd96 RD |
3025 | memblock=debug [KNL] Enable memblock debug messages. |
3026 | ||
6902aa84 PM |
3027 | memchunk=nn[KMG] |
3028 | [KNL,SH] Allow user to override the default size for | |
3029 | per-device physically contiguous DMA buffers. | |
3030 | ||
6dddd7a7 | 3031 | memhp_default_state=online/offline |
86dd995d VK |
3032 | [KNL] Set the initial state for the memory hotplug |
3033 | onlining policy. If not specified, the default value is | |
3034 | set according to the | |
3035 | CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config | |
3036 | option. | |
cb1aaebe | 3037 | See Documentation/admin-guide/mm/memory-hotplug.rst. |
86dd995d | 3038 | |
6cececfc | 3039 | memmap=exactmap [KNL,X86] Enable setting of an exact |
1da177e4 LT |
3040 | E820 memory map, as specified by the user. |
3041 | Such memmap=exactmap lines can be constructed based on | |
3042 | BIOS output or other requirements. See the memmap=nn@ss | |
3043 | option description. | |
3044 | ||
3045 | memmap=nn[KMG]@ss[KMG] | |
4c8e3de4 | 3046 | [KNL, X86, MIPS, XTENSA] Force usage of a specific region of memory. |
277cba1d | 3047 | Region of memory to be used is from ss to ss+nn. |
8fcc9bc3 BH |
3048 | If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG], |
3049 | which limits max address to nn[KMG]. | |
3050 | Multiple different regions can be specified, | |
3051 | comma delimited. | |
3052 | Example: | |
3053 | memmap=100M@2G,100M#3G,1G!1024G | |
1da177e4 LT |
3054 | |
3055 | memmap=nn[KMG]#ss[KMG] | |
3056 | [KNL,ACPI] Mark specific memory as ACPI data. | |
277cba1d | 3057 | Region of memory to be marked is from ss to ss+nn. |
1da177e4 LT |
3058 | |
3059 | memmap=nn[KMG]$ss[KMG] | |
3060 | [KNL,ACPI] Mark specific memory as reserved. | |
277cba1d | 3061 | Region of memory to be reserved is from ss to ss+nn. |
1312848e PM |
3062 | Example: Exclude memory from 0x18690000-0x1869ffff |
3063 | memmap=64K$0x18690000 | |
3064 | or | |
3065 | memmap=0x10000$0x18690000 | |
8fcc9bc3 BH |
3066 | Some bootloaders may need an escape character before '$', |
3067 | like Grub2, otherwise '$' and the following number | |
3068 | will be eaten. | |
1da177e4 | 3069 | |
ec776ef6 CH |
3070 | memmap=nn[KMG]!ss[KMG] |
3071 | [KNL,X86] Mark specific memory as protected. | |
3072 | Region of memory to be used, from ss to ss+nn. | |
3073 | The memory region may be marked as e820 type 12 (0xc) | |
3074 | and is NVDIMM or ADR memory. | |
3075 | ||
ef61f8a3 JS |
3076 | memmap=<size>%<offset>-<oldtype>+<newtype> |
3077 | [KNL,ACPI] Convert memory within the specified region | |
3078 | from <oldtype> to <newtype>. If "-<oldtype>" is left | |
3079 | out, the whole region will be marked as <newtype>, | |
3080 | even if previously unavailable. If "+<newtype>" is left | |
3081 | out, matching memory will be removed. Types are | |
3082 | specified as e820 types, e.g., 1 = RAM, 2 = reserved, | |
3083 | 3 = ACPI, 12 = PRAM. | |
3084 | ||
9f077871 JF |
3085 | memory_corruption_check=0/1 [X86] |
3086 | Some BIOSes seem to corrupt the first 64k of | |
3087 | memory when doing things like suspend/resume. | |
3088 | Setting this option will scan the memory | |
3089 | looking for corruption. Enabling this will | |
3090 | both detect corruption and prevent the kernel | |
3091 | from using the memory being corrupted. | |
3092 | However, its intended as a diagnostic tool; if | |
3093 | repeatable BIOS-originated corruption always | |
3094 | affects the same memory, you can use memmap= | |
3095 | to prevent the kernel from using that memory. | |
3096 | ||
3097 | memory_corruption_check_size=size [X86] | |
3098 | By default it checks for corruption in the low | |
3099 | 64k, making this memory unavailable for normal | |
3100 | use. Use this parameter to scan for | |
3101 | corruption in more or less memory. | |
3102 | ||
3103 | memory_corruption_check_period=seconds [X86] | |
3104 | By default it checks for corruption every 60 | |
3105 | seconds. Use this parameter to check at some | |
3106 | other rate. 0 disables periodic checking. | |
3107 | ||
e3a9d9fc OS |
3108 | memory_hotplug.memmap_on_memory |
3109 | [KNL,X86,ARM] Boolean flag to enable this feature. | |
3110 | Format: {on | off (default)} | |
3111 | When enabled, runtime hotplugged memory will | |
66361095 MS |
3112 | allocate its internal metadata (struct pages, |
3113 | those vmemmap pages cannot be optimized even | |
3114 | if hugetlb_free_vmemmap is enabled) from the | |
3115 | hotadded memory which will allow to hotadd a | |
3116 | lot of memory without requiring additional | |
3117 | memory to do so. | |
e3a9d9fc OS |
3118 | This feature is disabled by default because it |
3119 | has some implication on large (e.g. GB) | |
3120 | allocations in some configurations (e.g. small | |
3121 | memory blocks). | |
3122 | The state of the flag can be read in | |
3123 | /sys/module/memory_hotplug/parameters/memmap_on_memory. | |
3124 | Note that even when enabled, there are a few cases where | |
3125 | the feature is not effective. | |
3126 | ||
376e3fde | 3127 | memtest= [KNL,X86,ARM,M68K,PPC,RISCV] Enable memtest |
c64df707 | 3128 | Format: <integer> |
c64df707 | 3129 | default : 0 <disable> |
9e5f6cf5 AH |
3130 | Specifies the number of memtest passes to be |
3131 | performed. Each pass selects another test | |
3132 | pattern from a given set of patterns. Memtest | |
3133 | fills the memory with this pattern, validates | |
3134 | memory contents and reserves bad memory | |
3135 | regions that are detected. | |
c64df707 | 3136 | |
c262f3b9 TL |
3137 | mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control |
3138 | Valid arguments: on, off | |
3139 | Default (depends on kernel configuration option): | |
3140 | on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y) | |
3141 | off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n) | |
3142 | mem_encrypt=on: Activate SME | |
3143 | mem_encrypt=off: Do not activate SME | |
3144 | ||
7ac3945d | 3145 | Refer to Documentation/virt/kvm/x86/amd-memory-encryption.rst |
c262f3b9 TL |
3146 | for details on when memory encryption can be activated. |
3147 | ||
406e7938 RW |
3148 | mem_sleep_default= [SUSPEND] Default system suspend mode: |
3149 | s2idle - Suspend-To-Idle | |
3150 | shallow - Power-On Suspend or equivalent (if supported) | |
3151 | deep - Suspend-To-RAM or equivalent (if supported) | |
58e7cb9e | 3152 | See Documentation/admin-guide/pm/sleep-states.rst. |
406e7938 | 3153 | |
1da177e4 | 3154 | meye.*= [HW] Set MotionEye Camera parameters |
32e2eae2 | 3155 | See Documentation/admin-guide/media/meye.rst. |
1da177e4 | 3156 | |
8f36881b AS |
3157 | mfgpt_irq= [IA-32] Specify the IRQ to use for the |
3158 | Multi-Function General Purpose Timers on AMD Geode | |
3159 | platforms. | |
3160 | ||
e6c4dc6c WT |
3161 | mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when |
3162 | the BIOS has incorrectly applied a workaround. TinyBIOS | |
3163 | version 0.98 is known to be affected, 0.99 fixes the | |
3164 | problem by letting the user disable the workaround. | |
3165 | ||
1da177e4 LT |
3166 | mga= [HW,DRM] |
3167 | ||
59bdbbd5 | 3168 | min_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory below this |
1c207f95 RD |
3169 | physical address is ignored. |
3170 | ||
39f45d7b MP |
3171 | mini2440= [ARM,HW,KNL] |
3172 | Format:[0..2][b][c][t] | |
3173 | Default: "0tb" | |
3174 | MINI2440 configuration specification: | |
3175 | 0 - The attached screen is the 3.5" TFT | |
3176 | 1 - The attached screen is the 7" TFT | |
3177 | 2 - The VGA Shield is attached (1024x768) | |
3178 | Leaving out the screen size parameter will not load | |
3179 | the TFT driver, and the framebuffer will be left | |
3180 | unconfigured. | |
3181 | b - Enable backlight. The TFT backlight pin will be | |
3182 | linked to the kernel VESA blanking code and a GPIO | |
3183 | LED. This parameter is not necessary when using the | |
3184 | VGA shield. | |
3185 | c - Enable the s3c camera interface. | |
3186 | t - Reserved for enabling touchscreen support. The | |
3187 | touchscreen support is not enabled in the mainstream | |
3188 | kernel as of 2.6.30, a preliminary port can be found | |
3189 | in the "bleeding edge" mini2440 support kernel at | |
6b2484e1 | 3190 | https://repo.or.cz/w/linux-2.6/mini2440.git |
39f45d7b | 3191 | |
98af8452 | 3192 | mitigations= |
a111b7c0 JP |
3193 | [X86,PPC,S390,ARM64] Control optional mitigations for |
3194 | CPU vulnerabilities. This is a set of curated, | |
d68be4c4 JP |
3195 | arch-independent options, each of which is an |
3196 | aggregation of existing arch-specific options. | |
98af8452 JP |
3197 | |
3198 | off | |
3199 | Disable all optional CPU mitigations. This | |
3200 | improves system performance, but it may also | |
3201 | expose users to several CPU vulnerabilities. | |
782e69ef | 3202 | Equivalent to: nopti [X86,PPC] |
e92b2573 | 3203 | if nokaslr then kpti=0 [ARM64] |
a2059825 | 3204 | nospectre_v1 [X86,PPC] |
0336e04a | 3205 | nobp=0 [S390] |
a111b7c0 | 3206 | nospectre_v2 [X86,PPC,S390,ARM64] |
d68be4c4 | 3207 | spectre_v2_user=off [X86] |
782e69ef | 3208 | spec_store_bypass_disable=off [X86,PPC] |
a111b7c0 | 3209 | ssbd=force-off [ARM64] |
d68be4c4 | 3210 | l1tf=off [X86] |
5c14068f | 3211 | mds=off [X86] |
a7a248c5 | 3212 | tsx_async_abort=off [X86] |
b8e8c830 | 3213 | kvm.nx_huge_pages=off [X86] |
553b0cb3 | 3214 | srbds=off [X86,INTEL] |
f7964378 | 3215 | no_entry_flush [PPC] |
9a32a7e7 | 3216 | no_uaccess_flush [PPC] |
8cb861e9 | 3217 | mmio_stale_data=off [X86] |
ea304a8b | 3218 | retbleed=off [X86] |
b8e8c830 PB |
3219 | |
3220 | Exceptions: | |
3221 | This does not have any effect on | |
3222 | kvm.nx_huge_pages when | |
3223 | kvm.nx_huge_pages=force. | |
98af8452 JP |
3224 | |
3225 | auto (default) | |
3226 | Mitigate all CPU vulnerabilities, but leave SMT | |
3227 | enabled, even if it's vulnerable. This is for | |
3228 | users who don't want to be surprised by SMT | |
3229 | getting disabled across kernel upgrades, or who | |
3230 | have other ways of avoiding SMT-based attacks. | |
d68be4c4 | 3231 | Equivalent to: (default behavior) |
98af8452 JP |
3232 | |
3233 | auto,nosmt | |
3234 | Mitigate all CPU vulnerabilities, disabling SMT | |
3235 | if needed. This is for users who always want to | |
3236 | be fully mitigated, even if it means losing SMT. | |
d68be4c4 | 3237 | Equivalent to: l1tf=flush,nosmt [X86] |
5c14068f | 3238 | mds=full,nosmt [X86] |
a7a248c5 | 3239 | tsx_async_abort=full,nosmt [X86] |
8cb861e9 | 3240 | mmio_stale_data=full,nosmt [X86] |
ea304a8b | 3241 | retbleed=auto,nosmt [X86] |
98af8452 | 3242 | |
6b74ab97 MG |
3243 | mminit_loglevel= |
3244 | [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this | |
3245 | parameter allows control of the logging verbosity for | |
3246 | the additional memory initialisation checks. A value | |
3247 | of 0 disables mminit logging and a level of 4 will | |
3248 | log everything. Information is printed at KERN_DEBUG | |
3249 | so loglevel=8 may also need to be specified. | |
3250 | ||
8cb861e9 PG |
3251 | mmio_stale_data= |
3252 | [X86,INTEL] Control mitigation for the Processor | |
3253 | MMIO Stale Data vulnerabilities. | |
3254 | ||
3255 | Processor MMIO Stale Data is a class of | |
3256 | vulnerabilities that may expose data after an MMIO | |
3257 | operation. Exposed data could originate or end in | |
3258 | the same CPU buffers as affected by MDS and TAA. | |
3259 | Therefore, similar to MDS and TAA, the mitigation | |
3260 | is to clear the affected CPU buffers. | |
3261 | ||
3262 | This parameter controls the mitigation. The | |
3263 | options are: | |
3264 | ||
3265 | full - Enable mitigation on vulnerable CPUs | |
3266 | ||
3267 | full,nosmt - Enable mitigation and disable SMT on | |
3268 | vulnerable CPUs. | |
3269 | ||
3270 | off - Unconditionally disable mitigation | |
3271 | ||
3272 | On MDS or TAA affected machines, | |
3273 | mmio_stale_data=off can be prevented by an active | |
3274 | MDS or TAA mitigation as these vulnerabilities are | |
3275 | mitigated with the same mechanism so in order to | |
3276 | disable this mitigation, you need to specify | |
3277 | mds=off and tsx_async_abort=off too. | |
3278 | ||
3279 | Not specifying this option is equivalent to | |
3280 | mmio_stale_data=full. | |
3281 | ||
3282 | For details see: | |
3283 | Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst | |
3284 | ||
ae39e9ed SK |
3285 | module.async_probe=<bool> |
3286 | [KNL] When set to true, modules will use async probing | |
3287 | by default. To enable/disable async probing for a | |
3288 | specific module, use the module specific control that | |
3289 | is documented under <module>.async_probe. When both | |
3290 | module.async_probe and <module>.async_probe are | |
3291 | specified, <module>.async_probe takes precedence for | |
3292 | the specific module. | |
3293 | ||
106a4ee2 RR |
3294 | module.sig_enforce |
3295 | [KNL] When CONFIG_MODULE_SIG is set, this means that | |
3296 | modules without (valid) signatures will fail to load. | |
2a039be7 | 3297 | Note that if CONFIG_MODULE_SIG_FORCE is set, that |
106a4ee2 RR |
3298 | is always true, so this option does nothing. |
3299 | ||
be7de5f9 PB |
3300 | module_blacklist= [KNL] Do not load a comma-separated list of |
3301 | modules. Useful for debugging problem modules. | |
3302 | ||
1da177e4 LT |
3303 | mousedev.tap_time= |
3304 | [MOUSE] Maximum time between finger touching and | |
3305 | leaving touchpad surface for touch to be considered | |
3306 | a tap and be reported as a left button click (for | |
3307 | touchpads working in absolute mode only). | |
3308 | Format: <msecs> | |
3309 | mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices | |
3310 | reporting absolute coordinates, such as tablets | |
3311 | mousedev.yres= [MOUSE] Vertical screen resolution, used for devices | |
3312 | reporting absolute coordinates, such as tablets | |
3313 | ||
a5c6d650 DR |
3314 | movablecore= [KNL,X86,IA-64,PPC] |
3315 | Format: nn[KMGTPE] | nn% | |
3316 | This parameter is the complement to kernelcore=, it | |
3317 | specifies the amount of memory used for migratable | |
3318 | allocations. If both kernelcore and movablecore is | |
3319 | specified, then kernelcore will be at *least* the | |
3320 | specified value but may be more. If movablecore on its | |
3321 | own is specified, the administrator must be careful | |
0cb55ad2 RD |
3322 | that the amount of memory usable for all allocations |
3323 | is not too small. | |
3324 | ||
f70029bb MH |
3325 | movable_node [KNL] Boot-time switch to make hotplugable memory |
3326 | NUMA nodes to be movable. This means that the memory | |
3327 | of such nodes will be usable only for movable | |
3328 | allocations which rules out almost all kernel | |
3329 | allocations. Use with caution! | |
c5320926 | 3330 | |
1da177e4 LT |
3331 | MTD_Partition= [MTD] |
3332 | Format: <name>,<region-number>,<size>,<offset> | |
3333 | ||
a9913044 RD |
3334 | MTD_Region= [MTD] Format: |
3335 | <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>] | |
1da177e4 LT |
3336 | |
3337 | mtdparts= [MTD] | |
fb251124 | 3338 | See drivers/mtd/parsers/cmdlinepart.c |
1da177e4 | 3339 | |
9db829f4 BD |
3340 | mtdset= [ARM] |
3341 | ARM/S3C2412 JIVE boot control | |
3342 | ||
0f12999e | 3343 | See arch/arm/mach-s3c/mach-jive.c |
9db829f4 | 3344 | |
1da177e4 | 3345 | mtouchusb.raw_coordinates= |
a9913044 RD |
3346 | [HW] Make the MicroTouch USB driver use raw coordinates |
3347 | ('y', default) or cooked coordinates ('n') | |
1da177e4 | 3348 | |
0cb55ad2 | 3349 | mtrr_chunk_size=nn[KMG] [X86] |
19f59460 | 3350 | used for mtrr cleanup. It is largest continuous chunk |
0cb55ad2 RD |
3351 | that could hold holes aka. UC entries. |
3352 | ||
3353 | mtrr_gran_size=nn[KMG] [X86] | |
3354 | Used for mtrr cleanup. It is granularity of mtrr block. | |
3355 | Default is 1. | |
3356 | Large value could prevent small alignment from | |
3357 | using up MTRRs. | |
3358 | ||
3359 | mtrr_spare_reg_nr=n [X86] | |
3360 | Format: <integer> | |
3361 | Range: 0,7 : spare reg number | |
3362 | Default : 1 | |
3363 | Used for mtrr cleanup. It is spare mtrr entries number. | |
3364 | Set to 2 or more if your graphical card needs more. | |
3365 | ||
389cfd96 RD |
3366 | multitce=off [PPC] This parameter disables the use of the pSeries |
3367 | firmware feature for updating multiple TCE entries | |
3368 | at a time. | |
3369 | ||
1da177e4 LT |
3370 | n2= [NET] SDL Inc. RISCom/N2 synchronous serial card |
3371 | ||
1da177e4 LT |
3372 | netdev= [NET] Network devices parameters |
3373 | Format: <irq>,<io>,<mem_start>,<mem_end>,<name> | |
3374 | Note that mem_start is often overloaded to mean | |
3375 | something different and driver-specific. | |
a9913044 RD |
3376 | This usage is only documented in each driver source |
3377 | file if at all. | |
3378 | ||
389cfd96 RD |
3379 | netpoll.carrier_timeout= |
3380 | [NET] Specifies amount of time (in seconds) that | |
3381 | netpoll should wait for a carrier. By default netpoll | |
3382 | waits 4 seconds. | |
3383 | ||
58401572 KPO |
3384 | nf_conntrack.acct= |
3385 | [NETFILTER] Enable connection tracking flow accounting | |
3386 | 0 to disable accounting | |
3387 | 1 to enable accounting | |
d70a011d | 3388 | Default value is 0. |
58401572 | 3389 | |
306a0753 | 3390 | nfsaddrs= [NFS] Deprecated. Use ip= instead. |
3eb30c51 | 3391 | See Documentation/admin-guide/nfs/nfsroot.rst. |
1da177e4 LT |
3392 | |
3393 | nfsroot= [NFS] nfs root filesystem for disk-less boxes. | |
3eb30c51 | 3394 | See Documentation/admin-guide/nfs/nfsroot.rst. |
1da177e4 | 3395 | |
306a0753 | 3396 | nfsrootdebug [NFS] enable nfsroot debugging messages. |
3eb30c51 | 3397 | See Documentation/admin-guide/nfs/nfsroot.rst. |
306a0753 | 3398 | |
5405fc44 TM |
3399 | nfs.callback_nr_threads= |
3400 | [NFSv4] set the total number of threads that the | |
3401 | NFS client will assign to service NFSv4 callback | |
3402 | requests. | |
3403 | ||
a72b4422 TM |
3404 | nfs.callback_tcpport= |
3405 | [NFS] set the TCP port on which the NFSv4 callback | |
3406 | channel should listen. | |
3407 | ||
e571cbf1 TM |
3408 | nfs.cache_getent= |
3409 | [NFS] sets the pathname to the program which is used | |
3410 | to update the NFS client cache entries. | |
3411 | ||
3412 | nfs.cache_getent_timeout= | |
3413 | [NFS] sets the timeout after which an attempt to | |
3414 | update a cache entry is deemed to have failed. | |
3415 | ||
58df095b TM |
3416 | nfs.idmap_cache_timeout= |
3417 | [NFS] set the maximum lifetime for idmapper cache | |
3418 | entries. | |
3419 | ||
f43bf0be TM |
3420 | nfs.enable_ino64= |
3421 | [NFS] enable 64-bit inode numbers. | |
3422 | If zero, the NFS client will fake up a 32-bit inode | |
3423 | number for the readdir() and stat() syscalls instead | |
3424 | of returning the full 64-bit number. | |
3425 | The default is to return 64-bit inode numbers. | |
3426 | ||
5405fc44 TM |
3427 | nfs.max_session_cb_slots= |
3428 | [NFSv4.1] Sets the maximum number of session | |
3429 | slots the client will assign to the callback | |
3430 | channel. This determines the maximum number of | |
3431 | callbacks the client will process in parallel for | |
3432 | a particular server. | |
3433 | ||
ef159e91 TM |
3434 | nfs.max_session_slots= |
3435 | [NFSv4.1] Sets the maximum number of session slots | |
3436 | the client will attempt to negotiate with the server. | |
3437 | This limits the number of simultaneous RPC requests | |
3438 | that the client can send to the NFSv4.1 server. | |
3439 | Note that there is little point in setting this | |
3440 | value higher than the max_tcp_slot_table_limit. | |
3441 | ||
b064eca2 | 3442 | nfs.nfs4_disable_idmapping= |
074b1d12 TM |
3443 | [NFSv4] When set to the default of '1', this option |
3444 | ensures that both the RPC level authentication | |
3445 | scheme and the NFS level operations agree to use | |
3446 | numeric uids/gids if the mount is using the | |
3447 | 'sec=sys' security flavour. In effect it is | |
3448 | disabling idmapping, which can make migration from | |
3449 | legacy NFSv2/v3 systems to NFSv4 easier. | |
3450 | Servers that do not support this mode of operation | |
3451 | will be autodetected by the client, and it will fall | |
3452 | back to using the idmapper. | |
3453 | To turn off this behaviour, set the value to '0'. | |
6f2ea7f2 CL |
3454 | nfs.nfs4_unique_id= |
3455 | [NFS4] Specify an additional fixed unique ident- | |
3456 | ification string that NFSv4 clients can insert into | |
3457 | their nfs_client_id4 string. This is typically a | |
3458 | UUID that is generated at system install time. | |
b064eca2 | 3459 | |
db8ac8ba WAA |
3460 | nfs.send_implementation_id = |
3461 | [NFSv4.1] Send client implementation identification | |
3462 | information in exchange_id requests. | |
3463 | If zero, no implementation identification information | |
3464 | will be sent. | |
3465 | The default is to send the implementation identification | |
3466 | information. | |
e52347bd | 3467 | |
f6de7a39 TM |
3468 | nfs.recover_lost_locks = |
3469 | [NFSv4] Attempt to recover locks that were lost due | |
3470 | to a lease timeout on the server. Please note that | |
3471 | doing this risks data corruption, since there are | |
3472 | no guarantees that the file will remain unchanged | |
3473 | after the locks are lost. | |
3474 | If you want to enable the kernel legacy behaviour of | |
3475 | attempting to recover these locks, then set this | |
3476 | parameter to '1'. | |
3477 | The default parameter value of '0' causes the kernel | |
3478 | not to attempt recovery of lost locks. | |
db8ac8ba | 3479 | |
bbf58bf3 TM |
3480 | nfs4.layoutstats_timer = |
3481 | [NFSv4.2] Change the rate at which the kernel sends | |
3482 | layoutstats to the pNFS metadata server. | |
3483 | ||
3484 | Setting this to value to 0 causes the kernel to use | |
3485 | whatever value is the default set by the layout | |
3486 | driver. A non-zero value sets the minimum interval | |
3487 | in seconds between layoutstats transmissions. | |
3488 | ||
6d91929a BF |
3489 | nfsd.inter_copy_offload_enable = |
3490 | [NFSv4.2] When set to 1, the server will support | |
3491 | server-to-server copies for which this server is | |
3492 | the destination of the copy. | |
3493 | ||
3494 | nfsd.nfsd4_ssc_umount_timeout = | |
3495 | [NFSv4.2] When used as the destination of a | |
3496 | server-to-server copy, knfsd temporarily mounts | |
3497 | the source server. It caches the mount in case | |
3498 | it will be needed again, and discards it if not | |
3499 | used for the number of milliseconds specified by | |
3500 | this parameter. | |
3501 | ||
e9541ce8 BF |
3502 | nfsd.nfs4_disable_idmapping= |
3503 | [NFSv4] When set to the default of '1', the NFSv4 | |
3504 | server will return only numeric uids and gids to | |
3505 | clients using auth_sys, and will accept numeric uids | |
3506 | and gids from such clients. This is intended to ease | |
3507 | migration from NFSv2/v3. | |
db8ac8ba | 3508 | |
6d91929a | 3509 | |
160c7ba3 PM |
3510 | nmi_backtrace.backtrace_idle [KNL] |
3511 | Dump stacks even of idle CPUs in response to an | |
3512 | NMI stack-backtrace request. | |
3513 | ||
c0c74acb | 3514 | nmi_debug= [KNL,SH] Specify one or more actions to take |
e7ba176b HS |
3515 | when a NMI is triggered. |
3516 | Format: [state][,regs][,debounce][,die] | |
3517 | ||
6cececfc | 3518 | nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels |
fef2c9bc | 3519 | Format: [panic,][nopanic,][num] |
195daf66 | 3520 | Valid num: 0 or 1 |
334bb79c PK |
3521 | 0 - turn hardlockup detector in nmi_watchdog off |
3522 | 1 - turn hardlockup detector in nmi_watchdog on | |
0cb55ad2 | 3523 | When panic is specified, panic when an NMI watchdog |
93285c01 ZD |
3524 | timeout occurs (or 'nopanic' to not panic on an NMI |
3525 | watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set) | |
3526 | To disable both hard and soft lockup detectors, | |
334bb79c | 3527 | please see 'nowatchdog'. |
0cb55ad2 RD |
3528 | This is useful when you use a panic=... timeout and |
3529 | need the box quickly up again. | |
1da177e4 | 3530 | |
d22881dc SW |
3531 | These settings can be accessed at runtime via |
3532 | the nmi_watchdog and hardlockup_panic sysctls. | |
3533 | ||
cd4f0ef7 | 3534 | no387 [BUGS=X86-32] Tells the kernel to use the 387 maths |
1da177e4 LT |
3535 | emulation library even if a 387 maths coprocessor |
3536 | is present. | |
3537 | ||
372fddf7 KS |
3538 | no5lvl [X86-64] Disable 5-level paging mode. Forces |
3539 | kernel to use 4-level paging instead. | |
3540 | ||
b745cfba | 3541 | nofsgsbase [X86] Disables FSGSBASE instructions. |
dd649bd0 | 3542 | |
0cb55ad2 RD |
3543 | no_console_suspend |
3544 | [HW] Never suspend the console | |
3545 | Disable suspending of consoles during suspend and | |
3546 | hibernate operations. Once disabled, debugging | |
3547 | messages can reach various consoles while the rest | |
3548 | of the system is being put to sleep (ie, while | |
3549 | debugging driver suspend/resume hooks). This may | |
3550 | not work reliably with all consoles, but is known | |
3551 | to work with serial and VGA consoles. | |
134620f7 YZ |
3552 | To facilitate more flexible debugging, we also add |
3553 | console_suspend, a printk module parameter to control | |
3554 | it. Users could use console_suspend (usually | |
3555 | /sys/module/printk/parameters/console_suspend) to | |
3556 | turn on/off it dynamically. | |
0cb55ad2 | 3557 | |
c6c40533 KS |
3558 | novmcoredd [KNL,KDUMP] |
3559 | Disable device dump. Device dump allows drivers to | |
3560 | append dump data to vmcore so you can collect driver | |
3561 | specified debug info. Drivers can append the data | |
3562 | without any limit and this data is stored in memory, | |
3563 | so this may cause significant memory stress. Disabling | |
3564 | device dump can help save memory but the driver debug | |
3565 | data will be no longer available. This parameter | |
3566 | is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP | |
3567 | is set. | |
3568 | ||
c1aee215 CL |
3569 | noaliencache [MM, NUMA, SLAB] Disables the allocation of alien |
3570 | caches in the slab allocator. Saves per-node memory, | |
3571 | but will impact performance. | |
3395ee05 | 3572 | |
a9913044 RD |
3573 | noalign [KNL,ARM] |
3574 | ||
686140a1 VG |
3575 | noaltinstr [S390] Disables alternative instructions patching |
3576 | (CPU alternatives feature). | |
3577 | ||
1da177e4 LT |
3578 | noapic [SMP,APIC] Tells the kernel to not make use of any |
3579 | IOAPICs that may be present in the system. | |
3580 | ||
5091faa4 MG |
3581 | noautogroup Disable scheduler automatic task group creation. |
3582 | ||
1da177e4 | 3583 | nocache [ARM] |
a9913044 | 3584 | |
6902aa84 PM |
3585 | nodsp [SH] Disable hardware DSP at boot time. |
3586 | ||
b2e0a54a | 3587 | noefi Disable EFI runtime services support. |
8b2cb7a8 | 3588 | |
f7964378 NP |
3589 | no_entry_flush [PPC] Don't flush the L1-D cache when entering the kernel. |
3590 | ||
1da177e4 LT |
3591 | noexec [IA-64] |
3592 | ||
dbae0a93 | 3593 | nosmap [PPC] |
52b6179a PA |
3594 | Disable SMAP (Supervisor Mode Access Prevention) |
3595 | even if it is supported by processor. | |
3596 | ||
385d2ae0 | 3597 | nosmep [PPC64s] |
52b6179a | 3598 | Disable SMEP (Supervisor Mode Execution Prevention) |
de5397ad FY |
3599 | even if it is supported by processor. |
3600 | ||
f5a1b191 JS |
3601 | noexec32 [X86-64] |
3602 | This affects only 32-bit executables. | |
3603 | noexec32=on: enable non-executable mappings (default) | |
3604 | read doesn't imply executable mappings | |
3605 | noexec32=off: disable non-executable mappings | |
3606 | read implies executable mappings | |
1da177e4 | 3607 | |
fab43ef4 | 3608 | nofpu [MIPS,SH] Disable hardware FPU at boot time. |
6902aa84 | 3609 | |
cd4f0ef7 | 3610 | nofxsr [BUGS=X86-32] Disables x86 floating point extended |
4f886511 CE |
3611 | register save and restore. The kernel will only save |
3612 | legacy floating-point registers on task switch. | |
1da177e4 | 3613 | |
5b280ed4 | 3614 | nohugeiomap [KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings. |
0ddab1d2 | 3615 | |
8abddd96 NP |
3616 | nohugevmalloc [PPC] Disable kernel huge vmalloc mappings. |
3617 | ||
52c48c51 SS |
3618 | nosmt [KNL,S390] Disable symmetric multithreading (SMT). |
3619 | Equivalent to smt=1. | |
3620 | ||
be3a5b0e | 3621 | [KNL,X86] Disable symmetric multithreading (SMT). |
506a66f3 TG |
3622 | nosmt=force: Force disable SMT, cannot be undone |
3623 | via the sysfs control file. | |
5e2d059b | 3624 | |
a2059825 JP |
3625 | nospectre_v1 [X86,PPC] Disable mitigations for Spectre Variant 1 |
3626 | (bounds check bypass). With this option data leaks are | |
3627 | possible in the system. | |
05736e4a | 3628 | |
e5ce5e72 JL |
3629 | nospectre_v2 [X86,PPC_FSL_BOOK3E,ARM64] Disable all mitigations for |
3630 | the Spectre variant 2 (indirect branch prediction) | |
3631 | vulnerability. System may allow data leaks with this | |
3632 | option. | |
da285121 | 3633 | |
24f7fc83 KRW |
3634 | nospec_store_bypass_disable |
3635 | [HW] Disable all mitigations for the Speculative Store Bypass vulnerability | |
3636 | ||
9a32a7e7 NP |
3637 | no_uaccess_flush |
3638 | [PPC] Don't flush the L1-D cache after accessing user data. | |
3639 | ||
0c752a93 SS |
3640 | noxsave [BUGS=X86] Disables x86 extended register state save |
3641 | and restore using xsave. The kernel will fallback to | |
3642 | enabling legacy floating-point and sse state. | |
3643 | ||
b6f42a4a FY |
3644 | noxsaveopt [X86] Disables xsaveopt used in saving x86 extended |
3645 | register states. The kernel will fall back to use | |
3646 | xsave to save the states. By using this parameter, | |
3647 | performance of saving the states is degraded because | |
3648 | xsave doesn't support modified optimization while | |
3649 | xsaveopt supports it on xsaveopt enabled systems. | |
3650 | ||
3651 | noxsaves [X86] Disables xsaves and xrstors used in saving and | |
3652 | restoring x86 extended register state in compacted | |
3653 | form of xsave area. The kernel will fall back to use | |
3654 | xsaveopt and xrstor to save and restore the states | |
3655 | in standard form of xsave area. By using this | |
3656 | parameter, xsave area per process might occupy more | |
3657 | memory on xsaves enabled systems. | |
3658 | ||
3cae85f5 FF |
3659 | nohlt [ARM,ARM64,MICROBLAZE,SH] Forces the kernel to busy wait |
3660 | in do_idle() and not use the arch_cpu_idle() | |
3661 | implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP | |
3662 | to be effective. This is useful on platforms where the | |
3663 | sleep(SH) or wfi(ARM,ARM64) instructions do not work | |
3664 | correctly or when doing power measurements to evalute | |
3665 | the impact of the sleep instructions. This is also | |
3666 | useful when using JTAG debugger. | |
a9913044 | 3667 | |
1f29fae2 SH |
3668 | no_file_caps Tells the kernel not to honor file capabilities. The |
3669 | only way then for a file to be executed with privilege | |
3670 | is to be setuid root or executed by root. | |
3671 | ||
1da177e4 LT |
3672 | nohalt [IA-64] Tells the kernel not to use the power saving |
3673 | function PAL_HALT_LIGHT when idle. This increases | |
3674 | power-consumption. On the positive side, it reduces | |
3675 | interrupt wake-up latency, which may improve performance | |
3676 | in certain environments such as networked servers or | |
3677 | real-time systems. | |
3678 | ||
5ead723a TT |
3679 | no_hash_pointers |
3680 | Force pointers printed to the console or buffers to be | |
3681 | unhashed. By default, when a pointer is printed via %p | |
3682 | format string, that pointer is "hashed", i.e. obscured | |
3683 | by hashing the pointer value. This is a security feature | |
3684 | that hides actual kernel addresses from unprivileged | |
3685 | users, but it also makes debugging the kernel more | |
3686 | difficult since unequal pointers can no longer be | |
3687 | compared. However, if this command-line option is | |
3688 | specified, then all normal pointers will have their true | |
84842911 | 3689 | value printed. This option should only be specified when |
5ead723a TT |
3690 | debugging the kernel. Please do not use on production |
3691 | kernels. | |
3692 | ||
a6e15a39 KC |
3693 | nohibernate [HIBERNATION] Disable hibernation and resume. |
3694 | ||
79bf2bb3 TG |
3695 | nohz= [KNL] Boottime enable/disable dynamic ticks |
3696 | Valid arguments: on, off | |
3697 | Default: on | |
3698 | ||
d94d1053 | 3699 | nohz_full= [KNL,BOOT,SMP,ISOL] |
2d13e6ca | 3700 | The argument is a cpu list, as described above. |
c5bfece2 | 3701 | In kernels built with CONFIG_NO_HZ_FULL=y, set |
a831881b | 3702 | the specified list of CPUs whose tick will be stopped |
0453b435 | 3703 | whenever possible. The boot CPU will be forced outside |
f99bcb2c PM |
3704 | the range to maintain the timekeeping. Any CPUs |
3705 | in this list will have their RCU callbacks offloaded, | |
3706 | just as if they had also been called out in the | |
3707 | rcu_nocbs= boot parameter. | |
a831881b | 3708 | |
b37a667c JF |
3709 | Note that this argument takes precedence over |
3710 | the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option. | |
3711 | ||
eeee7853 PM |
3712 | noiotrap [SH] Disables trapped I/O port accesses. |
3713 | ||
cd4f0ef7 | 3714 | noirqdebug [X86-32] Disables the code which attempts to detect and |
1da177e4 LT |
3715 | disable unhandled interrupt sources. |
3716 | ||
6cececfc | 3717 | no_timer_check [X86,APIC] Disables the code which tests for |
8542b200 ZA |
3718 | broken timer IRQ sources. |
3719 | ||
1da177e4 LT |
3720 | noisapnp [ISAPNP] Disables ISA PnP code. |
3721 | ||
3722 | noinitrd [RAM] Tells the kernel not to load any configured | |
3723 | initial RAM disk. | |
3724 | ||
03ea8155 WH |
3725 | nointremap [X86-64, Intel-IOMMU] Do not enable interrupt |
3726 | remapping. | |
d1423d56 | 3727 | [Deprecated - use intremap=off] |
03ea8155 | 3728 | |
1da177e4 LT |
3729 | nointroute [IA-64] |
3730 | ||
d12a72b8 AL |
3731 | noinvpcid [X86] Disable the INVPCID cpu feature. |
3732 | ||
16290246 | 3733 | nojitter [IA-64] Disables jitter checking for ITC timers. |
0aa366f3 | 3734 | |
9cf4c4fc JK |
3735 | no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver |
3736 | ||
fd10cde9 GN |
3737 | no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page |
3738 | fault handling. | |
3739 | ||
80e9a4f2 AM |
3740 | no-vmw-sched-clock |
3741 | [X86,PV_OPS] Disable paravirtualized VMware scheduler | |
3742 | clock and use the default one. | |
3743 | ||
e73a8f38 | 3744 | no-steal-acc [X86,PV_OPS,ARM64] Disable paravirtualized steal time |
e0685fa2 SP |
3745 | accounting. steal time is computed, but won't |
3746 | influence scheduler behaviour | |
d910f5c1 | 3747 | |
cd4f0ef7 | 3748 | nolapic [X86-32,APIC] Do not enable or use the local APIC. |
1da177e4 | 3749 | |
cd4f0ef7 | 3750 | nolapic_timer [X86-32,APIC] Do not use the local APIC timer. |
ad62ca2b | 3751 | |
312f1f01 H |
3752 | nomca [IA-64] Disable machine check abort handling |
3753 | ||
13696e0a | 3754 | nomce [X86-32] Disable Machine Check Exception |
abe37e5a | 3755 | |
83d7384f AS |
3756 | nomfgpt [X86-32] Disable Multi-Function General Purpose |
3757 | Timer usage (for AMD Geode machines). | |
3758 | ||
bda62633 DZ |
3759 | nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to |
3760 | shutdown the other cpus. Instead use the REBOOT_VECTOR | |
3761 | irq. | |
3762 | ||
b22a15a5 JMC |
3763 | nomodeset Disable kernel modesetting. DRM drivers will not perform |
3764 | display-mode changes or accelerated rendering. Only the | |
3765 | system framebuffer will be available for use if this was | |
3766 | set-up by the firmware or boot loader. | |
3767 | ||
3768 | Useful as fallback, or for testing and debugging. | |
3769 | ||
02608bef DY |
3770 | nomodule Disable module load |
3771 | ||
016ddd9b JK |
3772 | nopat [X86] Disable PAT (page attribute table extension of |
3773 | pagetables) support. | |
3774 | ||
0790c9aa AL |
3775 | nopcid [X86-64] Disable the PCID cpu feature. |
3776 | ||
0cb55ad2 RD |
3777 | norandmaps Don't use address space randomization. Equivalent to |
3778 | echo 0 > /proc/sys/kernel/randomize_va_space | |
3779 | ||
cd4f0ef7 | 3780 | noreplace-smp [X86-32,SMP] Don't replace SMP instructions |
b7fb4af0 JF |
3781 | with UP alternatives |
3782 | ||
a9913044 RD |
3783 | noresume [SWSUSP] Disables resume and restores original swap |
3784 | space. | |
3785 | ||
1da177e4 LT |
3786 | no-scroll [VGA] Disables scrollback. |
3787 | This is required for the Braillex ib80-piezo Braille | |
3788 | reader made by F.H. Papenmeier (Germany). | |
3789 | ||
3790 | nosbagart [IA-64] | |
3791 | ||
38853a30 JS |
3792 | nosgx [X86-64,SGX] Disables Intel SGX kernel support. |
3793 | ||
61ec7567 LB |
3794 | nosmp [SMP] Tells an SMP kernel to act as a UP kernel, |
3795 | and disable the IO APIC. legacy for "maxcpus=0". | |
1da177e4 | 3796 | |
97842216 DJ |
3797 | nosoftlockup [KNL] Disable the soft-lockup detector. |
3798 | ||
1da177e4 LT |
3799 | nosync [HW,M68K] Disables sync negotiation for all devices. |
3800 | ||
195daf66 | 3801 | nowatchdog [KNL] Disable both lockup detectors, i.e. |
6dddd7a7 | 3802 | soft-lockup and NMI watchdog (hard-lockup). |
58687acb | 3803 | |
1da177e4 | 3804 | nowb [ARM] |
a9913044 | 3805 | |
2b2fd87a WH |
3806 | nox2apic [X86-64,APIC] Do not enable x2APIC mode. |
3807 | ||
6dddd7a7 | 3808 | nps_mtm_hs_ctr= [KNL,ARC] |
35b55ef2 NC |
3809 | This parameter sets the maximum duration, in |
3810 | cycles, each HW thread of the CTOP can run | |
3811 | without interruptions, before HW switches it. | |
3812 | The actual maximum duration is 16 times this | |
3813 | parameter's value. | |
3814 | Format: integer between 1 and 255 | |
3815 | Default: 255 | |
3816 | ||
16290246 | 3817 | nptcg= [IA-64] Override max number of concurrent global TLB |
a6c75b86 FY |
3818 | purges which is reported from either PAL_VM_SUMMARY or |
3819 | SAL PALO. | |
3820 | ||
2b633e3f YL |
3821 | nr_cpus= [SMP] Maximum number of processors that an SMP kernel |
3822 | could support. nr_cpus=n : n >= 1 limits the kernel to | |
7c142bfe BH |
3823 | support 'n' processors. It could be larger than the |
3824 | number of already plugged CPU during bootup, later in | |
3825 | runtime you can physically add extra cpu until it reaches | |
3826 | n. So during boot up some boot time memory for per-cpu | |
3827 | variables need be pre-allocated for later physical cpu | |
3828 | hot plugging. | |
2b633e3f | 3829 | |
0cb55ad2 RD |
3830 | nr_uarts= [SERIAL] maximum number of UARTs to be registered. |
3831 | ||
544ef682 BS |
3832 | numa=off [KNL, ARM64, PPC, RISCV, SPARC, X86] Disable NUMA, Only |
3833 | set up a single NUMA node spanning all memory. | |
3834 | ||
00b072c0 BS |
3835 | numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic |
3836 | NUMA balancing. | |
1a687c2e MG |
3837 | Allowed values are enable and disable |
3838 | ||
f0c0b2b8 | 3839 | numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. |
c9bff3ee | 3840 | 'node', 'default' can be specified |
f0c0b2b8 | 3841 | This can be set from sysctl after boot. |
57043247 | 3842 | See Documentation/admin-guide/sysctl/vm.rst for details. |
f0c0b2b8 | 3843 | |
7c4be253 | 3844 | ohci1394_dma=early [HW] enable debugging via the ohci1394 driver. |
a74e2a22 | 3845 | See Documentation/core-api/debugging-via-ohci1394.rst for more |
7c4be253 RD |
3846 | info. |
3847 | ||
3ef0e1f8 AS |
3848 | olpc_ec_timeout= [OLPC] ms delay when issuing EC commands |
3849 | Rather than timing out after 20 ms if an EC | |
3850 | command is not properly ACKed, override the length | |
3851 | of the timeout. We have interrupts disabled while | |
3852 | waiting for the ACK, so if this is set too high | |
3853 | interrupts *may* be lost! | |
3854 | ||
15ac7afe TL |
3855 | omap_mux= [OMAP] Override bootloader pin multiplexing. |
3856 | Format: <mux_mode0.mode_name=value>... | |
3857 | For example, to override I2C bus2: | |
3858 | omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100 | |
3859 | ||
d2fc83c1 RD |
3860 | onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration |
3861 | ||
3862 | Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock] | |
3863 | ||
3864 | boundary - index of last SLC block on Flex-OneNAND. | |
3865 | The remaining blocks are configured as MLC blocks. | |
3866 | lock - Configure if Flex-OneNAND boundary should be locked. | |
3867 | Once locked, the boundary cannot be changed. | |
3868 | 1 indicates lock status, 0 indicates unlock status. | |
3869 | ||
44a4dcf7 RD |
3870 | oops=panic Always panic on oopses. Default is to just kill the |
3871 | process, but there is a small probability of | |
3872 | deadlocking the machine. | |
d404ab0a OH |
3873 | This will also cause panics on machine check exceptions. |
3874 | Useful together with panic=30 to trigger a reboot. | |
3875 | ||
e900a918 DW |
3876 | page_alloc.shuffle= |
3877 | [KNL] Boolean flag to control whether the page allocator | |
3878 | should randomize its free lists. The randomization may | |
3879 | be automatically enabled if the kernel detects it is | |
3880 | running on a platform with a direct-mapped memory-side | |
3881 | cache, and this parameter can be used to | |
3882 | override/disable that behavior. The state of the flag | |
3883 | can be read from sysfs at: | |
3884 | /sys/module/page_alloc/parameters/shuffle. | |
3885 | ||
48c96a36 JK |
3886 | page_owner= [KNL] Boot-time page_owner enabling option. |
3887 | Storage of the information about who allocated | |
3888 | each page is disabled in default. With this switch, | |
3889 | we can turn it on. | |
3890 | on: enable the feature | |
3891 | ||
8823b1db | 3892 | page_poison= [KNL] Boot-time parameter changing the state of |
8c9a134c KC |
3893 | poisoning on the buddy allocator, available with |
3894 | CONFIG_PAGE_POISONING=y. | |
3895 | off: turn off poisoning (default) | |
8823b1db LA |
3896 | on: turn on poisoning |
3897 | ||
f58780a8 GS |
3898 | page_reporting.page_reporting_order= |
3899 | [KNL] Minimal page reporting order | |
3900 | Format: <integer> | |
3901 | Adjust the minimal page reporting order. The page | |
3902 | reporting is disabled when it exceeds (MAX_ORDER-1). | |
3903 | ||
44a4dcf7 | 3904 | panic= [KNL] Kernel behaviour on panic: delay <timeout> |
4302fbc8 HD |
3905 | timeout > 0: seconds before rebooting |
3906 | timeout = 0: wait forever | |
3907 | timeout < 0: reboot immediately | |
1da177e4 LT |
3908 | Format: <timeout> |
3909 | ||
d999bd93 FT |
3910 | panic_print= Bitmask for printing system info when panic happens. |
3911 | User can chose combination of the following bits: | |
3912 | bit 0: print all tasks info | |
3913 | bit 1: print system memory info | |
3914 | bit 2: print timer info | |
3915 | bit 3: print locks info if CONFIG_LOCKDEP is on | |
3916 | bit 4: print ftrace buffer | |
de6da1e8 | 3917 | bit 5: print all printk messages in buffer |
8d470a45 | 3918 | bit 6: print all CPUs backtrace (if available in the arch) |
f953f140 GP |
3919 | *Be aware* that this option may print a _lot_ of lines, |
3920 | so there are risks of losing older messages in the log. | |
3921 | Use this option carefully, maybe worth to setup a | |
3922 | bigger log buffer with "log_buf_len" along with this. | |
d999bd93 | 3923 | |
db38d5c1 RA |
3924 | panic_on_taint= Bitmask for conditionally calling panic() in add_taint() |
3925 | Format: <hex>[,nousertaint] | |
3926 | Hexadecimal bitmask representing the set of TAINT flags | |
3927 | that will cause the kernel to panic when add_taint() is | |
3928 | called with any of the flags in this set. | |
3929 | The optional switch "nousertaint" can be utilized to | |
3930 | prevent userspace forced crashes by writing to sysctl | |
3931 | /proc/sys/kernel/tainted any flagset matching with the | |
3932 | bitmask set on panic_on_taint. | |
3933 | See Documentation/admin-guide/tainted-kernels.rst for | |
3934 | extra details on the taint flags that users can pick | |
3935 | to compose the bitmask to assign to panic_on_taint. | |
3936 | ||
9e3961a0 PB |
3937 | panic_on_warn panic() instead of WARN(). Useful to cause kdump |
3938 | on a WARN(). | |
3939 | ||
1da177e4 LT |
3940 | parkbd.port= [HW] Parallel port number the keyboard adapter is |
3941 | connected to, default is 0. | |
3942 | Format: <parport#> | |
3943 | parkbd.mode= [HW] Parallel port keyboard adapter mode of operation, | |
3944 | 0 for XT, 1 for AT (default is AT). | |
a9913044 RD |
3945 | Format: <mode> |
3946 | ||
3947 | parport= [HW,PPT] Specify parallel ports. 0 disables. | |
3948 | Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] } | |
3949 | Use 'auto' to force the driver to use any | |
3950 | IRQ/DMA settings detected (the default is to | |
3951 | ignore detected IRQ/DMA settings because of | |
3952 | possible conflicts). You can specify the base | |
3953 | address, IRQ, and DMA settings; IRQ and DMA | |
3954 | should be numbers, or 'auto' (for using detected | |
3955 | settings on that particular port), or 'nofifo' | |
3956 | (to avoid using a FIFO even if it is detected). | |
3957 | Parallel ports are assigned in the order they | |
3958 | are specified on the command line, starting | |
3959 | with parport0. | |
3960 | ||
3961 | parport_init_mode= [HW,PPT] | |
3962 | Configure VIA parallel port to operate in | |
3963 | a specific mode. This is necessary on Pegasos | |
3964 | computer where firmware has no options for setting | |
3965 | up parallel port mode and sets it to spp. | |
3966 | Currently this function knows 686a and 8231 chips. | |
1da177e4 LT |
3967 | Format: [spp|ps2|epp|ecp|ecpepp] |
3968 | ||
426e2c6a MR |
3969 | pata_legacy.all= [HW,LIBATA] |
3970 | Format: <int> | |
3971 | Set to non-zero to probe primary and secondary ISA | |
3972 | port ranges on PCI systems where no PCI PATA device | |
3973 | has been found at either range. Disabled by default. | |
3974 | ||
3975 | pata_legacy.autospeed= [HW,LIBATA] | |
3976 | Format: <int> | |
3977 | Set to non-zero if a chip is present that snoops speed | |
3978 | changes. Disabled by default. | |
3979 | ||
3980 | pata_legacy.ht6560a= [HW,LIBATA] | |
3981 | Format: <int> | |
3982 | Set to 1, 2, or 3 for HT 6560A on the primary channel, | |
3983 | the secondary channel, or both channels respectively. | |
3984 | Disabled by default. | |
3985 | ||
3986 | pata_legacy.ht6560b= [HW,LIBATA] | |
3987 | Format: <int> | |
3988 | Set to 1, 2, or 3 for HT 6560B on the primary channel, | |
3989 | the secondary channel, or both channels respectively. | |
3990 | Disabled by default. | |
3991 | ||
3992 | pata_legacy.iordy_mask= [HW,LIBATA] | |
3993 | Format: <int> | |
3994 | IORDY enable mask. Set individual bits to allow IORDY | |
3995 | for the respective channel. Bit 0 is for the first | |
3996 | legacy channel handled by this driver, bit 1 is for | |
3997 | the second channel, and so on. The sequence will often | |
3998 | correspond to the primary legacy channel, the secondary | |
3999 | legacy channel, and so on, but the handling of a PCI | |
4000 | bus and the use of other driver options may interfere | |
4001 | with the sequence. By default IORDY is allowed across | |
4002 | all channels. | |
4003 | ||
4004 | pata_legacy.opti82c46x= [HW,LIBATA] | |
4005 | Format: <int> | |
4006 | Set to 1, 2, or 3 for Opti 82c611A on the primary | |
4007 | channel, the secondary channel, or both channels | |
4008 | respectively. Disabled by default. | |
4009 | ||
4010 | pata_legacy.opti82c611a= [HW,LIBATA] | |
4011 | Format: <int> | |
4012 | Set to 1, 2, or 3 for Opti 82c465MV on the primary | |
4013 | channel, the secondary channel, or both channels | |
4014 | respectively. Disabled by default. | |
4015 | ||
4016 | pata_legacy.pio_mask= [HW,LIBATA] | |
4017 | Format: <int> | |
4018 | PIO mode mask for autospeed devices. Set individual | |
4019 | bits to allow the use of the respective PIO modes. | |
4020 | Bit 0 is for mode 0, bit 1 is for mode 1, and so on. | |
4021 | All modes allowed by default. | |
4022 | ||
4023 | pata_legacy.probe_all= [HW,LIBATA] | |
4024 | Format: <int> | |
4025 | Set to non-zero to probe tertiary and further ISA | |
4026 | port ranges on PCI systems. Disabled by default. | |
4027 | ||
7d33004d MR |
4028 | pata_legacy.probe_mask= [HW,LIBATA] |
4029 | Format: <int> | |
4030 | Probe mask for legacy ISA PATA ports. Depending on | |
4031 | platform configuration and the use of other driver | |
4032 | options up to 6 legacy ports are supported: 0x1f0, | |
4033 | 0x170, 0x1e8, 0x168, 0x1e0, 0x160, however probing | |
4034 | of individual ports can be disabled by setting the | |
4035 | corresponding bits in the mask to 1. Bit 0 is for | |
4036 | the first port in the list above (0x1f0), and so on. | |
4037 | By default all supported ports are probed. | |
4038 | ||
426e2c6a MR |
4039 | pata_legacy.qdi= [HW,LIBATA] |
4040 | Format: <int> | |
4041 | Set to non-zero to probe QDI controllers. By default | |
4042 | set to 1 if CONFIG_PATA_QDI_MODULE, 0 otherwise. | |
4043 | ||
4044 | pata_legacy.winbond= [HW,LIBATA] | |
4045 | Format: <int> | |
4046 | Set to non-zero to probe Winbond controllers. Use | |
4047 | the standard I/O port (0x130) if 1, otherwise the | |
4048 | value given is the I/O port to use (typically 0x1b0). | |
4049 | By default set to 1 if CONFIG_PATA_WINBOND_VLB_MODULE, | |
4050 | 0 otherwise. | |
4051 | ||
6ddcec95 MR |
4052 | pata_platform.pio_mask= [HW,LIBATA] |
4053 | Format: <int> | |
4054 | Supported PIO mode mask. Set individual bits to allow | |
4055 | the use of the respective PIO modes. Bit 0 is for | |
4056 | mode 0, bit 1 is for mode 1, and so on. Mode 0 only | |
4057 | allowed by default. | |
4058 | ||
dd287796 AM |
4059 | pause_on_oops= |
4060 | Halt all CPUs after the first oops has been printed for | |
4061 | the specified number of seconds. This is to be used if | |
4062 | your oopses keep scrolling off the screen. | |
4063 | ||
1da177e4 LT |
4064 | pcbit= [HW,ISDN] |
4065 | ||
4066 | pcd. [PARIDE] | |
4067 | See header of drivers/block/paride/pcd.c. | |
e7751617 | 4068 | See also Documentation/admin-guide/blockdev/paride.rst. |
1da177e4 | 4069 | |
07d8d7e5 LG |
4070 | pci=option[,option...] [PCI] various PCI subsystem options. |
4071 | ||
4072 | Some options herein operate on a specific device | |
4073 | or a set of devices (<pci_dev>). These are | |
4074 | specified in one of the following formats: | |
4075 | ||
45db3370 | 4076 | [<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]* |
07d8d7e5 LG |
4077 | pci:<vendor>:<device>[:<subvendor>:<subdevice>] |
4078 | ||
4079 | Note: the first format specifies a PCI | |
4080 | bus/device/function address which may change | |
4081 | if new hardware is inserted, if motherboard | |
4082 | firmware changes, or due to changes caused | |
4083 | by other kernel parameters. If the | |
4084 | domain is left unspecified, it is | |
45db3370 LG |
4085 | taken to be zero. Optionally, a path |
4086 | to a device through multiple device/function | |
4087 | addresses can be specified after the base | |
4088 | address (this is more robust against | |
4089 | renumbering issues). The second format | |
07d8d7e5 LG |
4090 | selects devices using IDs from the |
4091 | configuration space which may match multiple | |
4092 | devices in the system. | |
4093 | ||
11eb0e0e | 4094 | earlydump dump PCI config space before the kernel |
6dddd7a7 | 4095 | changes anything |
c0115606 | 4096 | off [X86] don't probe for the PCI bus |
cd4f0ef7 | 4097 | bios [X86-32] force use of PCI BIOS, don't access |
a9913044 RD |
4098 | the hardware directly. Use this if your machine |
4099 | has a non-standard PCI host bridge. | |
cd4f0ef7 | 4100 | nobios [X86-32] disallow use of PCI BIOS, only direct |
a9913044 RD |
4101 | hardware access methods are allowed. Use this |
4102 | if you experience crashes upon bootup and you | |
4103 | suspect they are caused by the BIOS. | |
afd8c084 BP |
4104 | conf1 [X86] Force use of PCI Configuration Access |
4105 | Mechanism 1 (config address in IO port 0xCF8, | |
4106 | data in IO port 0xCFC, both 32-bit). | |
4107 | conf2 [X86] Force use of PCI Configuration Access | |
4108 | Mechanism 2 (IO port 0xCF8 is an 8-bit port for | |
4109 | the function, IO port 0xCFA, also 8-bit, sets | |
4110 | bus number. The config space is then accessed | |
4111 | through ports 0xC000-0xCFFF). | |
4112 | See http://wiki.osdev.org/PCI for more info | |
4113 | on the configuration access mechanisms. | |
7f785763 RD |
4114 | noaer [PCIE] If the PCIEAER kernel config parameter is |
4115 | enabled, this kernel boot option can be used to | |
4116 | disable the use of PCIE advanced error reporting. | |
32a2eea7 JG |
4117 | nodomains [PCI] Disable support for multiple PCI |
4118 | root domains (aka PCI segments, in ACPI-speak). | |
6cececfc | 4119 | nommconf [X86] Disable use of MMCONFIG for PCI |
61be6d66 | 4120 | Configuration |
12983077 AH |
4121 | check_enable_amd_mmconf [X86] check for and enable |
4122 | properly configured MMIO access to PCI | |
4123 | config space on AMD family 10h CPU | |
309e57df MW |
4124 | nomsi [MSI] If the PCI_MSI kernel config parameter is |
4125 | enabled, this kernel boot option can be used to | |
4126 | disable the use of MSI interrupts system-wide. | |
a9322f64 SA |
4127 | noioapicquirk [APIC] Disable all boot interrupt quirks. |
4128 | Safety option to keep boot IRQs enabled. This | |
4129 | should never be necessary. | |
9197979b SA |
4130 | ioapicreroute [APIC] Enable rerouting of boot IRQs to the |
4131 | primary IO-APIC for bridges that cannot disable | |
4132 | boot IRQs. This fixes a source of spurious IRQs | |
4133 | when the system masks IRQs. | |
41b9eb26 SA |
4134 | noioapicreroute [APIC] Disable workaround that uses the |
4135 | boot IRQ equivalent of an IRQ that connects to | |
4136 | a chipset where boot IRQs cannot be disabled. | |
4137 | The opposite of ioapicreroute. | |
cd4f0ef7 | 4138 | biosirq [X86-32] Use PCI BIOS calls to get the interrupt |
a9913044 RD |
4139 | routing table. These calls are known to be buggy |
4140 | on several machines and they hang the machine | |
4141 | when used, but on other computers it's the only | |
4142 | way to get the interrupt routing table. Try | |
4143 | this option if the kernel is unable to allocate | |
4144 | IRQs or discover secondary PCI buses on your | |
4145 | motherboard. | |
c0115606 | 4146 | rom [X86] Assign address space to expansion ROMs. |
a9913044 RD |
4147 | Use with caution as certain devices share |
4148 | address decoders between ROMs and other | |
4149 | resources. | |
c0115606 | 4150 | norom [X86] Do not assign address space to |
bb71ad88 GH |
4151 | expansion ROMs that do not already have |
4152 | BIOS assigned address ranges. | |
7bd1c365 MH |
4153 | nobar [X86] Do not assign address space to the |
4154 | BARs that weren't assigned by the BIOS. | |
c0115606 | 4155 | irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be |
a9913044 RD |
4156 | assigned automatically to PCI devices. You can |
4157 | make the kernel exclude IRQs of your ISA cards | |
4158 | this way. | |
c0115606 | 4159 | pirqaddr=0xAAAAA [X86] Specify the physical address |
a9913044 RD |
4160 | of the PIRQ table (normally generated |
4161 | by the BIOS) if it is outside the | |
4162 | F0000h-100000h range. | |
c0115606 | 4163 | lastbus=N [X86] Scan all buses thru bus #N. Can be |
a9913044 RD |
4164 | useful if the kernel is unable to find your |
4165 | secondary buses and you want to tell it | |
4166 | explicitly which ones they are. | |
c0115606 | 4167 | assign-busses [X86] Always assign all PCI bus |
a9913044 RD |
4168 | numbers ourselves, overriding |
4169 | whatever the firmware may have done. | |
c0115606 | 4170 | usepirqmask [X86] Honor the possible IRQ mask stored |
a9913044 RD |
4171 | in the BIOS $PIR table. This is needed on |
4172 | some systems with broken BIOSes, notably | |
4173 | some HP Pavilion N5400 and Omnibook XE3 | |
4174 | notebooks. This will have no effect if ACPI | |
4175 | IRQ routing is enabled. | |
c0115606 | 4176 | noacpi [X86] Do not use ACPI for IRQ routing |
a9913044 | 4177 | or for PCI scanning. |
7bc5e3f2 BH |
4178 | use_crs [X86] Use PCI host bridge window information |
4179 | from ACPI. On BIOSes from 2008 or later, this | |
4180 | is enabled by default. If you need to use this, | |
4181 | please report a bug. | |
4182 | nocrs [X86] Ignore PCI host bridge windows from ACPI. | |
6dddd7a7 | 4183 | If you need to use this, please report a bug. |
fa6dae5d HG |
4184 | use_e820 [X86] Use E820 reservations to exclude parts of |
4185 | PCI host bridge windows. This is a workaround | |
4186 | for BIOS defects in host bridge _CRS methods. | |
4187 | If you need to use this, please report a bug to | |
4188 | <linux-pci@vger.kernel.org>. | |
4189 | no_e820 [X86] Ignore E820 reservations for PCI host | |
4190 | bridge windows. This is the default on modern | |
4191 | hardware. If you need to use this, please report | |
4192 | a bug to <linux-pci@vger.kernel.org>. | |
a9913044 RD |
4193 | routeirq Do IRQ routing for all PCI devices. |
4194 | This is normally done in pci_enable_device(), | |
4195 | so this option is a temporary workaround | |
4196 | for broken drivers that don't call it. | |
13a6ddb0 YL |
4197 | skip_isa_align [X86] do not align io start addr, so can |
4198 | handle more pci cards | |
0637a70a AK |
4199 | noearly [X86] Don't do any early type 1 scanning. |
4200 | This might help on some broken boards which | |
4201 | machine check when some devices' config space | |
4202 | is read. But various workarounds are disabled | |
4203 | and some IOMMU drivers will not work. | |
6b4b78fe MD |
4204 | bfsort Sort PCI devices into breadth-first order. |
4205 | This sorting is done to get a device | |
4206 | order compatible with older (<= 2.4) kernels. | |
4207 | nobfsort Don't sort PCI devices into breadth-first order. | |
fa238712 YW |
4208 | pcie_bus_tune_off Disable PCIe MPS (Max Payload Size) |
4209 | tuning and use the BIOS-configured MPS defaults. | |
4210 | pcie_bus_safe Set every device's MPS to the largest value | |
4211 | supported by all devices below the root complex. | |
4212 | pcie_bus_perf Set device MPS to the largest allowable MPS | |
4213 | based on its parent bus. Also set MRRS (Max | |
4214 | Read Request Size) to the largest supported | |
4215 | value (no larger than the MPS that the device | |
4216 | or bus can support) for best performance. | |
4217 | pcie_bus_peer2peer Set every device's MPS to 128B, which | |
4218 | every device is guaranteed to support. This | |
4219 | configuration allows peer-to-peer DMA between | |
4220 | any pair of devices, possibly at the cost of | |
4221 | reduced performance. This also guarantees | |
4222 | that hot-added devices will work. | |
4516a618 AN |
4223 | cbiosize=nn[KMG] The fixed amount of bus space which is |
4224 | reserved for the CardBus bridge's IO window. | |
4225 | The default value is 256 bytes. | |
4226 | cbmemsize=nn[KMG] The fixed amount of bus space which is | |
4227 | reserved for the CardBus bridge's memory | |
4228 | window. The default value is 64 megabytes. | |
32a9a682 YS |
4229 | resource_alignment= |
4230 | Format: | |
07d8d7e5 | 4231 | [<order of align>@]<pci_dev>[; ...] |
32a9a682 | 4232 | Specifies alignment and device to reassign |
07d8d7e5 LG |
4233 | aligned memory resources. How to |
4234 | specify the device is described above. | |
32a9a682 YS |
4235 | If <order of align> is not specified, |
4236 | PAGE_SIZE is used as alignment. | |
3b1b1ce3 | 4237 | A PCI-PCI bridge can be specified if resource |
32a9a682 | 4238 | windows need to be expanded. |
8b078c60 MK |
4239 | To specify the alignment for several |
4240 | instances of a device, the PCI vendor, | |
4241 | device, subvendor, and subdevice may be | |
3b1b1ce3 AK |
4242 | specified, e.g., 12@pci:8086:9c22:103c:198f |
4243 | for 4096-byte alignment. | |
43c16408 AP |
4244 | ecrc= Enable/disable PCIe ECRC (transaction layer |
4245 | end-to-end CRC checking). | |
4246 | bios: Use BIOS/firmware settings. This is the | |
4247 | the default. | |
4248 | off: Turn ECRC off | |
4249 | on: Turn ECRC on. | |
8c8803c5 YW |
4250 | hpiosize=nn[KMG] The fixed amount of bus space which is |
4251 | reserved for hotplug bridge's IO window. | |
4252 | Default size is 256 bytes. | |
d7b8a217 NJ |
4253 | hpmmiosize=nn[KMG] The fixed amount of bus space which is |
4254 | reserved for hotplug bridge's MMIO window. | |
4255 | Default size is 2 megabytes. | |
4256 | hpmmioprefsize=nn[KMG] The fixed amount of bus space which is | |
4257 | reserved for hotplug bridge's MMIO_PREF window. | |
4258 | Default size is 2 megabytes. | |
8c8803c5 | 4259 | hpmemsize=nn[KMG] The fixed amount of bus space which is |
d7b8a217 NJ |
4260 | reserved for hotplug bridge's MMIO and |
4261 | MMIO_PREF window. | |
8c8803c5 | 4262 | Default size is 2 megabytes. |
e16b4660 KB |
4263 | hpbussize=nn The minimum amount of additional bus numbers |
4264 | reserved for buses below a hotplug bridge. | |
4265 | Default is 1. | |
b55438fd YL |
4266 | realloc= Enable/disable reallocating PCI bridge resources |
4267 | if allocations done by BIOS are too small to | |
4268 | accommodate resources required by all child | |
4269 | devices. | |
4270 | off: Turn realloc off | |
4271 | on: Turn realloc on | |
4272 | realloc same as realloc=on | |
6748dcc2 | 4273 | noari do not use PCIe ARI. |
cef74409 GK |
4274 | noats [PCIE, Intel-IOMMU, AMD-IOMMU] |
4275 | do not use PCIe ATS (and IOMMU device IOTLB). | |
284f5f9d BH |
4276 | pcie_scan_all Scan all possible PCIe devices. Otherwise we |
4277 | only look for one device below a PCIe downstream | |
4278 | port. | |
f32ab754 UCCB |
4279 | big_root_window Try to add a big 64bit memory window to the PCIe |
4280 | root complex on AMD CPUs. Some GFX hardware | |
4281 | can resize a BAR to allow access to all VRAM. | |
4282 | Adding the window is slightly risky (it may | |
4283 | conflict with unreported devices), so this | |
4284 | taints the kernel. | |
aaca43fd LG |
4285 | disable_acs_redir=<pci_dev>[; ...] |
4286 | Specify one or more PCI devices (in the format | |
4287 | specified above) separated by semicolons. | |
4288 | Each device specified will have the PCI ACS | |
4289 | redirect capabilities forced off which will | |
4290 | allow P2P traffic between devices through | |
4291 | bridges without forcing it upstream. Note: | |
4292 | this removes isolation between devices and | |
4293 | may put more devices in an IOMMU group. | |
fbfe07d4 | 4294 | force_floating [S390] Force usage of floating interrupts. |
56271303 | 4295 | nomio [S390] Do not use MIO instructions. |
de267a7c PM |
4296 | norid [S390] ignore the RID field and force use of |
4297 | one PCI domain per PCI function | |
6b4b78fe | 4298 | |
e5665a45 CE |
4299 | pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power |
4300 | Management. | |
4301 | off Disable ASPM. | |
4302 | force Enable ASPM even on devices that claim not to support it. | |
4303 | WARNING: Forcing ASPM on may cause system lockups. | |
4304 | ||
4c0fd764 BH |
4305 | pcie_ports= [PCIE] PCIe port services handling: |
4306 | native Use native PCIe services (PME, AER, DPC, PCIe hotplug) | |
4307 | even if the platform doesn't give the OS permission to | |
4308 | use them. This may cause conflicts if the platform | |
4309 | also tries to use these services. | |
35a0b237 OJ |
4310 | dpc-native Use native PCIe service for DPC only. May |
4311 | cause conflicts if firmware uses AER or DPC. | |
4c0fd764 BH |
4312 | compat Disable native PCIe services (PME, AER, DPC, PCIe |
4313 | hotplug). | |
79dd9182 | 4314 | |
9d26d3a8 MW |
4315 | pcie_port_pm= [PCIE] PCIe port power management handling: |
4316 | off Disable power management of all PCIe ports | |
4317 | force Forcibly enable power management of all PCIe ports | |
4318 | ||
c7f48656 | 4319 | pcie_pme= [PCIE,PM] Native PCIe PME signaling options: |
c39fae14 | 4320 | nomsi Do not use MSI for native PCIe PME signaling (this makes |
28eb5f27 | 4321 | all PCIe root ports use INTx for all services). |
c7f48656 | 4322 | |
1da177e4 LT |
4323 | pcmv= [HW,PCMCIA] BadgePAD 4 |
4324 | ||
39ac5ba5 TB |
4325 | pd_ignore_unused |
4326 | [PM] | |
4327 | Keep all power-domains already enabled by bootloader on, | |
4328 | even if no driver has claimed them. This is useful | |
4329 | for debug and development, but should not be | |
4330 | needed on a platform with proper driver support. | |
4331 | ||
1da177e4 | 4332 | pd. [PARIDE] |
e7751617 | 4333 | See Documentation/admin-guide/blockdev/paride.rst. |
1da177e4 LT |
4334 | |
4335 | pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at | |
4336 | boot time. | |
4337 | Format: { 0 | 1 } | |
4338 | See arch/parisc/kernel/pdc_chassis.c | |
4339 | ||
f58dc01b | 4340 | percpu_alloc= Select which percpu first chunk allocator to use. |
e933a73f TH |
4341 | Currently supported values are "embed" and "page". |
4342 | Archs may support subset or none of the selections. | |
4343 | See comments in mm/percpu.c for details on each | |
4344 | allocator. This parameter is primarily for debugging | |
4345 | and performance comparison. | |
fa8a7094 | 4346 | |
1da177e4 | 4347 | pf. [PARIDE] |
e7751617 | 4348 | See Documentation/admin-guide/blockdev/paride.rst. |
1da177e4 LT |
4349 | |
4350 | pg. [PARIDE] | |
e7751617 | 4351 | See Documentation/admin-guide/blockdev/paride.rst. |
1da177e4 LT |
4352 | |
4353 | pirq= [SMP,APIC] Manual mp-table setup | |
cb1aaebe | 4354 | See Documentation/x86/i386/IO-APIC.rst. |
1da177e4 LT |
4355 | |
4356 | plip= [PPT,NET] Parallel port network link | |
4357 | Format: { parport<nr> | timid | 0 } | |
3ba9b1b8 | 4358 | See also Documentation/admin-guide/parport.rst. |
1da177e4 | 4359 | |
16290246 | 4360 | pmtmr= [X86] Manual setup of pmtmr I/O Port. |
de32a243 TG |
4361 | Override pmtimer IOPort with a hex value. |
4362 | e.g. pmtmr=0x508 | |
4363 | ||
0a4b4327 NP |
4364 | pmu_override= [PPC] Override the PMU. |
4365 | This option takes over the PMU facility, so it is no | |
4366 | longer usable by perf. Setting this option starts the | |
4367 | PMU counters by setting MMCR0 to 0 (the FC bit is | |
4368 | cleared). If a number is given, then MMCR1 is set to | |
4369 | that number, otherwise (e.g., 'pmu_override=on'), MMCR1 | |
4370 | remains 0. | |
4371 | ||
db96a759 CY |
4372 | pm_debug_messages [SUSPEND,KNL] |
4373 | Enable suspend/resume debug messages during boot up. | |
4374 | ||
96242116 BH |
4375 | pnp.debug=1 [PNP] |
4376 | Enable PNP debug messages (depends on the | |
4377 | CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time | |
4378 | via /sys/module/pnp/parameters/debug. We always show | |
4379 | current resource usage; turning this on also shows | |
4380 | possible settings and some assignment information. | |
97ef062b | 4381 | |
1da177e4 LT |
4382 | pnpacpi= [ACPI] |
4383 | { off } | |
4384 | ||
4385 | pnpbios= [ISAPNP] | |
4386 | { on | off | curr | res | no-curr | no-res } | |
4387 | ||
4388 | pnp_reserve_irq= | |
4389 | [ISAPNP] Exclude IRQs for the autoconfiguration | |
4390 | ||
4391 | pnp_reserve_dma= | |
4392 | [ISAPNP] Exclude DMAs for the autoconfiguration | |
4393 | ||
4394 | pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration | |
a9913044 | 4395 | Ranges are in pairs (I/O port base and size). |
1da177e4 LT |
4396 | |
4397 | pnp_reserve_mem= | |
a9913044 RD |
4398 | [ISAPNP] Exclude memory regions for the |
4399 | autoconfiguration. | |
1da177e4 LT |
4400 | Ranges are in pairs (memory base and size). |
4401 | ||
4af94f39 RD |
4402 | ports= [IP_VS_FTP] IPVS ftp helper module |
4403 | Default is 21. | |
4404 | Up to 8 (IP_VS_APP_MAX_PORTS) ports | |
4405 | may be specified. | |
4406 | Format: <port>,<port>.... | |
4407 | ||
c3cbd075 BS |
4408 | powersave=off [PPC] This option disables power saving features. |
4409 | It specifically disables cpuidle and sets the | |
4410 | platform machine description specific power_save | |
4411 | function to NULL. On Idle the CPU just reduces | |
4412 | execution priority. | |
4413 | ||
3eb5d588 AB |
4414 | ppc_strict_facility_enable |
4415 | [PPC] This option catches any kernel floating point, | |
4416 | Altivec, VSX and SPE outside of regions specifically | |
4417 | allowed (eg kernel_enable_fpu()/kernel_disable_fpu()). | |
4418 | There is some performance impact when enabling this. | |
4419 | ||
07fd1761 CB |
4420 | ppc_tm= [PPC] |
4421 | Format: {"off"} | |
4422 | Disable Hardware Transactional Memory | |
4423 | ||
6ef869e0 MH |
4424 | preempt= [KNL] |
4425 | Select preemption mode if you have CONFIG_PREEMPT_DYNAMIC | |
4426 | none - Limited to cond_resched() calls | |
4427 | voluntary - Limited to cond_resched() and might_sleep() calls | |
4428 | full - Any section that isn't explicitly preempt disabled | |
4429 | can be preempted anytime. | |
4430 | ||
45807a1d IM |
4431 | print-fatal-signals= |
4432 | [KNL] debug: print fatal signals | |
f84d49b2 NO |
4433 | |
4434 | If enabled, warn about various signal handling | |
4435 | related application anomalies: too many signals, | |
4436 | too many POSIX.1 timers, fatal signals causing a | |
4437 | coredump - etc. | |
4438 | ||
4439 | If you hit the warning due to signal overflow, | |
4440 | you might want to try "ulimit -i unlimited". | |
4441 | ||
45807a1d IM |
4442 | default: off. |
4443 | ||
c22ab332 MG |
4444 | printk.always_kmsg_dump= |
4445 | Trigger kmsg_dump for cases other than kernel oops or | |
4446 | panics | |
4447 | Format: <bool> (1/Y/y=enable, 0/N/n=disable) | |
4448 | default: disabled | |
4449 | ||
10102a89 DS |
4450 | printk.console_no_auto_verbose= |
4451 | Disable console loglevel raise on oops, panic | |
4452 | or lockdep-detected issues (only if lock debug is on). | |
4453 | With an exception to setups with low baudrate on | |
4454 | serial console, keeping this 0 is a good choice | |
4455 | in order to provide more debug information. | |
4456 | Format: <bool> | |
4457 | default: 0 (auto_verbose is enabled) | |
4458 | ||
750afe7b BP |
4459 | printk.devkmsg={on,off,ratelimit} |
4460 | Control writing to /dev/kmsg. | |
4461 | on - unlimited logging to /dev/kmsg from userspace | |
4462 | off - logging to /dev/kmsg disabled | |
4463 | ratelimit - ratelimit the logging | |
4464 | Default: ratelimit | |
4465 | ||
e84845c4 RD |
4466 | printk.time= Show timing data prefixed to each printk message line |
4467 | Format: <bool> (1/Y/y=enable, 0/N/n=disable) | |
4468 | ||
0cb55ad2 RD |
4469 | processor.max_cstate= [HW,ACPI] |
4470 | Limit processor to maximum C-state | |
4471 | max_cstate=9 overrides any DMI blacklist limit. | |
4472 | ||
4473 | processor.nocst [HW,ACPI] | |
4474 | Ignore the _CST method to determine C-states, | |
4475 | instead using the legacy FADT method | |
4476 | ||
1da177e4 | 4477 | profile= [KNL] Enable kernel profiling via /proc/profile |
e7e61fc0 RD |
4478 | Format: [<profiletype>,]<number> |
4479 | Param: <profiletype>: "schedule", "sleep", or "kvm" | |
4480 | [defaults to kernel profiling] | |
a9913044 | 4481 | Param: "schedule" - profile schedule points. |
b3da2a73 MG |
4482 | Param: "sleep" - profile D-state sleeping (millisecs). |
4483 | Requires CONFIG_SCHEDSTATS | |
c0fe2e69 | 4484 | Param: "kvm" - profile VM exits. |
e7e61fc0 RD |
4485 | Param: <number> - step/bucket size as a power of 2 for |
4486 | statistical time based profiling. | |
1da177e4 | 4487 | |
6b99e6e6 | 4488 | prompt_ramdisk= [RAM] [Deprecated] |
1da177e4 | 4489 | |
ecdc5d84 VG |
4490 | prot_virt= [S390] enable hosting protected virtual machines |
4491 | isolated from the hypervisor (if hardware supports | |
4492 | that). | |
4493 | Format: <bool> | |
4494 | ||
e0c27447 JW |
4495 | psi= [KNL] Enable or disable pressure stall information |
4496 | tracking. | |
4497 | Format: <bool> | |
4498 | ||
a9913044 RD |
4499 | psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to |
4500 | probe for; one of (bare|imps|exps|lifebook|any). | |
1da177e4 LT |
4501 | psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports |
4502 | per second. | |
a9913044 RD |
4503 | psmouse.resetafter= [HW,MOUSE] |
4504 | Try to reset the device after so many bad packets | |
1da177e4 LT |
4505 | (0 = never). |
4506 | psmouse.resolution= | |
4507 | [HW,MOUSE] Set desired mouse resolution, in dpi. | |
4508 | psmouse.smartscroll= | |
a9913044 | 4509 | [HW,MOUSE] Controls Logitech smartscroll autorepeat. |
1da177e4 LT |
4510 | 0 = disabled, 1 = enabled (default). |
4511 | ||
dee28e72 MG |
4512 | pstore.backend= Specify the name of the pstore backend to use |
4513 | ||
1da177e4 | 4514 | pt. [PARIDE] |
e7751617 | 4515 | See Documentation/admin-guide/blockdev/paride.rst. |
1da177e4 | 4516 | |
be3a5b0e | 4517 | pti= [X86-64] Control Page Table Isolation of user and |
01c9b17b DH |
4518 | kernel address spaces. Disabling this feature |
4519 | removes hardening, but improves performance of | |
4520 | system calls and interrupts. | |
4521 | ||
4522 | on - unconditionally enable | |
4523 | off - unconditionally disable | |
4524 | auto - kernel detects whether your CPU model is | |
4525 | vulnerable to issues that PTI mitigates | |
4526 | ||
4527 | Not specifying this option is equivalent to pti=auto. | |
4528 | ||
be3a5b0e | 4529 | nopti [X86-64] |
01c9b17b | 4530 | Equivalent to pti=off |
41f4c20b | 4531 | |
dc8c8587 KS |
4532 | pty.legacy_count= |
4533 | [KNL] Number of legacy pty's. Overwrites compiled-in | |
4534 | default number. | |
4535 | ||
7d2c502f | 4536 | quiet [KNL] Disable most log messages |
a9913044 | 4537 | |
1da177e4 LT |
4538 | r128= [HW,DRM] |
4539 | ||
4540 | raid= [HW,RAID] | |
e52347bd | 4541 | See Documentation/admin-guide/md.rst. |
1da177e4 | 4542 | |
1da177e4 | 4543 | ramdisk_size= [RAM] Sizes of RAM disks in kilobytes |
e7751617 | 4544 | See Documentation/admin-guide/blockdev/ramdisk.rst. |
1da177e4 | 4545 | |
6b99e6e6 RD |
4546 | ramdisk_start= [RAM] RAM disk image start address |
4547 | ||
9b254366 KC |
4548 | random.trust_cpu={on,off} |
4549 | [KNL] Enable or disable trusting the use of the | |
4550 | CPU's random number generator (if available) to | |
4551 | fully seed the kernel's CRNG. Default is controlled | |
4552 | by CONFIG_RANDOM_TRUST_CPU. | |
4553 | ||
d97c68d1 JD |
4554 | random.trust_bootloader={on,off} |
4555 | [KNL] Enable or disable trusting the use of a | |
4556 | seed passed by the bootloader (if available) to | |
4557 | fully seed the kernel's CRNG. Default is controlled | |
4558 | by CONFIG_RANDOM_TRUST_BOOTLOADER. | |
4559 | ||
39218ff4 KC |
4560 | randomize_kstack_offset= |
4561 | [KNL] Enable or disable kernel stack offset | |
4562 | randomization, which provides roughly 5 bits of | |
4563 | entropy, frustrating memory corruption attacks | |
4564 | that depend on stack address determinism or | |
4565 | cross-syscall address exposures. This is only | |
4566 | available on architectures that have defined | |
4567 | CONFIG_HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET. | |
4568 | Format: <bool> (1/Y/y=enable, 0/N/n=disable) | |
4569 | Default is CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT. | |
4570 | ||
011d8261 BP |
4571 | ras=option[,option,...] [KNL] RAS-specific options |
4572 | ||
4573 | cec_disable [X86] | |
4574 | Disable the Correctable Errors Collector, | |
4575 | see CONFIG_RAS_CEC help text. | |
4576 | ||
d2cf0854 FW |
4577 | rcu_nocbs[=cpu-list] |
4578 | [KNL] The optional argument is a cpu list, | |
4579 | as described above. | |
4580 | ||
4581 | In kernels built with CONFIG_RCU_NOCB_CPU=y, | |
4582 | enable the no-callback CPU mode, which prevents | |
4583 | such CPUs' callbacks from being invoked in | |
4584 | softirq context. Invocation of such CPUs' RCU | |
4585 | callbacks will instead be offloaded to "rcuox/N" | |
4586 | kthreads created for that purpose, where "x" is | |
4587 | "p" for RCU-preempt, "s" for RCU-sched, and "g" | |
4588 | for the kthreads that mediate grace periods; and | |
4589 | "N" is the CPU number. This reduces OS jitter on | |
4590 | the offloaded CPUs, which can be useful for HPC | |
4591 | and real-time workloads. It can also improve | |
4592 | energy efficiency for asymmetric multiprocessors. | |
4593 | ||
4594 | If a cpulist is passed as an argument, the specified | |
4595 | list of CPUs is set to no-callback mode from boot. | |
4596 | ||
4597 | Otherwise, if the '=' sign and the cpulist | |
4598 | arguments are omitted, no CPU will be set to | |
4599 | no-callback mode from boot but the mode may be | |
4600 | toggled at runtime via cpusets. | |
3fbfbf7a | 4601 | |
b37a667c JF |
4602 | Note that this argument takes precedence over |
4603 | the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option. | |
4604 | ||
4102adab | 4605 | rcu_nocb_poll [KNL] |
3fbfbf7a PM |
4606 | Rather than requiring that offloaded CPUs |
4607 | (specified by rcu_nocbs= above) explicitly | |
4608 | awaken the corresponding "rcuoN" kthreads, | |
4609 | make these kthreads poll for callbacks. | |
4610 | This improves the real-time response for the | |
4611 | offloaded CPUs by relieving them of the need to | |
4612 | wake up the corresponding kthread, but degrades | |
4613 | energy efficiency by requiring that the kthreads | |
4614 | periodically wake up to do the polling. | |
4615 | ||
4102adab | 4616 | rcutree.blimit= [KNL] |
97e63f0c PM |
4617 | Set maximum number of finished RCU callbacks to |
4618 | process in one batch. | |
21a1ea9e | 4619 | |
a3dc2948 PM |
4620 | rcutree.dump_tree= [KNL] |
4621 | Dump the structure of the rcu_node combining tree | |
4622 | out at early boot. This is used for diagnostic | |
4623 | purposes, to verify correct tree setup. | |
4624 | ||
0f41c0dd PM |
4625 | rcutree.gp_cleanup_delay= [KNL] |
4626 | Set the number of jiffies to delay each step of | |
90040c9e | 4627 | RCU grace-period cleanup. |
0f41c0dd | 4628 | |
37745d28 PM |
4629 | rcutree.gp_init_delay= [KNL] |
4630 | Set the number of jiffies to delay each step of | |
90040c9e | 4631 | RCU grace-period initialization. |
0f41c0dd PM |
4632 | |
4633 | rcutree.gp_preinit_delay= [KNL] | |
4634 | Set the number of jiffies to delay each step of | |
4635 | RCU grace-period pre-initialization, that is, | |
4636 | the propagation of recent CPU-hotplug changes up | |
90040c9e | 4637 | the rcu_node combining tree. |
37745d28 | 4638 | |
48d07c04 SAS |
4639 | rcutree.use_softirq= [KNL] |
4640 | If set to zero, move all RCU_SOFTIRQ processing to | |
4641 | per-CPU rcuc kthreads. Defaults to a non-zero | |
4642 | value, meaning that RCU_SOFTIRQ is used by default. | |
4643 | Specify rcutree.use_softirq=0 to use rcuc kthreads. | |
4644 | ||
8b9a0ecc SW |
4645 | But note that CONFIG_PREEMPT_RT=y kernels disable |
4646 | this kernel boot parameter, forcibly setting it | |
4647 | to zero. | |
4648 | ||
7fa27001 PM |
4649 | rcutree.rcu_fanout_exact= [KNL] |
4650 | Disable autobalancing of the rcu_node combining | |
4651 | tree. This is used by rcutorture, and might | |
4652 | possibly be useful for architectures having high | |
4653 | cache-to-cache transfer latencies. | |
37745d28 | 4654 | |
4102adab | 4655 | rcutree.rcu_fanout_leaf= [KNL] |
ee968ac6 PM |
4656 | Change the number of CPUs assigned to each |
4657 | leaf rcu_node structure. Useful for very | |
4658 | large systems, which will choose the value 64, | |
4659 | and for NUMA systems with large remote-access | |
4660 | latencies, which will choose a value aligned | |
4661 | with the appropriate hardware boundaries. | |
f885b7f2 | 4662 | |
53c72b59 URS |
4663 | rcutree.rcu_min_cached_objs= [KNL] |
4664 | Minimum number of objects which are cached and | |
4665 | maintained per one CPU. Object size is equal | |
4666 | to PAGE_SIZE. The cache allows to reduce the | |
4667 | pressure to page allocator, also it makes the | |
4668 | whole algorithm to behave better in low memory | |
4669 | condition. | |
4670 | ||
d0bfa8b3 ZQ |
4671 | rcutree.rcu_delay_page_cache_fill_msec= [KNL] |
4672 | Set the page-cache refill delay (in milliseconds) | |
4673 | in response to low-memory conditions. The range | |
4674 | of permitted values is in the range 0:100000. | |
4675 | ||
4102adab | 4676 | rcutree.jiffies_till_first_fqs= [KNL] |
c0f4dfd4 PM |
4677 | Set delay from grace-period initialization to |
4678 | first attempt to force quiescent states. | |
4679 | Units are jiffies, minimum value is zero, | |
4680 | and maximum value is HZ. | |
4681 | ||
4102adab | 4682 | rcutree.jiffies_till_next_fqs= [KNL] |
c0f4dfd4 PM |
4683 | Set delay between subsequent attempts to force |
4684 | quiescent states. Units are jiffies, minimum | |
4685 | value is one, and maximum value is HZ. | |
4686 | ||
1a4762b9 PM |
4687 | rcutree.jiffies_till_sched_qs= [KNL] |
4688 | Set required age in jiffies for a | |
4689 | given grace period before RCU starts | |
4690 | soliciting quiescent-state help from | |
4691 | rcu_note_context_switch() and cond_resched(). | |
4692 | If not specified, the kernel will calculate | |
4693 | a value based on the most recent settings | |
4694 | of rcutree.jiffies_till_first_fqs | |
4695 | and rcutree.jiffies_till_next_fqs. | |
4696 | This calculated value may be viewed in | |
4697 | rcutree.jiffies_to_sched_qs. Any attempt to set | |
4698 | rcutree.jiffies_to_sched_qs will be cheerfully | |
4699 | overwritten. | |
4700 | ||
21871d7e | 4701 | rcutree.kthread_prio= [KNL,BOOT] |
d2af1ad7 PM |
4702 | Set the SCHED_FIFO priority of the RCU per-CPU |
4703 | kthreads (rcuc/N). This value is also used for | |
4704 | the priority of the RCU boost threads (rcub/N) | |
4705 | and for the RCU grace-period kthreads (rcu_bh, | |
4706 | rcu_preempt, and rcu_sched). If RCU_BOOST is | |
4707 | set, valid values are 1-99 and the default is 1 | |
4708 | (the least-favored priority). Otherwise, when | |
4709 | RCU_BOOST is not set, valid values are 0-99 and | |
4710 | the default is zero (non-realtime operation). | |
a469948b AC |
4711 | When RCU_NOCB_CPU is set, also adjust the |
4712 | priority of NOCB callback kthreads. | |
21871d7e | 4713 | |
71de1e34 PM |
4714 | rcutree.rcu_divisor= [KNL] |
4715 | Set the shift-right count to use to compute | |
4716 | the callback-invocation batch limit bl from | |
4717 | the number of callbacks queued on this CPU. | |
4718 | The result will be bounded below by the value of | |
4719 | the rcutree.blimit kernel parameter. Every bl | |
4720 | callbacks, the softirq handler will exit in | |
4721 | order to allow the CPU to do other work. | |
4722 | ||
4723 | Please note that this callback-invocation batch | |
4724 | limit applies only to non-offloaded callback | |
4725 | invocation. Offloaded callbacks are instead | |
4726 | invoked in the context of an rcuoc kthread, which | |
4727 | scheduler will preempt as it does any other task. | |
4728 | ||
89f7f291 PM |
4729 | rcutree.nocb_nobypass_lim_per_jiffy= [KNL] |
4730 | On callback-offloaded (rcu_nocbs) CPUs, | |
4731 | RCU reduces the lock contention that would | |
4732 | otherwise be caused by callback floods through | |
4733 | use of the ->nocb_bypass list. However, in the | |
4734 | common non-flooded case, RCU queues directly to | |
4735 | the main ->cblist in order to avoid the extra | |
4736 | overhead of the ->nocb_bypass list and its lock. | |
4737 | But if there are too many callbacks queued during | |
4738 | a single jiffy, RCU pre-queues the callbacks into | |
4739 | the ->nocb_bypass queue. The definition of "too | |
4740 | many" is supplied by this kernel boot parameter. | |
4741 | ||
f7c612b0 PM |
4742 | rcutree.rcu_nocb_gp_stride= [KNL] |
4743 | Set the number of NOCB callback kthreads in | |
4744 | each group, which defaults to the square root | |
4745 | of the number of CPUs. Larger numbers reduce | |
4746 | the wakeup overhead on the global grace-period | |
4747 | kthread, but increases that same overhead on | |
4748 | each group's NOCB grace-period kthread. | |
fbce7497 | 4749 | |
4102adab | 4750 | rcutree.qhimark= [KNL] |
97e63f0c PM |
4751 | Set threshold of queued RCU callbacks beyond which |
4752 | batch limiting is disabled. | |
21a1ea9e | 4753 | |
4102adab | 4754 | rcutree.qlowmark= [KNL] |
24aaef8d RD |
4755 | Set threshold of queued RCU callbacks below which |
4756 | batch limiting is re-enabled. | |
21a1ea9e | 4757 | |
b2b00ddf PM |
4758 | rcutree.qovld= [KNL] |
4759 | Set threshold of queued RCU callbacks beyond which | |
4760 | RCU's force-quiescent-state scan will aggressively | |
4761 | enlist help from cond_resched() and sched IPIs to | |
4762 | help CPUs more quickly reach quiescent states. | |
4763 | Set to less than zero to make this be set based | |
4764 | on rcutree.qhimark at boot time and to zero to | |
4765 | disable more aggressive help enlistment. | |
4766 | ||
e3c50dfb PM |
4767 | rcutree.rcu_kick_kthreads= [KNL] |
4768 | Cause the grace-period kthread to get an extra | |
4769 | wake_up() if it sleeps three times longer than | |
4770 | it should at force-quiescent-state time. | |
4771 | This wake_up() will be accompanied by a | |
4772 | WARN_ONCE() splat and an ftrace_dump(). | |
4773 | ||
3d29aaf1 PM |
4774 | rcutree.rcu_unlock_delay= [KNL] |
4775 | In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels, | |
4776 | this specifies an rcu_read_unlock()-time delay | |
4777 | in microseconds. This defaults to zero. | |
4778 | Larger delays increase the probability of | |
4779 | catching RCU pointer leaks, that is, buggy use | |
4780 | of RCU-protected pointers after the relevant | |
4781 | rcu_read_unlock() has completed. | |
4782 | ||
2ccaff10 PM |
4783 | rcutree.sysrq_rcu= [KNL] |
4784 | Commandeer a sysrq key to dump out Tree RCU's | |
4785 | rcu_node tree with an eye towards determining | |
4786 | why a new grace period has not yet started. | |
4787 | ||
4e88ec4a | 4788 | rcuscale.gp_async= [KNL] |
881ed593 PM |
4789 | Measure performance of asynchronous |
4790 | grace-period primitives such as call_rcu(). | |
4791 | ||
4e88ec4a | 4792 | rcuscale.gp_async_max= [KNL] |
881ed593 PM |
4793 | Specify the maximum number of outstanding |
4794 | callbacks per writer thread. When a writer | |
4795 | thread exceeds this limit, it invokes the | |
4796 | corresponding flavor of rcu_barrier() to allow | |
4797 | previously posted callbacks to drain. | |
4798 | ||
4e88ec4a | 4799 | rcuscale.gp_exp= [KNL] |
bdea9e34 PM |
4800 | Measure performance of expedited synchronous |
4801 | grace-period primitives. | |
4802 | ||
4e88ec4a | 4803 | rcuscale.holdoff= [KNL] |
df37e66b PM |
4804 | Set test-start holdoff period. The purpose of |
4805 | this parameter is to delay the start of the | |
4806 | test until boot completes in order to avoid | |
4807 | interference. | |
4808 | ||
4e88ec4a | 4809 | rcuscale.kfree_rcu_test= [KNL] |
e6e78b00 JFG |
4810 | Set to measure performance of kfree_rcu() flooding. |
4811 | ||
686fe1bf URS |
4812 | rcuscale.kfree_rcu_test_double= [KNL] |
4813 | Test the double-argument variant of kfree_rcu(). | |
4814 | If this parameter has the same value as | |
4815 | rcuscale.kfree_rcu_test_single, both the single- | |
4816 | and double-argument variants are tested. | |
4817 | ||
4818 | rcuscale.kfree_rcu_test_single= [KNL] | |
4819 | Test the single-argument variant of kfree_rcu(). | |
4820 | If this parameter has the same value as | |
4821 | rcuscale.kfree_rcu_test_double, both the single- | |
4822 | and double-argument variants are tested. | |
4823 | ||
4e88ec4a | 4824 | rcuscale.kfree_nthreads= [KNL] |
e6e78b00 JFG |
4825 | The number of threads running loops of kfree_rcu(). |
4826 | ||
4e88ec4a | 4827 | rcuscale.kfree_alloc_num= [KNL] |
e6e78b00 JFG |
4828 | Number of allocations and frees done in an iteration. |
4829 | ||
4e88ec4a PM |
4830 | rcuscale.kfree_loops= [KNL] |
4831 | Number of loops doing rcuscale.kfree_alloc_num number | |
e6e78b00 JFG |
4832 | of allocations and frees. |
4833 | ||
4e88ec4a | 4834 | rcuscale.nreaders= [KNL] |
bdea9e34 PM |
4835 | Set number of RCU readers. The value -1 selects |
4836 | N, where N is the number of CPUs. A value | |
4837 | "n" less than -1 selects N-n+1, where N is again | |
4838 | the number of CPUs. For example, -2 selects N | |
4839 | (the number of CPUs), -3 selects N+1, and so on. | |
4840 | A value of "n" less than or equal to -N selects | |
4841 | a single reader. | |
4842 | ||
4e88ec4a | 4843 | rcuscale.nwriters= [KNL] |
bdea9e34 | 4844 | Set number of RCU writers. The values operate |
4e88ec4a | 4845 | the same as for rcuscale.nreaders. |
bdea9e34 PM |
4846 | N, where N is the number of CPUs |
4847 | ||
4e88ec4a | 4848 | rcuscale.perf_type= [KNL] |
820687a7 PM |
4849 | Specify the RCU implementation to test. |
4850 | ||
4e88ec4a | 4851 | rcuscale.shutdown= [KNL] |
bdea9e34 PM |
4852 | Shut the system down after performance tests |
4853 | complete. This is useful for hands-off automated | |
4854 | testing. | |
4855 | ||
4e88ec4a | 4856 | rcuscale.verbose= [KNL] |
bdea9e34 PM |
4857 | Enable additional printk() statements. |
4858 | ||
4e88ec4a | 4859 | rcuscale.writer_holdoff= [KNL] |
820687a7 PM |
4860 | Write-side holdoff between grace periods, |
4861 | in microseconds. The default of zero says | |
4862 | no holdoff. | |
4863 | ||
4102adab | 4864 | rcutorture.fqs_duration= [KNL] |
21b05de4 PM |
4865 | Set duration of force_quiescent_state bursts |
4866 | in microseconds. | |
dabb8aa9 | 4867 | |
4102adab | 4868 | rcutorture.fqs_holdoff= [KNL] |
21b05de4 PM |
4869 | Set holdoff time within force_quiescent_state bursts |
4870 | in microseconds. | |
dabb8aa9 | 4871 | |
4102adab | 4872 | rcutorture.fqs_stutter= [KNL] |
21b05de4 PM |
4873 | Set wait time between force_quiescent_state bursts |
4874 | in seconds. | |
4875 | ||
ed8f6fb2 | 4876 | rcutorture.fwd_progress= [KNL] |
82e31003 PM |
4877 | Specifies the number of kthreads to be used |
4878 | for RCU grace-period forward-progress testing | |
ed8f6fb2 | 4879 | for the types of RCU supporting this notion. |
82e31003 PM |
4880 | Defaults to 1 kthread, values less than zero or |
4881 | greater than the number of CPUs cause the number | |
4882 | of CPUs to be used. | |
ed8f6fb2 PM |
4883 | |
4884 | rcutorture.fwd_progress_div= [KNL] | |
4885 | Specify the fraction of a CPU-stall-warning | |
4886 | period to do tight-loop forward-progress testing. | |
4887 | ||
4888 | rcutorture.fwd_progress_holdoff= [KNL] | |
4889 | Number of seconds to wait between successive | |
4890 | forward-progress tests. | |
4891 | ||
4892 | rcutorture.fwd_progress_need_resched= [KNL] | |
4893 | Enclose cond_resched() calls within checks for | |
4894 | need_resched() during tight-loop forward-progress | |
4895 | testing. | |
4896 | ||
21b05de4 PM |
4897 | rcutorture.gp_cond= [KNL] |
4898 | Use conditional/asynchronous update-side | |
4899 | primitives, if available. | |
dabb8aa9 | 4900 | |
4102adab | 4901 | rcutorture.gp_exp= [KNL] |
21b05de4 | 4902 | Use expedited update-side primitives, if available. |
4102adab PM |
4903 | |
4904 | rcutorture.gp_normal= [KNL] | |
21b05de4 PM |
4905 | Use normal (non-expedited) asynchronous |
4906 | update-side primitives, if available. | |
4907 | ||
4908 | rcutorture.gp_sync= [KNL] | |
4909 | Use normal (non-expedited) synchronous | |
4910 | update-side primitives, if available. If all | |
4911 | of rcutorture.gp_cond=, rcutorture.gp_exp=, | |
4912 | rcutorture.gp_normal=, and rcutorture.gp_sync= | |
4913 | are zero, rcutorture acts as if is interpreted | |
4914 | they are all non-zero. | |
dabb8aa9 | 4915 | |
d6855142 PM |
4916 | rcutorture.irqreader= [KNL] |
4917 | Run RCU readers from irq handlers, or, more | |
4918 | accurately, from a timer handler. Not all RCU | |
4919 | flavors take kindly to this sort of thing. | |
4920 | ||
4921 | rcutorture.leakpointer= [KNL] | |
4922 | Leak an RCU-protected pointer out of the reader. | |
4923 | This can of course result in splats, and is | |
4924 | intended to test the ability of things like | |
4925 | CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect | |
4926 | such leaks. | |
4927 | ||
4102adab | 4928 | rcutorture.n_barrier_cbs= [KNL] |
dabb8aa9 PM |
4929 | Set callbacks/threads for rcu_barrier() testing. |
4930 | ||
4102adab | 4931 | rcutorture.nfakewriters= [KNL] |
dabb8aa9 PM |
4932 | Set number of concurrent RCU writers. These just |
4933 | stress RCU, they don't participate in the actual | |
4934 | test, hence the "fake". | |
4935 | ||
2c4319bd PM |
4936 | rcutorture.nocbs_nthreads= [KNL] |
4937 | Set number of RCU callback-offload togglers. | |
4938 | Zero (the default) disables toggling. | |
4939 | ||
4940 | rcutorture.nocbs_toggle= [KNL] | |
4941 | Set the delay in milliseconds between successive | |
4942 | callback-offload toggling attempts. | |
4943 | ||
4102adab | 4944 | rcutorture.nreaders= [KNL] |
3838cc18 PM |
4945 | Set number of RCU readers. The value -1 selects |
4946 | N-1, where N is the number of CPUs. A value | |
4947 | "n" less than -1 selects N-n-2, where N is again | |
4948 | the number of CPUs. For example, -2 selects N | |
4949 | (the number of CPUs), -3 selects N+1, and so on. | |
dabb8aa9 | 4950 | |
4102adab PM |
4951 | rcutorture.object_debug= [KNL] |
4952 | Enable debug-object double-call_rcu() testing. | |
4953 | ||
4954 | rcutorture.onoff_holdoff= [KNL] | |
dabb8aa9 PM |
4955 | Set time (s) after boot for CPU-hotplug testing. |
4956 | ||
4102adab | 4957 | rcutorture.onoff_interval= [KNL] |
028be12b PM |
4958 | Set time (jiffies) between CPU-hotplug operations, |
4959 | or zero to disable CPU-hotplug testing. | |
dabb8aa9 | 4960 | |
4a5f133c PM |
4961 | rcutorture.read_exit= [KNL] |
4962 | Set the number of read-then-exit kthreads used | |
4963 | to test the interaction of RCU updaters and | |
4964 | task-exit processing. | |
4965 | ||
4966 | rcutorture.read_exit_burst= [KNL] | |
4967 | The number of times in a given read-then-exit | |
4968 | episode that a set of read-then-exit kthreads | |
4969 | is spawned. | |
4970 | ||
4971 | rcutorture.read_exit_delay= [KNL] | |
4972 | The delay, in seconds, between successive | |
4973 | read-then-exit testing episodes. | |
4974 | ||
4102adab | 4975 | rcutorture.shuffle_interval= [KNL] |
dabb8aa9 PM |
4976 | Set task-shuffle interval (s). Shuffling tasks |
4977 | allows some CPUs to go into dyntick-idle mode | |
4978 | during the rcutorture test. | |
4979 | ||
4102adab | 4980 | rcutorture.shutdown_secs= [KNL] |
dabb8aa9 PM |
4981 | Set time (s) after boot system shutdown. This |
4982 | is useful for hands-off automated testing. | |
4983 | ||
4102adab | 4984 | rcutorture.stall_cpu= [KNL] |
dabb8aa9 PM |
4985 | Duration of CPU stall (s) to test RCU CPU stall |
4986 | warnings, zero to disable. | |
4987 | ||
19a8ff95 PM |
4988 | rcutorture.stall_cpu_block= [KNL] |
4989 | Sleep while stalling if set. This will result | |
4990 | in warnings from preemptible RCU in addition | |
4991 | to any other stall-related activity. | |
4992 | ||
4102adab | 4993 | rcutorture.stall_cpu_holdoff= [KNL] |
dabb8aa9 PM |
4994 | Time to wait (s) after boot before inducing stall. |
4995 | ||
2b1516e5 PM |
4996 | rcutorture.stall_cpu_irqsoff= [KNL] |
4997 | Disable interrupts while stalling if set. | |
4998 | ||
55b2dcf5 PM |
4999 | rcutorture.stall_gp_kthread= [KNL] |
5000 | Duration (s) of forced sleep within RCU | |
5001 | grace-period kthread to test RCU CPU stall | |
5002 | warnings, zero to disable. If both stall_cpu | |
5003 | and stall_gp_kthread are specified, the | |
5004 | kthread is starved first, then the CPU. | |
5005 | ||
4102adab | 5006 | rcutorture.stat_interval= [KNL] |
dabb8aa9 PM |
5007 | Time (s) between statistics printk()s. |
5008 | ||
4102adab | 5009 | rcutorture.stutter= [KNL] |
dabb8aa9 PM |
5010 | Time (s) to stutter testing, for example, specifying |
5011 | five seconds causes the test to run for five seconds, | |
5012 | wait for five seconds, and so on. This tests RCU's | |
5013 | ability to transition abruptly to and from idle. | |
5014 | ||
4102adab | 5015 | rcutorture.test_boost= [KNL] |
dabb8aa9 PM |
5016 | Test RCU priority boosting? 0=no, 1=maybe, 2=yes. |
5017 | "Maybe" means test if the RCU implementation | |
5018 | under test support RCU priority boosting. | |
5019 | ||
4102adab | 5020 | rcutorture.test_boost_duration= [KNL] |
dabb8aa9 PM |
5021 | Duration (s) of each individual boost test. |
5022 | ||
4102adab | 5023 | rcutorture.test_boost_interval= [KNL] |
dabb8aa9 PM |
5024 | Interval (s) between each boost test. |
5025 | ||
4102adab | 5026 | rcutorture.test_no_idle_hz= [KNL] |
dabb8aa9 PM |
5027 | Test RCU's dyntick-idle handling. See also the |
5028 | rcutorture.shuffle_interval parameter. | |
5029 | ||
4102adab | 5030 | rcutorture.torture_type= [KNL] |
dabb8aa9 PM |
5031 | Specify the RCU implementation to test. |
5032 | ||
4102adab | 5033 | rcutorture.verbose= [KNL] |
dabb8aa9 PM |
5034 | Enable additional printk() statements. |
5035 | ||
cdc694b2 PM |
5036 | rcupdate.rcu_cpu_stall_ftrace_dump= [KNL] |
5037 | Dump ftrace buffer after reporting RCU CPU | |
5038 | stall warning. | |
5039 | ||
5a9be7c6 PM |
5040 | rcupdate.rcu_cpu_stall_suppress= [KNL] |
5041 | Suppress RCU CPU stall warning messages. | |
5042 | ||
58c53360 PM |
5043 | rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL] |
5044 | Suppress RCU CPU stall warning messages and | |
5045 | rcutorture writer stall warnings that occur | |
5046 | during early boot, that is, during the time | |
5047 | before the init task is spawned. | |
5048 | ||
5a9be7c6 PM |
5049 | rcupdate.rcu_cpu_stall_timeout= [KNL] |
5050 | Set timeout for RCU CPU stall warning messages. | |
28b3ae42 UR |
5051 | The value is in seconds and the maximum allowed |
5052 | value is 300 seconds. | |
5053 | ||
5054 | rcupdate.rcu_exp_cpu_stall_timeout= [KNL] | |
5055 | Set timeout for expedited RCU CPU stall warning | |
5056 | messages. The value is in milliseconds | |
5057 | and the maximum allowed value is 21000 | |
5058 | milliseconds. Please note that this value is | |
5059 | adjusted to an arch timer tick resolution. | |
5060 | Setting this to zero causes the value from | |
5061 | rcupdate.rcu_cpu_stall_timeout to be used (after | |
5062 | conversion from seconds to milliseconds). | |
5a9be7c6 | 5063 | |
4102adab PM |
5064 | rcupdate.rcu_expedited= [KNL] |
5065 | Use expedited grace-period primitives, for | |
5066 | example, synchronize_rcu_expedited() instead | |
5067 | of synchronize_rcu(). This reduces latency, | |
5068 | but can increase CPU utilization, degrade | |
5069 | real-time latency, and degrade energy efficiency. | |
79cfea02 | 5070 | No effect on CONFIG_TINY_RCU kernels. |
4102adab | 5071 | |
5a9be7c6 PM |
5072 | rcupdate.rcu_normal= [KNL] |
5073 | Use only normal grace-period primitives, | |
5074 | for example, synchronize_rcu() instead of | |
5075 | synchronize_rcu_expedited(). This improves | |
79cfea02 PM |
5076 | real-time latency, CPU utilization, and |
5077 | energy efficiency, but can expose users to | |
5078 | increased grace-period latency. This parameter | |
5079 | overrides rcupdate.rcu_expedited. No effect on | |
5080 | CONFIG_TINY_RCU kernels. | |
4102adab | 5081 | |
3e42ec1a PM |
5082 | rcupdate.rcu_normal_after_boot= [KNL] |
5083 | Once boot has completed (that is, after | |
5084 | rcu_end_inkernel_boot() has been invoked), use | |
79cfea02 PM |
5085 | only normal grace-period primitives. No effect |
5086 | on CONFIG_TINY_RCU kernels. | |
3e42ec1a | 5087 | |
36221e10 JC |
5088 | But note that CONFIG_PREEMPT_RT=y kernels enables |
5089 | this kernel boot parameter, forcibly setting | |
5090 | it to the value one, that is, converting any | |
5091 | post-boot attempt at an expedited RCU grace | |
5092 | period to instead use normal non-expedited | |
5093 | grace-period processing. | |
5094 | ||
fd796e41 PM |
5095 | rcupdate.rcu_task_collapse_lim= [KNL] |
5096 | Set the maximum number of callbacks present | |
5097 | at the beginning of a grace period that allows | |
5098 | the RCU Tasks flavors to collapse back to using | |
5099 | a single callback queue. This switching only | |
5100 | occurs when rcupdate.rcu_task_enqueue_lim is | |
5101 | set to the default value of -1. | |
5102 | ||
ab97152f PM |
5103 | rcupdate.rcu_task_contend_lim= [KNL] |
5104 | Set the minimum number of callback-queuing-time | |
5105 | lock-contention events per jiffy required to | |
5106 | cause the RCU Tasks flavors to switch to per-CPU | |
5107 | callback queuing. This switching only occurs | |
5108 | when rcupdate.rcu_task_enqueue_lim is set to | |
5109 | the default value of -1. | |
5110 | ||
8610b656 PM |
5111 | rcupdate.rcu_task_enqueue_lim= [KNL] |
5112 | Set the number of callback queues to use for the | |
5113 | RCU Tasks family of RCU flavors. The default | |
5114 | of -1 allows this to be automatically (and | |
5115 | dynamically) adjusted. This parameter is intended | |
5116 | for use in testing. | |
5117 | ||
b0afa0f0 PM |
5118 | rcupdate.rcu_task_ipi_delay= [KNL] |
5119 | Set time in jiffies during which RCU tasks will | |
5120 | avoid sending IPIs, starting with the beginning | |
5121 | of a given grace period. Setting a large | |
5122 | number avoids disturbing real-time workloads, | |
5123 | but lengthens grace periods. | |
5124 | ||
f2539003 PM |
5125 | rcupdate.rcu_task_stall_info= [KNL] |
5126 | Set initial timeout in jiffies for RCU task stall | |
5127 | informational messages, which give some indication | |
5128 | of the problem for those not patient enough to | |
5129 | wait for ten minutes. Informational messages are | |
5130 | only printed prior to the stall-warning message | |
5131 | for a given grace period. Disable with a value | |
5132 | less than or equal to zero. Defaults to ten | |
5133 | seconds. A change in value does not take effect | |
5134 | until the beginning of the next grace period. | |
5135 | ||
5136 | rcupdate.rcu_task_stall_info_mult= [KNL] | |
5137 | Multiplier for time interval between successive | |
5138 | RCU task stall informational messages for a given | |
5139 | RCU tasks grace period. This value is clamped | |
5140 | to one through ten, inclusive. It defaults to | |
5141 | the value three, so that the first informational | |
5142 | message is printed 10 seconds into the grace | |
5143 | period, the second at 40 seconds, the third at | |
5144 | 160 seconds, and then the stall warning at 600 | |
5145 | seconds would prevent a fourth at 640 seconds. | |
5146 | ||
52db30ab | 5147 | rcupdate.rcu_task_stall_timeout= [KNL] |
f2539003 PM |
5148 | Set timeout in jiffies for RCU task stall |
5149 | warning messages. Disable with a value less | |
5150 | than or equal to zero. Defaults to ten minutes. | |
5151 | A change in value does not take effect until | |
5152 | the beginning of the next grace period. | |
52db30ab | 5153 | |
74860fee PK |
5154 | rcupdate.rcu_self_test= [KNL] |
5155 | Run the RCU early boot self tests | |
5156 | ||
ffdfc409 OJ |
5157 | rdinit= [KNL] |
5158 | Format: <full_path> | |
5159 | Run specified binary instead of /init from the ramdisk, | |
5160 | used for early userspace startup. See initrd. | |
5161 | ||
c49a0a80 TL |
5162 | rdrand= [X86] |
5163 | force - Override the decision by the kernel to hide the | |
5164 | advertisement of RDRAND support (this affects | |
5165 | certain AMD processors because of buggy BIOS | |
5166 | support, specifically around the suspend/resume | |
5167 | path). | |
5168 | ||
1d9807fc TL |
5169 | rdt= [HW,X86,RDT] |
5170 | Turn on/off individual RDT features. List is: | |
31516de3 FY |
5171 | cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp, |
5172 | mba. | |
1d9807fc TL |
5173 | E.g. to turn on cmt and turn off mba use: |
5174 | rdt=cmt,!mba | |
5175 | ||
1b3a5d02 RH |
5176 | reboot= [KNL] |
5177 | Format (x86 or x86_64): | |
12febc18 | 5178 | [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] | d[efault] \ |
1b3a5d02 RH |
5179 | [[,]s[mp]#### \ |
5180 | [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \ | |
5181 | [[,]f[orce] | |
b287a25a AK |
5182 | Where reboot_mode is one of warm (soft) or cold (hard) or gpio |
5183 | (prefix with 'panic_' to set mode for panic | |
5184 | reboot only), | |
1b3a5d02 RH |
5185 | reboot_type is one of bios, acpi, kbd, triple, efi, or pci, |
5186 | reboot_force is either force or not specified, | |
5187 | reboot_cpu is s[mp]#### with #### being the processor | |
5188 | to be used for rebooting. | |
1da177e4 | 5189 | |
1fbeb3a8 | 5190 | refscale.holdoff= [KNL] |
847dd70a PM |
5191 | Set test-start holdoff period. The purpose of |
5192 | this parameter is to delay the start of the | |
5193 | test until boot completes in order to avoid | |
5194 | interference. | |
5195 | ||
1fbeb3a8 | 5196 | refscale.loops= [KNL] |
847dd70a PM |
5197 | Set the number of loops over the synchronization |
5198 | primitive under test. Increasing this number | |
5199 | reduces noise due to loop start/end overhead, | |
5200 | but the default has already reduced the per-pass | |
5201 | noise to a handful of picoseconds on ca. 2020 | |
5202 | x86 laptops. | |
5203 | ||
1fbeb3a8 | 5204 | refscale.nreaders= [KNL] |
847dd70a PM |
5205 | Set number of readers. The default value of -1 |
5206 | selects N, where N is roughly 75% of the number | |
5207 | of CPUs. A value of zero is an interesting choice. | |
5208 | ||
1fbeb3a8 | 5209 | refscale.nruns= [KNL] |
847dd70a PM |
5210 | Set number of runs, each of which is dumped onto |
5211 | the console log. | |
5212 | ||
1fbeb3a8 | 5213 | refscale.readdelay= [KNL] |
847dd70a PM |
5214 | Set the read-side critical-section duration, |
5215 | measured in microseconds. | |
5216 | ||
1fbeb3a8 PM |
5217 | refscale.scale_type= [KNL] |
5218 | Specify the read-protection implementation to test. | |
5219 | ||
5220 | refscale.shutdown= [KNL] | |
847dd70a PM |
5221 | Shut down the system at the end of the performance |
5222 | test. This defaults to 1 (shut it down) when | |
4e88ec4a PM |
5223 | refscale is built into the kernel and to 0 (leave |
5224 | it running) when refscale is built as a module. | |
847dd70a | 5225 | |
1fbeb3a8 | 5226 | refscale.verbose= [KNL] |
847dd70a PM |
5227 | Enable additional printk() statements. |
5228 | ||
e76506f0 PM |
5229 | refscale.verbose_batched= [KNL] |
5230 | Batch the additional printk() statements. If zero | |
5231 | (the default) or negative, print everything. Otherwise, | |
5232 | print every Nth verbose statement, where N is the value | |
5233 | specified. | |
5234 | ||
46b6d94e PJ |
5235 | relax_domain_level= |
5236 | [KNL, SMP] Set scheduler's default relax_domain_level. | |
da82c92f | 5237 | See Documentation/admin-guide/cgroup-v1/cpusets.rst. |
46b6d94e | 5238 | |
ffd2e8df BH |
5239 | reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory |
5240 | Format: <base1>,<size1>[,<base2>,<size2>,...] | |
5241 | Reserve I/O ports or memory so the kernel won't use | |
5242 | them. If <base> is less than 0x10000, the region | |
5243 | is assumed to be I/O ports; otherwise it is memory. | |
1da177e4 | 5244 | |
cd4f0ef7 | 5245 | reservetop= [X86-32] |
461a9aff ZA |
5246 | Format: nn[KMG] |
5247 | Reserves a hole at the top of the kernel virtual | |
5248 | address space. | |
5249 | ||
7e96287d VG |
5250 | reset_devices [KNL] Force drivers to reset the underlying device |
5251 | during initialization. | |
5252 | ||
a9913044 RD |
5253 | resume= [SWSUSP] |
5254 | Specify the partition device for software suspend | |
2df83fa4 MB |
5255 | Format: |
5256 | {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>} | |
1da177e4 | 5257 | |
ecbd0da1 RW |
5258 | resume_offset= [SWSUSP] |
5259 | Specify the offset from the beginning of the partition | |
5260 | given by "resume=" at which the swap header is located, | |
5261 | in <PAGE_SIZE> units (needed only for swap files). | |
151f4e2b | 5262 | See Documentation/power/swsusp-and-swap-files.rst |
ecbd0da1 | 5263 | |
f126f733 BS |
5264 | resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to |
5265 | read the resume files | |
5266 | ||
6f8d7022 BS |
5267 | resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up. |
5268 | Useful for devices that are detected asynchronously | |
5269 | (e.g. USB and MMC devices). | |
5270 | ||
0a7b35cb MN |
5271 | retain_initrd [RAM] Keep initrd memory after extraction |
5272 | ||
7fbf47c7 AC |
5273 | retbleed= [X86] Control mitigation of RETBleed (Arbitrary |
5274 | Speculative Code Execution with Return Instructions) | |
5275 | vulnerability. | |
5276 | ||
e6cfcdda KP |
5277 | AMD-based UNRET and IBPB mitigations alone do not stop |
5278 | sibling threads from influencing the predictions of other | |
5279 | sibling threads. For that reason, STIBP is used on pro- | |
5280 | cessors that support it, and mitigate SMT on processors | |
5281 | that don't. | |
5282 | ||
e8ec1b6e KP |
5283 | off - no mitigation |
5284 | auto - automatically select a migitation | |
5285 | auto,nosmt - automatically select a mitigation, | |
5286 | disabling SMT if necessary for | |
5287 | the full mitigation (only on Zen1 | |
5288 | and older without STIBP). | |
e6cfcdda KP |
5289 | ibpb - On AMD, mitigate short speculation |
5290 | windows on basic block boundaries too. | |
5291 | Safe, highest perf impact. It also | |
5292 | enables STIBP if present. Not suitable | |
5293 | on Intel. | |
5294 | ibpb,nosmt - Like "ibpb" above but will disable SMT | |
5295 | when STIBP is not available. This is | |
5296 | the alternative for systems which do not | |
5297 | have STIBP. | |
5298 | unret - Force enable untrained return thunks, | |
5299 | only effective on AMD f15h-f17h based | |
5300 | systems. | |
5301 | unret,nosmt - Like unret, but will disable SMT when STIBP | |
5302 | is not available. This is the alternative for | |
5303 | systems which do not have STIBP. | |
7fbf47c7 AC |
5304 | |
5305 | Selecting 'auto' will choose a mitigation method at run | |
5306 | time according to the CPU. | |
5307 | ||
5308 | Not specifying this option is equivalent to retbleed=auto. | |
5309 | ||
0efbb786 AC |
5310 | rfkill.default_state= |
5311 | 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm, | |
5312 | etc. communication is blocked by default. | |
5313 | 1 Unblocked. | |
5314 | ||
5315 | rfkill.master_switch_mode= | |
5316 | 0 The "airplane mode" button does nothing. | |
5317 | 1 The "airplane mode" button toggles between everything | |
5318 | blocked and the previous configuration. | |
5319 | 2 The "airplane mode" button toggles between everything | |
5320 | blocked and everything unblocked. | |
5321 | ||
1da177e4 LT |
5322 | rhash_entries= [KNL,NET] |
5323 | Set number of hash buckets for route cache | |
5324 | ||
e16fd002 GA |
5325 | ring3mwait=disable |
5326 | [KNL] Disable ring 3 MONITOR/MWAIT feature on supported | |
5327 | CPUs. | |
5328 | ||
1da177e4 LT |
5329 | ro [KNL] Mount root device read-only on boot |
5330 | ||
d2aa1aca KC |
5331 | rodata= [KNL] |
5332 | on Mark read-only kernel memory as read-only (default). | |
5333 | off Leave read-only kernel memory writable for debugging. | |
5334 | ||
605df8af HS |
5335 | rockchip.usb_uart |
5336 | Enable the uart passthrough on the designated usb port | |
5337 | on Rockchip SoCs. When active, the signals of the | |
5338 | debug-uart get routed to the D+ and D- pins of the usb | |
5339 | port and the regular usb controller gets disabled. | |
5340 | ||
1da177e4 | 5341 | root= [KNL] Root filesystem |
f2d34fd9 | 5342 | See name_to_dev_t comment in init/do_mounts.c. |
1da177e4 LT |
5343 | |
5344 | rootdelay= [KNL] Delay (in seconds) to pause before attempting to | |
5345 | mount the root filesystem | |
5346 | ||
5347 | rootflags= [KNL] Set root filesystem mount option string | |
5348 | ||
5349 | rootfstype= [KNL] Set root filesystem type | |
5350 | ||
cc1ed754 PO |
5351 | rootwait [KNL] Wait (indefinitely) for root device to show up. |
5352 | Useful for devices that are detected asynchronously | |
5353 | (e.g. USB and MMC devices). | |
5354 | ||
5c71d618 RT |
5355 | rproc_mem=nn[KMG][@address] |
5356 | [KNL,ARM,CMA] Remoteproc physical memory block. | |
5357 | Memory area to be used by remote processor image, | |
5358 | managed by CMA. | |
5359 | ||
1da177e4 LT |
5360 | rw [KNL] Mount root device read-write on boot |
5361 | ||
5362 | S [KNL] Run init in single mode | |
5363 | ||
c60d1ae4 GS |
5364 | s390_iommu= [HW,S390] |
5365 | Set s390 IOTLB flushing mode | |
5366 | strict | |
5367 | With strict flushing every unmap operation will result in | |
5368 | an IOTLB flush. Default is lazy flushing before reuse, | |
5369 | which is faster. | |
5370 | ||
6aefbf1c NS |
5371 | s390_iommu_aperture= [KNL,S390] |
5372 | Specifies the size of the per device DMA address space | |
5373 | accessible through the DMA and IOMMU APIs as a decimal | |
5374 | factor of the size of main memory. | |
5375 | The default is 1 meaning that one can concurrently use | |
5376 | as many DMA addresses as physical memory is installed, | |
5377 | if supported by hardware, and thus map all of memory | |
5378 | once. With a value of 2 one can map all of memory twice | |
5379 | and so on. As a special case a factor of 0 imposes no | |
5380 | restrictions other than those given by hardware at the | |
5381 | cost of significant additional memory use for tables. | |
5382 | ||
1da177e4 LT |
5383 | sa1100ir [NET] |
5384 | See drivers/net/irda/sa1100_ir.c. | |
5385 | ||
9406415f | 5386 | sched_verbose [KNL] Enables verbose scheduler debug messages. |
f6630114 | 5387 | |
cb251765 MG |
5388 | schedstats= [KNL,X86] Enable or disable scheduled statistics. |
5389 | Allowed values are enable and disable. This feature | |
5390 | incurs a small amount of overhead in the scheduler | |
5391 | but is useful for debugging and performance tuning. | |
f6630114 | 5392 | |
05289b90 TG |
5393 | sched_thermal_decay_shift= |
5394 | [KNL, SMP] Set a decay shift for scheduler thermal | |
5395 | pressure signal. Thermal pressure signal follows the | |
5396 | default decay period of other scheduler pelt | |
5397 | signals(usually 32 ms but configurable). Setting | |
5398 | sched_thermal_decay_shift will left shift the decay | |
5399 | period for the thermal pressure signal by the shift | |
5400 | value. | |
5401 | i.e. with the default pelt decay period of 32 ms | |
5402 | sched_thermal_decay_shift thermal pressure decay pr | |
5403 | 1 64 ms | |
5404 | 2 128 ms | |
5405 | and so on. | |
5406 | Format: integer between 0 and 10 | |
5407 | Default is 0. | |
5408 | ||
e9d338a0 PM |
5409 | scftorture.holdoff= [KNL] |
5410 | Number of seconds to hold off before starting | |
5411 | test. Defaults to zero for module insertion and | |
5412 | to 10 seconds for built-in smp_call_function() | |
5413 | tests. | |
5414 | ||
5415 | scftorture.longwait= [KNL] | |
5416 | Request ridiculously long waits randomly selected | |
5417 | up to the chosen limit in seconds. Zero (the | |
5418 | default) disables this feature. Please note | |
5419 | that requesting even small non-zero numbers of | |
5420 | seconds can result in RCU CPU stall warnings, | |
5421 | softlockup complaints, and so on. | |
5422 | ||
5423 | scftorture.nthreads= [KNL] | |
5424 | Number of kthreads to spawn to invoke the | |
5425 | smp_call_function() family of functions. | |
5426 | The default of -1 specifies a number of kthreads | |
5427 | equal to the number of CPUs. | |
5428 | ||
5429 | scftorture.onoff_holdoff= [KNL] | |
5430 | Number seconds to wait after the start of the | |
5431 | test before initiating CPU-hotplug operations. | |
5432 | ||
5433 | scftorture.onoff_interval= [KNL] | |
5434 | Number seconds to wait between successive | |
5435 | CPU-hotplug operations. Specifying zero (which | |
5436 | is the default) disables CPU-hotplug operations. | |
5437 | ||
5438 | scftorture.shutdown_secs= [KNL] | |
5439 | The number of seconds following the start of the | |
5440 | test after which to shut down the system. The | |
5441 | default of zero avoids shutting down the system. | |
5442 | Non-zero values are useful for automated tests. | |
5443 | ||
5444 | scftorture.stat_interval= [KNL] | |
5445 | The number of seconds between outputting the | |
5446 | current test statistics to the console. A value | |
5447 | of zero disables statistics output. | |
5448 | ||
5449 | scftorture.stutter_cpus= [KNL] | |
5450 | The number of jiffies to wait between each change | |
5451 | to the set of CPUs under test. | |
5452 | ||
5453 | scftorture.use_cpus_read_lock= [KNL] | |
5454 | Use use_cpus_read_lock() instead of the default | |
5455 | preempt_disable() to disable CPU hotplug | |
5456 | while invoking one of the smp_call_function*() | |
5457 | functions. | |
5458 | ||
5459 | scftorture.verbose= [KNL] | |
5460 | Enable additional printk() statements. | |
5461 | ||
5462 | scftorture.weight_single= [KNL] | |
5463 | The probability weighting to use for the | |
5464 | smp_call_function_single() function with a zero | |
5465 | "wait" parameter. A value of -1 selects the | |
5466 | default if all other weights are -1. However, | |
5467 | if at least one weight has some other value, a | |
5468 | value of -1 will instead select a weight of zero. | |
5469 | ||
5470 | scftorture.weight_single_wait= [KNL] | |
5471 | The probability weighting to use for the | |
5472 | smp_call_function_single() function with a | |
5473 | non-zero "wait" parameter. See weight_single. | |
5474 | ||
5475 | scftorture.weight_many= [KNL] | |
5476 | The probability weighting to use for the | |
5477 | smp_call_function_many() function with a zero | |
5478 | "wait" parameter. See weight_single. | |
5479 | Note well that setting a high probability for | |
5480 | this weighting can place serious IPI load | |
5481 | on the system. | |
5482 | ||
5483 | scftorture.weight_many_wait= [KNL] | |
5484 | The probability weighting to use for the | |
5485 | smp_call_function_many() function with a | |
5486 | non-zero "wait" parameter. See weight_single | |
5487 | and weight_many. | |
5488 | ||
5489 | scftorture.weight_all= [KNL] | |
5490 | The probability weighting to use for the | |
5491 | smp_call_function_all() function with a zero | |
5492 | "wait" parameter. See weight_single and | |
5493 | weight_many. | |
5494 | ||
5495 | scftorture.weight_all_wait= [KNL] | |
5496 | The probability weighting to use for the | |
5497 | smp_call_function_all() function with a | |
5498 | non-zero "wait" parameter. See weight_single | |
5499 | and weight_many. | |
5500 | ||
5307c955 MG |
5501 | skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate |
5502 | xtime_lock contention on larger systems, and/or RCU lock | |
5503 | contention on all systems with CONFIG_MAXSMP set. | |
5504 | Format: { "0" | "1" } | |
5505 | 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1" | |
5506 | 1 -- enable. | |
5507 | Note: increases power consumption, thus should only be | |
5508 | enabled if running jitter sensitive (HPC/RT) workloads. | |
5509 | ||
89a9684e KC |
5510 | security= [SECURITY] Choose a legacy "major" security module to |
5511 | enable at boot. This has been deprecated by the | |
5512 | "lsm=" parameter. | |
0cb55ad2 RD |
5513 | |
5514 | selinux= [SELINUX] Disable or enable SELinux at boot time. | |
1da177e4 LT |
5515 | Format: { "0" | "1" } |
5516 | See security/selinux/Kconfig help text. | |
5517 | 0 -- disable. | |
5518 | 1 -- enable. | |
d41415eb | 5519 | Default value is 1. |
1da177e4 | 5520 | |
c1c124e9 JJ |
5521 | apparmor= [APPARMOR] Disable or enable AppArmor at boot time |
5522 | Format: { "0" | "1" } | |
5523 | See security/apparmor/Kconfig help text | |
5524 | 0 -- disable. | |
5525 | 1 -- enable. | |
5526 | Default value is set via kernel config option. | |
5527 | ||
cd4f0ef7 | 5528 | serialnumber [BUGS=X86-32] |
1da177e4 | 5529 | |
ba37a143 MR |
5530 | sev=option[,option...] [X86-64] See Documentation/x86/x86_64/boot-options.rst |
5531 | ||
1da177e4 LT |
5532 | shapers= [NET] |
5533 | Maximal number of shapers. | |
a9913044 | 5534 | |
1da177e4 LT |
5535 | simeth= [IA-64] |
5536 | simscsi= | |
a9913044 | 5537 | |
1da177e4 LT |
5538 | slram= [HW,MTD] |
5539 | ||
82edd9d5 RA |
5540 | slab_merge [MM] |
5541 | Enable merging of slabs with similar size when the | |
5542 | kernel is built without CONFIG_SLAB_MERGE_DEFAULT. | |
5543 | ||
423c929c JK |
5544 | slab_nomerge [MM] |
5545 | Disable merging of slabs with similar size. May be | |
5546 | necessary if there is some reason to distinguish | |
7660a6fd KC |
5547 | allocs to different slabs, especially in hardened |
5548 | environments where the risk of heap overflows and | |
5549 | layout control by attackers can usually be | |
5550 | frustrated by disabling merging. This will reduce | |
5551 | most of the exposure of a heap attack to a single | |
5552 | cache (risks via metadata attacks are mostly | |
5553 | unchanged). Debug options disable merging on their | |
5554 | own. | |
ee65728e | 5555 | For more information see Documentation/mm/slub.rst. |
423c929c | 5556 | |
3df1cccd DR |
5557 | slab_max_order= [MM, SLAB] |
5558 | Determines the maximum allowed order for slabs. | |
5559 | A high setting may cause OOMs due to memory | |
5560 | fragmentation. Defaults to 1 for systems with | |
5561 | more than 32MB of RAM, 0 otherwise. | |
5562 | ||
e17f1dfb | 5563 | slub_debug[=options[,slabs][;[options[,slabs]]...] [MM, SLUB] |
f0630fff CL |
5564 | Enabling slub_debug allows one to determine the |
5565 | culprit if slab objects become corrupted. Enabling | |
5566 | slub_debug can create guard zones around objects and | |
5567 | may poison objects when not in use. Also tracks the | |
5568 | last alloc / free. For more information see | |
ee65728e | 5569 | Documentation/mm/slub.rst. |
c1aee215 CL |
5570 | |
5571 | slub_max_order= [MM, SLUB] | |
f0630fff CL |
5572 | Determines the maximum allowed order for slabs. |
5573 | A high setting may cause OOMs due to memory | |
5574 | fragmentation. For more information see | |
ee65728e | 5575 | Documentation/mm/slub.rst. |
c1aee215 CL |
5576 | |
5577 | slub_min_objects= [MM, SLUB] | |
f0630fff CL |
5578 | The minimum number of objects per slab. SLUB will |
5579 | increase the slab order up to slub_max_order to | |
5580 | generate a sufficiently large slab able to contain | |
5581 | the number of objects indicated. The higher the number | |
5582 | of objects the smaller the overhead of tracking slabs | |
5583 | and the less frequently locks need to be acquired. | |
ee65728e | 5584 | For more information see Documentation/mm/slub.rst. |
c1aee215 CL |
5585 | |
5586 | slub_min_order= [MM, SLUB] | |
24775d65 | 5587 | Determines the minimum page order for slabs. Must be |
f0630fff | 5588 | lower than slub_max_order. |
ee65728e | 5589 | For more information see Documentation/mm/slub.rst. |
c1aee215 | 5590 | |
82edd9d5 RA |
5591 | slub_merge [MM, SLUB] |
5592 | Same with slab_merge. | |
5593 | ||
c1aee215 | 5594 | slub_nomerge [MM, SLUB] |
423c929c JK |
5595 | Same with slab_nomerge. This is supported for legacy. |
5596 | See slab_nomerge for more information. | |
c1aee215 | 5597 | |
1da177e4 LT |
5598 | smart2= [HW] |
5599 | Format: <io1>[,<io2>[,...,<io8>]] | |
5600 | ||
3791a223 PM |
5601 | smp.csd_lock_timeout= [KNL] |
5602 | Specify the period of time in milliseconds | |
5603 | that smp_call_function() and friends will wait | |
5604 | for a CPU to release the CSD lock. This is | |
5605 | useful when diagnosing bugs involving CPUs | |
5606 | disabling interrupts for extended periods | |
5607 | of time. Defaults to 5,000 milliseconds, and | |
5608 | setting a value of zero disables this feature. | |
5609 | This feature may be more efficiently disabled | |
5610 | using the csdlock_debug- kernel parameter. | |
5611 | ||
d0d4f69b BH |
5612 | smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices |
5613 | smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port | |
5614 | smsc-ircc2.ircc_sir= [HW] SIR base I/O port | |
5615 | smsc-ircc2.ircc_fir= [HW] FIR base I/O port | |
5616 | smsc-ircc2.ircc_irq= [HW] IRQ line | |
5617 | smsc-ircc2.ircc_dma= [HW] DMA channel | |
5618 | smsc-ircc2.ircc_transceiver= [HW] Transceiver type: | |
5619 | 0: Toshiba Satellite 1800 (GP data pin select) | |
5620 | 1: Fast pin select (default) | |
5621 | 2: ATC IRMode | |
5622 | ||
59bdbbd5 | 5623 | smt= [KNL,S390] Set the maximum number of threads (logical |
52c48c51 SS |
5624 | CPUs) to use per physical CPU on systems capable of |
5625 | symmetric multithreading (SMT). Will be capped to the | |
5626 | actual hardware limit. | |
5627 | Format: <integer> | |
5628 | Default: -1 (no limit) | |
5629 | ||
9c44bc03 IM |
5630 | softlockup_panic= |
5631 | [KNL] Should the soft-lockup detector generate panics. | |
f117955a | 5632 | Format: 0 | 1 |
9c44bc03 | 5633 | |
f117955a | 5634 | A value of 1 instructs the soft-lockup detector |
0a07bef6 GP |
5635 | to panic the machine when a soft-lockup occurs. It is |
5636 | also controlled by the kernel.softlockup_panic sysctl | |
5637 | and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the | |
5638 | respective build-time switch to that functionality. | |
3ce62385 | 5639 | |
ed235875 AT |
5640 | softlockup_all_cpu_backtrace= |
5641 | [KNL] Should the soft-lockup detector generate | |
5642 | backtraces on all cpus. | |
f117955a | 5643 | Format: 0 | 1 |
ed235875 | 5644 | |
1da177e4 | 5645 | sonypi.*= [HW] Sony Programmable I/O Control Device driver |
9e1cbede | 5646 | See Documentation/admin-guide/laptops/sonypi.rst |
1da177e4 | 5647 | |
da285121 DW |
5648 | spectre_v2= [X86] Control mitigation of Spectre variant 2 |
5649 | (indirect branch speculation) vulnerability. | |
fa1202ef TG |
5650 | The default operation protects the kernel from |
5651 | user space attacks. | |
da285121 | 5652 | |
fa1202ef TG |
5653 | on - unconditionally enable, implies |
5654 | spectre_v2_user=on | |
5655 | off - unconditionally disable, implies | |
5656 | spectre_v2_user=off | |
da285121 DW |
5657 | auto - kernel detects whether your CPU model is |
5658 | vulnerable | |
5659 | ||
5660 | Selecting 'on' will, and 'auto' may, choose a | |
5661 | mitigation method at run time according to the | |
5662 | CPU, the available microcode, the setting of the | |
5663 | CONFIG_RETPOLINE configuration option, and the | |
5664 | compiler with which the kernel was built. | |
5665 | ||
fa1202ef TG |
5666 | Selecting 'on' will also enable the mitigation |
5667 | against user space to user space task attacks. | |
5668 | ||
5669 | Selecting 'off' will disable both the kernel and | |
5670 | the user space protections. | |
5671 | ||
da285121 DW |
5672 | Specific mitigations can also be selected manually: |
5673 | ||
5674 | retpoline - replace indirect branches | |
5ad3eb11 PZ |
5675 | retpoline,generic - Retpolines |
5676 | retpoline,lfence - LFENCE; indirect branch | |
5677 | retpoline,amd - alias for retpoline,lfence | |
5678 | eibrs - enhanced IBRS | |
5679 | eibrs,retpoline - enhanced IBRS + Retpolines | |
5680 | eibrs,lfence - enhanced IBRS + LFENCE | |
7c693f54 | 5681 | ibrs - use IBRS to protect kernel |
da285121 DW |
5682 | |
5683 | Not specifying this option is equivalent to | |
5684 | spectre_v2=auto. | |
5685 | ||
fa1202ef TG |
5686 | spectre_v2_user= |
5687 | [X86] Control mitigation of Spectre variant 2 | |
5688 | (indirect branch speculation) vulnerability between | |
5689 | user space tasks | |
5690 | ||
5691 | on - Unconditionally enable mitigations. Is | |
5692 | enforced by spectre_v2=on | |
5693 | ||
5694 | off - Unconditionally disable mitigations. Is | |
5695 | enforced by spectre_v2=off | |
5696 | ||
7cc765a6 TG |
5697 | prctl - Indirect branch speculation is enabled, |
5698 | but mitigation can be enabled via prctl | |
5699 | per thread. The mitigation control state | |
5700 | is inherited on fork. | |
5701 | ||
55a97402 TG |
5702 | prctl,ibpb |
5703 | - Like "prctl" above, but only STIBP is | |
5704 | controlled per thread. IBPB is issued | |
5705 | always when switching between different user | |
5706 | space processes. | |
5707 | ||
6b3e64c2 TG |
5708 | seccomp |
5709 | - Same as "prctl" above, but all seccomp | |
5710 | threads will enable the mitigation unless | |
5711 | they explicitly opt out. | |
5712 | ||
55a97402 TG |
5713 | seccomp,ibpb |
5714 | - Like "seccomp" above, but only STIBP is | |
5715 | controlled per thread. IBPB is issued | |
5716 | always when switching between different | |
5717 | user space processes. | |
5718 | ||
fa1202ef TG |
5719 | auto - Kernel selects the mitigation depending on |
5720 | the available CPU features and vulnerability. | |
6b3e64c2 | 5721 | |
2f46993d | 5722 | Default mitigation: "prctl" |
fa1202ef TG |
5723 | |
5724 | Not specifying this option is equivalent to | |
5725 | spectre_v2_user=auto. | |
5726 | ||
24f7fc83 KRW |
5727 | spec_store_bypass_disable= |
5728 | [HW] Control Speculative Store Bypass (SSB) Disable mitigation | |
5729 | (Speculative Store Bypass vulnerability) | |
5730 | ||
5731 | Certain CPUs are vulnerable to an exploit against a | |
5732 | a common industry wide performance optimization known | |
5733 | as "Speculative Store Bypass" in which recent stores | |
5734 | to the same memory location may not be observed by | |
5735 | later loads during speculative execution. The idea | |
5736 | is that such stores are unlikely and that they can | |
5737 | be detected prior to instruction retirement at the | |
5738 | end of a particular speculation execution window. | |
5739 | ||
5740 | In vulnerable processors, the speculatively forwarded | |
5741 | store can be used in a cache side channel attack, for | |
5742 | example to read memory to which the attacker does not | |
5743 | directly have access (e.g. inside sandboxed code). | |
5744 | ||
5745 | This parameter controls whether the Speculative Store | |
5746 | Bypass optimization is used. | |
5747 | ||
6b4c1360 ME |
5748 | On x86 the options are: |
5749 | ||
f21b53b2 KC |
5750 | on - Unconditionally disable Speculative Store Bypass |
5751 | off - Unconditionally enable Speculative Store Bypass | |
5752 | auto - Kernel detects whether the CPU model contains an | |
5753 | implementation of Speculative Store Bypass and | |
5754 | picks the most appropriate mitigation. If the | |
5755 | CPU is not vulnerable, "off" is selected. If the | |
5756 | CPU is vulnerable the default mitigation is | |
5757 | architecture and Kconfig dependent. See below. | |
5758 | prctl - Control Speculative Store Bypass per thread | |
5759 | via prctl. Speculative Store Bypass is enabled | |
5760 | for a process by default. The state of the control | |
5761 | is inherited on fork. | |
5762 | seccomp - Same as "prctl" above, but all seccomp threads | |
5763 | will disable SSB unless they explicitly opt out. | |
24f7fc83 | 5764 | |
f21b53b2 | 5765 | Default mitigations: |
2f46993d | 5766 | X86: "prctl" |
f21b53b2 | 5767 | |
6b4c1360 ME |
5768 | On powerpc the options are: |
5769 | ||
5770 | on,auto - On Power8 and Power9 insert a store-forwarding | |
5771 | barrier on kernel entry and exit. On Power7 | |
5772 | perform a software flush on kernel entry and | |
5773 | exit. | |
5774 | off - No action. | |
5775 | ||
5776 | Not specifying this option is equivalent to | |
5777 | spec_store_bypass_disable=auto. | |
5778 | ||
1da177e4 LT |
5779 | spia_io_base= [HW,MTD] |
5780 | spia_fio_base= | |
5781 | spia_pedr= | |
5782 | spia_peddr= | |
5783 | ||
6650cdd9 | 5784 | split_lock_detect= |
ebca1770 | 5785 | [X86] Enable split lock detection or bus lock detection |
6650cdd9 PZI |
5786 | |
5787 | When enabled (and if hardware support is present), atomic | |
5788 | instructions that access data across cache line | |
ebca1770 FY |
5789 | boundaries will result in an alignment check exception |
5790 | for split lock detection or a debug exception for | |
5791 | bus lock detection. | |
6650cdd9 PZI |
5792 | |
5793 | off - not enabled | |
5794 | ||
ebca1770 | 5795 | warn - the kernel will emit rate-limited warnings |
6650cdd9 | 5796 | about applications triggering the #AC |
ebca1770 FY |
5797 | exception or the #DB exception. This mode is |
5798 | the default on CPUs that support split lock | |
5799 | detection or bus lock detection. Default | |
5800 | behavior is by #AC if both features are | |
5801 | enabled in hardware. | |
6650cdd9 PZI |
5802 | |
5803 | fatal - the kernel will send SIGBUS to applications | |
ebca1770 FY |
5804 | that trigger the #AC exception or the #DB |
5805 | exception. Default behavior is by #AC if | |
5806 | both features are enabled in hardware. | |
6650cdd9 | 5807 | |
9d839c28 FY |
5808 | ratelimit:N - |
5809 | Set system wide rate limit to N bus locks | |
5810 | per second for bus lock detection. | |
5811 | 0 < N <= 1000. | |
5812 | ||
5813 | N/A for split lock detection. | |
5814 | ||
5815 | ||
6650cdd9 PZI |
5816 | If an #AC exception is hit in the kernel or in |
5817 | firmware (i.e. not while executing in user mode) | |
5818 | the kernel will oops in either "warn" or "fatal" | |
5819 | mode. | |
5820 | ||
ebca1770 FY |
5821 | #DB exception for bus lock is triggered only when |
5822 | CPL > 0. | |
5823 | ||
7e5b3c26 MG |
5824 | srbds= [X86,INTEL] |
5825 | Control the Special Register Buffer Data Sampling | |
5826 | (SRBDS) mitigation. | |
5827 | ||
5828 | Certain CPUs are vulnerable to an MDS-like | |
5829 | exploit which can leak bits from the random | |
5830 | number generator. | |
5831 | ||
5832 | By default, this issue is mitigated by | |
5833 | microcode. However, the microcode fix can cause | |
5834 | the RDRAND and RDSEED instructions to become | |
5835 | much slower. Among other effects, this will | |
5836 | result in reduced throughput from /dev/urandom. | |
5837 | ||
5838 | The microcode mitigation can be disabled with | |
5839 | the following option: | |
5840 | ||
5841 | off: Disable mitigation and remove | |
5842 | performance impact to RDRAND and RDSEED | |
5843 | ||
a57ffb3c PM |
5844 | srcutree.big_cpu_lim [KNL] |
5845 | Specifies the number of CPUs constituting a | |
5846 | large system, such that srcu_struct structures | |
5847 | should immediately allocate an srcu_node array. | |
5848 | This kernel-boot parameter defaults to 128, | |
5849 | but takes effect only when the low-order four | |
5850 | bits of srcutree.convert_to_big is equal to 3 | |
5851 | (decide at boot). | |
5852 | ||
c69a00a1 PM |
5853 | srcutree.convert_to_big [KNL] |
5854 | Specifies under what conditions an SRCU tree | |
5855 | srcu_struct structure will be converted to big | |
5856 | form, that is, with an rcu_node tree: | |
5857 | ||
5858 | 0: Never. | |
5859 | 1: At init_srcu_struct() time. | |
5860 | 2: When rcutorture decides to. | |
a57ffb3c | 5861 | 3: Decide at boot time (default). |
9f2e91d9 | 5862 | 0x1X: Above plus if high contention. |
c69a00a1 PM |
5863 | |
5864 | Either way, the srcu_node tree will be sized based | |
5865 | on the actual runtime number of CPUs (nr_cpu_ids) | |
5866 | instead of the compile-time CONFIG_NR_CPUS. | |
5867 | ||
c350c008 PM |
5868 | srcutree.counter_wrap_check [KNL] |
5869 | Specifies how frequently to check for | |
5870 | grace-period sequence counter wrap for the | |
5871 | srcu_data structure's ->srcu_gp_seq_needed field. | |
5872 | The greater the number of bits set in this kernel | |
5873 | parameter, the less frequently counter wrap will | |
5874 | be checked for. Note that the bottom two bits | |
5875 | are ignored. | |
5876 | ||
22607d66 PM |
5877 | srcutree.exp_holdoff [KNL] |
5878 | Specifies how many nanoseconds must elapse | |
5879 | since the end of the last SRCU grace period for | |
5880 | a given srcu_struct until the next normal SRCU | |
5881 | grace period will be considered for automatic | |
5882 | expediting. Set to zero to disable automatic | |
5883 | expediting. | |
5884 | ||
4f2bfd94 NU |
5885 | srcutree.srcu_max_nodelay [KNL] |
5886 | Specifies the number of no-delay instances | |
5887 | per jiffy for which the SRCU grace period | |
5888 | worker thread will be rescheduled with zero | |
5889 | delay. Beyond this limit, worker thread will | |
5890 | be rescheduled with a sleep delay of one jiffy. | |
5891 | ||
5892 | srcutree.srcu_max_nodelay_phase [KNL] | |
5893 | Specifies the per-grace-period phase, number of | |
5894 | non-sleeping polls of readers. Beyond this limit, | |
5895 | grace period worker thread will be rescheduled | |
5896 | with a sleep delay of one jiffy, between each | |
5897 | rescan of the readers, for a grace period phase. | |
5898 | ||
5899 | srcutree.srcu_retry_check_delay [KNL] | |
5900 | Specifies number of microseconds of non-sleeping | |
5901 | delay between each non-sleeping poll of readers. | |
5902 | ||
9f2e91d9 PM |
5903 | srcutree.small_contention_lim [KNL] |
5904 | Specifies the number of update-side contention | |
5905 | events per jiffy will be tolerated before | |
5906 | initiating a conversion of an srcu_struct | |
5907 | structure to big form. Note that the value of | |
5908 | srcutree.convert_to_big must have the 0x10 bit | |
5909 | set for contention-based conversions to occur. | |
5910 | ||
a43ae4df MZ |
5911 | ssbd= [ARM64,HW] |
5912 | Speculative Store Bypass Disable control | |
5913 | ||
5914 | On CPUs that are vulnerable to the Speculative | |
5915 | Store Bypass vulnerability and offer a | |
5916 | firmware based mitigation, this parameter | |
5917 | indicates how the mitigation should be used: | |
5918 | ||
5919 | force-on: Unconditionally enable mitigation for | |
5920 | for both kernel and userspace | |
5921 | force-off: Unconditionally disable mitigation for | |
5922 | for both kernel and userspace | |
5923 | kernel: Always enable mitigation in the | |
5924 | kernel, and offer a prctl interface | |
5925 | to allow userspace to register its | |
5926 | interest in being mitigated too. | |
5927 | ||
1be7107f HD |
5928 | stack_guard_gap= [MM] |
5929 | override the default stack gap protection. The value | |
5930 | is in page units and it defines how many pages prior | |
5931 | to (for stacks growing down) resp. after (for stacks | |
5932 | growing up) the main stack are reserved for no other | |
5933 | mapping. Default value is 256 pages. | |
5934 | ||
e1fdc403 VJ |
5935 | stack_depot_disable= [KNL] |
5936 | Setting this to true through kernel command line will | |
5937 | disable the stack depot thereby saving the static memory | |
5938 | consumed by the stack hash table. By default this is set | |
5939 | to false. | |
5940 | ||
f38f1d2a SR |
5941 | stacktrace [FTRACE] |
5942 | Enabled the stack tracer on boot up. | |
5943 | ||
762e1207 SR |
5944 | stacktrace_filter=[function-list] |
5945 | [FTRACE] Limit the functions that the stack tracer | |
25942e5e | 5946 | will trace at boot up. function-list is a comma-separated |
762e1207 SR |
5947 | list of functions. This list can be changed at run |
5948 | time by the stack_trace_filter file in the debugfs | |
5949 | tracing directory. Note, this enables stack tracing | |
5950 | and the stacktrace above is not needed. | |
5951 | ||
1da177e4 LT |
5952 | sti= [PARISC,HW] |
5953 | Format: <num> | |
5954 | Set the STI (builtin display/keyboard on the HP-PARISC | |
5955 | machines) console (graphic card) which should be used | |
5956 | as the initial boot-console. | |
5957 | See also comment in drivers/video/console/sticore.c. | |
5958 | ||
5959 | sti_font= [HW] | |
5960 | See comment in drivers/video/console/sticore.c. | |
5961 | ||
5962 | stifb= [HW] | |
5963 | Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]] | |
5964 | ||
3aac3ebe TG |
5965 | strict_sas_size= |
5966 | [X86] | |
5967 | Format: <bool> | |
5968 | Enable or disable strict sigaltstack size checks | |
5969 | against the required signal frame size which | |
5970 | depends on the supported FPU features. This can | |
5971 | be used to filter out binaries which have | |
5972 | not yet been made aware of AT_MINSIGSTKSZ. | |
5973 | ||
cbf11071 TM |
5974 | sunrpc.min_resvport= |
5975 | sunrpc.max_resvport= | |
5976 | [NFS,SUNRPC] | |
5977 | SunRPC servers often require that client requests | |
5978 | originate from a privileged port (i.e. a port in the | |
5979 | range 0 < portnr < 1024). | |
5980 | An administrator who wishes to reserve some of these | |
5981 | ports for other uses may adjust the range that the | |
5982 | kernel's sunrpc client considers to be privileged | |
5983 | using these two parameters to set the minimum and | |
5984 | maximum port values. | |
5985 | ||
ff3ac5c3 TM |
5986 | sunrpc.svc_rpc_per_connection_limit= |
5987 | [NFS,SUNRPC] | |
5988 | Limit the number of requests that the server will | |
5989 | process in parallel from a single connection. | |
5990 | The default value is 0 (no limit). | |
5991 | ||
42a7fc4a GB |
5992 | sunrpc.pool_mode= |
5993 | [NFS] | |
5994 | Control how the NFS server code allocates CPUs to | |
5995 | service thread pools. Depending on how many NICs | |
5996 | you have and where their interrupts are bound, this | |
5997 | option will affect which CPUs will do NFS serving. | |
5998 | Note: this parameter cannot be changed while the | |
5999 | NFS server is running. | |
6000 | ||
6001 | auto the server chooses an appropriate mode | |
6002 | automatically using heuristics | |
6003 | global a single global pool contains all CPUs | |
6004 | percpu one pool for each CPU | |
6005 | pernode one pool for each NUMA node (equivalent | |
6006 | to global on non-NUMA machines) | |
6007 | ||
cbf11071 TM |
6008 | sunrpc.tcp_slot_table_entries= |
6009 | sunrpc.udp_slot_table_entries= | |
6010 | [NFS,SUNRPC] | |
6011 | Sets the upper limit on the number of simultaneous | |
6012 | RPC calls that can be sent from the client to a | |
6013 | server. Increasing these values may allow you to | |
6014 | improve throughput, but will also increase the | |
6015 | amount of memory reserved for use by the client. | |
6016 | ||
1d4a9c17 BN |
6017 | suspend.pm_test_delay= |
6018 | [SUSPEND] | |
6019 | Sets the number of seconds to remain in a suspend test | |
6020 | mode before resuming the system (see | |
6021 | /sys/power/pm_test). Only available when CONFIG_PM_DEBUG | |
6022 | is set. Default value is 5. | |
6023 | ||
6a9c930b RP |
6024 | svm= [PPC] |
6025 | Format: { on | off | y | n | 1 | 0 } | |
6026 | This parameter controls use of the Protected | |
6027 | Execution Facility on pSeries. | |
6028 | ||
59bdbbd5 RD |
6029 | swapaccount= [KNL] |
6030 | Format: [0|1] | |
6031 | Enable accounting of swap in memory resource | |
a42c390c | 6032 | controller if no parameter or 1 is given or disable |
da82c92f | 6033 | it if 0 is given (See Documentation/admin-guide/cgroup-v1/memory.rst) |
a42c390c | 6034 | |
91fec0f5 | 6035 | swiotlb= [ARM,IA-64,PPC,MIPS,X86] |
20347fca | 6036 | Format: { <int> [,<int>] | force | noforce } |
91fec0f5 | 6037 | <int> -- Number of I/O TLB slabs |
20347fca | 6038 | <int> -- Second integer after comma. Number of swiotlb |
72311809 TL |
6039 | areas with their own lock. Will be rounded up |
6040 | to a power of 2. | |
91fec0f5 JK |
6041 | force -- force using of bounce buffers even if they |
6042 | wouldn't be automatically used by the kernel | |
fff5d992 | 6043 | noforce -- Never use bounce buffers (for debugging) |
a9913044 | 6044 | |
1da177e4 LT |
6045 | switches= [HW,M68k] |
6046 | ||
3db978d4 VB |
6047 | sysctl.*= [KNL] |
6048 | Set a sysctl parameter, right before loading the init | |
6049 | process, as if the value was written to the respective | |
6050 | /proc/sys/... file. Both '.' and '/' are recognized as | |
6051 | separators. Unrecognized parameters and invalid values | |
6052 | are reported in the kernel log. Sysctls registered | |
6053 | later by a loaded module cannot be set this way. | |
6054 | Example: sysctl.vm.swappiness=40 | |
6055 | ||
e52eec13 AK |
6056 | sysfs.deprecated=0|1 [KNL] |
6057 | Enable/disable old style sysfs layout for old udev | |
6058 | on older distributions. When this option is enabled | |
6059 | very new udev will not work anymore. When this option | |
6060 | is disabled (or CONFIG_SYSFS_DEPRECATED not compiled) | |
6061 | in older udev will not work anymore. | |
6062 | Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in | |
6063 | the kernel configuration. | |
6064 | ||
5d6f647f IM |
6065 | sysrq_always_enabled |
6066 | [KNL] | |
6067 | Ignore sysrq setting - this boot parameter will | |
6068 | neutralize any effect of /proc/sys/kernel/sysrq. | |
6069 | Useful for debugging. | |
6070 | ||
747029a5 FF |
6071 | tcpmhash_entries= [KNL,NET] |
6072 | Set the number of tcp_metrics_hash slots. | |
6073 | Default value is 8192 or 16384 depending on total | |
6074 | ram pages. This is used to specify the TCP metrics | |
1cec2cac | 6075 | cache size. See Documentation/networking/ip-sysctl.rst |
747029a5 FF |
6076 | "tcp_no_metrics_save" section for more details. |
6077 | ||
1da177e4 LT |
6078 | tdfx= [HW,DRM] |
6079 | ||
59bdbbd5 RD |
6080 | test_suspend= [SUSPEND] |
6081 | Format: { "mem" | "standby" | "freeze" }[,N] | |
77437fd4 | 6082 | Specify "mem" (for Suspend-to-RAM) or "standby" (for |
acc82342 SP |
6083 | standby suspend) or "freeze" (for suspend type freeze) |
6084 | as the system sleep state during system startup with | |
6085 | the optional capability to repeat N number of times. | |
6086 | The system is woken from this state using a | |
6087 | wakeup-capable RTC alarm. | |
77437fd4 | 6088 | |
1da177e4 LT |
6089 | thash_entries= [KNL,NET] |
6090 | Set number of hash buckets for TCP connection | |
6091 | ||
f8707ec9 LB |
6092 | thermal.act= [HW,ACPI] |
6093 | -1: disable all active trip points in all thermal zones | |
6094 | <degrees C>: override all lowest active trip points | |
6095 | ||
c52a7419 LB |
6096 | thermal.crt= [HW,ACPI] |
6097 | -1: disable all critical trip points in all thermal zones | |
22a94d79 | 6098 | <degrees C>: override all critical trip points |
c52a7419 | 6099 | |
f5487145 LB |
6100 | thermal.nocrt= [HW,ACPI] |
6101 | Set to disable actions on ACPI thermal zone | |
6102 | critical and hot trip points. | |
6103 | ||
72b33ef8 LB |
6104 | thermal.off= [HW,ACPI] |
6105 | 1: disable ACPI thermal control | |
6106 | ||
a70cdc52 LB |
6107 | thermal.psv= [HW,ACPI] |
6108 | -1: disable all passive trip points | |
ada9cfdd RD |
6109 | <degrees C>: override all passive trip points to this |
6110 | value | |
a70cdc52 | 6111 | |
730ff34d LB |
6112 | thermal.tzp= [HW,ACPI] |
6113 | Specify global default ACPI thermal zone polling rate | |
6114 | <deci-seconds>: poll all this frequency | |
6115 | 0: no polling (default) | |
6116 | ||
8d32a307 TG |
6117 | threadirqs [KNL] |
6118 | Force threading of all interrupt handlers except those | |
24775d65 | 6119 | marked explicitly IRQF_NO_THREAD. |
8d32a307 | 6120 | |
2b1a61f0 HC |
6121 | topology= [S390] |
6122 | Format: {off | on} | |
6123 | Specify if the kernel should make use of the cpu | |
f65e51d7 SL |
6124 | topology information if the hardware supports this. |
6125 | The scheduler will make use of this information and | |
2b1a61f0 | 6126 | e.g. base its process migration decisions on it. |
c9af3fa9 | 6127 | Default is on. |
2b1a61f0 | 6128 | |
2d73bae1 NA |
6129 | topology_updates= [KNL, PPC, NUMA] |
6130 | Format: {off} | |
6131 | Specify if the kernel should ignore (off) | |
6132 | topology updates sent by the hypervisor to this | |
6133 | LPAR. | |
6134 | ||
8171d3e0 PM |
6135 | torture.disable_onoff_at_boot= [KNL] |
6136 | Prevent the CPU-hotplug component of torturing | |
6137 | until after init has spawned. | |
6138 | ||
2102ad29 PM |
6139 | torture.ftrace_dump_at_shutdown= [KNL] |
6140 | Dump the ftrace buffer at torture-test shutdown, | |
6141 | even if there were no errors. This can be a | |
6142 | very costly operation when many torture tests | |
6143 | are running concurrently, especially on systems | |
6144 | with rotating-rust storage. | |
6145 | ||
8a67a20b PM |
6146 | torture.verbose_sleep_frequency= [KNL] |
6147 | Specifies how many verbose printk()s should be | |
6148 | emitted between each sleep. The default of zero | |
6149 | disables verbose-printk() sleeping. | |
6150 | ||
6151 | torture.verbose_sleep_duration= [KNL] | |
6152 | Duration of each verbose-printk() sleep in jiffies. | |
6153 | ||
1da177e4 LT |
6154 | tp720= [HW,PS2] |
6155 | ||
225a9be2 RA |
6156 | tpm_suspend_pcr=[HW,TPM] |
6157 | Format: integer pcr id | |
6158 | Specify that at suspend time, the tpm driver | |
6159 | should extend the specified pcr with zeros, | |
6160 | as a workaround for some chips which fail to | |
6161 | flush the last written pcr on TPM_SaveState. | |
6162 | This will guarantee that all the other pcrs | |
6163 | are saved. | |
6164 | ||
389cfd96 | 6165 | tp_printk [FTRACE] |
0daa2302 SRRH |
6166 | Have the tracepoints sent to printk as well as the |
6167 | tracing ring buffer. This is useful for early boot up | |
6168 | where the system hangs or reboots and does not give the | |
6169 | option for reading the tracing buffer or performing a | |
6170 | ftrace_dump_on_oops. | |
6171 | ||
6172 | To turn off having tracepoints sent to printk, | |
6173 | echo 0 > /proc/sys/kernel/tracepoint_printk | |
6174 | Note, echoing 1 into this file without the | |
6175 | tracepoint_printk kernel cmdline option has no effect. | |
6176 | ||
f3860136 SRV |
6177 | The tp_printk_stop_on_boot (see below) can also be used |
6178 | to stop the printing of events to console at | |
6179 | late_initcall_sync. | |
6180 | ||
0daa2302 SRRH |
6181 | ** CAUTION ** |
6182 | ||
6183 | Having tracepoints sent to printk() and activating high | |
6184 | frequency tracepoints such as irq or sched, can cause | |
6185 | the system to live lock. | |
6186 | ||
389cfd96 | 6187 | tp_printk_stop_on_boot [FTRACE] |
f3860136 SRV |
6188 | When tp_printk (above) is set, it can cause a lot of noise |
6189 | on the console. It may be useful to only include the | |
6190 | printing of events during boot up, as user space may | |
6191 | make the system inoperable. | |
6192 | ||
6193 | This command line option will stop the printing of events | |
6194 | to console at the late_initcall_sync() time frame. | |
6195 | ||
9d612bef | 6196 | trace_buf_size=nn[KMG] |
3e6fb8e9 | 6197 | [FTRACE] will set tracing buffer size on each cpu. |
631595fb | 6198 | |
59bdbbd5 RD |
6199 | trace_clock= [FTRACE] Set the clock used for tracing events |
6200 | at boot up. | |
6201 | local - Use the per CPU time stamp counter | |
6202 | (converted into nanoseconds). Fast, but | |
6203 | depending on the architecture, may not be | |
6204 | in sync between CPUs. | |
6205 | global - Event time stamps are synchronize across | |
6206 | CPUs. May be slower than the local clock, | |
6207 | but better for some race conditions. | |
6208 | counter - Simple counting of events (1, 2, ..) | |
6209 | note, some counts may be skipped due to the | |
6210 | infrastructure grabbing the clock more than | |
6211 | once per event. | |
6212 | uptime - Use jiffies as the time stamp. | |
6213 | perf - Use the same clock that perf uses. | |
6214 | mono - Use ktime_get_mono_fast_ns() for time stamps. | |
6215 | mono_raw - Use ktime_get_raw_fast_ns() for time | |
6216 | stamps. | |
6217 | boot - Use ktime_get_boot_fast_ns() for time stamps. | |
6218 | Architectures may add more clocks. See | |
6219 | Documentation/trace/ftrace.rst for more details. | |
6220 | ||
020e5f85 LZ |
6221 | trace_event=[event-list] |
6222 | [FTRACE] Set and start specified trace events in order | |
d81749ea | 6223 | to facilitate early boot debugging. The event-list is a |
25942e5e | 6224 | comma-separated list of trace events to enable. See |
5fb94e9c | 6225 | also Documentation/trace/events.rst |
020e5f85 | 6226 | |
7bcfaf54 SR |
6227 | trace_options=[option-list] |
6228 | [FTRACE] Enable or disable tracer options at boot. | |
6229 | The option-list is a comma delimited list of options | |
6230 | that can be enabled or disabled just as if you were | |
6231 | to echo the option name into | |
6232 | ||
6233 | /sys/kernel/debug/tracing/trace_options | |
6234 | ||
6235 | For example, to enable stacktrace option (to dump the | |
6236 | stack trace of each event), add to the command line: | |
6237 | ||
6238 | trace_options=stacktrace | |
6239 | ||
5fb94e9c | 6240 | See also Documentation/trace/ftrace.rst "trace options" |
7bcfaf54 SR |
6241 | section. |
6242 | ||
de7edd31 SRRH |
6243 | traceoff_on_warning |
6244 | [FTRACE] enable this option to disable tracing when a | |
6245 | warning is hit. This turns off "tracing_on". Tracing can | |
6246 | be enabled again by echoing '1' into the "tracing_on" | |
6247 | file located in /sys/kernel/debug/tracing/ | |
6248 | ||
6249 | This option is useful, as it disables the trace before | |
6250 | the WARNING dump is called, which prevents the trace to | |
6251 | be filled with content caused by the warning output. | |
6252 | ||
6253 | This option can also be set at run time via the sysctl | |
6254 | option: kernel/traceoff_on_warning | |
6255 | ||
fcf4d821 JK |
6256 | transparent_hugepage= |
6257 | [KNL] | |
6258 | Format: [always|madvise|never] | |
6259 | Can be used to control the default behavior of the system | |
6260 | with respect to transparent hugepages. | |
45c9a74f MR |
6261 | See Documentation/admin-guide/mm/transhuge.rst |
6262 | for more details. | |
fcf4d821 | 6263 | |
5d0682be SG |
6264 | trusted.source= [KEYS] |
6265 | Format: <string> | |
6266 | This parameter identifies the trust source as a backend | |
6267 | for trusted keys implementation. Supported trust | |
6268 | sources: | |
6269 | - "tpm" | |
6270 | - "tee" | |
e9c5048c | 6271 | - "caam" |
5d0682be SG |
6272 | If not specified then it defaults to iterating through |
6273 | the trust source list starting with TPM and assigns the | |
6274 | first trust source as a backend which is initialized | |
6275 | successfully during iteration. | |
6276 | ||
fcd7c269 AF |
6277 | trusted.rng= [KEYS] |
6278 | Format: <string> | |
6279 | The RNG used to generate key material for trusted keys. | |
6280 | Can be one of: | |
6281 | - "kernel" | |
6282 | - the same value as trusted.source: "tpm" or "tee" | |
6283 | - "default" | |
6284 | If not specified, "default" is used. In this case, | |
6285 | the RNG's choice is left to each individual trust source. | |
6286 | ||
d3b8f889 | 6287 | tsc= Disable clocksource stability checks for TSC. |
395628ef AK |
6288 | Format: <string> |
6289 | [x86] reliable: mark tsc clocksource as reliable, this | |
d3b8f889 | 6290 | disables clocksource verification at runtime, as well |
6291 | as the stability checks done at bootup. Used to enable | |
6292 | high-resolution timer mode on older hardware, and in | |
6293 | virtualized environment. | |
e82b8e4e VP |
6294 | [x86] noirqtime: Do not use TSC to do irq accounting. |
6295 | Used to run time disable IRQ_TIME_ACCOUNTING on any | |
6296 | platforms where RDTSC is slow and this accounting | |
6297 | can add overhead. | |
6be53520 DL |
6298 | [x86] unstable: mark the TSC clocksource as unstable, this |
6299 | marks the TSC unconditionally unstable at bootup and | |
6300 | avoids any further wobbles once the TSC watchdog notices. | |
0f0b7e1c JL |
6301 | [x86] nowatchdog: disable clocksource watchdog. Used |
6302 | in situations with strict latency requirements (where | |
6303 | interruptions from clocksource watchdog are not | |
6304 | acceptable). | |
395628ef | 6305 | |
bd35c77e KP |
6306 | tsc_early_khz= [X86] Skip early TSC calibration and use the given |
6307 | value instead. Useful when the early TSC frequency discovery | |
6308 | procedure is not reliable, such as on overclocked systems | |
6309 | with CPUID.16h support and partial CPUID.15h support. | |
6310 | Format: <unsigned int> | |
6311 | ||
95c5824f PG |
6312 | tsx= [X86] Control Transactional Synchronization |
6313 | Extensions (TSX) feature in Intel processors that | |
6314 | support TSX control. | |
6315 | ||
6316 | This parameter controls the TSX feature. The options are: | |
6317 | ||
6318 | on - Enable TSX on the system. Although there are | |
6319 | mitigations for all known security vulnerabilities, | |
6320 | TSX has been known to be an accelerator for | |
6321 | several previous speculation-related CVEs, and | |
6322 | so there may be unknown security risks associated | |
6323 | with leaving it enabled. | |
6324 | ||
6325 | off - Disable TSX on the system. (Note that this | |
6326 | option takes effect only on newer CPUs which are | |
6327 | not vulnerable to MDS, i.e., have | |
6328 | MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get | |
6329 | the new IA32_TSX_CTRL MSR through a microcode | |
6330 | update. This new MSR allows for the reliable | |
6331 | deactivation of the TSX functionality.) | |
6332 | ||
7531a359 PG |
6333 | auto - Disable TSX if X86_BUG_TAA is present, |
6334 | otherwise enable TSX on the system. | |
6335 | ||
95c5824f PG |
6336 | Not specifying this option is equivalent to tsx=off. |
6337 | ||
6338 | See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst | |
6339 | for more details. | |
6340 | ||
a7a248c5 PG |
6341 | tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async |
6342 | Abort (TAA) vulnerability. | |
6343 | ||
6344 | Similar to Micro-architectural Data Sampling (MDS) | |
6345 | certain CPUs that support Transactional | |
6346 | Synchronization Extensions (TSX) are vulnerable to an | |
6347 | exploit against CPU internal buffers which can forward | |
6348 | information to a disclosure gadget under certain | |
6349 | conditions. | |
6350 | ||
6351 | In vulnerable processors, the speculatively forwarded | |
6352 | data can be used in a cache side channel attack, to | |
6353 | access data to which the attacker does not have direct | |
6354 | access. | |
6355 | ||
6356 | This parameter controls the TAA mitigation. The | |
6357 | options are: | |
6358 | ||
6359 | full - Enable TAA mitigation on vulnerable CPUs | |
6360 | if TSX is enabled. | |
6361 | ||
6362 | full,nosmt - Enable TAA mitigation and disable SMT on | |
6363 | vulnerable CPUs. If TSX is disabled, SMT | |
6364 | is not disabled because CPU is not | |
6365 | vulnerable to cross-thread TAA attacks. | |
6366 | off - Unconditionally disable TAA mitigation | |
6367 | ||
64870ed1 WL |
6368 | On MDS-affected machines, tsx_async_abort=off can be |
6369 | prevented by an active MDS mitigation as both vulnerabilities | |
6370 | are mitigated with the same mechanism so in order to disable | |
6371 | this mitigation, you need to specify mds=off too. | |
6372 | ||
a7a248c5 PG |
6373 | Not specifying this option is equivalent to |
6374 | tsx_async_abort=full. On CPUs which are MDS affected | |
6375 | and deploy MDS mitigation, TAA mitigation is not | |
6376 | required and doesn't provide any additional | |
6377 | mitigation. | |
6378 | ||
6379 | For details see: | |
6380 | Documentation/admin-guide/hw-vuln/tsx_async_abort.rst | |
6381 | ||
a9913044 RD |
6382 | turbografx.map[2|3]= [HW,JOY] |
6383 | TurboGraFX parallel port interface | |
6384 | Format: | |
6385 | <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7> | |
1752118d | 6386 | See also Documentation/input/devices/joystick-parport.rst |
1da177e4 | 6387 | |
b6935f8c | 6388 | udbg-immortal [PPC] When debugging early kernel crashes that |
e52347bd | 6389 | happen after console_init() and before a proper |
b6935f8c CK |
6390 | console driver takes over, this boot options might |
6391 | help "seeing" what's going on. | |
6392 | ||
f86dcc5a ED |
6393 | uhash_entries= [KNL,NET] |
6394 | Set number of hash buckets for UDP/UDP-Lite connections | |
6395 | ||
5f8364b7 AS |
6396 | uhci-hcd.ignore_oc= |
6397 | [USB] Ignore overcurrent events (default N). | |
6398 | Some badly-designed motherboards generate lots of | |
6399 | bogus events, for ports that aren't wired to | |
6400 | anything. Set this parameter to avoid log spamming. | |
6401 | Note that genuine overcurrent events won't be | |
6402 | reported either. | |
6403 | ||
e3a61b0a | 6404 | unknown_nmi_panic |
44a4dcf7 | 6405 | [X86] Cause panic on unknown NMI. |
e3a61b0a | 6406 | |
c4fc2342 CDH |
6407 | usbcore.authorized_default= |
6408 | [USB] Default USB device authorization: | |
6409 | (default -1 = authorized except for wireless USB, | |
7bae0432 DT |
6410 | 0 = not authorized, 1 = authorized, 2 = authorized |
6411 | if device connected to internal port) | |
c4fc2342 | 6412 | |
b5e795f8 AS |
6413 | usbcore.autosuspend= |
6414 | [USB] The autosuspend time delay (in seconds) used | |
6415 | for newly-detected USB devices (default 2). This | |
6416 | is the time required before an idle device will be | |
6417 | autosuspended. Devices for which the delay is set | |
eaafbc3a | 6418 | to a negative value won't be autosuspended at all. |
b5e795f8 | 6419 | |
fd7c519d JK |
6420 | usbcore.usbfs_snoop= |
6421 | [USB] Set to log all usbfs traffic (default 0 = off). | |
6422 | ||
0290cc9f AS |
6423 | usbcore.usbfs_snoop_max= |
6424 | [USB] Maximum number of bytes to snoop in each URB | |
6425 | (default = 65536). | |
6426 | ||
fd7c519d JK |
6427 | usbcore.blinkenlights= |
6428 | [USB] Set to cycle leds on hubs (default 0 = off). | |
6429 | ||
6430 | usbcore.old_scheme_first= | |
6431 | [USB] Start with the old device initialization | |
3155f4f4 | 6432 | scheme (default 0 = off). |
fd7c519d | 6433 | |
3f5eb8d5 AS |
6434 | usbcore.usbfs_memory_mb= |
6435 | [USB] Memory limit (in MB) for buffers allocated by | |
6436 | usbfs (default = 16, 0 = max = 2047). | |
6437 | ||
fd7c519d JK |
6438 | usbcore.use_both_schemes= |
6439 | [USB] Try the other device initialization scheme | |
6440 | if the first one fails (default 1 = enabled). | |
6441 | ||
6442 | usbcore.initial_descriptor_timeout= | |
6443 | [USB] Specifies timeout for the initial 64-byte | |
6dddd7a7 | 6444 | USB_REQ_GET_DESCRIPTOR request in milliseconds |
fd7c519d JK |
6445 | (default 5000 = 5.0 seconds). |
6446 | ||
40d58148 ON |
6447 | usbcore.nousb [USB] Disable the USB subsystem |
6448 | ||
027bd6ca KHF |
6449 | usbcore.quirks= |
6450 | [USB] A list of quirk entries to augment the built-in | |
6451 | usb core quirk list. List entries are separated by | |
6452 | commas. Each entry has the form | |
6453 | VendorID:ProductID:Flags. The IDs are 4-digit hex | |
6454 | numbers and Flags is a set of letters. Each letter | |
6455 | will change the built-in quirk; setting it if it is | |
6456 | clear and clearing it if it is set. The letters have | |
6457 | the following meanings: | |
6458 | a = USB_QUIRK_STRING_FETCH_255 (string | |
6459 | descriptors must not be fetched using | |
6460 | a 255-byte read); | |
6461 | b = USB_QUIRK_RESET_RESUME (device can't resume | |
6462 | correctly so reset it instead); | |
6463 | c = USB_QUIRK_NO_SET_INTF (device can't handle | |
6464 | Set-Interface requests); | |
6465 | d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't | |
6466 | handle its Configuration or Interface | |
6467 | strings); | |
6468 | e = USB_QUIRK_RESET (device can't be reset | |
6469 | (e.g morph devices), don't use reset); | |
6470 | f = USB_QUIRK_HONOR_BNUMINTERFACES (device has | |
6471 | more interface descriptions than the | |
6472 | bNumInterfaces count, and can't handle | |
6473 | talking to these interfaces); | |
6474 | g = USB_QUIRK_DELAY_INIT (device needs a pause | |
6475 | during initialization, after we read | |
6476 | the device descriptor); | |
6477 | h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For | |
6478 | high speed and super speed interrupt | |
6479 | endpoints, the USB 2.0 and USB 3.0 spec | |
6480 | require the interval in microframes (1 | |
6481 | microframe = 125 microseconds) to be | |
6482 | calculated as interval = 2 ^ | |
6483 | (bInterval-1). | |
6484 | Devices with this quirk report their | |
6485 | bInterval as the result of this | |
6486 | calculation instead of the exponent | |
6487 | variable used in the calculation); | |
6488 | i = USB_QUIRK_DEVICE_QUALIFIER (device can't | |
6489 | handle device_qualifier descriptor | |
6490 | requests); | |
6491 | j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device | |
6492 | generates spurious wakeup, ignore | |
6493 | remote wakeup capability); | |
6494 | k = USB_QUIRK_NO_LPM (device can't handle Link | |
6495 | Power Management); | |
6496 | l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL | |
6497 | (Device reports its bInterval as linear | |
6498 | frames instead of the USB 2.0 | |
6499 | calculation); | |
6500 | m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs | |
6501 | to be disconnected before suspend to | |
4d8d5a39 KHF |
6502 | prevent spurious wakeup); |
6503 | n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a | |
6504 | pause after every control message); | |
781f0766 KHF |
6505 | o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra |
6506 | delay after resetting its port); | |
027bd6ca KHF |
6507 | Example: quirks=0781:5580:bk,0a5c:5834:gij |
6508 | ||
1da177e4 LT |
6509 | usbhid.mousepoll= |
6510 | [USBHID] The interval which mice are to be polled at. | |
a9913044 | 6511 | |
933bfe4d TJ |
6512 | usbhid.jspoll= |
6513 | [USBHID] The interval which joysticks are to be polled at. | |
6514 | ||
2ddc8e2d FA |
6515 | usbhid.kbpoll= |
6516 | [USBHID] The interval which keyboards are to be polled at. | |
6517 | ||
d4f373e5 AS |
6518 | usb-storage.delay_use= |
6519 | [UMS] The delay in seconds before a new device is | |
19101954 | 6520 | scanned for Logical Units (default 1). |
d4f373e5 AS |
6521 | |
6522 | usb-storage.quirks= | |
6523 | [UMS] A list of quirks entries to supplement or | |
6524 | override the built-in unusual_devs list. List | |
6525 | entries are separated by commas. Each entry has | |
6526 | the form VID:PID:Flags where VID and PID are Vendor | |
6527 | and Product ID values (4-digit hex numbers) and | |
6528 | Flags is a set of characters, each corresponding | |
6529 | to a common usb-storage quirk flag as follows: | |
c838ea46 | 6530 | a = SANE_SENSE (collect more than 18 bytes |
65cc8bf9 | 6531 | of sense data, not on uas); |
a0bb1081 | 6532 | b = BAD_SENSE (don't collect more than 18 |
65cc8bf9 | 6533 | bytes of sense data, not on uas); |
d4f373e5 AS |
6534 | c = FIX_CAPACITY (decrease the reported |
6535 | device capacity by one sector); | |
5116901d | 6536 | d = NO_READ_DISC_INFO (don't use |
65cc8bf9 | 6537 | READ_DISC_INFO command, not on uas); |
5116901d KR |
6538 | e = NO_READ_CAPACITY_16 (don't use |
6539 | READ_CAPACITY_16 command); | |
734016b0 HG |
6540 | f = NO_REPORT_OPCODES (don't use report opcodes |
6541 | command, uas only); | |
ee136af4 HG |
6542 | g = MAX_SECTORS_240 (don't transfer more than |
6543 | 240 sectors at a time, uas only); | |
c838ea46 AS |
6544 | h = CAPACITY_HEURISTICS (decrease the |
6545 | reported device capacity by one | |
6546 | sector if the number is odd); | |
d4f373e5 AS |
6547 | i = IGNORE_DEVICE (don't bind to this |
6548 | device); | |
13630746 HG |
6549 | j = NO_REPORT_LUNS (don't use report luns |
6550 | command, uas only); | |
8010622c | 6551 | k = NO_SAME (do not use WRITE_SAME, uas only) |
d4f373e5 | 6552 | l = NOT_LOCKABLE (don't try to lock and |
65cc8bf9 | 6553 | unlock ejectable media, not on uas); |
d4f373e5 | 6554 | m = MAX_SECTORS_64 (don't transfer more |
65cc8bf9 ON |
6555 | than 64 sectors = 32 KB at a time, |
6556 | not on uas); | |
21c13a4f | 6557 | n = INITIAL_READ10 (force a retry of the |
65cc8bf9 | 6558 | initial READ(10) command, not on uas); |
c838ea46 | 6559 | o = CAPACITY_OK (accept the capacity |
65cc8bf9 | 6560 | reported by the device, not on uas); |
eaa05dfc | 6561 | p = WRITE_CACHE (the device cache is ON |
65cc8bf9 | 6562 | by default, not on uas); |
d4f373e5 | 6563 | r = IGNORE_RESIDUE (the device reports |
65cc8bf9 | 6564 | bogus residue values, not on uas); |
d4f373e5 AS |
6565 | s = SINGLE_LUN (the device has only one |
6566 | Logical Unit); | |
59307852 HG |
6567 | t = NO_ATA_1X (don't allow ATA(12) and ATA(16) |
6568 | commands, uas only); | |
b6089f19 | 6569 | u = IGNORE_UAS (don't bind to the uas driver); |
d4f373e5 AS |
6570 | w = NO_WP_DETECT (don't test whether the |
6571 | medium is write-protected). | |
050bc4e8 | 6572 | y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE |
65cc8bf9 ON |
6573 | even if the device claims no cache, |
6574 | not on uas) | |
d4f373e5 AS |
6575 | Example: quirks=0419:aaf5:rl,0421:0433:rc |
6576 | ||
ac1667db SB |
6577 | user_debug= [KNL,ARM] |
6578 | Format: <int> | |
6579 | See arch/arm/Kconfig.debug help text. | |
6580 | 1 - undefined instruction events | |
6581 | 2 - system calls | |
6582 | 4 - invalid data aborts | |
6583 | 8 - SIGSEGV faults | |
6584 | 16 - SIGBUS faults | |
6585 | Example: user_debug=31 | |
6586 | ||
14315592 IC |
6587 | userpte= |
6588 | [X86] Flags controlling user PTE allocations. | |
6589 | ||
6590 | nohigh = do not allocate PTE pages in | |
6591 | HIGHMEM regardless of setting | |
6592 | of CONFIG_HIGHPTE. | |
6593 | ||
59bdbbd5 | 6594 | vdso= [X86,SH,SPARC] |
b0b49f26 AL |
6595 | On X86_32, this is an alias for vdso32=. Otherwise: |
6596 | ||
6597 | vdso=1: enable VDSO (the default) | |
e6e5494c IM |
6598 | vdso=0: disable VDSO mapping |
6599 | ||
b0b49f26 AL |
6600 | vdso32= [X86] Control the 32-bit vDSO |
6601 | vdso32=1: enable 32-bit VDSO | |
6602 | vdso32=0 or vdso32=2: disable 32-bit VDSO | |
6603 | ||
6604 | See the help text for CONFIG_COMPAT_VDSO for more | |
6605 | details. If CONFIG_COMPAT_VDSO is set, the default is | |
6606 | vdso32=0; otherwise, the default is vdso32=1. | |
6607 | ||
6608 | For compatibility with older kernels, vdso32=2 is an | |
6609 | alias for vdso32=0. | |
6610 | ||
6611 | Try vdso32=0 if you encounter an error that says: | |
6612 | dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed! | |
af65d648 | 6613 | |
d080d397 YI |
6614 | vector= [IA-64,SMP] |
6615 | vector=percpu: enable percpu vector domain | |
6616 | ||
1da177e4 | 6617 | video= [FB] Frame buffer configuration |
ab42b818 | 6618 | See Documentation/fb/modedb.rst. |
1da177e4 | 6619 | |
59bdbbd5 RD |
6620 | video.brightness_switch_enabled= [ACPI] |
6621 | Format: [0|1] | |
3afe6dab AL |
6622 | If set to 1, on receiving an ACPI notify event |
6623 | generated by hotkey, video driver will adjust brightness | |
6624 | level and then send out the event to user space through | |
59bdbbd5 | 6625 | the allocated input device. If set to 0, video driver |
3afe6dab AL |
6626 | will only send out the event without touching backlight |
6627 | brightness level. | |
2843768b | 6628 | default: 1 |
3afe6dab | 6629 | |
81a054ce PM |
6630 | virtio_mmio.device= |
6631 | [VMMIO] Memory mapped virtio (platform) device. | |
6632 | ||
6633 | <size>@<baseaddr>:<irq>[:<id>] | |
6634 | where: | |
6635 | <size> := size (can use standard suffixes | |
6636 | like K, M and G) | |
6637 | <baseaddr> := physical base address | |
6638 | <irq> := interrupt number (as passed to | |
6639 | request_irq()) | |
6640 | <id> := (optional) platform device id | |
6641 | example: | |
6642 | virtio_mmio.device=1K@0x100b0000:48:7 | |
6643 | ||
6644 | Can be used multiple times for multiple devices. | |
6645 | ||
cd4f0ef7 | 6646 | vga= [BOOT,X86-32] Select a particular video mode |
cb1aaebe | 6647 | See Documentation/x86/boot.rst and |
4f4cfa6c | 6648 | Documentation/admin-guide/svga.rst. |
1da177e4 LT |
6649 | Use vga=ask for menu. |
6650 | This is actually a boot loader parameter; the value is | |
6651 | passed to the kernel using a special protocol. | |
6652 | ||
f682a97a AD |
6653 | vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y. |
6654 | May slow down system boot speed, especially when | |
6655 | enabled on systems with a large amount of memory. | |
6656 | All options are enabled by default, and this | |
6657 | interface is meant to allow for selectively | |
6658 | enabling or disabling specific virtual memory | |
6659 | debugging features. | |
6660 | ||
6661 | Available options are: | |
6662 | P Enable page structure init time poisoning | |
6663 | - Disable all of the above options | |
6664 | ||
a9913044 | 6665 | vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact |
1da177e4 LT |
6666 | size of <nn>. This can be used to increase the |
6667 | minimum size (128MB on x86). It can also be used to | |
6668 | decrease the size and leave more room for directly | |
6669 | mapped kernel RAM. | |
6670 | ||
3f429842 HC |
6671 | vmcp_cma=nn[MG] [KNL,S390] |
6672 | Sets the memory size reserved for contiguous memory | |
6673 | allocations for the vmcp device driver. | |
6674 | ||
585c3047 PO |
6675 | vmhalt= [KNL,S390] Perform z/VM CP command after system halt. |
6676 | Format: <command> | |
1da177e4 | 6677 | |
585c3047 PO |
6678 | vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic. |
6679 | Format: <command> | |
6680 | ||
6681 | vmpoff= [KNL,S390] Perform z/VM CP command after power off. | |
6682 | Format: <command> | |
a9913044 | 6683 | |
3ae36655 AL |
6684 | vsyscall= [X86-64] |
6685 | Controls the behavior of vsyscalls (i.e. calls to | |
6686 | fixed addresses of 0xffffffffff600x00 from legacy | |
6687 | code). Most statically-linked binaries and older | |
6688 | versions of glibc use these calls. Because these | |
6689 | functions are at fixed addresses, they make nice | |
6690 | targets for exploits that can control RIP. | |
6691 | ||
2e57ae05 | 6692 | emulate [default] Vsyscalls turn into traps and are |
bd49e16e AL |
6693 | emulated reasonably safely. The vsyscall |
6694 | page is readable. | |
3ae36655 | 6695 | |
bd49e16e AL |
6696 | xonly Vsyscalls turn into traps and are |
6697 | emulated reasonably safely. The vsyscall | |
6698 | page is not readable. | |
3ae36655 AL |
6699 | |
6700 | none Vsyscalls don't work at all. This makes | |
6701 | them quite hard to use for exploits but | |
6702 | might break your system. | |
6703 | ||
3855ae1c CL |
6704 | vt.color= [VT] Default text color. |
6705 | Format: 0xYX, X = foreground, Y = background. | |
6706 | Default: 0x07 = light gray on black. | |
6707 | ||
9ea9a886 CL |
6708 | vt.cur_default= [VT] Default cursor shape. |
6709 | Format: 0xCCBBAA, where AA, BB, and CC are the same as | |
6710 | the parameters of the <Esc>[?A;B;Cc escape sequence; | |
6711 | see VGA-softcursor.txt. Default: 2 = underline. | |
6712 | ||
0cb55ad2 RD |
6713 | vt.default_blu= [VT] |
6714 | Format: <blue0>,<blue1>,<blue2>,...,<blue15> | |
6715 | Change the default blue palette of the console. | |
6716 | This is a 16-member array composed of values | |
6717 | ranging from 0-255. | |
6718 | ||
6719 | vt.default_grn= [VT] | |
6720 | Format: <green0>,<green1>,<green2>,...,<green15> | |
6721 | Change the default green palette of the console. | |
6722 | This is a 16-member array composed of values | |
6723 | ranging from 0-255. | |
6724 | ||
6725 | vt.default_red= [VT] | |
6726 | Format: <red0>,<red1>,<red2>,...,<red15> | |
6727 | Change the default red palette of the console. | |
6728 | This is a 16-member array composed of values | |
6729 | ranging from 0-255. | |
6730 | ||
6731 | vt.default_utf8= | |
6732 | [VT] | |
6733 | Format=<0|1> | |
6734 | Set system-wide default UTF-8 mode for all tty's. | |
6735 | Default is 1, i.e. UTF-8 mode is enabled for all | |
6736 | newly opened terminals. | |
6737 | ||
f6c06b68 MG |
6738 | vt.global_cursor_default= |
6739 | [VT] | |
6740 | Format=<-1|0|1> | |
6741 | Set system-wide default for whether a cursor | |
6742 | is shown on new VTs. Default is -1, | |
6743 | i.e. cursors will be created by default unless | |
6744 | overridden by individual drivers. 0 will hide | |
6745 | cursors, 1 will display them. | |
6746 | ||
3855ae1c CL |
6747 | vt.italic= [VT] Default color for italic text; 0-15. |
6748 | Default: 2 = green. | |
6749 | ||
6750 | vt.underline= [VT] Default color for underlined text; 0-15. | |
6751 | Default: 3 = cyan. | |
6752 | ||
4724ba57 | 6753 | watchdog timers [HW,WDT] For information on watchdog timers, |
cc2a2d19 | 6754 | see Documentation/watchdog/watchdog-parameters.rst |
4724ba57 RD |
6755 | or other driver-specific files in the |
6756 | Documentation/watchdog/ directory. | |
1da177e4 | 6757 | |
11295055 LO |
6758 | watchdog_thresh= |
6759 | [KNL] | |
6760 | Set the hard lockup detector stall duration | |
6761 | threshold in seconds. The soft lockup detector | |
6762 | threshold is set to twice the value. A value of 0 | |
6763 | disables both lockup detectors. Default is 10 | |
6764 | seconds. | |
6765 | ||
82607adc TH |
6766 | workqueue.watchdog_thresh= |
6767 | If CONFIG_WQ_WATCHDOG is configured, workqueue can | |
6768 | warn stall conditions and dump internal state to | |
6769 | help debugging. 0 disables workqueue stall | |
6770 | detection; otherwise, it's the stall threshold | |
6771 | duration in seconds. The default value is 30 and | |
6772 | it can be updated at runtime by writing to the | |
6773 | corresponding sysfs file. | |
6774 | ||
d55262c4 TH |
6775 | workqueue.disable_numa |
6776 | By default, all work items queued to unbound | |
6777 | workqueues are affine to the NUMA nodes they're | |
6778 | issued on, which results in better behavior in | |
6779 | general. If NUMA affinity needs to be disabled for | |
6780 | whatever reason, this option can be used. Note | |
6781 | that this also can be controlled per-workqueue for | |
6782 | workqueues visible under /sys/bus/workqueue/. | |
6783 | ||
cee22a15 VK |
6784 | workqueue.power_efficient |
6785 | Per-cpu workqueues are generally preferred because | |
6786 | they show better performance thanks to cache | |
6787 | locality; unfortunately, per-cpu workqueues tend to | |
6788 | be more power hungry than unbound workqueues. | |
6789 | ||
6790 | Enabling this makes the per-cpu workqueues which | |
6791 | were observed to contribute significantly to power | |
6792 | consumption unbound, leading to measurably lower | |
6793 | power usage at the cost of small performance | |
6794 | overhead. | |
6795 | ||
6796 | The default value of this parameter is determined by | |
6797 | the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT. | |
6798 | ||
f303fccb TH |
6799 | workqueue.debug_force_rr_cpu |
6800 | Workqueue used to implicitly guarantee that work | |
6801 | items queued without explicit CPU specified are put | |
6802 | on the local CPU. This guarantee is no longer true | |
6803 | and while local CPU is still preferred work items | |
6804 | may be put on foreign CPUs. This debug option | |
6805 | forces round-robin CPU selection to flush out | |
6806 | usages which depend on the now broken guarantee. | |
6807 | When enabled, memory and cache locality will be | |
6808 | impacted. | |
6809 | ||
0cb55ad2 RD |
6810 | x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of |
6811 | default x2apic cluster mode on platforms | |
6812 | supporting x2apic. | |
6813 | ||
c70727a5 JG |
6814 | xen_512gb_limit [KNL,X86-64,XEN] |
6815 | Restricts the kernel running paravirtualized under Xen | |
6816 | to use only up to 512 GB of RAM. The reason to do so is | |
6817 | crash analysis tools and Xen tools for doing domain | |
6818 | save/restore/migration must be enabled to handle larger | |
6819 | domains. | |
6820 | ||
c1c5413a SS |
6821 | xen_emul_unplug= [HW,X86,XEN] |
6822 | Unplug Xen emulated devices | |
6823 | Format: [unplug0,][unplug1] | |
6824 | ide-disks -- unplug primary master IDE devices | |
6825 | aux-ide-disks -- unplug non-primary-master IDE devices | |
6826 | nics -- unplug network devices | |
6827 | all -- unplug all emulated devices (NICs and IDE disks) | |
1dc7ce99 IC |
6828 | unnecessary -- unplugging emulated devices is |
6829 | unnecessary even if the host did not respond to | |
6830 | the unplug protocol | |
c93a4dfb | 6831 | never -- do not unplug even if version check succeeds |
c1c5413a | 6832 | |
c6875f3a BO |
6833 | xen_legacy_crash [X86,XEN] |
6834 | Crash from Xen panic notifier, without executing late | |
6835 | panic() code such as dumping handler. | |
6836 | ||
15a3eac0 | 6837 | xen_nopvspin [X86,XEN] |
9a3c05e6 ZD |
6838 | Disables the qspinlock slowpath using Xen PV optimizations. |
6839 | This parameter is obsoleted by "nopvspin" parameter, which | |
6840 | has equivalent effect for XEN platform. | |
15a3eac0 | 6841 | |
8d693b91 KRW |
6842 | xen_nopv [X86] |
6843 | Disables the PV optimizations forcing the HVM guest to | |
6844 | run as generic HVM guest with no PV drivers. | |
b39b0497 ZD |
6845 | This option is obsoleted by the "nopv" option, which |
6846 | has equivalent effect for XEN platform. | |
8d693b91 | 6847 | |
b36b0fe9 DW |
6848 | xen_no_vector_callback |
6849 | [KNL,X86,XEN] Disable the vector callback for Xen | |
6850 | event channel interrupts. | |
6851 | ||
197ecb38 MMG |
6852 | xen_scrub_pages= [XEN] |
6853 | Boolean option to control scrubbing pages before giving them back | |
6854 | to Xen, for use by other domains. Can be also changed at runtime | |
6855 | with /sys/devices/system/xen_memory/xen_memory0/scrub_pages. | |
6856 | Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT. | |
6857 | ||
2ec16bc0 RT |
6858 | xen_timer_slop= [X86-64,XEN] |
6859 | Set the timer slop (in nanoseconds) for the virtual Xen | |
6860 | timers (default is 100000). This adjusts the minimum | |
6861 | delta of virtualized Xen timers, where lower values | |
6862 | improve timer resolution at the expense of processing | |
6863 | more timer interrupts. | |
6864 | ||
40fdea02 JG |
6865 | xen.balloon_boot_timeout= [XEN] |
6866 | The time (in seconds) to wait before giving up to boot | |
6867 | in case initial ballooning fails to free enough memory. | |
6868 | Applies only when running as HVM or PVH guest and | |
6869 | started with less memory configured than allowed at | |
6870 | max. Default is 180. | |
6871 | ||
e99502f7 JG |
6872 | xen.event_eoi_delay= [XEN] |
6873 | How long to delay EOI handling in case of event | |
6874 | storms (jiffies). Default is 10. | |
6875 | ||
6876 | xen.event_loop_timeout= [XEN] | |
6877 | After which time (jiffies) the event handling loop | |
6878 | should start to delay EOI handling. Default is 2. | |
6879 | ||
1a89c1dc JG |
6880 | xen.fifo_events= [XEN] |
6881 | Boolean parameter to disable using fifo event handling | |
6882 | even if available. Normally fifo event handling is | |
6883 | preferred over the 2-level event handling, as it is | |
6884 | fairer and the number of possible event channels is | |
6885 | much higher. Default is on (use fifo events). | |
6886 | ||
30978346 ZD |
6887 | nopv= [X86,XEN,KVM,HYPER_V,VMWARE] |
6888 | Disables the PV optimizations forcing the guest to run | |
6889 | as generic guest with no PV drivers. Currently support | |
6890 | XEN HVM, KVM, HYPER_V and VMWARE guest. | |
6891 | ||
9a3c05e6 | 6892 | nopvspin [X86,XEN,KVM] |
05eee619 ZD |
6893 | Disables the qspinlock slow path using PV optimizations |
6894 | which allow the hypervisor to 'idle' the guest on lock | |
6895 | contention. | |
6896 | ||
1da177e4 | 6897 | xirc2ps_cs= [NET,PCMCIA] |
a9913044 RD |
6898 | Format: |
6899 | <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]] | |
c0addc9a | 6900 | |
ba45cff6 MN |
6901 | xive= [PPC] |
6902 | By default on POWER9 and above, the kernel will | |
6903 | natively use the XIVE interrupt controller. This option | |
6904 | allows the fallback firmware mode to be used: | |
6905 | ||
6906 | off Fallback to firmware control of XIVE interrupt | |
6907 | controller on both pseries and powernv | |
6908 | platforms. Only useful on POWER9 and above. | |
6909 | ||
c21ee04f CLG |
6910 | xive.store-eoi=off [PPC] |
6911 | By default on POWER10 and above, the kernel will use | |
6912 | stores for EOI handling when the XIVE interrupt mode | |
6913 | is active. This option allows the XIVE driver to use | |
6914 | loads instead, as on POWER9. | |
6915 | ||
c0addc9a LT |
6916 | xhci-hcd.quirks [USB,KNL] |
6917 | A hex value specifying bitmask with supplemental xhci | |
6918 | host controller quirks. Meaning of each bit can be | |
6919 | consulted in header drivers/usb/host/xhci.h. | |
6278f55b GR |
6920 | |
6921 | xmon [PPC] | |
6922 | Format: { early | on | rw | ro | off } | |
6923 | Controls if xmon debugger is enabled. Default is off. | |
6924 | Passing only "xmon" is equivalent to "xmon=early". | |
6925 | early Call xmon as early as possible on boot; xmon | |
6926 | debugger is called from setup_arch(). | |
6927 | on xmon debugger hooks will be installed so xmon | |
6928 | is only called on a kernel crash. Default mode, | |
6929 | i.e. either "ro" or "rw" mode, is controlled | |
6930 | with CONFIG_XMON_DEFAULT_RO_MODE. | |
6931 | rw xmon debugger hooks will be installed so xmon | |
6932 | is called only on a kernel crash, mode is write, | |
6933 | meaning SPR registers, memory and, other data | |
6934 | can be written using xmon commands. | |
6935 | ro same as "rw" option above but SPR registers, | |
6936 | memory, and other data can't be written using | |
6937 | xmon commands. | |
6938 | off xmon is disabled. |