efi: Add "efi_fake_mem" boot option
[linux-2.6-block.git] / Documentation / kernel-parameters.txt
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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
1da177e4 3
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4The following is a consolidated list of the kernel parameters as
5implemented by the __setup(), core_param() and module_param() macros
6and sorted into English Dictionary order (defined as ignoring all
7punctuation and sorting digits before letters in a case insensitive
8manner), and with descriptions where known.
9
10The kernel parses parameters from the kernel command line up to "--";
11if it doesn't recognize a parameter and it doesn't contain a '.', the
12parameter gets passed to init: parameters with '=' go into init's
13environment, others are passed as command line arguments to init.
14Everything after "--" is passed as an argument to init.
15
16Module parameters can be specified in two ways: via the kernel command
17line with a module name prefix, or via modprobe, e.g.:
18
19 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
21
22Parameters for modules which are built into the kernel need to be
23specified on the kernel command line. modprobe looks through the
24kernel command line (/proc/cmdline) and collects module parameters
25when it loads a module, so the kernel command line can be used for
26loadable modules too.
1da177e4 27
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28Hyphens (dashes) and underscores are equivalent in parameter names, so
29 log_buf_len=1M print-fatal-signals=1
30can also be entered as
31 log-buf-len=1M print_fatal_signals=1
32
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33Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
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36This document may not be entirely up to date and comprehensive. The command
37"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38module. Loadable modules, after being loaded into the running kernel, also
39reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40parameters may be changed at runtime by the command
41"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
42
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43The parameters listed below are only valid if certain kernel build options were
44enabled and if respective hardware is present. The text in square brackets at
45the beginning of each description states the restrictions within which a
46parameter is applicable:
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47
48 ACPI ACPI support is enabled.
c99c108a 49 AGP AGP (Accelerated Graphics Port) is enabled.
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50 ALSA ALSA sound support is enabled.
51 APIC APIC support is enabled.
52 APM Advanced Power Management support is enabled.
16290246 53 ARM ARM architecture is enabled.
e7ba176b 54 AVR32 AVR32 architecture is enabled.
1da177e4 55 AX25 Appropriate AX.25 support is enabled.
0ae53640 56 BLACKFIN Blackfin architecture is enabled.
1e435256 57 CLK Common clock infrastructure is enabled.
5c71d618 58 CMA Contiguous Memory Area support is enabled.
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59 DRM Direct Rendering Management support is enabled.
60 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
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61 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
62 EFI EFI Partitioning (GPT) is enabled
63 EIDE EIDE/ATAPI support is enabled.
7102ebcd 64 EVM Extended Verification Module
1da177e4 65 FB The frame buffer device is enabled.
16290246 66 FTRACE Function tracing enabled.
2521f2c2 67 GCOV GCOV profiling is enabled.
1da177e4 68 HW Appropriate hardware is enabled.
1da177e4 69 IA-64 IA-64 architecture is enabled.
6146f0d5 70 IMA Integrity measurement architecture is enabled.
1da177e4 71 IOSCHED More than one I/O scheduler is enabled.
41e2e8be 72 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
b0f83b28 73 IPV6 IPv6 support is enabled.
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74 ISAPNP ISA PnP code is enabled.
75 ISDN Appropriate ISDN support is enabled.
76 JOY Appropriate joystick support is enabled.
84c08fd6 77 KGDB Kernel debugger support is enabled.
fef07aae 78 KVM Kernel Virtual Machine support is enabled.
11ef697b 79 LIBATA Libata driver is enabled
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80 LP Printer support is enabled.
81 LOOP Loopback device support is enabled.
82 M68k M68k architecture is enabled.
83 These options have more detailed description inside of
84 Documentation/m68k/kernel-options.txt.
1da177e4 85 MDA MDA console support is enabled.
16290246 86 MIPS MIPS architecture is enabled.
1da177e4 87 MOUSE Appropriate mouse support is enabled.
309e57df 88 MSI Message Signaled Interrupts (PCI).
c8facbb6 89 MTD MTD (Memory Technology Device) support is enabled.
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90 NET Appropriate network support is enabled.
91 NUMA NUMA support is enabled.
92 NFS Appropriate NFS support is enabled.
93 OSS OSS sound support is enabled.
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94 PV_OPS A paravirtualized kernel is enabled.
95 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
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96 PARISC The PA-RISC architecture is enabled.
97 PCI PCI bus support is enabled.
7f785763 98 PCIE PCI Express support is enabled.
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99 PCMCIA The PCMCIA subsystem is enabled.
100 PNP Plug & Play support is enabled.
101 PPC PowerPC architecture is enabled.
102 PPT Parallel port support is enabled.
103 PS2 Appropriate PS/2 support is enabled.
104 RAM RAM disk support is enabled.
105 S390 S390 architecture is enabled.
106 SCSI Appropriate SCSI support is enabled.
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107 A lot of drivers have their options described inside
108 the Documentation/scsi/ sub-directory.
20510f2f 109 SECURITY Different security models are enabled.
1da177e4 110 SELINUX SELinux support is enabled.
c1c124e9 111 APPARMOR AppArmor support is enabled.
1da177e4 112 SERIAL Serial support is enabled.
e523d93c 113 SH SuperH architecture is enabled.
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114 SMP The kernel is an SMP kernel.
115 SPARC Sparc architecture is enabled.
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116 SWSUSP Software suspend (hibernation) is enabled.
117 SUSPEND System suspend states are enabled.
225a9be2 118 TPM TPM drivers are enabled.
1da177e4 119 TS Appropriate touchscreen support is enabled.
d4f373e5 120 UMS USB Mass Storage support is enabled.
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121 USB USB support is enabled.
122 USBHID USB Human Interface Device support is enabled.
123 V4L Video For Linux support is enabled.
81a054ce 124 VMMIO Driver for memory mapped virtio devices is enabled.
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125 VGA The VGA console has been enabled.
126 VT Virtual terminal support is enabled.
127 WDT Watchdog support is enabled.
128 XT IBM PC/XT MFM hard disk support is enabled.
cd4f0ef7 129 X86-32 X86-32, aka i386 architecture is enabled.
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130 X86-64 X86-64 architecture is enabled.
131 More X86-64 boot options can be found in
71cced6e 132 Documentation/x86/x86_64/boot-options.txt .
16290246 133 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
c1c5413a 134 XEN Xen support is enabled
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135
136In addition, the following text indicates that the option:
137
138 BUGS= Relates to possible processor bugs on the said processor.
139 KNL Is a kernel start-up parameter.
140 BOOT Is a boot loader parameter.
141
142Parameters denoted with BOOT are actually interpreted by the boot
143loader, and have no meaning to the kernel directly.
144Do not modify the syntax of boot loader parameters without extreme
954a8b81 145need or coordination with <Documentation/x86/boot.txt>.
1da177e4 146
5558870b 147There are also arch-specific kernel-parameters not documented here.
71cced6e 148See for example <Documentation/x86/x86_64/boot-options.txt>.
5558870b 149
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150Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151a trailing = on the name of any parameter states that that parameter will
152be entered as an environment variable, whereas its absence indicates that
153it will appear as a kernel argument readable via /proc/cmdline by programs
154running once the system is up.
155
9c4751fd 156The number of kernel parameters is not limited, but the length of the
157complete command line (parameters including spaces etc.) is limited to
158a fixed number of characters. This limit depends on the architecture
159and is between 256 and 4096 characters. It is defined in the file
160./include/asm/setup.h as COMMAND_LINE_SIZE.
161
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162Finally, the [KMG] suffix is commonly described after a number of kernel
163parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165bytes respectively. Such letter suffixes can also be entirely omitted.
166
9c4751fd 167
b10d79f7 168 acpi= [HW,ACPI,X86,ARM64]
03d926f8 169 Advanced Configuration and Power Interface
68ca4069 170 Format: { force | off | strict | noirq | rsdt }
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171 force -- enable ACPI if default was off
172 off -- disable ACPI if default was on
173 noirq -- do not use ACPI for IRQ routing
a9913044 174 strict -- Be less tolerant of platforms that are not
1da177e4 175 strictly ACPI specification compliant.
237889bf 176 rsdt -- prefer RSDT over (default) XSDT
aa2110cb 177 copy_dsdt -- copy DSDT to memory
b10d79f7 178 For ARM64, ONLY "acpi=off" or "acpi=force" are available
1da177e4 179
395cf969 180 See also Documentation/power/runtime_pm.txt, pci=noacpi
1da177e4 181
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182 acpi_apic_instance= [ACPI, IOAPIC]
183 Format: <int>
184 2: use 2nd APIC table, if available
185 1,0: use 1st APIC table
4e381a4f 186 default: 0
a1fdcc0d 187
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188 acpi_backlight= [HW,ACPI]
189 acpi_backlight=vendor
190 acpi_backlight=video
191 If set to vendor, prefer vendor specific driver
192 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
193 of the ACPI video.ko driver.
194
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195 acpica_no_return_repair [HW, ACPI]
196 Disable AML predefined validation mechanism
197 This mechanism can repair the evaluation result to make
198 the return objects more ACPI specification compliant.
199 This option is useful for developers to identify the
200 root cause of an AML interpreter issue when the issue
201 has something to do with the repair mechanism.
202
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203 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
204 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
1da177e4 205 Format: <int>
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206 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
207 debug output. Bits in debug_layer correspond to a
208 _COMPONENT in an ACPI source file, e.g.,
209 #define _COMPONENT ACPI_PCI_COMPONENT
210 Bits in debug_level correspond to a level in
211 ACPI_DEBUG_PRINT statements, e.g.,
212 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
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213 The debug_level mask defaults to "info". See
214 Documentation/acpi/debug.txt for more information about
215 debug layers and levels.
a0d84a92 216
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217 Enable processor driver info messages:
218 acpi.debug_layer=0x20000000
219 Enable PCI/PCI interrupt routing info messages:
220 acpi.debug_layer=0x400000
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221 Enable AML "Debug" output, i.e., stores to the Debug
222 object while interpreting AML:
223 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
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224 Enable all messages related to ACPI hardware:
225 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
226
227 Some values produce so much output that the system is
228 unusable. The "log_buf_len" parameter may be useful
229 if you need to capture more output.
f989106c 230
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231 acpi_enforce_resources= [ACPI]
232 { strict | lax | no }
233 Check for resource conflicts between native drivers
234 and ACPI OperationRegions (SystemIO and SystemMemory
235 only). IO ports and memory declared in ACPI might be
236 used by the ACPI subsystem in arbitrary AML code and
237 can interfere with legacy drivers.
238 strict (default): access to resources claimed by ACPI
239 is denied; legacy drivers trying to access reserved
240 resources will fail to bind to device using them.
241 lax: access to resources claimed by ACPI is allowed;
242 legacy drivers trying to access reserved resources
243 will bind successfully but a warning message is logged.
244 no: ACPI OperationRegions are not marked as reserved,
245 no further checks are performed.
246
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247 acpi_force_table_verification [HW,ACPI]
248 Enable table checksum verification during early stage.
249 By default, this is disabled due to x86 early mapping
250 size limitation.
251
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252 acpi_irq_balance [HW,ACPI]
253 ACPI will balance active IRQs
254 default in APIC mode
255
256 acpi_irq_nobalance [HW,ACPI]
257 ACPI will not move active IRQs (default)
258 default in PIC mode
259
260 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
261 Format: <irq>,<irq>...
262
263 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
264 use by PCI
265 Format: <irq>,<irq>...
266
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267 acpi_no_auto_serialize [HW,ACPI]
268 Disable auto-serialization of AML methods
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269 AML control methods that contain the opcodes to create
270 named objects will be marked as "Serialized" by the
271 auto-serialization feature.
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272 This feature is enabled by default.
273 This option allows to turn off the feature.
22b5afce 274
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275 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
276 kernels.
277
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278 acpi_no_static_ssdt [HW,ACPI]
279 Disable installation of static SSDTs at early boot time
280 By default, SSDTs contained in the RSDT/XSDT will be
281 installed automatically and they will appear under
282 /sys/firmware/acpi/tables.
283 This option turns off this feature.
284 Note that specifying this option does not affect
285 dynamic table installation which will install SSDT
286 tables to /sys/firmware/acpi/tables/dynamic.
0cb55ad2 287
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288 acpi_rsdp= [ACPI,EFI,KEXEC]
289 Pass the RSDP address to the kernel, mostly used
290 on machines running EFI runtime service to boot the
291 second kernel for kdump.
4dde507f 292
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293 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
294 Format: To spoof as Windows 98: ="Microsoft Windows"
295
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296 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
297 of 2 which is mandated by ACPI 6) as the supported ACPI
298 specification revision (when using this switch, it may
299 be necessary to carry out a cold reboot _twice_ in a
300 row to make it take effect on the platform firmware).
301
0cb55ad2 302 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
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303 acpi_osi="string1" # add string1
304 acpi_osi="!string2" # remove string2
741d8128 305 acpi_osi=!* # remove all strings
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306 acpi_osi=! # disable all built-in OS vendor
307 strings
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308 acpi_osi= # disable all strings
309
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310 'acpi_osi=!' can be used in combination with single or
311 multiple 'acpi_osi="string1"' to support specific OS
312 vendor string(s). Note that such command can only
313 affect the default state of the OS vendor strings, thus
314 it cannot affect the default state of the feature group
315 strings and the current state of the OS vendor strings,
316 specifying it multiple times through kernel command line
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317 is meaningless. This command is useful when one do not
318 care about the state of the feature group strings which
319 should be controlled by the OSPM.
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320 Examples:
321 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
322 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
323 can make '_OSI("Windows 2000")' TRUE.
324
325 'acpi_osi=' cannot be used in combination with other
326 'acpi_osi=' command lines, the _OSI method will not
327 exist in the ACPI namespace. NOTE that such command can
328 only affect the _OSI support state, thus specifying it
329 multiple times through kernel command line is also
330 meaningless.
331 Examples:
332 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
333 FALSE.
334
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335 'acpi_osi=!*' can be used in combination with single or
336 multiple 'acpi_osi="string1"' to support specific
337 string(s). Note that such command can affect the
338 current state of both the OS vendor strings and the
339 feature group strings, thus specifying it multiple times
340 through kernel command line is meaningful. But it may
341 still not able to affect the final state of a string if
342 there are quirks related to this string. This command
343 is useful when one want to control the state of the
344 feature group strings to debug BIOS issues related to
345 the OSPM features.
346 Examples:
347 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
348 '_OSI("Module Device")' FALSE.
349 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
350 '_OSI("Module Device")' TRUE.
351 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
352 equivalent to
353 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
354 and
355 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
356 they all will make '_OSI("Windows 2000")' TRUE.
357
6cececfc 358 acpi_pm_good [X86]
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359 Override the pmtimer bug detection: force the kernel
360 to assume that this machine's pmtimer latches its value
361 and always returns good values.
362
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363 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
364 Format: { level | edge | high | low }
365
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366 acpi_skip_timer_override [HW,ACPI]
367 Recognize and ignore IRQ0/pin2 Interrupt Override.
368 For broken nForce2 BIOS resulting in XT-PIC timer.
369
370 acpi_sleep= [HW,ACPI] Sleep options
371 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
c3b0795c 372 old_ordering, nonvs, sci_force_enable }
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373 See Documentation/power/video.txt for information on
374 s3_bios and s3_mode.
375 s3_beep is for debugging; it makes the PC's speaker beep
376 as soon as the kernel's real-mode entry point is called.
377 s4_nohwsig prevents ACPI hardware signature from being
378 used during resume from hibernation.
379 old_ordering causes the ACPI 1.0 ordering of the _PTS
380 control method, with respect to putting devices into
381 low power states, to be enforced (the ACPI 2.0 ordering
382 of _PTS is used by default).
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383 nonvs prevents the kernel from saving/restoring the
384 ACPI NVS memory during suspend/hibernation and resume.
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385 sci_force_enable causes the kernel to set SCI_EN directly
386 on resume from S1/S3 (which is against the ACPI spec,
387 but some broken systems don't work without it).
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388
389 acpi_use_timer_override [HW,ACPI]
390 Use timer override. For some broken Nvidia NF5 boards
391 that require a timer override, but don't have HPET
392
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393 add_efi_memmap [EFI; X86] Include EFI memory map in
394 kernel's map of available physical RAM.
395
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396 agp= [AGP]
397 { off | try_unsupported }
398 off: disable AGP support
399 try_unsupported: try to drive unsupported chipsets
400 (may crash computer or cause data corruption)
401
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402 ALSA [HW,ALSA]
403 See Documentation/sound/alsa/alsa-parameters.txt
404
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405 alignment= [KNL,ARM]
406 Allow the default userspace alignment fault handler
407 behaviour to be specified. Bit 0 enables warnings,
408 bit 1 enables fixups, and bit 2 sends a segfault.
409
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410 align_va_addr= [X86-64]
411 Align virtual addresses by clearing slice [14:12] when
412 allocating a VMA at process creation time. This option
413 gives you up to 3% performance improvement on AMD F15h
414 machines (where it is enabled by default) for a
415 CPU-intensive style benchmark, and it can vary highly in
416 a microbenchmark depending on workload and compiler.
417
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418 32: only for 32-bit processes
419 64: only for 64-bit processes
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420 on: enable for both 32- and 64-bit processes
421 off: disable for both 32- and 64-bit processes
422
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423 alloc_snapshot [FTRACE]
424 Allocate the ftrace snapshot buffer on boot up when the
425 main buffer is allocated. This is handy if debugging
426 and you need to use tracing_snapshot() on boot up, and
427 do not want to use tracing_snapshot_alloc() as it needs
428 to be done where GFP_KERNEL allocations are allowed.
429
89e0b9a3 430 amd_iommu= [HW,X86-64]
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431 Pass parameters to the AMD IOMMU driver in the system.
432 Possible values are:
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433 fullflush - enable flushing of IO/TLB entries when
434 they are unmapped. Otherwise they are
435 flushed before they will be reused, which
436 is a lot of faster
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437 off - do not initialize any AMD IOMMU found in
438 the system
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439 force_isolation - Force device isolation for all
440 devices. The IOMMU driver is not
441 allowed anymore to lift isolation
442 requirements as needed. This option
443 does not override iommu=pt
afa9fdc2 444
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445 amd_iommu_dump= [HW,X86-64]
446 Enable AMD IOMMU driver option to dump the ACPI table
447 for AMD IOMMU. With this option enabled, AMD IOMMU
448 driver will print ACPI tables for AMD IOMMU during
449 IOMMU initialization.
450
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451 amijoy.map= [HW,JOY] Amiga joystick support
452 Map of devices attached to JOY0DAT and JOY1DAT
453 Format: <a>,<b>
395cf969 454 See also Documentation/input/joystick.txt
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455
456 analog.map= [HW,JOY] Analog joystick and gamepad support
457 Specifies type or capabilities of an analog joystick
458 connected to one of 16 gameports
459 Format: <type1>,<type2>,..<type16>
460
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461 apc= [HW,SPARC]
462 Power management functions (SPARCstation-4/5 + deriv.)
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463 Format: noidle
464 Disable APC CPU standby support. SPARCstation-Fox does
465 not play well with APC CPU idle - disable it if you have
466 APC and your system crashes randomly.
467
ca1eda2d 468 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
c8facbb6 469 Change the output verbosity whilst booting
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470 Format: { quiet (default) | verbose | debug }
471 Change the amount of debugging information output
472 when initialising the APIC and IO-APIC components.
a9913044 473
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474 autoconf= [IPV6]
475 See Documentation/networking/ipv6.txt.
476
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477 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
478 Limit apic dumping. The parameter defines the maximal
479 number of local apics being dumped. Also it is possible
480 to set it to "all" by meaning -- no limit here.
481 Format: { 1 (default) | 2 | ... | all }.
482 The parameter valid if only apic=debug or
483 apic=verbose is specified.
484 Example: apic=debug show_lapic=all
485
1da177e4 486 apm= [APM] Advanced Power Management
71f77055 487 See header of arch/x86/kernel/apm_32.c.
1da177e4 488
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489 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
490 Format: <io>,<irq>,<nodeID>
491
492 ataflop= [HW,M68k]
493
494 atarimouse= [HW,MOUSE] Atari Mouse
495
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496 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
497 EzKey and similar keyboards
498
499 atkbd.reset= [HW] Reset keyboard during initialization
500
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501 atkbd.set= [HW] Select keyboard code set
502 Format: <int> (2 = AT (default), 3 = PS/2)
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503
504 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
505 keyboards
506
507 atkbd.softraw= [HW] Choose between synthetic and real raw mode
508 Format: <bool> (0 = real, 1 = synthetic (default))
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509
510 atkbd.softrepeat= [HW]
511 Use software keyboard repeat
1da177e4 512
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513 audit= [KNL] Enable the audit sub-system
514 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
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515 0 - kernel audit is disabled and can not be enabled
516 until the next reboot
517 unset - kernel audit is initialized but disabled and
518 will be fully enabled by the userspace auditd.
519 1 - kernel audit is initialized and partially enabled,
520 storing at most audit_backlog_limit messages in
521 RAM until it is fully enabled by the userspace
522 auditd.
a106fb0c 523 Default: unset
f3411cb2 524
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525 audit_backlog_limit= [KNL] Set the audit queue size limit.
526 Format: <int> (must be >=0)
527 Default: 64
528
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529 baycom_epp= [HW,AX25]
530 Format: <io>,<mode>
a9913044 531
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LT
532 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
533 Format: <io>,<mode>
534 See header of drivers/net/hamradio/baycom_par.c.
535
a9913044
RD
536 baycom_ser_fdx= [HW,AX25]
537 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
1da177e4
LT
538 Format: <io>,<irq>,<mode>[,<baud>]
539 See header of drivers/net/hamradio/baycom_ser_fdx.c.
540
a9913044
RD
541 baycom_ser_hdx= [HW,AX25]
542 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
1da177e4
LT
543 Format: <io>,<irq>,<mode>
544 See header of drivers/net/hamradio/baycom_ser_hdx.c.
545
080506ad
PG
546 blkdevparts= Manual partition parsing of block device(s) for
547 embedded devices based on command line input.
548 See Documentation/block/cmdline-partition.txt
549
bfe8df3d
RD
550 boot_delay= Milliseconds to delay each printk during boot.
551 Values larger than 10 seconds (10000) are changed to
552 no delay (0).
553 Format: integer
554
35fc908d
AH
555 bootmem_debug [KNL] Enable bootmem allocator debug messages.
556
1da177e4 557 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
a9913044
RD
558 bttv.radio= Most important insmod options are available as
559 kernel args too.
1da177e4 560 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
395cf969 561 bttv.tuner=
1da177e4 562
4e89a2d8
WS
563 bulk_remove=off [PPC] This parameter disables the use of the pSeries
564 firmware feature for flushing multiple hpte entries
565 at a time.
566
1da177e4
LT
567 c101= [NET] Moxa C101 synchronous serial card
568
cd4f0ef7 569 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
1da177e4
LT
570 Sometimes CPU hardware bugs make them report the cache
571 size incorrectly. The kernel will attempt work arounds
572 to fix known problems, but for some CPUs it is not
573 possible to determine what the correct size should be.
574 This option provides an override for these situations.
575
ffb70f61
DK
576 ca_keys= [KEYS] This parameter identifies a specific key(s) on
577 the system trusted keyring to be used for certificate
578 trust validation.
32c4741c 579 format: { id:<keyid> | builtin }
ffb70f61 580
fd1bb4c9
FF
581 cca= [MIPS] Override the kernel pages' cache coherency
582 algorithm. Accepted values range from 0 to 7
583 inclusive. See arch/mips/include/asm/pgtable-bits.h
584 for platform specific values (SB1, Loongson3 and
585 others).
586
14ff56bb
SO
587 ccw_timeout_log [S390]
588 See Documentation/s390/CommonIO for details.
1da177e4 589
8bab8dde
PM
590 cgroup_disable= [KNL] Disable a particular controller
591 Format: {name of the controller(s) to disable}
ca0bdbb5
QH
592 The effects of cgroup_disable=foo are:
593 - foo isn't auto-mounted if you mount all cgroups in
594 a single hierarchy
595 - foo isn't visible as an individually mountable
596 subsystem
597 {Currently only "memory" controller deal with this and
598 cut the overhead, others just disable the usage. So
599 only cgroup_disable=memory is actually worthy}
8bab8dde 600
1da177e4
LT
601 checkreqprot [SELINUX] Set initial checkreqprot flag value.
602 Format: { "0" | "1" }
603 See security/selinux/Kconfig help text.
a9913044
RD
604 0 -- check protection applied by kernel (includes
605 any implied execute protection).
1da177e4
LT
606 1 -- check protection requested by application.
607 Default value is set via a kernel config option.
a9913044
RD
608 Value can be changed at runtime via
609 /selinux/checkreqprot.
610
661ca0da
SO
611 cio_ignore= [S390]
612 See Documentation/s390/CommonIO for details.
1e435256
OJ
613 clk_ignore_unused
614 [CLK]
e156ee56
MT
615 Prevents the clock framework from automatically gating
616 clocks that have not been explicitly enabled by a Linux
617 device driver but are enabled in hardware at reset or
618 by the bootloader/firmware. Note that this does not
619 force such clocks to be always-on nor does it reserve
620 those clocks in any way. This parameter is useful for
621 debug and development, but should not be needed on a
622 platform with proper driver support. For more
623 information, see Documentation/clk.txt.
661ca0da 624
cd4f0ef7 625 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
734efb46 626 [Deprecated]
3f6dee9b 627 Forces specified clocksource (if available) to be used
734efb46 628 when calculating gettimeofday(). If specified
3f6dee9b 629 clocksource is not available, it defaults to PIT.
1da177e4
LT
630 Format: { pit | tsc | cyclone | pmtmr }
631
592913ec 632 clocksource= Override the default clocksource
3d6ac984
RD
633 Format: <string>
634 Override the default clocksource and use the clocksource
635 with the name specified.
636 Some clocksource names to choose from, depending on
637 the platform:
638 [all] jiffies (this is the base, fallback clocksource)
639 [ACPI] acpi_pm
640 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
641 pxa_timer,timer3,32k_counter,timer0_1
642 [AVR32] avr32
9863c90f 643 [X86-32] pit,hpet,tsc;
3d6ac984
RD
644 scx200_hrt on Geode; cyclone on IBM x440
645 [MIPS] MIPS
646 [PARISC] cr16
647 [S390] tod
648 [SH] SuperH
649 [SPARC64] tick
650 [X86-64] hpet,tsc
651
ac72e788
AK
652 clearcpuid=BITNUM [X86]
653 Disable CPUID feature X for the kernel. See
07983f0e
RD
654 arch/x86/include/asm/cpufeature.h for the valid bit
655 numbers. Note the Linux specific bits are not necessarily
ac72e788
AK
656 stable over kernel options, but the vendor specific
657 ones should be.
658 Also note that user programs calling CPUID directly
659 or using the feature without checking anything
660 will still see it. This just prevents it from
661 being used by the kernel or shown in /proc/cpuinfo.
662 Also note the kernel might malfunction if you disable
663 some critical bits.
664
5ea3b1b2
AM
665 cma=nn[MG]@[start[MG][-end[MG]]]
666 [ARM,X86,KNL]
667 Sets the size of kernel global memory area for
668 contiguous memory allocations and optionally the
669 placement constraint by the physical address range of
f0d6d1f6
JD
670 memory allocations. A value of 0 disables CMA
671 altogether. For more information, see
c64be2bb
MS
672 include/linux/dma-contiguous.h
673
14f966e7
RJ
674 cmo_free_hint= [PPC] Format: { yes | no }
675 Specify whether pages are marked as being inactive
676 when they are freed. This is used in CMO environments
677 to determine OS memory pressure for page stealing by
678 a hypervisor.
679 Default: yes
680
c7909509
MS
681 coherent_pool=nn[KMG] [ARM,KNL]
682 Sets the size of memory pool for coherent, atomic dma
e9da6e99 683 allocations, by default set to 256K.
c7909509 684
6cececfc 685 code_bytes [X86] How many bytes of object code to print
a25bd949 686 in an oops report.
86c41837
CE
687 Range: 0 - 8192
688 Default: 64
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
716 See Documentation/serial-console.txt for more
717 information. See
718 Documentation/networking/netconsole.txt for an
719 alternative.
1da177e4 720
18a8bd94
YL
721 uart[8250],io,<addr>[,options]
722 uart[8250],mmio,<addr>[,options]
ca782f16
PH
723 uart[8250],mmio32,<addr>[,options]
724 uart[8250],0x<addr>[,options]
1da177e4
LT
725 Start an early, polled-mode console on the 8250/16550
726 UART at the specified I/O port or MMIO address,
ca782f16
PH
727 switching to the matching ttyS device later.
728 MMIO inter-register address stride is either 8-bit
729 (mmio) or 32-bit (mmio32).
730 If none of [io|mmio|mmio32], <addr> is assumed to be
731 equivalent to 'mmio'. 'options' are specified in the
732 same format described for ttyS above; if unspecified,
733 the h/w is not re-initialized.
734
a2fd6419
KRW
735 hvc<n> Use the hypervisor console device <n>. This is for
736 both Xen and PowerPC hypervisors.
1da177e4 737
f7511d5f
ST
738 If the device connected to the port is not a TTY but a braille
739 device, prepend "brl," before the device type, for instance
740 console=brl,ttyS0
741 For now, only VisioBraille is supported.
742
f324edc8
DM
743 consoleblank= [KNL] The console blank (screen saver) timeout in
744 seconds. Defaults to 10*60 = 10mins. A value of 0
745 disables the blank timer.
746
4cb0e11b
HK
747 coredump_filter=
748 [KNL] Change the default value for
749 /proc/<pid>/coredump_filter.
750 See also Documentation/filesystems/proc.txt.
751
62027aea
LB
752 cpuidle.off=1 [CPU_IDLE]
753 disable the cpuidle sub-system
754
d68921f9
LB
755 cpu_init_udelay=N
756 [X86] Delay for N microsec between assert and de-assert
757 of APIC INIT to start processors. This delay occurs
758 on every CPU online, such as boot, and resume from suspend.
759 Default: 10000
760
1da177e4 761 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
a9913044
RD
762 Format:
763 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
1da177e4 764
6f21e646
AD
765 crashkernel=size[KMG][@offset[KMG]]
766 [KNL] Using kexec, Linux can switch to a 'crash kernel'
767 upon panic. This parameter reserves the physical
768 memory region [offset, offset + size] for that kernel
769 image. If '@offset' is omitted, then a suitable offset
770 is selected automatically. Check
771 Documentation/kdump/kdump.txt for further details.
dc009d92 772
fb391599
BW
773 crashkernel=range1:size1[,range2:size2,...][@offset]
774 [KNL] Same as above, but depends on the memory
775 in the running system. The syntax of range is
776 start-[end] where start and end are both
777 a memory unit (amount[KMG]). See also
6f21e646 778 Documentation/kdump/kdump.txt for an example.
fb391599 779
adbc742b 780 crashkernel=size[KMG],high
55a20ee7
YL
781 [KNL, x86_64] range could be above 4G. Allow kernel
782 to allocate physical memory region from top, so could
783 be above 4G if system have more than 4G ram installed.
784 Otherwise memory region will be allocated below 4G, if
785 available.
786 It will be ignored if crashkernel=X is specified.
adbc742b
YL
787 crashkernel=size[KMG],low
788 [KNL, x86_64] range under 4G. When crashkernel=X,high
789 is passed, kernel could allocate physical memory region
c729de8f
YL
790 above 4G, that cause second kernel crash on system
791 that require some amount of low memory, e.g. swiotlb
792 requires at least 64M+32K low memory. Kernel would
793 try to allocate 72M below 4G automatically.
794 This one let user to specify own low range under 4G
795 for second kernel instead.
796 0: to disable low allocation.
adbc742b 797 It will be ignored when crashkernel=X,high is not used
55a20ee7 798 or memory reserved is below 4G.
c729de8f 799
1da177e4
LT
800 cs89x0_dma= [HW,NET]
801 Format: <dma>
802
803 cs89x0_media= [HW,NET]
804 Format: { rj45 | aui | bnc }
a9913044 805
a9913044 806 dasd= [HW,NET]
1da177e4
LT
807 See header of drivers/s390/block/dasd_devmap.c.
808
809 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
810 (one device per port)
811 Format: <port#>,<type>
812 See also Documentation/input/joystick-parport.txt
813
a648ec05
TR
814 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
815 time. See Documentation/dynamic-debug-howto.txt for
29e36c9f 816 details. Deprecated, see dyndbg.
a648ec05 817
1da177e4
LT
818 debug [KNL] Enable kernel debugging (events log level).
819
cae2ed9a
IM
820 debug_locks_verbose=
821 [KNL] verbose self-tests
822 Format=<0|1>
823 Print debugging info while doing the locking API
824 self-tests.
825 We default to 0 (no extra messages), setting it to
826 1 will print _a lot_ more information - normally
827 only useful to kernel developers.
828
3ac7fe5a
TG
829 debug_objects [KNL] Enable object debugging
830
3e8ebb5c
KM
831 no_debug_objects
832 [KNL] Disable object debugging
833
c0a32fc5
SG
834 debug_guardpage_minorder=
835 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
836 parameter allows control of the order of pages that will
837 be intentionally kept free (and hence protected) by the
838 buddy allocator. Bigger value increase the probability
839 of catching random memory corruption, but reduce the
840 amount of memory for normal system use. The maximum
841 possible value is MAX_ORDER/2. Setting this parameter
842 to 1 or 2 should be enough to identify most random
843 memory corruption problems caused by bugs in kernel or
844 driver code when a CPU writes to (or reads from) a
845 random memory location. Note that there exists a class
846 of memory corruptions problems caused by buggy H/W or
847 F/W or by drivers badly programing DMA (basically when
848 memory is written at bus level and the CPU MMU is
849 bypassed) which are not detectable by
850 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
851 tracking down these problems.
852
031bc574
JK
853 debug_pagealloc=
854 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
855 parameter enables the feature at boot time. In
856 default, it is disabled. We can avoid allocating huge
857 chunk of memory for debug pagealloc if we don't enable
858 it at boot time and the system will work mostly same
859 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
860 on: enable the feature
861
d3af01f1
TG
862 debugpat [X86] Enable PAT debugging
863
2d27a966 864 decnet.addr= [HW,NET]
1da177e4
LT
865 Format: <area>[,<node>]
866 See also Documentation/networking/decnet.txt.
867
0cb55ad2
RD
868 default_hugepagesz=
869 [same as hugepagesz=] The size of the default
870 HugeTLB page size. This is the size represented by
871 the legacy /proc/ hugepages APIs, used for SHM, and
872 default size when mounting hugetlbfs filesystems.
873 Defaults to the default architecture's huge page size
874 if not specified.
55ff9780 875
1da177e4
LT
876 dhash_entries= [KNL]
877 Set number of hash buckets for dentry cache.
a9913044 878
b0f83b28
BH
879 disable= [IPV6]
880 See Documentation/networking/ipv6.txt.
881
151e0c7d
HD
882 disable_cpu_apicid= [X86,APIC,SMP]
883 Format: <int>
884 The number of initial APIC ID for the
885 corresponding CPU to be disabled at boot,
886 mostly used for the kdump 2nd kernel to
887 disable BSP to wake up multiple CPUs without
888 causing system reset or hang due to sending
889 INIT from AP to BSP.
890
4e8b0cf4
NA
891 disable_ddw [PPC/PSERIES]
892 Disable Dynamic DMA Window support. Use this if
893 to workaround buggy firmware.
894
b0f83b28
BH
895 disable_ipv6= [IPV6]
896 See Documentation/networking/ipv6.txt.
897
95ffa243 898 disable_mtrr_cleanup [X86]
95ffa243
YL
899 The kernel tries to adjust MTRR layout from continuous
900 to discrete, to make X server driver able to add WB
0cb55ad2 901 entry later. This parameter disables that.
95ffa243 902
093af8d7 903 disable_mtrr_trim [X86, Intel and AMD only]
99fc8d42
JB
904 By default the kernel will trim any uncacheable
905 memory out of your available memory pool based on
906 MTRR settings. This parameter disables that behavior,
907 possibly causing your machine to run very slowly.
908
6cececfc 909 disable_timer_pin_1 [X86]
0cb55ad2
RD
910 Disable PIN 1 of APIC timer
911 Can be useful to work around chipset bugs.
912
0cb55ad2
RD
913 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
914 this option disables the debugging code at boot.
915
916 dma_debug_entries=<number>
917 This option allows to tune the number of preallocated
918 entries for DMA-API debugging code. One entry is
919 required per DMA-API allocation. Use this if the
920 DMA-API debugging code disables itself because the
921 architectural default is too low.
922
1745de5e
JR
923 dma_debug_driver=<driver_name>
924 With this option the DMA-API debugging driver
925 filter feature can be enabled at boot time. Just
926 pass the driver to filter for as the parameter.
927 The filter can be disabled or changed to another
928 driver later using sysfs.
929
da0df92b
CE
930 drm_kms_helper.edid_firmware=[<connector>:]<file>
931 Broken monitors, graphic adapters and KVMs may
932 send no or incorrect EDID data sets. This parameter
933 allows to specify an EDID data set in the
934 /lib/firmware directory that is used instead.
935 Generic built-in EDID data sets are used, if one of
936 edid/1024x768.bin, edid/1280x1024.bin,
937 edid/1680x1050.bin, or edid/1920x1080.bin is given
938 and no file with the same name exists. Details and
939 instructions how to build your own EDID data are
940 available in Documentation/EDID/HOWTO.txt. An EDID
941 data set will only be used for a particular connector,
942 if its name and a colon are prepended to the EDID
943 name.
944
1da177e4
LT
945 dscc4.setup= [NET]
946
29e36c9f
JC
947 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
948 module.dyndbg[="val"]
949 Enable debug messages at boot time. See
950 Documentation/dynamic-debug-howto.txt for details.
951
8c3641e9
DH
952 nompx [X86] Disables Intel Memory Protection Extensions.
953 See Documentation/x86/intel_mpx.txt for more
954 information about the feature.
955
f29ba61d
BP
956 eagerfpu= [X86]
957 on enable eager fpu restore
958 off disable eager fpu restore
959 auto selects the default scheme, which automatically
960 enables eagerfpu restore for xsaveopt.
961
f2411da7
LR
962 module.async_probe [KNL]
963 Enable asynchronous probe on this module.
964
56aeeba8
MS
965 early_ioremap_debug [KNL]
966 Enable debug messages in early_ioremap support. This
967 is useful for tracking down temporary early mappings
968 which are not unmapped.
969
0cb55ad2 970 earlycon= [KNL] Output early console device and options.
0d3c673e 971
6fa62fc4
MS
972 cdns,<addr>
973 Start an early, polled-mode console on a cadence serial
974 port at the specified address. The cadence serial port
975 must already be setup and configured. Options are not
976 yet supported.
977
0cb55ad2
RD
978 uart[8250],io,<addr>[,options]
979 uart[8250],mmio,<addr>[,options]
1917ac76 980 uart[8250],mmio32,<addr>[,options]
6e63be3f 981 uart[8250],mmio32be,<addr>[,options]
ca782f16 982 uart[8250],0x<addr>[,options]
0cb55ad2
RD
983 Start an early, polled-mode console on the 8250/16550
984 UART at the specified I/O port or MMIO address.
16290246 985 MMIO inter-register address stride is either 8-bit
6e63be3f
NC
986 (mmio) or 32-bit (mmio32 or mmio32be).
987 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
988 to be equivalent to 'mmio'. 'options' are specified
989 in the same format described for "console=ttyS<n>"; if
ca782f16 990 unspecified, the h/w is not initialized.
0cb55ad2 991
0d3c673e
RH
992 pl011,<addr>
993 Start an early, polled-mode console on a pl011 serial
994 port at the specified address. The pl011 serial port
995 must already be setup and configured. Options are not
996 yet supported.
997
0efe7296
SB
998 msm_serial,<addr>
999 Start an early, polled-mode console on an msm serial
1000 port at the specified address. The serial port
1001 must already be setup and configured. Options are not
1002 yet supported.
1003
1004 msm_serial_dm,<addr>
1005 Start an early, polled-mode console on an msm serial
1006 dm port at the specified address. The serial port
1007 must already be setup and configured. Options are not
1008 yet supported.
1009
d50d7269
RH
1010 smh Use ARM semihosting calls for early console.
1011
b94ba032
TF
1012 s3c2410,<addr>
1013 s3c2412,<addr>
1014 s3c2440,<addr>
1015 s3c6400,<addr>
1016 s5pv210,<addr>
1017 exynos4210,<addr>
1018 Use early console provided by serial driver available
1019 on Samsung SoCs, requires selecting proper type and
1020 a correct base address of the selected UART port. The
1021 serial port must already be setup and configured.
1022 Options are not yet supported.
1023
7913ad1a 1024 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1da177e4 1025 earlyprintk=vga
72548e83 1026 earlyprintk=efi
2482a92e 1027 earlyprintk=xen
1da177e4 1028 earlyprintk=serial[,ttySn[,baudrate]]
147ea091 1029 earlyprintk=serial[,0x...[,baudrate]]
ea3acb19 1030 earlyprintk=ttySn[,baudrate]
9780bc41 1031 earlyprintk=dbgp[debugController#]
c43088e3 1032 earlyprintk=pciserial,bus:device.function[,baudrate]
1da177e4 1033
147ea091
DH
1034 earlyprintk is useful when the kernel crashes before
1035 the normal console is initialized. It is not enabled by
1036 default because it has some cosmetic problems.
1037
a9913044 1038 Append ",keep" to not disable it when the real console
1da177e4
LT
1039 takes over.
1040
72548e83
MF
1041 Only one of vga, efi, serial, or usb debug port can
1042 be used at a time.
1da177e4 1043
147ea091
DH
1044 Currently only ttyS0 and ttyS1 may be specified by
1045 name. Other I/O ports may be explicitly specified
1046 on some architectures (x86 and arm at least) by
1047 replacing ttySn with an I/O port address, like this:
1048 earlyprintk=serial,0x1008,115200
1049 You can find the port for a given device in
1050 /proc/tty/driver/serial:
1051 2: uart:ST16650V2 port:00001008 irq:18 ...
1da177e4
LT
1052
1053 Interaction with the standard serial driver is not
1054 very good.
1055
72548e83
MF
1056 The VGA and EFI output is eventually overwritten by
1057 the real console.
1da177e4 1058
2482a92e
KRW
1059 The xen output can only be used by Xen PV guests.
1060
c700f013
CG
1061 edac_report= [HW,EDAC] Control how to report EDAC event
1062 Format: {"on" | "off" | "force"}
1063 on: enable EDAC to report H/W event. May be overridden
1064 by other higher priority error reporting module.
1065 off: disable H/W event reporting through EDAC.
1066 force: enforce the use of EDAC to report H/W event.
1067 default: on.
1068
9731191f
JW
1069 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1070 ekgdboc=kbd
1071
25985edc 1072 This is designed to be used in conjunction with
9731191f
JW
1073 the boot argument: earlyprintk=vga
1074
1da177e4 1075 edd= [EDD]
8c4dd606 1076 Format: {"off" | "on" | "skip[mbr]"}
1da177e4 1077
d2f7cbe7 1078 efi= [EFI]
fed6cefe 1079 Format: { "old_map", "nochunk", "noruntime", "debug" }
d2f7cbe7
BP
1080 old_map [X86-64]: switch to the old ioremap-based EFI
1081 runtime services mapping. 32-bit still uses this one by
1082 default.
5a17dae4
MF
1083 nochunk: disable reading files in "chunks" in the EFI
1084 boot stub, as chunking can cause problems with some
1085 firmware implementations.
5ae3683c 1086 noruntime : disable EFI runtime services support
fed6cefe 1087 debug: enable misc debug output
d2f7cbe7 1088
8c58bf3e
RW
1089 efi_no_storage_paranoia [EFI; X86]
1090 Using this parameter you can use more than 50% of
1091 your efi variable storage. Use this parameter only if
1092 you are really sure that your UEFI does sane gc and
1093 fulfills the spec otherwise your board may brick.
1094
0f96a99d
TI
1095 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1096 Add arbitrary attribute to specific memory range by
1097 updating original EFI memory map.
1098 Region of memory which aa attribute is added to is
1099 from ss to ss+nn.
1100 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1101 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1102 attribute is added to range 0x100000000-0x180000000 and
1103 0x10a0000000-0x1120000000.
1104
1105 Using this parameter you can do debugging of EFI memmap
1106 related feature. For example, you can do debugging of
1107 Address Range Mirroring feature even if your box
1108 doesn't support it.
1109
1da177e4
LT
1110 eisa_irq_edge= [PARISC,HW]
1111 See header of drivers/parisc/eisa.c.
1112
cd4f0ef7 1113 elanfreq= [X86-32]
1da177e4 1114 See comment before function elanfreq_setup() in
71f77055 1115 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1da177e4
LT
1116
1117 elevator= [IOSCHED]
17a9e7bb 1118 Format: {"cfq" | "deadline" | "noop"}
395cf969 1119 See Documentation/block/cfq-iosched.txt and
a9913044
RD
1120 Documentation/block/deadline-iosched.txt for details.
1121
d3bf3795 1122 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
a9913044 1123 Specifies physical address of start of kernel core
d3bf3795
MH
1124 image elf header and optionally the size. Generally
1125 kexec loader will pass this option to capture kernel.
aac04b32 1126 See Documentation/kdump/kdump.txt for details.
1da177e4 1127
0cb55ad2
RD
1128 enable_mtrr_cleanup [X86]
1129 The kernel tries to adjust MTRR layout from continuous
1130 to discrete, to make X server driver able to add WB
1131 entry later. This parameter enables that.
1132
ca1eda2d 1133 enable_timer_pin_1 [X86]
0cb55ad2
RD
1134 Enable PIN 1 of APIC timer
1135 Can be useful to work around chipset bugs
1136 (in particular on some ATI chipsets).
1137 The kernel tries to set a reasonable default.
1138
1da177e4
LT
1139 enforcing [SELINUX] Set initial enforcing status.
1140 Format: {"0" | "1"}
1141 See security/selinux/Kconfig help text.
1142 0 -- permissive (log only, no denials).
1143 1 -- enforcing (deny and log).
1144 Default value is 0.
1145 Value can be changed at runtime via /selinux/enforce.
1146
a08f82d0
HY
1147 erst_disable [ACPI]
1148 Disable Error Record Serialization Table (ERST)
1149 support.
1150
1da177e4
LT
1151 ether= [HW,NET] Ethernet cards parameters
1152 This option is obsoleted by the "netdev=" option, which
1153 has equivalent usage. See its documentation for details.
1154
7102ebcd
MZ
1155 evm= [EVM]
1156 Format: { "fix" }
1157 Permit 'security.evm' to be updated regardless of
1158 current integrity status.
1159
de1ba09b
AM
1160 failslab=
1161 fail_page_alloc=
1162 fail_make_request=[KNL]
1163 General fault injection mechanism.
1164 Format: <interval>,<probability>,<space>,<times>
395cf969 1165 See also Documentation/fault-injection/.
de1ba09b 1166
1da177e4 1167 floppy= [HW]
31c00fc1 1168 See Documentation/blockdev/floppy.txt.
1da177e4 1169
f13ae30e
AC
1170 force_pal_cache_flush
1171 [IA-64] Avoid check_sal_cache_flush which may hang on
1172 buggy SAL_CACHE_FLUSH implementations. Using this
1173 parameter will force ia64_sal_cache_flush to call
1174 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1175
69f2366c
CB
1176 forcepae [X86-32]
1177 Forcefully enable Physical Address Extension (PAE).
1178 Many Pentium M systems disable PAE but may have a
1179 functionally usable PAE implementation.
1180 Warning: use of this parameter will taint the kernel
1181 and may cause unknown problems.
1182
d9e54076 1183 ftrace=[tracer]
2af15d6a 1184 [FTRACE] will set and start the specified tracer
d9e54076
PZ
1185 as early as possible in order to facilitate early
1186 boot debugging.
1187
cecbca96 1188 ftrace_dump_on_oops[=orig_cpu]
2af15d6a 1189 [FTRACE] will dump the trace buffers on oops.
cecbca96
FW
1190 If no parameter is passed, ftrace will dump
1191 buffers of all CPUs, but if you pass orig_cpu, it will
1192 dump only the buffer of the CPU that triggered the
1193 oops.
2af15d6a
SR
1194
1195 ftrace_filter=[function-list]
1196 [FTRACE] Limit the functions traced by the function
1197 tracer at boot up. function-list is a comma separated
1198 list of functions. This list can be changed at run
1199 time by the set_ftrace_filter file in the debugfs
16290246 1200 tracing directory.
2af15d6a
SR
1201
1202 ftrace_notrace=[function-list]
1203 [FTRACE] Do not trace the functions specified in
1204 function-list. This list can be changed at run time
1205 by the set_ftrace_notrace file in the debugfs
1206 tracing directory.
d9e54076 1207
369bc18f
SA
1208 ftrace_graph_filter=[function-list]
1209 [FTRACE] Limit the top level callers functions traced
1210 by the function graph tracer at boot up.
1211 function-list is a comma separated list of functions
1212 that can be changed at run time by the
1213 set_graph_function file in the debugfs tracing directory.
1214
0d7d9a16
NK
1215 ftrace_graph_notrace=[function-list]
1216 [FTRACE] Do not trace from the functions specified in
1217 function-list. This list is a comma separated list of
1218 functions that can be changed at run time by the
1219 set_graph_notrace file in the debugfs tracing directory.
1220
1da177e4
LT
1221 gamecon.map[2|3]=
1222 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1223 support via parallel port (up to 5 devices per port)
1224 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1225 See also Documentation/input/joystick-parport.txt
1226
1227 gamma= [HW,DRM]
1228
aaf23042
YL
1229 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1230 Format: off | on
1231 default: on
1232
2521f2c2
PO
1233 gcov_persist= [GCOV] When non-zero (default), profiling data for
1234 kernel modules is saved and remains accessible via
1235 debugfs, even when the module is unloaded/reloaded.
1236 When zero, profiling data is discarded and associated
1237 debugfs files are removed at module unload time.
1238
1da177e4 1239 gpt [EFI] Forces disk with valid GPT signature but
6c5de79b
DB
1240 invalid Protective MBR to be treated as GPT. If the
1241 primary GPT is corrupted, it enables the backup/alternate
1242 GPT to be used instead.
1da177e4 1243
6cec9b07
AL
1244 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1245 the "Enable 0" bit of the configuration register.
1246 Format: 0 | 1
1247 Default: 0
1248 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1249 the "Enable 0" bit of the configuration register.
1250 Format: 0 | 1
1251 Default: 0
1252 grcan.select= [HW] Select which physical interface to use.
1253 Format: 0 | 1
1254 Default: 0
1255 grcan.txsize= [HW] Sets the size of the tx buffer.
1256 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1257 Default: 1024
1258 grcan.rxsize= [HW] Sets the size of the rx buffer.
1259 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1260 Default: 1024
1261
1da177e4
LT
1262 hashdist= [KNL,NUMA] Large hashes allocated during boot
1263 are distributed across NUMA nodes. Defaults on
16290246 1264 for 64-bit NUMA, off otherwise.
a9913044 1265 Format: 0 | 1 (for off | on)
1da177e4
LT
1266
1267 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1268
1269 hd= [EIDE] (E)IDE hard drive subsystem geometry
1270 Format: <cyl>,<head>,<sect>
1271
ea8c071c
HY
1272 hest_disable [ACPI]
1273 Disable Hardware Error Source Table (HEST) support;
1274 corresponding firmware-first mode error processing
1275 logic will be disabled.
1276
1da177e4
LT
1277 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1278 size of <nn>. This works even on boxes that have no
1279 highmem otherwise. This also works to reduce highmem
1280 size on bigger boxes.
1281
54cdfdb4
TG
1282 highres= [KNL] Enable/disable high resolution timer mode.
1283 Valid parameters: "on", "off"
1284 Default: "on"
1285
1da177e4
LT
1286 hisax= [HW,ISDN]
1287 See Documentation/isdn/README.HiSax.
1288
0cb55ad2
RD
1289 hlt [BUGS=ARM,SH]
1290
1291 hpet= [X86-32,HPET] option to control HPET usage
1292 Format: { enable (default) | disable | force |
1293 verbose }
1294 disable: disable HPET and use PIT instead
1295 force: allow force enabled of undocumented chips (ICH4,
1296 VIA, nVidia)
1297 verbose: show contents of HPET registers during setup
1298
3d035f58
PB
1299 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1300 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1301
b4718e62
AK
1302 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1303 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
0d9ea754
JT
1304 On x86-64 and powerpc, this option can be specified
1305 multiple times interleaved with hugepages= to reserve
1306 huge pages of different sizes. Valid pages sizes on
1307 x86-64 are 2M (when the CPU supports "pse") and 1G
27ec26ec 1308 (when the CPU supports the "pdpe1gb" cpuinfo flag).
6902aa84 1309
555d61d6
HB
1310 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1311 terminal devices. Valid values: 0..8
431429ff
HB
1312 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1313 If specified, z/VM IUCV HVC accepts connections
1314 from listed z/VM user IDs only.
cef7125d 1315
fdabf525
JH
1316 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1317 hardware thread id mappings.
1318 Format: <cpu>:<hwthread>
1319
7bf69395
FDN
1320 keep_bootcon [KNL]
1321 Do not unregister boot console at start. This is only
1322 useful for debugging when something happens in the window
1323 between unregistering the boot console and initializing
1324 the real console.
1325
3a853fb9 1326 i2c_bus= [HW] Override the default board specific I2C bus speed
7954763b
JN
1327 or register an additional I2C bus that is not
1328 registered from board initialization code.
3a853fb9
JN
1329 Format:
1330 <bus_id>,<clkrate>
1331
36d95739 1332 i8042.debug [HW] Toggle i8042 debug mode
1da177e4 1333 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
1334 i8042.dumbkbd [HW] Pretend that controller can only read data from
1335 keyboard and cannot control its state
1da177e4
LT
1336 (Don't attempt to blink the leds)
1337 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 1338 i8042.nokbd [HW] Don't check/create keyboard port
75d08c78
JK
1339 i8042.noloop [HW] Disable the AUX Loopback command while probing
1340 for the AUX port
1da177e4 1341 i8042.nomux [HW] Don't check presence of an active multiplexing
e55a3366 1342 controller
1da177e4
LT
1343 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1344 controllers
24775d65 1345 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1da177e4
LT
1346 i8042.reset [HW] Reset the controller during init and cleanup
1347 i8042.unlock [HW] Unlock (ignore) the keylock
148e9a71 1348 i8042.kbdreset [HW] Reset device connected to KBD port
1da177e4
LT
1349
1350 i810= [HW,DRM]
1351
e70c9d5e
DT
1352 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1353 indicates that the driver is running on unsupported
1354 hardware.
1da177e4
LT
1355 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1356 does not match list of supported models.
1357 i8k.power_status
1358 [HW] Report power status in /proc/i8k
1359 (disabled by default)
1360 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1361 capability is set.
1362
4dca20ef 1363 i915.invert_brightness=
7bd90909
CE
1364 [DRM] Invert the sense of the variable that is used to
1365 set the brightness of the panel backlight. Normally a
4dca20ef
CE
1366 brightness value of 0 indicates backlight switched off,
1367 and the maximum of the brightness value sets the backlight
1368 to maximum brightness. If this parameter is set to 0
1369 (default) and the machine requires it, or this parameter
1370 is set to 1, a brightness value of 0 sets the backlight
1371 to maximum brightness, and the maximum of the brightness
1372 value switches the backlight off.
1373 -1 -- never invert brightness
1374 0 -- machine default
1375 1 -- force brightness inversion
7bd90909 1376
1da177e4
LT
1377 icn= [HW,ISDN]
1378 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1379
0af80c04
DF
1380 ide-core.nodma= [HW] (E)IDE subsystem
1381 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
075affcb
BZ
1382 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1383 .cdrom .chs .ignore_cable are additional options
1c10e938 1384 See Documentation/ide/ide.txt.
1da177e4 1385
0f8b7f5d
MR
1386 ide-generic.probe-mask= [HW] (E)IDE subsystem
1387 Format: <int>
1388 Probe mask for legacy ISA IDE ports. Depending on
1389 platform up to 6 ports are supported, enabled by
1390 setting corresponding bits in the mask to 1. The
1391 default value is 0x0, which has a special meaning.
1392 On systems that have PCI, it triggers scanning the
1393 PCI bus for the first and the second port, which
1394 are then probed. On systems without PCI the value
1395 of 0x0 enables probing the two first ports as if it
1396 was 0x3.
1397
0cb55ad2
RD
1398 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1399 Claim all unknown PCI IDE storage controllers.
1400
f039b754 1401 idle= [X86]
69fb3676 1402 Format: idle=poll, idle=halt, idle=nomwait
ada9cfdd
RD
1403 Poll forces a polling idle loop that can slightly
1404 improve the performance of waking up a idle CPU, but
1405 will use a lot of power and make the system run hot.
1406 Not recommended.
ada9cfdd 1407 idle=halt: Halt is forced to be used for CPU idle.
c1e3b377 1408 In such case C2/C3 won't be used again.
ada9cfdd 1409 idle=nomwait: Disable mwait for CPU C-states
a9913044 1410
79290822
IM
1411 ignore_loglevel [KNL]
1412 Ignore loglevel setting - this will print /all/
1413 kernel messages to the console. Useful for debugging.
0eca6b7c
YZ
1414 We also add it as printk module parameter, so users
1415 could change it dynamically, usually by
1416 /sys/module/printk/parameters/ignore_loglevel.
79290822 1417
1da177e4
LT
1418 ihash_entries= [KNL]
1419 Set number of hash buckets for inode cache.
1420
2fe5d6de 1421 ima_appraise= [IMA] appraise integrity measurements
2faa6ef3 1422 Format: { "off" | "enforce" | "fix" | "log" }
2fe5d6de
MZ
1423 default: "enforce"
1424
07f6a794
MZ
1425 ima_appraise_tcb [IMA]
1426 The builtin appraise policy appraises all files
1427 owned by uid=0.
1428
3323eec9 1429 ima_hash= [IMA]
e7a2ad7e
MZ
1430 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1431 | sha512 | ... }
3323eec9
MZ
1432 default: "sha1"
1433
e7a2ad7e
MZ
1434 The list of supported hash algorithms is defined
1435 in crypto/hash_info.h.
1436
24fd03c8
MZ
1437 ima_policy= [IMA]
1438 The builtin measurement policy to load during IMA
1439 setup. Specyfing "tcb" as the value, measures all
1440 programs exec'd, files mmap'd for exec, and all files
1441 opened with the read mode bit set by either the
1442 effective uid (euid=0) or uid=0.
1443 Format: "tcb"
1444
1445 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
5789ba3b
EP
1446 Load a policy which meets the needs of the Trusted
1447 Computing Base. This means IMA will measure all
1448 programs exec'd, files mmap'd for exec, and all files
1449 opened for read by uid=0.
1450
9b9d4ce5
RS
1451 ima_template= [IMA]
1452 Select one of defined IMA measurements template formats.
8265a2f8 1453 Formats: { "ima" | "ima-ng" | "ima-sig" }
9b9d4ce5
RS
1454 Default: "ima-ng"
1455
c2426d2a
RS
1456 ima_template_fmt=
1457 [IMA] Define a custom template format.
1458 Format: { "field1|...|fieldN" }
1459
3bcced39
DK
1460 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1461 Format: <min_file_size>
1462 Set the minimal file size for using asynchronous hash.
1463 If left unspecified, ahash usage is disabled.
1464
1465 ahash performance varies for different data sizes on
1466 different crypto accelerators. This option can be used
1467 to achieve the best performance for a particular HW.
1468
6edf7a89
DK
1469 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1470 Format: <bufsize>
1471 Set hashing buffer size. Default: 4k.
1472
1473 ahash performance varies for different chunk sizes on
1474 different crypto accelerators. This option can be used
1475 to achieve best performance for particular HW.
1476
1da177e4
LT
1477 init= [KNL]
1478 Format: <full_path>
1479 Run specified binary instead of /sbin/init as init
1480 process.
1481
1482 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1483 for working out where the kernel is dying during
1484 startup.
1485
7b0b73d7
PB
1486 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1487 initcall functions. Useful for debugging built-in
1488 modules and initcalls.
1489
1da177e4
LT
1490 initrd= [BOOT] Specify the location of the initial ramdisk
1491
1492 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1493 Format: <irq>
1494
6bb2ff84
FY
1495 int_pln_enable [x86] Enable power limit notification interrupt
1496
d726d8d7
MZ
1497 integrity_audit=[IMA]
1498 Format: { "0" | "1" }
1499 0 -- basic integrity auditing messages. (Default)
1500 1 -- additional integrity auditing messages.
1501
ba395927 1502 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
0cd5c3c8
KM
1503 on
1504 Enable intel iommu driver.
ba395927
KA
1505 off
1506 Disable intel iommu driver.
1507 igfx_off [Default Off]
1508 By default, gfx is mapped as normal device. If a gfx
1509 device has a dedicated DMAR unit, the DMAR unit is
1510 bypassed by not enabling DMAR with this option. In
1511 this case, gfx device will use physical address for
1512 DMA.
7d3b03ce
KA
1513 forcedac [x86_64]
1514 With this option iommu will not optimize to look
16290246 1515 for io virtual address below 32-bit forcing dual
7d3b03ce 1516 address cycle on pci bus for cards supporting greater
16290246
RD
1517 than 32-bit addressing. The default is to look
1518 for translation below 32-bit and if not available
7d3b03ce 1519 then look in the higher range.
5e0d2a6f 1520 strict [Default Off]
1521 With this option on every unmap_single operation will
1522 result in a hardware IOTLB flush operation as opposed
1523 to batching them for performance.
6dd9a7c7
YS
1524 sp_off [Default Off]
1525 By default, super page will be supported if Intel IOMMU
1526 has the capability. With this option, super page will
1527 not be supported.
c83b2f20
DW
1528 ecs_off [Default Off]
1529 By default, extended context tables will be supported if
1530 the hardware advertises that it has support both for the
1531 extended tables themselves, and also PASID support. With
1532 this option set, extended tables will not be used even
1533 on hardware which claims to support them.
2e92c7ad
MI
1534
1535 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1536 0 disables intel_idle and fall back on acpi_idle.
1537 1 to 6 specify maximum depth of C-state.
1538
6be26498
DB
1539 intel_pstate= [X86]
1540 disable
1541 Do not enable intel_pstate as the default
1542 scaling driver for the supported processors
aa4ea34d
EZ
1543 force
1544 Enable intel_pstate on systems that prohibit it by default
1545 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1546 instead of acpi-cpufreq may disable platform features, such
1547 as thermal controls and power capping, that rely on ACPI
1548 P-States information being indicated to OSPM and therefore
1549 should be used with caution. This option does not work with
1550 processors that aren't supported by the intel_pstate driver
1551 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
2f86dc4c
DB
1552 no_hwp
1553 Do not enable hardware P state control (HWP)
1554 if available.
d64c3b0b
KCA
1555 hwp_only
1556 Only load intel_pstate on systems which support
1557 hardware P state control (HWP) if available.
6be26498 1558
d1423d56 1559 intremap= [X86-64, Intel-IOMMU]
d1423d56
CW
1560 on enable Interrupt Remapping (default)
1561 off disable Interrupt Remapping
1562 nosid disable Source ID checking
41750d31
SS
1563 no_x2apic_optout
1564 BIOS x2APIC opt-out request will be ignored
d1423d56 1565
0cb55ad2
RD
1566 iomem= Disable strict checking of access to MMIO memory
1567 strict regions from userspace.
1568 relaxed
1569
1570 iommu= [x86]
1571 off
1572 force
1573 noforce
1574 biomerge
1575 panic
1576 nopanic
1577 merge
1578 nomerge
1579 forcesac
1580 soft
bcb71abe 1581 pt [x86, IA-64]
4e287840
TLSC
1582 nobypass [PPC/POWERNV]
1583 Disable IOMMU bypass, using IOMMU for PCI devices.
bcb71abe 1584
0cb55ad2
RD
1585
1586 io7= [HW] IO7 for Marvel based alpha systems
1587 See comment before marvel_specify_io7 in
1588 arch/alpha/kernel/core_marvel.c.
1589
6cececfc 1590 io_delay= [X86] I/O delay method
6e7c4025
IM
1591 0x80
1592 Standard port 0x80 based delay
1593 0xed
1594 Alternate port 0xed based delay (needed on some systems)
b02aae9c 1595 udelay
6e7c4025
IM
1596 Simple two microseconds delay
1597 none
1598 No delay
b02aae9c 1599
1da177e4 1600 ip= [IP_PNP]
dc7a0816 1601 See Documentation/filesystems/nfs/nfsroot.txt.
1da177e4 1602
200803df
AC
1603 irqfixup [HW]
1604 When an interrupt is not handled search all handlers
1605 for it. Intended to get systems with badly broken
1606 firmware running.
1607
1608 irqpoll [HW]
1609 When an interrupt is not handled search all handlers
1610 for it. Also check all handlers each timer
1611 interrupt. Intended to get systems with badly broken
1612 firmware running.
1613
1da177e4 1614 isapnp= [ISAPNP]
a9913044 1615 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
1616
1617 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
1618 Format:
1619 <cpu number>,...,<cpu number>
1620 or
b225d44e
LZ
1621 <cpu number>-<cpu number>
1622 (must be a positive range in ascending order)
22f2e280
DF
1623 or a mixture
1624 <cpu number>,...,<cpu number>-<cpu number>
b225d44e 1625
1da177e4
LT
1626 This option can be used to specify one or more CPUs
1627 to isolate from the general SMP balancing and scheduling
b225d44e
LZ
1628 algorithms. You can move a process onto or off an
1629 "isolated" CPU via the CPU affinity syscalls or cpuset.
1da177e4
LT
1630 <cpu number> begins at 0 and the maximum value is
1631 "number of CPUs in system - 1".
1632
1633 This option is the preferred way to isolate CPUs. The
a9913044
RD
1634 alternative -- manually setting the CPU mask of all
1635 tasks in the system -- can cause problems and
1636 suboptimal load balancer performance.
1da177e4 1637
a9913044 1638 iucv= [HW,NET]
1da177e4 1639
7d8bfa26
JR
1640 ivrs_ioapic [HW,X86_64]
1641 Provide an override to the IOAPIC-ID<->DEVICE-ID
1642 mapping provided in the IVRS ACPI table. For
1643 example, to map IOAPIC-ID decimal 10 to
1644 PCI device 00:14.0 write the parameter as:
1645 ivrs_ioapic[10]=00:14.0
1646
1647 ivrs_hpet [HW,X86_64]
1648 Provide an override to the HPET-ID<->DEVICE-ID
1649 mapping provided in the IVRS ACPI table. For
1650 example, to map HPET-ID decimal 0 to
1651 PCI device 00:14.0 write the parameter as:
1652 ivrs_hpet[0]=00:14.0
1653
1da177e4
LT
1654 js= [HW,JOY] Analog joystick
1655 See Documentation/input/joystick.txt.
1656
24f2e027
KC
1657 kaslr/nokaslr [X86]
1658 Enable/disable kernel and module base offset ASLR
1659 (Address Space Layout Randomization) if built into
1660 the kernel. When CONFIG_HIBERNATION is selected,
1661 kASLR is disabled by default. When kASLR is enabled,
1662 hibernation will be disabled.
1663
0cb55ad2
RD
1664 keepinitrd [HW,ARM]
1665
6cececfc 1666 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
ed7ed365
MG
1667 specifies the amount of memory usable by the kernel
1668 for non-movable allocations. The requested amount is
1669 spread evenly throughout all nodes in the system. The
1670 remaining memory in each node is used for Movable
1671 pages. In the event, a node is too small to have both
1672 kernelcore and Movable pages, kernelcore pages will
1673 take priority and other nodes will have a larger number
675217fd 1674 of Movable pages. The Movable zone is used for the
ed7ed365
MG
1675 allocation of pages that may be reclaimed or moved
1676 by the page migration subsystem. This means that
1677 HugeTLB pages may not be allocated from this zone.
1678 Note that allocations like PTEs-from-HighMem still
1679 use the HighMem zone if it exists, and the Normal
1680 zone if it does not.
1681
4fe1da4e
JW
1682 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1683 Format: <Controller#>[,poll interval]
1684 The controller # is the number of the ehci usb debug
1685 port as it is probed via PCI. The poll interval is
1686 optional and is the number seconds in between
1687 each poll cycle to the debug port in case you need
1688 the functionality for interrupting the kernel with
1689 gdb or control-c on the dbgp connection. When
1690 not using this parameter you use sysrq-g to break into
1691 the kernel debugger.
1692
84c08fd6 1693 kgdboc= [KGDB,HW] kgdb over consoles.
ada64e4c
JW
1694 Requires a tty driver that supports console polling,
1695 or a supported polling keyboard driver (non-usb).
65b5ac14
JW
1696 Serial only format: <serial_device>[,baud]
1697 keyboard only format: kbd
1698 keyboard and serial format: kbd,<serial_device>[,baud]
1699 Optional Kernel mode setting:
1700 kms, kbd format: kms,kbd
1701 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
6cdf6e06 1702
84c08fd6
JW
1703 kgdbwait [KGDB] Stop kernel execution and enter the
1704 kernel debugger at the earliest opportunity.
1705
9bed90c6
FF
1706 kmac= [MIPS] korina ethernet MAC address.
1707 Configure the RouterBoard 532 series on-chip
1708 Ethernet adapter MAC address.
1709
04f70336
CM
1710 kmemleak= [KNL] Boot-time kmemleak enable/disable
1711 Valid arguments: on, off
1712 Default: on
47aeeddc
MI
1713 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1714 the default is off.
04f70336 1715
c3ac14b2
XQ
1716 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1717 Valid arguments: 0, 1, 2
1718 kmemcheck=0 (disabled)
1719 kmemcheck=1 (enabled)
1720 kmemcheck=2 (one-shot mode)
1721 Default: 2 (one-shot mode)
1722
6cececfc 1723 kstack=N [X86] Print N words from the kernel stack
0cb55ad2
RD
1724 in oops dumps.
1725
fef07aae
AP
1726 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1727 Default is 0 (don't ignore, but inject #GP)
1728
a182d873
XG
1729 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1730 KVM MMU at runtime.
fef07aae
AP
1731 Default is 0 (off)
1732
fef07aae 1733 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
8475f94a 1734 Default is 1 (enabled)
fef07aae
AP
1735
1736 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1737 for all guests.
16290246 1738 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
fef07aae 1739
fef07aae
AP
1740 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1741 (virtualized MMU) support on capable Intel chips.
1742 Default is 1 (enabled)
1743
1744 kvm-intel.emulate_invalid_guest_state=
1745 [KVM,Intel] Enable emulation of invalid guest states
1746 Default is 0 (disabled)
1747
1748 kvm-intel.flexpriority=
1749 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1750 Default is 1 (enabled)
1751
e1a72ae2
SL
1752 kvm-intel.nested=
1753 [KVM,Intel] Enable VMX nesting (nVMX).
1754 Default is 0 (disabled)
1755
fef07aae
AP
1756 kvm-intel.unrestricted_guest=
1757 [KVM,Intel] Disable unrestricted guest feature
1758 (virtualized real and unpaged mode) on capable
1759 Intel chips. Default is 1 (enabled)
1760
1761 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1762 feature (tagged TLBs) on capable Intel chips.
1763 Default is 1 (enabled)
1764
1da177e4
LT
1765 l2cr= [PPC]
1766
a78bfbfc
RB
1767 l3cr= [PPC]
1768
cd4f0ef7 1769 lapic [X86-32,APIC] Enable the local APIC even if BIOS
a9913044 1770 disabled it.
1da177e4 1771
279f1461
SS
1772 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1773 value for LAPIC timer one-shot implementation. Default
1774 back to the programmable timer unit in the LAPIC.
1775
6cececfc 1776 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
ada9cfdd 1777 in C2 power state.
e585bef8 1778
fcb71f6f
FC
1779 libata.dma= [LIBATA] DMA control
1780 libata.dma=0 Disable all PATA and SATA DMA
1781 libata.dma=1 PATA and SATA Disk DMA only
1782 libata.dma=2 ATAPI (CDROM) DMA only
16290246 1783 libata.dma=4 Compact Flash DMA only
fcb71f6f
FC
1784 Combinations also work, so libata.dma=3 enables DMA
1785 for disks and CDROMs, but not CFs.
16290246 1786
20308871
MP
1787 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1788 libata.ignore_hpa=0 keep BIOS limits (default)
1789 libata.ignore_hpa=1 ignore limits, using full disk
fcb71f6f 1790
78e70c23
DJ
1791 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1792 when set.
1793 Format: <int>
1794
33267325
TH
1795 libata.force= [LIBATA] Force configurations. The format is comma
1796 separated list of "[ID:]VAL" where ID is
4c44f309 1797 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
33267325
TH
1798 matching port, link or device. Basically, it matches
1799 the ATA ID string printed on console by libata. If
1800 the whole ID part is omitted, the last PORT and DEVICE
1801 values are used. If ID hasn't been specified yet, the
1802 configuration applies to all ports, links and devices.
1803
1804 If only DEVICE is omitted, the parameter applies to
1805 the port and all links and devices behind it. DEVICE
1806 number of 0 either selects the first device or the
1807 first fan-out link behind PMP device. It does not
1808 select the host link. DEVICE number of 15 selects the
1809 host link and device attached to it.
1810
1811 The VAL specifies the configuration to force. As long
1812 as there's no ambiguity shortcut notation is allowed.
1813 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1814 The following configurations can be forced.
1815
1816 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1817 Any ID with matching PORT is used.
1818
1819 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1820
1821 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1822 udma[/][16,25,33,44,66,100,133] notation is also
1823 allowed.
1824
1825 * [no]ncq: Turn on or off NCQ.
1826
d7b16e4f
MP
1827 * [no]ncqtrim: Turn off queued DSM TRIM.
1828
05944bdf
TH
1829 * nohrst, nosrst, norst: suppress hard, soft
1830 and both resets.
1831
ca6d43b0
DW
1832 * rstonce: only attempt one reset during
1833 hot-unplug link recovery
1834
43c9c591
TH
1835 * dump_id: dump IDENTIFY data.
1836
966fbe19
VP
1837 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1838
b8bd6dc3
RJ
1839 * disable: Disable this device.
1840
33267325
TH
1841 If there are multiple matching configurations changing
1842 the same attribute, the last one is used.
1843
95f72d1e 1844 memblock=debug [KNL] Enable memblock debug messages.
7c4be253 1845
1da177e4 1846 load_ramdisk= [RAM] List of ramdisks to load from floppy
31c00fc1 1847 See Documentation/blockdev/ramdisk.txt.
1da177e4 1848
a6b25b67
RD
1849 lockd.nlm_grace_period=P [NFS] Assign grace period.
1850 Format: <integer>
1da177e4 1851
a6b25b67
RD
1852 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1853 Format: <integer>
1854
1855 lockd.nlm_timeout=T [NFS] Assign timeout value.
1856 Format: <integer>
1857
1858 lockd.nlm_udpport=M [NFS] Assign UDP port.
1859 Format: <integer>
1da177e4 1860
ec4518aa
PM
1861 locktorture.nreaders_stress= [KNL]
1862 Set the number of locking read-acquisition kthreads.
1863 Defaults to being automatically set based on the
1864 number of online CPUs.
1865
1866 locktorture.nwriters_stress= [KNL]
1867 Set the number of locking write-acquisition kthreads.
1868
1869 locktorture.onoff_holdoff= [KNL]
1870 Set time (s) after boot for CPU-hotplug testing.
1871
1872 locktorture.onoff_interval= [KNL]
1873 Set time (s) between CPU-hotplug operations, or
1874 zero to disable CPU-hotplug testing.
1875
1876 locktorture.shuffle_interval= [KNL]
1877 Set task-shuffle interval (jiffies). Shuffling
1878 tasks allows some CPUs to go into dyntick-idle
1879 mode during the locktorture test.
1880
1881 locktorture.shutdown_secs= [KNL]
1882 Set time (s) after boot system shutdown. This
1883 is useful for hands-off automated testing.
1884
1885 locktorture.stat_interval= [KNL]
1886 Time (s) between statistics printk()s.
1887
1888 locktorture.stutter= [KNL]
1889 Time (s) to stutter testing, for example,
1890 specifying five seconds causes the test to run for
1891 five seconds, wait for five seconds, and so on.
1892 This tests the locking primitive's ability to
1893 transition abruptly to and from idle.
1894
1895 locktorture.torture_runnable= [BOOT]
1896 Start locktorture running at boot time.
1897
1898 locktorture.torture_type= [KNL]
1899 Specify the locking implementation to test.
1900
1901 locktorture.verbose= [KNL]
1902 Enable additional printk() statements.
1903
1da177e4
LT
1904 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1905 Format: <irq>
1906
1907 loglevel= All Kernel Messages with a loglevel smaller than the
1908 console loglevel will be printed to the console. It can
1909 also be changed with klogd or other programs. The
1910 loglevels are defined as follows:
1911
1912 0 (KERN_EMERG) system is unusable
1913 1 (KERN_ALERT) action must be taken immediately
1914 2 (KERN_CRIT) critical conditions
1915 3 (KERN_ERR) error conditions
1916 4 (KERN_WARNING) warning conditions
1917 5 (KERN_NOTICE) normal but significant condition
1918 6 (KERN_INFO) informational
1919 7 (KERN_DEBUG) debug-level messages
1920
c756d08a 1921 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
23b2899f
LR
1922 in bytes. n must be a power of two and greater
1923 than the minimal size. The minimal size is defined
1924 by LOG_BUF_SHIFT kernel config parameter. There is
1925 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1926 that allows to increase the default size depending on
1927 the number of CPUs. See init/Kconfig for more details.
1da177e4 1928
accaa24c
RD
1929 logo.nologo [FB] Disables display of the built-in Linux logo.
1930 This may be used to provide more screen space for
1931 kernel log messages and is useful when debugging
1932 kernel boot problems.
1933
1da177e4
LT
1934 lp=0 [LP] Specify parallel ports to use, e.g,
1935 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1936 lp=reset first parallel port). 'lp=0' disables the
1937 lp=auto printer driver. 'lp=reset' (which can be
1938 specified in addition to the ports) causes
1939 attached printers to be reset. Using
1940 lp=port1,port2,... specifies the parallel ports
1941 to associate lp devices with, starting with
1942 lp0. A port specification may be 'none' to skip
1943 that lp device, or a parport name such as
1944 'parport0'. Specifying 'lp=auto' instead of a
1945 port specification list means that device IDs
1946 from each port should be examined, to see if
1947 an IEEE 1284-compliant printer is attached; if
1948 so, the driver will manage that printer.
1949 See also header of drivers/char/lp.c.
1950
1951 lpj=n [KNL]
1952 Sets loops_per_jiffy to given constant, thus avoiding
1953 time-consuming boot-time autodetection (up to 250 ms per
1954 CPU). 0 enables autodetection (default). To determine
1955 the correct value for your kernel, boot with normal
1956 autodetection and see what value is printed. Note that
1957 on SMP systems the preset will be applied to all CPUs,
1958 which is likely to cause problems if your CPUs need
1959 significantly divergent settings. An incorrect value
1960 will cause delays in the kernel to be wrong, leading to
1961 unpredictable I/O errors and other breakage. Although
1962 unlikely, in the extreme case this might damage your
1963 hardware.
1964
1965 ltpc= [NET]
1966 Format: <io>,<irq>,<dma>
1967
16290246 1968 machvec= [IA-64] Force the use of a particular machine-vector
a9913044
RD
1969 (machvec) in a generic kernel.
1970 Example: machvec=hpzx1_swiotlb
1da177e4 1971
3209e70e
WZ
1972 machtype= [Loongson] Share the same kernel image file between different
1973 yeeloong laptop.
1974 Example: machtype=lemote-yeeloong-2f-7inch
1975
0cb55ad2
RD
1976 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1977 than or equal to this physical address is ignored.
1da177e4
LT
1978
1979 maxcpus= [SMP] Maximum number of processors that an SMP kernel
61ec7567
LB
1980 should make use of. maxcpus=n : n >= 0 limits the
1981 kernel to using 'n' processors. n=0 is a special case,
1982 it is equivalent to "nosmp", which also disables
1983 the IO APIC.
1da177e4 1984
d134b00b
KS
1985 max_loop= [LOOP] The number of loop block devices that get
1986 (loop.max_loop) unconditionally pre-created at init time. The default
1987 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1988 of statically allocating a predefined number, loop
1989 devices can be requested on-demand with the
1990 /dev/loop-control interface.
2b2c3750 1991
cd4f0ef7 1992 mce [X86-32] Machine Check Exception
1da177e4 1993
71cced6e 1994 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
909dd324 1995
1da177e4
LT
1996 md= [HW] RAID subsystems devices and level
1997 See Documentation/md.txt.
a9913044 1998
1da177e4
LT
1999 mdacon= [MDA]
2000 Format: <first>,<last>
2001 Specifies range of consoles to be captured by the MDA.
a9913044 2002
1da177e4
LT
2003 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2004 Amount of memory to be used when the kernel is not able
2005 to see the whole system memory or for test.
fbb97d87
WC
2006 [X86] Work as limiting max address. Use together
2007 with memmap= to avoid physical address space collisions.
2008 Without memmap= PCI devices could be placed at addresses
2009 belonging to unused RAM.
1da177e4 2010
cd4f0ef7 2011 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1da177e4
LT
2012 memory.
2013
6902aa84
PM
2014 memchunk=nn[KMG]
2015 [KNL,SH] Allow user to override the default size for
2016 per-device physically contiguous DMA buffers.
2017
6cececfc 2018 memmap=exactmap [KNL,X86] Enable setting of an exact
1da177e4
LT
2019 E820 memory map, as specified by the user.
2020 Such memmap=exactmap lines can be constructed based on
2021 BIOS output or other requirements. See the memmap=nn@ss
2022 option description.
2023
2024 memmap=nn[KMG]@ss[KMG]
277cba1d
RD
2025 [KNL] Force usage of a specific region of memory.
2026 Region of memory to be used is from ss to ss+nn.
1da177e4
LT
2027
2028 memmap=nn[KMG]#ss[KMG]
2029 [KNL,ACPI] Mark specific memory as ACPI data.
277cba1d 2030 Region of memory to be marked is from ss to ss+nn.
1da177e4
LT
2031
2032 memmap=nn[KMG]$ss[KMG]
2033 [KNL,ACPI] Mark specific memory as reserved.
277cba1d 2034 Region of memory to be reserved is from ss to ss+nn.
1312848e
PM
2035 Example: Exclude memory from 0x18690000-0x1869ffff
2036 memmap=64K$0x18690000
2037 or
2038 memmap=0x10000$0x18690000
1da177e4 2039
ec776ef6
CH
2040 memmap=nn[KMG]!ss[KMG]
2041 [KNL,X86] Mark specific memory as protected.
2042 Region of memory to be used, from ss to ss+nn.
2043 The memory region may be marked as e820 type 12 (0xc)
2044 and is NVDIMM or ADR memory.
2045
9f077871
JF
2046 memory_corruption_check=0/1 [X86]
2047 Some BIOSes seem to corrupt the first 64k of
2048 memory when doing things like suspend/resume.
2049 Setting this option will scan the memory
2050 looking for corruption. Enabling this will
2051 both detect corruption and prevent the kernel
2052 from using the memory being corrupted.
2053 However, its intended as a diagnostic tool; if
2054 repeatable BIOS-originated corruption always
2055 affects the same memory, you can use memmap=
2056 to prevent the kernel from using that memory.
2057
2058 memory_corruption_check_size=size [X86]
2059 By default it checks for corruption in the low
2060 64k, making this memory unavailable for normal
2061 use. Use this parameter to scan for
2062 corruption in more or less memory.
2063
2064 memory_corruption_check_period=seconds [X86]
2065 By default it checks for corruption every 60
2066 seconds. Use this parameter to check at some
2067 other rate. 0 disables periodic checking.
2068
e4b0db72 2069 memtest= [KNL,X86,ARM] Enable memtest
c64df707 2070 Format: <integer>
c64df707 2071 default : 0 <disable>
9e5f6cf5
AH
2072 Specifies the number of memtest passes to be
2073 performed. Each pass selects another test
2074 pattern from a given set of patterns. Memtest
2075 fills the memory with this pattern, validates
2076 memory contents and reserves bad memory
2077 regions that are detected.
c64df707 2078
1da177e4
LT
2079 meye.*= [HW] Set MotionEye Camera parameters
2080 See Documentation/video4linux/meye.txt.
2081
8f36881b
AS
2082 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2083 Multi-Function General Purpose Timers on AMD Geode
2084 platforms.
2085
e6c4dc6c
WT
2086 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2087 the BIOS has incorrectly applied a workaround. TinyBIOS
2088 version 0.98 is known to be affected, 0.99 fixes the
2089 problem by letting the user disable the workaround.
2090
1da177e4
LT
2091 mga= [HW,DRM]
2092
1c207f95
RD
2093 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2094 physical address is ignored.
2095
39f45d7b
MP
2096 mini2440= [ARM,HW,KNL]
2097 Format:[0..2][b][c][t]
2098 Default: "0tb"
2099 MINI2440 configuration specification:
2100 0 - The attached screen is the 3.5" TFT
2101 1 - The attached screen is the 7" TFT
2102 2 - The VGA Shield is attached (1024x768)
2103 Leaving out the screen size parameter will not load
2104 the TFT driver, and the framebuffer will be left
2105 unconfigured.
2106 b - Enable backlight. The TFT backlight pin will be
2107 linked to the kernel VESA blanking code and a GPIO
2108 LED. This parameter is not necessary when using the
2109 VGA shield.
2110 c - Enable the s3c camera interface.
2111 t - Reserved for enabling touchscreen support. The
2112 touchscreen support is not enabled in the mainstream
2113 kernel as of 2.6.30, a preliminary port can be found
2114 in the "bleeding edge" mini2440 support kernel at
2115 http://repo.or.cz/w/linux-2.6/mini2440.git
2116
6b74ab97
MG
2117 mminit_loglevel=
2118 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2119 parameter allows control of the logging verbosity for
2120 the additional memory initialisation checks. A value
2121 of 0 disables mminit logging and a level of 4 will
2122 log everything. Information is printed at KERN_DEBUG
2123 so loglevel=8 may also need to be specified.
2124
106a4ee2
RR
2125 module.sig_enforce
2126 [KNL] When CONFIG_MODULE_SIG is set, this means that
2127 modules without (valid) signatures will fail to load.
2a039be7 2128 Note that if CONFIG_MODULE_SIG_FORCE is set, that
106a4ee2
RR
2129 is always true, so this option does nothing.
2130
1da177e4
LT
2131 mousedev.tap_time=
2132 [MOUSE] Maximum time between finger touching and
2133 leaving touchpad surface for touch to be considered
2134 a tap and be reported as a left button click (for
2135 touchpads working in absolute mode only).
2136 Format: <msecs>
2137 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2138 reporting absolute coordinates, such as tablets
2139 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2140 reporting absolute coordinates, such as tablets
2141
6cececfc 2142 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
0cb55ad2
RD
2143 is similar to kernelcore except it specifies the
2144 amount of memory used for migratable allocations.
2145 If both kernelcore and movablecore is specified,
2146 then kernelcore will be at *least* the specified
2147 value but may be more. If movablecore on its own
2148 is specified, the administrator must be careful
2149 that the amount of memory usable for all allocations
2150 is not too small.
2151
c5320926
TC
2152 movable_node [KNL,X86] Boot-time switch to enable the effects
2153 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2154
1da177e4
LT
2155 MTD_Partition= [MTD]
2156 Format: <name>,<region-number>,<size>,<offset>
2157
a9913044
RD
2158 MTD_Region= [MTD] Format:
2159 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
2160
2161 mtdparts= [MTD]
c8facbb6 2162 See drivers/mtd/cmdlinepart.c.
1da177e4 2163
4e89a2d8
WS
2164 multitce=off [PPC] This parameter disables the use of the pSeries
2165 firmware feature for updating multiple TCE entries
2166 at a time.
2167
5988af23
RH
2168 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2169
2170 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2171
2172 boundary - index of last SLC block on Flex-OneNAND.
2173 The remaining blocks are configured as MLC blocks.
2174 lock - Configure if Flex-OneNAND boundary should be locked.
2175 Once locked, the boundary cannot be changed.
2176 1 indicates lock status, 0 indicates unlock status.
2177
9db829f4
BD
2178 mtdset= [ARM]
2179 ARM/S3C2412 JIVE boot control
2180
2181 See arch/arm/mach-s3c2412/mach-jive.c
2182
1da177e4 2183 mtouchusb.raw_coordinates=
a9913044
RD
2184 [HW] Make the MicroTouch USB driver use raw coordinates
2185 ('y', default) or cooked coordinates ('n')
1da177e4 2186
0cb55ad2 2187 mtrr_chunk_size=nn[KMG] [X86]
19f59460 2188 used for mtrr cleanup. It is largest continuous chunk
0cb55ad2
RD
2189 that could hold holes aka. UC entries.
2190
2191 mtrr_gran_size=nn[KMG] [X86]
2192 Used for mtrr cleanup. It is granularity of mtrr block.
2193 Default is 1.
2194 Large value could prevent small alignment from
2195 using up MTRRs.
2196
2197 mtrr_spare_reg_nr=n [X86]
2198 Format: <integer>
2199 Range: 0,7 : spare reg number
2200 Default : 1
2201 Used for mtrr cleanup. It is spare mtrr entries number.
2202 Set to 2 or more if your graphical card needs more.
2203
1da177e4
LT
2204 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2205
1da177e4
LT
2206 netdev= [NET] Network devices parameters
2207 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2208 Note that mem_start is often overloaded to mean
2209 something different and driver-specific.
a9913044
RD
2210 This usage is only documented in each driver source
2211 file if at all.
2212
58401572
KPO
2213 nf_conntrack.acct=
2214 [NETFILTER] Enable connection tracking flow accounting
2215 0 to disable accounting
2216 1 to enable accounting
d70a011d 2217 Default value is 0.
58401572 2218
306a0753 2219 nfsaddrs= [NFS] Deprecated. Use ip= instead.
dc7a0816 2220 See Documentation/filesystems/nfs/nfsroot.txt.
1da177e4
LT
2221
2222 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
dc7a0816 2223 See Documentation/filesystems/nfs/nfsroot.txt.
1da177e4 2224
306a0753
CL
2225 nfsrootdebug [NFS] enable nfsroot debugging messages.
2226 See Documentation/filesystems/nfs/nfsroot.txt.
2227
a72b4422
TM
2228 nfs.callback_tcpport=
2229 [NFS] set the TCP port on which the NFSv4 callback
2230 channel should listen.
2231
e571cbf1
TM
2232 nfs.cache_getent=
2233 [NFS] sets the pathname to the program which is used
2234 to update the NFS client cache entries.
2235
2236 nfs.cache_getent_timeout=
2237 [NFS] sets the timeout after which an attempt to
2238 update a cache entry is deemed to have failed.
2239
58df095b
TM
2240 nfs.idmap_cache_timeout=
2241 [NFS] set the maximum lifetime for idmapper cache
2242 entries.
2243
f43bf0be
TM
2244 nfs.enable_ino64=
2245 [NFS] enable 64-bit inode numbers.
2246 If zero, the NFS client will fake up a 32-bit inode
2247 number for the readdir() and stat() syscalls instead
2248 of returning the full 64-bit number.
2249 The default is to return 64-bit inode numbers.
2250
ef159e91
TM
2251 nfs.max_session_slots=
2252 [NFSv4.1] Sets the maximum number of session slots
2253 the client will attempt to negotiate with the server.
2254 This limits the number of simultaneous RPC requests
2255 that the client can send to the NFSv4.1 server.
2256 Note that there is little point in setting this
2257 value higher than the max_tcp_slot_table_limit.
2258
b064eca2 2259 nfs.nfs4_disable_idmapping=
074b1d12
TM
2260 [NFSv4] When set to the default of '1', this option
2261 ensures that both the RPC level authentication
2262 scheme and the NFS level operations agree to use
2263 numeric uids/gids if the mount is using the
2264 'sec=sys' security flavour. In effect it is
2265 disabling idmapping, which can make migration from
2266 legacy NFSv2/v3 systems to NFSv4 easier.
2267 Servers that do not support this mode of operation
2268 will be autodetected by the client, and it will fall
2269 back to using the idmapper.
2270 To turn off this behaviour, set the value to '0'.
6f2ea7f2
CL
2271 nfs.nfs4_unique_id=
2272 [NFS4] Specify an additional fixed unique ident-
2273 ification string that NFSv4 clients can insert into
2274 their nfs_client_id4 string. This is typically a
2275 UUID that is generated at system install time.
b064eca2 2276
db8ac8ba
WAA
2277 nfs.send_implementation_id =
2278 [NFSv4.1] Send client implementation identification
2279 information in exchange_id requests.
2280 If zero, no implementation identification information
2281 will be sent.
2282 The default is to send the implementation identification
2283 information.
f6de7a39
TM
2284
2285 nfs.recover_lost_locks =
2286 [NFSv4] Attempt to recover locks that were lost due
2287 to a lease timeout on the server. Please note that
2288 doing this risks data corruption, since there are
2289 no guarantees that the file will remain unchanged
2290 after the locks are lost.
2291 If you want to enable the kernel legacy behaviour of
2292 attempting to recover these locks, then set this
2293 parameter to '1'.
2294 The default parameter value of '0' causes the kernel
2295 not to attempt recovery of lost locks.
db8ac8ba 2296
e9541ce8
BF
2297 nfsd.nfs4_disable_idmapping=
2298 [NFSv4] When set to the default of '1', the NFSv4
2299 server will return only numeric uids and gids to
2300 clients using auth_sys, and will accept numeric uids
2301 and gids from such clients. This is intended to ease
2302 migration from NFSv2/v3.
db8ac8ba 2303
18d98f6c
SB
2304 objlayoutdriver.osd_login_prog=
2305 [NFS] [OBJLAYOUT] sets the pathname to the program which
2306 is used to automatically discover and login into new
2307 osd-targets. Please see:
2308 Documentation/filesystems/pnfs.txt for more explanations
2309
1e1030dc 2310 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
e7ba176b
HS
2311 when a NMI is triggered.
2312 Format: [state][,regs][,debounce][,die]
2313
6cececfc 2314 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
fef2c9bc 2315 Format: [panic,][nopanic,][num]
195daf66 2316 Valid num: 0 or 1
5b9a0e14 2317 0 - turn nmi_watchdog off
195daf66 2318 1 - turn nmi_watchdog on
0cb55ad2 2319 When panic is specified, panic when an NMI watchdog
fef2c9bc
DZ
2320 timeout occurs (or 'nopanic' to override the opposite
2321 default).
0cb55ad2
RD
2322 This is useful when you use a panic=... timeout and
2323 need the box quickly up again.
1da177e4 2324
bff38771
AV
2325 netpoll.carrier_timeout=
2326 [NET] Specifies amount of time (in seconds) that
2327 netpoll should wait for a carrier. By default netpoll
2328 waits 4 seconds.
2329
cd4f0ef7 2330 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1da177e4
LT
2331 emulation library even if a 387 maths coprocessor
2332 is present.
2333
0cb55ad2
RD
2334 no_console_suspend
2335 [HW] Never suspend the console
2336 Disable suspending of consoles during suspend and
2337 hibernate operations. Once disabled, debugging
2338 messages can reach various consoles while the rest
2339 of the system is being put to sleep (ie, while
2340 debugging driver suspend/resume hooks). This may
2341 not work reliably with all consoles, but is known
2342 to work with serial and VGA consoles.
134620f7
YZ
2343 To facilitate more flexible debugging, we also add
2344 console_suspend, a printk module parameter to control
2345 it. Users could use console_suspend (usually
2346 /sys/module/printk/parameters/console_suspend) to
2347 turn on/off it dynamically.
0cb55ad2 2348
c1aee215
CL
2349 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2350 caches in the slab allocator. Saves per-node memory,
2351 but will impact performance.
3395ee05 2352
a9913044
RD
2353 noalign [KNL,ARM]
2354
1da177e4
LT
2355 noapic [SMP,APIC] Tells the kernel to not make use of any
2356 IOAPICs that may be present in the system.
2357
5091faa4
MG
2358 noautogroup Disable scheduler automatic task group creation.
2359
1da177e4
LT
2360 nobats [PPC] Do not use BATs for mapping kernel lowmem
2361 on "Classic" PPC cores.
2362
2363 nocache [ARM]
a9913044 2364
0cb55ad2
RD
2365 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2366
163ecdff
SN
2367 nodelayacct [KNL] Disable per-task delay accounting
2368
1da177e4
LT
2369 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2370
6902aa84
PM
2371 nodsp [SH] Disable hardware DSP at boot time.
2372
b2e0a54a 2373 noefi Disable EFI runtime services support.
8b2cb7a8 2374
1da177e4
LT
2375 noexec [IA-64]
2376
6cececfc 2377 noexec [X86]
f5a1b191 2378 On X86-32 available only on PAE configured kernels.
1da177e4 2379 noexec=on: enable non-executable mappings (default)
f5a1b191
JS
2380 noexec=off: disable non-executable mappings
2381
52b6179a
PA
2382 nosmap [X86]
2383 Disable SMAP (Supervisor Mode Access Prevention)
2384 even if it is supported by processor.
2385
de5397ad 2386 nosmep [X86]
52b6179a 2387 Disable SMEP (Supervisor Mode Execution Prevention)
de5397ad
FY
2388 even if it is supported by processor.
2389
f5a1b191
JS
2390 noexec32 [X86-64]
2391 This affects only 32-bit executables.
2392 noexec32=on: enable non-executable mappings (default)
2393 read doesn't imply executable mappings
2394 noexec32=off: disable non-executable mappings
2395 read implies executable mappings
1da177e4 2396
fab43ef4 2397 nofpu [MIPS,SH] Disable hardware FPU at boot time.
6902aa84 2398
cd4f0ef7 2399 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4f886511
CE
2400 register save and restore. The kernel will only save
2401 legacy floating-point registers on task switch.
1da177e4 2402
0ddab1d2
TK
2403 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2404
0c752a93
SS
2405 noxsave [BUGS=X86] Disables x86 extended register state save
2406 and restore using xsave. The kernel will fallback to
2407 enabling legacy floating-point and sse state.
2408
b6f42a4a
FY
2409 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2410 register states. The kernel will fall back to use
2411 xsave to save the states. By using this parameter,
2412 performance of saving the states is degraded because
2413 xsave doesn't support modified optimization while
2414 xsaveopt supports it on xsaveopt enabled systems.
2415
2416 noxsaves [X86] Disables xsaves and xrstors used in saving and
2417 restoring x86 extended register state in compacted
2418 form of xsave area. The kernel will fall back to use
2419 xsaveopt and xrstor to save and restore the states
2420 in standard form of xsave area. By using this
2421 parameter, xsave area per process might occupy more
2422 memory on xsaves enabled systems.
2423
01a24d2b
PZ
2424 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2425 wfi(ARM) instruction doesn't work correctly and not to
2426 use it. This is also useful when using JTAG debugger.
a9913044 2427
1f29fae2
SH
2428 no_file_caps Tells the kernel not to honor file capabilities. The
2429 only way then for a file to be executed with privilege
2430 is to be setuid root or executed by root.
2431
1da177e4
LT
2432 nohalt [IA-64] Tells the kernel not to use the power saving
2433 function PAL_HALT_LIGHT when idle. This increases
2434 power-consumption. On the positive side, it reduces
2435 interrupt wake-up latency, which may improve performance
2436 in certain environments such as networked servers or
2437 real-time systems.
2438
a6e15a39
KC
2439 nohibernate [HIBERNATION] Disable hibernation and resume.
2440
79bf2bb3
TG
2441 nohz= [KNL] Boottime enable/disable dynamic ticks
2442 Valid arguments: on, off
2443 Default: on
2444
c5bfece2
FW
2445 nohz_full= [KNL,BOOT]
2446 In kernels built with CONFIG_NO_HZ_FULL=y, set
a831881b 2447 the specified list of CPUs whose tick will be stopped
0453b435
FW
2448 whenever possible. The boot CPU will be forced outside
2449 the range to maintain the timekeeping.
d1e43fa5
FW
2450 The CPUs in this range must also be included in the
2451 rcu_nocbs= set.
a831881b 2452
eeee7853
PM
2453 noiotrap [SH] Disables trapped I/O port accesses.
2454
cd4f0ef7 2455 noirqdebug [X86-32] Disables the code which attempts to detect and
1da177e4
LT
2456 disable unhandled interrupt sources.
2457
6cececfc 2458 no_timer_check [X86,APIC] Disables the code which tests for
8542b200
ZA
2459 broken timer IRQ sources.
2460
1da177e4
LT
2461 noisapnp [ISAPNP] Disables ISA PnP code.
2462
2463 noinitrd [RAM] Tells the kernel not to load any configured
2464 initial RAM disk.
2465
03ea8155
WH
2466 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2467 remapping.
d1423d56 2468 [Deprecated - use intremap=off]
03ea8155 2469
1da177e4
LT
2470 nointroute [IA-64]
2471
16290246 2472 nojitter [IA-64] Disables jitter checking for ITC timers.
0aa366f3 2473
9cf4c4fc
JK
2474 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2475
fd10cde9
GN
2476 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2477 fault handling.
2478
d910f5c1
GC
2479 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2480 steal time is computed, but won't influence scheduler
2481 behaviour
2482
cd4f0ef7 2483 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1da177e4 2484
cd4f0ef7 2485 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
ad62ca2b 2486
1da177e4
LT
2487 noltlbs [PPC] Do not use large page/tlb entries for kernel
2488 lowmem mapping on PPC40x.
2489
312f1f01
H
2490 nomca [IA-64] Disable machine check abort handling
2491
13696e0a 2492 nomce [X86-32] Disable Machine Check Exception
abe37e5a 2493
83d7384f
AS
2494 nomfgpt [X86-32] Disable Multi-Function General Purpose
2495 Timer usage (for AMD Geode machines).
2496
bda62633
DZ
2497 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2498 shutdown the other cpus. Instead use the REBOOT_VECTOR
2499 irq.
2500
02608bef
DY
2501 nomodule Disable module load
2502
016ddd9b
JK
2503 nopat [X86] Disable PAT (page attribute table extension of
2504 pagetables) support.
2505
0cb55ad2
RD
2506 norandmaps Don't use address space randomization. Equivalent to
2507 echo 0 > /proc/sys/kernel/randomize_va_space
2508
bbff2168 2509 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
959b4fdf 2510
cd4f0ef7 2511 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
b7fb4af0
JF
2512 with UP alternatives
2513
7a5091d5
PA
2514 nordrand [X86] Disable kernel use of the RDRAND and
2515 RDSEED instructions even if they are supported
2516 by the processor. RDRAND and RDSEED are still
2517 available to user space applications.
49d859d7 2518
a9913044
RD
2519 noresume [SWSUSP] Disables resume and restores original swap
2520 space.
2521
1da177e4
LT
2522 no-scroll [VGA] Disables scrollback.
2523 This is required for the Braillex ib80-piezo Braille
2524 reader made by F.H. Papenmeier (Germany).
2525
2526 nosbagart [IA-64]
2527
cd4f0ef7 2528 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4f886511 2529
61ec7567
LB
2530 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2531 and disable the IO APIC. legacy for "maxcpus=0".
1da177e4 2532
97842216
DJ
2533 nosoftlockup [KNL] Disable the soft-lockup detector.
2534
1da177e4
LT
2535 nosync [HW,M68K] Disables sync negotiation for all devices.
2536
cd4f0ef7 2537 notsc [BUGS=X86-32] Disable Time Stamp Counter
1da177e4
LT
2538
2539 nousb [USB] Disable the USB subsystem
2540
195daf66
UO
2541 nowatchdog [KNL] Disable both lockup detectors, i.e.
2542 soft-lockup and NMI watchdog (hard-lockup).
58687acb 2543
1da177e4 2544 nowb [ARM]
a9913044 2545
2b2fd87a
WH
2546 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2547
f78cff48
FY
2548 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2549 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2550 Some features depend on CPU0. Known dependencies are:
2551 1. Resume from suspend/hibernate depends on CPU0.
2552 Suspend/hibernate will fail if CPU0 is offline and you
2553 need to online CPU0 before suspend/hibernate.
2554 2. PIC interrupts also depend on CPU0. CPU0 can't be
2555 removed if a PIC interrupt is detected.
2556 It's said poweroff/reboot may depend on CPU0 on some
2557 machines although I haven't seen such issues so far
2558 after CPU0 is offline on a few tested machines.
2559 If the dependencies are under your control, you can
2560 turn on cpu0_hotplug.
2561
16290246 2562 nptcg= [IA-64] Override max number of concurrent global TLB
a6c75b86
FY
2563 purges which is reported from either PAL_VM_SUMMARY or
2564 SAL PALO.
2565
2b633e3f
YL
2566 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2567 could support. nr_cpus=n : n >= 1 limits the kernel to
2568 supporting 'n' processors. Later in runtime you can not
2569 use hotplug cpu feature to put more cpu back to online.
2570 just like you compile the kernel NR_CPUS=n
2571
0cb55ad2
RD
2572 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2573
1a687c2e
MG
2574 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2575 Allowed values are enable and disable
2576
f0c0b2b8
KH
2577 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2578 one of ['zone', 'node', 'default'] can be specified
2579 This can be set from sysctl after boot.
2580 See Documentation/sysctl/vm.txt for details.
2581
7c4be253
RD
2582 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2583 See Documentation/debugging-via-ohci1394.txt for more
2584 info.
2585
3ef0e1f8
AS
2586 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2587 Rather than timing out after 20 ms if an EC
2588 command is not properly ACKed, override the length
2589 of the timeout. We have interrupts disabled while
2590 waiting for the ACK, so if this is set too high
2591 interrupts *may* be lost!
2592
15ac7afe
TL
2593 omap_mux= [OMAP] Override bootloader pin multiplexing.
2594 Format: <mux_mode0.mode_name=value>...
2595 For example, to override I2C bus2:
2596 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2597
1da177e4
LT
2598 oprofile.timer= [HW]
2599 Use timer interrupt instead of performance counters
2600
7e4e0bd5
RR
2601 oprofile.cpu_type= Force an oprofile cpu type
2602 This might be useful if you have an older oprofile
2603 userland or if you want common events.
8d7ff4f2
RR
2604 Format: { arch_perfmon }
2605 arch_perfmon: [X86] Force use of architectural
7e4e0bd5
RR
2606 perfmon on Intel CPUs instead of the
2607 CPU specific event set.
159a80b2
RR
2608 timer: [X86] Force use of architectural NMI
2609 timer mode (see also oprofile.timer
2610 for generic hr timer mode)
dd3c4670
AK
2611 [s390] Force legacy basic mode sampling
2612 (report cpu_type "timer")
1dcdb5a9 2613
44a4dcf7
RD
2614 oops=panic Always panic on oopses. Default is to just kill the
2615 process, but there is a small probability of
2616 deadlocking the machine.
d404ab0a
OH
2617 This will also cause panics on machine check exceptions.
2618 Useful together with panic=30 to trigger a reboot.
2619
bcfde334
RD
2620 OSS [HW,OSS]
2621 See Documentation/sound/oss/oss-parameters.txt
2622
48c96a36
JK
2623 page_owner= [KNL] Boot-time page_owner enabling option.
2624 Storage of the information about who allocated
2625 each page is disabled in default. With this switch,
2626 we can turn it on.
2627 on: enable the feature
2628
44a4dcf7 2629 panic= [KNL] Kernel behaviour on panic: delay <timeout>
4302fbc8
HD
2630 timeout > 0: seconds before rebooting
2631 timeout = 0: wait forever
2632 timeout < 0: reboot immediately
1da177e4
LT
2633 Format: <timeout>
2634
9e3961a0
PB
2635 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2636 on a WARN().
2637
f06e5153
MH
2638 crash_kexec_post_notifiers
2639 Run kdump after running panic-notifiers and dumping
2640 kmsg. This only for the users who doubt kdump always
2641 succeeds in any situation.
2642 Note that this also increases risks of kdump failure,
2643 because some panic notifiers can make the crashed
2644 kernel more unstable.
2645
1da177e4
LT
2646 parkbd.port= [HW] Parallel port number the keyboard adapter is
2647 connected to, default is 0.
2648 Format: <parport#>
2649 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2650 0 for XT, 1 for AT (default is AT).
a9913044
RD
2651 Format: <mode>
2652
2653 parport= [HW,PPT] Specify parallel ports. 0 disables.
2654 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2655 Use 'auto' to force the driver to use any
2656 IRQ/DMA settings detected (the default is to
2657 ignore detected IRQ/DMA settings because of
2658 possible conflicts). You can specify the base
2659 address, IRQ, and DMA settings; IRQ and DMA
2660 should be numbers, or 'auto' (for using detected
2661 settings on that particular port), or 'nofifo'
2662 (to avoid using a FIFO even if it is detected).
2663 Parallel ports are assigned in the order they
2664 are specified on the command line, starting
2665 with parport0.
2666
2667 parport_init_mode= [HW,PPT]
2668 Configure VIA parallel port to operate in
2669 a specific mode. This is necessary on Pegasos
2670 computer where firmware has no options for setting
2671 up parallel port mode and sets it to spp.
2672 Currently this function knows 686a and 8231 chips.
1da177e4
LT
2673 Format: [spp|ps2|epp|ecp|ecpepp]
2674
dd287796
AM
2675 pause_on_oops=
2676 Halt all CPUs after the first oops has been printed for
2677 the specified number of seconds. This is to be used if
2678 your oopses keep scrolling off the screen.
2679
1da177e4
LT
2680 pcbit= [HW,ISDN]
2681
2682 pcd. [PARIDE]
2683 See header of drivers/block/paride/pcd.c.
31c00fc1 2684 See also Documentation/blockdev/paride.txt.
1da177e4 2685
a9913044 2686 pci=option[,option...] [PCI] various PCI subsystem options:
1cc0ca26
BH
2687 earlydump [X86] dump PCI config space before the kernel
2688 changes anything
c0115606 2689 off [X86] don't probe for the PCI bus
cd4f0ef7 2690 bios [X86-32] force use of PCI BIOS, don't access
a9913044
RD
2691 the hardware directly. Use this if your machine
2692 has a non-standard PCI host bridge.
cd4f0ef7 2693 nobios [X86-32] disallow use of PCI BIOS, only direct
a9913044
RD
2694 hardware access methods are allowed. Use this
2695 if you experience crashes upon bootup and you
2696 suspect they are caused by the BIOS.
c0115606 2697 conf1 [X86] Force use of PCI Configuration
a9913044 2698 Mechanism 1.
c0115606 2699 conf2 [X86] Force use of PCI Configuration
a9913044 2700 Mechanism 2.
7f785763
RD
2701 noaer [PCIE] If the PCIEAER kernel config parameter is
2702 enabled, this kernel boot option can be used to
2703 disable the use of PCIE advanced error reporting.
32a2eea7
JG
2704 nodomains [PCI] Disable support for multiple PCI
2705 root domains (aka PCI segments, in ACPI-speak).
6cececfc 2706 nommconf [X86] Disable use of MMCONFIG for PCI
61be6d66 2707 Configuration
12983077
AH
2708 check_enable_amd_mmconf [X86] check for and enable
2709 properly configured MMIO access to PCI
2710 config space on AMD family 10h CPU
309e57df
MW
2711 nomsi [MSI] If the PCI_MSI kernel config parameter is
2712 enabled, this kernel boot option can be used to
2713 disable the use of MSI interrupts system-wide.
a9322f64
SA
2714 noioapicquirk [APIC] Disable all boot interrupt quirks.
2715 Safety option to keep boot IRQs enabled. This
2716 should never be necessary.
9197979b
SA
2717 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2718 primary IO-APIC for bridges that cannot disable
2719 boot IRQs. This fixes a source of spurious IRQs
2720 when the system masks IRQs.
41b9eb26
SA
2721 noioapicreroute [APIC] Disable workaround that uses the
2722 boot IRQ equivalent of an IRQ that connects to
2723 a chipset where boot IRQs cannot be disabled.
2724 The opposite of ioapicreroute.
cd4f0ef7 2725 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
a9913044
RD
2726 routing table. These calls are known to be buggy
2727 on several machines and they hang the machine
2728 when used, but on other computers it's the only
2729 way to get the interrupt routing table. Try
2730 this option if the kernel is unable to allocate
2731 IRQs or discover secondary PCI buses on your
2732 motherboard.
c0115606 2733 rom [X86] Assign address space to expansion ROMs.
a9913044
RD
2734 Use with caution as certain devices share
2735 address decoders between ROMs and other
2736 resources.
c0115606 2737 norom [X86] Do not assign address space to
bb71ad88
GH
2738 expansion ROMs that do not already have
2739 BIOS assigned address ranges.
7bd1c365
MH
2740 nobar [X86] Do not assign address space to the
2741 BARs that weren't assigned by the BIOS.
c0115606 2742 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
a9913044
RD
2743 assigned automatically to PCI devices. You can
2744 make the kernel exclude IRQs of your ISA cards
2745 this way.
c0115606 2746 pirqaddr=0xAAAAA [X86] Specify the physical address
a9913044
RD
2747 of the PIRQ table (normally generated
2748 by the BIOS) if it is outside the
2749 F0000h-100000h range.
c0115606 2750 lastbus=N [X86] Scan all buses thru bus #N. Can be
a9913044
RD
2751 useful if the kernel is unable to find your
2752 secondary buses and you want to tell it
2753 explicitly which ones they are.
c0115606 2754 assign-busses [X86] Always assign all PCI bus
a9913044
RD
2755 numbers ourselves, overriding
2756 whatever the firmware may have done.
c0115606 2757 usepirqmask [X86] Honor the possible IRQ mask stored
a9913044
RD
2758 in the BIOS $PIR table. This is needed on
2759 some systems with broken BIOSes, notably
2760 some HP Pavilion N5400 and Omnibook XE3
2761 notebooks. This will have no effect if ACPI
2762 IRQ routing is enabled.
c0115606 2763 noacpi [X86] Do not use ACPI for IRQ routing
a9913044 2764 or for PCI scanning.
7bc5e3f2
BH
2765 use_crs [X86] Use PCI host bridge window information
2766 from ACPI. On BIOSes from 2008 or later, this
2767 is enabled by default. If you need to use this,
2768 please report a bug.
2769 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2770 If you need to use this, please report a bug.
a9913044
RD
2771 routeirq Do IRQ routing for all PCI devices.
2772 This is normally done in pci_enable_device(),
2773 so this option is a temporary workaround
2774 for broken drivers that don't call it.
13a6ddb0
YL
2775 skip_isa_align [X86] do not align io start addr, so can
2776 handle more pci cards
a9913044
RD
2777 firmware [ARM] Do not re-enumerate the bus but instead
2778 just use the configuration from the
2779 bootloader. This is currently used on
2780 IXP2000 systems where the bus has to be
2781 configured a certain way for adjunct CPUs.
0637a70a
AK
2782 noearly [X86] Don't do any early type 1 scanning.
2783 This might help on some broken boards which
2784 machine check when some devices' config space
2785 is read. But various workarounds are disabled
2786 and some IOMMU drivers will not work.
6b4b78fe
MD
2787 bfsort Sort PCI devices into breadth-first order.
2788 This sorting is done to get a device
2789 order compatible with older (<= 2.4) kernels.
2790 nobfsort Don't sort PCI devices into breadth-first order.
fa238712
YW
2791 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2792 tuning and use the BIOS-configured MPS defaults.
2793 pcie_bus_safe Set every device's MPS to the largest value
2794 supported by all devices below the root complex.
2795 pcie_bus_perf Set device MPS to the largest allowable MPS
2796 based on its parent bus. Also set MRRS (Max
2797 Read Request Size) to the largest supported
2798 value (no larger than the MPS that the device
2799 or bus can support) for best performance.
2800 pcie_bus_peer2peer Set every device's MPS to 128B, which
2801 every device is guaranteed to support. This
2802 configuration allows peer-to-peer DMA between
2803 any pair of devices, possibly at the cost of
2804 reduced performance. This also guarantees
2805 that hot-added devices will work.
4516a618
AN
2806 cbiosize=nn[KMG] The fixed amount of bus space which is
2807 reserved for the CardBus bridge's IO window.
2808 The default value is 256 bytes.
2809 cbmemsize=nn[KMG] The fixed amount of bus space which is
2810 reserved for the CardBus bridge's memory
2811 window. The default value is 64 megabytes.
32a9a682
YS
2812 resource_alignment=
2813 Format:
2814 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2815 Specifies alignment and device to reassign
2816 aligned memory resources.
2817 If <order of align> is not specified,
2818 PAGE_SIZE is used as alignment.
2819 PCI-PCI bridge can be specified, if resource
2820 windows need to be expanded.
43c16408
AP
2821 ecrc= Enable/disable PCIe ECRC (transaction layer
2822 end-to-end CRC checking).
2823 bios: Use BIOS/firmware settings. This is the
2824 the default.
2825 off: Turn ECRC off
2826 on: Turn ECRC on.
8c8803c5
YW
2827 hpiosize=nn[KMG] The fixed amount of bus space which is
2828 reserved for hotplug bridge's IO window.
2829 Default size is 256 bytes.
2830 hpmemsize=nn[KMG] The fixed amount of bus space which is
2831 reserved for hotplug bridge's memory window.
2832 Default size is 2 megabytes.
b55438fd
YL
2833 realloc= Enable/disable reallocating PCI bridge resources
2834 if allocations done by BIOS are too small to
2835 accommodate resources required by all child
2836 devices.
2837 off: Turn realloc off
2838 on: Turn realloc on
2839 realloc same as realloc=on
6748dcc2 2840 noari do not use PCIe ARI.
284f5f9d
BH
2841 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2842 only look for one device below a PCIe downstream
2843 port.
6b4b78fe 2844
e5665a45
CE
2845 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2846 Management.
2847 off Disable ASPM.
2848 force Enable ASPM even on devices that claim not to support it.
2849 WARNING: Forcing ASPM on may cause system lockups.
2850
7570a333
MT
2851 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2852 nomsi Do not use MSI for PCI Express Native Hotplug (this
2853 makes all PCIe ports use INTx for hotplug services).
2854
79dd9182 2855 pcie_ports= [PCIE] PCIe ports handling:
28eb5f27
RW
2856 auto Ask the BIOS whether or not to use native PCIe services
2857 associated with PCIe ports (PME, hot-plug, AER). Use
2858 them only if that is allowed by the BIOS.
2859 native Use native PCIe services associated with PCIe ports
2860 unconditionally.
79dd9182
RW
2861 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2862 ports driver.
2863
c7f48656 2864 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
c39fae14 2865 nomsi Do not use MSI for native PCIe PME signaling (this makes
28eb5f27 2866 all PCIe root ports use INTx for all services).
c7f48656 2867
1da177e4
LT
2868 pcmv= [HW,PCMCIA] BadgePAD 4
2869
39ac5ba5
TB
2870 pd_ignore_unused
2871 [PM]
2872 Keep all power-domains already enabled by bootloader on,
2873 even if no driver has claimed them. This is useful
2874 for debug and development, but should not be
2875 needed on a platform with proper driver support.
2876
1da177e4 2877 pd. [PARIDE]
31c00fc1 2878 See Documentation/blockdev/paride.txt.
1da177e4
LT
2879
2880 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2881 boot time.
2882 Format: { 0 | 1 }
2883 See arch/parisc/kernel/pdc_chassis.c
2884
f58dc01b 2885 percpu_alloc= Select which percpu first chunk allocator to use.
e933a73f
TH
2886 Currently supported values are "embed" and "page".
2887 Archs may support subset or none of the selections.
2888 See comments in mm/percpu.c for details on each
2889 allocator. This parameter is primarily for debugging
2890 and performance comparison.
fa8a7094 2891
1da177e4 2892 pf. [PARIDE]
31c00fc1 2893 See Documentation/blockdev/paride.txt.
1da177e4
LT
2894
2895 pg. [PARIDE]
31c00fc1 2896 See Documentation/blockdev/paride.txt.
1da177e4
LT
2897
2898 pirq= [SMP,APIC] Manual mp-table setup
71cced6e 2899 See Documentation/x86/i386/IO-APIC.txt.
1da177e4
LT
2900
2901 plip= [PPT,NET] Parallel port network link
2902 Format: { parport<nr> | timid | 0 }
2903 See also Documentation/parport.txt.
2904
16290246 2905 pmtmr= [X86] Manual setup of pmtmr I/O Port.
de32a243
TG
2906 Override pmtimer IOPort with a hex value.
2907 e.g. pmtmr=0x508
2908
96242116
BH
2909 pnp.debug=1 [PNP]
2910 Enable PNP debug messages (depends on the
2911 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2912 via /sys/module/pnp/parameters/debug. We always show
2913 current resource usage; turning this on also shows
2914 possible settings and some assignment information.
97ef062b 2915
1da177e4
LT
2916 pnpacpi= [ACPI]
2917 { off }
2918
2919 pnpbios= [ISAPNP]
2920 { on | off | curr | res | no-curr | no-res }
2921
2922 pnp_reserve_irq=
2923 [ISAPNP] Exclude IRQs for the autoconfiguration
2924
2925 pnp_reserve_dma=
2926 [ISAPNP] Exclude DMAs for the autoconfiguration
2927
2928 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 2929 Ranges are in pairs (I/O port base and size).
1da177e4
LT
2930
2931 pnp_reserve_mem=
a9913044
RD
2932 [ISAPNP] Exclude memory regions for the
2933 autoconfiguration.
1da177e4
LT
2934 Ranges are in pairs (memory base and size).
2935
4af94f39
RD
2936 ports= [IP_VS_FTP] IPVS ftp helper module
2937 Default is 21.
2938 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2939 may be specified.
2940 Format: <port>,<port>....
2941
45807a1d
IM
2942 print-fatal-signals=
2943 [KNL] debug: print fatal signals
f84d49b2
NO
2944
2945 If enabled, warn about various signal handling
2946 related application anomalies: too many signals,
2947 too many POSIX.1 timers, fatal signals causing a
2948 coredump - etc.
2949
2950 If you hit the warning due to signal overflow,
2951 you might want to try "ulimit -i unlimited".
2952
45807a1d
IM
2953 default: off.
2954
c22ab332
MG
2955 printk.always_kmsg_dump=
2956 Trigger kmsg_dump for cases other than kernel oops or
2957 panics
2958 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2959 default: disabled
2960
e84845c4
RD
2961 printk.time= Show timing data prefixed to each printk message line
2962 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2963
0cb55ad2
RD
2964 processor.max_cstate= [HW,ACPI]
2965 Limit processor to maximum C-state
2966 max_cstate=9 overrides any DMI blacklist limit.
2967
2968 processor.nocst [HW,ACPI]
2969 Ignore the _CST method to determine C-states,
2970 instead using the legacy FADT method
2971
1da177e4 2972 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
2973 Format: [schedule,]<number>
2974 Param: "schedule" - profile schedule points.
2975 Param: <number> - step/bucket size as a power of 2 for
2976 statistical time based profiling.
b3da2a73
MG
2977 Param: "sleep" - profile D-state sleeping (millisecs).
2978 Requires CONFIG_SCHEDSTATS
c0fe2e69 2979 Param: "kvm" - profile VM exits.
1da177e4 2980
1da177e4
LT
2981 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2982 before loading.
31c00fc1 2983 See Documentation/blockdev/ramdisk.txt.
1da177e4 2984
a9913044
RD
2985 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2986 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
2987 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2988 per second.
a9913044
RD
2989 psmouse.resetafter= [HW,MOUSE]
2990 Try to reset the device after so many bad packets
1da177e4
LT
2991 (0 = never).
2992 psmouse.resolution=
2993 [HW,MOUSE] Set desired mouse resolution, in dpi.
2994 psmouse.smartscroll=
a9913044 2995 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
2996 0 = disabled, 1 = enabled (default).
2997
dee28e72
MG
2998 pstore.backend= Specify the name of the pstore backend to use
2999
1da177e4 3000 pt. [PARIDE]
31c00fc1 3001 See Documentation/blockdev/paride.txt.
1da177e4 3002
dc8c8587
KS
3003 pty.legacy_count=
3004 [KNL] Number of legacy pty's. Overwrites compiled-in
3005 default number.
3006
7d2c502f 3007 quiet [KNL] Disable most log messages
a9913044 3008
1da177e4
LT
3009 r128= [HW,DRM]
3010
3011 raid= [HW,RAID]
3012 See Documentation/md.txt.
3013
a9913044 3014 ramdisk_blocksize= [RAM]
31c00fc1 3015 See Documentation/blockdev/ramdisk.txt.
a9913044 3016
1da177e4 3017 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
31c00fc1 3018 See Documentation/blockdev/ramdisk.txt.
1da177e4 3019
4102adab 3020 rcu_nocbs= [KNL]
3fbfbf7a
PM
3021 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3022 the specified list of CPUs to be no-callback CPUs.
3023 Invocation of these CPUs' RCU callbacks will
a4889858
PM
3024 be offloaded to "rcuox/N" kthreads created for
3025 that purpose, where "x" is "b" for RCU-bh, "p"
3026 for RCU-preempt, and "s" for RCU-sched, and "N"
3027 is the CPU number. This reduces OS jitter on the
3fbfbf7a
PM
3028 offloaded CPUs, which can be useful for HPC and
3029 real-time workloads. It can also improve energy
3030 efficiency for asymmetric multiprocessors.
3031
4102adab 3032 rcu_nocb_poll [KNL]
3fbfbf7a
PM
3033 Rather than requiring that offloaded CPUs
3034 (specified by rcu_nocbs= above) explicitly
3035 awaken the corresponding "rcuoN" kthreads,
3036 make these kthreads poll for callbacks.
3037 This improves the real-time response for the
3038 offloaded CPUs by relieving them of the need to
3039 wake up the corresponding kthread, but degrades
3040 energy efficiency by requiring that the kthreads
3041 periodically wake up to do the polling.
3042
4102adab 3043 rcutree.blimit= [KNL]
97e63f0c
PM
3044 Set maximum number of finished RCU callbacks to
3045 process in one batch.
21a1ea9e 3046
a3dc2948
PM
3047 rcutree.dump_tree= [KNL]
3048 Dump the structure of the rcu_node combining tree
3049 out at early boot. This is used for diagnostic
3050 purposes, to verify correct tree setup.
3051
0f41c0dd
PM
3052 rcutree.gp_cleanup_delay= [KNL]
3053 Set the number of jiffies to delay each step of
3054 RCU grace-period cleanup. This only has effect
3055 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3056
37745d28
PM
3057 rcutree.gp_init_delay= [KNL]
3058 Set the number of jiffies to delay each step of
3059 RCU grace-period initialization. This only has
0f41c0dd
PM
3060 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3061 is set.
3062
3063 rcutree.gp_preinit_delay= [KNL]
3064 Set the number of jiffies to delay each step of
3065 RCU grace-period pre-initialization, that is,
3066 the propagation of recent CPU-hotplug changes up
3067 the rcu_node combining tree. This only has effect
3068 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
37745d28 3069
7fa27001
PM
3070 rcutree.rcu_fanout_exact= [KNL]
3071 Disable autobalancing of the rcu_node combining
3072 tree. This is used by rcutorture, and might
3073 possibly be useful for architectures having high
3074 cache-to-cache transfer latencies.
37745d28 3075
4102adab 3076 rcutree.rcu_fanout_leaf= [KNL]
f885b7f2
PM
3077 Increase the number of CPUs assigned to each
3078 leaf rcu_node structure. Useful for very large
3079 systems.
3080
4a81e832
PM
3081 rcutree.jiffies_till_sched_qs= [KNL]
3082 Set required age in jiffies for a
3083 given grace period before RCU starts
3084 soliciting quiescent-state help from
3085 rcu_note_context_switch().
3086
4102adab 3087 rcutree.jiffies_till_first_fqs= [KNL]
c0f4dfd4
PM
3088 Set delay from grace-period initialization to
3089 first attempt to force quiescent states.
3090 Units are jiffies, minimum value is zero,
3091 and maximum value is HZ.
3092
4102adab 3093 rcutree.jiffies_till_next_fqs= [KNL]
c0f4dfd4
PM
3094 Set delay between subsequent attempts to force
3095 quiescent states. Units are jiffies, minimum
3096 value is one, and maximum value is HZ.
3097
21871d7e 3098 rcutree.kthread_prio= [KNL,BOOT]
d2af1ad7
PM
3099 Set the SCHED_FIFO priority of the RCU per-CPU
3100 kthreads (rcuc/N). This value is also used for
3101 the priority of the RCU boost threads (rcub/N)
3102 and for the RCU grace-period kthreads (rcu_bh,
3103 rcu_preempt, and rcu_sched). If RCU_BOOST is
3104 set, valid values are 1-99 and the default is 1
3105 (the least-favored priority). Otherwise, when
3106 RCU_BOOST is not set, valid values are 0-99 and
3107 the default is zero (non-realtime operation).
21871d7e 3108
fbce7497
PM
3109 rcutree.rcu_nocb_leader_stride= [KNL]
3110 Set the number of NOCB kthread groups, which
3111 defaults to the square root of the number of
3112 CPUs. Larger numbers reduces the wakeup overhead
3113 on the per-CPU grace-period kthreads, but increases
3114 that same overhead on each group's leader.
3115
4102adab 3116 rcutree.qhimark= [KNL]
97e63f0c
PM
3117 Set threshold of queued RCU callbacks beyond which
3118 batch limiting is disabled.
21a1ea9e 3119
4102adab 3120 rcutree.qlowmark= [KNL]
24aaef8d
RD
3121 Set threshold of queued RCU callbacks below which
3122 batch limiting is re-enabled.
21a1ea9e 3123
4102adab 3124 rcutree.rcu_idle_gp_delay= [KNL]
c0f4dfd4
PM
3125 Set wakeup interval for idle CPUs that have
3126 RCU callbacks (RCU_FAST_NO_HZ=y).
d40011f6 3127
4102adab 3128 rcutree.rcu_idle_lazy_gp_delay= [KNL]
c0f4dfd4
PM
3129 Set wakeup interval for idle CPUs that have
3130 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3131 Lazy RCU callbacks are those which RCU can
3132 prove do nothing more than free memory.
d40011f6 3133
38706bc5
PM
3134 rcutorture.cbflood_inter_holdoff= [KNL]
3135 Set holdoff time (jiffies) between successive
3136 callback-flood tests.
3137
3138 rcutorture.cbflood_intra_holdoff= [KNL]
3139 Set holdoff time (jiffies) between successive
3140 bursts of callbacks within a given callback-flood
3141 test.
3142
3143 rcutorture.cbflood_n_burst= [KNL]
3144 Set the number of bursts making up a given
3145 callback-flood test. Set this to zero to
3146 disable callback-flood testing.
3147
3148 rcutorture.cbflood_n_per_burst= [KNL]
3149 Set the number of callbacks to be registered
3150 in a given burst of a callback-flood test.
3151
4102adab 3152 rcutorture.fqs_duration= [KNL]
dabb8aa9
PM
3153 Set duration of force_quiescent_state bursts.
3154
4102adab 3155 rcutorture.fqs_holdoff= [KNL]
dabb8aa9
PM
3156 Set holdoff time within force_quiescent_state bursts.
3157
4102adab 3158 rcutorture.fqs_stutter= [KNL]
dabb8aa9
PM
3159 Set wait time between force_quiescent_state bursts.
3160
4102adab
PM
3161 rcutorture.gp_exp= [KNL]
3162 Use expedited update-side primitives.
3163
3164 rcutorture.gp_normal= [KNL]
3165 Use normal (non-expedited) update-side primitives.
3166 If both gp_exp and gp_normal are set, do both.
3167 If neither gp_exp nor gp_normal are set, still
3168 do both.
dabb8aa9 3169
4102adab 3170 rcutorture.n_barrier_cbs= [KNL]
dabb8aa9
PM
3171 Set callbacks/threads for rcu_barrier() testing.
3172
4102adab 3173 rcutorture.nfakewriters= [KNL]
dabb8aa9
PM
3174 Set number of concurrent RCU writers. These just
3175 stress RCU, they don't participate in the actual
3176 test, hence the "fake".
3177
4102adab 3178 rcutorture.nreaders= [KNL]
3838cc18
PM
3179 Set number of RCU readers. The value -1 selects
3180 N-1, where N is the number of CPUs. A value
3181 "n" less than -1 selects N-n-2, where N is again
3182 the number of CPUs. For example, -2 selects N
3183 (the number of CPUs), -3 selects N+1, and so on.
dabb8aa9 3184
4102adab
PM
3185 rcutorture.object_debug= [KNL]
3186 Enable debug-object double-call_rcu() testing.
3187
3188 rcutorture.onoff_holdoff= [KNL]
dabb8aa9
PM
3189 Set time (s) after boot for CPU-hotplug testing.
3190
4102adab 3191 rcutorture.onoff_interval= [KNL]
dabb8aa9
PM
3192 Set time (s) between CPU-hotplug operations, or
3193 zero to disable CPU-hotplug testing.
3194
59da22a0 3195 rcutorture.torture_runnable= [BOOT]
4102adab
PM
3196 Start rcutorture running at boot time.
3197
3198 rcutorture.shuffle_interval= [KNL]
dabb8aa9
PM
3199 Set task-shuffle interval (s). Shuffling tasks
3200 allows some CPUs to go into dyntick-idle mode
3201 during the rcutorture test.
3202
4102adab 3203 rcutorture.shutdown_secs= [KNL]
dabb8aa9
PM
3204 Set time (s) after boot system shutdown. This
3205 is useful for hands-off automated testing.
3206
4102adab 3207 rcutorture.stall_cpu= [KNL]
dabb8aa9
PM
3208 Duration of CPU stall (s) to test RCU CPU stall
3209 warnings, zero to disable.
3210
4102adab 3211 rcutorture.stall_cpu_holdoff= [KNL]
dabb8aa9
PM
3212 Time to wait (s) after boot before inducing stall.
3213
4102adab 3214 rcutorture.stat_interval= [KNL]
dabb8aa9
PM
3215 Time (s) between statistics printk()s.
3216
4102adab 3217 rcutorture.stutter= [KNL]
dabb8aa9
PM
3218 Time (s) to stutter testing, for example, specifying
3219 five seconds causes the test to run for five seconds,
3220 wait for five seconds, and so on. This tests RCU's
3221 ability to transition abruptly to and from idle.
3222
4102adab 3223 rcutorture.test_boost= [KNL]
dabb8aa9
PM
3224 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3225 "Maybe" means test if the RCU implementation
3226 under test support RCU priority boosting.
3227
4102adab 3228 rcutorture.test_boost_duration= [KNL]
dabb8aa9
PM
3229 Duration (s) of each individual boost test.
3230
4102adab 3231 rcutorture.test_boost_interval= [KNL]
dabb8aa9
PM
3232 Interval (s) between each boost test.
3233
4102adab 3234 rcutorture.test_no_idle_hz= [KNL]
dabb8aa9
PM
3235 Test RCU's dyntick-idle handling. See also the
3236 rcutorture.shuffle_interval parameter.
3237
4102adab 3238 rcutorture.torture_type= [KNL]
dabb8aa9
PM
3239 Specify the RCU implementation to test.
3240
4102adab 3241 rcutorture.verbose= [KNL]
dabb8aa9
PM
3242 Enable additional printk() statements.
3243
4102adab
PM
3244 rcupdate.rcu_expedited= [KNL]
3245 Use expedited grace-period primitives, for
3246 example, synchronize_rcu_expedited() instead
3247 of synchronize_rcu(). This reduces latency,
3248 but can increase CPU utilization, degrade
3249 real-time latency, and degrade energy efficiency.
3250
3251 rcupdate.rcu_cpu_stall_suppress= [KNL]
3252 Suppress RCU CPU stall warning messages.
3253
3254 rcupdate.rcu_cpu_stall_timeout= [KNL]
3255 Set timeout for RCU CPU stall warning messages.
3256
52db30ab
PM
3257 rcupdate.rcu_task_stall_timeout= [KNL]
3258 Set timeout in jiffies for RCU task stall warning
3259 messages. Disable with a value less than or equal
3260 to zero.
3261
74860fee
PK
3262 rcupdate.rcu_self_test= [KNL]
3263 Run the RCU early boot self tests
3264
3265 rcupdate.rcu_self_test_bh= [KNL]
3266 Run the RCU bh early boot self tests
3267
3268 rcupdate.rcu_self_test_sched= [KNL]
3269 Run the RCU sched early boot self tests
3270
ffdfc409
OJ
3271 rdinit= [KNL]
3272 Format: <full_path>
3273 Run specified binary instead of /init from the ramdisk,
3274 used for early userspace startup. See initrd.
3275
1b3a5d02
RH
3276 reboot= [KNL]
3277 Format (x86 or x86_64):
3278 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3279 [[,]s[mp]#### \
3280 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3281 [[,]f[orce]
3282 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3283 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3284 reboot_force is either force or not specified,
3285 reboot_cpu is s[mp]#### with #### being the processor
3286 to be used for rebooting.
1da177e4 3287
46b6d94e
PJ
3288 relax_domain_level=
3289 [KNL, SMP] Set scheduler's default relax_domain_level.
21acb9ca 3290 See Documentation/cgroups/cpusets.txt.
46b6d94e 3291
0399d4db
RW
3292 relative_sleep_states=
3293 [SUSPEND] Use sleep state labeling where the deepest
3294 state available other than hibernation is always "mem".
3295 Format: { "0" | "1" }
3296 0 -- Traditional sleep state labels.
3297 1 -- Relative sleep state labels.
3298
1da177e4
LT
3299 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3300
cd4f0ef7 3301 reservetop= [X86-32]
461a9aff
ZA
3302 Format: nn[KMG]
3303 Reserves a hole at the top of the kernel virtual
3304 address space.
3305
9ea77bdb
PA
3306 reservelow= [X86]
3307 Format: nn[K]
3308 Set the amount of memory to reserve for BIOS at
3309 the bottom of the address space.
3310
7e96287d
VG
3311 reset_devices [KNL] Force drivers to reset the underlying device
3312 during initialization.
3313
a9913044
RD
3314 resume= [SWSUSP]
3315 Specify the partition device for software suspend
2df83fa4
MB
3316 Format:
3317 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
1da177e4 3318
ecbd0da1
RW
3319 resume_offset= [SWSUSP]
3320 Specify the offset from the beginning of the partition
3321 given by "resume=" at which the swap header is located,
3322 in <PAGE_SIZE> units (needed only for swap files).
3323 See Documentation/power/swsusp-and-swap-files.txt
3324
f126f733
BS
3325 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3326 read the resume files
3327
6f8d7022
BS
3328 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3329 Useful for devices that are detected asynchronously
3330 (e.g. USB and MMC devices).
3331
f996fc96
BS
3332 hibernate= [HIBERNATION]
3333 noresume Don't check if there's a hibernation image
3334 present during boot.
3335 nocompress Don't compress/decompress hibernation images.
a6e15a39 3336 no Disable hibernation and resume.
f996fc96 3337
0a7b35cb
MN
3338 retain_initrd [RAM] Keep initrd memory after extraction
3339
0efbb786
AC
3340 rfkill.default_state=
3341 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3342 etc. communication is blocked by default.
3343 1 Unblocked.
3344
3345 rfkill.master_switch_mode=
3346 0 The "airplane mode" button does nothing.
3347 1 The "airplane mode" button toggles between everything
3348 blocked and the previous configuration.
3349 2 The "airplane mode" button toggles between everything
3350 blocked and everything unblocked.
3351
1da177e4
LT
3352 rhash_entries= [KNL,NET]
3353 Set number of hash buckets for route cache
3354
1da177e4
LT
3355 ro [KNL] Mount root device read-only on boot
3356
3357 root= [KNL] Root filesystem
f2d34fd9 3358 See name_to_dev_t comment in init/do_mounts.c.
1da177e4
LT
3359
3360 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3361 mount the root filesystem
3362
3363 rootflags= [KNL] Set root filesystem mount option string
3364
3365 rootfstype= [KNL] Set root filesystem type
3366
cc1ed754
PO
3367 rootwait [KNL] Wait (indefinitely) for root device to show up.
3368 Useful for devices that are detected asynchronously
3369 (e.g. USB and MMC devices).
3370
5c71d618
RT
3371 rproc_mem=nn[KMG][@address]
3372 [KNL,ARM,CMA] Remoteproc physical memory block.
3373 Memory area to be used by remote processor image,
3374 managed by CMA.
3375
1da177e4
LT
3376 rw [KNL] Mount root device read-write on boot
3377
3378 S [KNL] Run init in single mode
3379
c60d1ae4
GS
3380 s390_iommu= [HW,S390]
3381 Set s390 IOTLB flushing mode
3382 strict
3383 With strict flushing every unmap operation will result in
3384 an IOTLB flush. Default is lazy flushing before reuse,
3385 which is faster.
3386
1da177e4
LT
3387 sa1100ir [NET]
3388 See drivers/net/irda/sa1100_ir.c.
3389
1da177e4 3390 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 3391
f6630114
MT
3392 sched_debug [KNL] Enables verbose scheduler debug messages.
3393
5307c955
MG
3394 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3395 xtime_lock contention on larger systems, and/or RCU lock
3396 contention on all systems with CONFIG_MAXSMP set.
3397 Format: { "0" | "1" }
3398 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3399 1 -- enable.
3400 Note: increases power consumption, thus should only be
3401 enabled if running jitter sensitive (HPC/RT) workloads.
3402
0cb55ad2
RD
3403 security= [SECURITY] Choose a security module to enable at boot.
3404 If this boot parameter is not specified, only the first
3405 security module asking for security registration will be
3406 loaded. An invalid security module name will be treated
3407 as if no module has been chosen.
3408
3409 selinux= [SELINUX] Disable or enable SELinux at boot time.
1da177e4
LT
3410 Format: { "0" | "1" }
3411 See security/selinux/Kconfig help text.
3412 0 -- disable.
3413 1 -- enable.
3414 Default value is set via kernel config option.
3415 If enabled at boot time, /selinux/disable can be used
3416 later to disable prior to initial policy load.
3417
c1c124e9
JJ
3418 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3419 Format: { "0" | "1" }
3420 See security/apparmor/Kconfig help text
3421 0 -- disable.
3422 1 -- enable.
3423 Default value is set via kernel config option.
3424
cd4f0ef7 3425 serialnumber [BUGS=X86-32]
1da177e4 3426
1da177e4
LT
3427 shapers= [NET]
3428 Maximal number of shapers.
a9913044 3429
b05f78f5
YL
3430 show_msr= [x86] show boot-time MSR settings
3431 Format: { <integer> }
3432 Show boot-time (BIOS-initialized) MSR settings.
3433 The parameter means the number of CPUs to show,
3434 for example 1 means boot CPU only.
3435
1da177e4
LT
3436 simeth= [IA-64]
3437 simscsi=
a9913044 3438
1da177e4
LT
3439 slram= [HW,MTD]
3440
423c929c
JK
3441 slab_nomerge [MM]
3442 Disable merging of slabs with similar size. May be
3443 necessary if there is some reason to distinguish
3444 allocs to different slabs. Debug options disable
3445 merging on their own.
3446 For more information see Documentation/vm/slub.txt.
3447
3df1cccd
DR
3448 slab_max_order= [MM, SLAB]
3449 Determines the maximum allowed order for slabs.
3450 A high setting may cause OOMs due to memory
3451 fragmentation. Defaults to 1 for systems with
3452 more than 32MB of RAM, 0 otherwise.
3453
f0630fff
CL
3454 slub_debug[=options[,slabs]] [MM, SLUB]
3455 Enabling slub_debug allows one to determine the
3456 culprit if slab objects become corrupted. Enabling
3457 slub_debug can create guard zones around objects and
3458 may poison objects when not in use. Also tracks the
3459 last alloc / free. For more information see
3460 Documentation/vm/slub.txt.
c1aee215
CL
3461
3462 slub_max_order= [MM, SLUB]
f0630fff
CL
3463 Determines the maximum allowed order for slabs.
3464 A high setting may cause OOMs due to memory
3465 fragmentation. For more information see
3466 Documentation/vm/slub.txt.
c1aee215
CL
3467
3468 slub_min_objects= [MM, SLUB]
f0630fff
CL
3469 The minimum number of objects per slab. SLUB will
3470 increase the slab order up to slub_max_order to
3471 generate a sufficiently large slab able to contain
3472 the number of objects indicated. The higher the number
3473 of objects the smaller the overhead of tracking slabs
3474 and the less frequently locks need to be acquired.
c1aee215
CL
3475 For more information see Documentation/vm/slub.txt.
3476
3477 slub_min_order= [MM, SLUB]
24775d65 3478 Determines the minimum page order for slabs. Must be
f0630fff 3479 lower than slub_max_order.
c1aee215
CL
3480 For more information see Documentation/vm/slub.txt.
3481
3482 slub_nomerge [MM, SLUB]
423c929c
JK
3483 Same with slab_nomerge. This is supported for legacy.
3484 See slab_nomerge for more information.
c1aee215 3485
1da177e4
LT
3486 smart2= [HW]
3487 Format: <io1>[,<io2>[,...,<io8>]]
3488
d0d4f69b
BH
3489 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3490 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3491 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3492 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3493 smsc-ircc2.ircc_irq= [HW] IRQ line
3494 smsc-ircc2.ircc_dma= [HW] DMA channel
3495 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3496 0: Toshiba Satellite 1800 (GP data pin select)
3497 1: Fast pin select (default)
3498 2: ATC IRMode
3499
9c44bc03
IM
3500 softlockup_panic=
3501 [KNL] Should the soft-lockup detector generate panics.
44a4dcf7 3502 Format: <integer>
9c44bc03 3503
ed235875
AT
3504 softlockup_all_cpu_backtrace=
3505 [KNL] Should the soft-lockup detector generate
3506 backtraces on all cpus.
3507 Format: <integer>
3508
1da177e4 3509 sonypi.*= [HW] Sony Programmable I/O Control Device driver
395cf969 3510 See Documentation/laptops/sonypi.txt
1da177e4 3511
1da177e4
LT
3512 spia_io_base= [HW,MTD]
3513 spia_fio_base=
3514 spia_pedr=
3515 spia_peddr=
3516
f38f1d2a
SR
3517 stacktrace [FTRACE]
3518 Enabled the stack tracer on boot up.
3519
762e1207
SR
3520 stacktrace_filter=[function-list]
3521 [FTRACE] Limit the functions that the stack tracer
3522 will trace at boot up. function-list is a comma separated
3523 list of functions. This list can be changed at run
3524 time by the stack_trace_filter file in the debugfs
3525 tracing directory. Note, this enables stack tracing
3526 and the stacktrace above is not needed.
3527
1da177e4
LT
3528 sti= [PARISC,HW]
3529 Format: <num>
3530 Set the STI (builtin display/keyboard on the HP-PARISC
3531 machines) console (graphic card) which should be used
3532 as the initial boot-console.
3533 See also comment in drivers/video/console/sticore.c.
3534
3535 sti_font= [HW]
3536 See comment in drivers/video/console/sticore.c.
3537
3538 stifb= [HW]
3539 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3540
cbf11071
TM
3541 sunrpc.min_resvport=
3542 sunrpc.max_resvport=
3543 [NFS,SUNRPC]
3544 SunRPC servers often require that client requests
3545 originate from a privileged port (i.e. a port in the
3546 range 0 < portnr < 1024).
3547 An administrator who wishes to reserve some of these
3548 ports for other uses may adjust the range that the
3549 kernel's sunrpc client considers to be privileged
3550 using these two parameters to set the minimum and
3551 maximum port values.
3552
42a7fc4a
GB
3553 sunrpc.pool_mode=
3554 [NFS]
3555 Control how the NFS server code allocates CPUs to
3556 service thread pools. Depending on how many NICs
3557 you have and where their interrupts are bound, this
3558 option will affect which CPUs will do NFS serving.
3559 Note: this parameter cannot be changed while the
3560 NFS server is running.
3561
3562 auto the server chooses an appropriate mode
3563 automatically using heuristics
3564 global a single global pool contains all CPUs
3565 percpu one pool for each CPU
3566 pernode one pool for each NUMA node (equivalent
3567 to global on non-NUMA machines)
3568
cbf11071
TM
3569 sunrpc.tcp_slot_table_entries=
3570 sunrpc.udp_slot_table_entries=
3571 [NFS,SUNRPC]
3572 Sets the upper limit on the number of simultaneous
3573 RPC calls that can be sent from the client to a
3574 server. Increasing these values may allow you to
3575 improve throughput, but will also increase the
3576 amount of memory reserved for use by the client.
3577
1d4a9c17
BN
3578 suspend.pm_test_delay=
3579 [SUSPEND]
3580 Sets the number of seconds to remain in a suspend test
3581 mode before resuming the system (see
3582 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3583 is set. Default value is 5.
3584
07555ac1 3585 swapaccount=[0|1]
a42c390c
MH
3586 [KNL] Enable accounting of swap in memory resource
3587 controller if no parameter or 1 is given or disable
3588 it if 0 is given (See Documentation/cgroups/memory.txt)
3589
91fec0f5
JK
3590 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3591 Format: { <int> | force }
3592 <int> -- Number of I/O TLB slabs
3593 force -- force using of bounce buffers even if they
3594 wouldn't be automatically used by the kernel
a9913044 3595
1da177e4
LT
3596 switches= [HW,M68k]
3597
e52eec13
AK
3598 sysfs.deprecated=0|1 [KNL]
3599 Enable/disable old style sysfs layout for old udev
3600 on older distributions. When this option is enabled
3601 very new udev will not work anymore. When this option
3602 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3603 in older udev will not work anymore.
3604 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3605 the kernel configuration.
3606
5d6f647f
IM
3607 sysrq_always_enabled
3608 [KNL]
3609 Ignore sysrq setting - this boot parameter will
3610 neutralize any effect of /proc/sys/kernel/sysrq.
3611 Useful for debugging.
3612
747029a5
FF
3613 tcpmhash_entries= [KNL,NET]
3614 Set the number of tcp_metrics_hash slots.
3615 Default value is 8192 or 16384 depending on total
3616 ram pages. This is used to specify the TCP metrics
3617 cache size. See Documentation/networking/ip-sysctl.txt
3618 "tcp_no_metrics_save" section for more details.
3619
1da177e4
LT
3620 tdfx= [HW,DRM]
3621
acc82342 3622 test_suspend= [SUSPEND][,N]
77437fd4 3623 Specify "mem" (for Suspend-to-RAM) or "standby" (for
acc82342
SP
3624 standby suspend) or "freeze" (for suspend type freeze)
3625 as the system sleep state during system startup with
3626 the optional capability to repeat N number of times.
3627 The system is woken from this state using a
3628 wakeup-capable RTC alarm.
77437fd4 3629
1da177e4
LT
3630 thash_entries= [KNL,NET]
3631 Set number of hash buckets for TCP connection
3632
f8707ec9
LB
3633 thermal.act= [HW,ACPI]
3634 -1: disable all active trip points in all thermal zones
3635 <degrees C>: override all lowest active trip points
3636
c52a7419
LB
3637 thermal.crt= [HW,ACPI]
3638 -1: disable all critical trip points in all thermal zones
22a94d79 3639 <degrees C>: override all critical trip points
c52a7419 3640
f5487145
LB
3641 thermal.nocrt= [HW,ACPI]
3642 Set to disable actions on ACPI thermal zone
3643 critical and hot trip points.
3644
72b33ef8
LB
3645 thermal.off= [HW,ACPI]
3646 1: disable ACPI thermal control
3647
a70cdc52
LB
3648 thermal.psv= [HW,ACPI]
3649 -1: disable all passive trip points
ada9cfdd
RD
3650 <degrees C>: override all passive trip points to this
3651 value
a70cdc52 3652
730ff34d
LB
3653 thermal.tzp= [HW,ACPI]
3654 Specify global default ACPI thermal zone polling rate
3655 <deci-seconds>: poll all this frequency
3656 0: no polling (default)
3657
8d32a307
TG
3658 threadirqs [KNL]
3659 Force threading of all interrupt handlers except those
24775d65 3660 marked explicitly IRQF_NO_THREAD.
8d32a307 3661
2ca62b04
KRW
3662 tmem [KNL,XEN]
3663 Enable the Transcendent memory driver if built-in.
3664
3665 tmem.cleancache=0|1 [KNL, XEN]
3666 Default is on (1). Disable the usage of the cleancache
3667 API to send anonymous pages to the hypervisor.
3668
3669 tmem.frontswap=0|1 [KNL, XEN]
3670 Default is on (1). Disable the usage of the frontswap
37d46e15
KRW
3671 API to send swap pages to the hypervisor. If disabled
3672 the selfballooning and selfshrinking are force disabled.
2ca62b04
KRW
3673
3674 tmem.selfballooning=0|1 [KNL, XEN]
3675 Default is on (1). Disable the driving of swap pages
3676 to the hypervisor.
3677
3678 tmem.selfshrinking=0|1 [KNL, XEN]
3679 Default is on (1). Partial swapoff that immediately
3680 transfers pages from Xen hypervisor back to the
3681 kernel based on different criteria.
3682
2b1a61f0
HC
3683 topology= [S390]
3684 Format: {off | on}
3685 Specify if the kernel should make use of the cpu
f65e51d7
SL
3686 topology information if the hardware supports this.
3687 The scheduler will make use of this information and
2b1a61f0 3688 e.g. base its process migration decisions on it.
c9af3fa9 3689 Default is on.
2b1a61f0 3690
2d73bae1
NA
3691 topology_updates= [KNL, PPC, NUMA]
3692 Format: {off}
3693 Specify if the kernel should ignore (off)
3694 topology updates sent by the hypervisor to this
3695 LPAR.
3696
1da177e4
LT
3697 tp720= [HW,PS2]
3698
225a9be2
RA
3699 tpm_suspend_pcr=[HW,TPM]
3700 Format: integer pcr id
3701 Specify that at suspend time, the tpm driver
3702 should extend the specified pcr with zeros,
3703 as a workaround for some chips which fail to
3704 flush the last written pcr on TPM_SaveState.
3705 This will guarantee that all the other pcrs
3706 are saved.
3707
9d612bef 3708 trace_buf_size=nn[KMG]
3e6fb8e9 3709 [FTRACE] will set tracing buffer size on each cpu.
631595fb 3710
020e5f85
LZ
3711 trace_event=[event-list]
3712 [FTRACE] Set and start specified trace events in order
3713 to facilitate early boot debugging.
3714 See also Documentation/trace/events.txt
3715
7bcfaf54
SR
3716 trace_options=[option-list]
3717 [FTRACE] Enable or disable tracer options at boot.
3718 The option-list is a comma delimited list of options
3719 that can be enabled or disabled just as if you were
3720 to echo the option name into
3721
3722 /sys/kernel/debug/tracing/trace_options
3723
3724 For example, to enable stacktrace option (to dump the
3725 stack trace of each event), add to the command line:
3726
3727 trace_options=stacktrace
3728
3729 See also Documentation/trace/ftrace.txt "trace options"
3730 section.
3731
0daa2302
SRRH
3732 tp_printk[FTRACE]
3733 Have the tracepoints sent to printk as well as the
3734 tracing ring buffer. This is useful for early boot up
3735 where the system hangs or reboots and does not give the
3736 option for reading the tracing buffer or performing a
3737 ftrace_dump_on_oops.
3738
3739 To turn off having tracepoints sent to printk,
3740 echo 0 > /proc/sys/kernel/tracepoint_printk
3741 Note, echoing 1 into this file without the
3742 tracepoint_printk kernel cmdline option has no effect.
3743
3744 ** CAUTION **
3745
3746 Having tracepoints sent to printk() and activating high
3747 frequency tracepoints such as irq or sched, can cause
3748 the system to live lock.
3749
de7edd31
SRRH
3750 traceoff_on_warning
3751 [FTRACE] enable this option to disable tracing when a
3752 warning is hit. This turns off "tracing_on". Tracing can
3753 be enabled again by echoing '1' into the "tracing_on"
3754 file located in /sys/kernel/debug/tracing/
3755
3756 This option is useful, as it disables the trace before
3757 the WARNING dump is called, which prevents the trace to
3758 be filled with content caused by the warning output.
3759
3760 This option can also be set at run time via the sysctl
3761 option: kernel/traceoff_on_warning
3762
fcf4d821
JK
3763 transparent_hugepage=
3764 [KNL]
3765 Format: [always|madvise|never]
3766 Can be used to control the default behavior of the system
3767 with respect to transparent hugepages.
3768 See Documentation/vm/transhuge.txt for more details.
3769
d3b8f889 3770 tsc= Disable clocksource stability checks for TSC.
395628ef
AK
3771 Format: <string>
3772 [x86] reliable: mark tsc clocksource as reliable, this
d3b8f889 3773 disables clocksource verification at runtime, as well
3774 as the stability checks done at bootup. Used to enable
3775 high-resolution timer mode on older hardware, and in
3776 virtualized environment.
e82b8e4e
VP
3777 [x86] noirqtime: Do not use TSC to do irq accounting.
3778 Used to run time disable IRQ_TIME_ACCOUNTING on any
3779 platforms where RDTSC is slow and this accounting
3780 can add overhead.
395628ef 3781
a9913044
RD
3782 turbografx.map[2|3]= [HW,JOY]
3783 TurboGraFX parallel port interface
3784 Format:
3785 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
3786 See also Documentation/input/joystick-parport.txt
3787
b6935f8c
CK
3788 udbg-immortal [PPC] When debugging early kernel crashes that
3789 happen after console_init() and before a proper
3790 console driver takes over, this boot options might
3791 help "seeing" what's going on.
3792
f86dcc5a
ED
3793 uhash_entries= [KNL,NET]
3794 Set number of hash buckets for UDP/UDP-Lite connections
3795
5f8364b7
AS
3796 uhci-hcd.ignore_oc=
3797 [USB] Ignore overcurrent events (default N).
3798 Some badly-designed motherboards generate lots of
3799 bogus events, for ports that aren't wired to
3800 anything. Set this parameter to avoid log spamming.
3801 Note that genuine overcurrent events won't be
3802 reported either.
3803
e3a61b0a 3804 unknown_nmi_panic
44a4dcf7 3805 [X86] Cause panic on unknown NMI.
e3a61b0a 3806
c4fc2342
CDH
3807 usbcore.authorized_default=
3808 [USB] Default USB device authorization:
3809 (default -1 = authorized except for wireless USB,
3810 0 = not authorized, 1 = authorized)
3811
b5e795f8
AS
3812 usbcore.autosuspend=
3813 [USB] The autosuspend time delay (in seconds) used
3814 for newly-detected USB devices (default 2). This
3815 is the time required before an idle device will be
3816 autosuspended. Devices for which the delay is set
eaafbc3a 3817 to a negative value won't be autosuspended at all.
b5e795f8 3818
fd7c519d
JK
3819 usbcore.usbfs_snoop=
3820 [USB] Set to log all usbfs traffic (default 0 = off).
3821
3822 usbcore.blinkenlights=
3823 [USB] Set to cycle leds on hubs (default 0 = off).
3824
3825 usbcore.old_scheme_first=
3826 [USB] Start with the old device initialization
3827 scheme (default 0 = off).
3828
3f5eb8d5
AS
3829 usbcore.usbfs_memory_mb=
3830 [USB] Memory limit (in MB) for buffers allocated by
3831 usbfs (default = 16, 0 = max = 2047).
3832
fd7c519d
JK
3833 usbcore.use_both_schemes=
3834 [USB] Try the other device initialization scheme
3835 if the first one fails (default 1 = enabled).
3836
3837 usbcore.initial_descriptor_timeout=
3838 [USB] Specifies timeout for the initial 64-byte
3839 USB_REQ_GET_DESCRIPTOR request in milliseconds
3840 (default 5000 = 5.0 seconds).
3841
1da177e4
LT
3842 usbhid.mousepoll=
3843 [USBHID] The interval which mice are to be polled at.
a9913044 3844
d4f373e5
AS
3845 usb-storage.delay_use=
3846 [UMS] The delay in seconds before a new device is
19101954 3847 scanned for Logical Units (default 1).
d4f373e5
AS
3848
3849 usb-storage.quirks=
3850 [UMS] A list of quirks entries to supplement or
3851 override the built-in unusual_devs list. List
3852 entries are separated by commas. Each entry has
3853 the form VID:PID:Flags where VID and PID are Vendor
3854 and Product ID values (4-digit hex numbers) and
3855 Flags is a set of characters, each corresponding
3856 to a common usb-storage quirk flag as follows:
c838ea46
AS
3857 a = SANE_SENSE (collect more than 18 bytes
3858 of sense data);
a0bb1081
AS
3859 b = BAD_SENSE (don't collect more than 18
3860 bytes of sense data);
d4f373e5
AS
3861 c = FIX_CAPACITY (decrease the reported
3862 device capacity by one sector);
5116901d
KR
3863 d = NO_READ_DISC_INFO (don't use
3864 READ_DISC_INFO command);
3865 e = NO_READ_CAPACITY_16 (don't use
3866 READ_CAPACITY_16 command);
734016b0
HG
3867 f = NO_REPORT_OPCODES (don't use report opcodes
3868 command, uas only);
ee136af4
HG
3869 g = MAX_SECTORS_240 (don't transfer more than
3870 240 sectors at a time, uas only);
c838ea46
AS
3871 h = CAPACITY_HEURISTICS (decrease the
3872 reported device capacity by one
3873 sector if the number is odd);
d4f373e5
AS
3874 i = IGNORE_DEVICE (don't bind to this
3875 device);
3876 l = NOT_LOCKABLE (don't try to lock and
3877 unlock ejectable media);
3878 m = MAX_SECTORS_64 (don't transfer more
3879 than 64 sectors = 32 KB at a time);
21c13a4f
AS
3880 n = INITIAL_READ10 (force a retry of the
3881 initial READ(10) command);
c838ea46
AS
3882 o = CAPACITY_OK (accept the capacity
3883 reported by the device);
eaa05dfc
NJ
3884 p = WRITE_CACHE (the device cache is ON
3885 by default);
d4f373e5
AS
3886 r = IGNORE_RESIDUE (the device reports
3887 bogus residue values);
3888 s = SINGLE_LUN (the device has only one
3889 Logical Unit);
59307852
HG
3890 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3891 commands, uas only);
b6089f19 3892 u = IGNORE_UAS (don't bind to the uas driver);
d4f373e5
AS
3893 w = NO_WP_DETECT (don't test whether the
3894 medium is write-protected).
3895 Example: quirks=0419:aaf5:rl,0421:0433:rc
3896
ac1667db
SB
3897 user_debug= [KNL,ARM]
3898 Format: <int>
3899 See arch/arm/Kconfig.debug help text.
3900 1 - undefined instruction events
3901 2 - system calls
3902 4 - invalid data aborts
3903 8 - SIGSEGV faults
3904 16 - SIGBUS faults
3905 Example: user_debug=31
3906
14315592
IC
3907 userpte=
3908 [X86] Flags controlling user PTE allocations.
3909
3910 nohigh = do not allocate PTE pages in
3911 HIGHMEM regardless of setting
3912 of CONFIG_HIGHPTE.
3913
6cececfc 3914 vdso= [X86,SH]
b0b49f26
AL
3915 On X86_32, this is an alias for vdso32=. Otherwise:
3916
3917 vdso=1: enable VDSO (the default)
e6e5494c
IM
3918 vdso=0: disable VDSO mapping
3919
b0b49f26
AL
3920 vdso32= [X86] Control the 32-bit vDSO
3921 vdso32=1: enable 32-bit VDSO
3922 vdso32=0 or vdso32=2: disable 32-bit VDSO
3923
3924 See the help text for CONFIG_COMPAT_VDSO for more
3925 details. If CONFIG_COMPAT_VDSO is set, the default is
3926 vdso32=0; otherwise, the default is vdso32=1.
3927
3928 For compatibility with older kernels, vdso32=2 is an
3929 alias for vdso32=0.
3930
3931 Try vdso32=0 if you encounter an error that says:
3932 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
af65d648 3933
d080d397
YI
3934 vector= [IA-64,SMP]
3935 vector=percpu: enable percpu vector domain
3936
1da177e4
LT
3937 video= [FB] Frame buffer configuration
3938 See Documentation/fb/modedb.txt.
3939
3afe6dab
AL
3940 video.brightness_switch_enabled= [0,1]
3941 If set to 1, on receiving an ACPI notify event
3942 generated by hotkey, video driver will adjust brightness
3943 level and then send out the event to user space through
3944 the allocated input device; If set to 0, video driver
3945 will only send out the event without touching backlight
3946 brightness level.
2843768b 3947 default: 1
3afe6dab 3948
81a054ce
PM
3949 virtio_mmio.device=
3950 [VMMIO] Memory mapped virtio (platform) device.
3951
3952 <size>@<baseaddr>:<irq>[:<id>]
3953 where:
3954 <size> := size (can use standard suffixes
3955 like K, M and G)
3956 <baseaddr> := physical base address
3957 <irq> := interrupt number (as passed to
3958 request_irq())
3959 <id> := (optional) platform device id
3960 example:
3961 virtio_mmio.device=1K@0x100b0000:48:7
3962
3963 Can be used multiple times for multiple devices.
3964
cd4f0ef7 3965 vga= [BOOT,X86-32] Select a particular video mode
954a8b81 3966 See Documentation/x86/boot.txt and
a9913044 3967 Documentation/svga.txt.
1da177e4
LT
3968 Use vga=ask for menu.
3969 This is actually a boot loader parameter; the value is
3970 passed to the kernel using a special protocol.
3971
a9913044 3972 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
3973 size of <nn>. This can be used to increase the
3974 minimum size (128MB on x86). It can also be used to
3975 decrease the size and leave more room for directly
3976 mapped kernel RAM.
3977
585c3047
PO
3978 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3979 Format: <command>
1da177e4 3980
585c3047
PO
3981 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3982 Format: <command>
3983
3984 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3985 Format: <command>
a9913044 3986
3ae36655
AL
3987 vsyscall= [X86-64]
3988 Controls the behavior of vsyscalls (i.e. calls to
3989 fixed addresses of 0xffffffffff600x00 from legacy
3990 code). Most statically-linked binaries and older
3991 versions of glibc use these calls. Because these
3992 functions are at fixed addresses, they make nice
3993 targets for exploits that can control RIP.
3994
2e57ae05
AL
3995 emulate [default] Vsyscalls turn into traps and are
3996 emulated reasonably safely.
3ae36655 3997
2e57ae05 3998 native Vsyscalls are native syscall instructions.
3ae36655
AL
3999 This is a little bit faster than trapping
4000 and makes a few dynamic recompilers work
4001 better than they would in emulation mode.
4002 It also makes exploits much easier to write.
4003
4004 none Vsyscalls don't work at all. This makes
4005 them quite hard to use for exploits but
4006 might break your system.
4007
3855ae1c
CL
4008 vt.color= [VT] Default text color.
4009 Format: 0xYX, X = foreground, Y = background.
4010 Default: 0x07 = light gray on black.
4011
9ea9a886
CL
4012 vt.cur_default= [VT] Default cursor shape.
4013 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4014 the parameters of the <Esc>[?A;B;Cc escape sequence;
4015 see VGA-softcursor.txt. Default: 2 = underline.
4016
0cb55ad2
RD
4017 vt.default_blu= [VT]
4018 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4019 Change the default blue palette of the console.
4020 This is a 16-member array composed of values
4021 ranging from 0-255.
4022
4023 vt.default_grn= [VT]
4024 Format: <green0>,<green1>,<green2>,...,<green15>
4025 Change the default green palette of the console.
4026 This is a 16-member array composed of values
4027 ranging from 0-255.
4028
4029 vt.default_red= [VT]
4030 Format: <red0>,<red1>,<red2>,...,<red15>
4031 Change the default red palette of the console.
4032 This is a 16-member array composed of values
4033 ranging from 0-255.
4034
4035 vt.default_utf8=
4036 [VT]
4037 Format=<0|1>
4038 Set system-wide default UTF-8 mode for all tty's.
4039 Default is 1, i.e. UTF-8 mode is enabled for all
4040 newly opened terminals.
4041
f6c06b68
MG
4042 vt.global_cursor_default=
4043 [VT]
4044 Format=<-1|0|1>
4045 Set system-wide default for whether a cursor
4046 is shown on new VTs. Default is -1,
4047 i.e. cursors will be created by default unless
4048 overridden by individual drivers. 0 will hide
4049 cursors, 1 will display them.
4050
3855ae1c
CL
4051 vt.italic= [VT] Default color for italic text; 0-15.
4052 Default: 2 = green.
4053
4054 vt.underline= [VT] Default color for underlined text; 0-15.
4055 Default: 3 = cyan.
4056
4724ba57
RD
4057 watchdog timers [HW,WDT] For information on watchdog timers,
4058 see Documentation/watchdog/watchdog-parameters.txt
4059 or other driver-specific files in the
4060 Documentation/watchdog/ directory.
1da177e4 4061
d55262c4
TH
4062 workqueue.disable_numa
4063 By default, all work items queued to unbound
4064 workqueues are affine to the NUMA nodes they're
4065 issued on, which results in better behavior in
4066 general. If NUMA affinity needs to be disabled for
4067 whatever reason, this option can be used. Note
4068 that this also can be controlled per-workqueue for
4069 workqueues visible under /sys/bus/workqueue/.
4070
cee22a15
VK
4071 workqueue.power_efficient
4072 Per-cpu workqueues are generally preferred because
4073 they show better performance thanks to cache
4074 locality; unfortunately, per-cpu workqueues tend to
4075 be more power hungry than unbound workqueues.
4076
4077 Enabling this makes the per-cpu workqueues which
4078 were observed to contribute significantly to power
4079 consumption unbound, leading to measurably lower
4080 power usage at the cost of small performance
4081 overhead.
4082
4083 The default value of this parameter is determined by
4084 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4085
0cb55ad2
RD
4086 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4087 default x2apic cluster mode on platforms
4088 supporting x2apic.
4089
712b6aa8
KS
4090 x86_intel_mid_timer= [X86-32,APBT]
4091 Choose timer option for x86 Intel MID platform.
bb24c471
JP
4092 Two valid options are apbt timer only and lapic timer
4093 plus one apbt timer for broadcast timer.
712b6aa8 4094 x86_intel_mid_timer=apbt_only | lapic_and_apbt
bb24c471 4095
c1c5413a
SS
4096 xen_emul_unplug= [HW,X86,XEN]
4097 Unplug Xen emulated devices
4098 Format: [unplug0,][unplug1]
4099 ide-disks -- unplug primary master IDE devices
4100 aux-ide-disks -- unplug non-primary-master IDE devices
4101 nics -- unplug network devices
4102 all -- unplug all emulated devices (NICs and IDE disks)
1dc7ce99
IC
4103 unnecessary -- unplugging emulated devices is
4104 unnecessary even if the host did not respond to
4105 the unplug protocol
c93a4dfb 4106 never -- do not unplug even if version check succeeds
c1c5413a 4107
15a3eac0
KRW
4108 xen_nopvspin [X86,XEN]
4109 Disables the ticketlock slowpath using Xen PV
4110 optimizations.
4111
8d693b91
KRW
4112 xen_nopv [X86]
4113 Disables the PV optimizations forcing the HVM guest to
4114 run as generic HVM guest with no PV drivers.
4115
1da177e4 4116 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
4117 Format:
4118 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 4119
a9913044 4120______________________________________________________________________
1da177e4
LT
4121
4122TODO:
4123
1da177e4 4124 Add more DRM drivers.