Finally, the [KMG] suffix is commonly described after a number of kernel
parameter values. These 'K', 'M', and 'G' letters represent the _binary_
multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
-bytes respectively. Such letter suffixes can also be entirely omitted::
+bytes respectively. Such letter suffixes can also be entirely omitted:
-
- acpi= [HW,ACPI,X86,ARM64]
- Advanced Configuration and Power Interface
- Format: { force | on | off | strict | noirq | rsdt |
- copy_dsdt }
- force -- enable ACPI if default was off
- on -- enable ACPI but allow fallback to DT [arm64]
- off -- disable ACPI if default was on
- noirq -- do not use ACPI for IRQ routing
- strict -- Be less tolerant of platforms that are not
- strictly ACPI specification compliant.
- rsdt -- prefer RSDT over (default) XSDT
- copy_dsdt -- copy DSDT to memory
- For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
- are available
-
- See also Documentation/power/runtime_pm.txt, pci=noacpi
-
- acpi_apic_instance= [ACPI, IOAPIC]
- Format: <int>
- 2: use 2nd APIC table, if available
- 1,0: use 1st APIC table
- default: 0
-
- acpi_backlight= [HW,ACPI]
- acpi_backlight=vendor
- acpi_backlight=video
- If set to vendor, prefer vendor specific driver
- (e.g. thinkpad_acpi, sony_acpi, etc.) instead
- of the ACPI video.ko driver.
-
- acpi_force_32bit_fadt_addr
- force FADT to use 32 bit addresses rather than the
- 64 bit X_* addresses. Some firmware have broken 64
- bit addresses for force ACPI ignore these and use
- the older legacy 32 bit addresses.
-
- acpica_no_return_repair [HW, ACPI]
- Disable AML predefined validation mechanism
- This mechanism can repair the evaluation result to make
- the return objects more ACPI specification compliant.
- This option is useful for developers to identify the
- root cause of an AML interpreter issue when the issue
- has something to do with the repair mechanism.
-
- acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
- acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
- Format: <int>
- CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
- debug output. Bits in debug_layer correspond to a
- _COMPONENT in an ACPI source file, e.g.,
- #define _COMPONENT ACPI_PCI_COMPONENT
- Bits in debug_level correspond to a level in
- ACPI_DEBUG_PRINT statements, e.g.,
- ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
- The debug_level mask defaults to "info". See
- Documentation/acpi/debug.txt for more information about
- debug layers and levels.
-
- Enable processor driver info messages:
- acpi.debug_layer=0x20000000
- Enable PCI/PCI interrupt routing info messages:
- acpi.debug_layer=0x400000
- Enable AML "Debug" output, i.e., stores to the Debug
- object while interpreting AML:
- acpi.debug_layer=0xffffffff acpi.debug_level=0x2
- Enable all messages related to ACPI hardware:
- acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
-
- Some values produce so much output that the system is
- unusable. The "log_buf_len" parameter may be useful
- if you need to capture more output.
-
- acpi_enforce_resources= [ACPI]
- { strict | lax | no }
- Check for resource conflicts between native drivers
- and ACPI OperationRegions (SystemIO and SystemMemory
- only). IO ports and memory declared in ACPI might be
- used by the ACPI subsystem in arbitrary AML code and
- can interfere with legacy drivers.
- strict (default): access to resources claimed by ACPI
- is denied; legacy drivers trying to access reserved
- resources will fail to bind to device using them.
- lax: access to resources claimed by ACPI is allowed;
- legacy drivers trying to access reserved resources
- will bind successfully but a warning message is logged.
- no: ACPI OperationRegions are not marked as reserved,
- no further checks are performed.
-
- acpi_force_table_verification [HW,ACPI]
- Enable table checksum verification during early stage.
- By default, this is disabled due to x86 early mapping
- size limitation.
-
- acpi_irq_balance [HW,ACPI]
- ACPI will balance active IRQs
- default in APIC mode
-
- acpi_irq_nobalance [HW,ACPI]
- ACPI will not move active IRQs (default)
- default in PIC mode
-
- acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
- Format: <irq>,<irq>...
-
- acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
- use by PCI
- Format: <irq>,<irq>...
-
- acpi_no_auto_serialize [HW,ACPI]
- Disable auto-serialization of AML methods
- AML control methods that contain the opcodes to create
- named objects will be marked as "Serialized" by the
- auto-serialization feature.
- This feature is enabled by default.
- This option allows to turn off the feature.
-
- acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
- kernels.
-
- acpi_no_static_ssdt [HW,ACPI]
- Disable installation of static SSDTs at early boot time
- By default, SSDTs contained in the RSDT/XSDT will be
- installed automatically and they will appear under
- /sys/firmware/acpi/tables.
- This option turns off this feature.
- Note that specifying this option does not affect
- dynamic table installation which will install SSDT
- tables to /sys/firmware/acpi/tables/dynamic.
-
- acpi_rsdp= [ACPI,EFI,KEXEC]
- Pass the RSDP address to the kernel, mostly used
- on machines running EFI runtime service to boot the
- second kernel for kdump.
-
- acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
- Format: To spoof as Windows 98: ="Microsoft Windows"
-
- acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
- of 2 which is mandated by ACPI 6) as the supported ACPI
- specification revision (when using this switch, it may
- be necessary to carry out a cold reboot _twice_ in a
- row to make it take effect on the platform firmware).
-
- acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
- acpi_osi="string1" # add string1
- acpi_osi="!string2" # remove string2
- acpi_osi=!* # remove all strings
- acpi_osi=! # disable all built-in OS vendor
- strings
- acpi_osi=!! # enable all built-in OS vendor
- strings
- acpi_osi= # disable all strings
-
- 'acpi_osi=!' can be used in combination with single or
- multiple 'acpi_osi="string1"' to support specific OS
- vendor string(s). Note that such command can only
- affect the default state of the OS vendor strings, thus
- it cannot affect the default state of the feature group
- strings and the current state of the OS vendor strings,
- specifying it multiple times through kernel command line
- is meaningless. This command is useful when one do not
- care about the state of the feature group strings which
- should be controlled by the OSPM.
- Examples:
- 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
- to 'acpi_osi="Windows 2000" acpi_osi=!', they all
- can make '_OSI("Windows 2000")' TRUE.
-
- 'acpi_osi=' cannot be used in combination with other
- 'acpi_osi=' command lines, the _OSI method will not
- exist in the ACPI namespace. NOTE that such command can
- only affect the _OSI support state, thus specifying it
- multiple times through kernel command line is also
- meaningless.
- Examples:
- 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
- FALSE.
-
- 'acpi_osi=!*' can be used in combination with single or
- multiple 'acpi_osi="string1"' to support specific
- string(s). Note that such command can affect the
- current state of both the OS vendor strings and the
- feature group strings, thus specifying it multiple times
- through kernel command line is meaningful. But it may
- still not able to affect the final state of a string if
- there are quirks related to this string. This command
- is useful when one want to control the state of the
- feature group strings to debug BIOS issues related to
- the OSPM features.
- Examples:
- 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
- '_OSI("Module Device")' FALSE.
- 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
- '_OSI("Module Device")' TRUE.
- 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
- equivalent to
- 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
- and
- 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
- they all will make '_OSI("Windows 2000")' TRUE.
-
- acpi_pm_good [X86]
- Override the pmtimer bug detection: force the kernel
- to assume that this machine's pmtimer latches its value
- and always returns good values.
-
- acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
- Format: { level | edge | high | low }
-
- acpi_skip_timer_override [HW,ACPI]
- Recognize and ignore IRQ0/pin2 Interrupt Override.
- For broken nForce2 BIOS resulting in XT-PIC timer.
-
- acpi_sleep= [HW,ACPI] Sleep options
- Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
- old_ordering, nonvs, sci_force_enable }
- See Documentation/power/video.txt for information on
- s3_bios and s3_mode.
- s3_beep is for debugging; it makes the PC's speaker beep
- as soon as the kernel's real-mode entry point is called.
- s4_nohwsig prevents ACPI hardware signature from being
- used during resume from hibernation.
- old_ordering causes the ACPI 1.0 ordering of the _PTS
- control method, with respect to putting devices into
- low power states, to be enforced (the ACPI 2.0 ordering
- of _PTS is used by default).
- nonvs prevents the kernel from saving/restoring the
- ACPI NVS memory during suspend/hibernation and resume.
- sci_force_enable causes the kernel to set SCI_EN directly
- on resume from S1/S3 (which is against the ACPI spec,
- but some broken systems don't work without it).
-
- acpi_use_timer_override [HW,ACPI]
- Use timer override. For some broken Nvidia NF5 boards
- that require a timer override, but don't have HPET
-
- add_efi_memmap [EFI; X86] Include EFI memory map in
- kernel's map of available physical RAM.
-
- agp= [AGP]
- { off | try_unsupported }
- off: disable AGP support
- try_unsupported: try to drive unsupported chipsets
- (may crash computer or cause data corruption)
-
- ALSA [HW,ALSA]
- See Documentation/sound/alsa/alsa-parameters.txt
-
- alignment= [KNL,ARM]
- Allow the default userspace alignment fault handler
- behaviour to be specified. Bit 0 enables warnings,
- bit 1 enables fixups, and bit 2 sends a segfault.
-
- align_va_addr= [X86-64]
- Align virtual addresses by clearing slice [14:12] when
- allocating a VMA at process creation time. This option
- gives you up to 3% performance improvement on AMD F15h
- machines (where it is enabled by default) for a
- CPU-intensive style benchmark, and it can vary highly in
- a microbenchmark depending on workload and compiler.
-
- 32: only for 32-bit processes
- 64: only for 64-bit processes
- on: enable for both 32- and 64-bit processes
- off: disable for both 32- and 64-bit processes
-
- alloc_snapshot [FTRACE]
- Allocate the ftrace snapshot buffer on boot up when the
- main buffer is allocated. This is handy if debugging
- and you need to use tracing_snapshot() on boot up, and
- do not want to use tracing_snapshot_alloc() as it needs
- to be done where GFP_KERNEL allocations are allowed.
-
- amd_iommu= [HW,X86-64]
- Pass parameters to the AMD IOMMU driver in the system.
- Possible values are:
- fullflush - enable flushing of IO/TLB entries when
- they are unmapped. Otherwise they are
- flushed before they will be reused, which
- is a lot of faster
- off - do not initialize any AMD IOMMU found in
- the system
- force_isolation - Force device isolation for all
- devices. The IOMMU driver is not
- allowed anymore to lift isolation
- requirements as needed. This option
- does not override iommu=pt
-
- amd_iommu_dump= [HW,X86-64]
- Enable AMD IOMMU driver option to dump the ACPI table
- for AMD IOMMU. With this option enabled, AMD IOMMU
- driver will print ACPI tables for AMD IOMMU during
- IOMMU initialization.
-
- amd_iommu_intr= [HW,X86-64]
- Specifies one of the following AMD IOMMU interrupt
- remapping modes:
- legacy - Use legacy interrupt remapping mode.
- vapic - Use virtual APIC mode, which allows IOMMU
- to inject interrupts directly into guest.
- This mode requires kvm-amd.avic=1.
- (Default when IOMMU HW support is present.)
-
- amijoy.map= [HW,JOY] Amiga joystick support
- Map of devices attached to JOY0DAT and JOY1DAT
- Format: <a>,<b>
- See also Documentation/input/joystick.txt
-
- analog.map= [HW,JOY] Analog joystick and gamepad support
- Specifies type or capabilities of an analog joystick
- connected to one of 16 gameports
- Format: <type1>,<type2>,..<type16>
-
- apc= [HW,SPARC]
- Power management functions (SPARCstation-4/5 + deriv.)
- Format: noidle
- Disable APC CPU standby support. SPARCstation-Fox does
- not play well with APC CPU idle - disable it if you have
- APC and your system crashes randomly.
-
- apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
- Change the output verbosity whilst booting
- Format: { quiet (default) | verbose | debug }
- Change the amount of debugging information output
- when initialising the APIC and IO-APIC components.
-
- apic_extnmi= [APIC,X86] External NMI delivery setting
- Format: { bsp (default) | all | none }
- bsp: External NMI is delivered only to CPU 0
- all: External NMIs are broadcast to all CPUs as a
- backup of CPU 0
- none: External NMI is masked for all CPUs. This is
- useful so that a dump capture kernel won't be
- shot down by NMI
-
- autoconf= [IPV6]
- See Documentation/networking/ipv6.txt.
-
- show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
- Limit apic dumping. The parameter defines the maximal
- number of local apics being dumped. Also it is possible
- to set it to "all" by meaning -- no limit here.
- Format: { 1 (default) | 2 | ... | all }.
- The parameter valid if only apic=debug or
- apic=verbose is specified.
- Example: apic=debug show_lapic=all
-
- apm= [APM] Advanced Power Management
- See header of arch/x86/kernel/apm_32.c.
-
- arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
- Format: <io>,<irq>,<nodeID>
-
- ataflop= [HW,M68k]
-
- atarimouse= [HW,MOUSE] Atari Mouse
-
- atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
- EzKey and similar keyboards
-
- atkbd.reset= [HW] Reset keyboard during initialization
-
- atkbd.set= [HW] Select keyboard code set
- Format: <int> (2 = AT (default), 3 = PS/2)
-
- atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
- keyboards
-
- atkbd.softraw= [HW] Choose between synthetic and real raw mode
- Format: <bool> (0 = real, 1 = synthetic (default))
-
- atkbd.softrepeat= [HW]
- Use software keyboard repeat
-
- audit= [KNL] Enable the audit sub-system
- Format: { "0" | "1" } (0 = disabled, 1 = enabled)
- 0 - kernel audit is disabled and can not be enabled
- until the next reboot
- unset - kernel audit is initialized but disabled and
- will be fully enabled by the userspace auditd.
- 1 - kernel audit is initialized and partially enabled,
- storing at most audit_backlog_limit messages in
- RAM until it is fully enabled by the userspace
- auditd.
- Default: unset
-
- audit_backlog_limit= [KNL] Set the audit queue size limit.
- Format: <int> (must be >=0)
- Default: 64
-
- bau= [X86_UV] Enable the BAU on SGI UV. The default
- behavior is to disable the BAU (i.e. bau=0).
- Format: { "0" | "1" }
- 0 - Disable the BAU.
- 1 - Enable the BAU.
- unset - Disable the BAU.
-
- baycom_epp= [HW,AX25]
- Format: <io>,<mode>
-
- baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
- Format: <io>,<mode>
- See header of drivers/net/hamradio/baycom_par.c.
-
- baycom_ser_fdx= [HW,AX25]
- BayCom Serial Port AX.25 Modem (Full Duplex Mode)
- Format: <io>,<irq>,<mode>[,<baud>]
- See header of drivers/net/hamradio/baycom_ser_fdx.c.
-
- baycom_ser_hdx= [HW,AX25]
- BayCom Serial Port AX.25 Modem (Half Duplex Mode)
- Format: <io>,<irq>,<mode>
- See header of drivers/net/hamradio/baycom_ser_hdx.c.
-
- blkdevparts= Manual partition parsing of block device(s) for
- embedded devices based on command line input.
- See Documentation/block/cmdline-partition.txt
-
- boot_delay= Milliseconds to delay each printk during boot.
- Values larger than 10 seconds (10000) are changed to
- no delay (0).
- Format: integer
-
- bootmem_debug [KNL] Enable bootmem allocator debug messages.
-
- bert_disable [ACPI]
- Disable BERT OS support on buggy BIOSes.
-
- bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
- bttv.radio= Most important insmod options are available as
- kernel args too.
- bttv.pll= See Documentation/video4linux/bttv/Insmod-options
- bttv.tuner=
-
- bulk_remove=off [PPC] This parameter disables the use of the pSeries
- firmware feature for flushing multiple hpte entries
- at a time.
-
- c101= [NET] Moxa C101 synchronous serial card
-
- cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
- Sometimes CPU hardware bugs make them report the cache
- size incorrectly. The kernel will attempt work arounds
- to fix known problems, but for some CPUs it is not
- possible to determine what the correct size should be.
- This option provides an override for these situations.
-
- ca_keys= [KEYS] This parameter identifies a specific key(s) on
- the system trusted keyring to be used for certificate
- trust validation.
- format: { id:<keyid> | builtin }
-
- cca= [MIPS] Override the kernel pages' cache coherency
- algorithm. Accepted values range from 0 to 7
- inclusive. See arch/mips/include/asm/pgtable-bits.h
- for platform specific values (SB1, Loongson3 and
- others).
-
- ccw_timeout_log [S390]
- See Documentation/s390/CommonIO for details.
-
- cgroup_disable= [KNL] Disable a particular controller
- Format: {name of the controller(s) to disable}
- The effects of cgroup_disable=foo are:
- - foo isn't auto-mounted if you mount all cgroups in
- a single hierarchy
- - foo isn't visible as an individually mountable
- subsystem
- {Currently only "memory" controller deal with this and
- cut the overhead, others just disable the usage. So
- only cgroup_disable=memory is actually worthy}
-
- cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1
- Format: { controller[,controller...] | "all" }
- Like cgroup_disable, but only applies to cgroup v1;
- the blacklisted controllers remain available in cgroup2.
-
- cgroup.memory= [KNL] Pass options to the cgroup memory controller.
- Format: <string>
- nosocket -- Disable socket memory accounting.
- nokmem -- Disable kernel memory accounting.
-
- checkreqprot [SELINUX] Set initial checkreqprot flag value.
- Format: { "0" | "1" }
- See security/selinux/Kconfig help text.
- 0 -- check protection applied by kernel (includes
- any implied execute protection).
- 1 -- check protection requested by application.
- Default value is set via a kernel config option.
- Value can be changed at runtime via
- /selinux/checkreqprot.
-
- cio_ignore= [S390]
- See Documentation/s390/CommonIO for details.
- clk_ignore_unused
- [CLK]
- Prevents the clock framework from automatically gating
- clocks that have not been explicitly enabled by a Linux
- device driver but are enabled in hardware at reset or
- by the bootloader/firmware. Note that this does not
- force such clocks to be always-on nor does it reserve
- those clocks in any way. This parameter is useful for
- debug and development, but should not be needed on a
- platform with proper driver support. For more
- information, see Documentation/clk.txt.
-
- clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
- [Deprecated]
- Forces specified clocksource (if available) to be used
- when calculating gettimeofday(). If specified
- clocksource is not available, it defaults to PIT.
- Format: { pit | tsc | cyclone | pmtmr }
-
- clocksource= Override the default clocksource
- Format: <string>
- Override the default clocksource and use the clocksource
- with the name specified.
- Some clocksource names to choose from, depending on
- the platform:
- [all] jiffies (this is the base, fallback clocksource)
- [ACPI] acpi_pm
- [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
- pxa_timer,timer3,32k_counter,timer0_1
- [AVR32] avr32
- [X86-32] pit,hpet,tsc;
- scx200_hrt on Geode; cyclone on IBM x440
- [MIPS] MIPS
- [PARISC] cr16
- [S390] tod
- [SH] SuperH
- [SPARC64] tick
- [X86-64] hpet,tsc
-
- clocksource.arm_arch_timer.evtstrm=
- [ARM,ARM64]
- Format: <bool>
- Enable/disable the eventstream feature of the ARM
- architected timer so that code using WFE-based polling
- loops can be debugged more effectively on production
- systems.
-
- clocksource.arm_arch_timer.fsl-a008585=
- [ARM64]
- Format: <bool>
- Enable/disable the workaround of Freescale/NXP
- erratum A-008585. This can be useful for KVM
- guests, if the guest device tree doesn't show the
- erratum. If unspecified, the workaround is
- enabled based on the device tree.
-
- clearcpuid=BITNUM [X86]
- Disable CPUID feature X for the kernel. See
- arch/x86/include/asm/cpufeatures.h for the valid bit
- numbers. Note the Linux specific bits are not necessarily
- stable over kernel options, but the vendor specific
- ones should be.
- Also note that user programs calling CPUID directly
- or using the feature without checking anything
- will still see it. This just prevents it from
- being used by the kernel or shown in /proc/cpuinfo.
- Also note the kernel might malfunction if you disable
- some critical bits.
-
- cma=nn[MG]@[start[MG][-end[MG]]]
- [ARM,X86,KNL]
- Sets the size of kernel global memory area for
- contiguous memory allocations and optionally the
- placement constraint by the physical address range of
- memory allocations. A value of 0 disables CMA
- altogether. For more information, see
- include/linux/dma-contiguous.h
-
- cmo_free_hint= [PPC] Format: { yes | no }
- Specify whether pages are marked as being inactive
- when they are freed. This is used in CMO environments
- to determine OS memory pressure for page stealing by
- a hypervisor.
- Default: yes
-
- coherent_pool=nn[KMG] [ARM,KNL]
- Sets the size of memory pool for coherent, atomic dma
- allocations, by default set to 256K.
-
- code_bytes [X86] How many bytes of object code to print
- in an oops report.
- Range: 0 - 8192
- Default: 64
-
- com20020= [HW,NET] ARCnet - COM20020 chipset
- Format:
- <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
-
- com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
- Format: <io>[,<irq>]
-
- com90xx= [HW,NET]
- ARCnet - COM90xx chipset (memory-mapped buffers)
- Format: <io>[,<irq>[,<memstart>]]
-
- condev= [HW,S390] console device
- conmode=
-
- console= [KNL] Output console device and options.
-
- tty<n> Use the virtual console device <n>.
-
- ttyS<n>[,options]
- ttyUSB0[,options]
- Use the specified serial port. The options are of
- the form "bbbbpnf", where "bbbb" is the baud rate,
- "p" is parity ("n", "o", or "e"), "n" is number of
- bits, and "f" is flow control ("r" for RTS or
- omit it). Default is "9600n8".
-
- See Documentation/admin-guide/serial-console.rst for more
- information. See
- Documentation/networking/netconsole.txt for an
- alternative.
-
- uart[8250],io,<addr>[,options]
- uart[8250],mmio,<addr>[,options]
- uart[8250],mmio16,<addr>[,options]
- uart[8250],mmio32,<addr>[,options]
- uart[8250],0x<addr>[,options]
- Start an early, polled-mode console on the 8250/16550
- UART at the specified I/O port or MMIO address,
- switching to the matching ttyS device later.
- MMIO inter-register address stride is either 8-bit
- (mmio), 16-bit (mmio16), or 32-bit (mmio32).
- If none of [io|mmio|mmio16|mmio32], <addr> is assumed
- to be equivalent to 'mmio'. 'options' are specified in
- the same format described for ttyS above; if unspecified,
- the h/w is not re-initialized.
-
- hvc<n> Use the hypervisor console device <n>. This is for
- both Xen and PowerPC hypervisors.
-
- If the device connected to the port is not a TTY but a braille
- device, prepend "brl," before the device type, for instance
- console=brl,ttyS0
- For now, only VisioBraille is supported.
-
- consoleblank= [KNL] The console blank (screen saver) timeout in
- seconds. Defaults to 10*60 = 10mins. A value of 0
- disables the blank timer.
-
- coredump_filter=
- [KNL] Change the default value for
- /proc/<pid>/coredump_filter.
- See also Documentation/filesystems/proc.txt.
-
- cpuidle.off=1 [CPU_IDLE]
- disable the cpuidle sub-system
-
- cpu_init_udelay=N
- [X86] Delay for N microsec between assert and de-assert
- of APIC INIT to start processors. This delay occurs
- on every CPU online, such as boot, and resume from suspend.
- Default: 10000
-
- cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
- Format:
- <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
-
- crashkernel=size[KMG][@offset[KMG]]
- [KNL] Using kexec, Linux can switch to a 'crash kernel'
- upon panic. This parameter reserves the physical
- memory region [offset, offset + size] for that kernel
- image. If '@offset' is omitted, then a suitable offset
- is selected automatically. Check
- Documentation/kdump/kdump.txt for further details.
-
- crashkernel=range1:size1[,range2:size2,...][@offset]
- [KNL] Same as above, but depends on the memory
- in the running system. The syntax of range is
- start-[end] where start and end are both
- a memory unit (amount[KMG]). See also
- Documentation/kdump/kdump.txt for an example.
-
- crashkernel=size[KMG],high
- [KNL, x86_64] range could be above 4G. Allow kernel
- to allocate physical memory region from top, so could
- be above 4G if system have more than 4G ram installed.
- Otherwise memory region will be allocated below 4G, if
- available.
- It will be ignored if crashkernel=X is specified.
- crashkernel=size[KMG],low
- [KNL, x86_64] range under 4G. When crashkernel=X,high
- is passed, kernel could allocate physical memory region
- above 4G, that cause second kernel crash on system
- that require some amount of low memory, e.g. swiotlb
- requires at least 64M+32K low memory, also enough extra
- low memory is needed to make sure DMA buffers for 32-bit
- devices won't run out. Kernel would try to allocate at
- at least 256M below 4G automatically.
- This one let user to specify own low range under 4G
- for second kernel instead.
- 0: to disable low allocation.
- It will be ignored when crashkernel=X,high is not used
- or memory reserved is below 4G.
-
- cryptomgr.notests
- [KNL] Disable crypto self-tests
-
- cs89x0_dma= [HW,NET]
- Format: <dma>
-
- cs89x0_media= [HW,NET]
- Format: { rj45 | aui | bnc }
-
- dasd= [HW,NET]
- See header of drivers/s390/block/dasd_devmap.c.
-
- db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
- (one device per port)
- Format: <port#>,<type>
- See also Documentation/input/joystick-parport.txt
-
- ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
- time. See Documentation/dynamic-debug-howto.txt for
- details. Deprecated, see dyndbg.
-
- debug [KNL] Enable kernel debugging (events log level).
-
- debug_locks_verbose=
- [KNL] verbose self-tests
- Format=<0|1>
- Print debugging info while doing the locking API
- self-tests.
- We default to 0 (no extra messages), setting it to
- 1 will print _a lot_ more information - normally
- only useful to kernel developers.
-
- debug_objects [KNL] Enable object debugging
-
- no_debug_objects
- [KNL] Disable object debugging
-
- debug_guardpage_minorder=
- [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
- parameter allows control of the order of pages that will
- be intentionally kept free (and hence protected) by the
- buddy allocator. Bigger value increase the probability
- of catching random memory corruption, but reduce the
- amount of memory for normal system use. The maximum
- possible value is MAX_ORDER/2. Setting this parameter
- to 1 or 2 should be enough to identify most random
- memory corruption problems caused by bugs in kernel or
- driver code when a CPU writes to (or reads from) a
- random memory location. Note that there exists a class
- of memory corruptions problems caused by buggy H/W or
- F/W or by drivers badly programing DMA (basically when
- memory is written at bus level and the CPU MMU is
- bypassed) which are not detectable by
- CONFIG_DEBUG_PAGEALLOC, hence this option will not help
- tracking down these problems.
-
- debug_pagealloc=
- [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
- parameter enables the feature at boot time. In
- default, it is disabled. We can avoid allocating huge
- chunk of memory for debug pagealloc if we don't enable
- it at boot time and the system will work mostly same
- with the kernel built without CONFIG_DEBUG_PAGEALLOC.
- on: enable the feature
-
- debugpat [X86] Enable PAT debugging
-
- decnet.addr= [HW,NET]
- Format: <area>[,<node>]
- See also Documentation/networking/decnet.txt.
-
- default_hugepagesz=
- [same as hugepagesz=] The size of the default
- HugeTLB page size. This is the size represented by
- the legacy /proc/ hugepages APIs, used for SHM, and
- default size when mounting hugetlbfs filesystems.
- Defaults to the default architecture's huge page size
- if not specified.
-
- dhash_entries= [KNL]
- Set number of hash buckets for dentry cache.
-
- disable_1tb_segments [PPC]
- Disables the use of 1TB hash page table segments. This
- causes the kernel to fall back to 256MB segments which
- can be useful when debugging issues that require an SLB
- miss to occur.
-
- disable= [IPV6]
- See Documentation/networking/ipv6.txt.
-
- disable_radix [PPC]
- Disable RADIX MMU mode on POWER9
-
- disable_cpu_apicid= [X86,APIC,SMP]
- Format: <int>
- The number of initial APIC ID for the
- corresponding CPU to be disabled at boot,
- mostly used for the kdump 2nd kernel to
- disable BSP to wake up multiple CPUs without
- causing system reset or hang due to sending
- INIT from AP to BSP.
-
- disable_ddw [PPC/PSERIES]
- Disable Dynamic DMA Window support. Use this if
- to workaround buggy firmware.
-
- disable_ipv6= [IPV6]
- See Documentation/networking/ipv6.txt.
-
- disable_mtrr_cleanup [X86]
- The kernel tries to adjust MTRR layout from continuous
- to discrete, to make X server driver able to add WB
- entry later. This parameter disables that.
-
- disable_mtrr_trim [X86, Intel and AMD only]
- By default the kernel will trim any uncacheable
- memory out of your available memory pool based on
- MTRR settings. This parameter disables that behavior,
- possibly causing your machine to run very slowly.
-
- disable_timer_pin_1 [X86]
- Disable PIN 1 of APIC timer
- Can be useful to work around chipset bugs.
-
- dis_ucode_ldr [X86] Disable the microcode loader.
-
- dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
- this option disables the debugging code at boot.
-
- dma_debug_entries=<number>
- This option allows to tune the number of preallocated
- entries for DMA-API debugging code. One entry is
- required per DMA-API allocation. Use this if the
- DMA-API debugging code disables itself because the
- architectural default is too low.
-
- dma_debug_driver=<driver_name>
- With this option the DMA-API debugging driver
- filter feature can be enabled at boot time. Just
- pass the driver to filter for as the parameter.
- The filter can be disabled or changed to another
- driver later using sysfs.
-
- drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
- Broken monitors, graphic adapters, KVMs and EDIDless
- panels may send no or incorrect EDID data sets.
- This parameter allows to specify an EDID data sets
- in the /lib/firmware directory that are used instead.
- Generic built-in EDID data sets are used, if one of
- edid/1024x768.bin, edid/1280x1024.bin,
- edid/1680x1050.bin, or edid/1920x1080.bin is given
- and no file with the same name exists. Details and
- instructions how to build your own EDID data are
- available in Documentation/EDID/HOWTO.txt. An EDID
- data set will only be used for a particular connector,
- if its name and a colon are prepended to the EDID
- name. Each connector may use a unique EDID data
- set by separating the files with a comma. An EDID
- data set with no connector name will be used for
- any connectors not explicitly specified.
-
- dscc4.setup= [NET]
-
- dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
- module.dyndbg[="val"]
- Enable debug messages at boot time. See
- Documentation/dynamic-debug-howto.txt for details.
-
- nompx [X86] Disables Intel Memory Protection Extensions.
- See Documentation/x86/intel_mpx.txt for more
- information about the feature.
-
- nopku [X86] Disable Memory Protection Keys CPU feature found
- in some Intel CPUs.
-
- eagerfpu= [X86]
- on enable eager fpu restore
- off disable eager fpu restore
- auto selects the default scheme, which automatically
- enables eagerfpu restore for xsaveopt.
-
- module.async_probe [KNL]
- Enable asynchronous probe on this module.
-
- early_ioremap_debug [KNL]
- Enable debug messages in early_ioremap support. This
- is useful for tracking down temporary early mappings
- which are not unmapped.
-
- earlycon= [KNL] Output early console device and options.
-
- When used with no options, the early console is
- determined by the stdout-path property in device
- tree's chosen node.
-
- cdns,<addr>[,options]
- Start an early, polled-mode console on a Cadence
- (xuartps) serial port at the specified address. Only
- supported option is baud rate. If baud rate is not
- specified, the serial port must already be setup and
- configured.
-
- uart[8250],io,<addr>[,options]
- uart[8250],mmio,<addr>[,options]
- uart[8250],mmio32,<addr>[,options]
- uart[8250],mmio32be,<addr>[,options]
- uart[8250],0x<addr>[,options]
- Start an early, polled-mode console on the 8250/16550
- UART at the specified I/O port or MMIO address.
- MMIO inter-register address stride is either 8-bit
- (mmio) or 32-bit (mmio32 or mmio32be).
- If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
- to be equivalent to 'mmio'. 'options' are specified
- in the same format described for "console=ttyS<n>"; if
- unspecified, the h/w is not initialized.
-
- pl011,<addr>
- pl011,mmio32,<addr>
- Start an early, polled-mode console on a pl011 serial
- port at the specified address. The pl011 serial port
- must already be setup and configured. Options are not
- yet supported. If 'mmio32' is specified, then only
- the driver will use only 32-bit accessors to read/write
- the device registers.
-
- meson,<addr>
- Start an early, polled-mode console on a meson serial
- port at the specified address. The serial port must
- already be setup and configured. Options are not yet
- supported.
-
- msm_serial,<addr>
- Start an early, polled-mode console on an msm serial
- port at the specified address. The serial port
- must already be setup and configured. Options are not
- yet supported.
-
- msm_serial_dm,<addr>
- Start an early, polled-mode console on an msm serial
- dm port at the specified address. The serial port
- must already be setup and configured. Options are not
- yet supported.
-
- smh Use ARM semihosting calls for early console.
-
- s3c2410,<addr>
- s3c2412,<addr>
- s3c2440,<addr>
- s3c6400,<addr>
- s5pv210,<addr>
- exynos4210,<addr>
- Use early console provided by serial driver available
- on Samsung SoCs, requires selecting proper type and
- a correct base address of the selected UART port. The
- serial port must already be setup and configured.
- Options are not yet supported.
-
- lpuart,<addr>
- lpuart32,<addr>
- Use early console provided by Freescale LP UART driver
- found on Freescale Vybrid and QorIQ LS1021A processors.
- A valid base address must be provided, and the serial
- port must already be setup and configured.
-
- armada3700_uart,<addr>
- Start an early, polled-mode console on the
- Armada 3700 serial port at the specified
- address. The serial port must already be setup
- and configured. Options are not yet supported.
-
- earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
- earlyprintk=vga
- earlyprintk=efi
- earlyprintk=xen
- earlyprintk=serial[,ttySn[,baudrate]]
- earlyprintk=serial[,0x...[,baudrate]]
- earlyprintk=ttySn[,baudrate]
- earlyprintk=dbgp[debugController#]
- earlyprintk=pciserial,bus:device.function[,baudrate]
-
- earlyprintk is useful when the kernel crashes before
- the normal console is initialized. It is not enabled by
- default because it has some cosmetic problems.
-
- Append ",keep" to not disable it when the real console
- takes over.
-
- Only one of vga, efi, serial, or usb debug port can
- be used at a time.
-
- Currently only ttyS0 and ttyS1 may be specified by
- name. Other I/O ports may be explicitly specified
- on some architectures (x86 and arm at least) by
- replacing ttySn with an I/O port address, like this:
- earlyprintk=serial,0x1008,115200
- You can find the port for a given device in
- /proc/tty/driver/serial:
- 2: uart:ST16650V2 port:00001008 irq:18 ...
-
- Interaction with the standard serial driver is not
- very good.
-
- The VGA and EFI output is eventually overwritten by
- the real console.
-
- The xen output can only be used by Xen PV guests.
-
- edac_report= [HW,EDAC] Control how to report EDAC event
- Format: {"on" | "off" | "force"}
- on: enable EDAC to report H/W event. May be overridden
- by other higher priority error reporting module.
- off: disable H/W event reporting through EDAC.
- force: enforce the use of EDAC to report H/W event.
- default: on.
-
- ekgdboc= [X86,KGDB] Allow early kernel console debugging
- ekgdboc=kbd
-
- This is designed to be used in conjunction with
- the boot argument: earlyprintk=vga
-
- edd= [EDD]
- Format: {"off" | "on" | "skip[mbr]"}
-
- efi= [EFI]
- Format: { "old_map", "nochunk", "noruntime", "debug" }
- old_map [X86-64]: switch to the old ioremap-based EFI
- runtime services mapping. 32-bit still uses this one by
- default.
- nochunk: disable reading files in "chunks" in the EFI
- boot stub, as chunking can cause problems with some
- firmware implementations.
- noruntime : disable EFI runtime services support
- debug: enable misc debug output
-
- efi_no_storage_paranoia [EFI; X86]
- Using this parameter you can use more than 50% of
- your efi variable storage. Use this parameter only if
- you are really sure that your UEFI does sane gc and
- fulfills the spec otherwise your board may brick.
-
- efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
- Add arbitrary attribute to specific memory range by
- updating original EFI memory map.
- Region of memory which aa attribute is added to is
- from ss to ss+nn.
- If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
- is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
- attribute is added to range 0x100000000-0x180000000 and
- 0x10a0000000-0x1120000000.
-
- Using this parameter you can do debugging of EFI memmap
- related feature. For example, you can do debugging of
- Address Range Mirroring feature even if your box
- doesn't support it.
-
- efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
- that is to be dynamically loaded by Linux. If there are
- multiple variables with the same name but with different
- vendor GUIDs, all of them will be loaded. See
- Documentation/acpi/ssdt-overlays.txt for details.
-
-
- eisa_irq_edge= [PARISC,HW]
- See header of drivers/parisc/eisa.c.
-
- elanfreq= [X86-32]
- See comment before function elanfreq_setup() in
- arch/x86/kernel/cpu/cpufreq/elanfreq.c.
-
- elevator= [IOSCHED]
- Format: {"cfq" | "deadline" | "noop"}
- See Documentation/block/cfq-iosched.txt and
- Documentation/block/deadline-iosched.txt for details.
-
- elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
- Specifies physical address of start of kernel core
- image elf header and optionally the size. Generally
- kexec loader will pass this option to capture kernel.
- See Documentation/kdump/kdump.txt for details.
-
- enable_mtrr_cleanup [X86]
- The kernel tries to adjust MTRR layout from continuous
- to discrete, to make X server driver able to add WB
- entry later. This parameter enables that.
-
- enable_timer_pin_1 [X86]
- Enable PIN 1 of APIC timer
- Can be useful to work around chipset bugs
- (in particular on some ATI chipsets).
- The kernel tries to set a reasonable default.
-
- enforcing [SELINUX] Set initial enforcing status.
- Format: {"0" | "1"}
- See security/selinux/Kconfig help text.
- 0 -- permissive (log only, no denials).
- 1 -- enforcing (deny and log).
- Default value is 0.
- Value can be changed at runtime via /selinux/enforce.
-
- erst_disable [ACPI]
- Disable Error Record Serialization Table (ERST)
- support.
-
- ether= [HW,NET] Ethernet cards parameters
- This option is obsoleted by the "netdev=" option, which
- has equivalent usage. See its documentation for details.
-
- evm= [EVM]
- Format: { "fix" }
- Permit 'security.evm' to be updated regardless of
- current integrity status.
-
- failslab=
- fail_page_alloc=
- fail_make_request=[KNL]
- General fault injection mechanism.
- Format: <interval>,<probability>,<space>,<times>
- See also Documentation/fault-injection/.
-
- floppy= [HW]
- See Documentation/blockdev/floppy.txt.
-
- force_pal_cache_flush
- [IA-64] Avoid check_sal_cache_flush which may hang on
- buggy SAL_CACHE_FLUSH implementations. Using this
- parameter will force ia64_sal_cache_flush to call
- ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
-
- forcepae [X86-32]
- Forcefully enable Physical Address Extension (PAE).
- Many Pentium M systems disable PAE but may have a
- functionally usable PAE implementation.
- Warning: use of this parameter will taint the kernel
- and may cause unknown problems.
-
- ftrace=[tracer]
- [FTRACE] will set and start the specified tracer
- as early as possible in order to facilitate early
- boot debugging.
-
- ftrace_dump_on_oops[=orig_cpu]
- [FTRACE] will dump the trace buffers on oops.
- If no parameter is passed, ftrace will dump
- buffers of all CPUs, but if you pass orig_cpu, it will
- dump only the buffer of the CPU that triggered the
- oops.
-
- ftrace_filter=[function-list]
- [FTRACE] Limit the functions traced by the function
- tracer at boot up. function-list is a comma separated
- list of functions. This list can be changed at run
- time by the set_ftrace_filter file in the debugfs
- tracing directory.
-
- ftrace_notrace=[function-list]
- [FTRACE] Do not trace the functions specified in
- function-list. This list can be changed at run time
- by the set_ftrace_notrace file in the debugfs
- tracing directory.
-
- ftrace_graph_filter=[function-list]
- [FTRACE] Limit the top level callers functions traced
- by the function graph tracer at boot up.
- function-list is a comma separated list of functions
- that can be changed at run time by the
- set_graph_function file in the debugfs tracing directory.
-
- ftrace_graph_notrace=[function-list]
- [FTRACE] Do not trace from the functions specified in
- function-list. This list is a comma separated list of
- functions that can be changed at run time by the
- set_graph_notrace file in the debugfs tracing directory.
-
- gamecon.map[2|3]=
- [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
- support via parallel port (up to 5 devices per port)
- Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
- See also Documentation/input/joystick-parport.txt
-
- gamma= [HW,DRM]
-
- gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
- Format: off | on
- default: on
-
- gcov_persist= [GCOV] When non-zero (default), profiling data for
- kernel modules is saved and remains accessible via
- debugfs, even when the module is unloaded/reloaded.
- When zero, profiling data is discarded and associated
- debugfs files are removed at module unload time.
-
- gpt [EFI] Forces disk with valid GPT signature but
- invalid Protective MBR to be treated as GPT. If the
- primary GPT is corrupted, it enables the backup/alternate
- GPT to be used instead.
-
- grcan.enable0= [HW] Configuration of physical interface 0. Determines
- the "Enable 0" bit of the configuration register.
- Format: 0 | 1
- Default: 0
- grcan.enable1= [HW] Configuration of physical interface 1. Determines
- the "Enable 0" bit of the configuration register.
- Format: 0 | 1
- Default: 0
- grcan.select= [HW] Select which physical interface to use.
- Format: 0 | 1
- Default: 0
- grcan.txsize= [HW] Sets the size of the tx buffer.
- Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
- Default: 1024
- grcan.rxsize= [HW] Sets the size of the rx buffer.
- Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
- Default: 1024
-
- gpio-mockup.gpio_mockup_ranges
- [HW] Sets the ranges of gpiochip of for this device.
- Format: <start1>,<end1>,<start2>,<end2>...
-
- hardlockup_all_cpu_backtrace=
- [KNL] Should the hard-lockup detector generate
- backtraces on all cpus.
- Format: <integer>
-
- hashdist= [KNL,NUMA] Large hashes allocated during boot
- are distributed across NUMA nodes. Defaults on
- for 64-bit NUMA, off otherwise.
- Format: 0 | 1 (for off | on)
-
- hcl= [IA-64] SGI's Hardware Graph compatibility layer
-
- hd= [EIDE] (E)IDE hard drive subsystem geometry
- Format: <cyl>,<head>,<sect>
-
- hest_disable [ACPI]
- Disable Hardware Error Source Table (HEST) support;
- corresponding firmware-first mode error processing
- logic will be disabled.
-
- highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
- size of <nn>. This works even on boxes that have no
- highmem otherwise. This also works to reduce highmem
- size on bigger boxes.
-
- highres= [KNL] Enable/disable high resolution timer mode.
- Valid parameters: "on", "off"
- Default: "on"
-
- hisax= [HW,ISDN]
- See Documentation/isdn/README.HiSax.
-
- hlt [BUGS=ARM,SH]
-
- hpet= [X86-32,HPET] option to control HPET usage
- Format: { enable (default) | disable | force |
- verbose }
- disable: disable HPET and use PIT instead
- force: allow force enabled of undocumented chips (ICH4,
- VIA, nVidia)
- verbose: show contents of HPET registers during setup
-
- hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
- registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
-
- hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
- hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
- On x86-64 and powerpc, this option can be specified
- multiple times interleaved with hugepages= to reserve
- huge pages of different sizes. Valid pages sizes on
- x86-64 are 2M (when the CPU supports "pse") and 1G
- (when the CPU supports the "pdpe1gb" cpuinfo flag).
-
- hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
- terminal devices. Valid values: 0..8
- hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
- If specified, z/VM IUCV HVC accepts connections
- from listed z/VM user IDs only.
-
- hwthread_map= [METAG] Comma-separated list of Linux cpu id to
- hardware thread id mappings.
- Format: <cpu>:<hwthread>
-
- keep_bootcon [KNL]
- Do not unregister boot console at start. This is only
- useful for debugging when something happens in the window
- between unregistering the boot console and initializing
- the real console.
-
- i2c_bus= [HW] Override the default board specific I2C bus speed
- or register an additional I2C bus that is not
- registered from board initialization code.
- Format:
- <bus_id>,<clkrate>
-
- i8042.debug [HW] Toggle i8042 debug mode
- i8042.unmask_kbd_data
- [HW] Enable printing of interrupt data from the KBD port
- (disabled by default, and as a pre-condition
- requires that i8042.debug=1 be enabled)
- i8042.direct [HW] Put keyboard port into non-translated mode
- i8042.dumbkbd [HW] Pretend that controller can only read data from
- keyboard and cannot control its state
- (Don't attempt to blink the leds)
- i8042.noaux [HW] Don't check for auxiliary (== mouse) port
- i8042.nokbd [HW] Don't check/create keyboard port
- i8042.noloop [HW] Disable the AUX Loopback command while probing
- for the AUX port
- i8042.nomux [HW] Don't check presence of an active multiplexing
- controller
- i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
- controllers
- i8042.notimeout [HW] Ignore timeout condition signalled by controller
- i8042.reset [HW] Reset the controller during init, cleanup and
- suspend-to-ram transitions, only during s2r
- transitions, or never reset
- Format: { 1 | Y | y | 0 | N | n }
- 1, Y, y: always reset controller
- 0, N, n: don't ever reset controller
- Default: only on s2r transitions on x86; most other
- architectures force reset to be always executed
- i8042.unlock [HW] Unlock (ignore) the keylock
- i8042.kbdreset [HW] Reset device connected to KBD port
-
- i810= [HW,DRM]
-
- i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
- indicates that the driver is running on unsupported
- hardware.
- i8k.force [HW] Activate i8k driver even if SMM BIOS signature
- does not match list of supported models.
- i8k.power_status
- [HW] Report power status in /proc/i8k
- (disabled by default)
- i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
- capability is set.
-
- i915.invert_brightness=
- [DRM] Invert the sense of the variable that is used to
- set the brightness of the panel backlight. Normally a
- brightness value of 0 indicates backlight switched off,
- and the maximum of the brightness value sets the backlight
- to maximum brightness. If this parameter is set to 0
- (default) and the machine requires it, or this parameter
- is set to 1, a brightness value of 0 sets the backlight
- to maximum brightness, and the maximum of the brightness
- value switches the backlight off.
- -1 -- never invert brightness
- 0 -- machine default
- 1 -- force brightness inversion
-
- icn= [HW,ISDN]
- Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
-
- ide-core.nodma= [HW] (E)IDE subsystem
- Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
- .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
- .cdrom .chs .ignore_cable are additional options
- See Documentation/ide/ide.txt.
-
- ide-generic.probe-mask= [HW] (E)IDE subsystem
- Format: <int>
- Probe mask for legacy ISA IDE ports. Depending on
- platform up to 6 ports are supported, enabled by
- setting corresponding bits in the mask to 1. The
- default value is 0x0, which has a special meaning.
- On systems that have PCI, it triggers scanning the
- PCI bus for the first and the second port, which
- are then probed. On systems without PCI the value
- of 0x0 enables probing the two first ports as if it
- was 0x3.
-
- ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
- Claim all unknown PCI IDE storage controllers.
-
- idle= [X86]
- Format: idle=poll, idle=halt, idle=nomwait
- Poll forces a polling idle loop that can slightly
- improve the performance of waking up a idle CPU, but
- will use a lot of power and make the system run hot.
- Not recommended.
- idle=halt: Halt is forced to be used for CPU idle.
- In such case C2/C3 won't be used again.
- idle=nomwait: Disable mwait for CPU C-states
-
- ieee754= [MIPS] Select IEEE Std 754 conformance mode
- Format: { strict | legacy | 2008 | relaxed }
- Default: strict
-
- Choose which programs will be accepted for execution
- based on the IEEE 754 NaN encoding(s) supported by
- the FPU and the NaN encoding requested with the value
- of an ELF file header flag individually set by each
- binary. Hardware implementations are permitted to
- support either or both of the legacy and the 2008 NaN
- encoding mode.
-
- Available settings are as follows:
- strict accept binaries that request a NaN encoding
- supported by the FPU
- legacy only accept legacy-NaN binaries, if supported
- by the FPU
- 2008 only accept 2008-NaN binaries, if supported
- by the FPU
- relaxed accept any binaries regardless of whether
- supported by the FPU
-
- The FPU emulator is always able to support both NaN
- encodings, so if no FPU hardware is present or it has
- been disabled with 'nofpu', then the settings of
- 'legacy' and '2008' strap the emulator accordingly,
- 'relaxed' straps the emulator for both legacy-NaN and
- 2008-NaN, whereas 'strict' enables legacy-NaN only on
- legacy processors and both NaN encodings on MIPS32 or
- MIPS64 CPUs.
-
- The setting for ABS.fmt/NEG.fmt instruction execution
- mode generally follows that for the NaN encoding,
- except where unsupported by hardware.
-
- ignore_loglevel [KNL]
- Ignore loglevel setting - this will print /all/
- kernel messages to the console. Useful for debugging.
- We also add it as printk module parameter, so users
- could change it dynamically, usually by
- /sys/module/printk/parameters/ignore_loglevel.
-
- ignore_rlimit_data
- Ignore RLIMIT_DATA setting for data mappings,
- print warning at first misuse. Can be changed via
- /sys/module/kernel/parameters/ignore_rlimit_data.
-
- ihash_entries= [KNL]
- Set number of hash buckets for inode cache.
-
- ima_appraise= [IMA] appraise integrity measurements
- Format: { "off" | "enforce" | "fix" | "log" }
- default: "enforce"
-
- ima_appraise_tcb [IMA]
- The builtin appraise policy appraises all files
- owned by uid=0.
-
- ima_hash= [IMA]
- Format: { md5 | sha1 | rmd160 | sha256 | sha384
- | sha512 | ... }
- default: "sha1"
-
- The list of supported hash algorithms is defined
- in crypto/hash_info.h.
-
- ima_policy= [IMA]
- The builtin measurement policy to load during IMA
- setup. Specyfing "tcb" as the value, measures all
- programs exec'd, files mmap'd for exec, and all files
- opened with the read mode bit set by either the
- effective uid (euid=0) or uid=0.
- Format: "tcb"
-
- ima_tcb [IMA] Deprecated. Use ima_policy= instead.
- Load a policy which meets the needs of the Trusted
- Computing Base. This means IMA will measure all
- programs exec'd, files mmap'd for exec, and all files
- opened for read by uid=0.
-
- ima_template= [IMA]
- Select one of defined IMA measurements template formats.
- Formats: { "ima" | "ima-ng" | "ima-sig" }
- Default: "ima-ng"
-
- ima_template_fmt=
- [IMA] Define a custom template format.
- Format: { "field1|...|fieldN" }
-
- ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
- Format: <min_file_size>
- Set the minimal file size for using asynchronous hash.
- If left unspecified, ahash usage is disabled.
-
- ahash performance varies for different data sizes on
- different crypto accelerators. This option can be used
- to achieve the best performance for a particular HW.
-
- ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
- Format: <bufsize>
- Set hashing buffer size. Default: 4k.
-
- ahash performance varies for different chunk sizes on
- different crypto accelerators. This option can be used
- to achieve best performance for particular HW.
-
- init= [KNL]
- Format: <full_path>
- Run specified binary instead of /sbin/init as init
- process.
-
- initcall_debug [KNL] Trace initcalls as they are executed. Useful
- for working out where the kernel is dying during
- startup.
-
- initcall_blacklist= [KNL] Do not execute a comma-separated list of
- initcall functions. Useful for debugging built-in
- modules and initcalls.
-
- initrd= [BOOT] Specify the location of the initial ramdisk
-
- init_pkru= [x86] Specify the default memory protection keys rights
- register contents for all processes. 0x55555554 by
- default (disallow access to all but pkey 0). Can
- override in debugfs after boot.
-
- inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
- Format: <irq>
-
- int_pln_enable [x86] Enable power limit notification interrupt
-
- integrity_audit=[IMA]
- Format: { "0" | "1" }
- 0 -- basic integrity auditing messages. (Default)
- 1 -- additional integrity auditing messages.
-
- intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
- on
- Enable intel iommu driver.
- off
- Disable intel iommu driver.
- igfx_off [Default Off]
- By default, gfx is mapped as normal device. If a gfx
- device has a dedicated DMAR unit, the DMAR unit is
- bypassed by not enabling DMAR with this option. In
- this case, gfx device will use physical address for
- DMA.
- forcedac [x86_64]
- With this option iommu will not optimize to look
- for io virtual address below 32-bit forcing dual
- address cycle on pci bus for cards supporting greater
- than 32-bit addressing. The default is to look
- for translation below 32-bit and if not available
- then look in the higher range.
- strict [Default Off]
- With this option on every unmap_single operation will
- result in a hardware IOTLB flush operation as opposed
- to batching them for performance.
- sp_off [Default Off]
- By default, super page will be supported if Intel IOMMU
- has the capability. With this option, super page will
- not be supported.
- ecs_off [Default Off]
- By default, extended context tables will be supported if
- the hardware advertises that it has support both for the
- extended tables themselves, and also PASID support. With
- this option set, extended tables will not be used even
- on hardware which claims to support them.
-
- intel_idle.max_cstate= [KNL,HW,ACPI,X86]
- 0 disables intel_idle and fall back on acpi_idle.
- 1 to 9 specify maximum depth of C-state.
-
- intel_pstate= [X86]
- disable
- Do not enable intel_pstate as the default
- scaling driver for the supported processors
- force
- Enable intel_pstate on systems that prohibit it by default
- in favor of acpi-cpufreq. Forcing the intel_pstate driver
- instead of acpi-cpufreq may disable platform features, such
- as thermal controls and power capping, that rely on ACPI
- P-States information being indicated to OSPM and therefore
- should be used with caution. This option does not work with
- processors that aren't supported by the intel_pstate driver
- or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
- no_hwp
- Do not enable hardware P state control (HWP)
- if available.
- hwp_only
- Only load intel_pstate on systems which support
- hardware P state control (HWP) if available.
- support_acpi_ppc
- Enforce ACPI _PPC performance limits. If the Fixed ACPI
- Description Table, specifies preferred power management
- profile as "Enterprise Server" or "Performance Server",
- then this feature is turned on by default.
-
- intremap= [X86-64, Intel-IOMMU]
- on enable Interrupt Remapping (default)
- off disable Interrupt Remapping
- nosid disable Source ID checking
- no_x2apic_optout
- BIOS x2APIC opt-out request will be ignored
- nopost disable Interrupt Posting
-
- iomem= Disable strict checking of access to MMIO memory
- strict regions from userspace.
- relaxed
-
- iommu= [x86]
- off
- force
- noforce
- biomerge
- panic
- nopanic
- merge
- nomerge
- forcesac
- soft
- pt [x86, IA-64]
- nobypass [PPC/POWERNV]
- Disable IOMMU bypass, using IOMMU for PCI devices.
-
-
- io7= [HW] IO7 for Marvel based alpha systems
- See comment before marvel_specify_io7 in
- arch/alpha/kernel/core_marvel.c.
-
- io_delay= [X86] I/O delay method
- 0x80
- Standard port 0x80 based delay
- 0xed
- Alternate port 0xed based delay (needed on some systems)
- udelay
- Simple two microseconds delay
- none
- No delay
-
- ip= [IP_PNP]
- See Documentation/filesystems/nfs/nfsroot.txt.
-
- irqaffinity= [SMP] Set the default irq affinity mask
- The argument is a cpu list, as described above.
-
- irqfixup [HW]
- When an interrupt is not handled search all handlers
- for it. Intended to get systems with badly broken
- firmware running.
-
- irqpoll [HW]
- When an interrupt is not handled search all handlers
- for it. Also check all handlers each timer
- interrupt. Intended to get systems with badly broken
- firmware running.
-
- isapnp= [ISAPNP]
- Format: <RDP>,<reset>,<pci_scan>,<verbosity>
-
- isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
- The argument is a cpu list, as described above.
-
- This option can be used to specify one or more CPUs
- to isolate from the general SMP balancing and scheduling
- algorithms. You can move a process onto or off an
- "isolated" CPU via the CPU affinity syscalls or cpuset.
- <cpu number> begins at 0 and the maximum value is
- "number of CPUs in system - 1".
-
- This option is the preferred way to isolate CPUs. The
- alternative -- manually setting the CPU mask of all
- tasks in the system -- can cause problems and
- suboptimal load balancer performance.
-
- iucv= [HW,NET]
-
- ivrs_ioapic [HW,X86_64]
- Provide an override to the IOAPIC-ID<->DEVICE-ID
- mapping provided in the IVRS ACPI table. For
- example, to map IOAPIC-ID decimal 10 to
- PCI device 00:14.0 write the parameter as:
- ivrs_ioapic[10]=00:14.0
-
- ivrs_hpet [HW,X86_64]
- Provide an override to the HPET-ID<->DEVICE-ID
- mapping provided in the IVRS ACPI table. For
- example, to map HPET-ID decimal 0 to
- PCI device 00:14.0 write the parameter as:
- ivrs_hpet[0]=00:14.0
-
- ivrs_acpihid [HW,X86_64]
- Provide an override to the ACPI-HID:UID<->DEVICE-ID
- mapping provided in the IVRS ACPI table. For
- example, to map UART-HID:UID AMD0020:0 to
- PCI device 00:14.5 write the parameter as:
- ivrs_acpihid[00:14.5]=AMD0020:0
-
- js= [HW,JOY] Analog joystick
- See Documentation/input/joystick.txt.
-
- nokaslr [KNL]
- When CONFIG_RANDOMIZE_BASE is set, this disables
- kernel and module base offset ASLR (Address Space
- Layout Randomization).
-
- keepinitrd [HW,ARM]
-
- kernelcore= [KNL,X86,IA-64,PPC]
- Format: nn[KMGTPE] | "mirror"
- This parameter
- specifies the amount of memory usable by the kernel
- for non-movable allocations. The requested amount is
- spread evenly throughout all nodes in the system. The
- remaining memory in each node is used for Movable
- pages. In the event, a node is too small to have both
- kernelcore and Movable pages, kernelcore pages will
- take priority and other nodes will have a larger number
- of Movable pages. The Movable zone is used for the
- allocation of pages that may be reclaimed or moved
- by the page migration subsystem. This means that
- HugeTLB pages may not be allocated from this zone.
- Note that allocations like PTEs-from-HighMem still
- use the HighMem zone if it exists, and the Normal
- zone if it does not.
-
- Instead of specifying the amount of memory (nn[KMGTPE]),
- you can specify "mirror" option. In case "mirror"
- option is specified, mirrored (reliable) memory is used
- for non-movable allocations and remaining memory is used
- for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
- so you can NOT specify nn[KMGTPE] and "mirror" at the same
- time.
-
- kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
- Format: <Controller#>[,poll interval]
- The controller # is the number of the ehci usb debug
- port as it is probed via PCI. The poll interval is
- optional and is the number seconds in between
- each poll cycle to the debug port in case you need
- the functionality for interrupting the kernel with
- gdb or control-c on the dbgp connection. When
- not using this parameter you use sysrq-g to break into
- the kernel debugger.
-
- kgdboc= [KGDB,HW] kgdb over consoles.
- Requires a tty driver that supports console polling,
- or a supported polling keyboard driver (non-usb).
- Serial only format: <serial_device>[,baud]
- keyboard only format: kbd
- keyboard and serial format: kbd,<serial_device>[,baud]
- Optional Kernel mode setting:
- kms, kbd format: kms,kbd
- kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
-
- kgdbwait [KGDB] Stop kernel execution and enter the
- kernel debugger at the earliest opportunity.
-
- kmac= [MIPS] korina ethernet MAC address.
- Configure the RouterBoard 532 series on-chip
- Ethernet adapter MAC address.
-
- kmemleak= [KNL] Boot-time kmemleak enable/disable
- Valid arguments: on, off
- Default: on
- Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
- the default is off.
-
- kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
- Valid arguments: 0, 1, 2
- kmemcheck=0 (disabled)
- kmemcheck=1 (enabled)
- kmemcheck=2 (one-shot mode)
- Default: 2 (one-shot mode)
-
- kstack=N [X86] Print N words from the kernel stack
- in oops dumps.
-
- kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
- Default is 0 (don't ignore, but inject #GP)
-
- kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
- KVM MMU at runtime.
- Default is 0 (off)
-
- kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
- Default is 1 (enabled)
-
- kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
- for all guests.
- Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
-
- kvm-intel.ept= [KVM,Intel] Disable extended page tables
- (virtualized MMU) support on capable Intel chips.
- Default is 1 (enabled)
-
- kvm-intel.emulate_invalid_guest_state=
- [KVM,Intel] Enable emulation of invalid guest states
- Default is 0 (disabled)
-
- kvm-intel.flexpriority=
- [KVM,Intel] Disable FlexPriority feature (TPR shadow).
- Default is 1 (enabled)
-
- kvm-intel.nested=
- [KVM,Intel] Enable VMX nesting (nVMX).
- Default is 0 (disabled)
-
- kvm-intel.unrestricted_guest=
- [KVM,Intel] Disable unrestricted guest feature
- (virtualized real and unpaged mode) on capable
- Intel chips. Default is 1 (enabled)
-
- kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
- feature (tagged TLBs) on capable Intel chips.
- Default is 1 (enabled)
-
- l2cr= [PPC]
-
- l3cr= [PPC]
-
- lapic [X86-32,APIC] Enable the local APIC even if BIOS
- disabled it.
-
- lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
- value for LAPIC timer one-shot implementation. Default
- back to the programmable timer unit in the LAPIC.
-
- lapic_timer_c2_ok [X86,APIC] trust the local apic timer
- in C2 power state.
-
- libata.dma= [LIBATA] DMA control
- libata.dma=0 Disable all PATA and SATA DMA
- libata.dma=1 PATA and SATA Disk DMA only
- libata.dma=2 ATAPI (CDROM) DMA only
- libata.dma=4 Compact Flash DMA only
- Combinations also work, so libata.dma=3 enables DMA
- for disks and CDROMs, but not CFs.
-
- libata.ignore_hpa= [LIBATA] Ignore HPA limit
- libata.ignore_hpa=0 keep BIOS limits (default)
- libata.ignore_hpa=1 ignore limits, using full disk
-
- libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
- when set.
- Format: <int>
-
- libata.force= [LIBATA] Force configurations. The format is comma
- separated list of "[ID:]VAL" where ID is
- PORT[.DEVICE]. PORT and DEVICE are decimal numbers
- matching port, link or device. Basically, it matches
- the ATA ID string printed on console by libata. If
- the whole ID part is omitted, the last PORT and DEVICE
- values are used. If ID hasn't been specified yet, the
- configuration applies to all ports, links and devices.
-
- If only DEVICE is omitted, the parameter applies to
- the port and all links and devices behind it. DEVICE
- number of 0 either selects the first device or the
- first fan-out link behind PMP device. It does not
- select the host link. DEVICE number of 15 selects the
- host link and device attached to it.
-
- The VAL specifies the configuration to force. As long
- as there's no ambiguity shortcut notation is allowed.
- For example, both 1.5 and 1.5G would work for 1.5Gbps.
- The following configurations can be forced.
-
- * Cable type: 40c, 80c, short40c, unk, ign or sata.
- Any ID with matching PORT is used.
-
- * SATA link speed limit: 1.5Gbps or 3.0Gbps.
-
- * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
- udma[/][16,25,33,44,66,100,133] notation is also
- allowed.
-
- * [no]ncq: Turn on or off NCQ.
-
- * [no]ncqtrim: Turn off queued DSM TRIM.
-
- * nohrst, nosrst, norst: suppress hard, soft
- and both resets.
-
- * rstonce: only attempt one reset during
- hot-unplug link recovery
-
- * dump_id: dump IDENTIFY data.
-
- * atapi_dmadir: Enable ATAPI DMADIR bridge support
-
- * disable: Disable this device.
-
- If there are multiple matching configurations changing
- the same attribute, the last one is used.
-
- memblock=debug [KNL] Enable memblock debug messages.
-
- load_ramdisk= [RAM] List of ramdisks to load from floppy
- See Documentation/blockdev/ramdisk.txt.
-
- lockd.nlm_grace_period=P [NFS] Assign grace period.
- Format: <integer>
-
- lockd.nlm_tcpport=N [NFS] Assign TCP port.
- Format: <integer>
-
- lockd.nlm_timeout=T [NFS] Assign timeout value.
- Format: <integer>
-
- lockd.nlm_udpport=M [NFS] Assign UDP port.
- Format: <integer>
-
- locktorture.nreaders_stress= [KNL]
- Set the number of locking read-acquisition kthreads.
- Defaults to being automatically set based on the
- number of online CPUs.
-
- locktorture.nwriters_stress= [KNL]
- Set the number of locking write-acquisition kthreads.
-
- locktorture.onoff_holdoff= [KNL]
- Set time (s) after boot for CPU-hotplug testing.
-
- locktorture.onoff_interval= [KNL]
- Set time (s) between CPU-hotplug operations, or
- zero to disable CPU-hotplug testing.
-
- locktorture.shuffle_interval= [KNL]
- Set task-shuffle interval (jiffies). Shuffling
- tasks allows some CPUs to go into dyntick-idle
- mode during the locktorture test.
-
- locktorture.shutdown_secs= [KNL]
- Set time (s) after boot system shutdown. This
- is useful for hands-off automated testing.
-
- locktorture.stat_interval= [KNL]
- Time (s) between statistics printk()s.
-
- locktorture.stutter= [KNL]
- Time (s) to stutter testing, for example,
- specifying five seconds causes the test to run for
- five seconds, wait for five seconds, and so on.
- This tests the locking primitive's ability to
- transition abruptly to and from idle.
-
- locktorture.torture_runnable= [BOOT]
- Start locktorture running at boot time.
-
- locktorture.torture_type= [KNL]
- Specify the locking implementation to test.
-
- locktorture.verbose= [KNL]
- Enable additional printk() statements.
-
- logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
- Format: <irq>
-
- loglevel= All Kernel Messages with a loglevel smaller than the
- console loglevel will be printed to the console. It can
- also be changed with klogd or other programs. The
- loglevels are defined as follows:
-
- 0 (KERN_EMERG) system is unusable
- 1 (KERN_ALERT) action must be taken immediately
- 2 (KERN_CRIT) critical conditions
- 3 (KERN_ERR) error conditions
- 4 (KERN_WARNING) warning conditions
- 5 (KERN_NOTICE) normal but significant condition
- 6 (KERN_INFO) informational
- 7 (KERN_DEBUG) debug-level messages
-
- log_buf_len=n[KMG] Sets the size of the printk ring buffer,
- in bytes. n must be a power of two and greater
- than the minimal size. The minimal size is defined
- by LOG_BUF_SHIFT kernel config parameter. There is
- also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
- that allows to increase the default size depending on
- the number of CPUs. See init/Kconfig for more details.
-
- logo.nologo [FB] Disables display of the built-in Linux logo.
- This may be used to provide more screen space for
- kernel log messages and is useful when debugging
- kernel boot problems.
-
- lp=0 [LP] Specify parallel ports to use, e.g,
- lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
- lp=reset first parallel port). 'lp=0' disables the
- lp=auto printer driver. 'lp=reset' (which can be
- specified in addition to the ports) causes
- attached printers to be reset. Using
- lp=port1,port2,... specifies the parallel ports
- to associate lp devices with, starting with
- lp0. A port specification may be 'none' to skip
- that lp device, or a parport name such as
- 'parport0'. Specifying 'lp=auto' instead of a
- port specification list means that device IDs
- from each port should be examined, to see if
- an IEEE 1284-compliant printer is attached; if
- so, the driver will manage that printer.
- See also header of drivers/char/lp.c.
-
- lpj=n [KNL]
- Sets loops_per_jiffy to given constant, thus avoiding
- time-consuming boot-time autodetection (up to 250 ms per
- CPU). 0 enables autodetection (default). To determine
- the correct value for your kernel, boot with normal
- autodetection and see what value is printed. Note that
- on SMP systems the preset will be applied to all CPUs,
- which is likely to cause problems if your CPUs need
- significantly divergent settings. An incorrect value
- will cause delays in the kernel to be wrong, leading to
- unpredictable I/O errors and other breakage. Although
- unlikely, in the extreme case this might damage your
- hardware.
-
- ltpc= [NET]
- Format: <io>,<irq>,<dma>
-
- machvec= [IA-64] Force the use of a particular machine-vector
- (machvec) in a generic kernel.
- Example: machvec=hpzx1_swiotlb
-
- machtype= [Loongson] Share the same kernel image file between different
- yeeloong laptop.
- Example: machtype=lemote-yeeloong-2f-7inch
-
- max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
- than or equal to this physical address is ignored.
-
- maxcpus= [SMP] Maximum number of processors that an SMP kernel
- will bring up during bootup. maxcpus=n : n >= 0 limits
- the kernel to bring up 'n' processors. Surely after
- bootup you can bring up the other plugged cpu by executing
- "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
- only takes effect during system bootup.
- While n=0 is a special case, it is equivalent to "nosmp",
- which also disables the IO APIC.
-
- max_loop= [LOOP] The number of loop block devices that get
- (loop.max_loop) unconditionally pre-created at init time. The default
- number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
- of statically allocating a predefined number, loop
- devices can be requested on-demand with the
- /dev/loop-control interface.
-
- mce [X86-32] Machine Check Exception
-
- mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
-
- md= [HW] RAID subsystems devices and level
- See Documentation/admin-guide/md.rst.
-
- mdacon= [MDA]
- Format: <first>,<last>
- Specifies range of consoles to be captured by the MDA.
-
- mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
- Amount of memory to be used when the kernel is not able
- to see the whole system memory or for test.
- [X86] Work as limiting max address. Use together
- with memmap= to avoid physical address space collisions.
- Without memmap= PCI devices could be placed at addresses
- belonging to unused RAM.
-
- mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
- memory.
-
- memchunk=nn[KMG]
- [KNL,SH] Allow user to override the default size for
- per-device physically contiguous DMA buffers.
-
- memhp_default_state=online/offline
- [KNL] Set the initial state for the memory hotplug
- onlining policy. If not specified, the default value is
- set according to the
- CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
- option.
- See Documentation/memory-hotplug.txt.
-
- memmap=exactmap [KNL,X86] Enable setting of an exact
- E820 memory map, as specified by the user.
- Such memmap=exactmap lines can be constructed based on
- BIOS output or other requirements. See the memmap=nn@ss
- option description.
-
- memmap=nn[KMG]@ss[KMG]
- [KNL] Force usage of a specific region of memory.
- Region of memory to be used is from ss to ss+nn.
-
- memmap=nn[KMG]#ss[KMG]
- [KNL,ACPI] Mark specific memory as ACPI data.
- Region of memory to be marked is from ss to ss+nn.
-
- memmap=nn[KMG]$ss[KMG]
- [KNL,ACPI] Mark specific memory as reserved.
- Region of memory to be reserved is from ss to ss+nn.
- Example: Exclude memory from 0x18690000-0x1869ffff
- memmap=64K$0x18690000
- or
- memmap=0x10000$0x18690000
-
- memmap=nn[KMG]!ss[KMG]
- [KNL,X86] Mark specific memory as protected.
- Region of memory to be used, from ss to ss+nn.
- The memory region may be marked as e820 type 12 (0xc)
- and is NVDIMM or ADR memory.
-
- memory_corruption_check=0/1 [X86]
- Some BIOSes seem to corrupt the first 64k of
- memory when doing things like suspend/resume.
- Setting this option will scan the memory
- looking for corruption. Enabling this will
- both detect corruption and prevent the kernel
- from using the memory being corrupted.
- However, its intended as a diagnostic tool; if
- repeatable BIOS-originated corruption always
- affects the same memory, you can use memmap=
- to prevent the kernel from using that memory.
-
- memory_corruption_check_size=size [X86]
- By default it checks for corruption in the low
- 64k, making this memory unavailable for normal
- use. Use this parameter to scan for
- corruption in more or less memory.
-
- memory_corruption_check_period=seconds [X86]
- By default it checks for corruption every 60
- seconds. Use this parameter to check at some
- other rate. 0 disables periodic checking.
-
- memtest= [KNL,X86,ARM] Enable memtest
- Format: <integer>
- default : 0 <disable>
- Specifies the number of memtest passes to be
- performed. Each pass selects another test
- pattern from a given set of patterns. Memtest
- fills the memory with this pattern, validates
- memory contents and reserves bad memory
- regions that are detected.
-
- meye.*= [HW] Set MotionEye Camera parameters
- See Documentation/video4linux/meye.txt.
-
- mfgpt_irq= [IA-32] Specify the IRQ to use for the
- Multi-Function General Purpose Timers on AMD Geode
- platforms.
-
- mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
- the BIOS has incorrectly applied a workaround. TinyBIOS
- version 0.98 is known to be affected, 0.99 fixes the
- problem by letting the user disable the workaround.
-
- mga= [HW,DRM]
-
- min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
- physical address is ignored.
-
- mini2440= [ARM,HW,KNL]
- Format:[0..2][b][c][t]
- Default: "0tb"
- MINI2440 configuration specification:
- 0 - The attached screen is the 3.5" TFT
- 1 - The attached screen is the 7" TFT
- 2 - The VGA Shield is attached (1024x768)
- Leaving out the screen size parameter will not load
- the TFT driver, and the framebuffer will be left
- unconfigured.
- b - Enable backlight. The TFT backlight pin will be
- linked to the kernel VESA blanking code and a GPIO
- LED. This parameter is not necessary when using the
- VGA shield.
- c - Enable the s3c camera interface.
- t - Reserved for enabling touchscreen support. The
- touchscreen support is not enabled in the mainstream
- kernel as of 2.6.30, a preliminary port can be found
- in the "bleeding edge" mini2440 support kernel at
- http://repo.or.cz/w/linux-2.6/mini2440.git
-
- mminit_loglevel=
- [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
- parameter allows control of the logging verbosity for
- the additional memory initialisation checks. A value
- of 0 disables mminit logging and a level of 4 will
- log everything. Information is printed at KERN_DEBUG
- so loglevel=8 may also need to be specified.
-
- module.sig_enforce
- [KNL] When CONFIG_MODULE_SIG is set, this means that
- modules without (valid) signatures will fail to load.
- Note that if CONFIG_MODULE_SIG_FORCE is set, that
- is always true, so this option does nothing.
-
- module_blacklist= [KNL] Do not load a comma-separated list of
- modules. Useful for debugging problem modules.
-
- mousedev.tap_time=
- [MOUSE] Maximum time between finger touching and
- leaving touchpad surface for touch to be considered
- a tap and be reported as a left button click (for
- touchpads working in absolute mode only).
- Format: <msecs>
- mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
- reporting absolute coordinates, such as tablets
- mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
- reporting absolute coordinates, such as tablets
-
- movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
- is similar to kernelcore except it specifies the
- amount of memory used for migratable allocations.
- If both kernelcore and movablecore is specified,
- then kernelcore will be at *least* the specified
- value but may be more. If movablecore on its own
- is specified, the administrator must be careful
- that the amount of memory usable for all allocations
- is not too small.
-
- movable_node [KNL,X86] Boot-time switch to enable the effects
- of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
-
- MTD_Partition= [MTD]
- Format: <name>,<region-number>,<size>,<offset>
-
- MTD_Region= [MTD] Format:
- <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
-
- mtdparts= [MTD]
- See drivers/mtd/cmdlinepart.c.
-
- multitce=off [PPC] This parameter disables the use of the pSeries
- firmware feature for updating multiple TCE entries
- at a time.
-
- onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
-
- Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
-
- boundary - index of last SLC block on Flex-OneNAND.
- The remaining blocks are configured as MLC blocks.
- lock - Configure if Flex-OneNAND boundary should be locked.
- Once locked, the boundary cannot be changed.
- 1 indicates lock status, 0 indicates unlock status.
-
- mtdset= [ARM]
- ARM/S3C2412 JIVE boot control
-
- See arch/arm/mach-s3c2412/mach-jive.c
-
- mtouchusb.raw_coordinates=
- [HW] Make the MicroTouch USB driver use raw coordinates
- ('y', default) or cooked coordinates ('n')
-
- mtrr_chunk_size=nn[KMG] [X86]
- used for mtrr cleanup. It is largest continuous chunk
- that could hold holes aka. UC entries.
-
- mtrr_gran_size=nn[KMG] [X86]
- Used for mtrr cleanup. It is granularity of mtrr block.
- Default is 1.
- Large value could prevent small alignment from
- using up MTRRs.
-
- mtrr_spare_reg_nr=n [X86]
- Format: <integer>
- Range: 0,7 : spare reg number
- Default : 1
- Used for mtrr cleanup. It is spare mtrr entries number.
- Set to 2 or more if your graphical card needs more.
-
- n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
-
- netdev= [NET] Network devices parameters
- Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
- Note that mem_start is often overloaded to mean
- something different and driver-specific.
- This usage is only documented in each driver source
- file if at all.
-
- nf_conntrack.acct=
- [NETFILTER] Enable connection tracking flow accounting
- 0 to disable accounting
- 1 to enable accounting
- Default value is 0.
-
- nfsaddrs= [NFS] Deprecated. Use ip= instead.
- See Documentation/filesystems/nfs/nfsroot.txt.
-
- nfsroot= [NFS] nfs root filesystem for disk-less boxes.
- See Documentation/filesystems/nfs/nfsroot.txt.
-
- nfsrootdebug [NFS] enable nfsroot debugging messages.
- See Documentation/filesystems/nfs/nfsroot.txt.
-
- nfs.callback_nr_threads=
- [NFSv4] set the total number of threads that the
- NFS client will assign to service NFSv4 callback
- requests.
-
- nfs.callback_tcpport=
- [NFS] set the TCP port on which the NFSv4 callback
- channel should listen.
-
- nfs.cache_getent=
- [NFS] sets the pathname to the program which is used
- to update the NFS client cache entries.
-
- nfs.cache_getent_timeout=
- [NFS] sets the timeout after which an attempt to
- update a cache entry is deemed to have failed.
-
- nfs.idmap_cache_timeout=
- [NFS] set the maximum lifetime for idmapper cache
- entries.
-
- nfs.enable_ino64=
- [NFS] enable 64-bit inode numbers.
- If zero, the NFS client will fake up a 32-bit inode
- number for the readdir() and stat() syscalls instead
- of returning the full 64-bit number.
- The default is to return 64-bit inode numbers.
-
- nfs.max_session_cb_slots=
- [NFSv4.1] Sets the maximum number of session
- slots the client will assign to the callback
- channel. This determines the maximum number of
- callbacks the client will process in parallel for
- a particular server.
-
- nfs.max_session_slots=
- [NFSv4.1] Sets the maximum number of session slots
- the client will attempt to negotiate with the server.
- This limits the number of simultaneous RPC requests
- that the client can send to the NFSv4.1 server.
- Note that there is little point in setting this
- value higher than the max_tcp_slot_table_limit.
-
- nfs.nfs4_disable_idmapping=
- [NFSv4] When set to the default of '1', this option
- ensures that both the RPC level authentication
- scheme and the NFS level operations agree to use
- numeric uids/gids if the mount is using the
- 'sec=sys' security flavour. In effect it is
- disabling idmapping, which can make migration from
- legacy NFSv2/v3 systems to NFSv4 easier.
- Servers that do not support this mode of operation
- will be autodetected by the client, and it will fall
- back to using the idmapper.
- To turn off this behaviour, set the value to '0'.
- nfs.nfs4_unique_id=
- [NFS4] Specify an additional fixed unique ident-
- ification string that NFSv4 clients can insert into
- their nfs_client_id4 string. This is typically a
- UUID that is generated at system install time.
-
- nfs.send_implementation_id =
- [NFSv4.1] Send client implementation identification
- information in exchange_id requests.
- If zero, no implementation identification information
- will be sent.
- The default is to send the implementation identification
- information.
-
- nfs.recover_lost_locks =
- [NFSv4] Attempt to recover locks that were lost due
- to a lease timeout on the server. Please note that
- doing this risks data corruption, since there are
- no guarantees that the file will remain unchanged
- after the locks are lost.
- If you want to enable the kernel legacy behaviour of
- attempting to recover these locks, then set this
- parameter to '1'.
- The default parameter value of '0' causes the kernel
- not to attempt recovery of lost locks.
-
- nfs4.layoutstats_timer =
- [NFSv4.2] Change the rate at which the kernel sends
- layoutstats to the pNFS metadata server.
-
- Setting this to value to 0 causes the kernel to use
- whatever value is the default set by the layout
- driver. A non-zero value sets the minimum interval
- in seconds between layoutstats transmissions.
-
- nfsd.nfs4_disable_idmapping=
- [NFSv4] When set to the default of '1', the NFSv4
- server will return only numeric uids and gids to
- clients using auth_sys, and will accept numeric uids
- and gids from such clients. This is intended to ease
- migration from NFSv2/v3.
-
- objlayoutdriver.osd_login_prog=
- [NFS] [OBJLAYOUT] sets the pathname to the program which
- is used to automatically discover and login into new
- osd-targets. Please see:
- Documentation/filesystems/pnfs.txt for more explanations
-
- nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
- when a NMI is triggered.
- Format: [state][,regs][,debounce][,die]
-
- nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
- Format: [panic,][nopanic,][num]
- Valid num: 0 or 1
- 0 - turn hardlockup detector in nmi_watchdog off
- 1 - turn hardlockup detector in nmi_watchdog on
- When panic is specified, panic when an NMI watchdog
- timeout occurs (or 'nopanic' to override the opposite
- default). To disable both hard and soft lockup detectors,
- please see 'nowatchdog'.
- This is useful when you use a panic=... timeout and
- need the box quickly up again.
-
- netpoll.carrier_timeout=
- [NET] Specifies amount of time (in seconds) that
- netpoll should wait for a carrier. By default netpoll
- waits 4 seconds.
-
- no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
- emulation library even if a 387 maths coprocessor
- is present.
-
- no_console_suspend
- [HW] Never suspend the console
- Disable suspending of consoles during suspend and
- hibernate operations. Once disabled, debugging
- messages can reach various consoles while the rest
- of the system is being put to sleep (ie, while
- debugging driver suspend/resume hooks). This may
- not work reliably with all consoles, but is known
- to work with serial and VGA consoles.
- To facilitate more flexible debugging, we also add
- console_suspend, a printk module parameter to control
- it. Users could use console_suspend (usually
- /sys/module/printk/parameters/console_suspend) to
- turn on/off it dynamically.
-
- noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
- caches in the slab allocator. Saves per-node memory,
- but will impact performance.
-
- noalign [KNL,ARM]
-
- noapic [SMP,APIC] Tells the kernel to not make use of any
- IOAPICs that may be present in the system.
-
- noautogroup Disable scheduler automatic task group creation.
-
- nobats [PPC] Do not use BATs for mapping kernel lowmem
- on "Classic" PPC cores.
-
- nocache [ARM]
-
- noclflush [BUGS=X86] Don't use the CLFLUSH instruction
-
- nodelayacct [KNL] Disable per-task delay accounting
-
- nodsp [SH] Disable hardware DSP at boot time.
-
- noefi Disable EFI runtime services support.
-
- noexec [IA-64]
-
- noexec [X86]
- On X86-32 available only on PAE configured kernels.
- noexec=on: enable non-executable mappings (default)
- noexec=off: disable non-executable mappings
-
- nosmap [X86]
- Disable SMAP (Supervisor Mode Access Prevention)
- even if it is supported by processor.
-
- nosmep [X86]
- Disable SMEP (Supervisor Mode Execution Prevention)
- even if it is supported by processor.
-
- noexec32 [X86-64]
- This affects only 32-bit executables.
- noexec32=on: enable non-executable mappings (default)
- read doesn't imply executable mappings
- noexec32=off: disable non-executable mappings
- read implies executable mappings
-
- nofpu [MIPS,SH] Disable hardware FPU at boot time.
-
- nofxsr [BUGS=X86-32] Disables x86 floating point extended
- register save and restore. The kernel will only save
- legacy floating-point registers on task switch.
-
- nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
-
- nosmt [KNL,S390] Disable symmetric multithreading (SMT).
- Equivalent to smt=1.
-
- noxsave [BUGS=X86] Disables x86 extended register state save
- and restore using xsave. The kernel will fallback to
- enabling legacy floating-point and sse state.
-
- noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
- register states. The kernel will fall back to use
- xsave to save the states. By using this parameter,
- performance of saving the states is degraded because
- xsave doesn't support modified optimization while
- xsaveopt supports it on xsaveopt enabled systems.
-
- noxsaves [X86] Disables xsaves and xrstors used in saving and
- restoring x86 extended register state in compacted
- form of xsave area. The kernel will fall back to use
- xsaveopt and xrstor to save and restore the states
- in standard form of xsave area. By using this
- parameter, xsave area per process might occupy more
- memory on xsaves enabled systems.
-
- nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
- wfi(ARM) instruction doesn't work correctly and not to
- use it. This is also useful when using JTAG debugger.
-
- no_file_caps Tells the kernel not to honor file capabilities. The
- only way then for a file to be executed with privilege
- is to be setuid root or executed by root.
-
- nohalt [IA-64] Tells the kernel not to use the power saving
- function PAL_HALT_LIGHT when idle. This increases
- power-consumption. On the positive side, it reduces
- interrupt wake-up latency, which may improve performance
- in certain environments such as networked servers or
- real-time systems.
-
- nohibernate [HIBERNATION] Disable hibernation and resume.
-
- nohz= [KNL] Boottime enable/disable dynamic ticks
- Valid arguments: on, off
- Default: on
-
- nohz_full= [KNL,BOOT]
- The argument is a cpu list, as described above.
- In kernels built with CONFIG_NO_HZ_FULL=y, set
- the specified list of CPUs whose tick will be stopped
- whenever possible. The boot CPU will be forced outside
- the range to maintain the timekeeping.
- The CPUs in this range must also be included in the
- rcu_nocbs= set.
-
- noiotrap [SH] Disables trapped I/O port accesses.
-
- noirqdebug [X86-32] Disables the code which attempts to detect and
- disable unhandled interrupt sources.
-
- no_timer_check [X86,APIC] Disables the code which tests for
- broken timer IRQ sources.
-
- noisapnp [ISAPNP] Disables ISA PnP code.
-
- noinitrd [RAM] Tells the kernel not to load any configured
- initial RAM disk.
-
- nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
- remapping.
- [Deprecated - use intremap=off]
-
- nointroute [IA-64]
-
- noinvpcid [X86] Disable the INVPCID cpu feature.
-
- nojitter [IA-64] Disables jitter checking for ITC timers.
-
- no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
-
- no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
- fault handling.
-
- no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
- steal time is computed, but won't influence scheduler
- behaviour
-
- nolapic [X86-32,APIC] Do not enable or use the local APIC.
-
- nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
-
- noltlbs [PPC] Do not use large page/tlb entries for kernel
- lowmem mapping on PPC40x and PPC8xx
-
- nomca [IA-64] Disable machine check abort handling
-
- nomce [X86-32] Disable Machine Check Exception
-
- nomfgpt [X86-32] Disable Multi-Function General Purpose
- Timer usage (for AMD Geode machines).
-
- nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
- shutdown the other cpus. Instead use the REBOOT_VECTOR
- irq.
-
- nomodule Disable module load
-
- nopat [X86] Disable PAT (page attribute table extension of
- pagetables) support.
-
- norandmaps Don't use address space randomization. Equivalent to
- echo 0 > /proc/sys/kernel/randomize_va_space
-
- noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
-
- noreplace-smp [X86-32,SMP] Don't replace SMP instructions
- with UP alternatives
-
- nordrand [X86] Disable kernel use of the RDRAND and
- RDSEED instructions even if they are supported
- by the processor. RDRAND and RDSEED are still
- available to user space applications.
-
- noresume [SWSUSP] Disables resume and restores original swap
- space.
-
- no-scroll [VGA] Disables scrollback.
- This is required for the Braillex ib80-piezo Braille
- reader made by F.H. Papenmeier (Germany).
-
- nosbagart [IA-64]
-
- nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
-
- nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
- and disable the IO APIC. legacy for "maxcpus=0".
-
- nosoftlockup [KNL] Disable the soft-lockup detector.
-
- nosync [HW,M68K] Disables sync negotiation for all devices.
-
- notsc [BUGS=X86-32] Disable Time Stamp Counter
-
- nowatchdog [KNL] Disable both lockup detectors, i.e.
- soft-lockup and NMI watchdog (hard-lockup).
-
- nowb [ARM]
-
- nox2apic [X86-64,APIC] Do not enable x2APIC mode.
-
- cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
- CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
- Some features depend on CPU0. Known dependencies are:
- 1. Resume from suspend/hibernate depends on CPU0.
- Suspend/hibernate will fail if CPU0 is offline and you
- need to online CPU0 before suspend/hibernate.
- 2. PIC interrupts also depend on CPU0. CPU0 can't be
- removed if a PIC interrupt is detected.
- It's said poweroff/reboot may depend on CPU0 on some
- machines although I haven't seen such issues so far
- after CPU0 is offline on a few tested machines.
- If the dependencies are under your control, you can
- turn on cpu0_hotplug.
-
- nptcg= [IA-64] Override max number of concurrent global TLB
- purges which is reported from either PAL_VM_SUMMARY or
- SAL PALO.
-
- nr_cpus= [SMP] Maximum number of processors that an SMP kernel
- could support. nr_cpus=n : n >= 1 limits the kernel to
- support 'n' processors. It could be larger than the
- number of already plugged CPU during bootup, later in
- runtime you can physically add extra cpu until it reaches
- n. So during boot up some boot time memory for per-cpu
- variables need be pre-allocated for later physical cpu
- hot plugging.
-
- nr_uarts= [SERIAL] maximum number of UARTs to be registered.
-
- numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
- Allowed values are enable and disable
-
- numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
- one of ['zone', 'node', 'default'] can be specified
- This can be set from sysctl after boot.
- See Documentation/sysctl/vm.txt for details.
-
- ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
- See Documentation/debugging-via-ohci1394.txt for more
- info.
-
- olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
- Rather than timing out after 20 ms if an EC
- command is not properly ACKed, override the length
- of the timeout. We have interrupts disabled while
- waiting for the ACK, so if this is set too high
- interrupts *may* be lost!
-
- omap_mux= [OMAP] Override bootloader pin multiplexing.
- Format: <mux_mode0.mode_name=value>...
- For example, to override I2C bus2:
- omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
-
- oprofile.timer= [HW]
- Use timer interrupt instead of performance counters
-
- oprofile.cpu_type= Force an oprofile cpu type
- This might be useful if you have an older oprofile
- userland or if you want common events.
- Format: { arch_perfmon }
- arch_perfmon: [X86] Force use of architectural
- perfmon on Intel CPUs instead of the
- CPU specific event set.
- timer: [X86] Force use of architectural NMI
- timer mode (see also oprofile.timer
- for generic hr timer mode)
-
- oops=panic Always panic on oopses. Default is to just kill the
- process, but there is a small probability of
- deadlocking the machine.
- This will also cause panics on machine check exceptions.
- Useful together with panic=30 to trigger a reboot.
-
- OSS [HW,OSS]
- See Documentation/sound/oss/oss-parameters.txt
-
- page_owner= [KNL] Boot-time page_owner enabling option.
- Storage of the information about who allocated
- each page is disabled in default. With this switch,
- we can turn it on.
- on: enable the feature
-
- page_poison= [KNL] Boot-time parameter changing the state of
- poisoning on the buddy allocator.
- off: turn off poisoning
- on: turn on poisoning
-
- panic= [KNL] Kernel behaviour on panic: delay <timeout>
- timeout > 0: seconds before rebooting
- timeout = 0: wait forever
- timeout < 0: reboot immediately
- Format: <timeout>
-
- panic_on_warn panic() instead of WARN(). Useful to cause kdump
- on a WARN().
-
- crash_kexec_post_notifiers
- Run kdump after running panic-notifiers and dumping
- kmsg. This only for the users who doubt kdump always
- succeeds in any situation.
- Note that this also increases risks of kdump failure,
- because some panic notifiers can make the crashed
- kernel more unstable.
-
- parkbd.port= [HW] Parallel port number the keyboard adapter is
- connected to, default is 0.
- Format: <parport#>
- parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
- 0 for XT, 1 for AT (default is AT).
- Format: <mode>
-
- parport= [HW,PPT] Specify parallel ports. 0 disables.
- Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
- Use 'auto' to force the driver to use any
- IRQ/DMA settings detected (the default is to
- ignore detected IRQ/DMA settings because of
- possible conflicts). You can specify the base
- address, IRQ, and DMA settings; IRQ and DMA
- should be numbers, or 'auto' (for using detected
- settings on that particular port), or 'nofifo'
- (to avoid using a FIFO even if it is detected).
- Parallel ports are assigned in the order they
- are specified on the command line, starting
- with parport0.
-
- parport_init_mode= [HW,PPT]
- Configure VIA parallel port to operate in
- a specific mode. This is necessary on Pegasos
- computer where firmware has no options for setting
- up parallel port mode and sets it to spp.
- Currently this function knows 686a and 8231 chips.
- Format: [spp|ps2|epp|ecp|ecpepp]
-
- pause_on_oops=
- Halt all CPUs after the first oops has been printed for
- the specified number of seconds. This is to be used if
- your oopses keep scrolling off the screen.
-
- pcbit= [HW,ISDN]
-
- pcd. [PARIDE]
- See header of drivers/block/paride/pcd.c.
- See also Documentation/blockdev/paride.txt.
-
- pci=option[,option...] [PCI] various PCI subsystem options:
- earlydump [X86] dump PCI config space before the kernel
- changes anything
- off [X86] don't probe for the PCI bus
- bios [X86-32] force use of PCI BIOS, don't access
- the hardware directly. Use this if your machine
- has a non-standard PCI host bridge.
- nobios [X86-32] disallow use of PCI BIOS, only direct
- hardware access methods are allowed. Use this
- if you experience crashes upon bootup and you
- suspect they are caused by the BIOS.
- conf1 [X86] Force use of PCI Configuration Access
- Mechanism 1 (config address in IO port 0xCF8,
- data in IO port 0xCFC, both 32-bit).
- conf2 [X86] Force use of PCI Configuration Access
- Mechanism 2 (IO port 0xCF8 is an 8-bit port for
- the function, IO port 0xCFA, also 8-bit, sets
- bus number. The config space is then accessed
- through ports 0xC000-0xCFFF).
- See http://wiki.osdev.org/PCI for more info
- on the configuration access mechanisms.
- noaer [PCIE] If the PCIEAER kernel config parameter is
- enabled, this kernel boot option can be used to
- disable the use of PCIE advanced error reporting.
- nodomains [PCI] Disable support for multiple PCI
- root domains (aka PCI segments, in ACPI-speak).
- nommconf [X86] Disable use of MMCONFIG for PCI
- Configuration
- check_enable_amd_mmconf [X86] check for and enable
- properly configured MMIO access to PCI
- config space on AMD family 10h CPU
- nomsi [MSI] If the PCI_MSI kernel config parameter is
- enabled, this kernel boot option can be used to
- disable the use of MSI interrupts system-wide.
- noioapicquirk [APIC] Disable all boot interrupt quirks.
- Safety option to keep boot IRQs enabled. This
- should never be necessary.
- ioapicreroute [APIC] Enable rerouting of boot IRQs to the
- primary IO-APIC for bridges that cannot disable
- boot IRQs. This fixes a source of spurious IRQs
- when the system masks IRQs.
- noioapicreroute [APIC] Disable workaround that uses the
- boot IRQ equivalent of an IRQ that connects to
- a chipset where boot IRQs cannot be disabled.
- The opposite of ioapicreroute.
- biosirq [X86-32] Use PCI BIOS calls to get the interrupt
- routing table. These calls are known to be buggy
- on several machines and they hang the machine
- when used, but on other computers it's the only
- way to get the interrupt routing table. Try
- this option if the kernel is unable to allocate
- IRQs or discover secondary PCI buses on your
- motherboard.
- rom [X86] Assign address space to expansion ROMs.
- Use with caution as certain devices share
- address decoders between ROMs and other
- resources.
- norom [X86] Do not assign address space to
- expansion ROMs that do not already have
- BIOS assigned address ranges.
- nobar [X86] Do not assign address space to the
- BARs that weren't assigned by the BIOS.
- irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
- assigned automatically to PCI devices. You can
- make the kernel exclude IRQs of your ISA cards
- this way.
- pirqaddr=0xAAAAA [X86] Specify the physical address
- of the PIRQ table (normally generated
- by the BIOS) if it is outside the
- F0000h-100000h range.
- lastbus=N [X86] Scan all buses thru bus #N. Can be
- useful if the kernel is unable to find your
- secondary buses and you want to tell it
- explicitly which ones they are.
- assign-busses [X86] Always assign all PCI bus
- numbers ourselves, overriding
- whatever the firmware may have done.
- usepirqmask [X86] Honor the possible IRQ mask stored
- in the BIOS $PIR table. This is needed on
- some systems with broken BIOSes, notably
- some HP Pavilion N5400 and Omnibook XE3
- notebooks. This will have no effect if ACPI
- IRQ routing is enabled.
- noacpi [X86] Do not use ACPI for IRQ routing
- or for PCI scanning.
- use_crs [X86] Use PCI host bridge window information
- from ACPI. On BIOSes from 2008 or later, this
- is enabled by default. If you need to use this,
- please report a bug.
- nocrs [X86] Ignore PCI host bridge windows from ACPI.
- If you need to use this, please report a bug.
- routeirq Do IRQ routing for all PCI devices.
- This is normally done in pci_enable_device(),
- so this option is a temporary workaround
- for broken drivers that don't call it.
- skip_isa_align [X86] do not align io start addr, so can
- handle more pci cards
- noearly [X86] Don't do any early type 1 scanning.
- This might help on some broken boards which
- machine check when some devices' config space
- is read. But various workarounds are disabled
- and some IOMMU drivers will not work.
- bfsort Sort PCI devices into breadth-first order.
- This sorting is done to get a device
- order compatible with older (<= 2.4) kernels.
- nobfsort Don't sort PCI devices into breadth-first order.
- pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
- tuning and use the BIOS-configured MPS defaults.
- pcie_bus_safe Set every device's MPS to the largest value
- supported by all devices below the root complex.
- pcie_bus_perf Set device MPS to the largest allowable MPS
- based on its parent bus. Also set MRRS (Max
- Read Request Size) to the largest supported
- value (no larger than the MPS that the device
- or bus can support) for best performance.
- pcie_bus_peer2peer Set every device's MPS to 128B, which
- every device is guaranteed to support. This
- configuration allows peer-to-peer DMA between
- any pair of devices, possibly at the cost of
- reduced performance. This also guarantees
- that hot-added devices will work.
- cbiosize=nn[KMG] The fixed amount of bus space which is
- reserved for the CardBus bridge's IO window.
- The default value is 256 bytes.
- cbmemsize=nn[KMG] The fixed amount of bus space which is
- reserved for the CardBus bridge's memory
- window. The default value is 64 megabytes.
- resource_alignment=
- Format:
- [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
- [<order of align>@]pci:<vendor>:<device>\
- [:<subvendor>:<subdevice>][; ...]
- Specifies alignment and device to reassign
- aligned memory resources.
- If <order of align> is not specified,
- PAGE_SIZE is used as alignment.
- PCI-PCI bridge can be specified, if resource
- windows need to be expanded.
- To specify the alignment for several
- instances of a device, the PCI vendor,
- device, subvendor, and subdevice may be
- specified, e.g., 4096@pci:8086:9c22:103c:198f
- ecrc= Enable/disable PCIe ECRC (transaction layer
- end-to-end CRC checking).
- bios: Use BIOS/firmware settings. This is the
- the default.
- off: Turn ECRC off
- on: Turn ECRC on.
- hpiosize=nn[KMG] The fixed amount of bus space which is
- reserved for hotplug bridge's IO window.
- Default size is 256 bytes.
- hpmemsize=nn[KMG] The fixed amount of bus space which is
- reserved for hotplug bridge's memory window.
- Default size is 2 megabytes.
- hpbussize=nn The minimum amount of additional bus numbers
- reserved for buses below a hotplug bridge.
- Default is 1.
- realloc= Enable/disable reallocating PCI bridge resources
- if allocations done by BIOS are too small to
- accommodate resources required by all child
- devices.
- off: Turn realloc off
- on: Turn realloc on
- realloc same as realloc=on
- noari do not use PCIe ARI.
- pcie_scan_all Scan all possible PCIe devices. Otherwise we
- only look for one device below a PCIe downstream
- port.
-
- pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
- Management.
- off Disable ASPM.
- force Enable ASPM even on devices that claim not to support it.
- WARNING: Forcing ASPM on may cause system lockups.
-
- pcie_hp= [PCIE] PCI Express Hotplug driver options:
- nomsi Do not use MSI for PCI Express Native Hotplug (this
- makes all PCIe ports use INTx for hotplug services).
-
- pcie_ports= [PCIE] PCIe ports handling:
- auto Ask the BIOS whether or not to use native PCIe services
- associated with PCIe ports (PME, hot-plug, AER). Use
- them only if that is allowed by the BIOS.
- native Use native PCIe services associated with PCIe ports
- unconditionally.
- compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
- ports driver.
-
- pcie_port_pm= [PCIE] PCIe port power management handling:
- off Disable power management of all PCIe ports
- force Forcibly enable power management of all PCIe ports
-
- pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
- nomsi Do not use MSI for native PCIe PME signaling (this makes
- all PCIe root ports use INTx for all services).
-
- pcmv= [HW,PCMCIA] BadgePAD 4
-
- pd_ignore_unused
- [PM]
- Keep all power-domains already enabled by bootloader on,
- even if no driver has claimed them. This is useful
- for debug and development, but should not be
- needed on a platform with proper driver support.
-
- pd. [PARIDE]
- See Documentation/blockdev/paride.txt.
-
- pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
- boot time.
- Format: { 0 | 1 }
- See arch/parisc/kernel/pdc_chassis.c
-
- percpu_alloc= Select which percpu first chunk allocator to use.
- Currently supported values are "embed" and "page".
- Archs may support subset or none of the selections.
- See comments in mm/percpu.c for details on each
- allocator. This parameter is primarily for debugging
- and performance comparison.
-
- pf. [PARIDE]
- See Documentation/blockdev/paride.txt.
-
- pg. [PARIDE]
- See Documentation/blockdev/paride.txt.
-
- pirq= [SMP,APIC] Manual mp-table setup
- See Documentation/x86/i386/IO-APIC.txt.
-
- plip= [PPT,NET] Parallel port network link
- Format: { parport<nr> | timid | 0 }
- See also Documentation/parport.txt.
-
- pmtmr= [X86] Manual setup of pmtmr I/O Port.
- Override pmtimer IOPort with a hex value.
- e.g. pmtmr=0x508
-
- pnp.debug=1 [PNP]
- Enable PNP debug messages (depends on the
- CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
- via /sys/module/pnp/parameters/debug. We always show
- current resource usage; turning this on also shows
- possible settings and some assignment information.
-
- pnpacpi= [ACPI]
- { off }
-
- pnpbios= [ISAPNP]
- { on | off | curr | res | no-curr | no-res }
-
- pnp_reserve_irq=
- [ISAPNP] Exclude IRQs for the autoconfiguration
-
- pnp_reserve_dma=
- [ISAPNP] Exclude DMAs for the autoconfiguration
-
- pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
- Ranges are in pairs (I/O port base and size).
-
- pnp_reserve_mem=
- [ISAPNP] Exclude memory regions for the
- autoconfiguration.
- Ranges are in pairs (memory base and size).
-
- ports= [IP_VS_FTP] IPVS ftp helper module
- Default is 21.
- Up to 8 (IP_VS_APP_MAX_PORTS) ports
- may be specified.
- Format: <port>,<port>....
-
- ppc_strict_facility_enable
- [PPC] This option catches any kernel floating point,
- Altivec, VSX and SPE outside of regions specifically
- allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
- There is some performance impact when enabling this.
-
- print-fatal-signals=
- [KNL] debug: print fatal signals
-
- If enabled, warn about various signal handling
- related application anomalies: too many signals,
- too many POSIX.1 timers, fatal signals causing a
- coredump - etc.
-
- If you hit the warning due to signal overflow,
- you might want to try "ulimit -i unlimited".
-
- default: off.
-
- printk.always_kmsg_dump=
- Trigger kmsg_dump for cases other than kernel oops or
- panics
- Format: <bool> (1/Y/y=enable, 0/N/n=disable)
- default: disabled
-
- printk.devkmsg={on,off,ratelimit}
- Control writing to /dev/kmsg.
- on - unlimited logging to /dev/kmsg from userspace
- off - logging to /dev/kmsg disabled
- ratelimit - ratelimit the logging
- Default: ratelimit
-
- printk.time= Show timing data prefixed to each printk message line
- Format: <bool> (1/Y/y=enable, 0/N/n=disable)
-
- processor.max_cstate= [HW,ACPI]
- Limit processor to maximum C-state
- max_cstate=9 overrides any DMI blacklist limit.
-
- processor.nocst [HW,ACPI]
- Ignore the _CST method to determine C-states,
- instead using the legacy FADT method
-
- profile= [KNL] Enable kernel profiling via /proc/profile
- Format: [schedule,]<number>
- Param: "schedule" - profile schedule points.
- Param: <number> - step/bucket size as a power of 2 for
- statistical time based profiling.
- Param: "sleep" - profile D-state sleeping (millisecs).
- Requires CONFIG_SCHEDSTATS
- Param: "kvm" - profile VM exits.
-
- prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
- before loading.
- See Documentation/blockdev/ramdisk.txt.
-
- psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
- probe for; one of (bare|imps|exps|lifebook|any).
- psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
- per second.
- psmouse.resetafter= [HW,MOUSE]
- Try to reset the device after so many bad packets
- (0 = never).
- psmouse.resolution=
- [HW,MOUSE] Set desired mouse resolution, in dpi.
- psmouse.smartscroll=
- [HW,MOUSE] Controls Logitech smartscroll autorepeat.
- 0 = disabled, 1 = enabled (default).
-
- pstore.backend= Specify the name of the pstore backend to use
-
- pt. [PARIDE]
- See Documentation/blockdev/paride.txt.
-
- pty.legacy_count=
- [KNL] Number of legacy pty's. Overwrites compiled-in
- default number.
-
- quiet [KNL] Disable most log messages
-
- r128= [HW,DRM]
-
- raid= [HW,RAID]
- See Documentation/admin-guide/md.rst.
-
- ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
- See Documentation/blockdev/ramdisk.txt.
-
- rcu_nocbs= [KNL]
- The argument is a cpu list, as described above.
-
- In kernels built with CONFIG_RCU_NOCB_CPU=y, set
- the specified list of CPUs to be no-callback CPUs.
- Invocation of these CPUs' RCU callbacks will
- be offloaded to "rcuox/N" kthreads created for
- that purpose, where "x" is "b" for RCU-bh, "p"
- for RCU-preempt, and "s" for RCU-sched, and "N"
- is the CPU number. This reduces OS jitter on the
- offloaded CPUs, which can be useful for HPC and
- real-time workloads. It can also improve energy
- efficiency for asymmetric multiprocessors.
-
- rcu_nocb_poll [KNL]
- Rather than requiring that offloaded CPUs
- (specified by rcu_nocbs= above) explicitly
- awaken the corresponding "rcuoN" kthreads,
- make these kthreads poll for callbacks.
- This improves the real-time response for the
- offloaded CPUs by relieving them of the need to
- wake up the corresponding kthread, but degrades
- energy efficiency by requiring that the kthreads
- periodically wake up to do the polling.
-
- rcutree.blimit= [KNL]
- Set maximum number of finished RCU callbacks to
- process in one batch.
-
- rcutree.dump_tree= [KNL]
- Dump the structure of the rcu_node combining tree
- out at early boot. This is used for diagnostic
- purposes, to verify correct tree setup.
-
- rcutree.gp_cleanup_delay= [KNL]
- Set the number of jiffies to delay each step of
- RCU grace-period cleanup. This only has effect
- when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
-
- rcutree.gp_init_delay= [KNL]
- Set the number of jiffies to delay each step of
- RCU grace-period initialization. This only has
- effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
- is set.
-
- rcutree.gp_preinit_delay= [KNL]
- Set the number of jiffies to delay each step of
- RCU grace-period pre-initialization, that is,
- the propagation of recent CPU-hotplug changes up
- the rcu_node combining tree. This only has effect
- when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
-
- rcutree.rcu_fanout_exact= [KNL]
- Disable autobalancing of the rcu_node combining
- tree. This is used by rcutorture, and might
- possibly be useful for architectures having high
- cache-to-cache transfer latencies.
-
- rcutree.rcu_fanout_leaf= [KNL]
- Change the number of CPUs assigned to each
- leaf rcu_node structure. Useful for very
- large systems, which will choose the value 64,
- and for NUMA systems with large remote-access
- latencies, which will choose a value aligned
- with the appropriate hardware boundaries.
-
- rcutree.jiffies_till_sched_qs= [KNL]
- Set required age in jiffies for a
- given grace period before RCU starts
- soliciting quiescent-state help from
- rcu_note_context_switch().
-
- rcutree.jiffies_till_first_fqs= [KNL]
- Set delay from grace-period initialization to
- first attempt to force quiescent states.
- Units are jiffies, minimum value is zero,
- and maximum value is HZ.
-
- rcutree.jiffies_till_next_fqs= [KNL]
- Set delay between subsequent attempts to force
- quiescent states. Units are jiffies, minimum
- value is one, and maximum value is HZ.
-
- rcutree.kthread_prio= [KNL,BOOT]
- Set the SCHED_FIFO priority of the RCU per-CPU
- kthreads (rcuc/N). This value is also used for
- the priority of the RCU boost threads (rcub/N)
- and for the RCU grace-period kthreads (rcu_bh,
- rcu_preempt, and rcu_sched). If RCU_BOOST is
- set, valid values are 1-99 and the default is 1
- (the least-favored priority). Otherwise, when
- RCU_BOOST is not set, valid values are 0-99 and
- the default is zero (non-realtime operation).
-
- rcutree.rcu_nocb_leader_stride= [KNL]
- Set the number of NOCB kthread groups, which
- defaults to the square root of the number of
- CPUs. Larger numbers reduces the wakeup overhead
- on the per-CPU grace-period kthreads, but increases
- that same overhead on each group's leader.
-
- rcutree.qhimark= [KNL]
- Set threshold of queued RCU callbacks beyond which
- batch limiting is disabled.
-
- rcutree.qlowmark= [KNL]
- Set threshold of queued RCU callbacks below which
- batch limiting is re-enabled.
-
- rcutree.rcu_idle_gp_delay= [KNL]
- Set wakeup interval for idle CPUs that have
- RCU callbacks (RCU_FAST_NO_HZ=y).
-
- rcutree.rcu_idle_lazy_gp_delay= [KNL]
- Set wakeup interval for idle CPUs that have
- only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
- Lazy RCU callbacks are those which RCU can
- prove do nothing more than free memory.
-
- rcuperf.gp_exp= [KNL]
- Measure performance of expedited synchronous
- grace-period primitives.
-
- rcuperf.holdoff= [KNL]
- Set test-start holdoff period. The purpose of
- this parameter is to delay the start of the
- test until boot completes in order to avoid
- interference.
-
- rcuperf.nreaders= [KNL]
- Set number of RCU readers. The value -1 selects
- N, where N is the number of CPUs. A value
- "n" less than -1 selects N-n+1, where N is again
- the number of CPUs. For example, -2 selects N
- (the number of CPUs), -3 selects N+1, and so on.
- A value of "n" less than or equal to -N selects
- a single reader.
-
- rcuperf.nwriters= [KNL]
- Set number of RCU writers. The values operate
- the same as for rcuperf.nreaders.
- N, where N is the number of CPUs
-
- rcuperf.perf_runnable= [BOOT]
- Start rcuperf running at boot time.
-
- rcuperf.shutdown= [KNL]
- Shut the system down after performance tests
- complete. This is useful for hands-off automated
- testing.
-
- rcuperf.perf_type= [KNL]
- Specify the RCU implementation to test.
-
- rcuperf.verbose= [KNL]
- Enable additional printk() statements.
-
- rcutorture.cbflood_inter_holdoff= [KNL]
- Set holdoff time (jiffies) between successive
- callback-flood tests.
-
- rcutorture.cbflood_intra_holdoff= [KNL]
- Set holdoff time (jiffies) between successive
- bursts of callbacks within a given callback-flood
- test.
-
- rcutorture.cbflood_n_burst= [KNL]
- Set the number of bursts making up a given
- callback-flood test. Set this to zero to
- disable callback-flood testing.
-
- rcutorture.cbflood_n_per_burst= [KNL]
- Set the number of callbacks to be registered
- in a given burst of a callback-flood test.
-
- rcutorture.fqs_duration= [KNL]
- Set duration of force_quiescent_state bursts
- in microseconds.
-
- rcutorture.fqs_holdoff= [KNL]
- Set holdoff time within force_quiescent_state bursts
- in microseconds.
-
- rcutorture.fqs_stutter= [KNL]
- Set wait time between force_quiescent_state bursts
- in seconds.
-
- rcutorture.gp_cond= [KNL]
- Use conditional/asynchronous update-side
- primitives, if available.
-
- rcutorture.gp_exp= [KNL]
- Use expedited update-side primitives, if available.
-
- rcutorture.gp_normal= [KNL]
- Use normal (non-expedited) asynchronous
- update-side primitives, if available.
-
- rcutorture.gp_sync= [KNL]
- Use normal (non-expedited) synchronous
- update-side primitives, if available. If all
- of rcutorture.gp_cond=, rcutorture.gp_exp=,
- rcutorture.gp_normal=, and rcutorture.gp_sync=
- are zero, rcutorture acts as if is interpreted
- they are all non-zero.
-
- rcutorture.n_barrier_cbs= [KNL]
- Set callbacks/threads for rcu_barrier() testing.
-
- rcutorture.nfakewriters= [KNL]
- Set number of concurrent RCU writers. These just
- stress RCU, they don't participate in the actual
- test, hence the "fake".
-
- rcutorture.nreaders= [KNL]
- Set number of RCU readers. The value -1 selects
- N-1, where N is the number of CPUs. A value
- "n" less than -1 selects N-n-2, where N is again
- the number of CPUs. For example, -2 selects N
- (the number of CPUs), -3 selects N+1, and so on.
-
- rcutorture.object_debug= [KNL]
- Enable debug-object double-call_rcu() testing.
-
- rcutorture.onoff_holdoff= [KNL]
- Set time (s) after boot for CPU-hotplug testing.
-
- rcutorture.onoff_interval= [KNL]
- Set time (s) between CPU-hotplug operations, or
- zero to disable CPU-hotplug testing.
-
- rcutorture.shuffle_interval= [KNL]
- Set task-shuffle interval (s). Shuffling tasks
- allows some CPUs to go into dyntick-idle mode
- during the rcutorture test.
-
- rcutorture.shutdown_secs= [KNL]
- Set time (s) after boot system shutdown. This
- is useful for hands-off automated testing.
-
- rcutorture.stall_cpu= [KNL]
- Duration of CPU stall (s) to test RCU CPU stall
- warnings, zero to disable.
-
- rcutorture.stall_cpu_holdoff= [KNL]
- Time to wait (s) after boot before inducing stall.
-
- rcutorture.stat_interval= [KNL]
- Time (s) between statistics printk()s.
-
- rcutorture.stutter= [KNL]
- Time (s) to stutter testing, for example, specifying
- five seconds causes the test to run for five seconds,
- wait for five seconds, and so on. This tests RCU's
- ability to transition abruptly to and from idle.
-
- rcutorture.test_boost= [KNL]
- Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
- "Maybe" means test if the RCU implementation
- under test support RCU priority boosting.
-
- rcutorture.test_boost_duration= [KNL]
- Duration (s) of each individual boost test.
-
- rcutorture.test_boost_interval= [KNL]
- Interval (s) between each boost test.
-
- rcutorture.test_no_idle_hz= [KNL]
- Test RCU's dyntick-idle handling. See also the
- rcutorture.shuffle_interval parameter.
-
- rcutorture.torture_runnable= [BOOT]
- Start rcutorture running at boot time.
-
- rcutorture.torture_type= [KNL]
- Specify the RCU implementation to test.
-
- rcutorture.verbose= [KNL]
- Enable additional printk() statements.
-
- rcupdate.rcu_cpu_stall_suppress= [KNL]
- Suppress RCU CPU stall warning messages.
-
- rcupdate.rcu_cpu_stall_timeout= [KNL]
- Set timeout for RCU CPU stall warning messages.
-
- rcupdate.rcu_expedited= [KNL]
- Use expedited grace-period primitives, for
- example, synchronize_rcu_expedited() instead
- of synchronize_rcu(). This reduces latency,
- but can increase CPU utilization, degrade
- real-time latency, and degrade energy efficiency.
- No effect on CONFIG_TINY_RCU kernels.
-
- rcupdate.rcu_normal= [KNL]
- Use only normal grace-period primitives,
- for example, synchronize_rcu() instead of
- synchronize_rcu_expedited(). This improves
- real-time latency, CPU utilization, and
- energy efficiency, but can expose users to
- increased grace-period latency. This parameter
- overrides rcupdate.rcu_expedited. No effect on
- CONFIG_TINY_RCU kernels.
-
- rcupdate.rcu_normal_after_boot= [KNL]
- Once boot has completed (that is, after
- rcu_end_inkernel_boot() has been invoked), use
- only normal grace-period primitives. No effect
- on CONFIG_TINY_RCU kernels.
-
- rcupdate.rcu_task_stall_timeout= [KNL]
- Set timeout in jiffies for RCU task stall warning
- messages. Disable with a value less than or equal
- to zero.
-
- rcupdate.rcu_self_test= [KNL]
- Run the RCU early boot self tests
-
- rcupdate.rcu_self_test_bh= [KNL]
- Run the RCU bh early boot self tests
-
- rcupdate.rcu_self_test_sched= [KNL]
- Run the RCU sched early boot self tests
-
- rdinit= [KNL]
- Format: <full_path>
- Run specified binary instead of /init from the ramdisk,
- used for early userspace startup. See initrd.
-
- reboot= [KNL]
- Format (x86 or x86_64):
- [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
- [[,]s[mp]#### \
- [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
- [[,]f[orce]
- Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
- reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
- reboot_force is either force or not specified,
- reboot_cpu is s[mp]#### with #### being the processor
- to be used for rebooting.
-
- relax_domain_level=
- [KNL, SMP] Set scheduler's default relax_domain_level.
- See Documentation/cgroup-v1/cpusets.txt.
-
- relative_sleep_states=
- [SUSPEND] Use sleep state labeling where the deepest
- state available other than hibernation is always "mem".
- Format: { "0" | "1" }
- 0 -- Traditional sleep state labels.
- 1 -- Relative sleep state labels.
-
- reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
-
- reservetop= [X86-32]
- Format: nn[KMG]
- Reserves a hole at the top of the kernel virtual
- address space.
-
- reservelow= [X86]
- Format: nn[K]
- Set the amount of memory to reserve for BIOS at
- the bottom of the address space.
-
- reset_devices [KNL] Force drivers to reset the underlying device
- during initialization.
-
- resume= [SWSUSP]
- Specify the partition device for software suspend
- Format:
- {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
-
- resume_offset= [SWSUSP]
- Specify the offset from the beginning of the partition
- given by "resume=" at which the swap header is located,
- in <PAGE_SIZE> units (needed only for swap files).
- See Documentation/power/swsusp-and-swap-files.txt
-
- resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
- read the resume files
-
- resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
- Useful for devices that are detected asynchronously
- (e.g. USB and MMC devices).
-
- hibernate= [HIBERNATION]
- noresume Don't check if there's a hibernation image
- present during boot.
- nocompress Don't compress/decompress hibernation images.
- no Disable hibernation and resume.
- protect_image Turn on image protection during restoration
- (that will set all pages holding image data
- during restoration read-only).
-
- retain_initrd [RAM] Keep initrd memory after extraction
-
- rfkill.default_state=
- 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
- etc. communication is blocked by default.
- 1 Unblocked.
-
- rfkill.master_switch_mode=
- 0 The "airplane mode" button does nothing.
- 1 The "airplane mode" button toggles between everything
- blocked and the previous configuration.
- 2 The "airplane mode" button toggles between everything
- blocked and everything unblocked.
-
- rhash_entries= [KNL,NET]
- Set number of hash buckets for route cache
-
- ro [KNL] Mount root device read-only on boot
-
- rodata= [KNL]
- on Mark read-only kernel memory as read-only (default).
- off Leave read-only kernel memory writable for debugging.
-
- rockchip.usb_uart
- Enable the uart passthrough on the designated usb port
- on Rockchip SoCs. When active, the signals of the
- debug-uart get routed to the D+ and D- pins of the usb
- port and the regular usb controller gets disabled.
-
- root= [KNL] Root filesystem
- See name_to_dev_t comment in init/do_mounts.c.
-
- rootdelay= [KNL] Delay (in seconds) to pause before attempting to
- mount the root filesystem
-
- rootflags= [KNL] Set root filesystem mount option string
-
- rootfstype= [KNL] Set root filesystem type
-
- rootwait [KNL] Wait (indefinitely) for root device to show up.
- Useful for devices that are detected asynchronously
- (e.g. USB and MMC devices).
-
- rproc_mem=nn[KMG][@address]
- [KNL,ARM,CMA] Remoteproc physical memory block.
- Memory area to be used by remote processor image,
- managed by CMA.
-
- rw [KNL] Mount root device read-write on boot
-
- S [KNL] Run init in single mode
-
- s390_iommu= [HW,S390]
- Set s390 IOTLB flushing mode
- strict
- With strict flushing every unmap operation will result in
- an IOTLB flush. Default is lazy flushing before reuse,
- which is faster.
-
- sa1100ir [NET]
- See drivers/net/irda/sa1100_ir.c.
-
- sbni= [NET] Granch SBNI12 leased line adapter
-
- sched_debug [KNL] Enables verbose scheduler debug messages.
-
- schedstats= [KNL,X86] Enable or disable scheduled statistics.
- Allowed values are enable and disable. This feature
- incurs a small amount of overhead in the scheduler
- but is useful for debugging and performance tuning.
-
- skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
- xtime_lock contention on larger systems, and/or RCU lock
- contention on all systems with CONFIG_MAXSMP set.
- Format: { "0" | "1" }
- 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
- 1 -- enable.
- Note: increases power consumption, thus should only be
- enabled if running jitter sensitive (HPC/RT) workloads.
-
- security= [SECURITY] Choose a security module to enable at boot.
- If this boot parameter is not specified, only the first
- security module asking for security registration will be
- loaded. An invalid security module name will be treated
- as if no module has been chosen.
-
- selinux= [SELINUX] Disable or enable SELinux at boot time.
- Format: { "0" | "1" }
- See security/selinux/Kconfig help text.
- 0 -- disable.
- 1 -- enable.
- Default value is set via kernel config option.
- If enabled at boot time, /selinux/disable can be used
- later to disable prior to initial policy load.
-
- apparmor= [APPARMOR] Disable or enable AppArmor at boot time
- Format: { "0" | "1" }
- See security/apparmor/Kconfig help text
- 0 -- disable.
- 1 -- enable.
- Default value is set via kernel config option.
-
- serialnumber [BUGS=X86-32]
-
- shapers= [NET]
- Maximal number of shapers.
-
- show_msr= [x86] show boot-time MSR settings
- Format: { <integer> }
- Show boot-time (BIOS-initialized) MSR settings.
- The parameter means the number of CPUs to show,
- for example 1 means boot CPU only.
-
- simeth= [IA-64]
- simscsi=
-
- slram= [HW,MTD]
-
- slab_nomerge [MM]
- Disable merging of slabs with similar size. May be
- necessary if there is some reason to distinguish
- allocs to different slabs. Debug options disable
- merging on their own.
- For more information see Documentation/vm/slub.txt.
-
- slab_max_order= [MM, SLAB]
- Determines the maximum allowed order for slabs.
- A high setting may cause OOMs due to memory
- fragmentation. Defaults to 1 for systems with
- more than 32MB of RAM, 0 otherwise.
-
- slub_debug[=options[,slabs]] [MM, SLUB]
- Enabling slub_debug allows one to determine the
- culprit if slab objects become corrupted. Enabling
- slub_debug can create guard zones around objects and
- may poison objects when not in use. Also tracks the
- last alloc / free. For more information see
- Documentation/vm/slub.txt.
-
- slub_max_order= [MM, SLUB]
- Determines the maximum allowed order for slabs.
- A high setting may cause OOMs due to memory
- fragmentation. For more information see
- Documentation/vm/slub.txt.
-
- slub_min_objects= [MM, SLUB]
- The minimum number of objects per slab. SLUB will
- increase the slab order up to slub_max_order to
- generate a sufficiently large slab able to contain
- the number of objects indicated. The higher the number
- of objects the smaller the overhead of tracking slabs
- and the less frequently locks need to be acquired.
- For more information see Documentation/vm/slub.txt.
-
- slub_min_order= [MM, SLUB]
- Determines the minimum page order for slabs. Must be
- lower than slub_max_order.
- For more information see Documentation/vm/slub.txt.
-
- slub_nomerge [MM, SLUB]
- Same with slab_nomerge. This is supported for legacy.
- See slab_nomerge for more information.
-
- smart2= [HW]
- Format: <io1>[,<io2>[,...,<io8>]]
-
- smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
- smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
- smsc-ircc2.ircc_sir= [HW] SIR base I/O port
- smsc-ircc2.ircc_fir= [HW] FIR base I/O port
- smsc-ircc2.ircc_irq= [HW] IRQ line
- smsc-ircc2.ircc_dma= [HW] DMA channel
- smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
- 0: Toshiba Satellite 1800 (GP data pin select)
- 1: Fast pin select (default)
- 2: ATC IRMode
-
- smt [KNL,S390] Set the maximum number of threads (logical
- CPUs) to use per physical CPU on systems capable of
- symmetric multithreading (SMT). Will be capped to the
- actual hardware limit.
- Format: <integer>
- Default: -1 (no limit)
-
- softlockup_panic=
- [KNL] Should the soft-lockup detector generate panics.
- Format: <integer>
-
- softlockup_all_cpu_backtrace=
- [KNL] Should the soft-lockup detector generate
- backtraces on all cpus.
- Format: <integer>
-
- sonypi.*= [HW] Sony Programmable I/O Control Device driver
- See Documentation/laptops/sonypi.txt
-
- spia_io_base= [HW,MTD]
- spia_fio_base=
- spia_pedr=
- spia_peddr=
-
- stacktrace [FTRACE]
- Enabled the stack tracer on boot up.
-
- stacktrace_filter=[function-list]
- [FTRACE] Limit the functions that the stack tracer
- will trace at boot up. function-list is a comma separated
- list of functions. This list can be changed at run
- time by the stack_trace_filter file in the debugfs
- tracing directory. Note, this enables stack tracing
- and the stacktrace above is not needed.
-
- sti= [PARISC,HW]
- Format: <num>
- Set the STI (builtin display/keyboard on the HP-PARISC
- machines) console (graphic card) which should be used
- as the initial boot-console.
- See also comment in drivers/video/console/sticore.c.
-
- sti_font= [HW]
- See comment in drivers/video/console/sticore.c.
-
- stifb= [HW]
- Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
-
- sunrpc.min_resvport=
- sunrpc.max_resvport=
- [NFS,SUNRPC]
- SunRPC servers often require that client requests
- originate from a privileged port (i.e. a port in the
- range 0 < portnr < 1024).
- An administrator who wishes to reserve some of these
- ports for other uses may adjust the range that the
- kernel's sunrpc client considers to be privileged
- using these two parameters to set the minimum and
- maximum port values.
-
- sunrpc.svc_rpc_per_connection_limit=
- [NFS,SUNRPC]
- Limit the number of requests that the server will
- process in parallel from a single connection.
- The default value is 0 (no limit).
-
- sunrpc.pool_mode=
- [NFS]
- Control how the NFS server code allocates CPUs to
- service thread pools. Depending on how many NICs
- you have and where their interrupts are bound, this
- option will affect which CPUs will do NFS serving.
- Note: this parameter cannot be changed while the
- NFS server is running.
-
- auto the server chooses an appropriate mode
- automatically using heuristics
- global a single global pool contains all CPUs
- percpu one pool for each CPU
- pernode one pool for each NUMA node (equivalent
- to global on non-NUMA machines)
-
- sunrpc.tcp_slot_table_entries=
- sunrpc.udp_slot_table_entries=
- [NFS,SUNRPC]
- Sets the upper limit on the number of simultaneous
- RPC calls that can be sent from the client to a
- server. Increasing these values may allow you to
- improve throughput, but will also increase the
- amount of memory reserved for use by the client.
-
- suspend.pm_test_delay=
- [SUSPEND]
- Sets the number of seconds to remain in a suspend test
- mode before resuming the system (see
- /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
- is set. Default value is 5.
-
- swapaccount=[0|1]
- [KNL] Enable accounting of swap in memory resource
- controller if no parameter or 1 is given or disable
- it if 0 is given (See Documentation/cgroup-v1/memory.txt)
-
- swiotlb= [ARM,IA-64,PPC,MIPS,X86]
- Format: { <int> | force }
- <int> -- Number of I/O TLB slabs
- force -- force using of bounce buffers even if they
- wouldn't be automatically used by the kernel
-
- switches= [HW,M68k]
-
- sysfs.deprecated=0|1 [KNL]
- Enable/disable old style sysfs layout for old udev
- on older distributions. When this option is enabled
- very new udev will not work anymore. When this option
- is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
- in older udev will not work anymore.
- Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
- the kernel configuration.
-
- sysrq_always_enabled
- [KNL]
- Ignore sysrq setting - this boot parameter will
- neutralize any effect of /proc/sys/kernel/sysrq.
- Useful for debugging.
-
- tcpmhash_entries= [KNL,NET]
- Set the number of tcp_metrics_hash slots.
- Default value is 8192 or 16384 depending on total
- ram pages. This is used to specify the TCP metrics
- cache size. See Documentation/networking/ip-sysctl.txt
- "tcp_no_metrics_save" section for more details.
-
- tdfx= [HW,DRM]
-
- test_suspend= [SUSPEND][,N]
- Specify "mem" (for Suspend-to-RAM) or "standby" (for
- standby suspend) or "freeze" (for suspend type freeze)
- as the system sleep state during system startup with
- the optional capability to repeat N number of times.
- The system is woken from this state using a
- wakeup-capable RTC alarm.
-
- thash_entries= [KNL,NET]
- Set number of hash buckets for TCP connection
-
- thermal.act= [HW,ACPI]
- -1: disable all active trip points in all thermal zones
- <degrees C>: override all lowest active trip points
-
- thermal.crt= [HW,ACPI]
- -1: disable all critical trip points in all thermal zones
- <degrees C>: override all critical trip points
-
- thermal.nocrt= [HW,ACPI]
- Set to disable actions on ACPI thermal zone
- critical and hot trip points.
-
- thermal.off= [HW,ACPI]
- 1: disable ACPI thermal control
-
- thermal.psv= [HW,ACPI]
- -1: disable all passive trip points
- <degrees C>: override all passive trip points to this
- value
-
- thermal.tzp= [HW,ACPI]
- Specify global default ACPI thermal zone polling rate
- <deci-seconds>: poll all this frequency
- 0: no polling (default)
-
- threadirqs [KNL]
- Force threading of all interrupt handlers except those
- marked explicitly IRQF_NO_THREAD.
-
- tmem [KNL,XEN]
- Enable the Transcendent memory driver if built-in.
-
- tmem.cleancache=0|1 [KNL, XEN]
- Default is on (1). Disable the usage of the cleancache
- API to send anonymous pages to the hypervisor.
-
- tmem.frontswap=0|1 [KNL, XEN]
- Default is on (1). Disable the usage of the frontswap
- API to send swap pages to the hypervisor. If disabled
- the selfballooning and selfshrinking are force disabled.
-
- tmem.selfballooning=0|1 [KNL, XEN]
- Default is on (1). Disable the driving of swap pages
- to the hypervisor.
-
- tmem.selfshrinking=0|1 [KNL, XEN]
- Default is on (1). Partial swapoff that immediately
- transfers pages from Xen hypervisor back to the
- kernel based on different criteria.
-
- topology= [S390]
- Format: {off | on}
- Specify if the kernel should make use of the cpu
- topology information if the hardware supports this.
- The scheduler will make use of this information and
- e.g. base its process migration decisions on it.
- Default is on.
-
- topology_updates= [KNL, PPC, NUMA]
- Format: {off}
- Specify if the kernel should ignore (off)
- topology updates sent by the hypervisor to this
- LPAR.
-
- tp720= [HW,PS2]
-
- tpm_suspend_pcr=[HW,TPM]
- Format: integer pcr id
- Specify that at suspend time, the tpm driver
- should extend the specified pcr with zeros,
- as a workaround for some chips which fail to
- flush the last written pcr on TPM_SaveState.
- This will guarantee that all the other pcrs
- are saved.
-
- trace_buf_size=nn[KMG]
- [FTRACE] will set tracing buffer size on each cpu.
-
- trace_event=[event-list]
- [FTRACE] Set and start specified trace events in order
- to facilitate early boot debugging. The event-list is a
- comma separated list of trace events to enable. See
- also Documentation/trace/events.txt
-
- trace_options=[option-list]
- [FTRACE] Enable or disable tracer options at boot.
- The option-list is a comma delimited list of options
- that can be enabled or disabled just as if you were
- to echo the option name into
-
- /sys/kernel/debug/tracing/trace_options
-
- For example, to enable stacktrace option (to dump the
- stack trace of each event), add to the command line:
-
- trace_options=stacktrace
-
- See also Documentation/trace/ftrace.txt "trace options"
- section.
-
- tp_printk[FTRACE]
- Have the tracepoints sent to printk as well as the
- tracing ring buffer. This is useful for early boot up
- where the system hangs or reboots and does not give the
- option for reading the tracing buffer or performing a
- ftrace_dump_on_oops.
-
- To turn off having tracepoints sent to printk,
- echo 0 > /proc/sys/kernel/tracepoint_printk
- Note, echoing 1 into this file without the
- tracepoint_printk kernel cmdline option has no effect.
-
- ** CAUTION **
-
- Having tracepoints sent to printk() and activating high
- frequency tracepoints such as irq or sched, can cause
- the system to live lock.
-
- traceoff_on_warning
- [FTRACE] enable this option to disable tracing when a
- warning is hit. This turns off "tracing_on". Tracing can
- be enabled again by echoing '1' into the "tracing_on"
- file located in /sys/kernel/debug/tracing/
-
- This option is useful, as it disables the trace before
- the WARNING dump is called, which prevents the trace to
- be filled with content caused by the warning output.
-
- This option can also be set at run time via the sysctl
- option: kernel/traceoff_on_warning
-
- transparent_hugepage=
- [KNL]
- Format: [always|madvise|never]
- Can be used to control the default behavior of the system
- with respect to transparent hugepages.
- See Documentation/vm/transhuge.txt for more details.
-
- tsc= Disable clocksource stability checks for TSC.
- Format: <string>
- [x86] reliable: mark tsc clocksource as reliable, this
- disables clocksource verification at runtime, as well
- as the stability checks done at bootup. Used to enable
- high-resolution timer mode on older hardware, and in
- virtualized environment.
- [x86] noirqtime: Do not use TSC to do irq accounting.
- Used to run time disable IRQ_TIME_ACCOUNTING on any
- platforms where RDTSC is slow and this accounting
- can add overhead.
-
- turbografx.map[2|3]= [HW,JOY]
- TurboGraFX parallel port interface
- Format:
- <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
- See also Documentation/input/joystick-parport.txt
-
- udbg-immortal [PPC] When debugging early kernel crashes that
- happen after console_init() and before a proper
- console driver takes over, this boot options might
- help "seeing" what's going on.
-
- uhash_entries= [KNL,NET]
- Set number of hash buckets for UDP/UDP-Lite connections
-
- uhci-hcd.ignore_oc=
- [USB] Ignore overcurrent events (default N).
- Some badly-designed motherboards generate lots of
- bogus events, for ports that aren't wired to
- anything. Set this parameter to avoid log spamming.
- Note that genuine overcurrent events won't be
- reported either.
-
- unknown_nmi_panic
- [X86] Cause panic on unknown NMI.
-
- usbcore.authorized_default=
- [USB] Default USB device authorization:
- (default -1 = authorized except for wireless USB,
- 0 = not authorized, 1 = authorized)
-
- usbcore.autosuspend=
- [USB] The autosuspend time delay (in seconds) used
- for newly-detected USB devices (default 2). This
- is the time required before an idle device will be
- autosuspended. Devices for which the delay is set
- to a negative value won't be autosuspended at all.
-
- usbcore.usbfs_snoop=
- [USB] Set to log all usbfs traffic (default 0 = off).
-
- usbcore.usbfs_snoop_max=
- [USB] Maximum number of bytes to snoop in each URB
- (default = 65536).
-
- usbcore.blinkenlights=
- [USB] Set to cycle leds on hubs (default 0 = off).
-
- usbcore.old_scheme_first=
- [USB] Start with the old device initialization
- scheme (default 0 = off).
-
- usbcore.usbfs_memory_mb=
- [USB] Memory limit (in MB) for buffers allocated by
- usbfs (default = 16, 0 = max = 2047).
-
- usbcore.use_both_schemes=
- [USB] Try the other device initialization scheme
- if the first one fails (default 1 = enabled).
-
- usbcore.initial_descriptor_timeout=
- [USB] Specifies timeout for the initial 64-byte
- USB_REQ_GET_DESCRIPTOR request in milliseconds
- (default 5000 = 5.0 seconds).
-
- usbcore.nousb [USB] Disable the USB subsystem
-
- usbhid.mousepoll=
- [USBHID] The interval which mice are to be polled at.
-
- usb-storage.delay_use=
- [UMS] The delay in seconds before a new device is
- scanned for Logical Units (default 1).
-
- usb-storage.quirks=
- [UMS] A list of quirks entries to supplement or
- override the built-in unusual_devs list. List
- entries are separated by commas. Each entry has
- the form VID:PID:Flags where VID and PID are Vendor
- and Product ID values (4-digit hex numbers) and
- Flags is a set of characters, each corresponding
- to a common usb-storage quirk flag as follows:
- a = SANE_SENSE (collect more than 18 bytes
- of sense data);
- b = BAD_SENSE (don't collect more than 18
- bytes of sense data);
- c = FIX_CAPACITY (decrease the reported
- device capacity by one sector);
- d = NO_READ_DISC_INFO (don't use
- READ_DISC_INFO command);
- e = NO_READ_CAPACITY_16 (don't use
- READ_CAPACITY_16 command);
- f = NO_REPORT_OPCODES (don't use report opcodes
- command, uas only);
- g = MAX_SECTORS_240 (don't transfer more than
- 240 sectors at a time, uas only);
- h = CAPACITY_HEURISTICS (decrease the
- reported device capacity by one
- sector if the number is odd);
- i = IGNORE_DEVICE (don't bind to this
- device);
- j = NO_REPORT_LUNS (don't use report luns
- command, uas only);
- l = NOT_LOCKABLE (don't try to lock and
- unlock ejectable media);
- m = MAX_SECTORS_64 (don't transfer more
- than 64 sectors = 32 KB at a time);
- n = INITIAL_READ10 (force a retry of the
- initial READ(10) command);
- o = CAPACITY_OK (accept the capacity
- reported by the device);
- p = WRITE_CACHE (the device cache is ON
- by default);
- r = IGNORE_RESIDUE (the device reports
- bogus residue values);
- s = SINGLE_LUN (the device has only one
- Logical Unit);
- t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
- commands, uas only);
- u = IGNORE_UAS (don't bind to the uas driver);
- w = NO_WP_DETECT (don't test whether the
- medium is write-protected).
- y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
- even if the device claims no cache)
- Example: quirks=0419:aaf5:rl,0421:0433:rc
-
- user_debug= [KNL,ARM]
- Format: <int>
- See arch/arm/Kconfig.debug help text.
- 1 - undefined instruction events
- 2 - system calls
- 4 - invalid data aborts
- 8 - SIGSEGV faults
- 16 - SIGBUS faults
- Example: user_debug=31
-
- userpte=
- [X86] Flags controlling user PTE allocations.
-
- nohigh = do not allocate PTE pages in
- HIGHMEM regardless of setting
- of CONFIG_HIGHPTE.
-
- vdso= [X86,SH]
- On X86_32, this is an alias for vdso32=. Otherwise:
-
- vdso=1: enable VDSO (the default)
- vdso=0: disable VDSO mapping
-
- vdso32= [X86] Control the 32-bit vDSO
- vdso32=1: enable 32-bit VDSO
- vdso32=0 or vdso32=2: disable 32-bit VDSO
-
- See the help text for CONFIG_COMPAT_VDSO for more
- details. If CONFIG_COMPAT_VDSO is set, the default is
- vdso32=0; otherwise, the default is vdso32=1.
-
- For compatibility with older kernels, vdso32=2 is an
- alias for vdso32=0.
-
- Try vdso32=0 if you encounter an error that says:
- dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
-
- vector= [IA-64,SMP]
- vector=percpu: enable percpu vector domain
-
- video= [FB] Frame buffer configuration
- See Documentation/fb/modedb.txt.
-
- video.brightness_switch_enabled= [0,1]
- If set to 1, on receiving an ACPI notify event
- generated by hotkey, video driver will adjust brightness
- level and then send out the event to user space through
- the allocated input device; If set to 0, video driver
- will only send out the event without touching backlight
- brightness level.
- default: 1
-
- virtio_mmio.device=
- [VMMIO] Memory mapped virtio (platform) device.
-
- <size>@<baseaddr>:<irq>[:<id>]
- where:
- <size> := size (can use standard suffixes
- like K, M and G)
- <baseaddr> := physical base address
- <irq> := interrupt number (as passed to
- request_irq())
- <id> := (optional) platform device id
- example:
- virtio_mmio.device=1K@0x100b0000:48:7
-
- Can be used multiple times for multiple devices.
-
- vga= [BOOT,X86-32] Select a particular video mode
- See Documentation/x86/boot.txt and
- Documentation/svga.txt.
- Use vga=ask for menu.
- This is actually a boot loader parameter; the value is
- passed to the kernel using a special protocol.
-
- vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
- size of <nn>. This can be used to increase the
- minimum size (128MB on x86). It can also be used to
- decrease the size and leave more room for directly
- mapped kernel RAM.
-
- vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
- Format: <command>
-
- vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
- Format: <command>
-
- vmpoff= [KNL,S390] Perform z/VM CP command after power off.
- Format: <command>
-
- vsyscall= [X86-64]
- Controls the behavior of vsyscalls (i.e. calls to
- fixed addresses of 0xffffffffff600x00 from legacy
- code). Most statically-linked binaries and older
- versions of glibc use these calls. Because these
- functions are at fixed addresses, they make nice
- targets for exploits that can control RIP.
-
- emulate [default] Vsyscalls turn into traps and are
- emulated reasonably safely.
-
- native Vsyscalls are native syscall instructions.
- This is a little bit faster than trapping
- and makes a few dynamic recompilers work
- better than they would in emulation mode.
- It also makes exploits much easier to write.
-
- none Vsyscalls don't work at all. This makes
- them quite hard to use for exploits but
- might break your system.
-
- vt.color= [VT] Default text color.
- Format: 0xYX, X = foreground, Y = background.
- Default: 0x07 = light gray on black.
-
- vt.cur_default= [VT] Default cursor shape.
- Format: 0xCCBBAA, where AA, BB, and CC are the same as
- the parameters of the <Esc>[?A;B;Cc escape sequence;
- see VGA-softcursor.txt. Default: 2 = underline.
-
- vt.default_blu= [VT]
- Format: <blue0>,<blue1>,<blue2>,...,<blue15>
- Change the default blue palette of the console.
- This is a 16-member array composed of values
- ranging from 0-255.
-
- vt.default_grn= [VT]
- Format: <green0>,<green1>,<green2>,...,<green15>
- Change the default green palette of the console.
- This is a 16-member array composed of values
- ranging from 0-255.
-
- vt.default_red= [VT]
- Format: <red0>,<red1>,<red2>,...,<red15>
- Change the default red palette of the console.
- This is a 16-member array composed of values
- ranging from 0-255.
-
- vt.default_utf8=
- [VT]
- Format=<0|1>
- Set system-wide default UTF-8 mode for all tty's.
- Default is 1, i.e. UTF-8 mode is enabled for all
- newly opened terminals.
-
- vt.global_cursor_default=
- [VT]
- Format=<-1|0|1>
- Set system-wide default for whether a cursor
- is shown on new VTs. Default is -1,
- i.e. cursors will be created by default unless
- overridden by individual drivers. 0 will hide
- cursors, 1 will display them.
-
- vt.italic= [VT] Default color for italic text; 0-15.
- Default: 2 = green.
-
- vt.underline= [VT] Default color for underlined text; 0-15.
- Default: 3 = cyan.
-
- watchdog timers [HW,WDT] For information on watchdog timers,
- see Documentation/watchdog/watchdog-parameters.txt
- or other driver-specific files in the
- Documentation/watchdog/ directory.
-
- workqueue.watchdog_thresh=
- If CONFIG_WQ_WATCHDOG is configured, workqueue can
- warn stall conditions and dump internal state to
- help debugging. 0 disables workqueue stall
- detection; otherwise, it's the stall threshold
- duration in seconds. The default value is 30 and
- it can be updated at runtime by writing to the
- corresponding sysfs file.
-
- workqueue.disable_numa
- By default, all work items queued to unbound
- workqueues are affine to the NUMA nodes they're
- issued on, which results in better behavior in
- general. If NUMA affinity needs to be disabled for
- whatever reason, this option can be used. Note
- that this also can be controlled per-workqueue for
- workqueues visible under /sys/bus/workqueue/.
-
- workqueue.power_efficient
- Per-cpu workqueues are generally preferred because
- they show better performance thanks to cache
- locality; unfortunately, per-cpu workqueues tend to
- be more power hungry than unbound workqueues.
-
- Enabling this makes the per-cpu workqueues which
- were observed to contribute significantly to power
- consumption unbound, leading to measurably lower
- power usage at the cost of small performance
- overhead.
-
- The default value of this parameter is determined by
- the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
-
- workqueue.debug_force_rr_cpu
- Workqueue used to implicitly guarantee that work
- items queued without explicit CPU specified are put
- on the local CPU. This guarantee is no longer true
- and while local CPU is still preferred work items
- may be put on foreign CPUs. This debug option
- forces round-robin CPU selection to flush out
- usages which depend on the now broken guarantee.
- When enabled, memory and cache locality will be
- impacted.
-
- x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
- default x2apic cluster mode on platforms
- supporting x2apic.
-
- x86_intel_mid_timer= [X86-32,APBT]
- Choose timer option for x86 Intel MID platform.
- Two valid options are apbt timer only and lapic timer
- plus one apbt timer for broadcast timer.
- x86_intel_mid_timer=apbt_only | lapic_and_apbt
-
- xen_512gb_limit [KNL,X86-64,XEN]
- Restricts the kernel running paravirtualized under Xen
- to use only up to 512 GB of RAM. The reason to do so is
- crash analysis tools and Xen tools for doing domain
- save/restore/migration must be enabled to handle larger
- domains.
-
- xen_emul_unplug= [HW,X86,XEN]
- Unplug Xen emulated devices
- Format: [unplug0,][unplug1]
- ide-disks -- unplug primary master IDE devices
- aux-ide-disks -- unplug non-primary-master IDE devices
- nics -- unplug network devices
- all -- unplug all emulated devices (NICs and IDE disks)
- unnecessary -- unplugging emulated devices is
- unnecessary even if the host did not respond to
- the unplug protocol
- never -- do not unplug even if version check succeeds
-
- xen_nopvspin [X86,XEN]
- Disables the ticketlock slowpath using Xen PV
- optimizations.
-
- xen_nopv [X86]
- Disables the PV optimizations forcing the HVM guest to
- run as generic HVM guest with no PV drivers.
-
- xirc2ps_cs= [NET,PCMCIA]
- Format:
- <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
-
-------------------------
+.. include:: kernel-parameters.txt
+ :literal:
Todo
----
--- /dev/null
+ acpi= [HW,ACPI,X86,ARM64]
+ Advanced Configuration and Power Interface
+ Format: { force | on | off | strict | noirq | rsdt |
+ copy_dsdt }
+ force -- enable ACPI if default was off
+ on -- enable ACPI but allow fallback to DT [arm64]
+ off -- disable ACPI if default was on
+ noirq -- do not use ACPI for IRQ routing
+ strict -- Be less tolerant of platforms that are not
+ strictly ACPI specification compliant.
+ rsdt -- prefer RSDT over (default) XSDT
+ copy_dsdt -- copy DSDT to memory
+ For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
+ are available
+
+ See also Documentation/power/runtime_pm.txt, pci=noacpi
+
+ acpi_apic_instance= [ACPI, IOAPIC]
+ Format: <int>
+ 2: use 2nd APIC table, if available
+ 1,0: use 1st APIC table
+ default: 0
+
+ acpi_backlight= [HW,ACPI]
+ acpi_backlight=vendor
+ acpi_backlight=video
+ If set to vendor, prefer vendor specific driver
+ (e.g. thinkpad_acpi, sony_acpi, etc.) instead
+ of the ACPI video.ko driver.
+
+ acpi_force_32bit_fadt_addr
+ force FADT to use 32 bit addresses rather than the
+ 64 bit X_* addresses. Some firmware have broken 64
+ bit addresses for force ACPI ignore these and use
+ the older legacy 32 bit addresses.
+
+ acpica_no_return_repair [HW, ACPI]
+ Disable AML predefined validation mechanism
+ This mechanism can repair the evaluation result to make
+ the return objects more ACPI specification compliant.
+ This option is useful for developers to identify the
+ root cause of an AML interpreter issue when the issue
+ has something to do with the repair mechanism.
+
+ acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
+ acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
+ Format: <int>
+ CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
+ debug output. Bits in debug_layer correspond to a
+ _COMPONENT in an ACPI source file, e.g.,
+ #define _COMPONENT ACPI_PCI_COMPONENT
+ Bits in debug_level correspond to a level in
+ ACPI_DEBUG_PRINT statements, e.g.,
+ ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
+ The debug_level mask defaults to "info". See
+ Documentation/acpi/debug.txt for more information about
+ debug layers and levels.
+
+ Enable processor driver info messages:
+ acpi.debug_layer=0x20000000
+ Enable PCI/PCI interrupt routing info messages:
+ acpi.debug_layer=0x400000
+ Enable AML "Debug" output, i.e., stores to the Debug
+ object while interpreting AML:
+ acpi.debug_layer=0xffffffff acpi.debug_level=0x2
+ Enable all messages related to ACPI hardware:
+ acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
+
+ Some values produce so much output that the system is
+ unusable. The "log_buf_len" parameter may be useful
+ if you need to capture more output.
+
+ acpi_enforce_resources= [ACPI]
+ { strict | lax | no }
+ Check for resource conflicts between native drivers
+ and ACPI OperationRegions (SystemIO and SystemMemory
+ only). IO ports and memory declared in ACPI might be
+ used by the ACPI subsystem in arbitrary AML code and
+ can interfere with legacy drivers.
+ strict (default): access to resources claimed by ACPI
+ is denied; legacy drivers trying to access reserved
+ resources will fail to bind to device using them.
+ lax: access to resources claimed by ACPI is allowed;
+ legacy drivers trying to access reserved resources
+ will bind successfully but a warning message is logged.
+ no: ACPI OperationRegions are not marked as reserved,
+ no further checks are performed.
+
+ acpi_force_table_verification [HW,ACPI]
+ Enable table checksum verification during early stage.
+ By default, this is disabled due to x86 early mapping
+ size limitation.
+
+ acpi_irq_balance [HW,ACPI]
+ ACPI will balance active IRQs
+ default in APIC mode
+
+ acpi_irq_nobalance [HW,ACPI]
+ ACPI will not move active IRQs (default)
+ default in PIC mode
+
+ acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
+ Format: <irq>,<irq>...
+
+ acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
+ use by PCI
+ Format: <irq>,<irq>...
+
+ acpi_no_auto_serialize [HW,ACPI]
+ Disable auto-serialization of AML methods
+ AML control methods that contain the opcodes to create
+ named objects will be marked as "Serialized" by the
+ auto-serialization feature.
+ This feature is enabled by default.
+ This option allows to turn off the feature.
+
+ acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
+ kernels.
+
+ acpi_no_static_ssdt [HW,ACPI]
+ Disable installation of static SSDTs at early boot time
+ By default, SSDTs contained in the RSDT/XSDT will be
+ installed automatically and they will appear under
+ /sys/firmware/acpi/tables.
+ This option turns off this feature.
+ Note that specifying this option does not affect
+ dynamic table installation which will install SSDT
+ tables to /sys/firmware/acpi/tables/dynamic.
+
+ acpi_rsdp= [ACPI,EFI,KEXEC]
+ Pass the RSDP address to the kernel, mostly used
+ on machines running EFI runtime service to boot the
+ second kernel for kdump.
+
+ acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
+ Format: To spoof as Windows 98: ="Microsoft Windows"
+
+ acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
+ of 2 which is mandated by ACPI 6) as the supported ACPI
+ specification revision (when using this switch, it may
+ be necessary to carry out a cold reboot _twice_ in a
+ row to make it take effect on the platform firmware).
+
+ acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
+ acpi_osi="string1" # add string1
+ acpi_osi="!string2" # remove string2
+ acpi_osi=!* # remove all strings
+ acpi_osi=! # disable all built-in OS vendor
+ strings
+ acpi_osi=!! # enable all built-in OS vendor
+ strings
+ acpi_osi= # disable all strings
+
+ 'acpi_osi=!' can be used in combination with single or
+ multiple 'acpi_osi="string1"' to support specific OS
+ vendor string(s). Note that such command can only
+ affect the default state of the OS vendor strings, thus
+ it cannot affect the default state of the feature group
+ strings and the current state of the OS vendor strings,
+ specifying it multiple times through kernel command line
+ is meaningless. This command is useful when one do not
+ care about the state of the feature group strings which
+ should be controlled by the OSPM.
+ Examples:
+ 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
+ to 'acpi_osi="Windows 2000" acpi_osi=!', they all
+ can make '_OSI("Windows 2000")' TRUE.
+
+ 'acpi_osi=' cannot be used in combination with other
+ 'acpi_osi=' command lines, the _OSI method will not
+ exist in the ACPI namespace. NOTE that such command can
+ only affect the _OSI support state, thus specifying it
+ multiple times through kernel command line is also
+ meaningless.
+ Examples:
+ 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
+ FALSE.
+
+ 'acpi_osi=!*' can be used in combination with single or
+ multiple 'acpi_osi="string1"' to support specific
+ string(s). Note that such command can affect the
+ current state of both the OS vendor strings and the
+ feature group strings, thus specifying it multiple times
+ through kernel command line is meaningful. But it may
+ still not able to affect the final state of a string if
+ there are quirks related to this string. This command
+ is useful when one want to control the state of the
+ feature group strings to debug BIOS issues related to
+ the OSPM features.
+ Examples:
+ 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
+ '_OSI("Module Device")' FALSE.
+ 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
+ '_OSI("Module Device")' TRUE.
+ 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
+ equivalent to
+ 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
+ and
+ 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
+ they all will make '_OSI("Windows 2000")' TRUE.
+
+ acpi_pm_good [X86]
+ Override the pmtimer bug detection: force the kernel
+ to assume that this machine's pmtimer latches its value
+ and always returns good values.
+
+ acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
+ Format: { level | edge | high | low }
+
+ acpi_skip_timer_override [HW,ACPI]
+ Recognize and ignore IRQ0/pin2 Interrupt Override.
+ For broken nForce2 BIOS resulting in XT-PIC timer.
+
+ acpi_sleep= [HW,ACPI] Sleep options
+ Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
+ old_ordering, nonvs, sci_force_enable }
+ See Documentation/power/video.txt for information on
+ s3_bios and s3_mode.
+ s3_beep is for debugging; it makes the PC's speaker beep
+ as soon as the kernel's real-mode entry point is called.
+ s4_nohwsig prevents ACPI hardware signature from being
+ used during resume from hibernation.
+ old_ordering causes the ACPI 1.0 ordering of the _PTS
+ control method, with respect to putting devices into
+ low power states, to be enforced (the ACPI 2.0 ordering
+ of _PTS is used by default).
+ nonvs prevents the kernel from saving/restoring the
+ ACPI NVS memory during suspend/hibernation and resume.
+ sci_force_enable causes the kernel to set SCI_EN directly
+ on resume from S1/S3 (which is against the ACPI spec,
+ but some broken systems don't work without it).
+
+ acpi_use_timer_override [HW,ACPI]
+ Use timer override. For some broken Nvidia NF5 boards
+ that require a timer override, but don't have HPET
+
+ add_efi_memmap [EFI; X86] Include EFI memory map in
+ kernel's map of available physical RAM.
+
+ agp= [AGP]
+ { off | try_unsupported }
+ off: disable AGP support
+ try_unsupported: try to drive unsupported chipsets
+ (may crash computer or cause data corruption)
+
+ ALSA [HW,ALSA]
+ See Documentation/sound/alsa/alsa-parameters.txt
+
+ alignment= [KNL,ARM]
+ Allow the default userspace alignment fault handler
+ behaviour to be specified. Bit 0 enables warnings,
+ bit 1 enables fixups, and bit 2 sends a segfault.
+
+ align_va_addr= [X86-64]
+ Align virtual addresses by clearing slice [14:12] when
+ allocating a VMA at process creation time. This option
+ gives you up to 3% performance improvement on AMD F15h
+ machines (where it is enabled by default) for a
+ CPU-intensive style benchmark, and it can vary highly in
+ a microbenchmark depending on workload and compiler.
+
+ 32: only for 32-bit processes
+ 64: only for 64-bit processes
+ on: enable for both 32- and 64-bit processes
+ off: disable for both 32- and 64-bit processes
+
+ alloc_snapshot [FTRACE]
+ Allocate the ftrace snapshot buffer on boot up when the
+ main buffer is allocated. This is handy if debugging
+ and you need to use tracing_snapshot() on boot up, and
+ do not want to use tracing_snapshot_alloc() as it needs
+ to be done where GFP_KERNEL allocations are allowed.
+
+ amd_iommu= [HW,X86-64]
+ Pass parameters to the AMD IOMMU driver in the system.
+ Possible values are:
+ fullflush - enable flushing of IO/TLB entries when
+ they are unmapped. Otherwise they are
+ flushed before they will be reused, which
+ is a lot of faster
+ off - do not initialize any AMD IOMMU found in
+ the system
+ force_isolation - Force device isolation for all
+ devices. The IOMMU driver is not
+ allowed anymore to lift isolation
+ requirements as needed. This option
+ does not override iommu=pt
+
+ amd_iommu_dump= [HW,X86-64]
+ Enable AMD IOMMU driver option to dump the ACPI table
+ for AMD IOMMU. With this option enabled, AMD IOMMU
+ driver will print ACPI tables for AMD IOMMU during
+ IOMMU initialization.
+
+ amd_iommu_intr= [HW,X86-64]
+ Specifies one of the following AMD IOMMU interrupt
+ remapping modes:
+ legacy - Use legacy interrupt remapping mode.
+ vapic - Use virtual APIC mode, which allows IOMMU
+ to inject interrupts directly into guest.
+ This mode requires kvm-amd.avic=1.
+ (Default when IOMMU HW support is present.)
+
+ amijoy.map= [HW,JOY] Amiga joystick support
+ Map of devices attached to JOY0DAT and JOY1DAT
+ Format: <a>,<b>
+ See also Documentation/input/joystick.txt
+
+ analog.map= [HW,JOY] Analog joystick and gamepad support
+ Specifies type or capabilities of an analog joystick
+ connected to one of 16 gameports
+ Format: <type1>,<type2>,..<type16>
+
+ apc= [HW,SPARC]
+ Power management functions (SPARCstation-4/5 + deriv.)
+ Format: noidle
+ Disable APC CPU standby support. SPARCstation-Fox does
+ not play well with APC CPU idle - disable it if you have
+ APC and your system crashes randomly.
+
+ apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
+ Change the output verbosity whilst booting
+ Format: { quiet (default) | verbose | debug }
+ Change the amount of debugging information output
+ when initialising the APIC and IO-APIC components.
+
+ apic_extnmi= [APIC,X86] External NMI delivery setting
+ Format: { bsp (default) | all | none }
+ bsp: External NMI is delivered only to CPU 0
+ all: External NMIs are broadcast to all CPUs as a
+ backup of CPU 0
+ none: External NMI is masked for all CPUs. This is
+ useful so that a dump capture kernel won't be
+ shot down by NMI
+
+ autoconf= [IPV6]
+ See Documentation/networking/ipv6.txt.
+
+ show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
+ Limit apic dumping. The parameter defines the maximal
+ number of local apics being dumped. Also it is possible
+ to set it to "all" by meaning -- no limit here.
+ Format: { 1 (default) | 2 | ... | all }.
+ The parameter valid if only apic=debug or
+ apic=verbose is specified.
+ Example: apic=debug show_lapic=all
+
+ apm= [APM] Advanced Power Management
+ See header of arch/x86/kernel/apm_32.c.
+
+ arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
+ Format: <io>,<irq>,<nodeID>
+
+ ataflop= [HW,M68k]
+
+ atarimouse= [HW,MOUSE] Atari Mouse
+
+ atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
+ EzKey and similar keyboards
+
+ atkbd.reset= [HW] Reset keyboard during initialization
+
+ atkbd.set= [HW] Select keyboard code set
+ Format: <int> (2 = AT (default), 3 = PS/2)
+
+ atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
+ keyboards
+
+ atkbd.softraw= [HW] Choose between synthetic and real raw mode
+ Format: <bool> (0 = real, 1 = synthetic (default))
+
+ atkbd.softrepeat= [HW]
+ Use software keyboard repeat
+
+ audit= [KNL] Enable the audit sub-system
+ Format: { "0" | "1" } (0 = disabled, 1 = enabled)
+ 0 - kernel audit is disabled and can not be enabled
+ until the next reboot
+ unset - kernel audit is initialized but disabled and
+ will be fully enabled by the userspace auditd.
+ 1 - kernel audit is initialized and partially enabled,
+ storing at most audit_backlog_limit messages in
+ RAM until it is fully enabled by the userspace
+ auditd.
+ Default: unset
+
+ audit_backlog_limit= [KNL] Set the audit queue size limit.
+ Format: <int> (must be >=0)
+ Default: 64
+
+ bau= [X86_UV] Enable the BAU on SGI UV. The default
+ behavior is to disable the BAU (i.e. bau=0).
+ Format: { "0" | "1" }
+ 0 - Disable the BAU.
+ 1 - Enable the BAU.
+ unset - Disable the BAU.
+
+ baycom_epp= [HW,AX25]
+ Format: <io>,<mode>
+
+ baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
+ Format: <io>,<mode>
+ See header of drivers/net/hamradio/baycom_par.c.
+
+ baycom_ser_fdx= [HW,AX25]
+ BayCom Serial Port AX.25 Modem (Full Duplex Mode)
+ Format: <io>,<irq>,<mode>[,<baud>]
+ See header of drivers/net/hamradio/baycom_ser_fdx.c.
+
+ baycom_ser_hdx= [HW,AX25]
+ BayCom Serial Port AX.25 Modem (Half Duplex Mode)
+ Format: <io>,<irq>,<mode>
+ See header of drivers/net/hamradio/baycom_ser_hdx.c.
+
+ blkdevparts= Manual partition parsing of block device(s) for
+ embedded devices based on command line input.
+ See Documentation/block/cmdline-partition.txt
+
+ boot_delay= Milliseconds to delay each printk during boot.
+ Values larger than 10 seconds (10000) are changed to
+ no delay (0).
+ Format: integer
+
+ bootmem_debug [KNL] Enable bootmem allocator debug messages.
+
+ bert_disable [ACPI]
+ Disable BERT OS support on buggy BIOSes.
+
+ bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
+ bttv.radio= Most important insmod options are available as
+ kernel args too.
+ bttv.pll= See Documentation/video4linux/bttv/Insmod-options
+ bttv.tuner=
+
+ bulk_remove=off [PPC] This parameter disables the use of the pSeries
+ firmware feature for flushing multiple hpte entries
+ at a time.
+
+ c101= [NET] Moxa C101 synchronous serial card
+
+ cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
+ Sometimes CPU hardware bugs make them report the cache
+ size incorrectly. The kernel will attempt work arounds
+ to fix known problems, but for some CPUs it is not
+ possible to determine what the correct size should be.
+ This option provides an override for these situations.
+
+ ca_keys= [KEYS] This parameter identifies a specific key(s) on
+ the system trusted keyring to be used for certificate
+ trust validation.
+ format: { id:<keyid> | builtin }
+
+ cca= [MIPS] Override the kernel pages' cache coherency
+ algorithm. Accepted values range from 0 to 7
+ inclusive. See arch/mips/include/asm/pgtable-bits.h
+ for platform specific values (SB1, Loongson3 and
+ others).
+
+ ccw_timeout_log [S390]
+ See Documentation/s390/CommonIO for details.
+
+ cgroup_disable= [KNL] Disable a particular controller
+ Format: {name of the controller(s) to disable}
+ The effects of cgroup_disable=foo are:
+ - foo isn't auto-mounted if you mount all cgroups in
+ a single hierarchy
+ - foo isn't visible as an individually mountable
+ subsystem
+ {Currently only "memory" controller deal with this and
+ cut the overhead, others just disable the usage. So
+ only cgroup_disable=memory is actually worthy}
+
+ cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1
+ Format: { controller[,controller...] | "all" }
+ Like cgroup_disable, but only applies to cgroup v1;
+ the blacklisted controllers remain available in cgroup2.
+
+ cgroup.memory= [KNL] Pass options to the cgroup memory controller.
+ Format: <string>
+ nosocket -- Disable socket memory accounting.
+ nokmem -- Disable kernel memory accounting.
+
+ checkreqprot [SELINUX] Set initial checkreqprot flag value.
+ Format: { "0" | "1" }
+ See security/selinux/Kconfig help text.
+ 0 -- check protection applied by kernel (includes
+ any implied execute protection).
+ 1 -- check protection requested by application.
+ Default value is set via a kernel config option.
+ Value can be changed at runtime via
+ /selinux/checkreqprot.
+
+ cio_ignore= [S390]
+ See Documentation/s390/CommonIO for details.
+ clk_ignore_unused
+ [CLK]
+ Prevents the clock framework from automatically gating
+ clocks that have not been explicitly enabled by a Linux
+ device driver but are enabled in hardware at reset or
+ by the bootloader/firmware. Note that this does not
+ force such clocks to be always-on nor does it reserve
+ those clocks in any way. This parameter is useful for
+ debug and development, but should not be needed on a
+ platform with proper driver support. For more
+ information, see Documentation/clk.txt.
+
+ clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
+ [Deprecated]
+ Forces specified clocksource (if available) to be used
+ when calculating gettimeofday(). If specified
+ clocksource is not available, it defaults to PIT.
+ Format: { pit | tsc | cyclone | pmtmr }
+
+ clocksource= Override the default clocksource
+ Format: <string>
+ Override the default clocksource and use the clocksource
+ with the name specified.
+ Some clocksource names to choose from, depending on
+ the platform:
+ [all] jiffies (this is the base, fallback clocksource)
+ [ACPI] acpi_pm
+ [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
+ pxa_timer,timer3,32k_counter,timer0_1
+ [AVR32] avr32
+ [X86-32] pit,hpet,tsc;
+ scx200_hrt on Geode; cyclone on IBM x440
+ [MIPS] MIPS
+ [PARISC] cr16
+ [S390] tod
+ [SH] SuperH
+ [SPARC64] tick
+ [X86-64] hpet,tsc
+
+ clocksource.arm_arch_timer.evtstrm=
+ [ARM,ARM64]
+ Format: <bool>
+ Enable/disable the eventstream feature of the ARM
+ architected timer so that code using WFE-based polling
+ loops can be debugged more effectively on production
+ systems.
+
+ clocksource.arm_arch_timer.fsl-a008585=
+ [ARM64]
+ Format: <bool>
+ Enable/disable the workaround of Freescale/NXP
+ erratum A-008585. This can be useful for KVM
+ guests, if the guest device tree doesn't show the
+ erratum. If unspecified, the workaround is
+ enabled based on the device tree.
+
+ clearcpuid=BITNUM [X86]
+ Disable CPUID feature X for the kernel. See
+ arch/x86/include/asm/cpufeatures.h for the valid bit
+ numbers. Note the Linux specific bits are not necessarily
+ stable over kernel options, but the vendor specific
+ ones should be.
+ Also note that user programs calling CPUID directly
+ or using the feature without checking anything
+ will still see it. This just prevents it from
+ being used by the kernel or shown in /proc/cpuinfo.
+ Also note the kernel might malfunction if you disable
+ some critical bits.
+
+ cma=nn[MG]@[start[MG][-end[MG]]]
+ [ARM,X86,KNL]
+ Sets the size of kernel global memory area for
+ contiguous memory allocations and optionally the
+ placement constraint by the physical address range of
+ memory allocations. A value of 0 disables CMA
+ altogether. For more information, see
+ include/linux/dma-contiguous.h
+
+ cmo_free_hint= [PPC] Format: { yes | no }
+ Specify whether pages are marked as being inactive
+ when they are freed. This is used in CMO environments
+ to determine OS memory pressure for page stealing by
+ a hypervisor.
+ Default: yes
+
+ coherent_pool=nn[KMG] [ARM,KNL]
+ Sets the size of memory pool for coherent, atomic dma
+ allocations, by default set to 256K.
+
+ code_bytes [X86] How many bytes of object code to print
+ in an oops report.
+ Range: 0 - 8192
+ Default: 64
+
+ com20020= [HW,NET] ARCnet - COM20020 chipset
+ Format:
+ <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
+
+ com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
+ Format: <io>[,<irq>]
+
+ com90xx= [HW,NET]
+ ARCnet - COM90xx chipset (memory-mapped buffers)
+ Format: <io>[,<irq>[,<memstart>]]
+
+ condev= [HW,S390] console device
+ conmode=
+
+ console= [KNL] Output console device and options.
+
+ tty<n> Use the virtual console device <n>.
+
+ ttyS<n>[,options]
+ ttyUSB0[,options]
+ Use the specified serial port. The options are of
+ the form "bbbbpnf", where "bbbb" is the baud rate,
+ "p" is parity ("n", "o", or "e"), "n" is number of
+ bits, and "f" is flow control ("r" for RTS or
+ omit it). Default is "9600n8".
+
+ See Documentation/admin-guide/serial-console.rst for more
+ information. See
+ Documentation/networking/netconsole.txt for an
+ alternative.
+
+ uart[8250],io,<addr>[,options]
+ uart[8250],mmio,<addr>[,options]
+ uart[8250],mmio16,<addr>[,options]
+ uart[8250],mmio32,<addr>[,options]
+ uart[8250],0x<addr>[,options]
+ Start an early, polled-mode console on the 8250/16550
+ UART at the specified I/O port or MMIO address,
+ switching to the matching ttyS device later.
+ MMIO inter-register address stride is either 8-bit
+ (mmio), 16-bit (mmio16), or 32-bit (mmio32).
+ If none of [io|mmio|mmio16|mmio32], <addr> is assumed
+ to be equivalent to 'mmio'. 'options' are specified in
+ the same format described for ttyS above; if unspecified,
+ the h/w is not re-initialized.
+
+ hvc<n> Use the hypervisor console device <n>. This is for
+ both Xen and PowerPC hypervisors.
+
+ If the device connected to the port is not a TTY but a braille
+ device, prepend "brl," before the device type, for instance
+ console=brl,ttyS0
+ For now, only VisioBraille is supported.
+
+ consoleblank= [KNL] The console blank (screen saver) timeout in
+ seconds. Defaults to 10*60 = 10mins. A value of 0
+ disables the blank timer.
+
+ coredump_filter=
+ [KNL] Change the default value for
+ /proc/<pid>/coredump_filter.
+ See also Documentation/filesystems/proc.txt.
+
+ cpuidle.off=1 [CPU_IDLE]
+ disable the cpuidle sub-system
+
+ cpu_init_udelay=N
+ [X86] Delay for N microsec between assert and de-assert
+ of APIC INIT to start processors. This delay occurs
+ on every CPU online, such as boot, and resume from suspend.
+ Default: 10000
+
+ cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
+ Format:
+ <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
+
+ crashkernel=size[KMG][@offset[KMG]]
+ [KNL] Using kexec, Linux can switch to a 'crash kernel'
+ upon panic. This parameter reserves the physical
+ memory region [offset, offset + size] for that kernel
+ image. If '@offset' is omitted, then a suitable offset
+ is selected automatically. Check
+ Documentation/kdump/kdump.txt for further details.
+
+ crashkernel=range1:size1[,range2:size2,...][@offset]
+ [KNL] Same as above, but depends on the memory
+ in the running system. The syntax of range is
+ start-[end] where start and end are both
+ a memory unit (amount[KMG]). See also
+ Documentation/kdump/kdump.txt for an example.
+
+ crashkernel=size[KMG],high
+ [KNL, x86_64] range could be above 4G. Allow kernel
+ to allocate physical memory region from top, so could
+ be above 4G if system have more than 4G ram installed.
+ Otherwise memory region will be allocated below 4G, if
+ available.
+ It will be ignored if crashkernel=X is specified.
+ crashkernel=size[KMG],low
+ [KNL, x86_64] range under 4G. When crashkernel=X,high
+ is passed, kernel could allocate physical memory region
+ above 4G, that cause second kernel crash on system
+ that require some amount of low memory, e.g. swiotlb
+ requires at least 64M+32K low memory, also enough extra
+ low memory is needed to make sure DMA buffers for 32-bit
+ devices won't run out. Kernel would try to allocate at
+ at least 256M below 4G automatically.
+ This one let user to specify own low range under 4G
+ for second kernel instead.
+ 0: to disable low allocation.
+ It will be ignored when crashkernel=X,high is not used
+ or memory reserved is below 4G.
+
+ cryptomgr.notests
+ [KNL] Disable crypto self-tests
+
+ cs89x0_dma= [HW,NET]
+ Format: <dma>
+
+ cs89x0_media= [HW,NET]
+ Format: { rj45 | aui | bnc }
+
+ dasd= [HW,NET]
+ See header of drivers/s390/block/dasd_devmap.c.
+
+ db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
+ (one device per port)
+ Format: <port#>,<type>
+ See also Documentation/input/joystick-parport.txt
+
+ ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
+ time. See Documentation/dynamic-debug-howto.txt for
+ details. Deprecated, see dyndbg.
+
+ debug [KNL] Enable kernel debugging (events log level).
+
+ debug_locks_verbose=
+ [KNL] verbose self-tests
+ Format=<0|1>
+ Print debugging info while doing the locking API
+ self-tests.
+ We default to 0 (no extra messages), setting it to
+ 1 will print _a lot_ more information - normally
+ only useful to kernel developers.
+
+ debug_objects [KNL] Enable object debugging
+
+ no_debug_objects
+ [KNL] Disable object debugging
+
+ debug_guardpage_minorder=
+ [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
+ parameter allows control of the order of pages that will
+ be intentionally kept free (and hence protected) by the
+ buddy allocator. Bigger value increase the probability
+ of catching random memory corruption, but reduce the
+ amount of memory for normal system use. The maximum
+ possible value is MAX_ORDER/2. Setting this parameter
+ to 1 or 2 should be enough to identify most random
+ memory corruption problems caused by bugs in kernel or
+ driver code when a CPU writes to (or reads from) a
+ random memory location. Note that there exists a class
+ of memory corruptions problems caused by buggy H/W or
+ F/W or by drivers badly programing DMA (basically when
+ memory is written at bus level and the CPU MMU is
+ bypassed) which are not detectable by
+ CONFIG_DEBUG_PAGEALLOC, hence this option will not help
+ tracking down these problems.
+
+ debug_pagealloc=
+ [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
+ parameter enables the feature at boot time. In
+ default, it is disabled. We can avoid allocating huge
+ chunk of memory for debug pagealloc if we don't enable
+ it at boot time and the system will work mostly same
+ with the kernel built without CONFIG_DEBUG_PAGEALLOC.
+ on: enable the feature
+
+ debugpat [X86] Enable PAT debugging
+
+ decnet.addr= [HW,NET]
+ Format: <area>[,<node>]
+ See also Documentation/networking/decnet.txt.
+
+ default_hugepagesz=
+ [same as hugepagesz=] The size of the default
+ HugeTLB page size. This is the size represented by
+ the legacy /proc/ hugepages APIs, used for SHM, and
+ default size when mounting hugetlbfs filesystems.
+ Defaults to the default architecture's huge page size
+ if not specified.
+
+ dhash_entries= [KNL]
+ Set number of hash buckets for dentry cache.
+
+ disable_1tb_segments [PPC]
+ Disables the use of 1TB hash page table segments. This
+ causes the kernel to fall back to 256MB segments which
+ can be useful when debugging issues that require an SLB
+ miss to occur.
+
+ disable= [IPV6]
+ See Documentation/networking/ipv6.txt.
+
+ disable_radix [PPC]
+ Disable RADIX MMU mode on POWER9
+
+ disable_cpu_apicid= [X86,APIC,SMP]
+ Format: <int>
+ The number of initial APIC ID for the
+ corresponding CPU to be disabled at boot,
+ mostly used for the kdump 2nd kernel to
+ disable BSP to wake up multiple CPUs without
+ causing system reset or hang due to sending
+ INIT from AP to BSP.
+
+ disable_ddw [PPC/PSERIES]
+ Disable Dynamic DMA Window support. Use this if
+ to workaround buggy firmware.
+
+ disable_ipv6= [IPV6]
+ See Documentation/networking/ipv6.txt.
+
+ disable_mtrr_cleanup [X86]
+ The kernel tries to adjust MTRR layout from continuous
+ to discrete, to make X server driver able to add WB
+ entry later. This parameter disables that.
+
+ disable_mtrr_trim [X86, Intel and AMD only]
+ By default the kernel will trim any uncacheable
+ memory out of your available memory pool based on
+ MTRR settings. This parameter disables that behavior,
+ possibly causing your machine to run very slowly.
+
+ disable_timer_pin_1 [X86]
+ Disable PIN 1 of APIC timer
+ Can be useful to work around chipset bugs.
+
+ dis_ucode_ldr [X86] Disable the microcode loader.
+
+ dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
+ this option disables the debugging code at boot.
+
+ dma_debug_entries=<number>
+ This option allows to tune the number of preallocated
+ entries for DMA-API debugging code. One entry is
+ required per DMA-API allocation. Use this if the
+ DMA-API debugging code disables itself because the
+ architectural default is too low.
+
+ dma_debug_driver=<driver_name>
+ With this option the DMA-API debugging driver
+ filter feature can be enabled at boot time. Just
+ pass the driver to filter for as the parameter.
+ The filter can be disabled or changed to another
+ driver later using sysfs.
+
+ drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
+ Broken monitors, graphic adapters, KVMs and EDIDless
+ panels may send no or incorrect EDID data sets.
+ This parameter allows to specify an EDID data sets
+ in the /lib/firmware directory that are used instead.
+ Generic built-in EDID data sets are used, if one of
+ edid/1024x768.bin, edid/1280x1024.bin,
+ edid/1680x1050.bin, or edid/1920x1080.bin is given
+ and no file with the same name exists. Details and
+ instructions how to build your own EDID data are
+ available in Documentation/EDID/HOWTO.txt. An EDID
+ data set will only be used for a particular connector,
+ if its name and a colon are prepended to the EDID
+ name. Each connector may use a unique EDID data
+ set by separating the files with a comma. An EDID
+ data set with no connector name will be used for
+ any connectors not explicitly specified.
+
+ dscc4.setup= [NET]
+
+ dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
+ module.dyndbg[="val"]
+ Enable debug messages at boot time. See
+ Documentation/dynamic-debug-howto.txt for details.
+
+ nompx [X86] Disables Intel Memory Protection Extensions.
+ See Documentation/x86/intel_mpx.txt for more
+ information about the feature.
+
+ nopku [X86] Disable Memory Protection Keys CPU feature found
+ in some Intel CPUs.
+
+ eagerfpu= [X86]
+ on enable eager fpu restore
+ off disable eager fpu restore
+ auto selects the default scheme, which automatically
+ enables eagerfpu restore for xsaveopt.
+
+ module.async_probe [KNL]
+ Enable asynchronous probe on this module.
+
+ early_ioremap_debug [KNL]
+ Enable debug messages in early_ioremap support. This
+ is useful for tracking down temporary early mappings
+ which are not unmapped.
+
+ earlycon= [KNL] Output early console device and options.
+
+ When used with no options, the early console is
+ determined by the stdout-path property in device
+ tree's chosen node.
+
+ cdns,<addr>[,options]
+ Start an early, polled-mode console on a Cadence
+ (xuartps) serial port at the specified address. Only
+ supported option is baud rate. If baud rate is not
+ specified, the serial port must already be setup and
+ configured.
+
+ uart[8250],io,<addr>[,options]
+ uart[8250],mmio,<addr>[,options]
+ uart[8250],mmio32,<addr>[,options]
+ uart[8250],mmio32be,<addr>[,options]
+ uart[8250],0x<addr>[,options]
+ Start an early, polled-mode console on the 8250/16550
+ UART at the specified I/O port or MMIO address.
+ MMIO inter-register address stride is either 8-bit
+ (mmio) or 32-bit (mmio32 or mmio32be).
+ If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
+ to be equivalent to 'mmio'. 'options' are specified
+ in the same format described for "console=ttyS<n>"; if
+ unspecified, the h/w is not initialized.
+
+ pl011,<addr>
+ pl011,mmio32,<addr>
+ Start an early, polled-mode console on a pl011 serial
+ port at the specified address. The pl011 serial port
+ must already be setup and configured. Options are not
+ yet supported. If 'mmio32' is specified, then only
+ the driver will use only 32-bit accessors to read/write
+ the device registers.
+
+ meson,<addr>
+ Start an early, polled-mode console on a meson serial
+ port at the specified address. The serial port must
+ already be setup and configured. Options are not yet
+ supported.
+
+ msm_serial,<addr>
+ Start an early, polled-mode console on an msm serial
+ port at the specified address. The serial port
+ must already be setup and configured. Options are not
+ yet supported.
+
+ msm_serial_dm,<addr>
+ Start an early, polled-mode console on an msm serial
+ dm port at the specified address. The serial port
+ must already be setup and configured. Options are not
+ yet supported.
+
+ smh Use ARM semihosting calls for early console.
+
+ s3c2410,<addr>
+ s3c2412,<addr>
+ s3c2440,<addr>
+ s3c6400,<addr>
+ s5pv210,<addr>
+ exynos4210,<addr>
+ Use early console provided by serial driver available
+ on Samsung SoCs, requires selecting proper type and
+ a correct base address of the selected UART port. The
+ serial port must already be setup and configured.
+ Options are not yet supported.
+
+ lpuart,<addr>
+ lpuart32,<addr>
+ Use early console provided by Freescale LP UART driver
+ found on Freescale Vybrid and QorIQ LS1021A processors.
+ A valid base address must be provided, and the serial
+ port must already be setup and configured.
+
+ armada3700_uart,<addr>
+ Start an early, polled-mode console on the
+ Armada 3700 serial port at the specified
+ address. The serial port must already be setup
+ and configured. Options are not yet supported.
+
+ earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
+ earlyprintk=vga
+ earlyprintk=efi
+ earlyprintk=xen
+ earlyprintk=serial[,ttySn[,baudrate]]
+ earlyprintk=serial[,0x...[,baudrate]]
+ earlyprintk=ttySn[,baudrate]
+ earlyprintk=dbgp[debugController#]
+ earlyprintk=pciserial,bus:device.function[,baudrate]
+
+ earlyprintk is useful when the kernel crashes before
+ the normal console is initialized. It is not enabled by
+ default because it has some cosmetic problems.
+
+ Append ",keep" to not disable it when the real console
+ takes over.
+
+ Only one of vga, efi, serial, or usb debug port can
+ be used at a time.
+
+ Currently only ttyS0 and ttyS1 may be specified by
+ name. Other I/O ports may be explicitly specified
+ on some architectures (x86 and arm at least) by
+ replacing ttySn with an I/O port address, like this:
+ earlyprintk=serial,0x1008,115200
+ You can find the port for a given device in
+ /proc/tty/driver/serial:
+ 2: uart:ST16650V2 port:00001008 irq:18 ...
+
+ Interaction with the standard serial driver is not
+ very good.
+
+ The VGA and EFI output is eventually overwritten by
+ the real console.
+
+ The xen output can only be used by Xen PV guests.
+
+ edac_report= [HW,EDAC] Control how to report EDAC event
+ Format: {"on" | "off" | "force"}
+ on: enable EDAC to report H/W event. May be overridden
+ by other higher priority error reporting module.
+ off: disable H/W event reporting through EDAC.
+ force: enforce the use of EDAC to report H/W event.
+ default: on.
+
+ ekgdboc= [X86,KGDB] Allow early kernel console debugging
+ ekgdboc=kbd
+
+ This is designed to be used in conjunction with
+ the boot argument: earlyprintk=vga
+
+ edd= [EDD]
+ Format: {"off" | "on" | "skip[mbr]"}
+
+ efi= [EFI]
+ Format: { "old_map", "nochunk", "noruntime", "debug" }
+ old_map [X86-64]: switch to the old ioremap-based EFI
+ runtime services mapping. 32-bit still uses this one by
+ default.
+ nochunk: disable reading files in "chunks" in the EFI
+ boot stub, as chunking can cause problems with some
+ firmware implementations.
+ noruntime : disable EFI runtime services support
+ debug: enable misc debug output
+
+ efi_no_storage_paranoia [EFI; X86]
+ Using this parameter you can use more than 50% of
+ your efi variable storage. Use this parameter only if
+ you are really sure that your UEFI does sane gc and
+ fulfills the spec otherwise your board may brick.
+
+ efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
+ Add arbitrary attribute to specific memory range by
+ updating original EFI memory map.
+ Region of memory which aa attribute is added to is
+ from ss to ss+nn.
+ If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
+ is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
+ attribute is added to range 0x100000000-0x180000000 and
+ 0x10a0000000-0x1120000000.
+
+ Using this parameter you can do debugging of EFI memmap
+ related feature. For example, you can do debugging of
+ Address Range Mirroring feature even if your box
+ doesn't support it.
+
+ efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
+ that is to be dynamically loaded by Linux. If there are
+ multiple variables with the same name but with different
+ vendor GUIDs, all of them will be loaded. See
+ Documentation/acpi/ssdt-overlays.txt for details.
+
+
+ eisa_irq_edge= [PARISC,HW]
+ See header of drivers/parisc/eisa.c.
+
+ elanfreq= [X86-32]
+ See comment before function elanfreq_setup() in
+ arch/x86/kernel/cpu/cpufreq/elanfreq.c.
+
+ elevator= [IOSCHED]
+ Format: {"cfq" | "deadline" | "noop"}
+ See Documentation/block/cfq-iosched.txt and
+ Documentation/block/deadline-iosched.txt for details.
+
+ elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
+ Specifies physical address of start of kernel core
+ image elf header and optionally the size. Generally
+ kexec loader will pass this option to capture kernel.
+ See Documentation/kdump/kdump.txt for details.
+
+ enable_mtrr_cleanup [X86]
+ The kernel tries to adjust MTRR layout from continuous
+ to discrete, to make X server driver able to add WB
+ entry later. This parameter enables that.
+
+ enable_timer_pin_1 [X86]
+ Enable PIN 1 of APIC timer
+ Can be useful to work around chipset bugs
+ (in particular on some ATI chipsets).
+ The kernel tries to set a reasonable default.
+
+ enforcing [SELINUX] Set initial enforcing status.
+ Format: {"0" | "1"}
+ See security/selinux/Kconfig help text.
+ 0 -- permissive (log only, no denials).
+ 1 -- enforcing (deny and log).
+ Default value is 0.
+ Value can be changed at runtime via /selinux/enforce.
+
+ erst_disable [ACPI]
+ Disable Error Record Serialization Table (ERST)
+ support.
+
+ ether= [HW,NET] Ethernet cards parameters
+ This option is obsoleted by the "netdev=" option, which
+ has equivalent usage. See its documentation for details.
+
+ evm= [EVM]
+ Format: { "fix" }
+ Permit 'security.evm' to be updated regardless of
+ current integrity status.
+
+ failslab=
+ fail_page_alloc=
+ fail_make_request=[KNL]
+ General fault injection mechanism.
+ Format: <interval>,<probability>,<space>,<times>
+ See also Documentation/fault-injection/.
+
+ floppy= [HW]
+ See Documentation/blockdev/floppy.txt.
+
+ force_pal_cache_flush
+ [IA-64] Avoid check_sal_cache_flush which may hang on
+ buggy SAL_CACHE_FLUSH implementations. Using this
+ parameter will force ia64_sal_cache_flush to call
+ ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
+
+ forcepae [X86-32]
+ Forcefully enable Physical Address Extension (PAE).
+ Many Pentium M systems disable PAE but may have a
+ functionally usable PAE implementation.
+ Warning: use of this parameter will taint the kernel
+ and may cause unknown problems.
+
+ ftrace=[tracer]
+ [FTRACE] will set and start the specified tracer
+ as early as possible in order to facilitate early
+ boot debugging.
+
+ ftrace_dump_on_oops[=orig_cpu]
+ [FTRACE] will dump the trace buffers on oops.
+ If no parameter is passed, ftrace will dump
+ buffers of all CPUs, but if you pass orig_cpu, it will
+ dump only the buffer of the CPU that triggered the
+ oops.
+
+ ftrace_filter=[function-list]
+ [FTRACE] Limit the functions traced by the function
+ tracer at boot up. function-list is a comma separated
+ list of functions. This list can be changed at run
+ time by the set_ftrace_filter file in the debugfs
+ tracing directory.
+
+ ftrace_notrace=[function-list]
+ [FTRACE] Do not trace the functions specified in
+ function-list. This list can be changed at run time
+ by the set_ftrace_notrace file in the debugfs
+ tracing directory.
+
+ ftrace_graph_filter=[function-list]
+ [FTRACE] Limit the top level callers functions traced
+ by the function graph tracer at boot up.
+ function-list is a comma separated list of functions
+ that can be changed at run time by the
+ set_graph_function file in the debugfs tracing directory.
+
+ ftrace_graph_notrace=[function-list]
+ [FTRACE] Do not trace from the functions specified in
+ function-list. This list is a comma separated list of
+ functions that can be changed at run time by the
+ set_graph_notrace file in the debugfs tracing directory.
+
+ gamecon.map[2|3]=
+ [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
+ support via parallel port (up to 5 devices per port)
+ Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
+ See also Documentation/input/joystick-parport.txt
+
+ gamma= [HW,DRM]
+
+ gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
+ Format: off | on
+ default: on
+
+ gcov_persist= [GCOV] When non-zero (default), profiling data for
+ kernel modules is saved and remains accessible via
+ debugfs, even when the module is unloaded/reloaded.
+ When zero, profiling data is discarded and associated
+ debugfs files are removed at module unload time.
+
+ gpt [EFI] Forces disk with valid GPT signature but
+ invalid Protective MBR to be treated as GPT. If the
+ primary GPT is corrupted, it enables the backup/alternate
+ GPT to be used instead.
+
+ grcan.enable0= [HW] Configuration of physical interface 0. Determines
+ the "Enable 0" bit of the configuration register.
+ Format: 0 | 1
+ Default: 0
+ grcan.enable1= [HW] Configuration of physical interface 1. Determines
+ the "Enable 0" bit of the configuration register.
+ Format: 0 | 1
+ Default: 0
+ grcan.select= [HW] Select which physical interface to use.
+ Format: 0 | 1
+ Default: 0
+ grcan.txsize= [HW] Sets the size of the tx buffer.
+ Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
+ Default: 1024
+ grcan.rxsize= [HW] Sets the size of the rx buffer.
+ Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
+ Default: 1024
+
+ gpio-mockup.gpio_mockup_ranges
+ [HW] Sets the ranges of gpiochip of for this device.
+ Format: <start1>,<end1>,<start2>,<end2>...
+
+ hardlockup_all_cpu_backtrace=
+ [KNL] Should the hard-lockup detector generate
+ backtraces on all cpus.
+ Format: <integer>
+
+ hashdist= [KNL,NUMA] Large hashes allocated during boot
+ are distributed across NUMA nodes. Defaults on
+ for 64-bit NUMA, off otherwise.
+ Format: 0 | 1 (for off | on)
+
+ hcl= [IA-64] SGI's Hardware Graph compatibility layer
+
+ hd= [EIDE] (E)IDE hard drive subsystem geometry
+ Format: <cyl>,<head>,<sect>
+
+ hest_disable [ACPI]
+ Disable Hardware Error Source Table (HEST) support;
+ corresponding firmware-first mode error processing
+ logic will be disabled.
+
+ highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
+ size of <nn>. This works even on boxes that have no
+ highmem otherwise. This also works to reduce highmem
+ size on bigger boxes.
+
+ highres= [KNL] Enable/disable high resolution timer mode.
+ Valid parameters: "on", "off"
+ Default: "on"
+
+ hisax= [HW,ISDN]
+ See Documentation/isdn/README.HiSax.
+
+ hlt [BUGS=ARM,SH]
+
+ hpet= [X86-32,HPET] option to control HPET usage
+ Format: { enable (default) | disable | force |
+ verbose }
+ disable: disable HPET and use PIT instead
+ force: allow force enabled of undocumented chips (ICH4,
+ VIA, nVidia)
+ verbose: show contents of HPET registers during setup
+
+ hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
+ registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
+
+ hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
+ hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
+ On x86-64 and powerpc, this option can be specified
+ multiple times interleaved with hugepages= to reserve
+ huge pages of different sizes. Valid pages sizes on
+ x86-64 are 2M (when the CPU supports "pse") and 1G
+ (when the CPU supports the "pdpe1gb" cpuinfo flag).
+
+ hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
+ terminal devices. Valid values: 0..8
+ hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
+ If specified, z/VM IUCV HVC accepts connections
+ from listed z/VM user IDs only.
+
+ hwthread_map= [METAG] Comma-separated list of Linux cpu id to
+ hardware thread id mappings.
+ Format: <cpu>:<hwthread>
+
+ keep_bootcon [KNL]
+ Do not unregister boot console at start. This is only
+ useful for debugging when something happens in the window
+ between unregistering the boot console and initializing
+ the real console.
+
+ i2c_bus= [HW] Override the default board specific I2C bus speed
+ or register an additional I2C bus that is not
+ registered from board initialization code.
+ Format:
+ <bus_id>,<clkrate>
+
+ i8042.debug [HW] Toggle i8042 debug mode
+ i8042.unmask_kbd_data
+ [HW] Enable printing of interrupt data from the KBD port
+ (disabled by default, and as a pre-condition
+ requires that i8042.debug=1 be enabled)
+ i8042.direct [HW] Put keyboard port into non-translated mode
+ i8042.dumbkbd [HW] Pretend that controller can only read data from
+ keyboard and cannot control its state
+ (Don't attempt to blink the leds)
+ i8042.noaux [HW] Don't check for auxiliary (== mouse) port
+ i8042.nokbd [HW] Don't check/create keyboard port
+ i8042.noloop [HW] Disable the AUX Loopback command while probing
+ for the AUX port
+ i8042.nomux [HW] Don't check presence of an active multiplexing
+ controller
+ i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
+ controllers
+ i8042.notimeout [HW] Ignore timeout condition signalled by controller
+ i8042.reset [HW] Reset the controller during init, cleanup and
+ suspend-to-ram transitions, only during s2r
+ transitions, or never reset
+ Format: { 1 | Y | y | 0 | N | n }
+ 1, Y, y: always reset controller
+ 0, N, n: don't ever reset controller
+ Default: only on s2r transitions on x86; most other
+ architectures force reset to be always executed
+ i8042.unlock [HW] Unlock (ignore) the keylock
+ i8042.kbdreset [HW] Reset device connected to KBD port
+
+ i810= [HW,DRM]
+
+ i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
+ indicates that the driver is running on unsupported
+ hardware.
+ i8k.force [HW] Activate i8k driver even if SMM BIOS signature
+ does not match list of supported models.
+ i8k.power_status
+ [HW] Report power status in /proc/i8k
+ (disabled by default)
+ i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
+ capability is set.
+
+ i915.invert_brightness=
+ [DRM] Invert the sense of the variable that is used to
+ set the brightness of the panel backlight. Normally a
+ brightness value of 0 indicates backlight switched off,
+ and the maximum of the brightness value sets the backlight
+ to maximum brightness. If this parameter is set to 0
+ (default) and the machine requires it, or this parameter
+ is set to 1, a brightness value of 0 sets the backlight
+ to maximum brightness, and the maximum of the brightness
+ value switches the backlight off.
+ -1 -- never invert brightness
+ 0 -- machine default
+ 1 -- force brightness inversion
+
+ icn= [HW,ISDN]
+ Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
+
+ ide-core.nodma= [HW] (E)IDE subsystem
+ Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
+ .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
+ .cdrom .chs .ignore_cable are additional options
+ See Documentation/ide/ide.txt.
+
+ ide-generic.probe-mask= [HW] (E)IDE subsystem
+ Format: <int>
+ Probe mask for legacy ISA IDE ports. Depending on
+ platform up to 6 ports are supported, enabled by
+ setting corresponding bits in the mask to 1. The
+ default value is 0x0, which has a special meaning.
+ On systems that have PCI, it triggers scanning the
+ PCI bus for the first and the second port, which
+ are then probed. On systems without PCI the value
+ of 0x0 enables probing the two first ports as if it
+ was 0x3.
+
+ ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
+ Claim all unknown PCI IDE storage controllers.
+
+ idle= [X86]
+ Format: idle=poll, idle=halt, idle=nomwait
+ Poll forces a polling idle loop that can slightly
+ improve the performance of waking up a idle CPU, but
+ will use a lot of power and make the system run hot.
+ Not recommended.
+ idle=halt: Halt is forced to be used for CPU idle.
+ In such case C2/C3 won't be used again.
+ idle=nomwait: Disable mwait for CPU C-states
+
+ ieee754= [MIPS] Select IEEE Std 754 conformance mode
+ Format: { strict | legacy | 2008 | relaxed }
+ Default: strict
+
+ Choose which programs will be accepted for execution
+ based on the IEEE 754 NaN encoding(s) supported by
+ the FPU and the NaN encoding requested with the value
+ of an ELF file header flag individually set by each
+ binary. Hardware implementations are permitted to
+ support either or both of the legacy and the 2008 NaN
+ encoding mode.
+
+ Available settings are as follows:
+ strict accept binaries that request a NaN encoding
+ supported by the FPU
+ legacy only accept legacy-NaN binaries, if supported
+ by the FPU
+ 2008 only accept 2008-NaN binaries, if supported
+ by the FPU
+ relaxed accept any binaries regardless of whether
+ supported by the FPU
+
+ The FPU emulator is always able to support both NaN
+ encodings, so if no FPU hardware is present or it has
+ been disabled with 'nofpu', then the settings of
+ 'legacy' and '2008' strap the emulator accordingly,
+ 'relaxed' straps the emulator for both legacy-NaN and
+ 2008-NaN, whereas 'strict' enables legacy-NaN only on
+ legacy processors and both NaN encodings on MIPS32 or
+ MIPS64 CPUs.
+
+ The setting for ABS.fmt/NEG.fmt instruction execution
+ mode generally follows that for the NaN encoding,
+ except where unsupported by hardware.
+
+ ignore_loglevel [KNL]
+ Ignore loglevel setting - this will print /all/
+ kernel messages to the console. Useful for debugging.
+ We also add it as printk module parameter, so users
+ could change it dynamically, usually by
+ /sys/module/printk/parameters/ignore_loglevel.
+
+ ignore_rlimit_data
+ Ignore RLIMIT_DATA setting for data mappings,
+ print warning at first misuse. Can be changed via
+ /sys/module/kernel/parameters/ignore_rlimit_data.
+
+ ihash_entries= [KNL]
+ Set number of hash buckets for inode cache.
+
+ ima_appraise= [IMA] appraise integrity measurements
+ Format: { "off" | "enforce" | "fix" | "log" }
+ default: "enforce"
+
+ ima_appraise_tcb [IMA]
+ The builtin appraise policy appraises all files
+ owned by uid=0.
+
+ ima_hash= [IMA]
+ Format: { md5 | sha1 | rmd160 | sha256 | sha384
+ | sha512 | ... }
+ default: "sha1"
+
+ The list of supported hash algorithms is defined
+ in crypto/hash_info.h.
+
+ ima_policy= [IMA]
+ The builtin measurement policy to load during IMA
+ setup. Specyfing "tcb" as the value, measures all
+ programs exec'd, files mmap'd for exec, and all files
+ opened with the read mode bit set by either the
+ effective uid (euid=0) or uid=0.
+ Format: "tcb"
+
+ ima_tcb [IMA] Deprecated. Use ima_policy= instead.
+ Load a policy which meets the needs of the Trusted
+ Computing Base. This means IMA will measure all
+ programs exec'd, files mmap'd for exec, and all files
+ opened for read by uid=0.
+
+ ima_template= [IMA]
+ Select one of defined IMA measurements template formats.
+ Formats: { "ima" | "ima-ng" | "ima-sig" }
+ Default: "ima-ng"
+
+ ima_template_fmt=
+ [IMA] Define a custom template format.
+ Format: { "field1|...|fieldN" }
+
+ ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
+ Format: <min_file_size>
+ Set the minimal file size for using asynchronous hash.
+ If left unspecified, ahash usage is disabled.
+
+ ahash performance varies for different data sizes on
+ different crypto accelerators. This option can be used
+ to achieve the best performance for a particular HW.
+
+ ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
+ Format: <bufsize>
+ Set hashing buffer size. Default: 4k.
+
+ ahash performance varies for different chunk sizes on
+ different crypto accelerators. This option can be used
+ to achieve best performance for particular HW.
+
+ init= [KNL]
+ Format: <full_path>
+ Run specified binary instead of /sbin/init as init
+ process.
+
+ initcall_debug [KNL] Trace initcalls as they are executed. Useful
+ for working out where the kernel is dying during
+ startup.
+
+ initcall_blacklist= [KNL] Do not execute a comma-separated list of
+ initcall functions. Useful for debugging built-in
+ modules and initcalls.
+
+ initrd= [BOOT] Specify the location of the initial ramdisk
+
+ init_pkru= [x86] Specify the default memory protection keys rights
+ register contents for all processes. 0x55555554 by
+ default (disallow access to all but pkey 0). Can
+ override in debugfs after boot.
+
+ inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
+ Format: <irq>
+
+ int_pln_enable [x86] Enable power limit notification interrupt
+
+ integrity_audit=[IMA]
+ Format: { "0" | "1" }
+ 0 -- basic integrity auditing messages. (Default)
+ 1 -- additional integrity auditing messages.
+
+ intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
+ on
+ Enable intel iommu driver.
+ off
+ Disable intel iommu driver.
+ igfx_off [Default Off]
+ By default, gfx is mapped as normal device. If a gfx
+ device has a dedicated DMAR unit, the DMAR unit is
+ bypassed by not enabling DMAR with this option. In
+ this case, gfx device will use physical address for
+ DMA.
+ forcedac [x86_64]
+ With this option iommu will not optimize to look
+ for io virtual address below 32-bit forcing dual
+ address cycle on pci bus for cards supporting greater
+ than 32-bit addressing. The default is to look
+ for translation below 32-bit and if not available
+ then look in the higher range.
+ strict [Default Off]
+ With this option on every unmap_single operation will
+ result in a hardware IOTLB flush operation as opposed
+ to batching them for performance.
+ sp_off [Default Off]
+ By default, super page will be supported if Intel IOMMU
+ has the capability. With this option, super page will
+ not be supported.
+ ecs_off [Default Off]
+ By default, extended context tables will be supported if
+ the hardware advertises that it has support both for the
+ extended tables themselves, and also PASID support. With
+ this option set, extended tables will not be used even
+ on hardware which claims to support them.
+
+ intel_idle.max_cstate= [KNL,HW,ACPI,X86]
+ 0 disables intel_idle and fall back on acpi_idle.
+ 1 to 9 specify maximum depth of C-state.
+
+ intel_pstate= [X86]
+ disable
+ Do not enable intel_pstate as the default
+ scaling driver for the supported processors
+ force
+ Enable intel_pstate on systems that prohibit it by default
+ in favor of acpi-cpufreq. Forcing the intel_pstate driver
+ instead of acpi-cpufreq may disable platform features, such
+ as thermal controls and power capping, that rely on ACPI
+ P-States information being indicated to OSPM and therefore
+ should be used with caution. This option does not work with
+ processors that aren't supported by the intel_pstate driver
+ or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
+ no_hwp
+ Do not enable hardware P state control (HWP)
+ if available.
+ hwp_only
+ Only load intel_pstate on systems which support
+ hardware P state control (HWP) if available.
+ support_acpi_ppc
+ Enforce ACPI _PPC performance limits. If the Fixed ACPI
+ Description Table, specifies preferred power management
+ profile as "Enterprise Server" or "Performance Server",
+ then this feature is turned on by default.
+
+ intremap= [X86-64, Intel-IOMMU]
+ on enable Interrupt Remapping (default)
+ off disable Interrupt Remapping
+ nosid disable Source ID checking
+ no_x2apic_optout
+ BIOS x2APIC opt-out request will be ignored
+ nopost disable Interrupt Posting
+
+ iomem= Disable strict checking of access to MMIO memory
+ strict regions from userspace.
+ relaxed
+
+ iommu= [x86]
+ off
+ force
+ noforce
+ biomerge
+ panic
+ nopanic
+ merge
+ nomerge
+ forcesac
+ soft
+ pt [x86, IA-64]
+ nobypass [PPC/POWERNV]
+ Disable IOMMU bypass, using IOMMU for PCI devices.
+
+
+ io7= [HW] IO7 for Marvel based alpha systems
+ See comment before marvel_specify_io7 in
+ arch/alpha/kernel/core_marvel.c.
+
+ io_delay= [X86] I/O delay method
+ 0x80
+ Standard port 0x80 based delay
+ 0xed
+ Alternate port 0xed based delay (needed on some systems)
+ udelay
+ Simple two microseconds delay
+ none
+ No delay
+
+ ip= [IP_PNP]
+ See Documentation/filesystems/nfs/nfsroot.txt.
+
+ irqaffinity= [SMP] Set the default irq affinity mask
+ The argument is a cpu list, as described above.
+
+ irqfixup [HW]
+ When an interrupt is not handled search all handlers
+ for it. Intended to get systems with badly broken
+ firmware running.
+
+ irqpoll [HW]
+ When an interrupt is not handled search all handlers
+ for it. Also check all handlers each timer
+ interrupt. Intended to get systems with badly broken
+ firmware running.
+
+ isapnp= [ISAPNP]
+ Format: <RDP>,<reset>,<pci_scan>,<verbosity>
+
+ isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
+ The argument is a cpu list, as described above.
+
+ This option can be used to specify one or more CPUs
+ to isolate from the general SMP balancing and scheduling
+ algorithms. You can move a process onto or off an
+ "isolated" CPU via the CPU affinity syscalls or cpuset.
+ <cpu number> begins at 0 and the maximum value is
+ "number of CPUs in system - 1".
+
+ This option is the preferred way to isolate CPUs. The
+ alternative -- manually setting the CPU mask of all
+ tasks in the system -- can cause problems and
+ suboptimal load balancer performance.
+
+ iucv= [HW,NET]
+
+ ivrs_ioapic [HW,X86_64]
+ Provide an override to the IOAPIC-ID<->DEVICE-ID
+ mapping provided in the IVRS ACPI table. For
+ example, to map IOAPIC-ID decimal 10 to
+ PCI device 00:14.0 write the parameter as:
+ ivrs_ioapic[10]=00:14.0
+
+ ivrs_hpet [HW,X86_64]
+ Provide an override to the HPET-ID<->DEVICE-ID
+ mapping provided in the IVRS ACPI table. For
+ example, to map HPET-ID decimal 0 to
+ PCI device 00:14.0 write the parameter as:
+ ivrs_hpet[0]=00:14.0
+
+ ivrs_acpihid [HW,X86_64]
+ Provide an override to the ACPI-HID:UID<->DEVICE-ID
+ mapping provided in the IVRS ACPI table. For
+ example, to map UART-HID:UID AMD0020:0 to
+ PCI device 00:14.5 write the parameter as:
+ ivrs_acpihid[00:14.5]=AMD0020:0
+
+ js= [HW,JOY] Analog joystick
+ See Documentation/input/joystick.txt.
+
+ nokaslr [KNL]
+ When CONFIG_RANDOMIZE_BASE is set, this disables
+ kernel and module base offset ASLR (Address Space
+ Layout Randomization).
+
+ keepinitrd [HW,ARM]
+
+ kernelcore= [KNL,X86,IA-64,PPC]
+ Format: nn[KMGTPE] | "mirror"
+ This parameter
+ specifies the amount of memory usable by the kernel
+ for non-movable allocations. The requested amount is
+ spread evenly throughout all nodes in the system. The
+ remaining memory in each node is used for Movable
+ pages. In the event, a node is too small to have both
+ kernelcore and Movable pages, kernelcore pages will
+ take priority and other nodes will have a larger number
+ of Movable pages. The Movable zone is used for the
+ allocation of pages that may be reclaimed or moved
+ by the page migration subsystem. This means that
+ HugeTLB pages may not be allocated from this zone.
+ Note that allocations like PTEs-from-HighMem still
+ use the HighMem zone if it exists, and the Normal
+ zone if it does not.
+
+ Instead of specifying the amount of memory (nn[KMGTPE]),
+ you can specify "mirror" option. In case "mirror"
+ option is specified, mirrored (reliable) memory is used
+ for non-movable allocations and remaining memory is used
+ for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
+ so you can NOT specify nn[KMGTPE] and "mirror" at the same
+ time.
+
+ kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
+ Format: <Controller#>[,poll interval]
+ The controller # is the number of the ehci usb debug
+ port as it is probed via PCI. The poll interval is
+ optional and is the number seconds in between
+ each poll cycle to the debug port in case you need
+ the functionality for interrupting the kernel with
+ gdb or control-c on the dbgp connection. When
+ not using this parameter you use sysrq-g to break into
+ the kernel debugger.
+
+ kgdboc= [KGDB,HW] kgdb over consoles.
+ Requires a tty driver that supports console polling,
+ or a supported polling keyboard driver (non-usb).
+ Serial only format: <serial_device>[,baud]
+ keyboard only format: kbd
+ keyboard and serial format: kbd,<serial_device>[,baud]
+ Optional Kernel mode setting:
+ kms, kbd format: kms,kbd
+ kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
+
+ kgdbwait [KGDB] Stop kernel execution and enter the
+ kernel debugger at the earliest opportunity.
+
+ kmac= [MIPS] korina ethernet MAC address.
+ Configure the RouterBoard 532 series on-chip
+ Ethernet adapter MAC address.
+
+ kmemleak= [KNL] Boot-time kmemleak enable/disable
+ Valid arguments: on, off
+ Default: on
+ Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
+ the default is off.
+
+ kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
+ Valid arguments: 0, 1, 2
+ kmemcheck=0 (disabled)
+ kmemcheck=1 (enabled)
+ kmemcheck=2 (one-shot mode)
+ Default: 2 (one-shot mode)
+
+ kstack=N [X86] Print N words from the kernel stack
+ in oops dumps.
+
+ kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
+ Default is 0 (don't ignore, but inject #GP)
+
+ kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
+ KVM MMU at runtime.
+ Default is 0 (off)
+
+ kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
+ Default is 1 (enabled)
+
+ kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
+ for all guests.
+ Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
+
+ kvm-intel.ept= [KVM,Intel] Disable extended page tables
+ (virtualized MMU) support on capable Intel chips.
+ Default is 1 (enabled)
+
+ kvm-intel.emulate_invalid_guest_state=
+ [KVM,Intel] Enable emulation of invalid guest states
+ Default is 0 (disabled)
+
+ kvm-intel.flexpriority=
+ [KVM,Intel] Disable FlexPriority feature (TPR shadow).
+ Default is 1 (enabled)
+
+ kvm-intel.nested=
+ [KVM,Intel] Enable VMX nesting (nVMX).
+ Default is 0 (disabled)
+
+ kvm-intel.unrestricted_guest=
+ [KVM,Intel] Disable unrestricted guest feature
+ (virtualized real and unpaged mode) on capable
+ Intel chips. Default is 1 (enabled)
+
+ kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
+ feature (tagged TLBs) on capable Intel chips.
+ Default is 1 (enabled)
+
+ l2cr= [PPC]
+
+ l3cr= [PPC]
+
+ lapic [X86-32,APIC] Enable the local APIC even if BIOS
+ disabled it.
+
+ lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
+ value for LAPIC timer one-shot implementation. Default
+ back to the programmable timer unit in the LAPIC.
+
+ lapic_timer_c2_ok [X86,APIC] trust the local apic timer
+ in C2 power state.
+
+ libata.dma= [LIBATA] DMA control
+ libata.dma=0 Disable all PATA and SATA DMA
+ libata.dma=1 PATA and SATA Disk DMA only
+ libata.dma=2 ATAPI (CDROM) DMA only
+ libata.dma=4 Compact Flash DMA only
+ Combinations also work, so libata.dma=3 enables DMA
+ for disks and CDROMs, but not CFs.
+
+ libata.ignore_hpa= [LIBATA] Ignore HPA limit
+ libata.ignore_hpa=0 keep BIOS limits (default)
+ libata.ignore_hpa=1 ignore limits, using full disk
+
+ libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
+ when set.
+ Format: <int>
+
+ libata.force= [LIBATA] Force configurations. The format is comma
+ separated list of "[ID:]VAL" where ID is
+ PORT[.DEVICE]. PORT and DEVICE are decimal numbers
+ matching port, link or device. Basically, it matches
+ the ATA ID string printed on console by libata. If
+ the whole ID part is omitted, the last PORT and DEVICE
+ values are used. If ID hasn't been specified yet, the
+ configuration applies to all ports, links and devices.
+
+ If only DEVICE is omitted, the parameter applies to
+ the port and all links and devices behind it. DEVICE
+ number of 0 either selects the first device or the
+ first fan-out link behind PMP device. It does not
+ select the host link. DEVICE number of 15 selects the
+ host link and device attached to it.
+
+ The VAL specifies the configuration to force. As long
+ as there's no ambiguity shortcut notation is allowed.
+ For example, both 1.5 and 1.5G would work for 1.5Gbps.
+ The following configurations can be forced.
+
+ * Cable type: 40c, 80c, short40c, unk, ign or sata.
+ Any ID with matching PORT is used.
+
+ * SATA link speed limit: 1.5Gbps or 3.0Gbps.
+
+ * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
+ udma[/][16,25,33,44,66,100,133] notation is also
+ allowed.
+
+ * [no]ncq: Turn on or off NCQ.
+
+ * [no]ncqtrim: Turn off queued DSM TRIM.
+
+ * nohrst, nosrst, norst: suppress hard, soft
+ and both resets.
+
+ * rstonce: only attempt one reset during
+ hot-unplug link recovery
+
+ * dump_id: dump IDENTIFY data.
+
+ * atapi_dmadir: Enable ATAPI DMADIR bridge support
+
+ * disable: Disable this device.
+
+ If there are multiple matching configurations changing
+ the same attribute, the last one is used.
+
+ memblock=debug [KNL] Enable memblock debug messages.
+
+ load_ramdisk= [RAM] List of ramdisks to load from floppy
+ See Documentation/blockdev/ramdisk.txt.
+
+ lockd.nlm_grace_period=P [NFS] Assign grace period.
+ Format: <integer>
+
+ lockd.nlm_tcpport=N [NFS] Assign TCP port.
+ Format: <integer>
+
+ lockd.nlm_timeout=T [NFS] Assign timeout value.
+ Format: <integer>
+
+ lockd.nlm_udpport=M [NFS] Assign UDP port.
+ Format: <integer>
+
+ locktorture.nreaders_stress= [KNL]
+ Set the number of locking read-acquisition kthreads.
+ Defaults to being automatically set based on the
+ number of online CPUs.
+
+ locktorture.nwriters_stress= [KNL]
+ Set the number of locking write-acquisition kthreads.
+
+ locktorture.onoff_holdoff= [KNL]
+ Set time (s) after boot for CPU-hotplug testing.
+
+ locktorture.onoff_interval= [KNL]
+ Set time (s) between CPU-hotplug operations, or
+ zero to disable CPU-hotplug testing.
+
+ locktorture.shuffle_interval= [KNL]
+ Set task-shuffle interval (jiffies). Shuffling
+ tasks allows some CPUs to go into dyntick-idle
+ mode during the locktorture test.
+
+ locktorture.shutdown_secs= [KNL]
+ Set time (s) after boot system shutdown. This
+ is useful for hands-off automated testing.
+
+ locktorture.stat_interval= [KNL]
+ Time (s) between statistics printk()s.
+
+ locktorture.stutter= [KNL]
+ Time (s) to stutter testing, for example,
+ specifying five seconds causes the test to run for
+ five seconds, wait for five seconds, and so on.
+ This tests the locking primitive's ability to
+ transition abruptly to and from idle.
+
+ locktorture.torture_runnable= [BOOT]
+ Start locktorture running at boot time.
+
+ locktorture.torture_type= [KNL]
+ Specify the locking implementation to test.
+
+ locktorture.verbose= [KNL]
+ Enable additional printk() statements.
+
+ logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
+ Format: <irq>
+
+ loglevel= All Kernel Messages with a loglevel smaller than the
+ console loglevel will be printed to the console. It can
+ also be changed with klogd or other programs. The
+ loglevels are defined as follows:
+
+ 0 (KERN_EMERG) system is unusable
+ 1 (KERN_ALERT) action must be taken immediately
+ 2 (KERN_CRIT) critical conditions
+ 3 (KERN_ERR) error conditions
+ 4 (KERN_WARNING) warning conditions
+ 5 (KERN_NOTICE) normal but significant condition
+ 6 (KERN_INFO) informational
+ 7 (KERN_DEBUG) debug-level messages
+
+ log_buf_len=n[KMG] Sets the size of the printk ring buffer,
+ in bytes. n must be a power of two and greater
+ than the minimal size. The minimal size is defined
+ by LOG_BUF_SHIFT kernel config parameter. There is
+ also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
+ that allows to increase the default size depending on
+ the number of CPUs. See init/Kconfig for more details.
+
+ logo.nologo [FB] Disables display of the built-in Linux logo.
+ This may be used to provide more screen space for
+ kernel log messages and is useful when debugging
+ kernel boot problems.
+
+ lp=0 [LP] Specify parallel ports to use, e.g,
+ lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
+ lp=reset first parallel port). 'lp=0' disables the
+ lp=auto printer driver. 'lp=reset' (which can be
+ specified in addition to the ports) causes
+ attached printers to be reset. Using
+ lp=port1,port2,... specifies the parallel ports
+ to associate lp devices with, starting with
+ lp0. A port specification may be 'none' to skip
+ that lp device, or a parport name such as
+ 'parport0'. Specifying 'lp=auto' instead of a
+ port specification list means that device IDs
+ from each port should be examined, to see if
+ an IEEE 1284-compliant printer is attached; if
+ so, the driver will manage that printer.
+ See also header of drivers/char/lp.c.
+
+ lpj=n [KNL]
+ Sets loops_per_jiffy to given constant, thus avoiding
+ time-consuming boot-time autodetection (up to 250 ms per
+ CPU). 0 enables autodetection (default). To determine
+ the correct value for your kernel, boot with normal
+ autodetection and see what value is printed. Note that
+ on SMP systems the preset will be applied to all CPUs,
+ which is likely to cause problems if your CPUs need
+ significantly divergent settings. An incorrect value
+ will cause delays in the kernel to be wrong, leading to
+ unpredictable I/O errors and other breakage. Although
+ unlikely, in the extreme case this might damage your
+ hardware.
+
+ ltpc= [NET]
+ Format: <io>,<irq>,<dma>
+
+ machvec= [IA-64] Force the use of a particular machine-vector
+ (machvec) in a generic kernel.
+ Example: machvec=hpzx1_swiotlb
+
+ machtype= [Loongson] Share the same kernel image file between different
+ yeeloong laptop.
+ Example: machtype=lemote-yeeloong-2f-7inch
+
+ max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
+ than or equal to this physical address is ignored.
+
+ maxcpus= [SMP] Maximum number of processors that an SMP kernel
+ will bring up during bootup. maxcpus=n : n >= 0 limits
+ the kernel to bring up 'n' processors. Surely after
+ bootup you can bring up the other plugged cpu by executing
+ "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
+ only takes effect during system bootup.
+ While n=0 is a special case, it is equivalent to "nosmp",
+ which also disables the IO APIC.
+
+ max_loop= [LOOP] The number of loop block devices that get
+ (loop.max_loop) unconditionally pre-created at init time. The default
+ number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
+ of statically allocating a predefined number, loop
+ devices can be requested on-demand with the
+ /dev/loop-control interface.
+
+ mce [X86-32] Machine Check Exception
+
+ mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
+
+ md= [HW] RAID subsystems devices and level
+ See Documentation/admin-guide/md.rst.
+
+ mdacon= [MDA]
+ Format: <first>,<last>
+ Specifies range of consoles to be captured by the MDA.
+
+ mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
+ Amount of memory to be used when the kernel is not able
+ to see the whole system memory or for test.
+ [X86] Work as limiting max address. Use together
+ with memmap= to avoid physical address space collisions.
+ Without memmap= PCI devices could be placed at addresses
+ belonging to unused RAM.
+
+ mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
+ memory.
+
+ memchunk=nn[KMG]
+ [KNL,SH] Allow user to override the default size for
+ per-device physically contiguous DMA buffers.
+
+ memhp_default_state=online/offline
+ [KNL] Set the initial state for the memory hotplug
+ onlining policy. If not specified, the default value is
+ set according to the
+ CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
+ option.
+ See Documentation/memory-hotplug.txt.
+
+ memmap=exactmap [KNL,X86] Enable setting of an exact
+ E820 memory map, as specified by the user.
+ Such memmap=exactmap lines can be constructed based on
+ BIOS output or other requirements. See the memmap=nn@ss
+ option description.
+
+ memmap=nn[KMG]@ss[KMG]
+ [KNL] Force usage of a specific region of memory.
+ Region of memory to be used is from ss to ss+nn.
+
+ memmap=nn[KMG]#ss[KMG]
+ [KNL,ACPI] Mark specific memory as ACPI data.
+ Region of memory to be marked is from ss to ss+nn.
+
+ memmap=nn[KMG]$ss[KMG]
+ [KNL,ACPI] Mark specific memory as reserved.
+ Region of memory to be reserved is from ss to ss+nn.
+ Example: Exclude memory from 0x18690000-0x1869ffff
+ memmap=64K$0x18690000
+ or
+ memmap=0x10000$0x18690000
+
+ memmap=nn[KMG]!ss[KMG]
+ [KNL,X86] Mark specific memory as protected.
+ Region of memory to be used, from ss to ss+nn.
+ The memory region may be marked as e820 type 12 (0xc)
+ and is NVDIMM or ADR memory.
+
+ memory_corruption_check=0/1 [X86]
+ Some BIOSes seem to corrupt the first 64k of
+ memory when doing things like suspend/resume.
+ Setting this option will scan the memory
+ looking for corruption. Enabling this will
+ both detect corruption and prevent the kernel
+ from using the memory being corrupted.
+ However, its intended as a diagnostic tool; if
+ repeatable BIOS-originated corruption always
+ affects the same memory, you can use memmap=
+ to prevent the kernel from using that memory.
+
+ memory_corruption_check_size=size [X86]
+ By default it checks for corruption in the low
+ 64k, making this memory unavailable for normal
+ use. Use this parameter to scan for
+ corruption in more or less memory.
+
+ memory_corruption_check_period=seconds [X86]
+ By default it checks for corruption every 60
+ seconds. Use this parameter to check at some
+ other rate. 0 disables periodic checking.
+
+ memtest= [KNL,X86,ARM] Enable memtest
+ Format: <integer>
+ default : 0 <disable>
+ Specifies the number of memtest passes to be
+ performed. Each pass selects another test
+ pattern from a given set of patterns. Memtest
+ fills the memory with this pattern, validates
+ memory contents and reserves bad memory
+ regions that are detected.
+
+ meye.*= [HW] Set MotionEye Camera parameters
+ See Documentation/video4linux/meye.txt.
+
+ mfgpt_irq= [IA-32] Specify the IRQ to use for the
+ Multi-Function General Purpose Timers on AMD Geode
+ platforms.
+
+ mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
+ the BIOS has incorrectly applied a workaround. TinyBIOS
+ version 0.98 is known to be affected, 0.99 fixes the
+ problem by letting the user disable the workaround.
+
+ mga= [HW,DRM]
+
+ min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
+ physical address is ignored.
+
+ mini2440= [ARM,HW,KNL]
+ Format:[0..2][b][c][t]
+ Default: "0tb"
+ MINI2440 configuration specification:
+ 0 - The attached screen is the 3.5" TFT
+ 1 - The attached screen is the 7" TFT
+ 2 - The VGA Shield is attached (1024x768)
+ Leaving out the screen size parameter will not load
+ the TFT driver, and the framebuffer will be left
+ unconfigured.
+ b - Enable backlight. The TFT backlight pin will be
+ linked to the kernel VESA blanking code and a GPIO
+ LED. This parameter is not necessary when using the
+ VGA shield.
+ c - Enable the s3c camera interface.
+ t - Reserved for enabling touchscreen support. The
+ touchscreen support is not enabled in the mainstream
+ kernel as of 2.6.30, a preliminary port can be found
+ in the "bleeding edge" mini2440 support kernel at
+ http://repo.or.cz/w/linux-2.6/mini2440.git
+
+ mminit_loglevel=
+ [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
+ parameter allows control of the logging verbosity for
+ the additional memory initialisation checks. A value
+ of 0 disables mminit logging and a level of 4 will
+ log everything. Information is printed at KERN_DEBUG
+ so loglevel=8 may also need to be specified.
+
+ module.sig_enforce
+ [KNL] When CONFIG_MODULE_SIG is set, this means that
+ modules without (valid) signatures will fail to load.
+ Note that if CONFIG_MODULE_SIG_FORCE is set, that
+ is always true, so this option does nothing.
+
+ module_blacklist= [KNL] Do not load a comma-separated list of
+ modules. Useful for debugging problem modules.
+
+ mousedev.tap_time=
+ [MOUSE] Maximum time between finger touching and
+ leaving touchpad surface for touch to be considered
+ a tap and be reported as a left button click (for
+ touchpads working in absolute mode only).
+ Format: <msecs>
+ mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
+ reporting absolute coordinates, such as tablets
+ mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
+ reporting absolute coordinates, such as tablets
+
+ movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
+ is similar to kernelcore except it specifies the
+ amount of memory used for migratable allocations.
+ If both kernelcore and movablecore is specified,
+ then kernelcore will be at *least* the specified
+ value but may be more. If movablecore on its own
+ is specified, the administrator must be careful
+ that the amount of memory usable for all allocations
+ is not too small.
+
+ movable_node [KNL,X86] Boot-time switch to enable the effects
+ of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
+
+ MTD_Partition= [MTD]
+ Format: <name>,<region-number>,<size>,<offset>
+
+ MTD_Region= [MTD] Format:
+ <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
+
+ mtdparts= [MTD]
+ See drivers/mtd/cmdlinepart.c.
+
+ multitce=off [PPC] This parameter disables the use of the pSeries
+ firmware feature for updating multiple TCE entries
+ at a time.
+
+ onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
+
+ Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
+
+ boundary - index of last SLC block on Flex-OneNAND.
+ The remaining blocks are configured as MLC blocks.
+ lock - Configure if Flex-OneNAND boundary should be locked.
+ Once locked, the boundary cannot be changed.
+ 1 indicates lock status, 0 indicates unlock status.
+
+ mtdset= [ARM]
+ ARM/S3C2412 JIVE boot control
+
+ See arch/arm/mach-s3c2412/mach-jive.c
+
+ mtouchusb.raw_coordinates=
+ [HW] Make the MicroTouch USB driver use raw coordinates
+ ('y', default) or cooked coordinates ('n')
+
+ mtrr_chunk_size=nn[KMG] [X86]
+ used for mtrr cleanup. It is largest continuous chunk
+ that could hold holes aka. UC entries.
+
+ mtrr_gran_size=nn[KMG] [X86]
+ Used for mtrr cleanup. It is granularity of mtrr block.
+ Default is 1.
+ Large value could prevent small alignment from
+ using up MTRRs.
+
+ mtrr_spare_reg_nr=n [X86]
+ Format: <integer>
+ Range: 0,7 : spare reg number
+ Default : 1
+ Used for mtrr cleanup. It is spare mtrr entries number.
+ Set to 2 or more if your graphical card needs more.
+
+ n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
+
+ netdev= [NET] Network devices parameters
+ Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
+ Note that mem_start is often overloaded to mean
+ something different and driver-specific.
+ This usage is only documented in each driver source
+ file if at all.
+
+ nf_conntrack.acct=
+ [NETFILTER] Enable connection tracking flow accounting
+ 0 to disable accounting
+ 1 to enable accounting
+ Default value is 0.
+
+ nfsaddrs= [NFS] Deprecated. Use ip= instead.
+ See Documentation/filesystems/nfs/nfsroot.txt.
+
+ nfsroot= [NFS] nfs root filesystem for disk-less boxes.
+ See Documentation/filesystems/nfs/nfsroot.txt.
+
+ nfsrootdebug [NFS] enable nfsroot debugging messages.
+ See Documentation/filesystems/nfs/nfsroot.txt.
+
+ nfs.callback_nr_threads=
+ [NFSv4] set the total number of threads that the
+ NFS client will assign to service NFSv4 callback
+ requests.
+
+ nfs.callback_tcpport=
+ [NFS] set the TCP port on which the NFSv4 callback
+ channel should listen.
+
+ nfs.cache_getent=
+ [NFS] sets the pathname to the program which is used
+ to update the NFS client cache entries.
+
+ nfs.cache_getent_timeout=
+ [NFS] sets the timeout after which an attempt to
+ update a cache entry is deemed to have failed.
+
+ nfs.idmap_cache_timeout=
+ [NFS] set the maximum lifetime for idmapper cache
+ entries.
+
+ nfs.enable_ino64=
+ [NFS] enable 64-bit inode numbers.
+ If zero, the NFS client will fake up a 32-bit inode
+ number for the readdir() and stat() syscalls instead
+ of returning the full 64-bit number.
+ The default is to return 64-bit inode numbers.
+
+ nfs.max_session_cb_slots=
+ [NFSv4.1] Sets the maximum number of session
+ slots the client will assign to the callback
+ channel. This determines the maximum number of
+ callbacks the client will process in parallel for
+ a particular server.
+
+ nfs.max_session_slots=
+ [NFSv4.1] Sets the maximum number of session slots
+ the client will attempt to negotiate with the server.
+ This limits the number of simultaneous RPC requests
+ that the client can send to the NFSv4.1 server.
+ Note that there is little point in setting this
+ value higher than the max_tcp_slot_table_limit.
+
+ nfs.nfs4_disable_idmapping=
+ [NFSv4] When set to the default of '1', this option
+ ensures that both the RPC level authentication
+ scheme and the NFS level operations agree to use
+ numeric uids/gids if the mount is using the
+ 'sec=sys' security flavour. In effect it is
+ disabling idmapping, which can make migration from
+ legacy NFSv2/v3 systems to NFSv4 easier.
+ Servers that do not support this mode of operation
+ will be autodetected by the client, and it will fall
+ back to using the idmapper.
+ To turn off this behaviour, set the value to '0'.
+ nfs.nfs4_unique_id=
+ [NFS4] Specify an additional fixed unique ident-
+ ification string that NFSv4 clients can insert into
+ their nfs_client_id4 string. This is typically a
+ UUID that is generated at system install time.
+
+ nfs.send_implementation_id =
+ [NFSv4.1] Send client implementation identification
+ information in exchange_id requests.
+ If zero, no implementation identification information
+ will be sent.
+ The default is to send the implementation identification
+ information.
+
+ nfs.recover_lost_locks =
+ [NFSv4] Attempt to recover locks that were lost due
+ to a lease timeout on the server. Please note that
+ doing this risks data corruption, since there are
+ no guarantees that the file will remain unchanged
+ after the locks are lost.
+ If you want to enable the kernel legacy behaviour of
+ attempting to recover these locks, then set this
+ parameter to '1'.
+ The default parameter value of '0' causes the kernel
+ not to attempt recovery of lost locks.
+
+ nfs4.layoutstats_timer =
+ [NFSv4.2] Change the rate at which the kernel sends
+ layoutstats to the pNFS metadata server.
+
+ Setting this to value to 0 causes the kernel to use
+ whatever value is the default set by the layout
+ driver. A non-zero value sets the minimum interval
+ in seconds between layoutstats transmissions.
+
+ nfsd.nfs4_disable_idmapping=
+ [NFSv4] When set to the default of '1', the NFSv4
+ server will return only numeric uids and gids to
+ clients using auth_sys, and will accept numeric uids
+ and gids from such clients. This is intended to ease
+ migration from NFSv2/v3.
+
+ objlayoutdriver.osd_login_prog=
+ [NFS] [OBJLAYOUT] sets the pathname to the program which
+ is used to automatically discover and login into new
+ osd-targets. Please see:
+ Documentation/filesystems/pnfs.txt for more explanations
+
+ nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
+ when a NMI is triggered.
+ Format: [state][,regs][,debounce][,die]
+
+ nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
+ Format: [panic,][nopanic,][num]
+ Valid num: 0 or 1
+ 0 - turn hardlockup detector in nmi_watchdog off
+ 1 - turn hardlockup detector in nmi_watchdog on
+ When panic is specified, panic when an NMI watchdog
+ timeout occurs (or 'nopanic' to override the opposite
+ default). To disable both hard and soft lockup detectors,
+ please see 'nowatchdog'.
+ This is useful when you use a panic=... timeout and
+ need the box quickly up again.
+
+ netpoll.carrier_timeout=
+ [NET] Specifies amount of time (in seconds) that
+ netpoll should wait for a carrier. By default netpoll
+ waits 4 seconds.
+
+ no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
+ emulation library even if a 387 maths coprocessor
+ is present.
+
+ no_console_suspend
+ [HW] Never suspend the console
+ Disable suspending of consoles during suspend and
+ hibernate operations. Once disabled, debugging
+ messages can reach various consoles while the rest
+ of the system is being put to sleep (ie, while
+ debugging driver suspend/resume hooks). This may
+ not work reliably with all consoles, but is known
+ to work with serial and VGA consoles.
+ To facilitate more flexible debugging, we also add
+ console_suspend, a printk module parameter to control
+ it. Users could use console_suspend (usually
+ /sys/module/printk/parameters/console_suspend) to
+ turn on/off it dynamically.
+
+ noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
+ caches in the slab allocator. Saves per-node memory,
+ but will impact performance.
+
+ noalign [KNL,ARM]
+
+ noapic [SMP,APIC] Tells the kernel to not make use of any
+ IOAPICs that may be present in the system.
+
+ noautogroup Disable scheduler automatic task group creation.
+
+ nobats [PPC] Do not use BATs for mapping kernel lowmem
+ on "Classic" PPC cores.
+
+ nocache [ARM]
+
+ noclflush [BUGS=X86] Don't use the CLFLUSH instruction
+
+ nodelayacct [KNL] Disable per-task delay accounting
+
+ nodsp [SH] Disable hardware DSP at boot time.
+
+ noefi Disable EFI runtime services support.
+
+ noexec [IA-64]
+
+ noexec [X86]
+ On X86-32 available only on PAE configured kernels.
+ noexec=on: enable non-executable mappings (default)
+ noexec=off: disable non-executable mappings
+
+ nosmap [X86]
+ Disable SMAP (Supervisor Mode Access Prevention)
+ even if it is supported by processor.
+
+ nosmep [X86]
+ Disable SMEP (Supervisor Mode Execution Prevention)
+ even if it is supported by processor.
+
+ noexec32 [X86-64]
+ This affects only 32-bit executables.
+ noexec32=on: enable non-executable mappings (default)
+ read doesn't imply executable mappings
+ noexec32=off: disable non-executable mappings
+ read implies executable mappings
+
+ nofpu [MIPS,SH] Disable hardware FPU at boot time.
+
+ nofxsr [BUGS=X86-32] Disables x86 floating point extended
+ register save and restore. The kernel will only save
+ legacy floating-point registers on task switch.
+
+ nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
+
+ nosmt [KNL,S390] Disable symmetric multithreading (SMT).
+ Equivalent to smt=1.
+
+ noxsave [BUGS=X86] Disables x86 extended register state save
+ and restore using xsave. The kernel will fallback to
+ enabling legacy floating-point and sse state.
+
+ noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
+ register states. The kernel will fall back to use
+ xsave to save the states. By using this parameter,
+ performance of saving the states is degraded because
+ xsave doesn't support modified optimization while
+ xsaveopt supports it on xsaveopt enabled systems.
+
+ noxsaves [X86] Disables xsaves and xrstors used in saving and
+ restoring x86 extended register state in compacted
+ form of xsave area. The kernel will fall back to use
+ xsaveopt and xrstor to save and restore the states
+ in standard form of xsave area. By using this
+ parameter, xsave area per process might occupy more
+ memory on xsaves enabled systems.
+
+ nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
+ wfi(ARM) instruction doesn't work correctly and not to
+ use it. This is also useful when using JTAG debugger.
+
+ no_file_caps Tells the kernel not to honor file capabilities. The
+ only way then for a file to be executed with privilege
+ is to be setuid root or executed by root.
+
+ nohalt [IA-64] Tells the kernel not to use the power saving
+ function PAL_HALT_LIGHT when idle. This increases
+ power-consumption. On the positive side, it reduces
+ interrupt wake-up latency, which may improve performance
+ in certain environments such as networked servers or
+ real-time systems.
+
+ nohibernate [HIBERNATION] Disable hibernation and resume.
+
+ nohz= [KNL] Boottime enable/disable dynamic ticks
+ Valid arguments: on, off
+ Default: on
+
+ nohz_full= [KNL,BOOT]
+ The argument is a cpu list, as described above.
+ In kernels built with CONFIG_NO_HZ_FULL=y, set
+ the specified list of CPUs whose tick will be stopped
+ whenever possible. The boot CPU will be forced outside
+ the range to maintain the timekeeping.
+ The CPUs in this range must also be included in the
+ rcu_nocbs= set.
+
+ noiotrap [SH] Disables trapped I/O port accesses.
+
+ noirqdebug [X86-32] Disables the code which attempts to detect and
+ disable unhandled interrupt sources.
+
+ no_timer_check [X86,APIC] Disables the code which tests for
+ broken timer IRQ sources.
+
+ noisapnp [ISAPNP] Disables ISA PnP code.
+
+ noinitrd [RAM] Tells the kernel not to load any configured
+ initial RAM disk.
+
+ nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
+ remapping.
+ [Deprecated - use intremap=off]
+
+ nointroute [IA-64]
+
+ noinvpcid [X86] Disable the INVPCID cpu feature.
+
+ nojitter [IA-64] Disables jitter checking for ITC timers.
+
+ no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
+
+ no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
+ fault handling.
+
+ no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
+ steal time is computed, but won't influence scheduler
+ behaviour
+
+ nolapic [X86-32,APIC] Do not enable or use the local APIC.
+
+ nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
+
+ noltlbs [PPC] Do not use large page/tlb entries for kernel
+ lowmem mapping on PPC40x and PPC8xx
+
+ nomca [IA-64] Disable machine check abort handling
+
+ nomce [X86-32] Disable Machine Check Exception
+
+ nomfgpt [X86-32] Disable Multi-Function General Purpose
+ Timer usage (for AMD Geode machines).
+
+ nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
+ shutdown the other cpus. Instead use the REBOOT_VECTOR
+ irq.
+
+ nomodule Disable module load
+
+ nopat [X86] Disable PAT (page attribute table extension of
+ pagetables) support.
+
+ norandmaps Don't use address space randomization. Equivalent to
+ echo 0 > /proc/sys/kernel/randomize_va_space
+
+ noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
+
+ noreplace-smp [X86-32,SMP] Don't replace SMP instructions
+ with UP alternatives
+
+ nordrand [X86] Disable kernel use of the RDRAND and
+ RDSEED instructions even if they are supported
+ by the processor. RDRAND and RDSEED are still
+ available to user space applications.
+
+ noresume [SWSUSP] Disables resume and restores original swap
+ space.
+
+ no-scroll [VGA] Disables scrollback.
+ This is required for the Braillex ib80-piezo Braille
+ reader made by F.H. Papenmeier (Germany).
+
+ nosbagart [IA-64]
+
+ nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
+
+ nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
+ and disable the IO APIC. legacy for "maxcpus=0".
+
+ nosoftlockup [KNL] Disable the soft-lockup detector.
+
+ nosync [HW,M68K] Disables sync negotiation for all devices.
+
+ notsc [BUGS=X86-32] Disable Time Stamp Counter
+
+ nowatchdog [KNL] Disable both lockup detectors, i.e.
+ soft-lockup and NMI watchdog (hard-lockup).
+
+ nowb [ARM]
+
+ nox2apic [X86-64,APIC] Do not enable x2APIC mode.
+
+ cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
+ CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
+ Some features depend on CPU0. Known dependencies are:
+ 1. Resume from suspend/hibernate depends on CPU0.
+ Suspend/hibernate will fail if CPU0 is offline and you
+ need to online CPU0 before suspend/hibernate.
+ 2. PIC interrupts also depend on CPU0. CPU0 can't be
+ removed if a PIC interrupt is detected.
+ It's said poweroff/reboot may depend on CPU0 on some
+ machines although I haven't seen such issues so far
+ after CPU0 is offline on a few tested machines.
+ If the dependencies are under your control, you can
+ turn on cpu0_hotplug.
+
+ nptcg= [IA-64] Override max number of concurrent global TLB
+ purges which is reported from either PAL_VM_SUMMARY or
+ SAL PALO.
+
+ nr_cpus= [SMP] Maximum number of processors that an SMP kernel
+ could support. nr_cpus=n : n >= 1 limits the kernel to
+ support 'n' processors. It could be larger than the
+ number of already plugged CPU during bootup, later in
+ runtime you can physically add extra cpu until it reaches
+ n. So during boot up some boot time memory for per-cpu
+ variables need be pre-allocated for later physical cpu
+ hot plugging.
+
+ nr_uarts= [SERIAL] maximum number of UARTs to be registered.
+
+ numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
+ Allowed values are enable and disable
+
+ numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
+ one of ['zone', 'node', 'default'] can be specified
+ This can be set from sysctl after boot.
+ See Documentation/sysctl/vm.txt for details.
+
+ ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
+ See Documentation/debugging-via-ohci1394.txt for more
+ info.
+
+ olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
+ Rather than timing out after 20 ms if an EC
+ command is not properly ACKed, override the length
+ of the timeout. We have interrupts disabled while
+ waiting for the ACK, so if this is set too high
+ interrupts *may* be lost!
+
+ omap_mux= [OMAP] Override bootloader pin multiplexing.
+ Format: <mux_mode0.mode_name=value>...
+ For example, to override I2C bus2:
+ omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
+
+ oprofile.timer= [HW]
+ Use timer interrupt instead of performance counters
+
+ oprofile.cpu_type= Force an oprofile cpu type
+ This might be useful if you have an older oprofile
+ userland or if you want common events.
+ Format: { arch_perfmon }
+ arch_perfmon: [X86] Force use of architectural
+ perfmon on Intel CPUs instead of the
+ CPU specific event set.
+ timer: [X86] Force use of architectural NMI
+ timer mode (see also oprofile.timer
+ for generic hr timer mode)
+
+ oops=panic Always panic on oopses. Default is to just kill the
+ process, but there is a small probability of
+ deadlocking the machine.
+ This will also cause panics on machine check exceptions.
+ Useful together with panic=30 to trigger a reboot.
+
+ OSS [HW,OSS]
+ See Documentation/sound/oss/oss-parameters.txt
+
+ page_owner= [KNL] Boot-time page_owner enabling option.
+ Storage of the information about who allocated
+ each page is disabled in default. With this switch,
+ we can turn it on.
+ on: enable the feature
+
+ page_poison= [KNL] Boot-time parameter changing the state of
+ poisoning on the buddy allocator.
+ off: turn off poisoning
+ on: turn on poisoning
+
+ panic= [KNL] Kernel behaviour on panic: delay <timeout>
+ timeout > 0: seconds before rebooting
+ timeout = 0: wait forever
+ timeout < 0: reboot immediately
+ Format: <timeout>
+
+ panic_on_warn panic() instead of WARN(). Useful to cause kdump
+ on a WARN().
+
+ crash_kexec_post_notifiers
+ Run kdump after running panic-notifiers and dumping
+ kmsg. This only for the users who doubt kdump always
+ succeeds in any situation.
+ Note that this also increases risks of kdump failure,
+ because some panic notifiers can make the crashed
+ kernel more unstable.
+
+ parkbd.port= [HW] Parallel port number the keyboard adapter is
+ connected to, default is 0.
+ Format: <parport#>
+ parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
+ 0 for XT, 1 for AT (default is AT).
+ Format: <mode>
+
+ parport= [HW,PPT] Specify parallel ports. 0 disables.
+ Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
+ Use 'auto' to force the driver to use any
+ IRQ/DMA settings detected (the default is to
+ ignore detected IRQ/DMA settings because of
+ possible conflicts). You can specify the base
+ address, IRQ, and DMA settings; IRQ and DMA
+ should be numbers, or 'auto' (for using detected
+ settings on that particular port), or 'nofifo'
+ (to avoid using a FIFO even if it is detected).
+ Parallel ports are assigned in the order they
+ are specified on the command line, starting
+ with parport0.
+
+ parport_init_mode= [HW,PPT]
+ Configure VIA parallel port to operate in
+ a specific mode. This is necessary on Pegasos
+ computer where firmware has no options for setting
+ up parallel port mode and sets it to spp.
+ Currently this function knows 686a and 8231 chips.
+ Format: [spp|ps2|epp|ecp|ecpepp]
+
+ pause_on_oops=
+ Halt all CPUs after the first oops has been printed for
+ the specified number of seconds. This is to be used if
+ your oopses keep scrolling off the screen.
+
+ pcbit= [HW,ISDN]
+
+ pcd. [PARIDE]
+ See header of drivers/block/paride/pcd.c.
+ See also Documentation/blockdev/paride.txt.
+
+ pci=option[,option...] [PCI] various PCI subsystem options:
+ earlydump [X86] dump PCI config space before the kernel
+ changes anything
+ off [X86] don't probe for the PCI bus
+ bios [X86-32] force use of PCI BIOS, don't access
+ the hardware directly. Use this if your machine
+ has a non-standard PCI host bridge.
+ nobios [X86-32] disallow use of PCI BIOS, only direct
+ hardware access methods are allowed. Use this
+ if you experience crashes upon bootup and you
+ suspect they are caused by the BIOS.
+ conf1 [X86] Force use of PCI Configuration Access
+ Mechanism 1 (config address in IO port 0xCF8,
+ data in IO port 0xCFC, both 32-bit).
+ conf2 [X86] Force use of PCI Configuration Access
+ Mechanism 2 (IO port 0xCF8 is an 8-bit port for
+ the function, IO port 0xCFA, also 8-bit, sets
+ bus number. The config space is then accessed
+ through ports 0xC000-0xCFFF).
+ See http://wiki.osdev.org/PCI for more info
+ on the configuration access mechanisms.
+ noaer [PCIE] If the PCIEAER kernel config parameter is
+ enabled, this kernel boot option can be used to
+ disable the use of PCIE advanced error reporting.
+ nodomains [PCI] Disable support for multiple PCI
+ root domains (aka PCI segments, in ACPI-speak).
+ nommconf [X86] Disable use of MMCONFIG for PCI
+ Configuration
+ check_enable_amd_mmconf [X86] check for and enable
+ properly configured MMIO access to PCI
+ config space on AMD family 10h CPU
+ nomsi [MSI] If the PCI_MSI kernel config parameter is
+ enabled, this kernel boot option can be used to
+ disable the use of MSI interrupts system-wide.
+ noioapicquirk [APIC] Disable all boot interrupt quirks.
+ Safety option to keep boot IRQs enabled. This
+ should never be necessary.
+ ioapicreroute [APIC] Enable rerouting of boot IRQs to the
+ primary IO-APIC for bridges that cannot disable
+ boot IRQs. This fixes a source of spurious IRQs
+ when the system masks IRQs.
+ noioapicreroute [APIC] Disable workaround that uses the
+ boot IRQ equivalent of an IRQ that connects to
+ a chipset where boot IRQs cannot be disabled.
+ The opposite of ioapicreroute.
+ biosirq [X86-32] Use PCI BIOS calls to get the interrupt
+ routing table. These calls are known to be buggy
+ on several machines and they hang the machine
+ when used, but on other computers it's the only
+ way to get the interrupt routing table. Try
+ this option if the kernel is unable to allocate
+ IRQs or discover secondary PCI buses on your
+ motherboard.
+ rom [X86] Assign address space to expansion ROMs.
+ Use with caution as certain devices share
+ address decoders between ROMs and other
+ resources.
+ norom [X86] Do not assign address space to
+ expansion ROMs that do not already have
+ BIOS assigned address ranges.
+ nobar [X86] Do not assign address space to the
+ BARs that weren't assigned by the BIOS.
+ irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
+ assigned automatically to PCI devices. You can
+ make the kernel exclude IRQs of your ISA cards
+ this way.
+ pirqaddr=0xAAAAA [X86] Specify the physical address
+ of the PIRQ table (normally generated
+ by the BIOS) if it is outside the
+ F0000h-100000h range.
+ lastbus=N [X86] Scan all buses thru bus #N. Can be
+ useful if the kernel is unable to find your
+ secondary buses and you want to tell it
+ explicitly which ones they are.
+ assign-busses [X86] Always assign all PCI bus
+ numbers ourselves, overriding
+ whatever the firmware may have done.
+ usepirqmask [X86] Honor the possible IRQ mask stored
+ in the BIOS $PIR table. This is needed on
+ some systems with broken BIOSes, notably
+ some HP Pavilion N5400 and Omnibook XE3
+ notebooks. This will have no effect if ACPI
+ IRQ routing is enabled.
+ noacpi [X86] Do not use ACPI for IRQ routing
+ or for PCI scanning.
+ use_crs [X86] Use PCI host bridge window information
+ from ACPI. On BIOSes from 2008 or later, this
+ is enabled by default. If you need to use this,
+ please report a bug.
+ nocrs [X86] Ignore PCI host bridge windows from ACPI.
+ If you need to use this, please report a bug.
+ routeirq Do IRQ routing for all PCI devices.
+ This is normally done in pci_enable_device(),
+ so this option is a temporary workaround
+ for broken drivers that don't call it.
+ skip_isa_align [X86] do not align io start addr, so can
+ handle more pci cards
+ noearly [X86] Don't do any early type 1 scanning.
+ This might help on some broken boards which
+ machine check when some devices' config space
+ is read. But various workarounds are disabled
+ and some IOMMU drivers will not work.
+ bfsort Sort PCI devices into breadth-first order.
+ This sorting is done to get a device
+ order compatible with older (<= 2.4) kernels.
+ nobfsort Don't sort PCI devices into breadth-first order.
+ pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
+ tuning and use the BIOS-configured MPS defaults.
+ pcie_bus_safe Set every device's MPS to the largest value
+ supported by all devices below the root complex.
+ pcie_bus_perf Set device MPS to the largest allowable MPS
+ based on its parent bus. Also set MRRS (Max
+ Read Request Size) to the largest supported
+ value (no larger than the MPS that the device
+ or bus can support) for best performance.
+ pcie_bus_peer2peer Set every device's MPS to 128B, which
+ every device is guaranteed to support. This
+ configuration allows peer-to-peer DMA between
+ any pair of devices, possibly at the cost of
+ reduced performance. This also guarantees
+ that hot-added devices will work.
+ cbiosize=nn[KMG] The fixed amount of bus space which is
+ reserved for the CardBus bridge's IO window.
+ The default value is 256 bytes.
+ cbmemsize=nn[KMG] The fixed amount of bus space which is
+ reserved for the CardBus bridge's memory
+ window. The default value is 64 megabytes.
+ resource_alignment=
+ Format:
+ [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
+ [<order of align>@]pci:<vendor>:<device>\
+ [:<subvendor>:<subdevice>][; ...]
+ Specifies alignment and device to reassign
+ aligned memory resources.
+ If <order of align> is not specified,
+ PAGE_SIZE is used as alignment.
+ PCI-PCI bridge can be specified, if resource
+ windows need to be expanded.
+ To specify the alignment for several
+ instances of a device, the PCI vendor,
+ device, subvendor, and subdevice may be
+ specified, e.g., 4096@pci:8086:9c22:103c:198f
+ ecrc= Enable/disable PCIe ECRC (transaction layer
+ end-to-end CRC checking).
+ bios: Use BIOS/firmware settings. This is the
+ the default.
+ off: Turn ECRC off
+ on: Turn ECRC on.
+ hpiosize=nn[KMG] The fixed amount of bus space which is
+ reserved for hotplug bridge's IO window.
+ Default size is 256 bytes.
+ hpmemsize=nn[KMG] The fixed amount of bus space which is
+ reserved for hotplug bridge's memory window.
+ Default size is 2 megabytes.
+ hpbussize=nn The minimum amount of additional bus numbers
+ reserved for buses below a hotplug bridge.
+ Default is 1.
+ realloc= Enable/disable reallocating PCI bridge resources
+ if allocations done by BIOS are too small to
+ accommodate resources required by all child
+ devices.
+ off: Turn realloc off
+ on: Turn realloc on
+ realloc same as realloc=on
+ noari do not use PCIe ARI.
+ pcie_scan_all Scan all possible PCIe devices. Otherwise we
+ only look for one device below a PCIe downstream
+ port.
+
+ pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
+ Management.
+ off Disable ASPM.
+ force Enable ASPM even on devices that claim not to support it.
+ WARNING: Forcing ASPM on may cause system lockups.
+
+ pcie_hp= [PCIE] PCI Express Hotplug driver options:
+ nomsi Do not use MSI for PCI Express Native Hotplug (this
+ makes all PCIe ports use INTx for hotplug services).
+
+ pcie_ports= [PCIE] PCIe ports handling:
+ auto Ask the BIOS whether or not to use native PCIe services
+ associated with PCIe ports (PME, hot-plug, AER). Use
+ them only if that is allowed by the BIOS.
+ native Use native PCIe services associated with PCIe ports
+ unconditionally.
+ compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
+ ports driver.
+
+ pcie_port_pm= [PCIE] PCIe port power management handling:
+ off Disable power management of all PCIe ports
+ force Forcibly enable power management of all PCIe ports
+
+ pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
+ nomsi Do not use MSI for native PCIe PME signaling (this makes
+ all PCIe root ports use INTx for all services).
+
+ pcmv= [HW,PCMCIA] BadgePAD 4
+
+ pd_ignore_unused
+ [PM]
+ Keep all power-domains already enabled by bootloader on,
+ even if no driver has claimed them. This is useful
+ for debug and development, but should not be
+ needed on a platform with proper driver support.
+
+ pd. [PARIDE]
+ See Documentation/blockdev/paride.txt.
+
+ pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
+ boot time.
+ Format: { 0 | 1 }
+ See arch/parisc/kernel/pdc_chassis.c
+
+ percpu_alloc= Select which percpu first chunk allocator to use.
+ Currently supported values are "embed" and "page".
+ Archs may support subset or none of the selections.
+ See comments in mm/percpu.c for details on each
+ allocator. This parameter is primarily for debugging
+ and performance comparison.
+
+ pf. [PARIDE]
+ See Documentation/blockdev/paride.txt.
+
+ pg. [PARIDE]
+ See Documentation/blockdev/paride.txt.
+
+ pirq= [SMP,APIC] Manual mp-table setup
+ See Documentation/x86/i386/IO-APIC.txt.
+
+ plip= [PPT,NET] Parallel port network link
+ Format: { parport<nr> | timid | 0 }
+ See also Documentation/parport.txt.
+
+ pmtmr= [X86] Manual setup of pmtmr I/O Port.
+ Override pmtimer IOPort with a hex value.
+ e.g. pmtmr=0x508
+
+ pnp.debug=1 [PNP]
+ Enable PNP debug messages (depends on the
+ CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
+ via /sys/module/pnp/parameters/debug. We always show
+ current resource usage; turning this on also shows
+ possible settings and some assignment information.
+
+ pnpacpi= [ACPI]
+ { off }
+
+ pnpbios= [ISAPNP]
+ { on | off | curr | res | no-curr | no-res }
+
+ pnp_reserve_irq=
+ [ISAPNP] Exclude IRQs for the autoconfiguration
+
+ pnp_reserve_dma=
+ [ISAPNP] Exclude DMAs for the autoconfiguration
+
+ pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
+ Ranges are in pairs (I/O port base and size).
+
+ pnp_reserve_mem=
+ [ISAPNP] Exclude memory regions for the
+ autoconfiguration.
+ Ranges are in pairs (memory base and size).
+
+ ports= [IP_VS_FTP] IPVS ftp helper module
+ Default is 21.
+ Up to 8 (IP_VS_APP_MAX_PORTS) ports
+ may be specified.
+ Format: <port>,<port>....
+
+ ppc_strict_facility_enable
+ [PPC] This option catches any kernel floating point,
+ Altivec, VSX and SPE outside of regions specifically
+ allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
+ There is some performance impact when enabling this.
+
+ print-fatal-signals=
+ [KNL] debug: print fatal signals
+
+ If enabled, warn about various signal handling
+ related application anomalies: too many signals,
+ too many POSIX.1 timers, fatal signals causing a
+ coredump - etc.
+
+ If you hit the warning due to signal overflow,
+ you might want to try "ulimit -i unlimited".
+
+ default: off.
+
+ printk.always_kmsg_dump=
+ Trigger kmsg_dump for cases other than kernel oops or
+ panics
+ Format: <bool> (1/Y/y=enable, 0/N/n=disable)
+ default: disabled
+
+ printk.devkmsg={on,off,ratelimit}
+ Control writing to /dev/kmsg.
+ on - unlimited logging to /dev/kmsg from userspace
+ off - logging to /dev/kmsg disabled
+ ratelimit - ratelimit the logging
+ Default: ratelimit
+
+ printk.time= Show timing data prefixed to each printk message line
+ Format: <bool> (1/Y/y=enable, 0/N/n=disable)
+
+ processor.max_cstate= [HW,ACPI]
+ Limit processor to maximum C-state
+ max_cstate=9 overrides any DMI blacklist limit.
+
+ processor.nocst [HW,ACPI]
+ Ignore the _CST method to determine C-states,
+ instead using the legacy FADT method
+
+ profile= [KNL] Enable kernel profiling via /proc/profile
+ Format: [schedule,]<number>
+ Param: "schedule" - profile schedule points.
+ Param: <number> - step/bucket size as a power of 2 for
+ statistical time based profiling.
+ Param: "sleep" - profile D-state sleeping (millisecs).
+ Requires CONFIG_SCHEDSTATS
+ Param: "kvm" - profile VM exits.
+
+ prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
+ before loading.
+ See Documentation/blockdev/ramdisk.txt.
+
+ psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
+ probe for; one of (bare|imps|exps|lifebook|any).
+ psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
+ per second.
+ psmouse.resetafter= [HW,MOUSE]
+ Try to reset the device after so many bad packets
+ (0 = never).
+ psmouse.resolution=
+ [HW,MOUSE] Set desired mouse resolution, in dpi.
+ psmouse.smartscroll=
+ [HW,MOUSE] Controls Logitech smartscroll autorepeat.
+ 0 = disabled, 1 = enabled (default).
+
+ pstore.backend= Specify the name of the pstore backend to use
+
+ pt. [PARIDE]
+ See Documentation/blockdev/paride.txt.
+
+ pty.legacy_count=
+ [KNL] Number of legacy pty's. Overwrites compiled-in
+ default number.
+
+ quiet [KNL] Disable most log messages
+
+ r128= [HW,DRM]
+
+ raid= [HW,RAID]
+ See Documentation/admin-guide/md.rst.
+
+ ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
+ See Documentation/blockdev/ramdisk.txt.
+
+ rcu_nocbs= [KNL]
+ The argument is a cpu list, as described above.
+
+ In kernels built with CONFIG_RCU_NOCB_CPU=y, set
+ the specified list of CPUs to be no-callback CPUs.
+ Invocation of these CPUs' RCU callbacks will
+ be offloaded to "rcuox/N" kthreads created for
+ that purpose, where "x" is "b" for RCU-bh, "p"
+ for RCU-preempt, and "s" for RCU-sched, and "N"
+ is the CPU number. This reduces OS jitter on the
+ offloaded CPUs, which can be useful for HPC and
+ real-time workloads. It can also improve energy
+ efficiency for asymmetric multiprocessors.
+
+ rcu_nocb_poll [KNL]
+ Rather than requiring that offloaded CPUs
+ (specified by rcu_nocbs= above) explicitly
+ awaken the corresponding "rcuoN" kthreads,
+ make these kthreads poll for callbacks.
+ This improves the real-time response for the
+ offloaded CPUs by relieving them of the need to
+ wake up the corresponding kthread, but degrades
+ energy efficiency by requiring that the kthreads
+ periodically wake up to do the polling.
+
+ rcutree.blimit= [KNL]
+ Set maximum number of finished RCU callbacks to
+ process in one batch.
+
+ rcutree.dump_tree= [KNL]
+ Dump the structure of the rcu_node combining tree
+ out at early boot. This is used for diagnostic
+ purposes, to verify correct tree setup.
+
+ rcutree.gp_cleanup_delay= [KNL]
+ Set the number of jiffies to delay each step of
+ RCU grace-period cleanup. This only has effect
+ when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
+
+ rcutree.gp_init_delay= [KNL]
+ Set the number of jiffies to delay each step of
+ RCU grace-period initialization. This only has
+ effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
+ is set.
+
+ rcutree.gp_preinit_delay= [KNL]
+ Set the number of jiffies to delay each step of
+ RCU grace-period pre-initialization, that is,
+ the propagation of recent CPU-hotplug changes up
+ the rcu_node combining tree. This only has effect
+ when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
+
+ rcutree.rcu_fanout_exact= [KNL]
+ Disable autobalancing of the rcu_node combining
+ tree. This is used by rcutorture, and might
+ possibly be useful for architectures having high
+ cache-to-cache transfer latencies.
+
+ rcutree.rcu_fanout_leaf= [KNL]
+ Change the number of CPUs assigned to each
+ leaf rcu_node structure. Useful for very
+ large systems, which will choose the value 64,
+ and for NUMA systems with large remote-access
+ latencies, which will choose a value aligned
+ with the appropriate hardware boundaries.
+
+ rcutree.jiffies_till_sched_qs= [KNL]
+ Set required age in jiffies for a
+ given grace period before RCU starts
+ soliciting quiescent-state help from
+ rcu_note_context_switch().
+
+ rcutree.jiffies_till_first_fqs= [KNL]
+ Set delay from grace-period initialization to
+ first attempt to force quiescent states.
+ Units are jiffies, minimum value is zero,
+ and maximum value is HZ.
+
+ rcutree.jiffies_till_next_fqs= [KNL]
+ Set delay between subsequent attempts to force
+ quiescent states. Units are jiffies, minimum
+ value is one, and maximum value is HZ.
+
+ rcutree.kthread_prio= [KNL,BOOT]
+ Set the SCHED_FIFO priority of the RCU per-CPU
+ kthreads (rcuc/N). This value is also used for
+ the priority of the RCU boost threads (rcub/N)
+ and for the RCU grace-period kthreads (rcu_bh,
+ rcu_preempt, and rcu_sched). If RCU_BOOST is
+ set, valid values are 1-99 and the default is 1
+ (the least-favored priority). Otherwise, when
+ RCU_BOOST is not set, valid values are 0-99 and
+ the default is zero (non-realtime operation).
+
+ rcutree.rcu_nocb_leader_stride= [KNL]
+ Set the number of NOCB kthread groups, which
+ defaults to the square root of the number of
+ CPUs. Larger numbers reduces the wakeup overhead
+ on the per-CPU grace-period kthreads, but increases
+ that same overhead on each group's leader.
+
+ rcutree.qhimark= [KNL]
+ Set threshold of queued RCU callbacks beyond which
+ batch limiting is disabled.
+
+ rcutree.qlowmark= [KNL]
+ Set threshold of queued RCU callbacks below which
+ batch limiting is re-enabled.
+
+ rcutree.rcu_idle_gp_delay= [KNL]
+ Set wakeup interval for idle CPUs that have
+ RCU callbacks (RCU_FAST_NO_HZ=y).
+
+ rcutree.rcu_idle_lazy_gp_delay= [KNL]
+ Set wakeup interval for idle CPUs that have
+ only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
+ Lazy RCU callbacks are those which RCU can
+ prove do nothing more than free memory.
+
+ rcuperf.gp_exp= [KNL]
+ Measure performance of expedited synchronous
+ grace-period primitives.
+
+ rcuperf.holdoff= [KNL]
+ Set test-start holdoff period. The purpose of
+ this parameter is to delay the start of the
+ test until boot completes in order to avoid
+ interference.
+
+ rcuperf.nreaders= [KNL]
+ Set number of RCU readers. The value -1 selects
+ N, where N is the number of CPUs. A value
+ "n" less than -1 selects N-n+1, where N is again
+ the number of CPUs. For example, -2 selects N
+ (the number of CPUs), -3 selects N+1, and so on.
+ A value of "n" less than or equal to -N selects
+ a single reader.
+
+ rcuperf.nwriters= [KNL]
+ Set number of RCU writers. The values operate
+ the same as for rcuperf.nreaders.
+ N, where N is the number of CPUs
+
+ rcuperf.perf_runnable= [BOOT]
+ Start rcuperf running at boot time.
+
+ rcuperf.shutdown= [KNL]
+ Shut the system down after performance tests
+ complete. This is useful for hands-off automated
+ testing.
+
+ rcuperf.perf_type= [KNL]
+ Specify the RCU implementation to test.
+
+ rcuperf.verbose= [KNL]
+ Enable additional printk() statements.
+
+ rcutorture.cbflood_inter_holdoff= [KNL]
+ Set holdoff time (jiffies) between successive
+ callback-flood tests.
+
+ rcutorture.cbflood_intra_holdoff= [KNL]
+ Set holdoff time (jiffies) between successive
+ bursts of callbacks within a given callback-flood
+ test.
+
+ rcutorture.cbflood_n_burst= [KNL]
+ Set the number of bursts making up a given
+ callback-flood test. Set this to zero to
+ disable callback-flood testing.
+
+ rcutorture.cbflood_n_per_burst= [KNL]
+ Set the number of callbacks to be registered
+ in a given burst of a callback-flood test.
+
+ rcutorture.fqs_duration= [KNL]
+ Set duration of force_quiescent_state bursts
+ in microseconds.
+
+ rcutorture.fqs_holdoff= [KNL]
+ Set holdoff time within force_quiescent_state bursts
+ in microseconds.
+
+ rcutorture.fqs_stutter= [KNL]
+ Set wait time between force_quiescent_state bursts
+ in seconds.
+
+ rcutorture.gp_cond= [KNL]
+ Use conditional/asynchronous update-side
+ primitives, if available.
+
+ rcutorture.gp_exp= [KNL]
+ Use expedited update-side primitives, if available.
+
+ rcutorture.gp_normal= [KNL]
+ Use normal (non-expedited) asynchronous
+ update-side primitives, if available.
+
+ rcutorture.gp_sync= [KNL]
+ Use normal (non-expedited) synchronous
+ update-side primitives, if available. If all
+ of rcutorture.gp_cond=, rcutorture.gp_exp=,
+ rcutorture.gp_normal=, and rcutorture.gp_sync=
+ are zero, rcutorture acts as if is interpreted
+ they are all non-zero.
+
+ rcutorture.n_barrier_cbs= [KNL]
+ Set callbacks/threads for rcu_barrier() testing.
+
+ rcutorture.nfakewriters= [KNL]
+ Set number of concurrent RCU writers. These just
+ stress RCU, they don't participate in the actual
+ test, hence the "fake".
+
+ rcutorture.nreaders= [KNL]
+ Set number of RCU readers. The value -1 selects
+ N-1, where N is the number of CPUs. A value
+ "n" less than -1 selects N-n-2, where N is again
+ the number of CPUs. For example, -2 selects N
+ (the number of CPUs), -3 selects N+1, and so on.
+
+ rcutorture.object_debug= [KNL]
+ Enable debug-object double-call_rcu() testing.
+
+ rcutorture.onoff_holdoff= [KNL]
+ Set time (s) after boot for CPU-hotplug testing.
+
+ rcutorture.onoff_interval= [KNL]
+ Set time (s) between CPU-hotplug operations, or
+ zero to disable CPU-hotplug testing.
+
+ rcutorture.shuffle_interval= [KNL]
+ Set task-shuffle interval (s). Shuffling tasks
+ allows some CPUs to go into dyntick-idle mode
+ during the rcutorture test.
+
+ rcutorture.shutdown_secs= [KNL]
+ Set time (s) after boot system shutdown. This
+ is useful for hands-off automated testing.
+
+ rcutorture.stall_cpu= [KNL]
+ Duration of CPU stall (s) to test RCU CPU stall
+ warnings, zero to disable.
+
+ rcutorture.stall_cpu_holdoff= [KNL]
+ Time to wait (s) after boot before inducing stall.
+
+ rcutorture.stat_interval= [KNL]
+ Time (s) between statistics printk()s.
+
+ rcutorture.stutter= [KNL]
+ Time (s) to stutter testing, for example, specifying
+ five seconds causes the test to run for five seconds,
+ wait for five seconds, and so on. This tests RCU's
+ ability to transition abruptly to and from idle.
+
+ rcutorture.test_boost= [KNL]
+ Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
+ "Maybe" means test if the RCU implementation
+ under test support RCU priority boosting.
+
+ rcutorture.test_boost_duration= [KNL]
+ Duration (s) of each individual boost test.
+
+ rcutorture.test_boost_interval= [KNL]
+ Interval (s) between each boost test.
+
+ rcutorture.test_no_idle_hz= [KNL]
+ Test RCU's dyntick-idle handling. See also the
+ rcutorture.shuffle_interval parameter.
+
+ rcutorture.torture_runnable= [BOOT]
+ Start rcutorture running at boot time.
+
+ rcutorture.torture_type= [KNL]
+ Specify the RCU implementation to test.
+
+ rcutorture.verbose= [KNL]
+ Enable additional printk() statements.
+
+ rcupdate.rcu_cpu_stall_suppress= [KNL]
+ Suppress RCU CPU stall warning messages.
+
+ rcupdate.rcu_cpu_stall_timeout= [KNL]
+ Set timeout for RCU CPU stall warning messages.
+
+ rcupdate.rcu_expedited= [KNL]
+ Use expedited grace-period primitives, for
+ example, synchronize_rcu_expedited() instead
+ of synchronize_rcu(). This reduces latency,
+ but can increase CPU utilization, degrade
+ real-time latency, and degrade energy efficiency.
+ No effect on CONFIG_TINY_RCU kernels.
+
+ rcupdate.rcu_normal= [KNL]
+ Use only normal grace-period primitives,
+ for example, synchronize_rcu() instead of
+ synchronize_rcu_expedited(). This improves
+ real-time latency, CPU utilization, and
+ energy efficiency, but can expose users to
+ increased grace-period latency. This parameter
+ overrides rcupdate.rcu_expedited. No effect on
+ CONFIG_TINY_RCU kernels.
+
+ rcupdate.rcu_normal_after_boot= [KNL]
+ Once boot has completed (that is, after
+ rcu_end_inkernel_boot() has been invoked), use
+ only normal grace-period primitives. No effect
+ on CONFIG_TINY_RCU kernels.
+
+ rcupdate.rcu_task_stall_timeout= [KNL]
+ Set timeout in jiffies for RCU task stall warning
+ messages. Disable with a value less than or equal
+ to zero.
+
+ rcupdate.rcu_self_test= [KNL]
+ Run the RCU early boot self tests
+
+ rcupdate.rcu_self_test_bh= [KNL]
+ Run the RCU bh early boot self tests
+
+ rcupdate.rcu_self_test_sched= [KNL]
+ Run the RCU sched early boot self tests
+
+ rdinit= [KNL]
+ Format: <full_path>
+ Run specified binary instead of /init from the ramdisk,
+ used for early userspace startup. See initrd.
+
+ reboot= [KNL]
+ Format (x86 or x86_64):
+ [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
+ [[,]s[mp]#### \
+ [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
+ [[,]f[orce]
+ Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
+ reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
+ reboot_force is either force or not specified,
+ reboot_cpu is s[mp]#### with #### being the processor
+ to be used for rebooting.
+
+ relax_domain_level=
+ [KNL, SMP] Set scheduler's default relax_domain_level.
+ See Documentation/cgroup-v1/cpusets.txt.
+
+ relative_sleep_states=
+ [SUSPEND] Use sleep state labeling where the deepest
+ state available other than hibernation is always "mem".
+ Format: { "0" | "1" }
+ 0 -- Traditional sleep state labels.
+ 1 -- Relative sleep state labels.
+
+ reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
+
+ reservetop= [X86-32]
+ Format: nn[KMG]
+ Reserves a hole at the top of the kernel virtual
+ address space.
+
+ reservelow= [X86]
+ Format: nn[K]
+ Set the amount of memory to reserve for BIOS at
+ the bottom of the address space.
+
+ reset_devices [KNL] Force drivers to reset the underlying device
+ during initialization.
+
+ resume= [SWSUSP]
+ Specify the partition device for software suspend
+ Format:
+ {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
+
+ resume_offset= [SWSUSP]
+ Specify the offset from the beginning of the partition
+ given by "resume=" at which the swap header is located,
+ in <PAGE_SIZE> units (needed only for swap files).
+ See Documentation/power/swsusp-and-swap-files.txt
+
+ resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
+ read the resume files
+
+ resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
+ Useful for devices that are detected asynchronously
+ (e.g. USB and MMC devices).
+
+ hibernate= [HIBERNATION]
+ noresume Don't check if there's a hibernation image
+ present during boot.
+ nocompress Don't compress/decompress hibernation images.
+ no Disable hibernation and resume.
+ protect_image Turn on image protection during restoration
+ (that will set all pages holding image data
+ during restoration read-only).
+
+ retain_initrd [RAM] Keep initrd memory after extraction
+
+ rfkill.default_state=
+ 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
+ etc. communication is blocked by default.
+ 1 Unblocked.
+
+ rfkill.master_switch_mode=
+ 0 The "airplane mode" button does nothing.
+ 1 The "airplane mode" button toggles between everything
+ blocked and the previous configuration.
+ 2 The "airplane mode" button toggles between everything
+ blocked and everything unblocked.
+
+ rhash_entries= [KNL,NET]
+ Set number of hash buckets for route cache
+
+ ro [KNL] Mount root device read-only on boot
+
+ rodata= [KNL]
+ on Mark read-only kernel memory as read-only (default).
+ off Leave read-only kernel memory writable for debugging.
+
+ rockchip.usb_uart
+ Enable the uart passthrough on the designated usb port
+ on Rockchip SoCs. When active, the signals of the
+ debug-uart get routed to the D+ and D- pins of the usb
+ port and the regular usb controller gets disabled.
+
+ root= [KNL] Root filesystem
+ See name_to_dev_t comment in init/do_mounts.c.
+
+ rootdelay= [KNL] Delay (in seconds) to pause before attempting to
+ mount the root filesystem
+
+ rootflags= [KNL] Set root filesystem mount option string
+
+ rootfstype= [KNL] Set root filesystem type
+
+ rootwait [KNL] Wait (indefinitely) for root device to show up.
+ Useful for devices that are detected asynchronously
+ (e.g. USB and MMC devices).
+
+ rproc_mem=nn[KMG][@address]
+ [KNL,ARM,CMA] Remoteproc physical memory block.
+ Memory area to be used by remote processor image,
+ managed by CMA.
+
+ rw [KNL] Mount root device read-write on boot
+
+ S [KNL] Run init in single mode
+
+ s390_iommu= [HW,S390]
+ Set s390 IOTLB flushing mode
+ strict
+ With strict flushing every unmap operation will result in
+ an IOTLB flush. Default is lazy flushing before reuse,
+ which is faster.
+
+ sa1100ir [NET]
+ See drivers/net/irda/sa1100_ir.c.
+
+ sbni= [NET] Granch SBNI12 leased line adapter
+
+ sched_debug [KNL] Enables verbose scheduler debug messages.
+
+ schedstats= [KNL,X86] Enable or disable scheduled statistics.
+ Allowed values are enable and disable. This feature
+ incurs a small amount of overhead in the scheduler
+ but is useful for debugging and performance tuning.
+
+ skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
+ xtime_lock contention on larger systems, and/or RCU lock
+ contention on all systems with CONFIG_MAXSMP set.
+ Format: { "0" | "1" }
+ 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
+ 1 -- enable.
+ Note: increases power consumption, thus should only be
+ enabled if running jitter sensitive (HPC/RT) workloads.
+
+ security= [SECURITY] Choose a security module to enable at boot.
+ If this boot parameter is not specified, only the first
+ security module asking for security registration will be
+ loaded. An invalid security module name will be treated
+ as if no module has been chosen.
+
+ selinux= [SELINUX] Disable or enable SELinux at boot time.
+ Format: { "0" | "1" }
+ See security/selinux/Kconfig help text.
+ 0 -- disable.
+ 1 -- enable.
+ Default value is set via kernel config option.
+ If enabled at boot time, /selinux/disable can be used
+ later to disable prior to initial policy load.
+
+ apparmor= [APPARMOR] Disable or enable AppArmor at boot time
+ Format: { "0" | "1" }
+ See security/apparmor/Kconfig help text
+ 0 -- disable.
+ 1 -- enable.
+ Default value is set via kernel config option.
+
+ serialnumber [BUGS=X86-32]
+
+ shapers= [NET]
+ Maximal number of shapers.
+
+ show_msr= [x86] show boot-time MSR settings
+ Format: { <integer> }
+ Show boot-time (BIOS-initialized) MSR settings.
+ The parameter means the number of CPUs to show,
+ for example 1 means boot CPU only.
+
+ simeth= [IA-64]
+ simscsi=
+
+ slram= [HW,MTD]
+
+ slab_nomerge [MM]
+ Disable merging of slabs with similar size. May be
+ necessary if there is some reason to distinguish
+ allocs to different slabs. Debug options disable
+ merging on their own.
+ For more information see Documentation/vm/slub.txt.
+
+ slab_max_order= [MM, SLAB]
+ Determines the maximum allowed order for slabs.
+ A high setting may cause OOMs due to memory
+ fragmentation. Defaults to 1 for systems with
+ more than 32MB of RAM, 0 otherwise.
+
+ slub_debug[=options[,slabs]] [MM, SLUB]
+ Enabling slub_debug allows one to determine the
+ culprit if slab objects become corrupted. Enabling
+ slub_debug can create guard zones around objects and
+ may poison objects when not in use. Also tracks the
+ last alloc / free. For more information see
+ Documentation/vm/slub.txt.
+
+ slub_max_order= [MM, SLUB]
+ Determines the maximum allowed order for slabs.
+ A high setting may cause OOMs due to memory
+ fragmentation. For more information see
+ Documentation/vm/slub.txt.
+
+ slub_min_objects= [MM, SLUB]
+ The minimum number of objects per slab. SLUB will
+ increase the slab order up to slub_max_order to
+ generate a sufficiently large slab able to contain
+ the number of objects indicated. The higher the number
+ of objects the smaller the overhead of tracking slabs
+ and the less frequently locks need to be acquired.
+ For more information see Documentation/vm/slub.txt.
+
+ slub_min_order= [MM, SLUB]
+ Determines the minimum page order for slabs. Must be
+ lower than slub_max_order.
+ For more information see Documentation/vm/slub.txt.
+
+ slub_nomerge [MM, SLUB]
+ Same with slab_nomerge. This is supported for legacy.
+ See slab_nomerge for more information.
+
+ smart2= [HW]
+ Format: <io1>[,<io2>[,...,<io8>]]
+
+ smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
+ smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
+ smsc-ircc2.ircc_sir= [HW] SIR base I/O port
+ smsc-ircc2.ircc_fir= [HW] FIR base I/O port
+ smsc-ircc2.ircc_irq= [HW] IRQ line
+ smsc-ircc2.ircc_dma= [HW] DMA channel
+ smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
+ 0: Toshiba Satellite 1800 (GP data pin select)
+ 1: Fast pin select (default)
+ 2: ATC IRMode
+
+ smt [KNL,S390] Set the maximum number of threads (logical
+ CPUs) to use per physical CPU on systems capable of
+ symmetric multithreading (SMT). Will be capped to the
+ actual hardware limit.
+ Format: <integer>
+ Default: -1 (no limit)
+
+ softlockup_panic=
+ [KNL] Should the soft-lockup detector generate panics.
+ Format: <integer>
+
+ softlockup_all_cpu_backtrace=
+ [KNL] Should the soft-lockup detector generate
+ backtraces on all cpus.
+ Format: <integer>
+
+ sonypi.*= [HW] Sony Programmable I/O Control Device driver
+ See Documentation/laptops/sonypi.txt
+
+ spia_io_base= [HW,MTD]
+ spia_fio_base=
+ spia_pedr=
+ spia_peddr=
+
+ stacktrace [FTRACE]
+ Enabled the stack tracer on boot up.
+
+ stacktrace_filter=[function-list]
+ [FTRACE] Limit the functions that the stack tracer
+ will trace at boot up. function-list is a comma separated
+ list of functions. This list can be changed at run
+ time by the stack_trace_filter file in the debugfs
+ tracing directory. Note, this enables stack tracing
+ and the stacktrace above is not needed.
+
+ sti= [PARISC,HW]
+ Format: <num>
+ Set the STI (builtin display/keyboard on the HP-PARISC
+ machines) console (graphic card) which should be used
+ as the initial boot-console.
+ See also comment in drivers/video/console/sticore.c.
+
+ sti_font= [HW]
+ See comment in drivers/video/console/sticore.c.
+
+ stifb= [HW]
+ Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
+
+ sunrpc.min_resvport=
+ sunrpc.max_resvport=
+ [NFS,SUNRPC]
+ SunRPC servers often require that client requests
+ originate from a privileged port (i.e. a port in the
+ range 0 < portnr < 1024).
+ An administrator who wishes to reserve some of these
+ ports for other uses may adjust the range that the
+ kernel's sunrpc client considers to be privileged
+ using these two parameters to set the minimum and
+ maximum port values.
+
+ sunrpc.svc_rpc_per_connection_limit=
+ [NFS,SUNRPC]
+ Limit the number of requests that the server will
+ process in parallel from a single connection.
+ The default value is 0 (no limit).
+
+ sunrpc.pool_mode=
+ [NFS]
+ Control how the NFS server code allocates CPUs to
+ service thread pools. Depending on how many NICs
+ you have and where their interrupts are bound, this
+ option will affect which CPUs will do NFS serving.
+ Note: this parameter cannot be changed while the
+ NFS server is running.
+
+ auto the server chooses an appropriate mode
+ automatically using heuristics
+ global a single global pool contains all CPUs
+ percpu one pool for each CPU
+ pernode one pool for each NUMA node (equivalent
+ to global on non-NUMA machines)
+
+ sunrpc.tcp_slot_table_entries=
+ sunrpc.udp_slot_table_entries=
+ [NFS,SUNRPC]
+ Sets the upper limit on the number of simultaneous
+ RPC calls that can be sent from the client to a
+ server. Increasing these values may allow you to
+ improve throughput, but will also increase the
+ amount of memory reserved for use by the client.
+
+ suspend.pm_test_delay=
+ [SUSPEND]
+ Sets the number of seconds to remain in a suspend test
+ mode before resuming the system (see
+ /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
+ is set. Default value is 5.
+
+ swapaccount=[0|1]
+ [KNL] Enable accounting of swap in memory resource
+ controller if no parameter or 1 is given or disable
+ it if 0 is given (See Documentation/cgroup-v1/memory.txt)
+
+ swiotlb= [ARM,IA-64,PPC,MIPS,X86]
+ Format: { <int> | force }
+ <int> -- Number of I/O TLB slabs
+ force -- force using of bounce buffers even if they
+ wouldn't be automatically used by the kernel
+
+ switches= [HW,M68k]
+
+ sysfs.deprecated=0|1 [KNL]
+ Enable/disable old style sysfs layout for old udev
+ on older distributions. When this option is enabled
+ very new udev will not work anymore. When this option
+ is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
+ in older udev will not work anymore.
+ Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
+ the kernel configuration.
+
+ sysrq_always_enabled
+ [KNL]
+ Ignore sysrq setting - this boot parameter will
+ neutralize any effect of /proc/sys/kernel/sysrq.
+ Useful for debugging.
+
+ tcpmhash_entries= [KNL,NET]
+ Set the number of tcp_metrics_hash slots.
+ Default value is 8192 or 16384 depending on total
+ ram pages. This is used to specify the TCP metrics
+ cache size. See Documentation/networking/ip-sysctl.txt
+ "tcp_no_metrics_save" section for more details.
+
+ tdfx= [HW,DRM]
+
+ test_suspend= [SUSPEND][,N]
+ Specify "mem" (for Suspend-to-RAM) or "standby" (for
+ standby suspend) or "freeze" (for suspend type freeze)
+ as the system sleep state during system startup with
+ the optional capability to repeat N number of times.
+ The system is woken from this state using a
+ wakeup-capable RTC alarm.
+
+ thash_entries= [KNL,NET]
+ Set number of hash buckets for TCP connection
+
+ thermal.act= [HW,ACPI]
+ -1: disable all active trip points in all thermal zones
+ <degrees C>: override all lowest active trip points
+
+ thermal.crt= [HW,ACPI]
+ -1: disable all critical trip points in all thermal zones
+ <degrees C>: override all critical trip points
+
+ thermal.nocrt= [HW,ACPI]
+ Set to disable actions on ACPI thermal zone
+ critical and hot trip points.
+
+ thermal.off= [HW,ACPI]
+ 1: disable ACPI thermal control
+
+ thermal.psv= [HW,ACPI]
+ -1: disable all passive trip points
+ <degrees C>: override all passive trip points to this
+ value
+
+ thermal.tzp= [HW,ACPI]
+ Specify global default ACPI thermal zone polling rate
+ <deci-seconds>: poll all this frequency
+ 0: no polling (default)
+
+ threadirqs [KNL]
+ Force threading of all interrupt handlers except those
+ marked explicitly IRQF_NO_THREAD.
+
+ tmem [KNL,XEN]
+ Enable the Transcendent memory driver if built-in.
+
+ tmem.cleancache=0|1 [KNL, XEN]
+ Default is on (1). Disable the usage of the cleancache
+ API to send anonymous pages to the hypervisor.
+
+ tmem.frontswap=0|1 [KNL, XEN]
+ Default is on (1). Disable the usage of the frontswap
+ API to send swap pages to the hypervisor. If disabled
+ the selfballooning and selfshrinking are force disabled.
+
+ tmem.selfballooning=0|1 [KNL, XEN]
+ Default is on (1). Disable the driving of swap pages
+ to the hypervisor.
+
+ tmem.selfshrinking=0|1 [KNL, XEN]
+ Default is on (1). Partial swapoff that immediately
+ transfers pages from Xen hypervisor back to the
+ kernel based on different criteria.
+
+ topology= [S390]
+ Format: {off | on}
+ Specify if the kernel should make use of the cpu
+ topology information if the hardware supports this.
+ The scheduler will make use of this information and
+ e.g. base its process migration decisions on it.
+ Default is on.
+
+ topology_updates= [KNL, PPC, NUMA]
+ Format: {off}
+ Specify if the kernel should ignore (off)
+ topology updates sent by the hypervisor to this
+ LPAR.
+
+ tp720= [HW,PS2]
+
+ tpm_suspend_pcr=[HW,TPM]
+ Format: integer pcr id
+ Specify that at suspend time, the tpm driver
+ should extend the specified pcr with zeros,
+ as a workaround for some chips which fail to
+ flush the last written pcr on TPM_SaveState.
+ This will guarantee that all the other pcrs
+ are saved.
+
+ trace_buf_size=nn[KMG]
+ [FTRACE] will set tracing buffer size on each cpu.
+
+ trace_event=[event-list]
+ [FTRACE] Set and start specified trace events in order
+ to facilitate early boot debugging. The event-list is a
+ comma separated list of trace events to enable. See
+ also Documentation/trace/events.txt
+
+ trace_options=[option-list]
+ [FTRACE] Enable or disable tracer options at boot.
+ The option-list is a comma delimited list of options
+ that can be enabled or disabled just as if you were
+ to echo the option name into
+
+ /sys/kernel/debug/tracing/trace_options
+
+ For example, to enable stacktrace option (to dump the
+ stack trace of each event), add to the command line:
+
+ trace_options=stacktrace
+
+ See also Documentation/trace/ftrace.txt "trace options"
+ section.
+
+ tp_printk[FTRACE]
+ Have the tracepoints sent to printk as well as the
+ tracing ring buffer. This is useful for early boot up
+ where the system hangs or reboots and does not give the
+ option for reading the tracing buffer or performing a
+ ftrace_dump_on_oops.
+
+ To turn off having tracepoints sent to printk,
+ echo 0 > /proc/sys/kernel/tracepoint_printk
+ Note, echoing 1 into this file without the
+ tracepoint_printk kernel cmdline option has no effect.
+
+ ** CAUTION **
+
+ Having tracepoints sent to printk() and activating high
+ frequency tracepoints such as irq or sched, can cause
+ the system to live lock.
+
+ traceoff_on_warning
+ [FTRACE] enable this option to disable tracing when a
+ warning is hit. This turns off "tracing_on". Tracing can
+ be enabled again by echoing '1' into the "tracing_on"
+ file located in /sys/kernel/debug/tracing/
+
+ This option is useful, as it disables the trace before
+ the WARNING dump is called, which prevents the trace to
+ be filled with content caused by the warning output.
+
+ This option can also be set at run time via the sysctl
+ option: kernel/traceoff_on_warning
+
+ transparent_hugepage=
+ [KNL]
+ Format: [always|madvise|never]
+ Can be used to control the default behavior of the system
+ with respect to transparent hugepages.
+ See Documentation/vm/transhuge.txt for more details.
+
+ tsc= Disable clocksource stability checks for TSC.
+ Format: <string>
+ [x86] reliable: mark tsc clocksource as reliable, this
+ disables clocksource verification at runtime, as well
+ as the stability checks done at bootup. Used to enable
+ high-resolution timer mode on older hardware, and in
+ virtualized environment.
+ [x86] noirqtime: Do not use TSC to do irq accounting.
+ Used to run time disable IRQ_TIME_ACCOUNTING on any
+ platforms where RDTSC is slow and this accounting
+ can add overhead.
+
+ turbografx.map[2|3]= [HW,JOY]
+ TurboGraFX parallel port interface
+ Format:
+ <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
+ See also Documentation/input/joystick-parport.txt
+
+ udbg-immortal [PPC] When debugging early kernel crashes that
+ happen after console_init() and before a proper
+ console driver takes over, this boot options might
+ help "seeing" what's going on.
+
+ uhash_entries= [KNL,NET]
+ Set number of hash buckets for UDP/UDP-Lite connections
+
+ uhci-hcd.ignore_oc=
+ [USB] Ignore overcurrent events (default N).
+ Some badly-designed motherboards generate lots of
+ bogus events, for ports that aren't wired to
+ anything. Set this parameter to avoid log spamming.
+ Note that genuine overcurrent events won't be
+ reported either.
+
+ unknown_nmi_panic
+ [X86] Cause panic on unknown NMI.
+
+ usbcore.authorized_default=
+ [USB] Default USB device authorization:
+ (default -1 = authorized except for wireless USB,
+ 0 = not authorized, 1 = authorized)
+
+ usbcore.autosuspend=
+ [USB] The autosuspend time delay (in seconds) used
+ for newly-detected USB devices (default 2). This
+ is the time required before an idle device will be
+ autosuspended. Devices for which the delay is set
+ to a negative value won't be autosuspended at all.
+
+ usbcore.usbfs_snoop=
+ [USB] Set to log all usbfs traffic (default 0 = off).
+
+ usbcore.usbfs_snoop_max=
+ [USB] Maximum number of bytes to snoop in each URB
+ (default = 65536).
+
+ usbcore.blinkenlights=
+ [USB] Set to cycle leds on hubs (default 0 = off).
+
+ usbcore.old_scheme_first=
+ [USB] Start with the old device initialization
+ scheme (default 0 = off).
+
+ usbcore.usbfs_memory_mb=
+ [USB] Memory limit (in MB) for buffers allocated by
+ usbfs (default = 16, 0 = max = 2047).
+
+ usbcore.use_both_schemes=
+ [USB] Try the other device initialization scheme
+ if the first one fails (default 1 = enabled).
+
+ usbcore.initial_descriptor_timeout=
+ [USB] Specifies timeout for the initial 64-byte
+ USB_REQ_GET_DESCRIPTOR request in milliseconds
+ (default 5000 = 5.0 seconds).
+
+ usbcore.nousb [USB] Disable the USB subsystem
+
+ usbhid.mousepoll=
+ [USBHID] The interval which mice are to be polled at.
+
+ usb-storage.delay_use=
+ [UMS] The delay in seconds before a new device is
+ scanned for Logical Units (default 1).
+
+ usb-storage.quirks=
+ [UMS] A list of quirks entries to supplement or
+ override the built-in unusual_devs list. List
+ entries are separated by commas. Each entry has
+ the form VID:PID:Flags where VID and PID are Vendor
+ and Product ID values (4-digit hex numbers) and
+ Flags is a set of characters, each corresponding
+ to a common usb-storage quirk flag as follows:
+ a = SANE_SENSE (collect more than 18 bytes
+ of sense data);
+ b = BAD_SENSE (don't collect more than 18
+ bytes of sense data);
+ c = FIX_CAPACITY (decrease the reported
+ device capacity by one sector);
+ d = NO_READ_DISC_INFO (don't use
+ READ_DISC_INFO command);
+ e = NO_READ_CAPACITY_16 (don't use
+ READ_CAPACITY_16 command);
+ f = NO_REPORT_OPCODES (don't use report opcodes
+ command, uas only);
+ g = MAX_SECTORS_240 (don't transfer more than
+ 240 sectors at a time, uas only);
+ h = CAPACITY_HEURISTICS (decrease the
+ reported device capacity by one
+ sector if the number is odd);
+ i = IGNORE_DEVICE (don't bind to this
+ device);
+ j = NO_REPORT_LUNS (don't use report luns
+ command, uas only);
+ l = NOT_LOCKABLE (don't try to lock and
+ unlock ejectable media);
+ m = MAX_SECTORS_64 (don't transfer more
+ than 64 sectors = 32 KB at a time);
+ n = INITIAL_READ10 (force a retry of the
+ initial READ(10) command);
+ o = CAPACITY_OK (accept the capacity
+ reported by the device);
+ p = WRITE_CACHE (the device cache is ON
+ by default);
+ r = IGNORE_RESIDUE (the device reports
+ bogus residue values);
+ s = SINGLE_LUN (the device has only one
+ Logical Unit);
+ t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
+ commands, uas only);
+ u = IGNORE_UAS (don't bind to the uas driver);
+ w = NO_WP_DETECT (don't test whether the
+ medium is write-protected).
+ y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
+ even if the device claims no cache)
+ Example: quirks=0419:aaf5:rl,0421:0433:rc
+
+ user_debug= [KNL,ARM]
+ Format: <int>
+ See arch/arm/Kconfig.debug help text.
+ 1 - undefined instruction events
+ 2 - system calls
+ 4 - invalid data aborts
+ 8 - SIGSEGV faults
+ 16 - SIGBUS faults
+ Example: user_debug=31
+
+ userpte=
+ [X86] Flags controlling user PTE allocations.
+
+ nohigh = do not allocate PTE pages in
+ HIGHMEM regardless of setting
+ of CONFIG_HIGHPTE.
+
+ vdso= [X86,SH]
+ On X86_32, this is an alias for vdso32=. Otherwise:
+
+ vdso=1: enable VDSO (the default)
+ vdso=0: disable VDSO mapping
+
+ vdso32= [X86] Control the 32-bit vDSO
+ vdso32=1: enable 32-bit VDSO
+ vdso32=0 or vdso32=2: disable 32-bit VDSO
+
+ See the help text for CONFIG_COMPAT_VDSO for more
+ details. If CONFIG_COMPAT_VDSO is set, the default is
+ vdso32=0; otherwise, the default is vdso32=1.
+
+ For compatibility with older kernels, vdso32=2 is an
+ alias for vdso32=0.
+
+ Try vdso32=0 if you encounter an error that says:
+ dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
+
+ vector= [IA-64,SMP]
+ vector=percpu: enable percpu vector domain
+
+ video= [FB] Frame buffer configuration
+ See Documentation/fb/modedb.txt.
+
+ video.brightness_switch_enabled= [0,1]
+ If set to 1, on receiving an ACPI notify event
+ generated by hotkey, video driver will adjust brightness
+ level and then send out the event to user space through
+ the allocated input device; If set to 0, video driver
+ will only send out the event without touching backlight
+ brightness level.
+ default: 1
+
+ virtio_mmio.device=
+ [VMMIO] Memory mapped virtio (platform) device.
+
+ <size>@<baseaddr>:<irq>[:<id>]
+ where:
+ <size> := size (can use standard suffixes
+ like K, M and G)
+ <baseaddr> := physical base address
+ <irq> := interrupt number (as passed to
+ request_irq())
+ <id> := (optional) platform device id
+ example:
+ virtio_mmio.device=1K@0x100b0000:48:7
+
+ Can be used multiple times for multiple devices.
+
+ vga= [BOOT,X86-32] Select a particular video mode
+ See Documentation/x86/boot.txt and
+ Documentation/svga.txt.
+ Use vga=ask for menu.
+ This is actually a boot loader parameter; the value is
+ passed to the kernel using a special protocol.
+
+ vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
+ size of <nn>. This can be used to increase the
+ minimum size (128MB on x86). It can also be used to
+ decrease the size and leave more room for directly
+ mapped kernel RAM.
+
+ vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
+ Format: <command>
+
+ vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
+ Format: <command>
+
+ vmpoff= [KNL,S390] Perform z/VM CP command after power off.
+ Format: <command>
+
+ vsyscall= [X86-64]
+ Controls the behavior of vsyscalls (i.e. calls to
+ fixed addresses of 0xffffffffff600x00 from legacy
+ code). Most statically-linked binaries and older
+ versions of glibc use these calls. Because these
+ functions are at fixed addresses, they make nice
+ targets for exploits that can control RIP.
+
+ emulate [default] Vsyscalls turn into traps and are
+ emulated reasonably safely.
+
+ native Vsyscalls are native syscall instructions.
+ This is a little bit faster than trapping
+ and makes a few dynamic recompilers work
+ better than they would in emulation mode.
+ It also makes exploits much easier to write.
+
+ none Vsyscalls don't work at all. This makes
+ them quite hard to use for exploits but
+ might break your system.
+
+ vt.color= [VT] Default text color.
+ Format: 0xYX, X = foreground, Y = background.
+ Default: 0x07 = light gray on black.
+
+ vt.cur_default= [VT] Default cursor shape.
+ Format: 0xCCBBAA, where AA, BB, and CC are the same as
+ the parameters of the <Esc>[?A;B;Cc escape sequence;
+ see VGA-softcursor.txt. Default: 2 = underline.
+
+ vt.default_blu= [VT]
+ Format: <blue0>,<blue1>,<blue2>,...,<blue15>
+ Change the default blue palette of the console.
+ This is a 16-member array composed of values
+ ranging from 0-255.
+
+ vt.default_grn= [VT]
+ Format: <green0>,<green1>,<green2>,...,<green15>
+ Change the default green palette of the console.
+ This is a 16-member array composed of values
+ ranging from 0-255.
+
+ vt.default_red= [VT]
+ Format: <red0>,<red1>,<red2>,...,<red15>
+ Change the default red palette of the console.
+ This is a 16-member array composed of values
+ ranging from 0-255.
+
+ vt.default_utf8=
+ [VT]
+ Format=<0|1>
+ Set system-wide default UTF-8 mode for all tty's.
+ Default is 1, i.e. UTF-8 mode is enabled for all
+ newly opened terminals.
+
+ vt.global_cursor_default=
+ [VT]
+ Format=<-1|0|1>
+ Set system-wide default for whether a cursor
+ is shown on new VTs. Default is -1,
+ i.e. cursors will be created by default unless
+ overridden by individual drivers. 0 will hide
+ cursors, 1 will display them.
+
+ vt.italic= [VT] Default color for italic text; 0-15.
+ Default: 2 = green.
+
+ vt.underline= [VT] Default color for underlined text; 0-15.
+ Default: 3 = cyan.
+
+ watchdog timers [HW,WDT] For information on watchdog timers,
+ see Documentation/watchdog/watchdog-parameters.txt
+ or other driver-specific files in the
+ Documentation/watchdog/ directory.
+
+ workqueue.watchdog_thresh=
+ If CONFIG_WQ_WATCHDOG is configured, workqueue can
+ warn stall conditions and dump internal state to
+ help debugging. 0 disables workqueue stall
+ detection; otherwise, it's the stall threshold
+ duration in seconds. The default value is 30 and
+ it can be updated at runtime by writing to the
+ corresponding sysfs file.
+
+ workqueue.disable_numa
+ By default, all work items queued to unbound
+ workqueues are affine to the NUMA nodes they're
+ issued on, which results in better behavior in
+ general. If NUMA affinity needs to be disabled for
+ whatever reason, this option can be used. Note
+ that this also can be controlled per-workqueue for
+ workqueues visible under /sys/bus/workqueue/.
+
+ workqueue.power_efficient
+ Per-cpu workqueues are generally preferred because
+ they show better performance thanks to cache
+ locality; unfortunately, per-cpu workqueues tend to
+ be more power hungry than unbound workqueues.
+
+ Enabling this makes the per-cpu workqueues which
+ were observed to contribute significantly to power
+ consumption unbound, leading to measurably lower
+ power usage at the cost of small performance
+ overhead.
+
+ The default value of this parameter is determined by
+ the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
+
+ workqueue.debug_force_rr_cpu
+ Workqueue used to implicitly guarantee that work
+ items queued without explicit CPU specified are put
+ on the local CPU. This guarantee is no longer true
+ and while local CPU is still preferred work items
+ may be put on foreign CPUs. This debug option
+ forces round-robin CPU selection to flush out
+ usages which depend on the now broken guarantee.
+ When enabled, memory and cache locality will be
+ impacted.
+
+ x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
+ default x2apic cluster mode on platforms
+ supporting x2apic.
+
+ x86_intel_mid_timer= [X86-32,APBT]
+ Choose timer option for x86 Intel MID platform.
+ Two valid options are apbt timer only and lapic timer
+ plus one apbt timer for broadcast timer.
+ x86_intel_mid_timer=apbt_only | lapic_and_apbt
+
+ xen_512gb_limit [KNL,X86-64,XEN]
+ Restricts the kernel running paravirtualized under Xen
+ to use only up to 512 GB of RAM. The reason to do so is
+ crash analysis tools and Xen tools for doing domain
+ save/restore/migration must be enabled to handle larger
+ domains.
+
+ xen_emul_unplug= [HW,X86,XEN]
+ Unplug Xen emulated devices
+ Format: [unplug0,][unplug1]
+ ide-disks -- unplug primary master IDE devices
+ aux-ide-disks -- unplug non-primary-master IDE devices
+ nics -- unplug network devices
+ all -- unplug all emulated devices (NICs and IDE disks)
+ unnecessary -- unplugging emulated devices is
+ unnecessary even if the host did not respond to
+ the unplug protocol
+ never -- do not unplug even if version check succeeds
+
+ xen_nopvspin [X86,XEN]
+ Disables the ticketlock slowpath using Xen PV
+ optimizations.
+
+ xen_nopv [X86]
+ Disables the PV optimizations forcing the HVM guest to
+ run as generic HVM guest with no PV drivers.
+
+ xirc2ps_cs= [NET,PCMCIA]
+ Format:
+ <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
projects / linux-2.6-block.git / commitdiff