4 The following is a consolidated list of the kernel parameters as
5 implemented by the __setup(), core_param() and module_param() macros
6 and sorted into English Dictionary order (defined as ignoring all
7 punctuation and sorting digits before letters in a case insensitive
8 manner), and with descriptions where known.
10 The kernel parses parameters from the kernel command line up to "--";
11 if it doesn't recognize a parameter and it doesn't contain a '.', the
12 parameter gets passed to init: parameters with '=' go into init's
13 environment, others are passed as command line arguments to init.
14 Everything after "--" is passed as an argument to init.
16 Module parameters can be specified in two ways: via the kernel command
17 line with a module name prefix, or via modprobe, e.g.:
19 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
22 Parameters for modules which are built into the kernel need to be
23 specified on the kernel command line. modprobe looks through the
24 kernel command line (/proc/cmdline) and collects module parameters
25 when it loads a module, so the kernel command line can be used for
28 Hyphens (dashes) and underscores are equivalent in parameter names, so
29 log_buf_len=1M print-fatal-signals=1
30 can also be entered as
31 log-buf-len=1M print_fatal_signals=1
33 Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
36 This document may not be entirely up to date and comprehensive. The command
37 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38 module. Loadable modules, after being loaded into the running kernel, also
39 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40 parameters may be changed at runtime by the command
41 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
43 The parameters listed below are only valid if certain kernel build options were
44 enabled and if respective hardware is present. The text in square brackets at
45 the beginning of each description states the restrictions within which a
46 parameter is applicable:
48 ACPI ACPI support is enabled.
49 AGP AGP (Accelerated Graphics Port) is enabled.
50 ALSA ALSA sound support is enabled.
51 APIC APIC support is enabled.
52 APM Advanced Power Management support is enabled.
53 ARM ARM architecture is enabled.
54 AVR32 AVR32 architecture is enabled.
55 AX25 Appropriate AX.25 support is enabled.
56 BLACKFIN Blackfin architecture is enabled.
57 CLK Common clock infrastructure is enabled.
58 CMA Contiguous Memory Area support is enabled.
59 DRM Direct Rendering Management support is enabled.
60 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
61 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
62 EFI EFI Partitioning (GPT) is enabled
63 EIDE EIDE/ATAPI support is enabled.
64 EVM Extended Verification Module
65 FB The frame buffer device is enabled.
66 FTRACE Function tracing enabled.
67 GCOV GCOV profiling is enabled.
68 HW Appropriate hardware is enabled.
69 IA-64 IA-64 architecture is enabled.
70 IMA Integrity measurement architecture is enabled.
71 IOSCHED More than one I/O scheduler is enabled.
72 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
73 IPV6 IPv6 support is enabled.
74 ISAPNP ISA PnP code is enabled.
75 ISDN Appropriate ISDN support is enabled.
76 JOY Appropriate joystick support is enabled.
77 KGDB Kernel debugger support is enabled.
78 KVM Kernel Virtual Machine support is enabled.
79 LIBATA Libata driver is enabled
80 LP Printer support is enabled.
81 LOOP Loopback device support is enabled.
82 M68k M68k architecture is enabled.
83 These options have more detailed description inside of
84 Documentation/m68k/kernel-options.txt.
85 MDA MDA console support is enabled.
86 MIPS MIPS architecture is enabled.
87 MOUSE Appropriate mouse support is enabled.
88 MSI Message Signaled Interrupts (PCI).
89 MTD MTD (Memory Technology Device) support is enabled.
90 NET Appropriate network support is enabled.
91 NUMA NUMA support is enabled.
92 NFS Appropriate NFS support is enabled.
93 OSS OSS sound support is enabled.
94 PV_OPS A paravirtualized kernel is enabled.
95 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
96 PARISC The PA-RISC architecture is enabled.
97 PCI PCI bus support is enabled.
98 PCIE PCI Express support is enabled.
99 PCMCIA The PCMCIA subsystem is enabled.
100 PNP Plug & Play support is enabled.
101 PPC PowerPC architecture is enabled.
102 PPT Parallel port support is enabled.
103 PS2 Appropriate PS/2 support is enabled.
104 RAM RAM disk support is enabled.
105 S390 S390 architecture is enabled.
106 SCSI Appropriate SCSI support is enabled.
107 A lot of drivers have their options described inside
108 the Documentation/scsi/ sub-directory.
109 SECURITY Different security models are enabled.
110 SELINUX SELinux support is enabled.
111 APPARMOR AppArmor support is enabled.
112 SERIAL Serial support is enabled.
113 SH SuperH architecture is enabled.
114 SMP The kernel is an SMP kernel.
115 SPARC Sparc architecture is enabled.
116 SWSUSP Software suspend (hibernation) is enabled.
117 SUSPEND System suspend states are enabled.
118 TPM TPM drivers are enabled.
119 TS Appropriate touchscreen support is enabled.
120 UMS USB Mass Storage support is enabled.
121 USB USB support is enabled.
122 USBHID USB Human Interface Device support is enabled.
123 V4L Video For Linux support is enabled.
124 VMMIO Driver for memory mapped virtio devices is enabled.
125 VGA The VGA console has been enabled.
126 VT Virtual terminal support is enabled.
127 WDT Watchdog support is enabled.
128 XT IBM PC/XT MFM hard disk support is enabled.
129 X86-32 X86-32, aka i386 architecture is enabled.
130 X86-64 X86-64 architecture is enabled.
131 More X86-64 boot options can be found in
132 Documentation/x86/x86_64/boot-options.txt .
133 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
134 XEN Xen support is enabled
136 In addition, the following text indicates that the option:
138 BUGS= Relates to possible processor bugs on the said processor.
139 KNL Is a kernel start-up parameter.
140 BOOT Is a boot loader parameter.
142 Parameters denoted with BOOT are actually interpreted by the boot
143 loader, and have no meaning to the kernel directly.
144 Do not modify the syntax of boot loader parameters without extreme
145 need or coordination with <Documentation/x86/boot.txt>.
147 There are also arch-specific kernel-parameters not documented here.
148 See for example <Documentation/x86/x86_64/boot-options.txt>.
150 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151 a trailing = on the name of any parameter states that that parameter will
152 be entered as an environment variable, whereas its absence indicates that
153 it will appear as a kernel argument readable via /proc/cmdline by programs
154 running once the system is up.
156 The number of kernel parameters is not limited, but the length of the
157 complete command line (parameters including spaces etc.) is limited to
158 a fixed number of characters. This limit depends on the architecture
159 and is between 256 and 4096 characters. It is defined in the file
160 ./include/asm/setup.h as COMMAND_LINE_SIZE.
162 Finally, the [KMG] suffix is commonly described after a number of kernel
163 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165 bytes respectively. Such letter suffixes can also be entirely omitted.
168 acpi= [HW,ACPI,X86,ARM64]
169 Advanced Configuration and Power Interface
170 Format: { force | off | strict | noirq | rsdt }
171 force -- enable ACPI if default was off
172 off -- disable ACPI if default was on
173 noirq -- do not use ACPI for IRQ routing
174 strict -- Be less tolerant of platforms that are not
175 strictly ACPI specification compliant.
176 rsdt -- prefer RSDT over (default) XSDT
177 copy_dsdt -- copy DSDT to memory
178 For ARM64, ONLY "acpi=off" or "acpi=force" are available
180 See also Documentation/power/runtime_pm.txt, pci=noacpi
182 acpi_apic_instance= [ACPI, IOAPIC]
184 2: use 2nd APIC table, if available
185 1,0: use 1st APIC table
188 acpi_backlight= [HW,ACPI]
189 acpi_backlight=vendor
191 If set to vendor, prefer vendor specific driver
192 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
193 of the ACPI video.ko driver.
195 acpica_no_return_repair [HW, ACPI]
196 Disable AML predefined validation mechanism
197 This mechanism can repair the evaluation result to make
198 the return objects more ACPI specification compliant.
199 This option is useful for developers to identify the
200 root cause of an AML interpreter issue when the issue
201 has something to do with the repair mechanism.
203 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
204 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
206 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
207 debug output. Bits in debug_layer correspond to a
208 _COMPONENT in an ACPI source file, e.g.,
209 #define _COMPONENT ACPI_PCI_COMPONENT
210 Bits in debug_level correspond to a level in
211 ACPI_DEBUG_PRINT statements, e.g.,
212 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
213 The debug_level mask defaults to "info". See
214 Documentation/acpi/debug.txt for more information about
215 debug layers and levels.
217 Enable processor driver info messages:
218 acpi.debug_layer=0x20000000
219 Enable PCI/PCI interrupt routing info messages:
220 acpi.debug_layer=0x400000
221 Enable AML "Debug" output, i.e., stores to the Debug
222 object while interpreting AML:
223 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
224 Enable all messages related to ACPI hardware:
225 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
227 Some values produce so much output that the system is
228 unusable. The "log_buf_len" parameter may be useful
229 if you need to capture more output.
231 acpi_enforce_resources= [ACPI]
232 { strict | lax | no }
233 Check for resource conflicts between native drivers
234 and ACPI OperationRegions (SystemIO and SystemMemory
235 only). IO ports and memory declared in ACPI might be
236 used by the ACPI subsystem in arbitrary AML code and
237 can interfere with legacy drivers.
238 strict (default): access to resources claimed by ACPI
239 is denied; legacy drivers trying to access reserved
240 resources will fail to bind to device using them.
241 lax: access to resources claimed by ACPI is allowed;
242 legacy drivers trying to access reserved resources
243 will bind successfully but a warning message is logged.
244 no: ACPI OperationRegions are not marked as reserved,
245 no further checks are performed.
247 acpi_force_table_verification [HW,ACPI]
248 Enable table checksum verification during early stage.
249 By default, this is disabled due to x86 early mapping
252 acpi_irq_balance [HW,ACPI]
253 ACPI will balance active IRQs
256 acpi_irq_nobalance [HW,ACPI]
257 ACPI will not move active IRQs (default)
260 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
261 Format: <irq>,<irq>...
263 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
265 Format: <irq>,<irq>...
267 acpi_no_auto_serialize [HW,ACPI]
268 Disable auto-serialization of AML methods
269 AML control methods that contain the opcodes to create
270 named objects will be marked as "Serialized" by the
271 auto-serialization feature.
272 This feature is enabled by default.
273 This option allows to turn off the feature.
275 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
278 acpi_no_static_ssdt [HW,ACPI]
279 Disable installation of static SSDTs at early boot time
280 By default, SSDTs contained in the RSDT/XSDT will be
281 installed automatically and they will appear under
282 /sys/firmware/acpi/tables.
283 This option turns off this feature.
284 Note that specifying this option does not affect
285 dynamic table installation which will install SSDT
286 tables to /sys/firmware/acpi/tables/dynamic.
288 acpi_rsdp= [ACPI,EFI,KEXEC]
289 Pass the RSDP address to the kernel, mostly used
290 on machines running EFI runtime service to boot the
291 second kernel for kdump.
293 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
294 Format: To spoof as Windows 98: ="Microsoft Windows"
296 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
297 acpi_osi="string1" # add string1
298 acpi_osi="!string2" # remove string2
299 acpi_osi=!* # remove all strings
300 acpi_osi=! # disable all built-in OS vendor
302 acpi_osi= # disable all strings
304 'acpi_osi=!' can be used in combination with single or
305 multiple 'acpi_osi="string1"' to support specific OS
306 vendor string(s). Note that such command can only
307 affect the default state of the OS vendor strings, thus
308 it cannot affect the default state of the feature group
309 strings and the current state of the OS vendor strings,
310 specifying it multiple times through kernel command line
311 is meaningless. This command is useful when one do not
312 care about the state of the feature group strings which
313 should be controlled by the OSPM.
315 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
316 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
317 can make '_OSI("Windows 2000")' TRUE.
319 'acpi_osi=' cannot be used in combination with other
320 'acpi_osi=' command lines, the _OSI method will not
321 exist in the ACPI namespace. NOTE that such command can
322 only affect the _OSI support state, thus specifying it
323 multiple times through kernel command line is also
326 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
329 'acpi_osi=!*' can be used in combination with single or
330 multiple 'acpi_osi="string1"' to support specific
331 string(s). Note that such command can affect the
332 current state of both the OS vendor strings and the
333 feature group strings, thus specifying it multiple times
334 through kernel command line is meaningful. But it may
335 still not able to affect the final state of a string if
336 there are quirks related to this string. This command
337 is useful when one want to control the state of the
338 feature group strings to debug BIOS issues related to
341 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
342 '_OSI("Module Device")' FALSE.
343 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
344 '_OSI("Module Device")' TRUE.
345 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
347 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
349 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
350 they all will make '_OSI("Windows 2000")' TRUE.
353 Override the pmtimer bug detection: force the kernel
354 to assume that this machine's pmtimer latches its value
355 and always returns good values.
357 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
358 Format: { level | edge | high | low }
360 acpi_skip_timer_override [HW,ACPI]
361 Recognize and ignore IRQ0/pin2 Interrupt Override.
362 For broken nForce2 BIOS resulting in XT-PIC timer.
364 acpi_sleep= [HW,ACPI] Sleep options
365 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
366 old_ordering, nonvs, sci_force_enable }
367 See Documentation/power/video.txt for information on
369 s3_beep is for debugging; it makes the PC's speaker beep
370 as soon as the kernel's real-mode entry point is called.
371 s4_nohwsig prevents ACPI hardware signature from being
372 used during resume from hibernation.
373 old_ordering causes the ACPI 1.0 ordering of the _PTS
374 control method, with respect to putting devices into
375 low power states, to be enforced (the ACPI 2.0 ordering
376 of _PTS is used by default).
377 nonvs prevents the kernel from saving/restoring the
378 ACPI NVS memory during suspend/hibernation and resume.
379 sci_force_enable causes the kernel to set SCI_EN directly
380 on resume from S1/S3 (which is against the ACPI spec,
381 but some broken systems don't work without it).
383 acpi_use_timer_override [HW,ACPI]
384 Use timer override. For some broken Nvidia NF5 boards
385 that require a timer override, but don't have HPET
387 add_efi_memmap [EFI; X86] Include EFI memory map in
388 kernel's map of available physical RAM.
391 { off | try_unsupported }
392 off: disable AGP support
393 try_unsupported: try to drive unsupported chipsets
394 (may crash computer or cause data corruption)
397 See Documentation/sound/alsa/alsa-parameters.txt
400 Allow the default userspace alignment fault handler
401 behaviour to be specified. Bit 0 enables warnings,
402 bit 1 enables fixups, and bit 2 sends a segfault.
404 align_va_addr= [X86-64]
405 Align virtual addresses by clearing slice [14:12] when
406 allocating a VMA at process creation time. This option
407 gives you up to 3% performance improvement on AMD F15h
408 machines (where it is enabled by default) for a
409 CPU-intensive style benchmark, and it can vary highly in
410 a microbenchmark depending on workload and compiler.
412 32: only for 32-bit processes
413 64: only for 64-bit processes
414 on: enable for both 32- and 64-bit processes
415 off: disable for both 32- and 64-bit processes
417 alloc_snapshot [FTRACE]
418 Allocate the ftrace snapshot buffer on boot up when the
419 main buffer is allocated. This is handy if debugging
420 and you need to use tracing_snapshot() on boot up, and
421 do not want to use tracing_snapshot_alloc() as it needs
422 to be done where GFP_KERNEL allocations are allowed.
424 amd_iommu= [HW,X86-64]
425 Pass parameters to the AMD IOMMU driver in the system.
427 fullflush - enable flushing of IO/TLB entries when
428 they are unmapped. Otherwise they are
429 flushed before they will be reused, which
431 off - do not initialize any AMD IOMMU found in
433 force_isolation - Force device isolation for all
434 devices. The IOMMU driver is not
435 allowed anymore to lift isolation
436 requirements as needed. This option
437 does not override iommu=pt
439 amd_iommu_dump= [HW,X86-64]
440 Enable AMD IOMMU driver option to dump the ACPI table
441 for AMD IOMMU. With this option enabled, AMD IOMMU
442 driver will print ACPI tables for AMD IOMMU during
443 IOMMU initialization.
445 amijoy.map= [HW,JOY] Amiga joystick support
446 Map of devices attached to JOY0DAT and JOY1DAT
448 See also Documentation/input/joystick.txt
450 analog.map= [HW,JOY] Analog joystick and gamepad support
451 Specifies type or capabilities of an analog joystick
452 connected to one of 16 gameports
453 Format: <type1>,<type2>,..<type16>
456 Power management functions (SPARCstation-4/5 + deriv.)
458 Disable APC CPU standby support. SPARCstation-Fox does
459 not play well with APC CPU idle - disable it if you have
460 APC and your system crashes randomly.
462 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
463 Change the output verbosity whilst booting
464 Format: { quiet (default) | verbose | debug }
465 Change the amount of debugging information output
466 when initialising the APIC and IO-APIC components.
469 See Documentation/networking/ipv6.txt.
471 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
472 Limit apic dumping. The parameter defines the maximal
473 number of local apics being dumped. Also it is possible
474 to set it to "all" by meaning -- no limit here.
475 Format: { 1 (default) | 2 | ... | all }.
476 The parameter valid if only apic=debug or
477 apic=verbose is specified.
478 Example: apic=debug show_lapic=all
480 apm= [APM] Advanced Power Management
481 See header of arch/x86/kernel/apm_32.c.
483 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
484 Format: <io>,<irq>,<nodeID>
488 atarimouse= [HW,MOUSE] Atari Mouse
490 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
491 EzKey and similar keyboards
493 atkbd.reset= [HW] Reset keyboard during initialization
495 atkbd.set= [HW] Select keyboard code set
496 Format: <int> (2 = AT (default), 3 = PS/2)
498 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
501 atkbd.softraw= [HW] Choose between synthetic and real raw mode
502 Format: <bool> (0 = real, 1 = synthetic (default))
504 atkbd.softrepeat= [HW]
505 Use software keyboard repeat
507 audit= [KNL] Enable the audit sub-system
508 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
509 0 - kernel audit is disabled and can not be enabled
510 until the next reboot
511 unset - kernel audit is initialized but disabled and
512 will be fully enabled by the userspace auditd.
513 1 - kernel audit is initialized and partially enabled,
514 storing at most audit_backlog_limit messages in
515 RAM until it is fully enabled by the userspace
519 audit_backlog_limit= [KNL] Set the audit queue size limit.
520 Format: <int> (must be >=0)
523 baycom_epp= [HW,AX25]
526 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
528 See header of drivers/net/hamradio/baycom_par.c.
530 baycom_ser_fdx= [HW,AX25]
531 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
532 Format: <io>,<irq>,<mode>[,<baud>]
533 See header of drivers/net/hamradio/baycom_ser_fdx.c.
535 baycom_ser_hdx= [HW,AX25]
536 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
537 Format: <io>,<irq>,<mode>
538 See header of drivers/net/hamradio/baycom_ser_hdx.c.
540 blkdevparts= Manual partition parsing of block device(s) for
541 embedded devices based on command line input.
542 See Documentation/block/cmdline-partition.txt
544 boot_delay= Milliseconds to delay each printk during boot.
545 Values larger than 10 seconds (10000) are changed to
549 bootmem_debug [KNL] Enable bootmem allocator debug messages.
551 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
552 bttv.radio= Most important insmod options are available as
554 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
557 bulk_remove=off [PPC] This parameter disables the use of the pSeries
558 firmware feature for flushing multiple hpte entries
561 c101= [NET] Moxa C101 synchronous serial card
563 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
564 Sometimes CPU hardware bugs make them report the cache
565 size incorrectly. The kernel will attempt work arounds
566 to fix known problems, but for some CPUs it is not
567 possible to determine what the correct size should be.
568 This option provides an override for these situations.
570 ca_keys= [KEYS] This parameter identifies a specific key(s) on
571 the system trusted keyring to be used for certificate
573 format: { id:<keyid> | builtin }
575 cca= [MIPS] Override the kernel pages' cache coherency
576 algorithm. Accepted values range from 0 to 7
577 inclusive. See arch/mips/include/asm/pgtable-bits.h
578 for platform specific values (SB1, Loongson3 and
581 ccw_timeout_log [S390]
582 See Documentation/s390/CommonIO for details.
584 cgroup_disable= [KNL] Disable a particular controller
585 Format: {name of the controller(s) to disable}
586 The effects of cgroup_disable=foo are:
587 - foo isn't auto-mounted if you mount all cgroups in
589 - foo isn't visible as an individually mountable
591 {Currently only "memory" controller deal with this and
592 cut the overhead, others just disable the usage. So
593 only cgroup_disable=memory is actually worthy}
595 checkreqprot [SELINUX] Set initial checkreqprot flag value.
596 Format: { "0" | "1" }
597 See security/selinux/Kconfig help text.
598 0 -- check protection applied by kernel (includes
599 any implied execute protection).
600 1 -- check protection requested by application.
601 Default value is set via a kernel config option.
602 Value can be changed at runtime via
603 /selinux/checkreqprot.
606 See Documentation/s390/CommonIO for details.
609 Prevents the clock framework from automatically gating
610 clocks that have not been explicitly enabled by a Linux
611 device driver but are enabled in hardware at reset or
612 by the bootloader/firmware. Note that this does not
613 force such clocks to be always-on nor does it reserve
614 those clocks in any way. This parameter is useful for
615 debug and development, but should not be needed on a
616 platform with proper driver support. For more
617 information, see Documentation/clk.txt.
619 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
621 Forces specified clocksource (if available) to be used
622 when calculating gettimeofday(). If specified
623 clocksource is not available, it defaults to PIT.
624 Format: { pit | tsc | cyclone | pmtmr }
626 clocksource= Override the default clocksource
628 Override the default clocksource and use the clocksource
629 with the name specified.
630 Some clocksource names to choose from, depending on
632 [all] jiffies (this is the base, fallback clocksource)
634 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
635 pxa_timer,timer3,32k_counter,timer0_1
637 [X86-32] pit,hpet,tsc;
638 scx200_hrt on Geode; cyclone on IBM x440
646 clearcpuid=BITNUM [X86]
647 Disable CPUID feature X for the kernel. See
648 arch/x86/include/asm/cpufeature.h for the valid bit
649 numbers. Note the Linux specific bits are not necessarily
650 stable over kernel options, but the vendor specific
652 Also note that user programs calling CPUID directly
653 or using the feature without checking anything
654 will still see it. This just prevents it from
655 being used by the kernel or shown in /proc/cpuinfo.
656 Also note the kernel might malfunction if you disable
659 cma=nn[MG]@[start[MG][-end[MG]]]
661 Sets the size of kernel global memory area for
662 contiguous memory allocations and optionally the
663 placement constraint by the physical address range of
664 memory allocations. A value of 0 disables CMA
665 altogether. For more information, see
666 include/linux/dma-contiguous.h
668 cmo_free_hint= [PPC] Format: { yes | no }
669 Specify whether pages are marked as being inactive
670 when they are freed. This is used in CMO environments
671 to determine OS memory pressure for page stealing by
675 coherent_pool=nn[KMG] [ARM,KNL]
676 Sets the size of memory pool for coherent, atomic dma
677 allocations, by default set to 256K.
679 code_bytes [X86] How many bytes of object code to print
684 com20020= [HW,NET] ARCnet - COM20020 chipset
686 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
688 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
692 ARCnet - COM90xx chipset (memory-mapped buffers)
693 Format: <io>[,<irq>[,<memstart>]]
695 condev= [HW,S390] console device
698 console= [KNL] Output console device and options.
700 tty<n> Use the virtual console device <n>.
704 Use the specified serial port. The options are of
705 the form "bbbbpnf", where "bbbb" is the baud rate,
706 "p" is parity ("n", "o", or "e"), "n" is number of
707 bits, and "f" is flow control ("r" for RTS or
708 omit it). Default is "9600n8".
710 See Documentation/serial-console.txt for more
712 Documentation/networking/netconsole.txt for an
715 uart[8250],io,<addr>[,options]
716 uart[8250],mmio,<addr>[,options]
717 uart[8250],mmio32,<addr>[,options]
718 uart[8250],0x<addr>[,options]
719 Start an early, polled-mode console on the 8250/16550
720 UART at the specified I/O port or MMIO address,
721 switching to the matching ttyS device later.
722 MMIO inter-register address stride is either 8-bit
723 (mmio) or 32-bit (mmio32).
724 If none of [io|mmio|mmio32], <addr> is assumed to be
725 equivalent to 'mmio'. 'options' are specified in the
726 same format described for ttyS above; if unspecified,
727 the h/w is not re-initialized.
729 hvc<n> Use the hypervisor console device <n>. This is for
730 both Xen and PowerPC hypervisors.
732 If the device connected to the port is not a TTY but a braille
733 device, prepend "brl," before the device type, for instance
735 For now, only VisioBraille is supported.
737 consoleblank= [KNL] The console blank (screen saver) timeout in
738 seconds. Defaults to 10*60 = 10mins. A value of 0
739 disables the blank timer.
742 [KNL] Change the default value for
743 /proc/<pid>/coredump_filter.
744 See also Documentation/filesystems/proc.txt.
746 cpuidle.off=1 [CPU_IDLE]
747 disable the cpuidle sub-system
750 [X86] Delay for N microsec between assert and de-assert
751 of APIC INIT to start processors. This delay occurs
752 on every CPU online, such as boot, and resume from suspend.
755 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
757 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
759 crashkernel=size[KMG][@offset[KMG]]
760 [KNL] Using kexec, Linux can switch to a 'crash kernel'
761 upon panic. This parameter reserves the physical
762 memory region [offset, offset + size] for that kernel
763 image. If '@offset' is omitted, then a suitable offset
764 is selected automatically. Check
765 Documentation/kdump/kdump.txt for further details.
767 crashkernel=range1:size1[,range2:size2,...][@offset]
768 [KNL] Same as above, but depends on the memory
769 in the running system. The syntax of range is
770 start-[end] where start and end are both
771 a memory unit (amount[KMG]). See also
772 Documentation/kdump/kdump.txt for an example.
774 crashkernel=size[KMG],high
775 [KNL, x86_64] range could be above 4G. Allow kernel
776 to allocate physical memory region from top, so could
777 be above 4G if system have more than 4G ram installed.
778 Otherwise memory region will be allocated below 4G, if
780 It will be ignored if crashkernel=X is specified.
781 crashkernel=size[KMG],low
782 [KNL, x86_64] range under 4G. When crashkernel=X,high
783 is passed, kernel could allocate physical memory region
784 above 4G, that cause second kernel crash on system
785 that require some amount of low memory, e.g. swiotlb
786 requires at least 64M+32K low memory. Kernel would
787 try to allocate 72M below 4G automatically.
788 This one let user to specify own low range under 4G
789 for second kernel instead.
790 0: to disable low allocation.
791 It will be ignored when crashkernel=X,high is not used
792 or memory reserved is below 4G.
797 cs89x0_media= [HW,NET]
798 Format: { rj45 | aui | bnc }
801 See header of drivers/s390/block/dasd_devmap.c.
803 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
804 (one device per port)
805 Format: <port#>,<type>
806 See also Documentation/input/joystick-parport.txt
808 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
809 time. See Documentation/dynamic-debug-howto.txt for
810 details. Deprecated, see dyndbg.
812 debug [KNL] Enable kernel debugging (events log level).
815 [KNL] verbose self-tests
817 Print debugging info while doing the locking API
819 We default to 0 (no extra messages), setting it to
820 1 will print _a lot_ more information - normally
821 only useful to kernel developers.
823 debug_objects [KNL] Enable object debugging
826 [KNL] Disable object debugging
828 debug_guardpage_minorder=
829 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
830 parameter allows control of the order of pages that will
831 be intentionally kept free (and hence protected) by the
832 buddy allocator. Bigger value increase the probability
833 of catching random memory corruption, but reduce the
834 amount of memory for normal system use. The maximum
835 possible value is MAX_ORDER/2. Setting this parameter
836 to 1 or 2 should be enough to identify most random
837 memory corruption problems caused by bugs in kernel or
838 driver code when a CPU writes to (or reads from) a
839 random memory location. Note that there exists a class
840 of memory corruptions problems caused by buggy H/W or
841 F/W or by drivers badly programing DMA (basically when
842 memory is written at bus level and the CPU MMU is
843 bypassed) which are not detectable by
844 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
845 tracking down these problems.
848 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
849 parameter enables the feature at boot time. In
850 default, it is disabled. We can avoid allocating huge
851 chunk of memory for debug pagealloc if we don't enable
852 it at boot time and the system will work mostly same
853 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
854 on: enable the feature
856 debugpat [X86] Enable PAT debugging
858 decnet.addr= [HW,NET]
859 Format: <area>[,<node>]
860 See also Documentation/networking/decnet.txt.
863 [same as hugepagesz=] The size of the default
864 HugeTLB page size. This is the size represented by
865 the legacy /proc/ hugepages APIs, used for SHM, and
866 default size when mounting hugetlbfs filesystems.
867 Defaults to the default architecture's huge page size
871 Set number of hash buckets for dentry cache.
874 See Documentation/networking/ipv6.txt.
876 disable_cpu_apicid= [X86,APIC,SMP]
878 The number of initial APIC ID for the
879 corresponding CPU to be disabled at boot,
880 mostly used for the kdump 2nd kernel to
881 disable BSP to wake up multiple CPUs without
882 causing system reset or hang due to sending
885 disable_ddw [PPC/PSERIES]
886 Disable Dynamic DMA Window support. Use this if
887 to workaround buggy firmware.
890 See Documentation/networking/ipv6.txt.
892 disable_mtrr_cleanup [X86]
893 The kernel tries to adjust MTRR layout from continuous
894 to discrete, to make X server driver able to add WB
895 entry later. This parameter disables that.
897 disable_mtrr_trim [X86, Intel and AMD only]
898 By default the kernel will trim any uncacheable
899 memory out of your available memory pool based on
900 MTRR settings. This parameter disables that behavior,
901 possibly causing your machine to run very slowly.
903 disable_timer_pin_1 [X86]
904 Disable PIN 1 of APIC timer
905 Can be useful to work around chipset bugs.
907 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
908 this option disables the debugging code at boot.
910 dma_debug_entries=<number>
911 This option allows to tune the number of preallocated
912 entries for DMA-API debugging code. One entry is
913 required per DMA-API allocation. Use this if the
914 DMA-API debugging code disables itself because the
915 architectural default is too low.
917 dma_debug_driver=<driver_name>
918 With this option the DMA-API debugging driver
919 filter feature can be enabled at boot time. Just
920 pass the driver to filter for as the parameter.
921 The filter can be disabled or changed to another
922 driver later using sysfs.
924 drm_kms_helper.edid_firmware=[<connector>:]<file>
925 Broken monitors, graphic adapters and KVMs may
926 send no or incorrect EDID data sets. This parameter
927 allows to specify an EDID data set in the
928 /lib/firmware directory that is used instead.
929 Generic built-in EDID data sets are used, if one of
930 edid/1024x768.bin, edid/1280x1024.bin,
931 edid/1680x1050.bin, or edid/1920x1080.bin is given
932 and no file with the same name exists. Details and
933 instructions how to build your own EDID data are
934 available in Documentation/EDID/HOWTO.txt. An EDID
935 data set will only be used for a particular connector,
936 if its name and a colon are prepended to the EDID
941 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
942 module.dyndbg[="val"]
943 Enable debug messages at boot time. See
944 Documentation/dynamic-debug-howto.txt for details.
946 nompx [X86] Disables Intel Memory Protection Extensions.
947 See Documentation/x86/intel_mpx.txt for more
948 information about the feature.
951 on enable eager fpu restore
952 off disable eager fpu restore
953 auto selects the default scheme, which automatically
954 enables eagerfpu restore for xsaveopt.
956 early_ioremap_debug [KNL]
957 Enable debug messages in early_ioremap support. This
958 is useful for tracking down temporary early mappings
959 which are not unmapped.
961 earlycon= [KNL] Output early console device and options.
964 Start an early, polled-mode console on a cadence serial
965 port at the specified address. The cadence serial port
966 must already be setup and configured. Options are not
969 uart[8250],io,<addr>[,options]
970 uart[8250],mmio,<addr>[,options]
971 uart[8250],mmio32,<addr>[,options]
972 uart[8250],0x<addr>[,options]
973 Start an early, polled-mode console on the 8250/16550
974 UART at the specified I/O port or MMIO address.
975 MMIO inter-register address stride is either 8-bit
976 (mmio) or 32-bit (mmio32).
977 If none of [io|mmio|mmio32], <addr> is assumed to be
978 equivalent to 'mmio'. 'options' are specified in the
979 same format described for "console=ttyS<n>"; if
980 unspecified, the h/w is not initialized.
983 Start an early, polled-mode console on a pl011 serial
984 port at the specified address. The pl011 serial port
985 must already be setup and configured. Options are not
989 Start an early, polled-mode console on an msm serial
990 port at the specified address. The serial port
991 must already be setup and configured. Options are not
995 Start an early, polled-mode console on an msm serial
996 dm port at the specified address. The serial port
997 must already be setup and configured. Options are not
1000 smh Use ARM semihosting calls for early console.
1008 Use early console provided by serial driver available
1009 on Samsung SoCs, requires selecting proper type and
1010 a correct base address of the selected UART port. The
1011 serial port must already be setup and configured.
1012 Options are not yet supported.
1014 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1018 earlyprintk=serial[,ttySn[,baudrate]]
1019 earlyprintk=serial[,0x...[,baudrate]]
1020 earlyprintk=ttySn[,baudrate]
1021 earlyprintk=dbgp[debugController#]
1023 earlyprintk is useful when the kernel crashes before
1024 the normal console is initialized. It is not enabled by
1025 default because it has some cosmetic problems.
1027 Append ",keep" to not disable it when the real console
1030 Only one of vga, efi, serial, or usb debug port can
1033 Currently only ttyS0 and ttyS1 may be specified by
1034 name. Other I/O ports may be explicitly specified
1035 on some architectures (x86 and arm at least) by
1036 replacing ttySn with an I/O port address, like this:
1037 earlyprintk=serial,0x1008,115200
1038 You can find the port for a given device in
1039 /proc/tty/driver/serial:
1040 2: uart:ST16650V2 port:00001008 irq:18 ...
1042 Interaction with the standard serial driver is not
1045 The VGA and EFI output is eventually overwritten by
1048 The xen output can only be used by Xen PV guests.
1050 edac_report= [HW,EDAC] Control how to report EDAC event
1051 Format: {"on" | "off" | "force"}
1052 on: enable EDAC to report H/W event. May be overridden
1053 by other higher priority error reporting module.
1054 off: disable H/W event reporting through EDAC.
1055 force: enforce the use of EDAC to report H/W event.
1058 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1061 This is designed to be used in conjunction with
1062 the boot argument: earlyprintk=vga
1065 Format: {"off" | "on" | "skip[mbr]"}
1068 Format: { "old_map", "nochunk", "noruntime", "debug" }
1069 old_map [X86-64]: switch to the old ioremap-based EFI
1070 runtime services mapping. 32-bit still uses this one by
1072 nochunk: disable reading files in "chunks" in the EFI
1073 boot stub, as chunking can cause problems with some
1074 firmware implementations.
1075 noruntime : disable EFI runtime services support
1076 debug: enable misc debug output
1078 efi_no_storage_paranoia [EFI; X86]
1079 Using this parameter you can use more than 50% of
1080 your efi variable storage. Use this parameter only if
1081 you are really sure that your UEFI does sane gc and
1082 fulfills the spec otherwise your board may brick.
1084 eisa_irq_edge= [PARISC,HW]
1085 See header of drivers/parisc/eisa.c.
1088 See comment before function elanfreq_setup() in
1089 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1092 Format: {"cfq" | "deadline" | "noop"}
1093 See Documentation/block/cfq-iosched.txt and
1094 Documentation/block/deadline-iosched.txt for details.
1096 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1097 Specifies physical address of start of kernel core
1098 image elf header and optionally the size. Generally
1099 kexec loader will pass this option to capture kernel.
1100 See Documentation/kdump/kdump.txt for details.
1102 enable_mtrr_cleanup [X86]
1103 The kernel tries to adjust MTRR layout from continuous
1104 to discrete, to make X server driver able to add WB
1105 entry later. This parameter enables that.
1107 enable_timer_pin_1 [X86]
1108 Enable PIN 1 of APIC timer
1109 Can be useful to work around chipset bugs
1110 (in particular on some ATI chipsets).
1111 The kernel tries to set a reasonable default.
1113 enforcing [SELINUX] Set initial enforcing status.
1115 See security/selinux/Kconfig help text.
1116 0 -- permissive (log only, no denials).
1117 1 -- enforcing (deny and log).
1119 Value can be changed at runtime via /selinux/enforce.
1122 Disable Error Record Serialization Table (ERST)
1125 ether= [HW,NET] Ethernet cards parameters
1126 This option is obsoleted by the "netdev=" option, which
1127 has equivalent usage. See its documentation for details.
1131 Permit 'security.evm' to be updated regardless of
1132 current integrity status.
1136 fail_make_request=[KNL]
1137 General fault injection mechanism.
1138 Format: <interval>,<probability>,<space>,<times>
1139 See also Documentation/fault-injection/.
1142 See Documentation/blockdev/floppy.txt.
1144 force_pal_cache_flush
1145 [IA-64] Avoid check_sal_cache_flush which may hang on
1146 buggy SAL_CACHE_FLUSH implementations. Using this
1147 parameter will force ia64_sal_cache_flush to call
1148 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1151 Forcefully enable Physical Address Extension (PAE).
1152 Many Pentium M systems disable PAE but may have a
1153 functionally usable PAE implementation.
1154 Warning: use of this parameter will taint the kernel
1155 and may cause unknown problems.
1158 [FTRACE] will set and start the specified tracer
1159 as early as possible in order to facilitate early
1162 ftrace_dump_on_oops[=orig_cpu]
1163 [FTRACE] will dump the trace buffers on oops.
1164 If no parameter is passed, ftrace will dump
1165 buffers of all CPUs, but if you pass orig_cpu, it will
1166 dump only the buffer of the CPU that triggered the
1169 ftrace_filter=[function-list]
1170 [FTRACE] Limit the functions traced by the function
1171 tracer at boot up. function-list is a comma separated
1172 list of functions. This list can be changed at run
1173 time by the set_ftrace_filter file in the debugfs
1176 ftrace_notrace=[function-list]
1177 [FTRACE] Do not trace the functions specified in
1178 function-list. This list can be changed at run time
1179 by the set_ftrace_notrace file in the debugfs
1182 ftrace_graph_filter=[function-list]
1183 [FTRACE] Limit the top level callers functions traced
1184 by the function graph tracer at boot up.
1185 function-list is a comma separated list of functions
1186 that can be changed at run time by the
1187 set_graph_function file in the debugfs tracing directory.
1189 ftrace_graph_notrace=[function-list]
1190 [FTRACE] Do not trace from the functions specified in
1191 function-list. This list is a comma separated list of
1192 functions that can be changed at run time by the
1193 set_graph_notrace file in the debugfs tracing directory.
1196 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1197 support via parallel port (up to 5 devices per port)
1198 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1199 See also Documentation/input/joystick-parport.txt
1203 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1207 gcov_persist= [GCOV] When non-zero (default), profiling data for
1208 kernel modules is saved and remains accessible via
1209 debugfs, even when the module is unloaded/reloaded.
1210 When zero, profiling data is discarded and associated
1211 debugfs files are removed at module unload time.
1213 gpt [EFI] Forces disk with valid GPT signature but
1214 invalid Protective MBR to be treated as GPT. If the
1215 primary GPT is corrupted, it enables the backup/alternate
1216 GPT to be used instead.
1218 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1219 the "Enable 0" bit of the configuration register.
1222 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1223 the "Enable 0" bit of the configuration register.
1226 grcan.select= [HW] Select which physical interface to use.
1229 grcan.txsize= [HW] Sets the size of the tx buffer.
1230 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1232 grcan.rxsize= [HW] Sets the size of the rx buffer.
1233 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1236 hashdist= [KNL,NUMA] Large hashes allocated during boot
1237 are distributed across NUMA nodes. Defaults on
1238 for 64-bit NUMA, off otherwise.
1239 Format: 0 | 1 (for off | on)
1241 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1243 hd= [EIDE] (E)IDE hard drive subsystem geometry
1244 Format: <cyl>,<head>,<sect>
1247 Disable Hardware Error Source Table (HEST) support;
1248 corresponding firmware-first mode error processing
1249 logic will be disabled.
1251 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1252 size of <nn>. This works even on boxes that have no
1253 highmem otherwise. This also works to reduce highmem
1254 size on bigger boxes.
1256 highres= [KNL] Enable/disable high resolution timer mode.
1257 Valid parameters: "on", "off"
1261 See Documentation/isdn/README.HiSax.
1265 hpet= [X86-32,HPET] option to control HPET usage
1266 Format: { enable (default) | disable | force |
1268 disable: disable HPET and use PIT instead
1269 force: allow force enabled of undocumented chips (ICH4,
1271 verbose: show contents of HPET registers during setup
1273 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1274 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1276 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1277 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1278 On x86-64 and powerpc, this option can be specified
1279 multiple times interleaved with hugepages= to reserve
1280 huge pages of different sizes. Valid pages sizes on
1281 x86-64 are 2M (when the CPU supports "pse") and 1G
1282 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1284 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1285 terminal devices. Valid values: 0..8
1286 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1287 If specified, z/VM IUCV HVC accepts connections
1288 from listed z/VM user IDs only.
1290 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1291 hardware thread id mappings.
1292 Format: <cpu>:<hwthread>
1295 Do not unregister boot console at start. This is only
1296 useful for debugging when something happens in the window
1297 between unregistering the boot console and initializing
1300 i2c_bus= [HW] Override the default board specific I2C bus speed
1301 or register an additional I2C bus that is not
1302 registered from board initialization code.
1306 i8042.debug [HW] Toggle i8042 debug mode
1307 i8042.direct [HW] Put keyboard port into non-translated mode
1308 i8042.dumbkbd [HW] Pretend that controller can only read data from
1309 keyboard and cannot control its state
1310 (Don't attempt to blink the leds)
1311 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1312 i8042.nokbd [HW] Don't check/create keyboard port
1313 i8042.noloop [HW] Disable the AUX Loopback command while probing
1315 i8042.nomux [HW] Don't check presence of an active multiplexing
1317 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1319 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1320 i8042.reset [HW] Reset the controller during init and cleanup
1321 i8042.unlock [HW] Unlock (ignore) the keylock
1322 i8042.kbdreset [HW] Reset device connected to KBD port
1326 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1327 indicates that the driver is running on unsupported
1329 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1330 does not match list of supported models.
1332 [HW] Report power status in /proc/i8k
1333 (disabled by default)
1334 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1337 i915.invert_brightness=
1338 [DRM] Invert the sense of the variable that is used to
1339 set the brightness of the panel backlight. Normally a
1340 brightness value of 0 indicates backlight switched off,
1341 and the maximum of the brightness value sets the backlight
1342 to maximum brightness. If this parameter is set to 0
1343 (default) and the machine requires it, or this parameter
1344 is set to 1, a brightness value of 0 sets the backlight
1345 to maximum brightness, and the maximum of the brightness
1346 value switches the backlight off.
1347 -1 -- never invert brightness
1348 0 -- machine default
1349 1 -- force brightness inversion
1352 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1354 ide-core.nodma= [HW] (E)IDE subsystem
1355 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1356 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1357 .cdrom .chs .ignore_cable are additional options
1358 See Documentation/ide/ide.txt.
1360 ide-generic.probe-mask= [HW] (E)IDE subsystem
1362 Probe mask for legacy ISA IDE ports. Depending on
1363 platform up to 6 ports are supported, enabled by
1364 setting corresponding bits in the mask to 1. The
1365 default value is 0x0, which has a special meaning.
1366 On systems that have PCI, it triggers scanning the
1367 PCI bus for the first and the second port, which
1368 are then probed. On systems without PCI the value
1369 of 0x0 enables probing the two first ports as if it
1372 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1373 Claim all unknown PCI IDE storage controllers.
1376 Format: idle=poll, idle=halt, idle=nomwait
1377 Poll forces a polling idle loop that can slightly
1378 improve the performance of waking up a idle CPU, but
1379 will use a lot of power and make the system run hot.
1381 idle=halt: Halt is forced to be used for CPU idle.
1382 In such case C2/C3 won't be used again.
1383 idle=nomwait: Disable mwait for CPU C-states
1385 ignore_loglevel [KNL]
1386 Ignore loglevel setting - this will print /all/
1387 kernel messages to the console. Useful for debugging.
1388 We also add it as printk module parameter, so users
1389 could change it dynamically, usually by
1390 /sys/module/printk/parameters/ignore_loglevel.
1392 ihash_entries= [KNL]
1393 Set number of hash buckets for inode cache.
1395 ima_appraise= [IMA] appraise integrity measurements
1396 Format: { "off" | "enforce" | "fix" | "log" }
1399 ima_appraise_tcb [IMA]
1400 The builtin appraise policy appraises all files
1404 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1408 The list of supported hash algorithms is defined
1409 in crypto/hash_info.h.
1412 Load a policy which meets the needs of the Trusted
1413 Computing Base. This means IMA will measure all
1414 programs exec'd, files mmap'd for exec, and all files
1415 opened for read by uid=0.
1418 Select one of defined IMA measurements template formats.
1419 Formats: { "ima" | "ima-ng" }
1423 [IMA] Define a custom template format.
1424 Format: { "field1|...|fieldN" }
1426 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1427 Format: <min_file_size>
1428 Set the minimal file size for using asynchronous hash.
1429 If left unspecified, ahash usage is disabled.
1431 ahash performance varies for different data sizes on
1432 different crypto accelerators. This option can be used
1433 to achieve the best performance for a particular HW.
1435 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1437 Set hashing buffer size. Default: 4k.
1439 ahash performance varies for different chunk sizes on
1440 different crypto accelerators. This option can be used
1441 to achieve best performance for particular HW.
1445 Run specified binary instead of /sbin/init as init
1448 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1449 for working out where the kernel is dying during
1452 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1453 initcall functions. Useful for debugging built-in
1454 modules and initcalls.
1456 initrd= [BOOT] Specify the location of the initial ramdisk
1458 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1461 int_pln_enable [x86] Enable power limit notification interrupt
1463 integrity_audit=[IMA]
1464 Format: { "0" | "1" }
1465 0 -- basic integrity auditing messages. (Default)
1466 1 -- additional integrity auditing messages.
1468 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1470 Enable intel iommu driver.
1472 Disable intel iommu driver.
1473 igfx_off [Default Off]
1474 By default, gfx is mapped as normal device. If a gfx
1475 device has a dedicated DMAR unit, the DMAR unit is
1476 bypassed by not enabling DMAR with this option. In
1477 this case, gfx device will use physical address for
1480 With this option iommu will not optimize to look
1481 for io virtual address below 32-bit forcing dual
1482 address cycle on pci bus for cards supporting greater
1483 than 32-bit addressing. The default is to look
1484 for translation below 32-bit and if not available
1485 then look in the higher range.
1486 strict [Default Off]
1487 With this option on every unmap_single operation will
1488 result in a hardware IOTLB flush operation as opposed
1489 to batching them for performance.
1490 sp_off [Default Off]
1491 By default, super page will be supported if Intel IOMMU
1492 has the capability. With this option, super page will
1494 ecs_off [Default Off]
1495 By default, extended context tables will be supported if
1496 the hardware advertises that it has support both for the
1497 extended tables themselves, and also PASID support. With
1498 this option set, extended tables will not be used even
1499 on hardware which claims to support them.
1501 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1502 0 disables intel_idle and fall back on acpi_idle.
1503 1 to 6 specify maximum depth of C-state.
1507 Do not enable intel_pstate as the default
1508 scaling driver for the supported processors
1510 Enable intel_pstate on systems that prohibit it by default
1511 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1512 instead of acpi-cpufreq may disable platform features, such
1513 as thermal controls and power capping, that rely on ACPI
1514 P-States information being indicated to OSPM and therefore
1515 should be used with caution. This option does not work with
1516 processors that aren't supported by the intel_pstate driver
1517 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1519 Do not enable hardware P state control (HWP)
1522 Only load intel_pstate on systems which support
1523 hardware P state control (HWP) if available.
1525 intremap= [X86-64, Intel-IOMMU]
1526 on enable Interrupt Remapping (default)
1527 off disable Interrupt Remapping
1528 nosid disable Source ID checking
1530 BIOS x2APIC opt-out request will be ignored
1532 iomem= Disable strict checking of access to MMIO memory
1533 strict regions from userspace.
1548 nobypass [PPC/POWERNV]
1549 Disable IOMMU bypass, using IOMMU for PCI devices.
1552 io7= [HW] IO7 for Marvel based alpha systems
1553 See comment before marvel_specify_io7 in
1554 arch/alpha/kernel/core_marvel.c.
1556 io_delay= [X86] I/O delay method
1558 Standard port 0x80 based delay
1560 Alternate port 0xed based delay (needed on some systems)
1562 Simple two microseconds delay
1567 See Documentation/filesystems/nfs/nfsroot.txt.
1570 When an interrupt is not handled search all handlers
1571 for it. Intended to get systems with badly broken
1575 When an interrupt is not handled search all handlers
1576 for it. Also check all handlers each timer
1577 interrupt. Intended to get systems with badly broken
1581 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1583 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1585 <cpu number>,...,<cpu number>
1587 <cpu number>-<cpu number>
1588 (must be a positive range in ascending order)
1590 <cpu number>,...,<cpu number>-<cpu number>
1592 This option can be used to specify one or more CPUs
1593 to isolate from the general SMP balancing and scheduling
1594 algorithms. You can move a process onto or off an
1595 "isolated" CPU via the CPU affinity syscalls or cpuset.
1596 <cpu number> begins at 0 and the maximum value is
1597 "number of CPUs in system - 1".
1599 This option is the preferred way to isolate CPUs. The
1600 alternative -- manually setting the CPU mask of all
1601 tasks in the system -- can cause problems and
1602 suboptimal load balancer performance.
1606 ivrs_ioapic [HW,X86_64]
1607 Provide an override to the IOAPIC-ID<->DEVICE-ID
1608 mapping provided in the IVRS ACPI table. For
1609 example, to map IOAPIC-ID decimal 10 to
1610 PCI device 00:14.0 write the parameter as:
1611 ivrs_ioapic[10]=00:14.0
1613 ivrs_hpet [HW,X86_64]
1614 Provide an override to the HPET-ID<->DEVICE-ID
1615 mapping provided in the IVRS ACPI table. For
1616 example, to map HPET-ID decimal 0 to
1617 PCI device 00:14.0 write the parameter as:
1618 ivrs_hpet[0]=00:14.0
1620 js= [HW,JOY] Analog joystick
1621 See Documentation/input/joystick.txt.
1624 Enable/disable kernel and module base offset ASLR
1625 (Address Space Layout Randomization) if built into
1626 the kernel. When CONFIG_HIBERNATION is selected,
1627 kASLR is disabled by default. When kASLR is enabled,
1628 hibernation will be disabled.
1632 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1633 specifies the amount of memory usable by the kernel
1634 for non-movable allocations. The requested amount is
1635 spread evenly throughout all nodes in the system. The
1636 remaining memory in each node is used for Movable
1637 pages. In the event, a node is too small to have both
1638 kernelcore and Movable pages, kernelcore pages will
1639 take priority and other nodes will have a larger number
1640 of Movable pages. The Movable zone is used for the
1641 allocation of pages that may be reclaimed or moved
1642 by the page migration subsystem. This means that
1643 HugeTLB pages may not be allocated from this zone.
1644 Note that allocations like PTEs-from-HighMem still
1645 use the HighMem zone if it exists, and the Normal
1646 zone if it does not.
1648 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1649 Format: <Controller#>[,poll interval]
1650 The controller # is the number of the ehci usb debug
1651 port as it is probed via PCI. The poll interval is
1652 optional and is the number seconds in between
1653 each poll cycle to the debug port in case you need
1654 the functionality for interrupting the kernel with
1655 gdb or control-c on the dbgp connection. When
1656 not using this parameter you use sysrq-g to break into
1657 the kernel debugger.
1659 kgdboc= [KGDB,HW] kgdb over consoles.
1660 Requires a tty driver that supports console polling,
1661 or a supported polling keyboard driver (non-usb).
1662 Serial only format: <serial_device>[,baud]
1663 keyboard only format: kbd
1664 keyboard and serial format: kbd,<serial_device>[,baud]
1665 Optional Kernel mode setting:
1666 kms, kbd format: kms,kbd
1667 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1669 kgdbwait [KGDB] Stop kernel execution and enter the
1670 kernel debugger at the earliest opportunity.
1672 kmac= [MIPS] korina ethernet MAC address.
1673 Configure the RouterBoard 532 series on-chip
1674 Ethernet adapter MAC address.
1676 kmemleak= [KNL] Boot-time kmemleak enable/disable
1677 Valid arguments: on, off
1679 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1682 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1683 Valid arguments: 0, 1, 2
1684 kmemcheck=0 (disabled)
1685 kmemcheck=1 (enabled)
1686 kmemcheck=2 (one-shot mode)
1687 Default: 2 (one-shot mode)
1689 kstack=N [X86] Print N words from the kernel stack
1692 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1693 Default is 0 (don't ignore, but inject #GP)
1695 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1699 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1700 Default is 1 (enabled)
1702 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1704 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1706 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1707 (virtualized MMU) support on capable Intel chips.
1708 Default is 1 (enabled)
1710 kvm-intel.emulate_invalid_guest_state=
1711 [KVM,Intel] Enable emulation of invalid guest states
1712 Default is 0 (disabled)
1714 kvm-intel.flexpriority=
1715 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1716 Default is 1 (enabled)
1719 [KVM,Intel] Enable VMX nesting (nVMX).
1720 Default is 0 (disabled)
1722 kvm-intel.unrestricted_guest=
1723 [KVM,Intel] Disable unrestricted guest feature
1724 (virtualized real and unpaged mode) on capable
1725 Intel chips. Default is 1 (enabled)
1727 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1728 feature (tagged TLBs) on capable Intel chips.
1729 Default is 1 (enabled)
1735 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1738 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1739 value for LAPIC timer one-shot implementation. Default
1740 back to the programmable timer unit in the LAPIC.
1742 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1745 libata.dma= [LIBATA] DMA control
1746 libata.dma=0 Disable all PATA and SATA DMA
1747 libata.dma=1 PATA and SATA Disk DMA only
1748 libata.dma=2 ATAPI (CDROM) DMA only
1749 libata.dma=4 Compact Flash DMA only
1750 Combinations also work, so libata.dma=3 enables DMA
1751 for disks and CDROMs, but not CFs.
1753 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1754 libata.ignore_hpa=0 keep BIOS limits (default)
1755 libata.ignore_hpa=1 ignore limits, using full disk
1757 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1761 libata.force= [LIBATA] Force configurations. The format is comma
1762 separated list of "[ID:]VAL" where ID is
1763 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1764 matching port, link or device. Basically, it matches
1765 the ATA ID string printed on console by libata. If
1766 the whole ID part is omitted, the last PORT and DEVICE
1767 values are used. If ID hasn't been specified yet, the
1768 configuration applies to all ports, links and devices.
1770 If only DEVICE is omitted, the parameter applies to
1771 the port and all links and devices behind it. DEVICE
1772 number of 0 either selects the first device or the
1773 first fan-out link behind PMP device. It does not
1774 select the host link. DEVICE number of 15 selects the
1775 host link and device attached to it.
1777 The VAL specifies the configuration to force. As long
1778 as there's no ambiguity shortcut notation is allowed.
1779 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1780 The following configurations can be forced.
1782 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1783 Any ID with matching PORT is used.
1785 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1787 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1788 udma[/][16,25,33,44,66,100,133] notation is also
1791 * [no]ncq: Turn on or off NCQ.
1793 * nohrst, nosrst, norst: suppress hard, soft
1796 * rstonce: only attempt one reset during
1797 hot-unplug link recovery
1799 * dump_id: dump IDENTIFY data.
1801 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1803 * disable: Disable this device.
1805 If there are multiple matching configurations changing
1806 the same attribute, the last one is used.
1808 memblock=debug [KNL] Enable memblock debug messages.
1810 load_ramdisk= [RAM] List of ramdisks to load from floppy
1811 See Documentation/blockdev/ramdisk.txt.
1813 lockd.nlm_grace_period=P [NFS] Assign grace period.
1816 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1819 lockd.nlm_timeout=T [NFS] Assign timeout value.
1822 lockd.nlm_udpport=M [NFS] Assign UDP port.
1825 locktorture.nreaders_stress= [KNL]
1826 Set the number of locking read-acquisition kthreads.
1827 Defaults to being automatically set based on the
1828 number of online CPUs.
1830 locktorture.nwriters_stress= [KNL]
1831 Set the number of locking write-acquisition kthreads.
1833 locktorture.onoff_holdoff= [KNL]
1834 Set time (s) after boot for CPU-hotplug testing.
1836 locktorture.onoff_interval= [KNL]
1837 Set time (s) between CPU-hotplug operations, or
1838 zero to disable CPU-hotplug testing.
1840 locktorture.shuffle_interval= [KNL]
1841 Set task-shuffle interval (jiffies). Shuffling
1842 tasks allows some CPUs to go into dyntick-idle
1843 mode during the locktorture test.
1845 locktorture.shutdown_secs= [KNL]
1846 Set time (s) after boot system shutdown. This
1847 is useful for hands-off automated testing.
1849 locktorture.stat_interval= [KNL]
1850 Time (s) between statistics printk()s.
1852 locktorture.stutter= [KNL]
1853 Time (s) to stutter testing, for example,
1854 specifying five seconds causes the test to run for
1855 five seconds, wait for five seconds, and so on.
1856 This tests the locking primitive's ability to
1857 transition abruptly to and from idle.
1859 locktorture.torture_runnable= [BOOT]
1860 Start locktorture running at boot time.
1862 locktorture.torture_type= [KNL]
1863 Specify the locking implementation to test.
1865 locktorture.verbose= [KNL]
1866 Enable additional printk() statements.
1868 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1871 loglevel= All Kernel Messages with a loglevel smaller than the
1872 console loglevel will be printed to the console. It can
1873 also be changed with klogd or other programs. The
1874 loglevels are defined as follows:
1876 0 (KERN_EMERG) system is unusable
1877 1 (KERN_ALERT) action must be taken immediately
1878 2 (KERN_CRIT) critical conditions
1879 3 (KERN_ERR) error conditions
1880 4 (KERN_WARNING) warning conditions
1881 5 (KERN_NOTICE) normal but significant condition
1882 6 (KERN_INFO) informational
1883 7 (KERN_DEBUG) debug-level messages
1885 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1886 in bytes. n must be a power of two and greater
1887 than the minimal size. The minimal size is defined
1888 by LOG_BUF_SHIFT kernel config parameter. There is
1889 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1890 that allows to increase the default size depending on
1891 the number of CPUs. See init/Kconfig for more details.
1893 logo.nologo [FB] Disables display of the built-in Linux logo.
1894 This may be used to provide more screen space for
1895 kernel log messages and is useful when debugging
1896 kernel boot problems.
1898 lp=0 [LP] Specify parallel ports to use, e.g,
1899 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1900 lp=reset first parallel port). 'lp=0' disables the
1901 lp=auto printer driver. 'lp=reset' (which can be
1902 specified in addition to the ports) causes
1903 attached printers to be reset. Using
1904 lp=port1,port2,... specifies the parallel ports
1905 to associate lp devices with, starting with
1906 lp0. A port specification may be 'none' to skip
1907 that lp device, or a parport name such as
1908 'parport0'. Specifying 'lp=auto' instead of a
1909 port specification list means that device IDs
1910 from each port should be examined, to see if
1911 an IEEE 1284-compliant printer is attached; if
1912 so, the driver will manage that printer.
1913 See also header of drivers/char/lp.c.
1916 Sets loops_per_jiffy to given constant, thus avoiding
1917 time-consuming boot-time autodetection (up to 250 ms per
1918 CPU). 0 enables autodetection (default). To determine
1919 the correct value for your kernel, boot with normal
1920 autodetection and see what value is printed. Note that
1921 on SMP systems the preset will be applied to all CPUs,
1922 which is likely to cause problems if your CPUs need
1923 significantly divergent settings. An incorrect value
1924 will cause delays in the kernel to be wrong, leading to
1925 unpredictable I/O errors and other breakage. Although
1926 unlikely, in the extreme case this might damage your
1930 Format: <io>,<irq>,<dma>
1932 machvec= [IA-64] Force the use of a particular machine-vector
1933 (machvec) in a generic kernel.
1934 Example: machvec=hpzx1_swiotlb
1936 machtype= [Loongson] Share the same kernel image file between different
1938 Example: machtype=lemote-yeeloong-2f-7inch
1940 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1941 than or equal to this physical address is ignored.
1943 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1944 should make use of. maxcpus=n : n >= 0 limits the
1945 kernel to using 'n' processors. n=0 is a special case,
1946 it is equivalent to "nosmp", which also disables
1949 max_loop= [LOOP] The number of loop block devices that get
1950 (loop.max_loop) unconditionally pre-created at init time. The default
1951 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1952 of statically allocating a predefined number, loop
1953 devices can be requested on-demand with the
1954 /dev/loop-control interface.
1956 mce [X86-32] Machine Check Exception
1958 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1960 md= [HW] RAID subsystems devices and level
1961 See Documentation/md.txt.
1964 Format: <first>,<last>
1965 Specifies range of consoles to be captured by the MDA.
1967 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1968 Amount of memory to be used when the kernel is not able
1969 to see the whole system memory or for test.
1970 [X86] Work as limiting max address. Use together
1971 with memmap= to avoid physical address space collisions.
1972 Without memmap= PCI devices could be placed at addresses
1973 belonging to unused RAM.
1975 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1979 [KNL,SH] Allow user to override the default size for
1980 per-device physically contiguous DMA buffers.
1982 memmap=exactmap [KNL,X86] Enable setting of an exact
1983 E820 memory map, as specified by the user.
1984 Such memmap=exactmap lines can be constructed based on
1985 BIOS output or other requirements. See the memmap=nn@ss
1988 memmap=nn[KMG]@ss[KMG]
1989 [KNL] Force usage of a specific region of memory.
1990 Region of memory to be used is from ss to ss+nn.
1992 memmap=nn[KMG]#ss[KMG]
1993 [KNL,ACPI] Mark specific memory as ACPI data.
1994 Region of memory to be marked is from ss to ss+nn.
1996 memmap=nn[KMG]$ss[KMG]
1997 [KNL,ACPI] Mark specific memory as reserved.
1998 Region of memory to be reserved is from ss to ss+nn.
1999 Example: Exclude memory from 0x18690000-0x1869ffff
2000 memmap=64K$0x18690000
2002 memmap=0x10000$0x18690000
2004 memmap=nn[KMG]!ss[KMG]
2005 [KNL,X86] Mark specific memory as protected.
2006 Region of memory to be used, from ss to ss+nn.
2007 The memory region may be marked as e820 type 12 (0xc)
2008 and is NVDIMM or ADR memory.
2010 memory_corruption_check=0/1 [X86]
2011 Some BIOSes seem to corrupt the first 64k of
2012 memory when doing things like suspend/resume.
2013 Setting this option will scan the memory
2014 looking for corruption. Enabling this will
2015 both detect corruption and prevent the kernel
2016 from using the memory being corrupted.
2017 However, its intended as a diagnostic tool; if
2018 repeatable BIOS-originated corruption always
2019 affects the same memory, you can use memmap=
2020 to prevent the kernel from using that memory.
2022 memory_corruption_check_size=size [X86]
2023 By default it checks for corruption in the low
2024 64k, making this memory unavailable for normal
2025 use. Use this parameter to scan for
2026 corruption in more or less memory.
2028 memory_corruption_check_period=seconds [X86]
2029 By default it checks for corruption every 60
2030 seconds. Use this parameter to check at some
2031 other rate. 0 disables periodic checking.
2033 memtest= [KNL,X86,ARM] Enable memtest
2035 default : 0 <disable>
2036 Specifies the number of memtest passes to be
2037 performed. Each pass selects another test
2038 pattern from a given set of patterns. Memtest
2039 fills the memory with this pattern, validates
2040 memory contents and reserves bad memory
2041 regions that are detected.
2043 meye.*= [HW] Set MotionEye Camera parameters
2044 See Documentation/video4linux/meye.txt.
2046 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2047 Multi-Function General Purpose Timers on AMD Geode
2050 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2051 the BIOS has incorrectly applied a workaround. TinyBIOS
2052 version 0.98 is known to be affected, 0.99 fixes the
2053 problem by letting the user disable the workaround.
2057 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2058 physical address is ignored.
2060 mini2440= [ARM,HW,KNL]
2061 Format:[0..2][b][c][t]
2063 MINI2440 configuration specification:
2064 0 - The attached screen is the 3.5" TFT
2065 1 - The attached screen is the 7" TFT
2066 2 - The VGA Shield is attached (1024x768)
2067 Leaving out the screen size parameter will not load
2068 the TFT driver, and the framebuffer will be left
2070 b - Enable backlight. The TFT backlight pin will be
2071 linked to the kernel VESA blanking code and a GPIO
2072 LED. This parameter is not necessary when using the
2074 c - Enable the s3c camera interface.
2075 t - Reserved for enabling touchscreen support. The
2076 touchscreen support is not enabled in the mainstream
2077 kernel as of 2.6.30, a preliminary port can be found
2078 in the "bleeding edge" mini2440 support kernel at
2079 http://repo.or.cz/w/linux-2.6/mini2440.git
2082 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2083 parameter allows control of the logging verbosity for
2084 the additional memory initialisation checks. A value
2085 of 0 disables mminit logging and a level of 4 will
2086 log everything. Information is printed at KERN_DEBUG
2087 so loglevel=8 may also need to be specified.
2090 [KNL] When CONFIG_MODULE_SIG is set, this means that
2091 modules without (valid) signatures will fail to load.
2092 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2093 is always true, so this option does nothing.
2096 [MOUSE] Maximum time between finger touching and
2097 leaving touchpad surface for touch to be considered
2098 a tap and be reported as a left button click (for
2099 touchpads working in absolute mode only).
2101 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2102 reporting absolute coordinates, such as tablets
2103 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2104 reporting absolute coordinates, such as tablets
2106 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2107 is similar to kernelcore except it specifies the
2108 amount of memory used for migratable allocations.
2109 If both kernelcore and movablecore is specified,
2110 then kernelcore will be at *least* the specified
2111 value but may be more. If movablecore on its own
2112 is specified, the administrator must be careful
2113 that the amount of memory usable for all allocations
2116 movable_node [KNL,X86] Boot-time switch to enable the effects
2117 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2119 MTD_Partition= [MTD]
2120 Format: <name>,<region-number>,<size>,<offset>
2122 MTD_Region= [MTD] Format:
2123 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2126 See drivers/mtd/cmdlinepart.c.
2128 multitce=off [PPC] This parameter disables the use of the pSeries
2129 firmware feature for updating multiple TCE entries
2132 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2134 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2136 boundary - index of last SLC block on Flex-OneNAND.
2137 The remaining blocks are configured as MLC blocks.
2138 lock - Configure if Flex-OneNAND boundary should be locked.
2139 Once locked, the boundary cannot be changed.
2140 1 indicates lock status, 0 indicates unlock status.
2143 ARM/S3C2412 JIVE boot control
2145 See arch/arm/mach-s3c2412/mach-jive.c
2147 mtouchusb.raw_coordinates=
2148 [HW] Make the MicroTouch USB driver use raw coordinates
2149 ('y', default) or cooked coordinates ('n')
2151 mtrr_chunk_size=nn[KMG] [X86]
2152 used for mtrr cleanup. It is largest continuous chunk
2153 that could hold holes aka. UC entries.
2155 mtrr_gran_size=nn[KMG] [X86]
2156 Used for mtrr cleanup. It is granularity of mtrr block.
2158 Large value could prevent small alignment from
2161 mtrr_spare_reg_nr=n [X86]
2163 Range: 0,7 : spare reg number
2165 Used for mtrr cleanup. It is spare mtrr entries number.
2166 Set to 2 or more if your graphical card needs more.
2168 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2170 netdev= [NET] Network devices parameters
2171 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2172 Note that mem_start is often overloaded to mean
2173 something different and driver-specific.
2174 This usage is only documented in each driver source
2178 [NETFILTER] Enable connection tracking flow accounting
2179 0 to disable accounting
2180 1 to enable accounting
2183 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2184 See Documentation/filesystems/nfs/nfsroot.txt.
2186 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2187 See Documentation/filesystems/nfs/nfsroot.txt.
2189 nfsrootdebug [NFS] enable nfsroot debugging messages.
2190 See Documentation/filesystems/nfs/nfsroot.txt.
2192 nfs.callback_tcpport=
2193 [NFS] set the TCP port on which the NFSv4 callback
2194 channel should listen.
2197 [NFS] sets the pathname to the program which is used
2198 to update the NFS client cache entries.
2200 nfs.cache_getent_timeout=
2201 [NFS] sets the timeout after which an attempt to
2202 update a cache entry is deemed to have failed.
2204 nfs.idmap_cache_timeout=
2205 [NFS] set the maximum lifetime for idmapper cache
2209 [NFS] enable 64-bit inode numbers.
2210 If zero, the NFS client will fake up a 32-bit inode
2211 number for the readdir() and stat() syscalls instead
2212 of returning the full 64-bit number.
2213 The default is to return 64-bit inode numbers.
2215 nfs.max_session_slots=
2216 [NFSv4.1] Sets the maximum number of session slots
2217 the client will attempt to negotiate with the server.
2218 This limits the number of simultaneous RPC requests
2219 that the client can send to the NFSv4.1 server.
2220 Note that there is little point in setting this
2221 value higher than the max_tcp_slot_table_limit.
2223 nfs.nfs4_disable_idmapping=
2224 [NFSv4] When set to the default of '1', this option
2225 ensures that both the RPC level authentication
2226 scheme and the NFS level operations agree to use
2227 numeric uids/gids if the mount is using the
2228 'sec=sys' security flavour. In effect it is
2229 disabling idmapping, which can make migration from
2230 legacy NFSv2/v3 systems to NFSv4 easier.
2231 Servers that do not support this mode of operation
2232 will be autodetected by the client, and it will fall
2233 back to using the idmapper.
2234 To turn off this behaviour, set the value to '0'.
2236 [NFS4] Specify an additional fixed unique ident-
2237 ification string that NFSv4 clients can insert into
2238 their nfs_client_id4 string. This is typically a
2239 UUID that is generated at system install time.
2241 nfs.send_implementation_id =
2242 [NFSv4.1] Send client implementation identification
2243 information in exchange_id requests.
2244 If zero, no implementation identification information
2246 The default is to send the implementation identification
2249 nfs.recover_lost_locks =
2250 [NFSv4] Attempt to recover locks that were lost due
2251 to a lease timeout on the server. Please note that
2252 doing this risks data corruption, since there are
2253 no guarantees that the file will remain unchanged
2254 after the locks are lost.
2255 If you want to enable the kernel legacy behaviour of
2256 attempting to recover these locks, then set this
2258 The default parameter value of '0' causes the kernel
2259 not to attempt recovery of lost locks.
2261 nfsd.nfs4_disable_idmapping=
2262 [NFSv4] When set to the default of '1', the NFSv4
2263 server will return only numeric uids and gids to
2264 clients using auth_sys, and will accept numeric uids
2265 and gids from such clients. This is intended to ease
2266 migration from NFSv2/v3.
2268 objlayoutdriver.osd_login_prog=
2269 [NFS] [OBJLAYOUT] sets the pathname to the program which
2270 is used to automatically discover and login into new
2271 osd-targets. Please see:
2272 Documentation/filesystems/pnfs.txt for more explanations
2274 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2275 when a NMI is triggered.
2276 Format: [state][,regs][,debounce][,die]
2278 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2279 Format: [panic,][nopanic,][num]
2281 0 - turn nmi_watchdog off
2282 1 - turn nmi_watchdog on
2283 When panic is specified, panic when an NMI watchdog
2284 timeout occurs (or 'nopanic' to override the opposite
2286 This is useful when you use a panic=... timeout and
2287 need the box quickly up again.
2289 netpoll.carrier_timeout=
2290 [NET] Specifies amount of time (in seconds) that
2291 netpoll should wait for a carrier. By default netpoll
2294 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2295 emulation library even if a 387 maths coprocessor
2299 [HW] Never suspend the console
2300 Disable suspending of consoles during suspend and
2301 hibernate operations. Once disabled, debugging
2302 messages can reach various consoles while the rest
2303 of the system is being put to sleep (ie, while
2304 debugging driver suspend/resume hooks). This may
2305 not work reliably with all consoles, but is known
2306 to work with serial and VGA consoles.
2307 To facilitate more flexible debugging, we also add
2308 console_suspend, a printk module parameter to control
2309 it. Users could use console_suspend (usually
2310 /sys/module/printk/parameters/console_suspend) to
2311 turn on/off it dynamically.
2313 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2314 caches in the slab allocator. Saves per-node memory,
2315 but will impact performance.
2319 noapic [SMP,APIC] Tells the kernel to not make use of any
2320 IOAPICs that may be present in the system.
2322 noautogroup Disable scheduler automatic task group creation.
2324 nobats [PPC] Do not use BATs for mapping kernel lowmem
2325 on "Classic" PPC cores.
2329 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2331 nodelayacct [KNL] Disable per-task delay accounting
2333 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2335 nodsp [SH] Disable hardware DSP at boot time.
2337 noefi Disable EFI runtime services support.
2342 On X86-32 available only on PAE configured kernels.
2343 noexec=on: enable non-executable mappings (default)
2344 noexec=off: disable non-executable mappings
2347 Disable SMAP (Supervisor Mode Access Prevention)
2348 even if it is supported by processor.
2351 Disable SMEP (Supervisor Mode Execution Prevention)
2352 even if it is supported by processor.
2355 This affects only 32-bit executables.
2356 noexec32=on: enable non-executable mappings (default)
2357 read doesn't imply executable mappings
2358 noexec32=off: disable non-executable mappings
2359 read implies executable mappings
2361 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2363 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2364 register save and restore. The kernel will only save
2365 legacy floating-point registers on task switch.
2367 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2369 noxsave [BUGS=X86] Disables x86 extended register state save
2370 and restore using xsave. The kernel will fallback to
2371 enabling legacy floating-point and sse state.
2373 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2374 register states. The kernel will fall back to use
2375 xsave to save the states. By using this parameter,
2376 performance of saving the states is degraded because
2377 xsave doesn't support modified optimization while
2378 xsaveopt supports it on xsaveopt enabled systems.
2380 noxsaves [X86] Disables xsaves and xrstors used in saving and
2381 restoring x86 extended register state in compacted
2382 form of xsave area. The kernel will fall back to use
2383 xsaveopt and xrstor to save and restore the states
2384 in standard form of xsave area. By using this
2385 parameter, xsave area per process might occupy more
2386 memory on xsaves enabled systems.
2388 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2389 wfi(ARM) instruction doesn't work correctly and not to
2390 use it. This is also useful when using JTAG debugger.
2392 no_file_caps Tells the kernel not to honor file capabilities. The
2393 only way then for a file to be executed with privilege
2394 is to be setuid root or executed by root.
2396 nohalt [IA-64] Tells the kernel not to use the power saving
2397 function PAL_HALT_LIGHT when idle. This increases
2398 power-consumption. On the positive side, it reduces
2399 interrupt wake-up latency, which may improve performance
2400 in certain environments such as networked servers or
2403 nohibernate [HIBERNATION] Disable hibernation and resume.
2405 nohz= [KNL] Boottime enable/disable dynamic ticks
2406 Valid arguments: on, off
2409 nohz_full= [KNL,BOOT]
2410 In kernels built with CONFIG_NO_HZ_FULL=y, set
2411 the specified list of CPUs whose tick will be stopped
2412 whenever possible. The boot CPU will be forced outside
2413 the range to maintain the timekeeping.
2414 The CPUs in this range must also be included in the
2417 noiotrap [SH] Disables trapped I/O port accesses.
2419 noirqdebug [X86-32] Disables the code which attempts to detect and
2420 disable unhandled interrupt sources.
2422 no_timer_check [X86,APIC] Disables the code which tests for
2423 broken timer IRQ sources.
2425 noisapnp [ISAPNP] Disables ISA PnP code.
2427 noinitrd [RAM] Tells the kernel not to load any configured
2430 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2432 [Deprecated - use intremap=off]
2436 nojitter [IA-64] Disables jitter checking for ITC timers.
2438 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2440 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2443 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2444 steal time is computed, but won't influence scheduler
2447 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2449 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2451 noltlbs [PPC] Do not use large page/tlb entries for kernel
2452 lowmem mapping on PPC40x.
2454 nomca [IA-64] Disable machine check abort handling
2456 nomce [X86-32] Machine Check Exception
2458 nomfgpt [X86-32] Disable Multi-Function General Purpose
2459 Timer usage (for AMD Geode machines).
2461 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2462 shutdown the other cpus. Instead use the REBOOT_VECTOR
2465 nomodule Disable module load
2467 nopat [X86] Disable PAT (page attribute table extension of
2468 pagetables) support.
2470 norandmaps Don't use address space randomization. Equivalent to
2471 echo 0 > /proc/sys/kernel/randomize_va_space
2473 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2475 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2476 with UP alternatives
2478 nordrand [X86] Disable kernel use of the RDRAND and
2479 RDSEED instructions even if they are supported
2480 by the processor. RDRAND and RDSEED are still
2481 available to user space applications.
2483 noresume [SWSUSP] Disables resume and restores original swap
2486 no-scroll [VGA] Disables scrollback.
2487 This is required for the Braillex ib80-piezo Braille
2488 reader made by F.H. Papenmeier (Germany).
2492 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2494 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2495 and disable the IO APIC. legacy for "maxcpus=0".
2497 nosoftlockup [KNL] Disable the soft-lockup detector.
2499 nosync [HW,M68K] Disables sync negotiation for all devices.
2501 notsc [BUGS=X86-32] Disable Time Stamp Counter
2503 nousb [USB] Disable the USB subsystem
2505 nowatchdog [KNL] Disable both lockup detectors, i.e.
2506 soft-lockup and NMI watchdog (hard-lockup).
2510 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2512 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2513 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2514 Some features depend on CPU0. Known dependencies are:
2515 1. Resume from suspend/hibernate depends on CPU0.
2516 Suspend/hibernate will fail if CPU0 is offline and you
2517 need to online CPU0 before suspend/hibernate.
2518 2. PIC interrupts also depend on CPU0. CPU0 can't be
2519 removed if a PIC interrupt is detected.
2520 It's said poweroff/reboot may depend on CPU0 on some
2521 machines although I haven't seen such issues so far
2522 after CPU0 is offline on a few tested machines.
2523 If the dependencies are under your control, you can
2524 turn on cpu0_hotplug.
2526 nptcg= [IA-64] Override max number of concurrent global TLB
2527 purges which is reported from either PAL_VM_SUMMARY or
2530 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2531 could support. nr_cpus=n : n >= 1 limits the kernel to
2532 supporting 'n' processors. Later in runtime you can not
2533 use hotplug cpu feature to put more cpu back to online.
2534 just like you compile the kernel NR_CPUS=n
2536 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2538 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2539 Allowed values are enable and disable
2541 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2542 one of ['zone', 'node', 'default'] can be specified
2543 This can be set from sysctl after boot.
2544 See Documentation/sysctl/vm.txt for details.
2546 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2547 See Documentation/debugging-via-ohci1394.txt for more
2550 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2551 Rather than timing out after 20 ms if an EC
2552 command is not properly ACKed, override the length
2553 of the timeout. We have interrupts disabled while
2554 waiting for the ACK, so if this is set too high
2555 interrupts *may* be lost!
2557 omap_mux= [OMAP] Override bootloader pin multiplexing.
2558 Format: <mux_mode0.mode_name=value>...
2559 For example, to override I2C bus2:
2560 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2562 oprofile.timer= [HW]
2563 Use timer interrupt instead of performance counters
2565 oprofile.cpu_type= Force an oprofile cpu type
2566 This might be useful if you have an older oprofile
2567 userland or if you want common events.
2568 Format: { arch_perfmon }
2569 arch_perfmon: [X86] Force use of architectural
2570 perfmon on Intel CPUs instead of the
2571 CPU specific event set.
2572 timer: [X86] Force use of architectural NMI
2573 timer mode (see also oprofile.timer
2574 for generic hr timer mode)
2575 [s390] Force legacy basic mode sampling
2576 (report cpu_type "timer")
2578 oops=panic Always panic on oopses. Default is to just kill the
2579 process, but there is a small probability of
2580 deadlocking the machine.
2581 This will also cause panics on machine check exceptions.
2582 Useful together with panic=30 to trigger a reboot.
2585 See Documentation/sound/oss/oss-parameters.txt
2587 page_owner= [KNL] Boot-time page_owner enabling option.
2588 Storage of the information about who allocated
2589 each page is disabled in default. With this switch,
2591 on: enable the feature
2593 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2594 timeout > 0: seconds before rebooting
2595 timeout = 0: wait forever
2596 timeout < 0: reboot immediately
2599 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2602 crash_kexec_post_notifiers
2603 Run kdump after running panic-notifiers and dumping
2604 kmsg. This only for the users who doubt kdump always
2605 succeeds in any situation.
2606 Note that this also increases risks of kdump failure,
2607 because some panic notifiers can make the crashed
2608 kernel more unstable.
2610 parkbd.port= [HW] Parallel port number the keyboard adapter is
2611 connected to, default is 0.
2613 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2614 0 for XT, 1 for AT (default is AT).
2617 parport= [HW,PPT] Specify parallel ports. 0 disables.
2618 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2619 Use 'auto' to force the driver to use any
2620 IRQ/DMA settings detected (the default is to
2621 ignore detected IRQ/DMA settings because of
2622 possible conflicts). You can specify the base
2623 address, IRQ, and DMA settings; IRQ and DMA
2624 should be numbers, or 'auto' (for using detected
2625 settings on that particular port), or 'nofifo'
2626 (to avoid using a FIFO even if it is detected).
2627 Parallel ports are assigned in the order they
2628 are specified on the command line, starting
2631 parport_init_mode= [HW,PPT]
2632 Configure VIA parallel port to operate in
2633 a specific mode. This is necessary on Pegasos
2634 computer where firmware has no options for setting
2635 up parallel port mode and sets it to spp.
2636 Currently this function knows 686a and 8231 chips.
2637 Format: [spp|ps2|epp|ecp|ecpepp]
2640 Halt all CPUs after the first oops has been printed for
2641 the specified number of seconds. This is to be used if
2642 your oopses keep scrolling off the screen.
2647 See header of drivers/block/paride/pcd.c.
2648 See also Documentation/blockdev/paride.txt.
2650 pci=option[,option...] [PCI] various PCI subsystem options:
2651 earlydump [X86] dump PCI config space before the kernel
2653 off [X86] don't probe for the PCI bus
2654 bios [X86-32] force use of PCI BIOS, don't access
2655 the hardware directly. Use this if your machine
2656 has a non-standard PCI host bridge.
2657 nobios [X86-32] disallow use of PCI BIOS, only direct
2658 hardware access methods are allowed. Use this
2659 if you experience crashes upon bootup and you
2660 suspect they are caused by the BIOS.
2661 conf1 [X86] Force use of PCI Configuration
2663 conf2 [X86] Force use of PCI Configuration
2665 noaer [PCIE] If the PCIEAER kernel config parameter is
2666 enabled, this kernel boot option can be used to
2667 disable the use of PCIE advanced error reporting.
2668 nodomains [PCI] Disable support for multiple PCI
2669 root domains (aka PCI segments, in ACPI-speak).
2670 nommconf [X86] Disable use of MMCONFIG for PCI
2672 check_enable_amd_mmconf [X86] check for and enable
2673 properly configured MMIO access to PCI
2674 config space on AMD family 10h CPU
2675 nomsi [MSI] If the PCI_MSI kernel config parameter is
2676 enabled, this kernel boot option can be used to
2677 disable the use of MSI interrupts system-wide.
2678 noioapicquirk [APIC] Disable all boot interrupt quirks.
2679 Safety option to keep boot IRQs enabled. This
2680 should never be necessary.
2681 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2682 primary IO-APIC for bridges that cannot disable
2683 boot IRQs. This fixes a source of spurious IRQs
2684 when the system masks IRQs.
2685 noioapicreroute [APIC] Disable workaround that uses the
2686 boot IRQ equivalent of an IRQ that connects to
2687 a chipset where boot IRQs cannot be disabled.
2688 The opposite of ioapicreroute.
2689 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2690 routing table. These calls are known to be buggy
2691 on several machines and they hang the machine
2692 when used, but on other computers it's the only
2693 way to get the interrupt routing table. Try
2694 this option if the kernel is unable to allocate
2695 IRQs or discover secondary PCI buses on your
2697 rom [X86] Assign address space to expansion ROMs.
2698 Use with caution as certain devices share
2699 address decoders between ROMs and other
2701 norom [X86] Do not assign address space to
2702 expansion ROMs that do not already have
2703 BIOS assigned address ranges.
2704 nobar [X86] Do not assign address space to the
2705 BARs that weren't assigned by the BIOS.
2706 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2707 assigned automatically to PCI devices. You can
2708 make the kernel exclude IRQs of your ISA cards
2710 pirqaddr=0xAAAAA [X86] Specify the physical address
2711 of the PIRQ table (normally generated
2712 by the BIOS) if it is outside the
2713 F0000h-100000h range.
2714 lastbus=N [X86] Scan all buses thru bus #N. Can be
2715 useful if the kernel is unable to find your
2716 secondary buses and you want to tell it
2717 explicitly which ones they are.
2718 assign-busses [X86] Always assign all PCI bus
2719 numbers ourselves, overriding
2720 whatever the firmware may have done.
2721 usepirqmask [X86] Honor the possible IRQ mask stored
2722 in the BIOS $PIR table. This is needed on
2723 some systems with broken BIOSes, notably
2724 some HP Pavilion N5400 and Omnibook XE3
2725 notebooks. This will have no effect if ACPI
2726 IRQ routing is enabled.
2727 noacpi [X86] Do not use ACPI for IRQ routing
2728 or for PCI scanning.
2729 use_crs [X86] Use PCI host bridge window information
2730 from ACPI. On BIOSes from 2008 or later, this
2731 is enabled by default. If you need to use this,
2732 please report a bug.
2733 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2734 If you need to use this, please report a bug.
2735 routeirq Do IRQ routing for all PCI devices.
2736 This is normally done in pci_enable_device(),
2737 so this option is a temporary workaround
2738 for broken drivers that don't call it.
2739 skip_isa_align [X86] do not align io start addr, so can
2740 handle more pci cards
2741 firmware [ARM] Do not re-enumerate the bus but instead
2742 just use the configuration from the
2743 bootloader. This is currently used on
2744 IXP2000 systems where the bus has to be
2745 configured a certain way for adjunct CPUs.
2746 noearly [X86] Don't do any early type 1 scanning.
2747 This might help on some broken boards which
2748 machine check when some devices' config space
2749 is read. But various workarounds are disabled
2750 and some IOMMU drivers will not work.
2751 bfsort Sort PCI devices into breadth-first order.
2752 This sorting is done to get a device
2753 order compatible with older (<= 2.4) kernels.
2754 nobfsort Don't sort PCI devices into breadth-first order.
2755 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2756 tuning and use the BIOS-configured MPS defaults.
2757 pcie_bus_safe Set every device's MPS to the largest value
2758 supported by all devices below the root complex.
2759 pcie_bus_perf Set device MPS to the largest allowable MPS
2760 based on its parent bus. Also set MRRS (Max
2761 Read Request Size) to the largest supported
2762 value (no larger than the MPS that the device
2763 or bus can support) for best performance.
2764 pcie_bus_peer2peer Set every device's MPS to 128B, which
2765 every device is guaranteed to support. This
2766 configuration allows peer-to-peer DMA between
2767 any pair of devices, possibly at the cost of
2768 reduced performance. This also guarantees
2769 that hot-added devices will work.
2770 cbiosize=nn[KMG] The fixed amount of bus space which is
2771 reserved for the CardBus bridge's IO window.
2772 The default value is 256 bytes.
2773 cbmemsize=nn[KMG] The fixed amount of bus space which is
2774 reserved for the CardBus bridge's memory
2775 window. The default value is 64 megabytes.
2778 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2779 Specifies alignment and device to reassign
2780 aligned memory resources.
2781 If <order of align> is not specified,
2782 PAGE_SIZE is used as alignment.
2783 PCI-PCI bridge can be specified, if resource
2784 windows need to be expanded.
2785 ecrc= Enable/disable PCIe ECRC (transaction layer
2786 end-to-end CRC checking).
2787 bios: Use BIOS/firmware settings. This is the
2791 hpiosize=nn[KMG] The fixed amount of bus space which is
2792 reserved for hotplug bridge's IO window.
2793 Default size is 256 bytes.
2794 hpmemsize=nn[KMG] The fixed amount of bus space which is
2795 reserved for hotplug bridge's memory window.
2796 Default size is 2 megabytes.
2797 realloc= Enable/disable reallocating PCI bridge resources
2798 if allocations done by BIOS are too small to
2799 accommodate resources required by all child
2801 off: Turn realloc off
2803 realloc same as realloc=on
2804 noari do not use PCIe ARI.
2805 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2806 only look for one device below a PCIe downstream
2809 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2812 force Enable ASPM even on devices that claim not to support it.
2813 WARNING: Forcing ASPM on may cause system lockups.
2815 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2816 nomsi Do not use MSI for PCI Express Native Hotplug (this
2817 makes all PCIe ports use INTx for hotplug services).
2819 pcie_ports= [PCIE] PCIe ports handling:
2820 auto Ask the BIOS whether or not to use native PCIe services
2821 associated with PCIe ports (PME, hot-plug, AER). Use
2822 them only if that is allowed by the BIOS.
2823 native Use native PCIe services associated with PCIe ports
2825 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2828 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2829 nomsi Do not use MSI for native PCIe PME signaling (this makes
2830 all PCIe root ports use INTx for all services).
2832 pcmv= [HW,PCMCIA] BadgePAD 4
2836 Keep all power-domains already enabled by bootloader on,
2837 even if no driver has claimed them. This is useful
2838 for debug and development, but should not be
2839 needed on a platform with proper driver support.
2842 See Documentation/blockdev/paride.txt.
2844 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2847 See arch/parisc/kernel/pdc_chassis.c
2849 percpu_alloc= Select which percpu first chunk allocator to use.
2850 Currently supported values are "embed" and "page".
2851 Archs may support subset or none of the selections.
2852 See comments in mm/percpu.c for details on each
2853 allocator. This parameter is primarily for debugging
2854 and performance comparison.
2857 See Documentation/blockdev/paride.txt.
2860 See Documentation/blockdev/paride.txt.
2862 pirq= [SMP,APIC] Manual mp-table setup
2863 See Documentation/x86/i386/IO-APIC.txt.
2865 plip= [PPT,NET] Parallel port network link
2866 Format: { parport<nr> | timid | 0 }
2867 See also Documentation/parport.txt.
2869 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2870 Override pmtimer IOPort with a hex value.
2874 Enable PNP debug messages (depends on the
2875 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2876 via /sys/module/pnp/parameters/debug. We always show
2877 current resource usage; turning this on also shows
2878 possible settings and some assignment information.
2884 { on | off | curr | res | no-curr | no-res }
2887 [ISAPNP] Exclude IRQs for the autoconfiguration
2890 [ISAPNP] Exclude DMAs for the autoconfiguration
2892 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2893 Ranges are in pairs (I/O port base and size).
2896 [ISAPNP] Exclude memory regions for the
2898 Ranges are in pairs (memory base and size).
2900 ports= [IP_VS_FTP] IPVS ftp helper module
2902 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2904 Format: <port>,<port>....
2906 print-fatal-signals=
2907 [KNL] debug: print fatal signals
2909 If enabled, warn about various signal handling
2910 related application anomalies: too many signals,
2911 too many POSIX.1 timers, fatal signals causing a
2914 If you hit the warning due to signal overflow,
2915 you might want to try "ulimit -i unlimited".
2919 printk.always_kmsg_dump=
2920 Trigger kmsg_dump for cases other than kernel oops or
2922 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2925 printk.time= Show timing data prefixed to each printk message line
2926 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2928 processor.max_cstate= [HW,ACPI]
2929 Limit processor to maximum C-state
2930 max_cstate=9 overrides any DMI blacklist limit.
2932 processor.nocst [HW,ACPI]
2933 Ignore the _CST method to determine C-states,
2934 instead using the legacy FADT method
2936 profile= [KNL] Enable kernel profiling via /proc/profile
2937 Format: [schedule,]<number>
2938 Param: "schedule" - profile schedule points.
2939 Param: <number> - step/bucket size as a power of 2 for
2940 statistical time based profiling.
2941 Param: "sleep" - profile D-state sleeping (millisecs).
2942 Requires CONFIG_SCHEDSTATS
2943 Param: "kvm" - profile VM exits.
2945 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2947 See Documentation/blockdev/ramdisk.txt.
2949 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2950 probe for; one of (bare|imps|exps|lifebook|any).
2951 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2953 psmouse.resetafter= [HW,MOUSE]
2954 Try to reset the device after so many bad packets
2957 [HW,MOUSE] Set desired mouse resolution, in dpi.
2958 psmouse.smartscroll=
2959 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2960 0 = disabled, 1 = enabled (default).
2962 pstore.backend= Specify the name of the pstore backend to use
2965 See Documentation/blockdev/paride.txt.
2968 [KNL] Number of legacy pty's. Overwrites compiled-in
2971 quiet [KNL] Disable most log messages
2976 See Documentation/md.txt.
2978 ramdisk_blocksize= [RAM]
2979 See Documentation/blockdev/ramdisk.txt.
2981 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2982 See Documentation/blockdev/ramdisk.txt.
2985 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2986 the specified list of CPUs to be no-callback CPUs.
2987 Invocation of these CPUs' RCU callbacks will
2988 be offloaded to "rcuox/N" kthreads created for
2989 that purpose, where "x" is "b" for RCU-bh, "p"
2990 for RCU-preempt, and "s" for RCU-sched, and "N"
2991 is the CPU number. This reduces OS jitter on the
2992 offloaded CPUs, which can be useful for HPC and
2993 real-time workloads. It can also improve energy
2994 efficiency for asymmetric multiprocessors.
2997 Rather than requiring that offloaded CPUs
2998 (specified by rcu_nocbs= above) explicitly
2999 awaken the corresponding "rcuoN" kthreads,
3000 make these kthreads poll for callbacks.
3001 This improves the real-time response for the
3002 offloaded CPUs by relieving them of the need to
3003 wake up the corresponding kthread, but degrades
3004 energy efficiency by requiring that the kthreads
3005 periodically wake up to do the polling.
3007 rcutree.blimit= [KNL]
3008 Set maximum number of finished RCU callbacks to
3009 process in one batch.
3011 rcutree.dump_tree= [KNL]
3012 Dump the structure of the rcu_node combining tree
3013 out at early boot. This is used for diagnostic
3014 purposes, to verify correct tree setup.
3016 rcutree.gp_cleanup_delay= [KNL]
3017 Set the number of jiffies to delay each step of
3018 RCU grace-period cleanup. This only has effect
3019 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3021 rcutree.gp_init_delay= [KNL]
3022 Set the number of jiffies to delay each step of
3023 RCU grace-period initialization. This only has
3024 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3027 rcutree.gp_preinit_delay= [KNL]
3028 Set the number of jiffies to delay each step of
3029 RCU grace-period pre-initialization, that is,
3030 the propagation of recent CPU-hotplug changes up
3031 the rcu_node combining tree. This only has effect
3032 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3034 rcutree.rcu_fanout_exact= [KNL]
3035 Disable autobalancing of the rcu_node combining
3036 tree. This is used by rcutorture, and might
3037 possibly be useful for architectures having high
3038 cache-to-cache transfer latencies.
3040 rcutree.rcu_fanout_leaf= [KNL]
3041 Increase the number of CPUs assigned to each
3042 leaf rcu_node structure. Useful for very large
3045 rcutree.jiffies_till_sched_qs= [KNL]
3046 Set required age in jiffies for a
3047 given grace period before RCU starts
3048 soliciting quiescent-state help from
3049 rcu_note_context_switch().
3051 rcutree.jiffies_till_first_fqs= [KNL]
3052 Set delay from grace-period initialization to
3053 first attempt to force quiescent states.
3054 Units are jiffies, minimum value is zero,
3055 and maximum value is HZ.
3057 rcutree.jiffies_till_next_fqs= [KNL]
3058 Set delay between subsequent attempts to force
3059 quiescent states. Units are jiffies, minimum
3060 value is one, and maximum value is HZ.
3062 rcutree.kthread_prio= [KNL,BOOT]
3063 Set the SCHED_FIFO priority of the RCU per-CPU
3064 kthreads (rcuc/N). This value is also used for
3065 the priority of the RCU boost threads (rcub/N)
3066 and for the RCU grace-period kthreads (rcu_bh,
3067 rcu_preempt, and rcu_sched). If RCU_BOOST is
3068 set, valid values are 1-99 and the default is 1
3069 (the least-favored priority). Otherwise, when
3070 RCU_BOOST is not set, valid values are 0-99 and
3071 the default is zero (non-realtime operation).
3073 rcutree.rcu_nocb_leader_stride= [KNL]
3074 Set the number of NOCB kthread groups, which
3075 defaults to the square root of the number of
3076 CPUs. Larger numbers reduces the wakeup overhead
3077 on the per-CPU grace-period kthreads, but increases
3078 that same overhead on each group's leader.
3080 rcutree.qhimark= [KNL]
3081 Set threshold of queued RCU callbacks beyond which
3082 batch limiting is disabled.
3084 rcutree.qlowmark= [KNL]
3085 Set threshold of queued RCU callbacks below which
3086 batch limiting is re-enabled.
3088 rcutree.rcu_idle_gp_delay= [KNL]
3089 Set wakeup interval for idle CPUs that have
3090 RCU callbacks (RCU_FAST_NO_HZ=y).
3092 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3093 Set wakeup interval for idle CPUs that have
3094 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3095 Lazy RCU callbacks are those which RCU can
3096 prove do nothing more than free memory.
3098 rcutorture.cbflood_inter_holdoff= [KNL]
3099 Set holdoff time (jiffies) between successive
3100 callback-flood tests.
3102 rcutorture.cbflood_intra_holdoff= [KNL]
3103 Set holdoff time (jiffies) between successive
3104 bursts of callbacks within a given callback-flood
3107 rcutorture.cbflood_n_burst= [KNL]
3108 Set the number of bursts making up a given
3109 callback-flood test. Set this to zero to
3110 disable callback-flood testing.
3112 rcutorture.cbflood_n_per_burst= [KNL]
3113 Set the number of callbacks to be registered
3114 in a given burst of a callback-flood test.
3116 rcutorture.fqs_duration= [KNL]
3117 Set duration of force_quiescent_state bursts.
3119 rcutorture.fqs_holdoff= [KNL]
3120 Set holdoff time within force_quiescent_state bursts.
3122 rcutorture.fqs_stutter= [KNL]
3123 Set wait time between force_quiescent_state bursts.
3125 rcutorture.gp_exp= [KNL]
3126 Use expedited update-side primitives.
3128 rcutorture.gp_normal= [KNL]
3129 Use normal (non-expedited) update-side primitives.
3130 If both gp_exp and gp_normal are set, do both.
3131 If neither gp_exp nor gp_normal are set, still
3134 rcutorture.n_barrier_cbs= [KNL]
3135 Set callbacks/threads for rcu_barrier() testing.
3137 rcutorture.nfakewriters= [KNL]
3138 Set number of concurrent RCU writers. These just
3139 stress RCU, they don't participate in the actual
3140 test, hence the "fake".
3142 rcutorture.nreaders= [KNL]
3143 Set number of RCU readers. The value -1 selects
3144 N-1, where N is the number of CPUs. A value
3145 "n" less than -1 selects N-n-2, where N is again
3146 the number of CPUs. For example, -2 selects N
3147 (the number of CPUs), -3 selects N+1, and so on.
3149 rcutorture.object_debug= [KNL]
3150 Enable debug-object double-call_rcu() testing.
3152 rcutorture.onoff_holdoff= [KNL]
3153 Set time (s) after boot for CPU-hotplug testing.
3155 rcutorture.onoff_interval= [KNL]
3156 Set time (s) between CPU-hotplug operations, or
3157 zero to disable CPU-hotplug testing.
3159 rcutorture.torture_runnable= [BOOT]
3160 Start rcutorture running at boot time.
3162 rcutorture.shuffle_interval= [KNL]
3163 Set task-shuffle interval (s). Shuffling tasks
3164 allows some CPUs to go into dyntick-idle mode
3165 during the rcutorture test.
3167 rcutorture.shutdown_secs= [KNL]
3168 Set time (s) after boot system shutdown. This
3169 is useful for hands-off automated testing.
3171 rcutorture.stall_cpu= [KNL]
3172 Duration of CPU stall (s) to test RCU CPU stall
3173 warnings, zero to disable.
3175 rcutorture.stall_cpu_holdoff= [KNL]
3176 Time to wait (s) after boot before inducing stall.
3178 rcutorture.stat_interval= [KNL]
3179 Time (s) between statistics printk()s.
3181 rcutorture.stutter= [KNL]
3182 Time (s) to stutter testing, for example, specifying
3183 five seconds causes the test to run for five seconds,
3184 wait for five seconds, and so on. This tests RCU's
3185 ability to transition abruptly to and from idle.
3187 rcutorture.test_boost= [KNL]
3188 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3189 "Maybe" means test if the RCU implementation
3190 under test support RCU priority boosting.
3192 rcutorture.test_boost_duration= [KNL]
3193 Duration (s) of each individual boost test.
3195 rcutorture.test_boost_interval= [KNL]
3196 Interval (s) between each boost test.
3198 rcutorture.test_no_idle_hz= [KNL]
3199 Test RCU's dyntick-idle handling. See also the
3200 rcutorture.shuffle_interval parameter.
3202 rcutorture.torture_type= [KNL]
3203 Specify the RCU implementation to test.
3205 rcutorture.verbose= [KNL]
3206 Enable additional printk() statements.
3208 rcupdate.rcu_expedited= [KNL]
3209 Use expedited grace-period primitives, for
3210 example, synchronize_rcu_expedited() instead
3211 of synchronize_rcu(). This reduces latency,
3212 but can increase CPU utilization, degrade
3213 real-time latency, and degrade energy efficiency.
3215 rcupdate.rcu_cpu_stall_suppress= [KNL]
3216 Suppress RCU CPU stall warning messages.
3218 rcupdate.rcu_cpu_stall_timeout= [KNL]
3219 Set timeout for RCU CPU stall warning messages.
3221 rcupdate.rcu_task_stall_timeout= [KNL]
3222 Set timeout in jiffies for RCU task stall warning
3223 messages. Disable with a value less than or equal
3226 rcupdate.rcu_self_test= [KNL]
3227 Run the RCU early boot self tests
3229 rcupdate.rcu_self_test_bh= [KNL]
3230 Run the RCU bh early boot self tests
3232 rcupdate.rcu_self_test_sched= [KNL]
3233 Run the RCU sched early boot self tests
3237 Run specified binary instead of /init from the ramdisk,
3238 used for early userspace startup. See initrd.
3241 Format (x86 or x86_64):
3242 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3244 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3246 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3247 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3248 reboot_force is either force or not specified,
3249 reboot_cpu is s[mp]#### with #### being the processor
3250 to be used for rebooting.
3253 [KNL, SMP] Set scheduler's default relax_domain_level.
3254 See Documentation/cgroups/cpusets.txt.
3256 relative_sleep_states=
3257 [SUSPEND] Use sleep state labeling where the deepest
3258 state available other than hibernation is always "mem".
3259 Format: { "0" | "1" }
3260 0 -- Traditional sleep state labels.
3261 1 -- Relative sleep state labels.
3263 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3265 reservetop= [X86-32]
3267 Reserves a hole at the top of the kernel virtual
3272 Set the amount of memory to reserve for BIOS at
3273 the bottom of the address space.
3275 reset_devices [KNL] Force drivers to reset the underlying device
3276 during initialization.
3279 Specify the partition device for software suspend
3281 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3283 resume_offset= [SWSUSP]
3284 Specify the offset from the beginning of the partition
3285 given by "resume=" at which the swap header is located,
3286 in <PAGE_SIZE> units (needed only for swap files).
3287 See Documentation/power/swsusp-and-swap-files.txt
3289 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3290 read the resume files
3292 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3293 Useful for devices that are detected asynchronously
3294 (e.g. USB and MMC devices).
3296 hibernate= [HIBERNATION]
3297 noresume Don't check if there's a hibernation image
3298 present during boot.
3299 nocompress Don't compress/decompress hibernation images.
3300 no Disable hibernation and resume.
3302 retain_initrd [RAM] Keep initrd memory after extraction
3304 rfkill.default_state=
3305 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3306 etc. communication is blocked by default.
3309 rfkill.master_switch_mode=
3310 0 The "airplane mode" button does nothing.
3311 1 The "airplane mode" button toggles between everything
3312 blocked and the previous configuration.
3313 2 The "airplane mode" button toggles between everything
3314 blocked and everything unblocked.
3316 rhash_entries= [KNL,NET]
3317 Set number of hash buckets for route cache
3319 ro [KNL] Mount root device read-only on boot
3321 root= [KNL] Root filesystem
3322 See name_to_dev_t comment in init/do_mounts.c.
3324 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3325 mount the root filesystem
3327 rootflags= [KNL] Set root filesystem mount option string
3329 rootfstype= [KNL] Set root filesystem type
3331 rootwait [KNL] Wait (indefinitely) for root device to show up.
3332 Useful for devices that are detected asynchronously
3333 (e.g. USB and MMC devices).
3335 rproc_mem=nn[KMG][@address]
3336 [KNL,ARM,CMA] Remoteproc physical memory block.
3337 Memory area to be used by remote processor image,
3340 rw [KNL] Mount root device read-write on boot
3342 S [KNL] Run init in single mode
3344 s390_iommu= [HW,S390]
3345 Set s390 IOTLB flushing mode
3347 With strict flushing every unmap operation will result in
3348 an IOTLB flush. Default is lazy flushing before reuse,
3352 See drivers/net/irda/sa1100_ir.c.
3354 sbni= [NET] Granch SBNI12 leased line adapter
3356 sched_debug [KNL] Enables verbose scheduler debug messages.
3358 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3359 xtime_lock contention on larger systems, and/or RCU lock
3360 contention on all systems with CONFIG_MAXSMP set.
3361 Format: { "0" | "1" }
3362 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3364 Note: increases power consumption, thus should only be
3365 enabled if running jitter sensitive (HPC/RT) workloads.
3367 security= [SECURITY] Choose a security module to enable at boot.
3368 If this boot parameter is not specified, only the first
3369 security module asking for security registration will be
3370 loaded. An invalid security module name will be treated
3371 as if no module has been chosen.
3373 selinux= [SELINUX] Disable or enable SELinux at boot time.
3374 Format: { "0" | "1" }
3375 See security/selinux/Kconfig help text.
3378 Default value is set via kernel config option.
3379 If enabled at boot time, /selinux/disable can be used
3380 later to disable prior to initial policy load.
3382 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3383 Format: { "0" | "1" }
3384 See security/apparmor/Kconfig help text
3387 Default value is set via kernel config option.
3389 serialnumber [BUGS=X86-32]
3392 Maximal number of shapers.
3394 show_msr= [x86] show boot-time MSR settings
3395 Format: { <integer> }
3396 Show boot-time (BIOS-initialized) MSR settings.
3397 The parameter means the number of CPUs to show,
3398 for example 1 means boot CPU only.
3406 Disable merging of slabs with similar size. May be
3407 necessary if there is some reason to distinguish
3408 allocs to different slabs. Debug options disable
3409 merging on their own.
3410 For more information see Documentation/vm/slub.txt.
3412 slab_max_order= [MM, SLAB]
3413 Determines the maximum allowed order for slabs.
3414 A high setting may cause OOMs due to memory
3415 fragmentation. Defaults to 1 for systems with
3416 more than 32MB of RAM, 0 otherwise.
3418 slub_debug[=options[,slabs]] [MM, SLUB]
3419 Enabling slub_debug allows one to determine the
3420 culprit if slab objects become corrupted. Enabling
3421 slub_debug can create guard zones around objects and
3422 may poison objects when not in use. Also tracks the
3423 last alloc / free. For more information see
3424 Documentation/vm/slub.txt.
3426 slub_max_order= [MM, SLUB]
3427 Determines the maximum allowed order for slabs.
3428 A high setting may cause OOMs due to memory
3429 fragmentation. For more information see
3430 Documentation/vm/slub.txt.
3432 slub_min_objects= [MM, SLUB]
3433 The minimum number of objects per slab. SLUB will
3434 increase the slab order up to slub_max_order to
3435 generate a sufficiently large slab able to contain
3436 the number of objects indicated. The higher the number
3437 of objects the smaller the overhead of tracking slabs
3438 and the less frequently locks need to be acquired.
3439 For more information see Documentation/vm/slub.txt.
3441 slub_min_order= [MM, SLUB]
3442 Determines the minimum page order for slabs. Must be
3443 lower than slub_max_order.
3444 For more information see Documentation/vm/slub.txt.
3446 slub_nomerge [MM, SLUB]
3447 Same with slab_nomerge. This is supported for legacy.
3448 See slab_nomerge for more information.
3451 Format: <io1>[,<io2>[,...,<io8>]]
3453 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3454 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3455 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3456 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3457 smsc-ircc2.ircc_irq= [HW] IRQ line
3458 smsc-ircc2.ircc_dma= [HW] DMA channel
3459 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3460 0: Toshiba Satellite 1800 (GP data pin select)
3461 1: Fast pin select (default)
3465 [KNL] Should the soft-lockup detector generate panics.
3468 softlockup_all_cpu_backtrace=
3469 [KNL] Should the soft-lockup detector generate
3470 backtraces on all cpus.
3473 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3474 See Documentation/laptops/sonypi.txt
3476 spia_io_base= [HW,MTD]
3482 Enabled the stack tracer on boot up.
3484 stacktrace_filter=[function-list]
3485 [FTRACE] Limit the functions that the stack tracer
3486 will trace at boot up. function-list is a comma separated
3487 list of functions. This list can be changed at run
3488 time by the stack_trace_filter file in the debugfs
3489 tracing directory. Note, this enables stack tracing
3490 and the stacktrace above is not needed.
3494 Set the STI (builtin display/keyboard on the HP-PARISC
3495 machines) console (graphic card) which should be used
3496 as the initial boot-console.
3497 See also comment in drivers/video/console/sticore.c.
3500 See comment in drivers/video/console/sticore.c.
3503 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3505 sunrpc.min_resvport=
3506 sunrpc.max_resvport=
3508 SunRPC servers often require that client requests
3509 originate from a privileged port (i.e. a port in the
3510 range 0 < portnr < 1024).
3511 An administrator who wishes to reserve some of these
3512 ports for other uses may adjust the range that the
3513 kernel's sunrpc client considers to be privileged
3514 using these two parameters to set the minimum and
3515 maximum port values.
3519 Control how the NFS server code allocates CPUs to
3520 service thread pools. Depending on how many NICs
3521 you have and where their interrupts are bound, this
3522 option will affect which CPUs will do NFS serving.
3523 Note: this parameter cannot be changed while the
3524 NFS server is running.
3526 auto the server chooses an appropriate mode
3527 automatically using heuristics
3528 global a single global pool contains all CPUs
3529 percpu one pool for each CPU
3530 pernode one pool for each NUMA node (equivalent
3531 to global on non-NUMA machines)
3533 sunrpc.tcp_slot_table_entries=
3534 sunrpc.udp_slot_table_entries=
3536 Sets the upper limit on the number of simultaneous
3537 RPC calls that can be sent from the client to a
3538 server. Increasing these values may allow you to
3539 improve throughput, but will also increase the
3540 amount of memory reserved for use by the client.
3542 suspend.pm_test_delay=
3544 Sets the number of seconds to remain in a suspend test
3545 mode before resuming the system (see
3546 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3547 is set. Default value is 5.
3550 [KNL] Enable accounting of swap in memory resource
3551 controller if no parameter or 1 is given or disable
3552 it if 0 is given (See Documentation/cgroups/memory.txt)
3554 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3555 Format: { <int> | force }
3556 <int> -- Number of I/O TLB slabs
3557 force -- force using of bounce buffers even if they
3558 wouldn't be automatically used by the kernel
3562 sysfs.deprecated=0|1 [KNL]
3563 Enable/disable old style sysfs layout for old udev
3564 on older distributions. When this option is enabled
3565 very new udev will not work anymore. When this option
3566 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3567 in older udev will not work anymore.
3568 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3569 the kernel configuration.
3571 sysrq_always_enabled
3573 Ignore sysrq setting - this boot parameter will
3574 neutralize any effect of /proc/sys/kernel/sysrq.
3575 Useful for debugging.
3577 tcpmhash_entries= [KNL,NET]
3578 Set the number of tcp_metrics_hash slots.
3579 Default value is 8192 or 16384 depending on total
3580 ram pages. This is used to specify the TCP metrics
3581 cache size. See Documentation/networking/ip-sysctl.txt
3582 "tcp_no_metrics_save" section for more details.
3586 test_suspend= [SUSPEND][,N]
3587 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3588 standby suspend) or "freeze" (for suspend type freeze)
3589 as the system sleep state during system startup with
3590 the optional capability to repeat N number of times.
3591 The system is woken from this state using a
3592 wakeup-capable RTC alarm.
3594 thash_entries= [KNL,NET]
3595 Set number of hash buckets for TCP connection
3597 thermal.act= [HW,ACPI]
3598 -1: disable all active trip points in all thermal zones
3599 <degrees C>: override all lowest active trip points
3601 thermal.crt= [HW,ACPI]
3602 -1: disable all critical trip points in all thermal zones
3603 <degrees C>: override all critical trip points
3605 thermal.nocrt= [HW,ACPI]
3606 Set to disable actions on ACPI thermal zone
3607 critical and hot trip points.
3609 thermal.off= [HW,ACPI]
3610 1: disable ACPI thermal control
3612 thermal.psv= [HW,ACPI]
3613 -1: disable all passive trip points
3614 <degrees C>: override all passive trip points to this
3617 thermal.tzp= [HW,ACPI]
3618 Specify global default ACPI thermal zone polling rate
3619 <deci-seconds>: poll all this frequency
3620 0: no polling (default)
3623 Force threading of all interrupt handlers except those
3624 marked explicitly IRQF_NO_THREAD.
3627 Enable the Transcendent memory driver if built-in.
3629 tmem.cleancache=0|1 [KNL, XEN]
3630 Default is on (1). Disable the usage of the cleancache
3631 API to send anonymous pages to the hypervisor.
3633 tmem.frontswap=0|1 [KNL, XEN]
3634 Default is on (1). Disable the usage of the frontswap
3635 API to send swap pages to the hypervisor. If disabled
3636 the selfballooning and selfshrinking are force disabled.
3638 tmem.selfballooning=0|1 [KNL, XEN]
3639 Default is on (1). Disable the driving of swap pages
3642 tmem.selfshrinking=0|1 [KNL, XEN]
3643 Default is on (1). Partial swapoff that immediately
3644 transfers pages from Xen hypervisor back to the
3645 kernel based on different criteria.
3649 Specify if the kernel should make use of the cpu
3650 topology information if the hardware supports this.
3651 The scheduler will make use of this information and
3652 e.g. base its process migration decisions on it.
3655 topology_updates= [KNL, PPC, NUMA]
3657 Specify if the kernel should ignore (off)
3658 topology updates sent by the hypervisor to this
3663 tpm_suspend_pcr=[HW,TPM]
3664 Format: integer pcr id
3665 Specify that at suspend time, the tpm driver
3666 should extend the specified pcr with zeros,
3667 as a workaround for some chips which fail to
3668 flush the last written pcr on TPM_SaveState.
3669 This will guarantee that all the other pcrs
3672 trace_buf_size=nn[KMG]
3673 [FTRACE] will set tracing buffer size on each cpu.
3675 trace_event=[event-list]
3676 [FTRACE] Set and start specified trace events in order
3677 to facilitate early boot debugging.
3678 See also Documentation/trace/events.txt
3680 trace_options=[option-list]
3681 [FTRACE] Enable or disable tracer options at boot.
3682 The option-list is a comma delimited list of options
3683 that can be enabled or disabled just as if you were
3684 to echo the option name into
3686 /sys/kernel/debug/tracing/trace_options
3688 For example, to enable stacktrace option (to dump the
3689 stack trace of each event), add to the command line:
3691 trace_options=stacktrace
3693 See also Documentation/trace/ftrace.txt "trace options"
3697 Have the tracepoints sent to printk as well as the
3698 tracing ring buffer. This is useful for early boot up
3699 where the system hangs or reboots and does not give the
3700 option for reading the tracing buffer or performing a
3701 ftrace_dump_on_oops.
3703 To turn off having tracepoints sent to printk,
3704 echo 0 > /proc/sys/kernel/tracepoint_printk
3705 Note, echoing 1 into this file without the
3706 tracepoint_printk kernel cmdline option has no effect.
3710 Having tracepoints sent to printk() and activating high
3711 frequency tracepoints such as irq or sched, can cause
3712 the system to live lock.
3715 [FTRACE] enable this option to disable tracing when a
3716 warning is hit. This turns off "tracing_on". Tracing can
3717 be enabled again by echoing '1' into the "tracing_on"
3718 file located in /sys/kernel/debug/tracing/
3720 This option is useful, as it disables the trace before
3721 the WARNING dump is called, which prevents the trace to
3722 be filled with content caused by the warning output.
3724 This option can also be set at run time via the sysctl
3725 option: kernel/traceoff_on_warning
3727 transparent_hugepage=
3729 Format: [always|madvise|never]
3730 Can be used to control the default behavior of the system
3731 with respect to transparent hugepages.
3732 See Documentation/vm/transhuge.txt for more details.
3734 tsc= Disable clocksource stability checks for TSC.
3736 [x86] reliable: mark tsc clocksource as reliable, this
3737 disables clocksource verification at runtime, as well
3738 as the stability checks done at bootup. Used to enable
3739 high-resolution timer mode on older hardware, and in
3740 virtualized environment.
3741 [x86] noirqtime: Do not use TSC to do irq accounting.
3742 Used to run time disable IRQ_TIME_ACCOUNTING on any
3743 platforms where RDTSC is slow and this accounting
3746 turbografx.map[2|3]= [HW,JOY]
3747 TurboGraFX parallel port interface
3749 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3750 See also Documentation/input/joystick-parport.txt
3752 udbg-immortal [PPC] When debugging early kernel crashes that
3753 happen after console_init() and before a proper
3754 console driver takes over, this boot options might
3755 help "seeing" what's going on.
3757 uhash_entries= [KNL,NET]
3758 Set number of hash buckets for UDP/UDP-Lite connections
3761 [USB] Ignore overcurrent events (default N).
3762 Some badly-designed motherboards generate lots of
3763 bogus events, for ports that aren't wired to
3764 anything. Set this parameter to avoid log spamming.
3765 Note that genuine overcurrent events won't be
3769 [X86] Cause panic on unknown NMI.
3771 usbcore.authorized_default=
3772 [USB] Default USB device authorization:
3773 (default -1 = authorized except for wireless USB,
3774 0 = not authorized, 1 = authorized)
3776 usbcore.autosuspend=
3777 [USB] The autosuspend time delay (in seconds) used
3778 for newly-detected USB devices (default 2). This
3779 is the time required before an idle device will be
3780 autosuspended. Devices for which the delay is set
3781 to a negative value won't be autosuspended at all.
3783 usbcore.usbfs_snoop=
3784 [USB] Set to log all usbfs traffic (default 0 = off).
3786 usbcore.blinkenlights=
3787 [USB] Set to cycle leds on hubs (default 0 = off).
3789 usbcore.old_scheme_first=
3790 [USB] Start with the old device initialization
3791 scheme (default 0 = off).
3793 usbcore.usbfs_memory_mb=
3794 [USB] Memory limit (in MB) for buffers allocated by
3795 usbfs (default = 16, 0 = max = 2047).
3797 usbcore.use_both_schemes=
3798 [USB] Try the other device initialization scheme
3799 if the first one fails (default 1 = enabled).
3801 usbcore.initial_descriptor_timeout=
3802 [USB] Specifies timeout for the initial 64-byte
3803 USB_REQ_GET_DESCRIPTOR request in milliseconds
3804 (default 5000 = 5.0 seconds).
3807 [USBHID] The interval which mice are to be polled at.
3809 usb-storage.delay_use=
3810 [UMS] The delay in seconds before a new device is
3811 scanned for Logical Units (default 1).
3814 [UMS] A list of quirks entries to supplement or
3815 override the built-in unusual_devs list. List
3816 entries are separated by commas. Each entry has
3817 the form VID:PID:Flags where VID and PID are Vendor
3818 and Product ID values (4-digit hex numbers) and
3819 Flags is a set of characters, each corresponding
3820 to a common usb-storage quirk flag as follows:
3821 a = SANE_SENSE (collect more than 18 bytes
3823 b = BAD_SENSE (don't collect more than 18
3824 bytes of sense data);
3825 c = FIX_CAPACITY (decrease the reported
3826 device capacity by one sector);
3827 d = NO_READ_DISC_INFO (don't use
3828 READ_DISC_INFO command);
3829 e = NO_READ_CAPACITY_16 (don't use
3830 READ_CAPACITY_16 command);
3831 f = NO_REPORT_OPCODES (don't use report opcodes
3833 g = MAX_SECTORS_240 (don't transfer more than
3834 240 sectors at a time, uas only);
3835 h = CAPACITY_HEURISTICS (decrease the
3836 reported device capacity by one
3837 sector if the number is odd);
3838 i = IGNORE_DEVICE (don't bind to this
3840 l = NOT_LOCKABLE (don't try to lock and
3841 unlock ejectable media);
3842 m = MAX_SECTORS_64 (don't transfer more
3843 than 64 sectors = 32 KB at a time);
3844 n = INITIAL_READ10 (force a retry of the
3845 initial READ(10) command);
3846 o = CAPACITY_OK (accept the capacity
3847 reported by the device);
3848 p = WRITE_CACHE (the device cache is ON
3850 r = IGNORE_RESIDUE (the device reports
3851 bogus residue values);
3852 s = SINGLE_LUN (the device has only one
3854 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3855 commands, uas only);
3856 u = IGNORE_UAS (don't bind to the uas driver);
3857 w = NO_WP_DETECT (don't test whether the
3858 medium is write-protected).
3859 Example: quirks=0419:aaf5:rl,0421:0433:rc
3861 user_debug= [KNL,ARM]
3863 See arch/arm/Kconfig.debug help text.
3864 1 - undefined instruction events
3866 4 - invalid data aborts
3869 Example: user_debug=31
3872 [X86] Flags controlling user PTE allocations.
3874 nohigh = do not allocate PTE pages in
3875 HIGHMEM regardless of setting
3879 On X86_32, this is an alias for vdso32=. Otherwise:
3881 vdso=1: enable VDSO (the default)
3882 vdso=0: disable VDSO mapping
3884 vdso32= [X86] Control the 32-bit vDSO
3885 vdso32=1: enable 32-bit VDSO
3886 vdso32=0 or vdso32=2: disable 32-bit VDSO
3888 See the help text for CONFIG_COMPAT_VDSO for more
3889 details. If CONFIG_COMPAT_VDSO is set, the default is
3890 vdso32=0; otherwise, the default is vdso32=1.
3892 For compatibility with older kernels, vdso32=2 is an
3895 Try vdso32=0 if you encounter an error that says:
3896 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3899 vector=percpu: enable percpu vector domain
3901 video= [FB] Frame buffer configuration
3902 See Documentation/fb/modedb.txt.
3904 video.brightness_switch_enabled= [0,1]
3905 If set to 1, on receiving an ACPI notify event
3906 generated by hotkey, video driver will adjust brightness
3907 level and then send out the event to user space through
3908 the allocated input device; If set to 0, video driver
3909 will only send out the event without touching backlight
3914 [VMMIO] Memory mapped virtio (platform) device.
3916 <size>@<baseaddr>:<irq>[:<id>]
3918 <size> := size (can use standard suffixes
3920 <baseaddr> := physical base address
3921 <irq> := interrupt number (as passed to
3923 <id> := (optional) platform device id
3925 virtio_mmio.device=1K@0x100b0000:48:7
3927 Can be used multiple times for multiple devices.
3929 vga= [BOOT,X86-32] Select a particular video mode
3930 See Documentation/x86/boot.txt and
3931 Documentation/svga.txt.
3932 Use vga=ask for menu.
3933 This is actually a boot loader parameter; the value is
3934 passed to the kernel using a special protocol.
3936 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3937 size of <nn>. This can be used to increase the
3938 minimum size (128MB on x86). It can also be used to
3939 decrease the size and leave more room for directly
3942 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3945 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3948 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3952 Controls the behavior of vsyscalls (i.e. calls to
3953 fixed addresses of 0xffffffffff600x00 from legacy
3954 code). Most statically-linked binaries and older
3955 versions of glibc use these calls. Because these
3956 functions are at fixed addresses, they make nice
3957 targets for exploits that can control RIP.
3959 emulate [default] Vsyscalls turn into traps and are
3960 emulated reasonably safely.
3962 native Vsyscalls are native syscall instructions.
3963 This is a little bit faster than trapping
3964 and makes a few dynamic recompilers work
3965 better than they would in emulation mode.
3966 It also makes exploits much easier to write.
3968 none Vsyscalls don't work at all. This makes
3969 them quite hard to use for exploits but
3970 might break your system.
3972 vt.color= [VT] Default text color.
3973 Format: 0xYX, X = foreground, Y = background.
3974 Default: 0x07 = light gray on black.
3976 vt.cur_default= [VT] Default cursor shape.
3977 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3978 the parameters of the <Esc>[?A;B;Cc escape sequence;
3979 see VGA-softcursor.txt. Default: 2 = underline.
3981 vt.default_blu= [VT]
3982 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3983 Change the default blue palette of the console.
3984 This is a 16-member array composed of values
3987 vt.default_grn= [VT]
3988 Format: <green0>,<green1>,<green2>,...,<green15>
3989 Change the default green palette of the console.
3990 This is a 16-member array composed of values
3993 vt.default_red= [VT]
3994 Format: <red0>,<red1>,<red2>,...,<red15>
3995 Change the default red palette of the console.
3996 This is a 16-member array composed of values
4002 Set system-wide default UTF-8 mode for all tty's.
4003 Default is 1, i.e. UTF-8 mode is enabled for all
4004 newly opened terminals.
4006 vt.global_cursor_default=
4009 Set system-wide default for whether a cursor
4010 is shown on new VTs. Default is -1,
4011 i.e. cursors will be created by default unless
4012 overridden by individual drivers. 0 will hide
4013 cursors, 1 will display them.
4015 vt.italic= [VT] Default color for italic text; 0-15.
4018 vt.underline= [VT] Default color for underlined text; 0-15.
4021 watchdog timers [HW,WDT] For information on watchdog timers,
4022 see Documentation/watchdog/watchdog-parameters.txt
4023 or other driver-specific files in the
4024 Documentation/watchdog/ directory.
4026 workqueue.disable_numa
4027 By default, all work items queued to unbound
4028 workqueues are affine to the NUMA nodes they're
4029 issued on, which results in better behavior in
4030 general. If NUMA affinity needs to be disabled for
4031 whatever reason, this option can be used. Note
4032 that this also can be controlled per-workqueue for
4033 workqueues visible under /sys/bus/workqueue/.
4035 workqueue.power_efficient
4036 Per-cpu workqueues are generally preferred because
4037 they show better performance thanks to cache
4038 locality; unfortunately, per-cpu workqueues tend to
4039 be more power hungry than unbound workqueues.
4041 Enabling this makes the per-cpu workqueues which
4042 were observed to contribute significantly to power
4043 consumption unbound, leading to measurably lower
4044 power usage at the cost of small performance
4047 The default value of this parameter is determined by
4048 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4050 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4051 default x2apic cluster mode on platforms
4054 x86_intel_mid_timer= [X86-32,APBT]
4055 Choose timer option for x86 Intel MID platform.
4056 Two valid options are apbt timer only and lapic timer
4057 plus one apbt timer for broadcast timer.
4058 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4060 xen_emul_unplug= [HW,X86,XEN]
4061 Unplug Xen emulated devices
4062 Format: [unplug0,][unplug1]
4063 ide-disks -- unplug primary master IDE devices
4064 aux-ide-disks -- unplug non-primary-master IDE devices
4065 nics -- unplug network devices
4066 all -- unplug all emulated devices (NICs and IDE disks)
4067 unnecessary -- unplugging emulated devices is
4068 unnecessary even if the host did not respond to
4070 never -- do not unplug even if version check succeeds
4072 xen_nopvspin [X86,XEN]
4073 Disables the ticketlock slowpath using Xen PV
4077 Disables the PV optimizations forcing the HVM guest to
4078 run as generic HVM guest with no PV drivers.
4080 xirc2ps_cs= [NET,PCMCIA]
4082 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4084 ______________________________________________________________________
4088 Add more DRM drivers.
projects / cascardo / linux.git / blob