1 acpi= [HW,ACPI,X86,ARM64]
2 Advanced Configuration and Power Interface
3 Format: { force | on | off | strict | noirq | rsdt |
5 force -- enable ACPI if default was off
6 on -- enable ACPI but allow fallback to DT [arm64]
7 off -- disable ACPI if default was on
8 noirq -- do not use ACPI for IRQ routing
9 strict -- Be less tolerant of platforms that are not
10 strictly ACPI specification compliant.
11 rsdt -- prefer RSDT over (default) XSDT
12 copy_dsdt -- copy DSDT to memory
13 For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
16 See also Documentation/power/runtime_pm.txt, pci=noacpi
18 acpi_apic_instance= [ACPI, IOAPIC]
20 2: use 2nd APIC table, if available
21 1,0: use 1st APIC table
24 acpi_backlight= [HW,ACPI]
27 If set to vendor, prefer vendor specific driver
28 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
29 of the ACPI video.ko driver.
31 acpi_force_32bit_fadt_addr
32 force FADT to use 32 bit addresses rather than the
33 64 bit X_* addresses. Some firmware have broken 64
34 bit addresses for force ACPI ignore these and use
35 the older legacy 32 bit addresses.
37 acpica_no_return_repair [HW, ACPI]
38 Disable AML predefined validation mechanism
39 This mechanism can repair the evaluation result to make
40 the return objects more ACPI specification compliant.
41 This option is useful for developers to identify the
42 root cause of an AML interpreter issue when the issue
43 has something to do with the repair mechanism.
45 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
46 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
48 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
49 debug output. Bits in debug_layer correspond to a
50 _COMPONENT in an ACPI source file, e.g.,
51 #define _COMPONENT ACPI_PCI_COMPONENT
52 Bits in debug_level correspond to a level in
53 ACPI_DEBUG_PRINT statements, e.g.,
54 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
55 The debug_level mask defaults to "info". See
56 Documentation/acpi/debug.txt for more information about
57 debug layers and levels.
59 Enable processor driver info messages:
60 acpi.debug_layer=0x20000000
61 Enable PCI/PCI interrupt routing info messages:
62 acpi.debug_layer=0x400000
63 Enable AML "Debug" output, i.e., stores to the Debug
64 object while interpreting AML:
65 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
66 Enable all messages related to ACPI hardware:
67 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
69 Some values produce so much output that the system is
70 unusable. The "log_buf_len" parameter may be useful
71 if you need to capture more output.
73 acpi_enforce_resources= [ACPI]
75 Check for resource conflicts between native drivers
76 and ACPI OperationRegions (SystemIO and SystemMemory
77 only). IO ports and memory declared in ACPI might be
78 used by the ACPI subsystem in arbitrary AML code and
79 can interfere with legacy drivers.
80 strict (default): access to resources claimed by ACPI
81 is denied; legacy drivers trying to access reserved
82 resources will fail to bind to device using them.
83 lax: access to resources claimed by ACPI is allowed;
84 legacy drivers trying to access reserved resources
85 will bind successfully but a warning message is logged.
86 no: ACPI OperationRegions are not marked as reserved,
87 no further checks are performed.
89 acpi_force_table_verification [HW,ACPI]
90 Enable table checksum verification during early stage.
91 By default, this is disabled due to x86 early mapping
94 acpi_irq_balance [HW,ACPI]
95 ACPI will balance active IRQs
98 acpi_irq_nobalance [HW,ACPI]
99 ACPI will not move active IRQs (default)
102 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
103 Format: <irq>,<irq>...
105 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
107 Format: <irq>,<irq>...
109 acpi_mask_gpe= [HW,ACPI]
110 Due to the existence of _Lxx/_Exx, some GPEs triggered
111 by unsupported hardware/firmware features can result in
112 GPE floodings that cannot be automatically disabled by
114 This facility can be used to prevent such uncontrolled
117 Support masking of GPEs numbered from 0x00 to 0x7f.
119 acpi_no_auto_serialize [HW,ACPI]
120 Disable auto-serialization of AML methods
121 AML control methods that contain the opcodes to create
122 named objects will be marked as "Serialized" by the
123 auto-serialization feature.
124 This feature is enabled by default.
125 This option allows to turn off the feature.
127 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
130 acpi_no_static_ssdt [HW,ACPI]
131 Disable installation of static SSDTs at early boot time
132 By default, SSDTs contained in the RSDT/XSDT will be
133 installed automatically and they will appear under
134 /sys/firmware/acpi/tables.
135 This option turns off this feature.
136 Note that specifying this option does not affect
137 dynamic table installation which will install SSDT
138 tables to /sys/firmware/acpi/tables/dynamic.
140 acpi_rsdp= [ACPI,EFI,KEXEC]
141 Pass the RSDP address to the kernel, mostly used
142 on machines running EFI runtime service to boot the
143 second kernel for kdump.
145 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
146 Format: To spoof as Windows 98: ="Microsoft Windows"
148 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
149 of 2 which is mandated by ACPI 6) as the supported ACPI
150 specification revision (when using this switch, it may
151 be necessary to carry out a cold reboot _twice_ in a
152 row to make it take effect on the platform firmware).
154 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
155 acpi_osi="string1" # add string1
156 acpi_osi="!string2" # remove string2
157 acpi_osi=!* # remove all strings
158 acpi_osi=! # disable all built-in OS vendor
160 acpi_osi=!! # enable all built-in OS vendor
162 acpi_osi= # disable all strings
164 'acpi_osi=!' can be used in combination with single or
165 multiple 'acpi_osi="string1"' to support specific OS
166 vendor string(s). Note that such command can only
167 affect the default state of the OS vendor strings, thus
168 it cannot affect the default state of the feature group
169 strings and the current state of the OS vendor strings,
170 specifying it multiple times through kernel command line
171 is meaningless. This command is useful when one do not
172 care about the state of the feature group strings which
173 should be controlled by the OSPM.
175 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
176 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
177 can make '_OSI("Windows 2000")' TRUE.
179 'acpi_osi=' cannot be used in combination with other
180 'acpi_osi=' command lines, the _OSI method will not
181 exist in the ACPI namespace. NOTE that such command can
182 only affect the _OSI support state, thus specifying it
183 multiple times through kernel command line is also
186 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
189 'acpi_osi=!*' can be used in combination with single or
190 multiple 'acpi_osi="string1"' to support specific
191 string(s). Note that such command can affect the
192 current state of both the OS vendor strings and the
193 feature group strings, thus specifying it multiple times
194 through kernel command line is meaningful. But it may
195 still not able to affect the final state of a string if
196 there are quirks related to this string. This command
197 is useful when one want to control the state of the
198 feature group strings to debug BIOS issues related to
201 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
202 '_OSI("Module Device")' FALSE.
203 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
204 '_OSI("Module Device")' TRUE.
205 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
207 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
209 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
210 they all will make '_OSI("Windows 2000")' TRUE.
213 Override the pmtimer bug detection: force the kernel
214 to assume that this machine's pmtimer latches its value
215 and always returns good values.
217 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
218 Format: { level | edge | high | low }
220 acpi_skip_timer_override [HW,ACPI]
221 Recognize and ignore IRQ0/pin2 Interrupt Override.
222 For broken nForce2 BIOS resulting in XT-PIC timer.
224 acpi_sleep= [HW,ACPI] Sleep options
225 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
226 old_ordering, nonvs, sci_force_enable }
227 See Documentation/power/video.txt for information on
229 s3_beep is for debugging; it makes the PC's speaker beep
230 as soon as the kernel's real-mode entry point is called.
231 s4_nohwsig prevents ACPI hardware signature from being
232 used during resume from hibernation.
233 old_ordering causes the ACPI 1.0 ordering of the _PTS
234 control method, with respect to putting devices into
235 low power states, to be enforced (the ACPI 2.0 ordering
236 of _PTS is used by default).
237 nonvs prevents the kernel from saving/restoring the
238 ACPI NVS memory during suspend/hibernation and resume.
239 sci_force_enable causes the kernel to set SCI_EN directly
240 on resume from S1/S3 (which is against the ACPI spec,
241 but some broken systems don't work without it).
243 acpi_use_timer_override [HW,ACPI]
244 Use timer override. For some broken Nvidia NF5 boards
245 that require a timer override, but don't have HPET
247 add_efi_memmap [EFI; X86] Include EFI memory map in
248 kernel's map of available physical RAM.
251 { off | try_unsupported }
252 off: disable AGP support
253 try_unsupported: try to drive unsupported chipsets
254 (may crash computer or cause data corruption)
257 See Documentation/sound/alsa/alsa-parameters.txt
260 Allow the default userspace alignment fault handler
261 behaviour to be specified. Bit 0 enables warnings,
262 bit 1 enables fixups, and bit 2 sends a segfault.
264 align_va_addr= [X86-64]
265 Align virtual addresses by clearing slice [14:12] when
266 allocating a VMA at process creation time. This option
267 gives you up to 3% performance improvement on AMD F15h
268 machines (where it is enabled by default) for a
269 CPU-intensive style benchmark, and it can vary highly in
270 a microbenchmark depending on workload and compiler.
272 32: only for 32-bit processes
273 64: only for 64-bit processes
274 on: enable for both 32- and 64-bit processes
275 off: disable for both 32- and 64-bit processes
277 alloc_snapshot [FTRACE]
278 Allocate the ftrace snapshot buffer on boot up when the
279 main buffer is allocated. This is handy if debugging
280 and you need to use tracing_snapshot() on boot up, and
281 do not want to use tracing_snapshot_alloc() as it needs
282 to be done where GFP_KERNEL allocations are allowed.
284 amd_iommu= [HW,X86-64]
285 Pass parameters to the AMD IOMMU driver in the system.
287 fullflush - enable flushing of IO/TLB entries when
288 they are unmapped. Otherwise they are
289 flushed before they will be reused, which
291 off - do not initialize any AMD IOMMU found in
293 force_isolation - Force device isolation for all
294 devices. The IOMMU driver is not
295 allowed anymore to lift isolation
296 requirements as needed. This option
297 does not override iommu=pt
299 amd_iommu_dump= [HW,X86-64]
300 Enable AMD IOMMU driver option to dump the ACPI table
301 for AMD IOMMU. With this option enabled, AMD IOMMU
302 driver will print ACPI tables for AMD IOMMU during
303 IOMMU initialization.
305 amd_iommu_intr= [HW,X86-64]
306 Specifies one of the following AMD IOMMU interrupt
308 legacy - Use legacy interrupt remapping mode.
309 vapic - Use virtual APIC mode, which allows IOMMU
310 to inject interrupts directly into guest.
311 This mode requires kvm-amd.avic=1.
312 (Default when IOMMU HW support is present.)
314 amijoy.map= [HW,JOY] Amiga joystick support
315 Map of devices attached to JOY0DAT and JOY1DAT
317 See also Documentation/input/joystick.txt
319 analog.map= [HW,JOY] Analog joystick and gamepad support
320 Specifies type or capabilities of an analog joystick
321 connected to one of 16 gameports
322 Format: <type1>,<type2>,..<type16>
325 Power management functions (SPARCstation-4/5 + deriv.)
327 Disable APC CPU standby support. SPARCstation-Fox does
328 not play well with APC CPU idle - disable it if you have
329 APC and your system crashes randomly.
331 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
332 Change the output verbosity whilst booting
333 Format: { quiet (default) | verbose | debug }
334 Change the amount of debugging information output
335 when initialising the APIC and IO-APIC components.
337 apic_extnmi= [APIC,X86] External NMI delivery setting
338 Format: { bsp (default) | all | none }
339 bsp: External NMI is delivered only to CPU 0
340 all: External NMIs are broadcast to all CPUs as a
342 none: External NMI is masked for all CPUs. This is
343 useful so that a dump capture kernel won't be
347 See Documentation/networking/ipv6.txt.
349 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
350 Limit apic dumping. The parameter defines the maximal
351 number of local apics being dumped. Also it is possible
352 to set it to "all" by meaning -- no limit here.
353 Format: { 1 (default) | 2 | ... | all }.
354 The parameter valid if only apic=debug or
355 apic=verbose is specified.
356 Example: apic=debug show_lapic=all
358 apm= [APM] Advanced Power Management
359 See header of arch/x86/kernel/apm_32.c.
361 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
362 Format: <io>,<irq>,<nodeID>
366 atarimouse= [HW,MOUSE] Atari Mouse
368 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
369 EzKey and similar keyboards
371 atkbd.reset= [HW] Reset keyboard during initialization
373 atkbd.set= [HW] Select keyboard code set
374 Format: <int> (2 = AT (default), 3 = PS/2)
376 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
379 atkbd.softraw= [HW] Choose between synthetic and real raw mode
380 Format: <bool> (0 = real, 1 = synthetic (default))
382 atkbd.softrepeat= [HW]
383 Use software keyboard repeat
385 audit= [KNL] Enable the audit sub-system
386 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
387 0 - kernel audit is disabled and can not be enabled
388 until the next reboot
389 unset - kernel audit is initialized but disabled and
390 will be fully enabled by the userspace auditd.
391 1 - kernel audit is initialized and partially enabled,
392 storing at most audit_backlog_limit messages in
393 RAM until it is fully enabled by the userspace
397 audit_backlog_limit= [KNL] Set the audit queue size limit.
398 Format: <int> (must be >=0)
401 bau= [X86_UV] Enable the BAU on SGI UV. The default
402 behavior is to disable the BAU (i.e. bau=0).
403 Format: { "0" | "1" }
406 unset - Disable the BAU.
408 baycom_epp= [HW,AX25]
411 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
413 See header of drivers/net/hamradio/baycom_par.c.
415 baycom_ser_fdx= [HW,AX25]
416 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
417 Format: <io>,<irq>,<mode>[,<baud>]
418 See header of drivers/net/hamradio/baycom_ser_fdx.c.
420 baycom_ser_hdx= [HW,AX25]
421 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
422 Format: <io>,<irq>,<mode>
423 See header of drivers/net/hamradio/baycom_ser_hdx.c.
425 blkdevparts= Manual partition parsing of block device(s) for
426 embedded devices based on command line input.
427 See Documentation/block/cmdline-partition.txt
429 boot_delay= Milliseconds to delay each printk during boot.
430 Values larger than 10 seconds (10000) are changed to
434 bootmem_debug [KNL] Enable bootmem allocator debug messages.
437 Disable BERT OS support on buggy BIOSes.
439 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
440 bttv.radio= Most important insmod options are available as
442 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
445 bulk_remove=off [PPC] This parameter disables the use of the pSeries
446 firmware feature for flushing multiple hpte entries
449 c101= [NET] Moxa C101 synchronous serial card
451 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
452 Sometimes CPU hardware bugs make them report the cache
453 size incorrectly. The kernel will attempt work arounds
454 to fix known problems, but for some CPUs it is not
455 possible to determine what the correct size should be.
456 This option provides an override for these situations.
458 ca_keys= [KEYS] This parameter identifies a specific key(s) on
459 the system trusted keyring to be used for certificate
461 format: { id:<keyid> | builtin }
463 cca= [MIPS] Override the kernel pages' cache coherency
464 algorithm. Accepted values range from 0 to 7
465 inclusive. See arch/mips/include/asm/pgtable-bits.h
466 for platform specific values (SB1, Loongson3 and
469 ccw_timeout_log [S390]
470 See Documentation/s390/CommonIO for details.
472 cgroup_disable= [KNL] Disable a particular controller
473 Format: {name of the controller(s) to disable}
474 The effects of cgroup_disable=foo are:
475 - foo isn't auto-mounted if you mount all cgroups in
477 - foo isn't visible as an individually mountable
479 {Currently only "memory" controller deal with this and
480 cut the overhead, others just disable the usage. So
481 only cgroup_disable=memory is actually worthy}
483 cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1
484 Format: { controller[,controller...] | "all" }
485 Like cgroup_disable, but only applies to cgroup v1;
486 the blacklisted controllers remain available in cgroup2.
488 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
490 nosocket -- Disable socket memory accounting.
491 nokmem -- Disable kernel memory accounting.
493 checkreqprot [SELINUX] Set initial checkreqprot flag value.
494 Format: { "0" | "1" }
495 See security/selinux/Kconfig help text.
496 0 -- check protection applied by kernel (includes
497 any implied execute protection).
498 1 -- check protection requested by application.
499 Default value is set via a kernel config option.
500 Value can be changed at runtime via
501 /selinux/checkreqprot.
504 See Documentation/s390/CommonIO for details.
507 Prevents the clock framework from automatically gating
508 clocks that have not been explicitly enabled by a Linux
509 device driver but are enabled in hardware at reset or
510 by the bootloader/firmware. Note that this does not
511 force such clocks to be always-on nor does it reserve
512 those clocks in any way. This parameter is useful for
513 debug and development, but should not be needed on a
514 platform with proper driver support. For more
515 information, see Documentation/clk.txt.
517 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
519 Forces specified clocksource (if available) to be used
520 when calculating gettimeofday(). If specified
521 clocksource is not available, it defaults to PIT.
522 Format: { pit | tsc | cyclone | pmtmr }
524 clocksource= Override the default clocksource
526 Override the default clocksource and use the clocksource
527 with the name specified.
528 Some clocksource names to choose from, depending on
530 [all] jiffies (this is the base, fallback clocksource)
532 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
533 pxa_timer,timer3,32k_counter,timer0_1
534 [X86-32] pit,hpet,tsc;
535 scx200_hrt on Geode; cyclone on IBM x440
543 clocksource.arm_arch_timer.evtstrm=
546 Enable/disable the eventstream feature of the ARM
547 architected timer so that code using WFE-based polling
548 loops can be debugged more effectively on production
551 clearcpuid=BITNUM [X86]
552 Disable CPUID feature X for the kernel. See
553 arch/x86/include/asm/cpufeatures.h for the valid bit
554 numbers. Note the Linux specific bits are not necessarily
555 stable over kernel options, but the vendor specific
557 Also note that user programs calling CPUID directly
558 or using the feature without checking anything
559 will still see it. This just prevents it from
560 being used by the kernel or shown in /proc/cpuinfo.
561 Also note the kernel might malfunction if you disable
564 cma=nn[MG]@[start[MG][-end[MG]]]
566 Sets the size of kernel global memory area for
567 contiguous memory allocations and optionally the
568 placement constraint by the physical address range of
569 memory allocations. A value of 0 disables CMA
570 altogether. For more information, see
571 include/linux/dma-contiguous.h
573 cmo_free_hint= [PPC] Format: { yes | no }
574 Specify whether pages are marked as being inactive
575 when they are freed. This is used in CMO environments
576 to determine OS memory pressure for page stealing by
580 coherent_pool=nn[KMG] [ARM,KNL]
581 Sets the size of memory pool for coherent, atomic dma
582 allocations, by default set to 256K.
584 code_bytes [X86] How many bytes of object code to print
589 com20020= [HW,NET] ARCnet - COM20020 chipset
591 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
593 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
597 ARCnet - COM90xx chipset (memory-mapped buffers)
598 Format: <io>[,<irq>[,<memstart>]]
600 condev= [HW,S390] console device
603 console= [KNL] Output console device and options.
605 tty<n> Use the virtual console device <n>.
609 Use the specified serial port. The options are of
610 the form "bbbbpnf", where "bbbb" is the baud rate,
611 "p" is parity ("n", "o", or "e"), "n" is number of
612 bits, and "f" is flow control ("r" for RTS or
613 omit it). Default is "9600n8".
615 See Documentation/admin-guide/serial-console.rst for more
617 Documentation/networking/netconsole.txt for an
620 uart[8250],io,<addr>[,options]
621 uart[8250],mmio,<addr>[,options]
622 uart[8250],mmio16,<addr>[,options]
623 uart[8250],mmio32,<addr>[,options]
624 uart[8250],0x<addr>[,options]
625 Start an early, polled-mode console on the 8250/16550
626 UART at the specified I/O port or MMIO address,
627 switching to the matching ttyS device later.
628 MMIO inter-register address stride is either 8-bit
629 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
630 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
631 to be equivalent to 'mmio'. 'options' are specified in
632 the same format described for ttyS above; if unspecified,
633 the h/w is not re-initialized.
635 hvc<n> Use the hypervisor console device <n>. This is for
636 both Xen and PowerPC hypervisors.
638 If the device connected to the port is not a TTY but a braille
639 device, prepend "brl," before the device type, for instance
641 For now, only VisioBraille is supported.
643 consoleblank= [KNL] The console blank (screen saver) timeout in
644 seconds. Defaults to 10*60 = 10mins. A value of 0
645 disables the blank timer.
648 [KNL] Change the default value for
649 /proc/<pid>/coredump_filter.
650 See also Documentation/filesystems/proc.txt.
652 cpuidle.off=1 [CPU_IDLE]
653 disable the cpuidle sub-system
655 cpufreq.off=1 [CPU_FREQ]
656 disable the cpufreq sub-system
659 [X86] Delay for N microsec between assert and de-assert
660 of APIC INIT to start processors. This delay occurs
661 on every CPU online, such as boot, and resume from suspend.
664 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
666 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
668 crashkernel=size[KMG][@offset[KMG]]
669 [KNL] Using kexec, Linux can switch to a 'crash kernel'
670 upon panic. This parameter reserves the physical
671 memory region [offset, offset + size] for that kernel
672 image. If '@offset' is omitted, then a suitable offset
673 is selected automatically. Check
674 Documentation/kdump/kdump.txt for further details.
676 crashkernel=range1:size1[,range2:size2,...][@offset]
677 [KNL] Same as above, but depends on the memory
678 in the running system. The syntax of range is
679 start-[end] where start and end are both
680 a memory unit (amount[KMG]). See also
681 Documentation/kdump/kdump.txt for an example.
683 crashkernel=size[KMG],high
684 [KNL, x86_64] range could be above 4G. Allow kernel
685 to allocate physical memory region from top, so could
686 be above 4G if system have more than 4G ram installed.
687 Otherwise memory region will be allocated below 4G, if
689 It will be ignored if crashkernel=X is specified.
690 crashkernel=size[KMG],low
691 [KNL, x86_64] range under 4G. When crashkernel=X,high
692 is passed, kernel could allocate physical memory region
693 above 4G, that cause second kernel crash on system
694 that require some amount of low memory, e.g. swiotlb
695 requires at least 64M+32K low memory, also enough extra
696 low memory is needed to make sure DMA buffers for 32-bit
697 devices won't run out. Kernel would try to allocate at
698 at least 256M below 4G automatically.
699 This one let user to specify own low range under 4G
700 for second kernel instead.
701 0: to disable low allocation.
702 It will be ignored when crashkernel=X,high is not used
703 or memory reserved is below 4G.
706 [KNL] Disable crypto self-tests
711 cs89x0_media= [HW,NET]
712 Format: { rj45 | aui | bnc }
715 See header of drivers/s390/block/dasd_devmap.c.
717 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
718 (one device per port)
719 Format: <port#>,<type>
720 See also Documentation/input/joystick-parport.txt
722 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
723 time. See Documentation/dynamic-debug-howto.txt for
724 details. Deprecated, see dyndbg.
726 debug [KNL] Enable kernel debugging (events log level).
729 [KNL] verbose self-tests
731 Print debugging info while doing the locking API
733 We default to 0 (no extra messages), setting it to
734 1 will print _a lot_ more information - normally
735 only useful to kernel developers.
737 debug_objects [KNL] Enable object debugging
740 [KNL] Disable object debugging
742 debug_guardpage_minorder=
743 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
744 parameter allows control of the order of pages that will
745 be intentionally kept free (and hence protected) by the
746 buddy allocator. Bigger value increase the probability
747 of catching random memory corruption, but reduce the
748 amount of memory for normal system use. The maximum
749 possible value is MAX_ORDER/2. Setting this parameter
750 to 1 or 2 should be enough to identify most random
751 memory corruption problems caused by bugs in kernel or
752 driver code when a CPU writes to (or reads from) a
753 random memory location. Note that there exists a class
754 of memory corruptions problems caused by buggy H/W or
755 F/W or by drivers badly programing DMA (basically when
756 memory is written at bus level and the CPU MMU is
757 bypassed) which are not detectable by
758 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
759 tracking down these problems.
762 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
763 parameter enables the feature at boot time. In
764 default, it is disabled. We can avoid allocating huge
765 chunk of memory for debug pagealloc if we don't enable
766 it at boot time and the system will work mostly same
767 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
768 on: enable the feature
770 debugpat [X86] Enable PAT debugging
772 decnet.addr= [HW,NET]
773 Format: <area>[,<node>]
774 See also Documentation/networking/decnet.txt.
777 [same as hugepagesz=] The size of the default
778 HugeTLB page size. This is the size represented by
779 the legacy /proc/ hugepages APIs, used for SHM, and
780 default size when mounting hugetlbfs filesystems.
781 Defaults to the default architecture's huge page size
785 Set number of hash buckets for dentry cache.
787 disable_1tb_segments [PPC]
788 Disables the use of 1TB hash page table segments. This
789 causes the kernel to fall back to 256MB segments which
790 can be useful when debugging issues that require an SLB
794 See Documentation/networking/ipv6.txt.
797 Disable RADIX MMU mode on POWER9
799 disable_cpu_apicid= [X86,APIC,SMP]
801 The number of initial APIC ID for the
802 corresponding CPU to be disabled at boot,
803 mostly used for the kdump 2nd kernel to
804 disable BSP to wake up multiple CPUs without
805 causing system reset or hang due to sending
808 disable_ddw [PPC/PSERIES]
809 Disable Dynamic DMA Window support. Use this if
810 to workaround buggy firmware.
813 See Documentation/networking/ipv6.txt.
815 disable_mtrr_cleanup [X86]
816 The kernel tries to adjust MTRR layout from continuous
817 to discrete, to make X server driver able to add WB
818 entry later. This parameter disables that.
820 disable_mtrr_trim [X86, Intel and AMD only]
821 By default the kernel will trim any uncacheable
822 memory out of your available memory pool based on
823 MTRR settings. This parameter disables that behavior,
824 possibly causing your machine to run very slowly.
826 disable_timer_pin_1 [X86]
827 Disable PIN 1 of APIC timer
828 Can be useful to work around chipset bugs.
830 dis_ucode_ldr [X86] Disable the microcode loader.
832 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
833 this option disables the debugging code at boot.
835 dma_debug_entries=<number>
836 This option allows to tune the number of preallocated
837 entries for DMA-API debugging code. One entry is
838 required per DMA-API allocation. Use this if the
839 DMA-API debugging code disables itself because the
840 architectural default is too low.
842 dma_debug_driver=<driver_name>
843 With this option the DMA-API debugging driver
844 filter feature can be enabled at boot time. Just
845 pass the driver to filter for as the parameter.
846 The filter can be disabled or changed to another
847 driver later using sysfs.
849 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
850 Broken monitors, graphic adapters, KVMs and EDIDless
851 panels may send no or incorrect EDID data sets.
852 This parameter allows to specify an EDID data sets
853 in the /lib/firmware directory that are used instead.
854 Generic built-in EDID data sets are used, if one of
855 edid/1024x768.bin, edid/1280x1024.bin,
856 edid/1680x1050.bin, or edid/1920x1080.bin is given
857 and no file with the same name exists. Details and
858 instructions how to build your own EDID data are
859 available in Documentation/EDID/HOWTO.txt. An EDID
860 data set will only be used for a particular connector,
861 if its name and a colon are prepended to the EDID
862 name. Each connector may use a unique EDID data
863 set by separating the files with a comma. An EDID
864 data set with no connector name will be used for
865 any connectors not explicitly specified.
869 dump_apple_properties [X86]
870 Dump name and content of EFI device properties on
871 x86 Macs. Useful for driver authors to determine
872 what data is available or for reverse-engineering.
874 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
875 module.dyndbg[="val"]
876 Enable debug messages at boot time. See
877 Documentation/dynamic-debug-howto.txt for details.
879 nompx [X86] Disables Intel Memory Protection Extensions.
880 See Documentation/x86/intel_mpx.txt for more
881 information about the feature.
883 nopku [X86] Disable Memory Protection Keys CPU feature found
886 module.async_probe [KNL]
887 Enable asynchronous probe on this module.
889 early_ioremap_debug [KNL]
890 Enable debug messages in early_ioremap support. This
891 is useful for tracking down temporary early mappings
892 which are not unmapped.
894 earlycon= [KNL] Output early console device and options.
896 When used with no options, the early console is
897 determined by the stdout-path property in device
900 cdns,<addr>[,options]
901 Start an early, polled-mode console on a Cadence
902 (xuartps) serial port at the specified address. Only
903 supported option is baud rate. If baud rate is not
904 specified, the serial port must already be setup and
907 uart[8250],io,<addr>[,options]
908 uart[8250],mmio,<addr>[,options]
909 uart[8250],mmio32,<addr>[,options]
910 uart[8250],mmio32be,<addr>[,options]
911 uart[8250],0x<addr>[,options]
912 Start an early, polled-mode console on the 8250/16550
913 UART at the specified I/O port or MMIO address.
914 MMIO inter-register address stride is either 8-bit
915 (mmio) or 32-bit (mmio32 or mmio32be).
916 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
917 to be equivalent to 'mmio'. 'options' are specified
918 in the same format described for "console=ttyS<n>"; if
919 unspecified, the h/w is not initialized.
923 Start an early, polled-mode console on a pl011 serial
924 port at the specified address. The pl011 serial port
925 must already be setup and configured. Options are not
926 yet supported. If 'mmio32' is specified, then only
927 the driver will use only 32-bit accessors to read/write
928 the device registers.
931 Start an early, polled-mode console on a meson serial
932 port at the specified address. The serial port must
933 already be setup and configured. Options are not yet
937 Start an early, polled-mode console on an msm serial
938 port at the specified address. The serial port
939 must already be setup and configured. Options are not
943 Start an early, polled-mode console on an msm serial
944 dm port at the specified address. The serial port
945 must already be setup and configured. Options are not
948 smh Use ARM semihosting calls for early console.
956 Use early console provided by serial driver available
957 on Samsung SoCs, requires selecting proper type and
958 a correct base address of the selected UART port. The
959 serial port must already be setup and configured.
960 Options are not yet supported.
963 Start an early, polled-mode console on a lantiq serial
964 (lqasc) port at the specified address. The serial port
965 must already be setup and configured. Options are not
970 Use early console provided by Freescale LP UART driver
971 found on Freescale Vybrid and QorIQ LS1021A processors.
972 A valid base address must be provided, and the serial
973 port must already be setup and configured.
976 Start an early, polled-mode console on the
977 Armada 3700 serial port at the specified
978 address. The serial port must already be setup
979 and configured. Options are not yet supported.
981 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k,S390]
986 earlyprintk=serial[,ttySn[,baudrate]]
987 earlyprintk=serial[,0x...[,baudrate]]
988 earlyprintk=ttySn[,baudrate]
989 earlyprintk=dbgp[debugController#]
990 earlyprintk=pciserial,bus:device.function[,baudrate]
991 earlyprintk=xdbc[xhciController#]
993 earlyprintk is useful when the kernel crashes before
994 the normal console is initialized. It is not enabled by
995 default because it has some cosmetic problems.
997 Append ",keep" to not disable it when the real console
1000 Only one of vga, efi, serial, or usb debug port can
1003 Currently only ttyS0 and ttyS1 may be specified by
1004 name. Other I/O ports may be explicitly specified
1005 on some architectures (x86 and arm at least) by
1006 replacing ttySn with an I/O port address, like this:
1007 earlyprintk=serial,0x1008,115200
1008 You can find the port for a given device in
1009 /proc/tty/driver/serial:
1010 2: uart:ST16650V2 port:00001008 irq:18 ...
1012 Interaction with the standard serial driver is not
1015 The VGA and EFI output is eventually overwritten by
1018 The xen output can only be used by Xen PV guests.
1020 The sclp output can only be used on s390.
1022 edac_report= [HW,EDAC] Control how to report EDAC event
1023 Format: {"on" | "off" | "force"}
1024 on: enable EDAC to report H/W event. May be overridden
1025 by other higher priority error reporting module.
1026 off: disable H/W event reporting through EDAC.
1027 force: enforce the use of EDAC to report H/W event.
1030 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1033 This is designed to be used in conjunction with
1034 the boot argument: earlyprintk=vga
1037 Format: {"off" | "on" | "skip[mbr]"}
1040 Format: { "old_map", "nochunk", "noruntime", "debug" }
1041 old_map [X86-64]: switch to the old ioremap-based EFI
1042 runtime services mapping. 32-bit still uses this one by
1044 nochunk: disable reading files in "chunks" in the EFI
1045 boot stub, as chunking can cause problems with some
1046 firmware implementations.
1047 noruntime : disable EFI runtime services support
1048 debug: enable misc debug output
1050 efi_no_storage_paranoia [EFI; X86]
1051 Using this parameter you can use more than 50% of
1052 your efi variable storage. Use this parameter only if
1053 you are really sure that your UEFI does sane gc and
1054 fulfills the spec otherwise your board may brick.
1056 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1057 Add arbitrary attribute to specific memory range by
1058 updating original EFI memory map.
1059 Region of memory which aa attribute is added to is
1061 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1062 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1063 attribute is added to range 0x100000000-0x180000000 and
1064 0x10a0000000-0x1120000000.
1066 Using this parameter you can do debugging of EFI memmap
1067 related feature. For example, you can do debugging of
1068 Address Range Mirroring feature even if your box
1071 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1072 that is to be dynamically loaded by Linux. If there are
1073 multiple variables with the same name but with different
1074 vendor GUIDs, all of them will be loaded. See
1075 Documentation/acpi/ssdt-overlays.txt for details.
1078 eisa_irq_edge= [PARISC,HW]
1079 See header of drivers/parisc/eisa.c.
1082 See comment before function elanfreq_setup() in
1083 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1086 Format: {"cfq" | "deadline" | "noop"}
1087 See Documentation/block/cfq-iosched.txt and
1088 Documentation/block/deadline-iosched.txt for details.
1090 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1091 Specifies physical address of start of kernel core
1092 image elf header and optionally the size. Generally
1093 kexec loader will pass this option to capture kernel.
1094 See Documentation/kdump/kdump.txt for details.
1096 enable_mtrr_cleanup [X86]
1097 The kernel tries to adjust MTRR layout from continuous
1098 to discrete, to make X server driver able to add WB
1099 entry later. This parameter enables that.
1101 enable_timer_pin_1 [X86]
1102 Enable PIN 1 of APIC timer
1103 Can be useful to work around chipset bugs
1104 (in particular on some ATI chipsets).
1105 The kernel tries to set a reasonable default.
1107 enforcing [SELINUX] Set initial enforcing status.
1109 See security/selinux/Kconfig help text.
1110 0 -- permissive (log only, no denials).
1111 1 -- enforcing (deny and log).
1113 Value can be changed at runtime via /selinux/enforce.
1116 Disable Error Record Serialization Table (ERST)
1119 ether= [HW,NET] Ethernet cards parameters
1120 This option is obsoleted by the "netdev=" option, which
1121 has equivalent usage. See its documentation for details.
1125 Permit 'security.evm' to be updated regardless of
1126 current integrity status.
1130 fail_make_request=[KNL]
1131 General fault injection mechanism.
1132 Format: <interval>,<probability>,<space>,<times>
1133 See also Documentation/fault-injection/.
1136 See Documentation/blockdev/floppy.txt.
1138 force_pal_cache_flush
1139 [IA-64] Avoid check_sal_cache_flush which may hang on
1140 buggy SAL_CACHE_FLUSH implementations. Using this
1141 parameter will force ia64_sal_cache_flush to call
1142 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1145 Forcefully enable Physical Address Extension (PAE).
1146 Many Pentium M systems disable PAE but may have a
1147 functionally usable PAE implementation.
1148 Warning: use of this parameter will taint the kernel
1149 and may cause unknown problems.
1152 [FTRACE] will set and start the specified tracer
1153 as early as possible in order to facilitate early
1156 ftrace_dump_on_oops[=orig_cpu]
1157 [FTRACE] will dump the trace buffers on oops.
1158 If no parameter is passed, ftrace will dump
1159 buffers of all CPUs, but if you pass orig_cpu, it will
1160 dump only the buffer of the CPU that triggered the
1163 ftrace_filter=[function-list]
1164 [FTRACE] Limit the functions traced by the function
1165 tracer at boot up. function-list is a comma separated
1166 list of functions. This list can be changed at run
1167 time by the set_ftrace_filter file in the debugfs
1170 ftrace_notrace=[function-list]
1171 [FTRACE] Do not trace the functions specified in
1172 function-list. This list can be changed at run time
1173 by the set_ftrace_notrace file in the debugfs
1176 ftrace_graph_filter=[function-list]
1177 [FTRACE] Limit the top level callers functions traced
1178 by the function graph tracer at boot up.
1179 function-list is a comma separated list of functions
1180 that can be changed at run time by the
1181 set_graph_function file in the debugfs tracing directory.
1183 ftrace_graph_notrace=[function-list]
1184 [FTRACE] Do not trace from the functions specified in
1185 function-list. This list is a comma separated list of
1186 functions that can be changed at run time by the
1187 set_graph_notrace file in the debugfs tracing directory.
1189 ftrace_graph_max_depth=<uint>
1190 [FTRACE] Used with the function graph tracer. This is
1191 the max depth it will trace into a function. This value
1192 can be changed at run time by the max_graph_depth file
1193 in the tracefs tracing directory. default: 0 (no limit)
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 goldfish [X86] Enable the goldfish android emulator platform.
1214 Don't use this when you are not running on the
1217 gpt [EFI] Forces disk with valid GPT signature but
1218 invalid Protective MBR to be treated as GPT. If the
1219 primary GPT is corrupted, it enables the backup/alternate
1220 GPT to be used instead.
1222 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1223 the "Enable 0" bit of the configuration register.
1226 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1227 the "Enable 0" bit of the configuration register.
1230 grcan.select= [HW] Select which physical interface to use.
1233 grcan.txsize= [HW] Sets the size of the tx buffer.
1234 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1236 grcan.rxsize= [HW] Sets the size of the rx buffer.
1237 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1240 gpio-mockup.gpio_mockup_ranges
1241 [HW] Sets the ranges of gpiochip of for this device.
1242 Format: <start1>,<end1>,<start2>,<end2>...
1244 hardlockup_all_cpu_backtrace=
1245 [KNL] Should the hard-lockup detector generate
1246 backtraces on all cpus.
1249 hashdist= [KNL,NUMA] Large hashes allocated during boot
1250 are distributed across NUMA nodes. Defaults on
1251 for 64-bit NUMA, off otherwise.
1252 Format: 0 | 1 (for off | on)
1254 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1256 hd= [EIDE] (E)IDE hard drive subsystem geometry
1257 Format: <cyl>,<head>,<sect>
1260 Disable Hardware Error Source Table (HEST) support;
1261 corresponding firmware-first mode error processing
1262 logic will be disabled.
1264 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1265 size of <nn>. This works even on boxes that have no
1266 highmem otherwise. This also works to reduce highmem
1267 size on bigger boxes.
1269 highres= [KNL] Enable/disable high resolution timer mode.
1270 Valid parameters: "on", "off"
1274 See Documentation/isdn/README.HiSax.
1278 hpet= [X86-32,HPET] option to control HPET usage
1279 Format: { enable (default) | disable | force |
1281 disable: disable HPET and use PIT instead
1282 force: allow force enabled of undocumented chips (ICH4,
1284 verbose: show contents of HPET registers during setup
1286 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1287 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1289 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1290 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1291 On x86-64 and powerpc, this option can be specified
1292 multiple times interleaved with hugepages= to reserve
1293 huge pages of different sizes. Valid pages sizes on
1294 x86-64 are 2M (when the CPU supports "pse") and 1G
1295 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1297 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1298 terminal devices. Valid values: 0..8
1299 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1300 If specified, z/VM IUCV HVC accepts connections
1301 from listed z/VM user IDs only.
1303 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1304 hardware thread id mappings.
1305 Format: <cpu>:<hwthread>
1308 Do not unregister boot console at start. This is only
1309 useful for debugging when something happens in the window
1310 between unregistering the boot console and initializing
1313 i2c_bus= [HW] Override the default board specific I2C bus speed
1314 or register an additional I2C bus that is not
1315 registered from board initialization code.
1319 i8042.debug [HW] Toggle i8042 debug mode
1320 i8042.unmask_kbd_data
1321 [HW] Enable printing of interrupt data from the KBD port
1322 (disabled by default, and as a pre-condition
1323 requires that i8042.debug=1 be enabled)
1324 i8042.direct [HW] Put keyboard port into non-translated mode
1325 i8042.dumbkbd [HW] Pretend that controller can only read data from
1326 keyboard and cannot control its state
1327 (Don't attempt to blink the leds)
1328 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1329 i8042.nokbd [HW] Don't check/create keyboard port
1330 i8042.noloop [HW] Disable the AUX Loopback command while probing
1332 i8042.nomux [HW] Don't check presence of an active multiplexing
1334 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1336 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1337 i8042.reset [HW] Reset the controller during init, cleanup and
1338 suspend-to-ram transitions, only during s2r
1339 transitions, or never reset
1340 Format: { 1 | Y | y | 0 | N | n }
1341 1, Y, y: always reset controller
1342 0, N, n: don't ever reset controller
1343 Default: only on s2r transitions on x86; most other
1344 architectures force reset to be always executed
1345 i8042.unlock [HW] Unlock (ignore) the keylock
1346 i8042.kbdreset [HW] Reset device connected to KBD port
1350 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1351 indicates that the driver is running on unsupported
1353 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1354 does not match list of supported models.
1356 [HW] Report power status in /proc/i8k
1357 (disabled by default)
1358 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1361 i915.invert_brightness=
1362 [DRM] Invert the sense of the variable that is used to
1363 set the brightness of the panel backlight. Normally a
1364 brightness value of 0 indicates backlight switched off,
1365 and the maximum of the brightness value sets the backlight
1366 to maximum brightness. If this parameter is set to 0
1367 (default) and the machine requires it, or this parameter
1368 is set to 1, a brightness value of 0 sets the backlight
1369 to maximum brightness, and the maximum of the brightness
1370 value switches the backlight off.
1371 -1 -- never invert brightness
1372 0 -- machine default
1373 1 -- force brightness inversion
1376 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1378 ide-core.nodma= [HW] (E)IDE subsystem
1379 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1380 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1381 .cdrom .chs .ignore_cable are additional options
1382 See Documentation/ide/ide.txt.
1384 ide-generic.probe-mask= [HW] (E)IDE subsystem
1386 Probe mask for legacy ISA IDE ports. Depending on
1387 platform up to 6 ports are supported, enabled by
1388 setting corresponding bits in the mask to 1. The
1389 default value is 0x0, which has a special meaning.
1390 On systems that have PCI, it triggers scanning the
1391 PCI bus for the first and the second port, which
1392 are then probed. On systems without PCI the value
1393 of 0x0 enables probing the two first ports as if it
1396 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1397 Claim all unknown PCI IDE storage controllers.
1400 Format: idle=poll, idle=halt, idle=nomwait
1401 Poll forces a polling idle loop that can slightly
1402 improve the performance of waking up a idle CPU, but
1403 will use a lot of power and make the system run hot.
1405 idle=halt: Halt is forced to be used for CPU idle.
1406 In such case C2/C3 won't be used again.
1407 idle=nomwait: Disable mwait for CPU C-states
1409 ieee754= [MIPS] Select IEEE Std 754 conformance mode
1410 Format: { strict | legacy | 2008 | relaxed }
1413 Choose which programs will be accepted for execution
1414 based on the IEEE 754 NaN encoding(s) supported by
1415 the FPU and the NaN encoding requested with the value
1416 of an ELF file header flag individually set by each
1417 binary. Hardware implementations are permitted to
1418 support either or both of the legacy and the 2008 NaN
1421 Available settings are as follows:
1422 strict accept binaries that request a NaN encoding
1423 supported by the FPU
1424 legacy only accept legacy-NaN binaries, if supported
1426 2008 only accept 2008-NaN binaries, if supported
1428 relaxed accept any binaries regardless of whether
1429 supported by the FPU
1431 The FPU emulator is always able to support both NaN
1432 encodings, so if no FPU hardware is present or it has
1433 been disabled with 'nofpu', then the settings of
1434 'legacy' and '2008' strap the emulator accordingly,
1435 'relaxed' straps the emulator for both legacy-NaN and
1436 2008-NaN, whereas 'strict' enables legacy-NaN only on
1437 legacy processors and both NaN encodings on MIPS32 or
1440 The setting for ABS.fmt/NEG.fmt instruction execution
1441 mode generally follows that for the NaN encoding,
1442 except where unsupported by hardware.
1444 ignore_loglevel [KNL]
1445 Ignore loglevel setting - this will print /all/
1446 kernel messages to the console. Useful for debugging.
1447 We also add it as printk module parameter, so users
1448 could change it dynamically, usually by
1449 /sys/module/printk/parameters/ignore_loglevel.
1452 Ignore RLIMIT_DATA setting for data mappings,
1453 print warning at first misuse. Can be changed via
1454 /sys/module/kernel/parameters/ignore_rlimit_data.
1456 ihash_entries= [KNL]
1457 Set number of hash buckets for inode cache.
1459 ima_appraise= [IMA] appraise integrity measurements
1460 Format: { "off" | "enforce" | "fix" | "log" }
1463 ima_appraise_tcb [IMA]
1464 The builtin appraise policy appraises all files
1467 ima_canonical_fmt [IMA]
1468 Use the canonical format for the binary runtime
1469 measurements, instead of host native format.
1472 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1476 The list of supported hash algorithms is defined
1477 in crypto/hash_info.h.
1480 The builtin measurement policy to load during IMA
1481 setup. Specyfing "tcb" as the value, measures all
1482 programs exec'd, files mmap'd for exec, and all files
1483 opened with the read mode bit set by either the
1484 effective uid (euid=0) or uid=0.
1487 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1488 Load a policy which meets the needs of the Trusted
1489 Computing Base. This means IMA will measure all
1490 programs exec'd, files mmap'd for exec, and all files
1491 opened for read by uid=0.
1494 Select one of defined IMA measurements template formats.
1495 Formats: { "ima" | "ima-ng" | "ima-sig" }
1499 [IMA] Define a custom template format.
1500 Format: { "field1|...|fieldN" }
1502 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1503 Format: <min_file_size>
1504 Set the minimal file size for using asynchronous hash.
1505 If left unspecified, ahash usage is disabled.
1507 ahash performance varies for different data sizes on
1508 different crypto accelerators. This option can be used
1509 to achieve the best performance for a particular HW.
1511 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1513 Set hashing buffer size. Default: 4k.
1515 ahash performance varies for different chunk sizes on
1516 different crypto accelerators. This option can be used
1517 to achieve best performance for particular HW.
1521 Run specified binary instead of /sbin/init as init
1524 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1525 for working out where the kernel is dying during
1528 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1529 initcall functions. Useful for debugging built-in
1530 modules and initcalls.
1532 initrd= [BOOT] Specify the location of the initial ramdisk
1534 init_pkru= [x86] Specify the default memory protection keys rights
1535 register contents for all processes. 0x55555554 by
1536 default (disallow access to all but pkey 0). Can
1537 override in debugfs after boot.
1539 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1542 int_pln_enable [x86] Enable power limit notification interrupt
1544 integrity_audit=[IMA]
1545 Format: { "0" | "1" }
1546 0 -- basic integrity auditing messages. (Default)
1547 1 -- additional integrity auditing messages.
1549 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1551 Enable intel iommu driver.
1553 Disable intel iommu driver.
1554 igfx_off [Default Off]
1555 By default, gfx is mapped as normal device. If a gfx
1556 device has a dedicated DMAR unit, the DMAR unit is
1557 bypassed by not enabling DMAR with this option. In
1558 this case, gfx device will use physical address for
1561 With this option iommu will not optimize to look
1562 for io virtual address below 32-bit forcing dual
1563 address cycle on pci bus for cards supporting greater
1564 than 32-bit addressing. The default is to look
1565 for translation below 32-bit and if not available
1566 then look in the higher range.
1567 strict [Default Off]
1568 With this option on every unmap_single operation will
1569 result in a hardware IOTLB flush operation as opposed
1570 to batching them for performance.
1571 sp_off [Default Off]
1572 By default, super page will be supported if Intel IOMMU
1573 has the capability. With this option, super page will
1575 ecs_off [Default Off]
1576 By default, extended context tables will be supported if
1577 the hardware advertises that it has support both for the
1578 extended tables themselves, and also PASID support. With
1579 this option set, extended tables will not be used even
1580 on hardware which claims to support them.
1581 tboot_noforce [Default Off]
1582 Do not force the Intel IOMMU enabled under tboot.
1583 By default, tboot will force Intel IOMMU on, which
1584 could harm performance of some high-throughput
1585 devices like 40GBit network cards, even if identity
1587 Note that using this option lowers the security
1588 provided by tboot because it makes the system
1589 vulnerable to DMA attacks.
1591 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1592 0 disables intel_idle and fall back on acpi_idle.
1593 1 to 9 specify maximum depth of C-state.
1597 Do not enable intel_pstate as the default
1598 scaling driver for the supported processors
1600 Use intel_pstate as a scaling driver, but configure it
1601 to work with generic cpufreq governors (instead of
1602 enabling its internal governor). This mode cannot be
1603 used along with the hardware-managed P-states (HWP)
1606 Enable intel_pstate on systems that prohibit it by default
1607 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1608 instead of acpi-cpufreq may disable platform features, such
1609 as thermal controls and power capping, that rely on ACPI
1610 P-States information being indicated to OSPM and therefore
1611 should be used with caution. This option does not work with
1612 processors that aren't supported by the intel_pstate driver
1613 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1615 Do not enable hardware P state control (HWP)
1618 Only load intel_pstate on systems which support
1619 hardware P state control (HWP) if available.
1621 Enforce ACPI _PPC performance limits. If the Fixed ACPI
1622 Description Table, specifies preferred power management
1623 profile as "Enterprise Server" or "Performance Server",
1624 then this feature is turned on by default.
1626 Allow per-logical-CPU P-State performance control limits using
1627 cpufreq sysfs interface
1629 intremap= [X86-64, Intel-IOMMU]
1630 on enable Interrupt Remapping (default)
1631 off disable Interrupt Remapping
1632 nosid disable Source ID checking
1634 BIOS x2APIC opt-out request will be ignored
1635 nopost disable Interrupt Posting
1637 iomem= Disable strict checking of access to MMIO memory
1638 strict regions from userspace.
1653 nobypass [PPC/POWERNV]
1654 Disable IOMMU bypass, using IOMMU for PCI devices.
1657 [ARM64] Configure DMA to bypass the IOMMU by default.
1658 Format: { "0" | "1" }
1659 0 - Use IOMMU translation for DMA.
1660 1 - Bypass the IOMMU for DMA.
1661 unset - Use IOMMU translation for DMA.
1663 io7= [HW] IO7 for Marvel based alpha systems
1664 See comment before marvel_specify_io7 in
1665 arch/alpha/kernel/core_marvel.c.
1667 io_delay= [X86] I/O delay method
1669 Standard port 0x80 based delay
1671 Alternate port 0xed based delay (needed on some systems)
1673 Simple two microseconds delay
1678 See Documentation/filesystems/nfs/nfsroot.txt.
1680 irqaffinity= [SMP] Set the default irq affinity mask
1681 The argument is a cpu list, as described above.
1684 When an interrupt is not handled search all handlers
1685 for it. Intended to get systems with badly broken
1689 When an interrupt is not handled search all handlers
1690 for it. Also check all handlers each timer
1691 interrupt. Intended to get systems with badly broken
1695 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1697 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1698 The argument is a cpu list, as described above.
1700 This option can be used to specify one or more CPUs
1701 to isolate from the general SMP balancing and scheduling
1702 algorithms. You can move a process onto or off an
1703 "isolated" CPU via the CPU affinity syscalls or cpuset.
1704 <cpu number> begins at 0 and the maximum value is
1705 "number of CPUs in system - 1".
1707 This option is the preferred way to isolate CPUs. The
1708 alternative -- manually setting the CPU mask of all
1709 tasks in the system -- can cause problems and
1710 suboptimal load balancer performance.
1714 ivrs_ioapic [HW,X86_64]
1715 Provide an override to the IOAPIC-ID<->DEVICE-ID
1716 mapping provided in the IVRS ACPI table. For
1717 example, to map IOAPIC-ID decimal 10 to
1718 PCI device 00:14.0 write the parameter as:
1719 ivrs_ioapic[10]=00:14.0
1721 ivrs_hpet [HW,X86_64]
1722 Provide an override to the HPET-ID<->DEVICE-ID
1723 mapping provided in the IVRS ACPI table. For
1724 example, to map HPET-ID decimal 0 to
1725 PCI device 00:14.0 write the parameter as:
1726 ivrs_hpet[0]=00:14.0
1728 ivrs_acpihid [HW,X86_64]
1729 Provide an override to the ACPI-HID:UID<->DEVICE-ID
1730 mapping provided in the IVRS ACPI table. For
1731 example, to map UART-HID:UID AMD0020:0 to
1732 PCI device 00:14.5 write the parameter as:
1733 ivrs_acpihid[00:14.5]=AMD0020:0
1735 js= [HW,JOY] Analog joystick
1736 See Documentation/input/joystick.txt.
1739 When CONFIG_RANDOMIZE_BASE is set, this disables
1740 kernel and module base offset ASLR (Address Space
1741 Layout Randomization).
1744 [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
1745 report on every invalid memory access. Without this
1746 parameter KASAN will print report only for the first
1751 kernelcore= [KNL,X86,IA-64,PPC]
1752 Format: nn[KMGTPE] | "mirror"
1754 specifies the amount of memory usable by the kernel
1755 for non-movable allocations. The requested amount is
1756 spread evenly throughout all nodes in the system. The
1757 remaining memory in each node is used for Movable
1758 pages. In the event, a node is too small to have both
1759 kernelcore and Movable pages, kernelcore pages will
1760 take priority and other nodes will have a larger number
1761 of Movable pages. The Movable zone is used for the
1762 allocation of pages that may be reclaimed or moved
1763 by the page migration subsystem. This means that
1764 HugeTLB pages may not be allocated from this zone.
1765 Note that allocations like PTEs-from-HighMem still
1766 use the HighMem zone if it exists, and the Normal
1767 zone if it does not.
1769 Instead of specifying the amount of memory (nn[KMGTPE]),
1770 you can specify "mirror" option. In case "mirror"
1771 option is specified, mirrored (reliable) memory is used
1772 for non-movable allocations and remaining memory is used
1773 for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
1774 so you can NOT specify nn[KMGTPE] and "mirror" at the same
1777 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1778 Format: <Controller#>[,poll interval]
1779 The controller # is the number of the ehci usb debug
1780 port as it is probed via PCI. The poll interval is
1781 optional and is the number seconds in between
1782 each poll cycle to the debug port in case you need
1783 the functionality for interrupting the kernel with
1784 gdb or control-c on the dbgp connection. When
1785 not using this parameter you use sysrq-g to break into
1786 the kernel debugger.
1788 kgdboc= [KGDB,HW] kgdb over consoles.
1789 Requires a tty driver that supports console polling,
1790 or a supported polling keyboard driver (non-usb).
1791 Serial only format: <serial_device>[,baud]
1792 keyboard only format: kbd
1793 keyboard and serial format: kbd,<serial_device>[,baud]
1794 Optional Kernel mode setting:
1795 kms, kbd format: kms,kbd
1796 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1798 kgdbwait [KGDB] Stop kernel execution and enter the
1799 kernel debugger at the earliest opportunity.
1801 kmac= [MIPS] korina ethernet MAC address.
1802 Configure the RouterBoard 532 series on-chip
1803 Ethernet adapter MAC address.
1805 kmemleak= [KNL] Boot-time kmemleak enable/disable
1806 Valid arguments: on, off
1808 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1811 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1812 Valid arguments: 0, 1, 2
1813 kmemcheck=0 (disabled)
1814 kmemcheck=1 (enabled)
1815 kmemcheck=2 (one-shot mode)
1816 Default: 2 (one-shot mode)
1818 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1819 Default is 0 (don't ignore, but inject #GP)
1821 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1825 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1826 Default is 1 (enabled)
1828 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1830 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1832 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1833 (virtualized MMU) support on capable Intel chips.
1834 Default is 1 (enabled)
1836 kvm-intel.emulate_invalid_guest_state=
1837 [KVM,Intel] Enable emulation of invalid guest states
1838 Default is 0 (disabled)
1840 kvm-intel.flexpriority=
1841 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1842 Default is 1 (enabled)
1845 [KVM,Intel] Enable VMX nesting (nVMX).
1846 Default is 0 (disabled)
1848 kvm-intel.unrestricted_guest=
1849 [KVM,Intel] Disable unrestricted guest feature
1850 (virtualized real and unpaged mode) on capable
1851 Intel chips. Default is 1 (enabled)
1853 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1854 feature (tagged TLBs) on capable Intel chips.
1855 Default is 1 (enabled)
1861 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1864 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1865 value for LAPIC timer one-shot implementation. Default
1866 back to the programmable timer unit in the LAPIC.
1868 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1871 libata.dma= [LIBATA] DMA control
1872 libata.dma=0 Disable all PATA and SATA DMA
1873 libata.dma=1 PATA and SATA Disk DMA only
1874 libata.dma=2 ATAPI (CDROM) DMA only
1875 libata.dma=4 Compact Flash DMA only
1876 Combinations also work, so libata.dma=3 enables DMA
1877 for disks and CDROMs, but not CFs.
1879 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1880 libata.ignore_hpa=0 keep BIOS limits (default)
1881 libata.ignore_hpa=1 ignore limits, using full disk
1883 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1887 libata.force= [LIBATA] Force configurations. The format is comma
1888 separated list of "[ID:]VAL" where ID is
1889 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1890 matching port, link or device. Basically, it matches
1891 the ATA ID string printed on console by libata. If
1892 the whole ID part is omitted, the last PORT and DEVICE
1893 values are used. If ID hasn't been specified yet, the
1894 configuration applies to all ports, links and devices.
1896 If only DEVICE is omitted, the parameter applies to
1897 the port and all links and devices behind it. DEVICE
1898 number of 0 either selects the first device or the
1899 first fan-out link behind PMP device. It does not
1900 select the host link. DEVICE number of 15 selects the
1901 host link and device attached to it.
1903 The VAL specifies the configuration to force. As long
1904 as there's no ambiguity shortcut notation is allowed.
1905 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1906 The following configurations can be forced.
1908 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1909 Any ID with matching PORT is used.
1911 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1913 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1914 udma[/][16,25,33,44,66,100,133] notation is also
1917 * [no]ncq: Turn on or off NCQ.
1919 * [no]ncqtrim: Turn off queued DSM TRIM.
1921 * nohrst, nosrst, norst: suppress hard, soft
1924 * rstonce: only attempt one reset during
1925 hot-unplug link recovery
1927 * dump_id: dump IDENTIFY data.
1929 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1931 * disable: Disable this device.
1933 If there are multiple matching configurations changing
1934 the same attribute, the last one is used.
1936 memblock=debug [KNL] Enable memblock debug messages.
1938 load_ramdisk= [RAM] List of ramdisks to load from floppy
1939 See Documentation/blockdev/ramdisk.txt.
1941 lockd.nlm_grace_period=P [NFS] Assign grace period.
1944 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1947 lockd.nlm_timeout=T [NFS] Assign timeout value.
1950 lockd.nlm_udpport=M [NFS] Assign UDP port.
1953 locktorture.nreaders_stress= [KNL]
1954 Set the number of locking read-acquisition kthreads.
1955 Defaults to being automatically set based on the
1956 number of online CPUs.
1958 locktorture.nwriters_stress= [KNL]
1959 Set the number of locking write-acquisition kthreads.
1961 locktorture.onoff_holdoff= [KNL]
1962 Set time (s) after boot for CPU-hotplug testing.
1964 locktorture.onoff_interval= [KNL]
1965 Set time (s) between CPU-hotplug operations, or
1966 zero to disable CPU-hotplug testing.
1968 locktorture.shuffle_interval= [KNL]
1969 Set task-shuffle interval (jiffies). Shuffling
1970 tasks allows some CPUs to go into dyntick-idle
1971 mode during the locktorture test.
1973 locktorture.shutdown_secs= [KNL]
1974 Set time (s) after boot system shutdown. This
1975 is useful for hands-off automated testing.
1977 locktorture.stat_interval= [KNL]
1978 Time (s) between statistics printk()s.
1980 locktorture.stutter= [KNL]
1981 Time (s) to stutter testing, for example,
1982 specifying five seconds causes the test to run for
1983 five seconds, wait for five seconds, and so on.
1984 This tests the locking primitive's ability to
1985 transition abruptly to and from idle.
1987 locktorture.torture_runnable= [BOOT]
1988 Start locktorture running at boot time.
1990 locktorture.torture_type= [KNL]
1991 Specify the locking implementation to test.
1993 locktorture.verbose= [KNL]
1994 Enable additional printk() statements.
1996 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1999 loglevel= All Kernel Messages with a loglevel smaller than the
2000 console loglevel will be printed to the console. It can
2001 also be changed with klogd or other programs. The
2002 loglevels are defined as follows:
2004 0 (KERN_EMERG) system is unusable
2005 1 (KERN_ALERT) action must be taken immediately
2006 2 (KERN_CRIT) critical conditions
2007 3 (KERN_ERR) error conditions
2008 4 (KERN_WARNING) warning conditions
2009 5 (KERN_NOTICE) normal but significant condition
2010 6 (KERN_INFO) informational
2011 7 (KERN_DEBUG) debug-level messages
2013 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
2014 in bytes. n must be a power of two and greater
2015 than the minimal size. The minimal size is defined
2016 by LOG_BUF_SHIFT kernel config parameter. There is
2017 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
2018 that allows to increase the default size depending on
2019 the number of CPUs. See init/Kconfig for more details.
2021 logo.nologo [FB] Disables display of the built-in Linux logo.
2022 This may be used to provide more screen space for
2023 kernel log messages and is useful when debugging
2024 kernel boot problems.
2026 lp=0 [LP] Specify parallel ports to use, e.g,
2027 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
2028 lp=reset first parallel port). 'lp=0' disables the
2029 lp=auto printer driver. 'lp=reset' (which can be
2030 specified in addition to the ports) causes
2031 attached printers to be reset. Using
2032 lp=port1,port2,... specifies the parallel ports
2033 to associate lp devices with, starting with
2034 lp0. A port specification may be 'none' to skip
2035 that lp device, or a parport name such as
2036 'parport0'. Specifying 'lp=auto' instead of a
2037 port specification list means that device IDs
2038 from each port should be examined, to see if
2039 an IEEE 1284-compliant printer is attached; if
2040 so, the driver will manage that printer.
2041 See also header of drivers/char/lp.c.
2044 Sets loops_per_jiffy to given constant, thus avoiding
2045 time-consuming boot-time autodetection (up to 250 ms per
2046 CPU). 0 enables autodetection (default). To determine
2047 the correct value for your kernel, boot with normal
2048 autodetection and see what value is printed. Note that
2049 on SMP systems the preset will be applied to all CPUs,
2050 which is likely to cause problems if your CPUs need
2051 significantly divergent settings. An incorrect value
2052 will cause delays in the kernel to be wrong, leading to
2053 unpredictable I/O errors and other breakage. Although
2054 unlikely, in the extreme case this might damage your
2058 Format: <io>,<irq>,<dma>
2060 machvec= [IA-64] Force the use of a particular machine-vector
2061 (machvec) in a generic kernel.
2062 Example: machvec=hpzx1_swiotlb
2064 machtype= [Loongson] Share the same kernel image file between different
2066 Example: machtype=lemote-yeeloong-2f-7inch
2068 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2069 than or equal to this physical address is ignored.
2071 maxcpus= [SMP] Maximum number of processors that an SMP kernel
2072 will bring up during bootup. maxcpus=n : n >= 0 limits
2073 the kernel to bring up 'n' processors. Surely after
2074 bootup you can bring up the other plugged cpu by executing
2075 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
2076 only takes effect during system bootup.
2077 While n=0 is a special case, it is equivalent to "nosmp",
2078 which also disables the IO APIC.
2080 max_loop= [LOOP] The number of loop block devices that get
2081 (loop.max_loop) unconditionally pre-created at init time. The default
2082 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2083 of statically allocating a predefined number, loop
2084 devices can be requested on-demand with the
2085 /dev/loop-control interface.
2087 mce [X86-32] Machine Check Exception
2089 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2091 md= [HW] RAID subsystems devices and level
2092 See Documentation/admin-guide/md.rst.
2095 Format: <first>,<last>
2096 Specifies range of consoles to be captured by the MDA.
2098 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2099 Amount of memory to be used when the kernel is not able
2100 to see the whole system memory or for test.
2101 [X86] Work as limiting max address. Use together
2102 with memmap= to avoid physical address space collisions.
2103 Without memmap= PCI devices could be placed at addresses
2104 belonging to unused RAM.
2106 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2110 [KNL,SH] Allow user to override the default size for
2111 per-device physically contiguous DMA buffers.
2113 memhp_default_state=online/offline
2114 [KNL] Set the initial state for the memory hotplug
2115 onlining policy. If not specified, the default value is
2116 set according to the
2117 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
2119 See Documentation/memory-hotplug.txt.
2121 memmap=exactmap [KNL,X86] Enable setting of an exact
2122 E820 memory map, as specified by the user.
2123 Such memmap=exactmap lines can be constructed based on
2124 BIOS output or other requirements. See the memmap=nn@ss
2127 memmap=nn[KMG]@ss[KMG]
2128 [KNL] Force usage of a specific region of memory.
2129 Region of memory to be used is from ss to ss+nn.
2131 memmap=nn[KMG]#ss[KMG]
2132 [KNL,ACPI] Mark specific memory as ACPI data.
2133 Region of memory to be marked is from ss to ss+nn.
2135 memmap=nn[KMG]$ss[KMG]
2136 [KNL,ACPI] Mark specific memory as reserved.
2137 Region of memory to be reserved is from ss to ss+nn.
2138 Example: Exclude memory from 0x18690000-0x1869ffff
2139 memmap=64K$0x18690000
2141 memmap=0x10000$0x18690000
2143 memmap=nn[KMG]!ss[KMG]
2144 [KNL,X86] Mark specific memory as protected.
2145 Region of memory to be used, from ss to ss+nn.
2146 The memory region may be marked as e820 type 12 (0xc)
2147 and is NVDIMM or ADR memory.
2149 memory_corruption_check=0/1 [X86]
2150 Some BIOSes seem to corrupt the first 64k of
2151 memory when doing things like suspend/resume.
2152 Setting this option will scan the memory
2153 looking for corruption. Enabling this will
2154 both detect corruption and prevent the kernel
2155 from using the memory being corrupted.
2156 However, its intended as a diagnostic tool; if
2157 repeatable BIOS-originated corruption always
2158 affects the same memory, you can use memmap=
2159 to prevent the kernel from using that memory.
2161 memory_corruption_check_size=size [X86]
2162 By default it checks for corruption in the low
2163 64k, making this memory unavailable for normal
2164 use. Use this parameter to scan for
2165 corruption in more or less memory.
2167 memory_corruption_check_period=seconds [X86]
2168 By default it checks for corruption every 60
2169 seconds. Use this parameter to check at some
2170 other rate. 0 disables periodic checking.
2172 memtest= [KNL,X86,ARM] Enable memtest
2174 default : 0 <disable>
2175 Specifies the number of memtest passes to be
2176 performed. Each pass selects another test
2177 pattern from a given set of patterns. Memtest
2178 fills the memory with this pattern, validates
2179 memory contents and reserves bad memory
2180 regions that are detected.
2182 mem_sleep_default= [SUSPEND] Default system suspend mode:
2183 s2idle - Suspend-To-Idle
2184 shallow - Power-On Suspend or equivalent (if supported)
2185 deep - Suspend-To-RAM or equivalent (if supported)
2186 See Documentation/power/states.txt.
2188 meye.*= [HW] Set MotionEye Camera parameters
2189 See Documentation/video4linux/meye.txt.
2191 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2192 Multi-Function General Purpose Timers on AMD Geode
2195 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2196 the BIOS has incorrectly applied a workaround. TinyBIOS
2197 version 0.98 is known to be affected, 0.99 fixes the
2198 problem by letting the user disable the workaround.
2202 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2203 physical address is ignored.
2205 mini2440= [ARM,HW,KNL]
2206 Format:[0..2][b][c][t]
2208 MINI2440 configuration specification:
2209 0 - The attached screen is the 3.5" TFT
2210 1 - The attached screen is the 7" TFT
2211 2 - The VGA Shield is attached (1024x768)
2212 Leaving out the screen size parameter will not load
2213 the TFT driver, and the framebuffer will be left
2215 b - Enable backlight. The TFT backlight pin will be
2216 linked to the kernel VESA blanking code and a GPIO
2217 LED. This parameter is not necessary when using the
2219 c - Enable the s3c camera interface.
2220 t - Reserved for enabling touchscreen support. The
2221 touchscreen support is not enabled in the mainstream
2222 kernel as of 2.6.30, a preliminary port can be found
2223 in the "bleeding edge" mini2440 support kernel at
2224 http://repo.or.cz/w/linux-2.6/mini2440.git
2227 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2228 parameter allows control of the logging verbosity for
2229 the additional memory initialisation checks. A value
2230 of 0 disables mminit logging and a level of 4 will
2231 log everything. Information is printed at KERN_DEBUG
2232 so loglevel=8 may also need to be specified.
2235 [KNL] When CONFIG_MODULE_SIG is set, this means that
2236 modules without (valid) signatures will fail to load.
2237 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2238 is always true, so this option does nothing.
2240 module_blacklist= [KNL] Do not load a comma-separated list of
2241 modules. Useful for debugging problem modules.
2244 [MOUSE] Maximum time between finger touching and
2245 leaving touchpad surface for touch to be considered
2246 a tap and be reported as a left button click (for
2247 touchpads working in absolute mode only).
2249 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2250 reporting absolute coordinates, such as tablets
2251 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2252 reporting absolute coordinates, such as tablets
2254 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2255 is similar to kernelcore except it specifies the
2256 amount of memory used for migratable allocations.
2257 If both kernelcore and movablecore is specified,
2258 then kernelcore will be at *least* the specified
2259 value but may be more. If movablecore on its own
2260 is specified, the administrator must be careful
2261 that the amount of memory usable for all allocations
2264 movable_node [KNL] Boot-time switch to enable the effects
2265 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2267 MTD_Partition= [MTD]
2268 Format: <name>,<region-number>,<size>,<offset>
2270 MTD_Region= [MTD] Format:
2271 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2274 See drivers/mtd/cmdlinepart.c.
2276 multitce=off [PPC] This parameter disables the use of the pSeries
2277 firmware feature for updating multiple TCE entries
2280 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2282 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2284 boundary - index of last SLC block on Flex-OneNAND.
2285 The remaining blocks are configured as MLC blocks.
2286 lock - Configure if Flex-OneNAND boundary should be locked.
2287 Once locked, the boundary cannot be changed.
2288 1 indicates lock status, 0 indicates unlock status.
2291 ARM/S3C2412 JIVE boot control
2293 See arch/arm/mach-s3c2412/mach-jive.c
2295 mtouchusb.raw_coordinates=
2296 [HW] Make the MicroTouch USB driver use raw coordinates
2297 ('y', default) or cooked coordinates ('n')
2299 mtrr_chunk_size=nn[KMG] [X86]
2300 used for mtrr cleanup. It is largest continuous chunk
2301 that could hold holes aka. UC entries.
2303 mtrr_gran_size=nn[KMG] [X86]
2304 Used for mtrr cleanup. It is granularity of mtrr block.
2306 Large value could prevent small alignment from
2309 mtrr_spare_reg_nr=n [X86]
2311 Range: 0,7 : spare reg number
2313 Used for mtrr cleanup. It is spare mtrr entries number.
2314 Set to 2 or more if your graphical card needs more.
2316 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2318 netdev= [NET] Network devices parameters
2319 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2320 Note that mem_start is often overloaded to mean
2321 something different and driver-specific.
2322 This usage is only documented in each driver source
2326 [NETFILTER] Enable connection tracking flow accounting
2327 0 to disable accounting
2328 1 to enable accounting
2331 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2332 See Documentation/filesystems/nfs/nfsroot.txt.
2334 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2335 See Documentation/filesystems/nfs/nfsroot.txt.
2337 nfsrootdebug [NFS] enable nfsroot debugging messages.
2338 See Documentation/filesystems/nfs/nfsroot.txt.
2340 nfs.callback_nr_threads=
2341 [NFSv4] set the total number of threads that the
2342 NFS client will assign to service NFSv4 callback
2345 nfs.callback_tcpport=
2346 [NFS] set the TCP port on which the NFSv4 callback
2347 channel should listen.
2350 [NFS] sets the pathname to the program which is used
2351 to update the NFS client cache entries.
2353 nfs.cache_getent_timeout=
2354 [NFS] sets the timeout after which an attempt to
2355 update a cache entry is deemed to have failed.
2357 nfs.idmap_cache_timeout=
2358 [NFS] set the maximum lifetime for idmapper cache
2362 [NFS] enable 64-bit inode numbers.
2363 If zero, the NFS client will fake up a 32-bit inode
2364 number for the readdir() and stat() syscalls instead
2365 of returning the full 64-bit number.
2366 The default is to return 64-bit inode numbers.
2368 nfs.max_session_cb_slots=
2369 [NFSv4.1] Sets the maximum number of session
2370 slots the client will assign to the callback
2371 channel. This determines the maximum number of
2372 callbacks the client will process in parallel for
2373 a particular server.
2375 nfs.max_session_slots=
2376 [NFSv4.1] Sets the maximum number of session slots
2377 the client will attempt to negotiate with the server.
2378 This limits the number of simultaneous RPC requests
2379 that the client can send to the NFSv4.1 server.
2380 Note that there is little point in setting this
2381 value higher than the max_tcp_slot_table_limit.
2383 nfs.nfs4_disable_idmapping=
2384 [NFSv4] When set to the default of '1', this option
2385 ensures that both the RPC level authentication
2386 scheme and the NFS level operations agree to use
2387 numeric uids/gids if the mount is using the
2388 'sec=sys' security flavour. In effect it is
2389 disabling idmapping, which can make migration from
2390 legacy NFSv2/v3 systems to NFSv4 easier.
2391 Servers that do not support this mode of operation
2392 will be autodetected by the client, and it will fall
2393 back to using the idmapper.
2394 To turn off this behaviour, set the value to '0'.
2396 [NFS4] Specify an additional fixed unique ident-
2397 ification string that NFSv4 clients can insert into
2398 their nfs_client_id4 string. This is typically a
2399 UUID that is generated at system install time.
2401 nfs.send_implementation_id =
2402 [NFSv4.1] Send client implementation identification
2403 information in exchange_id requests.
2404 If zero, no implementation identification information
2406 The default is to send the implementation identification
2409 nfs.recover_lost_locks =
2410 [NFSv4] Attempt to recover locks that were lost due
2411 to a lease timeout on the server. Please note that
2412 doing this risks data corruption, since there are
2413 no guarantees that the file will remain unchanged
2414 after the locks are lost.
2415 If you want to enable the kernel legacy behaviour of
2416 attempting to recover these locks, then set this
2418 The default parameter value of '0' causes the kernel
2419 not to attempt recovery of lost locks.
2421 nfs4.layoutstats_timer =
2422 [NFSv4.2] Change the rate at which the kernel sends
2423 layoutstats to the pNFS metadata server.
2425 Setting this to value to 0 causes the kernel to use
2426 whatever value is the default set by the layout
2427 driver. A non-zero value sets the minimum interval
2428 in seconds between layoutstats transmissions.
2430 nfsd.nfs4_disable_idmapping=
2431 [NFSv4] When set to the default of '1', the NFSv4
2432 server will return only numeric uids and gids to
2433 clients using auth_sys, and will accept numeric uids
2434 and gids from such clients. This is intended to ease
2435 migration from NFSv2/v3.
2437 nmi_debug= [KNL,SH] Specify one or more actions to take
2438 when a NMI is triggered.
2439 Format: [state][,regs][,debounce][,die]
2441 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2442 Format: [panic,][nopanic,][num]
2444 0 - turn hardlockup detector in nmi_watchdog off
2445 1 - turn hardlockup detector in nmi_watchdog on
2446 When panic is specified, panic when an NMI watchdog
2447 timeout occurs (or 'nopanic' to override the opposite
2448 default). To disable both hard and soft lockup detectors,
2449 please see 'nowatchdog'.
2450 This is useful when you use a panic=... timeout and
2451 need the box quickly up again.
2453 netpoll.carrier_timeout=
2454 [NET] Specifies amount of time (in seconds) that
2455 netpoll should wait for a carrier. By default netpoll
2458 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2459 emulation library even if a 387 maths coprocessor
2463 [HW] Never suspend the console
2464 Disable suspending of consoles during suspend and
2465 hibernate operations. Once disabled, debugging
2466 messages can reach various consoles while the rest
2467 of the system is being put to sleep (ie, while
2468 debugging driver suspend/resume hooks). This may
2469 not work reliably with all consoles, but is known
2470 to work with serial and VGA consoles.
2471 To facilitate more flexible debugging, we also add
2472 console_suspend, a printk module parameter to control
2473 it. Users could use console_suspend (usually
2474 /sys/module/printk/parameters/console_suspend) to
2475 turn on/off it dynamically.
2477 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2478 caches in the slab allocator. Saves per-node memory,
2479 but will impact performance.
2483 noapic [SMP,APIC] Tells the kernel to not make use of any
2484 IOAPICs that may be present in the system.
2486 noautogroup Disable scheduler automatic task group creation.
2488 nobats [PPC] Do not use BATs for mapping kernel lowmem
2489 on "Classic" PPC cores.
2493 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2495 nodelayacct [KNL] Disable per-task delay accounting
2497 nodsp [SH] Disable hardware DSP at boot time.
2499 noefi Disable EFI runtime services support.
2504 On X86-32 available only on PAE configured kernels.
2505 noexec=on: enable non-executable mappings (default)
2506 noexec=off: disable non-executable mappings
2509 Disable SMAP (Supervisor Mode Access Prevention)
2510 even if it is supported by processor.
2513 Disable SMEP (Supervisor Mode Execution Prevention)
2514 even if it is supported by processor.
2517 This affects only 32-bit executables.
2518 noexec32=on: enable non-executable mappings (default)
2519 read doesn't imply executable mappings
2520 noexec32=off: disable non-executable mappings
2521 read implies executable mappings
2523 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2525 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2526 register save and restore. The kernel will only save
2527 legacy floating-point registers on task switch.
2529 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2531 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
2532 Equivalent to smt=1.
2534 noxsave [BUGS=X86] Disables x86 extended register state save
2535 and restore using xsave. The kernel will fallback to
2536 enabling legacy floating-point and sse state.
2538 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2539 register states. The kernel will fall back to use
2540 xsave to save the states. By using this parameter,
2541 performance of saving the states is degraded because
2542 xsave doesn't support modified optimization while
2543 xsaveopt supports it on xsaveopt enabled systems.
2545 noxsaves [X86] Disables xsaves and xrstors used in saving and
2546 restoring x86 extended register state in compacted
2547 form of xsave area. The kernel will fall back to use
2548 xsaveopt and xrstor to save and restore the states
2549 in standard form of xsave area. By using this
2550 parameter, xsave area per process might occupy more
2551 memory on xsaves enabled systems.
2553 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2554 wfi(ARM) instruction doesn't work correctly and not to
2555 use it. This is also useful when using JTAG debugger.
2557 no_file_caps Tells the kernel not to honor file capabilities. The
2558 only way then for a file to be executed with privilege
2559 is to be setuid root or executed by root.
2561 nohalt [IA-64] Tells the kernel not to use the power saving
2562 function PAL_HALT_LIGHT when idle. This increases
2563 power-consumption. On the positive side, it reduces
2564 interrupt wake-up latency, which may improve performance
2565 in certain environments such as networked servers or
2568 nohibernate [HIBERNATION] Disable hibernation and resume.
2570 nohz= [KNL] Boottime enable/disable dynamic ticks
2571 Valid arguments: on, off
2574 nohz_full= [KNL,BOOT]
2575 The argument is a cpu list, as described above.
2576 In kernels built with CONFIG_NO_HZ_FULL=y, set
2577 the specified list of CPUs whose tick will be stopped
2578 whenever possible. The boot CPU will be forced outside
2579 the range to maintain the timekeeping.
2580 The CPUs in this range must also be included in the
2583 noiotrap [SH] Disables trapped I/O port accesses.
2585 noirqdebug [X86-32] Disables the code which attempts to detect and
2586 disable unhandled interrupt sources.
2588 no_timer_check [X86,APIC] Disables the code which tests for
2589 broken timer IRQ sources.
2591 noisapnp [ISAPNP] Disables ISA PnP code.
2593 noinitrd [RAM] Tells the kernel not to load any configured
2596 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2598 [Deprecated - use intremap=off]
2602 noinvpcid [X86] Disable the INVPCID cpu feature.
2604 nojitter [IA-64] Disables jitter checking for ITC timers.
2606 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2608 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2612 [X86,PV_OPS] Disable paravirtualized VMware scheduler
2613 clock and use the default one.
2615 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2616 steal time is computed, but won't influence scheduler
2619 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2621 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2623 noltlbs [PPC] Do not use large page/tlb entries for kernel
2624 lowmem mapping on PPC40x and PPC8xx
2626 nomca [IA-64] Disable machine check abort handling
2628 nomce [X86-32] Disable Machine Check Exception
2630 nomfgpt [X86-32] Disable Multi-Function General Purpose
2631 Timer usage (for AMD Geode machines).
2633 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2634 shutdown the other cpus. Instead use the REBOOT_VECTOR
2637 nomodule Disable module load
2639 nopat [X86] Disable PAT (page attribute table extension of
2640 pagetables) support.
2642 norandmaps Don't use address space randomization. Equivalent to
2643 echo 0 > /proc/sys/kernel/randomize_va_space
2645 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2647 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2648 with UP alternatives
2650 nordrand [X86] Disable kernel use of the RDRAND and
2651 RDSEED instructions even if they are supported
2652 by the processor. RDRAND and RDSEED are still
2653 available to user space applications.
2655 noresume [SWSUSP] Disables resume and restores original swap
2658 no-scroll [VGA] Disables scrollback.
2659 This is required for the Braillex ib80-piezo Braille
2660 reader made by F.H. Papenmeier (Germany).
2664 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2666 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2667 and disable the IO APIC. legacy for "maxcpus=0".
2669 nosoftlockup [KNL] Disable the soft-lockup detector.
2671 nosync [HW,M68K] Disables sync negotiation for all devices.
2673 notsc [BUGS=X86-32] Disable Time Stamp Counter
2675 nowatchdog [KNL] Disable both lockup detectors, i.e.
2676 soft-lockup and NMI watchdog (hard-lockup).
2680 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2682 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2683 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2684 Some features depend on CPU0. Known dependencies are:
2685 1. Resume from suspend/hibernate depends on CPU0.
2686 Suspend/hibernate will fail if CPU0 is offline and you
2687 need to online CPU0 before suspend/hibernate.
2688 2. PIC interrupts also depend on CPU0. CPU0 can't be
2689 removed if a PIC interrupt is detected.
2690 It's said poweroff/reboot may depend on CPU0 on some
2691 machines although I haven't seen such issues so far
2692 after CPU0 is offline on a few tested machines.
2693 If the dependencies are under your control, you can
2694 turn on cpu0_hotplug.
2696 nptcg= [IA-64] Override max number of concurrent global TLB
2697 purges which is reported from either PAL_VM_SUMMARY or
2700 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2701 could support. nr_cpus=n : n >= 1 limits the kernel to
2702 support 'n' processors. It could be larger than the
2703 number of already plugged CPU during bootup, later in
2704 runtime you can physically add extra cpu until it reaches
2705 n. So during boot up some boot time memory for per-cpu
2706 variables need be pre-allocated for later physical cpu
2709 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2711 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2712 Allowed values are enable and disable
2714 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2715 one of ['zone', 'node', 'default'] can be specified
2716 This can be set from sysctl after boot.
2717 See Documentation/sysctl/vm.txt for details.
2719 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2720 See Documentation/debugging-via-ohci1394.txt for more
2723 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2724 Rather than timing out after 20 ms if an EC
2725 command is not properly ACKed, override the length
2726 of the timeout. We have interrupts disabled while
2727 waiting for the ACK, so if this is set too high
2728 interrupts *may* be lost!
2730 omap_mux= [OMAP] Override bootloader pin multiplexing.
2731 Format: <mux_mode0.mode_name=value>...
2732 For example, to override I2C bus2:
2733 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2735 oprofile.timer= [HW]
2736 Use timer interrupt instead of performance counters
2738 oprofile.cpu_type= Force an oprofile cpu type
2739 This might be useful if you have an older oprofile
2740 userland or if you want common events.
2741 Format: { arch_perfmon }
2742 arch_perfmon: [X86] Force use of architectural
2743 perfmon on Intel CPUs instead of the
2744 CPU specific event set.
2745 timer: [X86] Force use of architectural NMI
2746 timer mode (see also oprofile.timer
2747 for generic hr timer mode)
2749 oops=panic Always panic on oopses. Default is to just kill the
2750 process, but there is a small probability of
2751 deadlocking the machine.
2752 This will also cause panics on machine check exceptions.
2753 Useful together with panic=30 to trigger a reboot.
2756 See Documentation/sound/oss/oss-parameters.txt
2758 page_owner= [KNL] Boot-time page_owner enabling option.
2759 Storage of the information about who allocated
2760 each page is disabled in default. With this switch,
2762 on: enable the feature
2764 page_poison= [KNL] Boot-time parameter changing the state of
2765 poisoning on the buddy allocator.
2766 off: turn off poisoning
2767 on: turn on poisoning
2769 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2770 timeout > 0: seconds before rebooting
2771 timeout = 0: wait forever
2772 timeout < 0: reboot immediately
2775 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2778 crash_kexec_post_notifiers
2779 Run kdump after running panic-notifiers and dumping
2780 kmsg. This only for the users who doubt kdump always
2781 succeeds in any situation.
2782 Note that this also increases risks of kdump failure,
2783 because some panic notifiers can make the crashed
2784 kernel more unstable.
2786 parkbd.port= [HW] Parallel port number the keyboard adapter is
2787 connected to, default is 0.
2789 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2790 0 for XT, 1 for AT (default is AT).
2793 parport= [HW,PPT] Specify parallel ports. 0 disables.
2794 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2795 Use 'auto' to force the driver to use any
2796 IRQ/DMA settings detected (the default is to
2797 ignore detected IRQ/DMA settings because of
2798 possible conflicts). You can specify the base
2799 address, IRQ, and DMA settings; IRQ and DMA
2800 should be numbers, or 'auto' (for using detected
2801 settings on that particular port), or 'nofifo'
2802 (to avoid using a FIFO even if it is detected).
2803 Parallel ports are assigned in the order they
2804 are specified on the command line, starting
2807 parport_init_mode= [HW,PPT]
2808 Configure VIA parallel port to operate in
2809 a specific mode. This is necessary on Pegasos
2810 computer where firmware has no options for setting
2811 up parallel port mode and sets it to spp.
2812 Currently this function knows 686a and 8231 chips.
2813 Format: [spp|ps2|epp|ecp|ecpepp]
2816 Halt all CPUs after the first oops has been printed for
2817 the specified number of seconds. This is to be used if
2818 your oopses keep scrolling off the screen.
2823 See header of drivers/block/paride/pcd.c.
2824 See also Documentation/blockdev/paride.txt.
2826 pci=option[,option...] [PCI] various PCI subsystem options:
2827 earlydump [X86] dump PCI config space before the kernel
2829 off [X86] don't probe for the PCI bus
2830 bios [X86-32] force use of PCI BIOS, don't access
2831 the hardware directly. Use this if your machine
2832 has a non-standard PCI host bridge.
2833 nobios [X86-32] disallow use of PCI BIOS, only direct
2834 hardware access methods are allowed. Use this
2835 if you experience crashes upon bootup and you
2836 suspect they are caused by the BIOS.
2837 conf1 [X86] Force use of PCI Configuration Access
2838 Mechanism 1 (config address in IO port 0xCF8,
2839 data in IO port 0xCFC, both 32-bit).
2840 conf2 [X86] Force use of PCI Configuration Access
2841 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
2842 the function, IO port 0xCFA, also 8-bit, sets
2843 bus number. The config space is then accessed
2844 through ports 0xC000-0xCFFF).
2845 See http://wiki.osdev.org/PCI for more info
2846 on the configuration access mechanisms.
2847 noaer [PCIE] If the PCIEAER kernel config parameter is
2848 enabled, this kernel boot option can be used to
2849 disable the use of PCIE advanced error reporting.
2850 nodomains [PCI] Disable support for multiple PCI
2851 root domains (aka PCI segments, in ACPI-speak).
2852 nommconf [X86] Disable use of MMCONFIG for PCI
2854 check_enable_amd_mmconf [X86] check for and enable
2855 properly configured MMIO access to PCI
2856 config space on AMD family 10h CPU
2857 nomsi [MSI] If the PCI_MSI kernel config parameter is
2858 enabled, this kernel boot option can be used to
2859 disable the use of MSI interrupts system-wide.
2860 noioapicquirk [APIC] Disable all boot interrupt quirks.
2861 Safety option to keep boot IRQs enabled. This
2862 should never be necessary.
2863 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2864 primary IO-APIC for bridges that cannot disable
2865 boot IRQs. This fixes a source of spurious IRQs
2866 when the system masks IRQs.
2867 noioapicreroute [APIC] Disable workaround that uses the
2868 boot IRQ equivalent of an IRQ that connects to
2869 a chipset where boot IRQs cannot be disabled.
2870 The opposite of ioapicreroute.
2871 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2872 routing table. These calls are known to be buggy
2873 on several machines and they hang the machine
2874 when used, but on other computers it's the only
2875 way to get the interrupt routing table. Try
2876 this option if the kernel is unable to allocate
2877 IRQs or discover secondary PCI buses on your
2879 rom [X86] Assign address space to expansion ROMs.
2880 Use with caution as certain devices share
2881 address decoders between ROMs and other
2883 norom [X86] Do not assign address space to
2884 expansion ROMs that do not already have
2885 BIOS assigned address ranges.
2886 nobar [X86] Do not assign address space to the
2887 BARs that weren't assigned by the BIOS.
2888 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2889 assigned automatically to PCI devices. You can
2890 make the kernel exclude IRQs of your ISA cards
2892 pirqaddr=0xAAAAA [X86] Specify the physical address
2893 of the PIRQ table (normally generated
2894 by the BIOS) if it is outside the
2895 F0000h-100000h range.
2896 lastbus=N [X86] Scan all buses thru bus #N. Can be
2897 useful if the kernel is unable to find your
2898 secondary buses and you want to tell it
2899 explicitly which ones they are.
2900 assign-busses [X86] Always assign all PCI bus
2901 numbers ourselves, overriding
2902 whatever the firmware may have done.
2903 usepirqmask [X86] Honor the possible IRQ mask stored
2904 in the BIOS $PIR table. This is needed on
2905 some systems with broken BIOSes, notably
2906 some HP Pavilion N5400 and Omnibook XE3
2907 notebooks. This will have no effect if ACPI
2908 IRQ routing is enabled.
2909 noacpi [X86] Do not use ACPI for IRQ routing
2910 or for PCI scanning.
2911 use_crs [X86] Use PCI host bridge window information
2912 from ACPI. On BIOSes from 2008 or later, this
2913 is enabled by default. If you need to use this,
2914 please report a bug.
2915 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2916 If you need to use this, please report a bug.
2917 routeirq Do IRQ routing for all PCI devices.
2918 This is normally done in pci_enable_device(),
2919 so this option is a temporary workaround
2920 for broken drivers that don't call it.
2921 skip_isa_align [X86] do not align io start addr, so can
2922 handle more pci cards
2923 noearly [X86] Don't do any early type 1 scanning.
2924 This might help on some broken boards which
2925 machine check when some devices' config space
2926 is read. But various workarounds are disabled
2927 and some IOMMU drivers will not work.
2928 bfsort Sort PCI devices into breadth-first order.
2929 This sorting is done to get a device
2930 order compatible with older (<= 2.4) kernels.
2931 nobfsort Don't sort PCI devices into breadth-first order.
2932 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2933 tuning and use the BIOS-configured MPS defaults.
2934 pcie_bus_safe Set every device's MPS to the largest value
2935 supported by all devices below the root complex.
2936 pcie_bus_perf Set device MPS to the largest allowable MPS
2937 based on its parent bus. Also set MRRS (Max
2938 Read Request Size) to the largest supported
2939 value (no larger than the MPS that the device
2940 or bus can support) for best performance.
2941 pcie_bus_peer2peer Set every device's MPS to 128B, which
2942 every device is guaranteed to support. This
2943 configuration allows peer-to-peer DMA between
2944 any pair of devices, possibly at the cost of
2945 reduced performance. This also guarantees
2946 that hot-added devices will work.
2947 cbiosize=nn[KMG] The fixed amount of bus space which is
2948 reserved for the CardBus bridge's IO window.
2949 The default value is 256 bytes.
2950 cbmemsize=nn[KMG] The fixed amount of bus space which is
2951 reserved for the CardBus bridge's memory
2952 window. The default value is 64 megabytes.
2955 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2956 [<order of align>@]pci:<vendor>:<device>\
2957 [:<subvendor>:<subdevice>][; ...]
2958 Specifies alignment and device to reassign
2959 aligned memory resources.
2960 If <order of align> is not specified,
2961 PAGE_SIZE is used as alignment.
2962 PCI-PCI bridge can be specified, if resource
2963 windows need to be expanded.
2964 To specify the alignment for several
2965 instances of a device, the PCI vendor,
2966 device, subvendor, and subdevice may be
2967 specified, e.g., 4096@pci:8086:9c22:103c:198f
2968 ecrc= Enable/disable PCIe ECRC (transaction layer
2969 end-to-end CRC checking).
2970 bios: Use BIOS/firmware settings. This is the
2974 hpiosize=nn[KMG] The fixed amount of bus space which is
2975 reserved for hotplug bridge's IO window.
2976 Default size is 256 bytes.
2977 hpmemsize=nn[KMG] The fixed amount of bus space which is
2978 reserved for hotplug bridge's memory window.
2979 Default size is 2 megabytes.
2980 hpbussize=nn The minimum amount of additional bus numbers
2981 reserved for buses below a hotplug bridge.
2983 realloc= Enable/disable reallocating PCI bridge resources
2984 if allocations done by BIOS are too small to
2985 accommodate resources required by all child
2987 off: Turn realloc off
2989 realloc same as realloc=on
2990 noari do not use PCIe ARI.
2991 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2992 only look for one device below a PCIe downstream
2995 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2998 force Enable ASPM even on devices that claim not to support it.
2999 WARNING: Forcing ASPM on may cause system lockups.
3001 pcie_hp= [PCIE] PCI Express Hotplug driver options:
3002 nomsi Do not use MSI for PCI Express Native Hotplug (this
3003 makes all PCIe ports use INTx for hotplug services).
3005 pcie_ports= [PCIE] PCIe ports handling:
3006 auto Ask the BIOS whether or not to use native PCIe services
3007 associated with PCIe ports (PME, hot-plug, AER). Use
3008 them only if that is allowed by the BIOS.
3009 native Use native PCIe services associated with PCIe ports
3011 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
3014 pcie_port_pm= [PCIE] PCIe port power management handling:
3015 off Disable power management of all PCIe ports
3016 force Forcibly enable power management of all PCIe ports
3018 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
3019 nomsi Do not use MSI for native PCIe PME signaling (this makes
3020 all PCIe root ports use INTx for all services).
3022 pcmv= [HW,PCMCIA] BadgePAD 4
3026 Keep all power-domains already enabled by bootloader on,
3027 even if no driver has claimed them. This is useful
3028 for debug and development, but should not be
3029 needed on a platform with proper driver support.
3032 See Documentation/blockdev/paride.txt.
3034 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
3037 See arch/parisc/kernel/pdc_chassis.c
3039 percpu_alloc= Select which percpu first chunk allocator to use.
3040 Currently supported values are "embed" and "page".
3041 Archs may support subset or none of the selections.
3042 See comments in mm/percpu.c for details on each
3043 allocator. This parameter is primarily for debugging
3044 and performance comparison.
3047 See Documentation/blockdev/paride.txt.
3050 See Documentation/blockdev/paride.txt.
3052 pirq= [SMP,APIC] Manual mp-table setup
3053 See Documentation/x86/i386/IO-APIC.txt.
3055 plip= [PPT,NET] Parallel port network link
3056 Format: { parport<nr> | timid | 0 }
3057 See also Documentation/parport.txt.
3059 pmtmr= [X86] Manual setup of pmtmr I/O Port.
3060 Override pmtimer IOPort with a hex value.
3064 Enable PNP debug messages (depends on the
3065 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
3066 via /sys/module/pnp/parameters/debug. We always show
3067 current resource usage; turning this on also shows
3068 possible settings and some assignment information.
3074 { on | off | curr | res | no-curr | no-res }
3077 [ISAPNP] Exclude IRQs for the autoconfiguration
3080 [ISAPNP] Exclude DMAs for the autoconfiguration
3082 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
3083 Ranges are in pairs (I/O port base and size).
3086 [ISAPNP] Exclude memory regions for the
3088 Ranges are in pairs (memory base and size).
3090 ports= [IP_VS_FTP] IPVS ftp helper module
3092 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3094 Format: <port>,<port>....
3096 powersave=off [PPC] This option disables power saving features.
3097 It specifically disables cpuidle and sets the
3098 platform machine description specific power_save
3099 function to NULL. On Idle the CPU just reduces
3102 ppc_strict_facility_enable
3103 [PPC] This option catches any kernel floating point,
3104 Altivec, VSX and SPE outside of regions specifically
3105 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3106 There is some performance impact when enabling this.
3108 print-fatal-signals=
3109 [KNL] debug: print fatal signals
3111 If enabled, warn about various signal handling
3112 related application anomalies: too many signals,
3113 too many POSIX.1 timers, fatal signals causing a
3116 If you hit the warning due to signal overflow,
3117 you might want to try "ulimit -i unlimited".
3121 printk.always_kmsg_dump=
3122 Trigger kmsg_dump for cases other than kernel oops or
3124 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3127 printk.devkmsg={on,off,ratelimit}
3128 Control writing to /dev/kmsg.
3129 on - unlimited logging to /dev/kmsg from userspace
3130 off - logging to /dev/kmsg disabled
3131 ratelimit - ratelimit the logging
3134 printk.time= Show timing data prefixed to each printk message line
3135 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3137 processor.max_cstate= [HW,ACPI]
3138 Limit processor to maximum C-state
3139 max_cstate=9 overrides any DMI blacklist limit.
3141 processor.nocst [HW,ACPI]
3142 Ignore the _CST method to determine C-states,
3143 instead using the legacy FADT method
3145 profile= [KNL] Enable kernel profiling via /proc/profile
3146 Format: [schedule,]<number>
3147 Param: "schedule" - profile schedule points.
3148 Param: <number> - step/bucket size as a power of 2 for
3149 statistical time based profiling.
3150 Param: "sleep" - profile D-state sleeping (millisecs).
3151 Requires CONFIG_SCHEDSTATS
3152 Param: "kvm" - profile VM exits.
3154 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3156 See Documentation/blockdev/ramdisk.txt.
3158 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3159 probe for; one of (bare|imps|exps|lifebook|any).
3160 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3162 psmouse.resetafter= [HW,MOUSE]
3163 Try to reset the device after so many bad packets
3166 [HW,MOUSE] Set desired mouse resolution, in dpi.
3167 psmouse.smartscroll=
3168 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3169 0 = disabled, 1 = enabled (default).
3171 pstore.backend= Specify the name of the pstore backend to use
3174 See Documentation/blockdev/paride.txt.
3177 [KNL] Number of legacy pty's. Overwrites compiled-in
3180 quiet [KNL] Disable most log messages
3185 See Documentation/admin-guide/md.rst.
3187 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3188 See Documentation/blockdev/ramdisk.txt.
3190 ras=option[,option,...] [KNL] RAS-specific options
3193 Disable the Correctable Errors Collector,
3194 see CONFIG_RAS_CEC help text.
3197 The argument is a cpu list, as described above.
3199 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3200 the specified list of CPUs to be no-callback CPUs.
3201 Invocation of these CPUs' RCU callbacks will
3202 be offloaded to "rcuox/N" kthreads created for
3203 that purpose, where "x" is "b" for RCU-bh, "p"
3204 for RCU-preempt, and "s" for RCU-sched, and "N"
3205 is the CPU number. This reduces OS jitter on the
3206 offloaded CPUs, which can be useful for HPC and
3207 real-time workloads. It can also improve energy
3208 efficiency for asymmetric multiprocessors.
3211 Rather than requiring that offloaded CPUs
3212 (specified by rcu_nocbs= above) explicitly
3213 awaken the corresponding "rcuoN" kthreads,
3214 make these kthreads poll for callbacks.
3215 This improves the real-time response for the
3216 offloaded CPUs by relieving them of the need to
3217 wake up the corresponding kthread, but degrades
3218 energy efficiency by requiring that the kthreads
3219 periodically wake up to do the polling.
3221 rcutree.blimit= [KNL]
3222 Set maximum number of finished RCU callbacks to
3223 process in one batch.
3225 rcutree.dump_tree= [KNL]
3226 Dump the structure of the rcu_node combining tree
3227 out at early boot. This is used for diagnostic
3228 purposes, to verify correct tree setup.
3230 rcutree.gp_cleanup_delay= [KNL]
3231 Set the number of jiffies to delay each step of
3232 RCU grace-period cleanup. This only has effect
3233 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3235 rcutree.gp_init_delay= [KNL]
3236 Set the number of jiffies to delay each step of
3237 RCU grace-period initialization. This only has
3238 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3241 rcutree.gp_preinit_delay= [KNL]
3242 Set the number of jiffies to delay each step of
3243 RCU grace-period pre-initialization, that is,
3244 the propagation of recent CPU-hotplug changes up
3245 the rcu_node combining tree. This only has effect
3246 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3248 rcutree.rcu_fanout_exact= [KNL]
3249 Disable autobalancing of the rcu_node combining
3250 tree. This is used by rcutorture, and might
3251 possibly be useful for architectures having high
3252 cache-to-cache transfer latencies.
3254 rcutree.rcu_fanout_leaf= [KNL]
3255 Change the number of CPUs assigned to each
3256 leaf rcu_node structure. Useful for very
3257 large systems, which will choose the value 64,
3258 and for NUMA systems with large remote-access
3259 latencies, which will choose a value aligned
3260 with the appropriate hardware boundaries.
3262 rcutree.jiffies_till_sched_qs= [KNL]
3263 Set required age in jiffies for a
3264 given grace period before RCU starts
3265 soliciting quiescent-state help from
3266 rcu_note_context_switch().
3268 rcutree.jiffies_till_first_fqs= [KNL]
3269 Set delay from grace-period initialization to
3270 first attempt to force quiescent states.
3271 Units are jiffies, minimum value is zero,
3272 and maximum value is HZ.
3274 rcutree.jiffies_till_next_fqs= [KNL]
3275 Set delay between subsequent attempts to force
3276 quiescent states. Units are jiffies, minimum
3277 value is one, and maximum value is HZ.
3279 rcutree.kthread_prio= [KNL,BOOT]
3280 Set the SCHED_FIFO priority of the RCU per-CPU
3281 kthreads (rcuc/N). This value is also used for
3282 the priority of the RCU boost threads (rcub/N)
3283 and for the RCU grace-period kthreads (rcu_bh,
3284 rcu_preempt, and rcu_sched). If RCU_BOOST is
3285 set, valid values are 1-99 and the default is 1
3286 (the least-favored priority). Otherwise, when
3287 RCU_BOOST is not set, valid values are 0-99 and
3288 the default is zero (non-realtime operation).
3290 rcutree.rcu_nocb_leader_stride= [KNL]
3291 Set the number of NOCB kthread groups, which
3292 defaults to the square root of the number of
3293 CPUs. Larger numbers reduces the wakeup overhead
3294 on the per-CPU grace-period kthreads, but increases
3295 that same overhead on each group's leader.
3297 rcutree.qhimark= [KNL]
3298 Set threshold of queued RCU callbacks beyond which
3299 batch limiting is disabled.
3301 rcutree.qlowmark= [KNL]
3302 Set threshold of queued RCU callbacks below which
3303 batch limiting is re-enabled.
3305 rcutree.rcu_idle_gp_delay= [KNL]
3306 Set wakeup interval for idle CPUs that have
3307 RCU callbacks (RCU_FAST_NO_HZ=y).
3309 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3310 Set wakeup interval for idle CPUs that have
3311 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3312 Lazy RCU callbacks are those which RCU can
3313 prove do nothing more than free memory.
3315 rcutree.rcu_kick_kthreads= [KNL]
3316 Cause the grace-period kthread to get an extra
3317 wake_up() if it sleeps three times longer than
3318 it should at force-quiescent-state time.
3319 This wake_up() will be accompanied by a
3320 WARN_ONCE() splat and an ftrace_dump().
3322 rcuperf.gp_exp= [KNL]
3323 Measure performance of expedited synchronous
3324 grace-period primitives.
3326 rcuperf.holdoff= [KNL]
3327 Set test-start holdoff period. The purpose of
3328 this parameter is to delay the start of the
3329 test until boot completes in order to avoid
3332 rcuperf.nreaders= [KNL]
3333 Set number of RCU readers. The value -1 selects
3334 N, where N is the number of CPUs. A value
3335 "n" less than -1 selects N-n+1, where N is again
3336 the number of CPUs. For example, -2 selects N
3337 (the number of CPUs), -3 selects N+1, and so on.
3338 A value of "n" less than or equal to -N selects
3341 rcuperf.nwriters= [KNL]
3342 Set number of RCU writers. The values operate
3343 the same as for rcuperf.nreaders.
3344 N, where N is the number of CPUs
3346 rcuperf.perf_runnable= [BOOT]
3347 Start rcuperf running at boot time.
3349 rcuperf.shutdown= [KNL]
3350 Shut the system down after performance tests
3351 complete. This is useful for hands-off automated
3354 rcuperf.perf_type= [KNL]
3355 Specify the RCU implementation to test.
3357 rcuperf.verbose= [KNL]
3358 Enable additional printk() statements.
3360 rcutorture.cbflood_inter_holdoff= [KNL]
3361 Set holdoff time (jiffies) between successive
3362 callback-flood tests.
3364 rcutorture.cbflood_intra_holdoff= [KNL]
3365 Set holdoff time (jiffies) between successive
3366 bursts of callbacks within a given callback-flood
3369 rcutorture.cbflood_n_burst= [KNL]
3370 Set the number of bursts making up a given
3371 callback-flood test. Set this to zero to
3372 disable callback-flood testing.
3374 rcutorture.cbflood_n_per_burst= [KNL]
3375 Set the number of callbacks to be registered
3376 in a given burst of a callback-flood test.
3378 rcutorture.fqs_duration= [KNL]
3379 Set duration of force_quiescent_state bursts
3382 rcutorture.fqs_holdoff= [KNL]
3383 Set holdoff time within force_quiescent_state bursts
3386 rcutorture.fqs_stutter= [KNL]
3387 Set wait time between force_quiescent_state bursts
3390 rcutorture.gp_cond= [KNL]
3391 Use conditional/asynchronous update-side
3392 primitives, if available.
3394 rcutorture.gp_exp= [KNL]
3395 Use expedited update-side primitives, if available.
3397 rcutorture.gp_normal= [KNL]
3398 Use normal (non-expedited) asynchronous
3399 update-side primitives, if available.
3401 rcutorture.gp_sync= [KNL]
3402 Use normal (non-expedited) synchronous
3403 update-side primitives, if available. If all
3404 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3405 rcutorture.gp_normal=, and rcutorture.gp_sync=
3406 are zero, rcutorture acts as if is interpreted
3407 they are all non-zero.
3409 rcutorture.n_barrier_cbs= [KNL]
3410 Set callbacks/threads for rcu_barrier() testing.
3412 rcutorture.nfakewriters= [KNL]
3413 Set number of concurrent RCU writers. These just
3414 stress RCU, they don't participate in the actual
3415 test, hence the "fake".
3417 rcutorture.nreaders= [KNL]
3418 Set number of RCU readers. The value -1 selects
3419 N-1, where N is the number of CPUs. A value
3420 "n" less than -1 selects N-n-2, where N is again
3421 the number of CPUs. For example, -2 selects N
3422 (the number of CPUs), -3 selects N+1, and so on.
3424 rcutorture.object_debug= [KNL]
3425 Enable debug-object double-call_rcu() testing.
3427 rcutorture.onoff_holdoff= [KNL]
3428 Set time (s) after boot for CPU-hotplug testing.
3430 rcutorture.onoff_interval= [KNL]
3431 Set time (s) between CPU-hotplug operations, or
3432 zero to disable CPU-hotplug testing.
3434 rcutorture.shuffle_interval= [KNL]
3435 Set task-shuffle interval (s). Shuffling tasks
3436 allows some CPUs to go into dyntick-idle mode
3437 during the rcutorture test.
3439 rcutorture.shutdown_secs= [KNL]
3440 Set time (s) after boot system shutdown. This
3441 is useful for hands-off automated testing.
3443 rcutorture.stall_cpu= [KNL]
3444 Duration of CPU stall (s) to test RCU CPU stall
3445 warnings, zero to disable.
3447 rcutorture.stall_cpu_holdoff= [KNL]
3448 Time to wait (s) after boot before inducing stall.
3450 rcutorture.stat_interval= [KNL]
3451 Time (s) between statistics printk()s.
3453 rcutorture.stutter= [KNL]
3454 Time (s) to stutter testing, for example, specifying
3455 five seconds causes the test to run for five seconds,
3456 wait for five seconds, and so on. This tests RCU's
3457 ability to transition abruptly to and from idle.
3459 rcutorture.test_boost= [KNL]
3460 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3461 "Maybe" means test if the RCU implementation
3462 under test support RCU priority boosting.
3464 rcutorture.test_boost_duration= [KNL]
3465 Duration (s) of each individual boost test.
3467 rcutorture.test_boost_interval= [KNL]
3468 Interval (s) between each boost test.
3470 rcutorture.test_no_idle_hz= [KNL]
3471 Test RCU's dyntick-idle handling. See also the
3472 rcutorture.shuffle_interval parameter.
3474 rcutorture.torture_runnable= [BOOT]
3475 Start rcutorture running at boot time.
3477 rcutorture.torture_type= [KNL]
3478 Specify the RCU implementation to test.
3480 rcutorture.verbose= [KNL]
3481 Enable additional printk() statements.
3483 rcupdate.rcu_cpu_stall_suppress= [KNL]
3484 Suppress RCU CPU stall warning messages.
3486 rcupdate.rcu_cpu_stall_timeout= [KNL]
3487 Set timeout for RCU CPU stall warning messages.
3489 rcupdate.rcu_expedited= [KNL]
3490 Use expedited grace-period primitives, for
3491 example, synchronize_rcu_expedited() instead
3492 of synchronize_rcu(). This reduces latency,
3493 but can increase CPU utilization, degrade
3494 real-time latency, and degrade energy efficiency.
3495 No effect on CONFIG_TINY_RCU kernels.
3497 rcupdate.rcu_normal= [KNL]
3498 Use only normal grace-period primitives,
3499 for example, synchronize_rcu() instead of
3500 synchronize_rcu_expedited(). This improves
3501 real-time latency, CPU utilization, and
3502 energy efficiency, but can expose users to
3503 increased grace-period latency. This parameter
3504 overrides rcupdate.rcu_expedited. No effect on
3505 CONFIG_TINY_RCU kernels.
3507 rcupdate.rcu_normal_after_boot= [KNL]
3508 Once boot has completed (that is, after
3509 rcu_end_inkernel_boot() has been invoked), use
3510 only normal grace-period primitives. No effect
3511 on CONFIG_TINY_RCU kernels.
3513 rcupdate.rcu_task_stall_timeout= [KNL]
3514 Set timeout in jiffies for RCU task stall warning
3515 messages. Disable with a value less than or equal
3518 rcupdate.rcu_self_test= [KNL]
3519 Run the RCU early boot self tests
3521 rcupdate.rcu_self_test_bh= [KNL]
3522 Run the RCU bh early boot self tests
3524 rcupdate.rcu_self_test_sched= [KNL]
3525 Run the RCU sched early boot self tests
3529 Run specified binary instead of /init from the ramdisk,
3530 used for early userspace startup. See initrd.
3533 Format (x86 or x86_64):
3534 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3536 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3538 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3539 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3540 reboot_force is either force or not specified,
3541 reboot_cpu is s[mp]#### with #### being the processor
3542 to be used for rebooting.
3545 [KNL, SMP] Set scheduler's default relax_domain_level.
3546 See Documentation/cgroup-v1/cpusets.txt.
3548 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3550 reservetop= [X86-32]
3552 Reserves a hole at the top of the kernel virtual
3557 Set the amount of memory to reserve for BIOS at
3558 the bottom of the address space.
3560 reset_devices [KNL] Force drivers to reset the underlying device
3561 during initialization.
3564 Specify the partition device for software suspend
3566 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3568 resume_offset= [SWSUSP]
3569 Specify the offset from the beginning of the partition
3570 given by "resume=" at which the swap header is located,
3571 in <PAGE_SIZE> units (needed only for swap files).
3572 See Documentation/power/swsusp-and-swap-files.txt
3574 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3575 read the resume files
3577 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3578 Useful for devices that are detected asynchronously
3579 (e.g. USB and MMC devices).
3581 hibernate= [HIBERNATION]
3582 noresume Don't check if there's a hibernation image
3583 present during boot.
3584 nocompress Don't compress/decompress hibernation images.
3585 no Disable hibernation and resume.
3586 protect_image Turn on image protection during restoration
3587 (that will set all pages holding image data
3588 during restoration read-only).
3590 retain_initrd [RAM] Keep initrd memory after extraction
3592 rfkill.default_state=
3593 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3594 etc. communication is blocked by default.
3597 rfkill.master_switch_mode=
3598 0 The "airplane mode" button does nothing.
3599 1 The "airplane mode" button toggles between everything
3600 blocked and the previous configuration.
3601 2 The "airplane mode" button toggles between everything
3602 blocked and everything unblocked.
3604 rhash_entries= [KNL,NET]
3605 Set number of hash buckets for route cache
3608 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
3611 ro [KNL] Mount root device read-only on boot
3614 on Mark read-only kernel memory as read-only (default).
3615 off Leave read-only kernel memory writable for debugging.
3618 Enable the uart passthrough on the designated usb port
3619 on Rockchip SoCs. When active, the signals of the
3620 debug-uart get routed to the D+ and D- pins of the usb
3621 port and the regular usb controller gets disabled.
3623 root= [KNL] Root filesystem
3624 See name_to_dev_t comment in init/do_mounts.c.
3626 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3627 mount the root filesystem
3629 rootflags= [KNL] Set root filesystem mount option string
3631 rootfstype= [KNL] Set root filesystem type
3633 rootwait [KNL] Wait (indefinitely) for root device to show up.
3634 Useful for devices that are detected asynchronously
3635 (e.g. USB and MMC devices).
3637 rproc_mem=nn[KMG][@address]
3638 [KNL,ARM,CMA] Remoteproc physical memory block.
3639 Memory area to be used by remote processor image,
3642 rw [KNL] Mount root device read-write on boot
3644 S [KNL] Run init in single mode
3646 s390_iommu= [HW,S390]
3647 Set s390 IOTLB flushing mode
3649 With strict flushing every unmap operation will result in
3650 an IOTLB flush. Default is lazy flushing before reuse,
3654 See drivers/net/irda/sa1100_ir.c.
3656 sbni= [NET] Granch SBNI12 leased line adapter
3658 sched_debug [KNL] Enables verbose scheduler debug messages.
3660 schedstats= [KNL,X86] Enable or disable scheduled statistics.
3661 Allowed values are enable and disable. This feature
3662 incurs a small amount of overhead in the scheduler
3663 but is useful for debugging and performance tuning.
3665 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3666 xtime_lock contention on larger systems, and/or RCU lock
3667 contention on all systems with CONFIG_MAXSMP set.
3668 Format: { "0" | "1" }
3669 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3671 Note: increases power consumption, thus should only be
3672 enabled if running jitter sensitive (HPC/RT) workloads.
3674 security= [SECURITY] Choose a security module to enable at boot.
3675 If this boot parameter is not specified, only the first
3676 security module asking for security registration will be
3677 loaded. An invalid security module name will be treated
3678 as if no module has been chosen.
3680 selinux= [SELINUX] Disable or enable SELinux at boot time.
3681 Format: { "0" | "1" }
3682 See security/selinux/Kconfig help text.
3685 Default value is set via kernel config option.
3686 If enabled at boot time, /selinux/disable can be used
3687 later to disable prior to initial policy load.
3689 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3690 Format: { "0" | "1" }
3691 See security/apparmor/Kconfig help text
3694 Default value is set via kernel config option.
3696 serialnumber [BUGS=X86-32]
3699 Maximal number of shapers.
3707 Disable merging of slabs with similar size. May be
3708 necessary if there is some reason to distinguish
3709 allocs to different slabs. Debug options disable
3710 merging on their own.
3711 For more information see Documentation/vm/slub.txt.
3713 slab_max_order= [MM, SLAB]
3714 Determines the maximum allowed order for slabs.
3715 A high setting may cause OOMs due to memory
3716 fragmentation. Defaults to 1 for systems with
3717 more than 32MB of RAM, 0 otherwise.
3719 slub_debug[=options[,slabs]] [MM, SLUB]
3720 Enabling slub_debug allows one to determine the
3721 culprit if slab objects become corrupted. Enabling
3722 slub_debug can create guard zones around objects and
3723 may poison objects when not in use. Also tracks the
3724 last alloc / free. For more information see
3725 Documentation/vm/slub.txt.
3727 slub_memcg_sysfs= [MM, SLUB]
3728 Determines whether to enable sysfs directories for
3729 memory cgroup sub-caches. 1 to enable, 0 to disable.
3730 The default is determined by CONFIG_SLUB_MEMCG_SYSFS_ON.
3731 Enabling this can lead to a very high number of debug
3732 directories and files being created under
3735 slub_max_order= [MM, SLUB]
3736 Determines the maximum allowed order for slabs.
3737 A high setting may cause OOMs due to memory
3738 fragmentation. For more information see
3739 Documentation/vm/slub.txt.
3741 slub_min_objects= [MM, SLUB]
3742 The minimum number of objects per slab. SLUB will
3743 increase the slab order up to slub_max_order to
3744 generate a sufficiently large slab able to contain
3745 the number of objects indicated. The higher the number
3746 of objects the smaller the overhead of tracking slabs
3747 and the less frequently locks need to be acquired.
3748 For more information see Documentation/vm/slub.txt.
3750 slub_min_order= [MM, SLUB]
3751 Determines the minimum page order for slabs. Must be
3752 lower than slub_max_order.
3753 For more information see Documentation/vm/slub.txt.
3755 slub_nomerge [MM, SLUB]
3756 Same with slab_nomerge. This is supported for legacy.
3757 See slab_nomerge for more information.
3760 Format: <io1>[,<io2>[,...,<io8>]]
3762 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3763 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3764 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3765 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3766 smsc-ircc2.ircc_irq= [HW] IRQ line
3767 smsc-ircc2.ircc_dma= [HW] DMA channel
3768 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3769 0: Toshiba Satellite 1800 (GP data pin select)
3770 1: Fast pin select (default)
3773 smt [KNL,S390] Set the maximum number of threads (logical
3774 CPUs) to use per physical CPU on systems capable of
3775 symmetric multithreading (SMT). Will be capped to the
3776 actual hardware limit.
3778 Default: -1 (no limit)
3781 [KNL] Should the soft-lockup detector generate panics.
3784 softlockup_all_cpu_backtrace=
3785 [KNL] Should the soft-lockup detector generate
3786 backtraces on all cpus.
3789 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3790 See Documentation/laptops/sonypi.txt
3792 spia_io_base= [HW,MTD]
3797 srcutree.exp_holdoff [KNL]
3798 Specifies how many nanoseconds must elapse
3799 since the end of the last SRCU grace period for
3800 a given srcu_struct until the next normal SRCU
3801 grace period will be considered for automatic
3802 expediting. Set to zero to disable automatic
3806 Enabled the stack tracer on boot up.
3808 stacktrace_filter=[function-list]
3809 [FTRACE] Limit the functions that the stack tracer
3810 will trace at boot up. function-list is a comma separated
3811 list of functions. This list can be changed at run
3812 time by the stack_trace_filter file in the debugfs
3813 tracing directory. Note, this enables stack tracing
3814 and the stacktrace above is not needed.
3818 Set the STI (builtin display/keyboard on the HP-PARISC
3819 machines) console (graphic card) which should be used
3820 as the initial boot-console.
3821 See also comment in drivers/video/console/sticore.c.
3824 See comment in drivers/video/console/sticore.c.
3827 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3829 sunrpc.min_resvport=
3830 sunrpc.max_resvport=
3832 SunRPC servers often require that client requests
3833 originate from a privileged port (i.e. a port in the
3834 range 0 < portnr < 1024).
3835 An administrator who wishes to reserve some of these
3836 ports for other uses may adjust the range that the
3837 kernel's sunrpc client considers to be privileged
3838 using these two parameters to set the minimum and
3839 maximum port values.
3841 sunrpc.svc_rpc_per_connection_limit=
3843 Limit the number of requests that the server will
3844 process in parallel from a single connection.
3845 The default value is 0 (no limit).
3849 Control how the NFS server code allocates CPUs to
3850 service thread pools. Depending on how many NICs
3851 you have and where their interrupts are bound, this
3852 option will affect which CPUs will do NFS serving.
3853 Note: this parameter cannot be changed while the
3854 NFS server is running.
3856 auto the server chooses an appropriate mode
3857 automatically using heuristics
3858 global a single global pool contains all CPUs
3859 percpu one pool for each CPU
3860 pernode one pool for each NUMA node (equivalent
3861 to global on non-NUMA machines)
3863 sunrpc.tcp_slot_table_entries=
3864 sunrpc.udp_slot_table_entries=
3866 Sets the upper limit on the number of simultaneous
3867 RPC calls that can be sent from the client to a
3868 server. Increasing these values may allow you to
3869 improve throughput, but will also increase the
3870 amount of memory reserved for use by the client.
3872 suspend.pm_test_delay=
3874 Sets the number of seconds to remain in a suspend test
3875 mode before resuming the system (see
3876 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3877 is set. Default value is 5.
3880 [KNL] Enable accounting of swap in memory resource
3881 controller if no parameter or 1 is given or disable
3882 it if 0 is given (See Documentation/cgroup-v1/memory.txt)
3884 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3885 Format: { <int> | force | noforce }
3886 <int> -- Number of I/O TLB slabs
3887 force -- force using of bounce buffers even if they
3888 wouldn't be automatically used by the kernel
3889 noforce -- Never use bounce buffers (for debugging)
3893 sysfs.deprecated=0|1 [KNL]
3894 Enable/disable old style sysfs layout for old udev
3895 on older distributions. When this option is enabled
3896 very new udev will not work anymore. When this option
3897 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3898 in older udev will not work anymore.
3899 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3900 the kernel configuration.
3902 sysrq_always_enabled
3904 Ignore sysrq setting - this boot parameter will
3905 neutralize any effect of /proc/sys/kernel/sysrq.
3906 Useful for debugging.
3908 tcpmhash_entries= [KNL,NET]
3909 Set the number of tcp_metrics_hash slots.
3910 Default value is 8192 or 16384 depending on total
3911 ram pages. This is used to specify the TCP metrics
3912 cache size. See Documentation/networking/ip-sysctl.txt
3913 "tcp_no_metrics_save" section for more details.
3917 test_suspend= [SUSPEND][,N]
3918 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3919 standby suspend) or "freeze" (for suspend type freeze)
3920 as the system sleep state during system startup with
3921 the optional capability to repeat N number of times.
3922 The system is woken from this state using a
3923 wakeup-capable RTC alarm.
3925 thash_entries= [KNL,NET]
3926 Set number of hash buckets for TCP connection
3928 thermal.act= [HW,ACPI]
3929 -1: disable all active trip points in all thermal zones
3930 <degrees C>: override all lowest active trip points
3932 thermal.crt= [HW,ACPI]
3933 -1: disable all critical trip points in all thermal zones
3934 <degrees C>: override all critical trip points
3936 thermal.nocrt= [HW,ACPI]
3937 Set to disable actions on ACPI thermal zone
3938 critical and hot trip points.
3940 thermal.off= [HW,ACPI]
3941 1: disable ACPI thermal control
3943 thermal.psv= [HW,ACPI]
3944 -1: disable all passive trip points
3945 <degrees C>: override all passive trip points to this
3948 thermal.tzp= [HW,ACPI]
3949 Specify global default ACPI thermal zone polling rate
3950 <deci-seconds>: poll all this frequency
3951 0: no polling (default)
3954 Force threading of all interrupt handlers except those
3955 marked explicitly IRQF_NO_THREAD.
3958 Enable the Transcendent memory driver if built-in.
3960 tmem.cleancache=0|1 [KNL, XEN]
3961 Default is on (1). Disable the usage of the cleancache
3962 API to send anonymous pages to the hypervisor.
3964 tmem.frontswap=0|1 [KNL, XEN]
3965 Default is on (1). Disable the usage of the frontswap
3966 API to send swap pages to the hypervisor. If disabled
3967 the selfballooning and selfshrinking are force disabled.
3969 tmem.selfballooning=0|1 [KNL, XEN]
3970 Default is on (1). Disable the driving of swap pages
3973 tmem.selfshrinking=0|1 [KNL, XEN]
3974 Default is on (1). Partial swapoff that immediately
3975 transfers pages from Xen hypervisor back to the
3976 kernel based on different criteria.
3980 Specify if the kernel should make use of the cpu
3981 topology information if the hardware supports this.
3982 The scheduler will make use of this information and
3983 e.g. base its process migration decisions on it.
3986 topology_updates= [KNL, PPC, NUMA]
3988 Specify if the kernel should ignore (off)
3989 topology updates sent by the hypervisor to this
3994 tpm_suspend_pcr=[HW,TPM]
3995 Format: integer pcr id
3996 Specify that at suspend time, the tpm driver
3997 should extend the specified pcr with zeros,
3998 as a workaround for some chips which fail to
3999 flush the last written pcr on TPM_SaveState.
4000 This will guarantee that all the other pcrs
4003 trace_buf_size=nn[KMG]
4004 [FTRACE] will set tracing buffer size on each cpu.
4006 trace_event=[event-list]
4007 [FTRACE] Set and start specified trace events in order
4008 to facilitate early boot debugging. The event-list is a
4009 comma separated list of trace events to enable. See
4010 also Documentation/trace/events.txt
4012 trace_options=[option-list]
4013 [FTRACE] Enable or disable tracer options at boot.
4014 The option-list is a comma delimited list of options
4015 that can be enabled or disabled just as if you were
4016 to echo the option name into
4018 /sys/kernel/debug/tracing/trace_options
4020 For example, to enable stacktrace option (to dump the
4021 stack trace of each event), add to the command line:
4023 trace_options=stacktrace
4025 See also Documentation/trace/ftrace.txt "trace options"
4029 Have the tracepoints sent to printk as well as the
4030 tracing ring buffer. This is useful for early boot up
4031 where the system hangs or reboots and does not give the
4032 option for reading the tracing buffer or performing a
4033 ftrace_dump_on_oops.
4035 To turn off having tracepoints sent to printk,
4036 echo 0 > /proc/sys/kernel/tracepoint_printk
4037 Note, echoing 1 into this file without the
4038 tracepoint_printk kernel cmdline option has no effect.
4042 Having tracepoints sent to printk() and activating high
4043 frequency tracepoints such as irq or sched, can cause
4044 the system to live lock.
4047 [FTRACE] enable this option to disable tracing when a
4048 warning is hit. This turns off "tracing_on". Tracing can
4049 be enabled again by echoing '1' into the "tracing_on"
4050 file located in /sys/kernel/debug/tracing/
4052 This option is useful, as it disables the trace before
4053 the WARNING dump is called, which prevents the trace to
4054 be filled with content caused by the warning output.
4056 This option can also be set at run time via the sysctl
4057 option: kernel/traceoff_on_warning
4059 transparent_hugepage=
4061 Format: [always|madvise|never]
4062 Can be used to control the default behavior of the system
4063 with respect to transparent hugepages.
4064 See Documentation/vm/transhuge.txt for more details.
4066 tsc= Disable clocksource stability checks for TSC.
4068 [x86] reliable: mark tsc clocksource as reliable, this
4069 disables clocksource verification at runtime, as well
4070 as the stability checks done at bootup. Used to enable
4071 high-resolution timer mode on older hardware, and in
4072 virtualized environment.
4073 [x86] noirqtime: Do not use TSC to do irq accounting.
4074 Used to run time disable IRQ_TIME_ACCOUNTING on any
4075 platforms where RDTSC is slow and this accounting
4078 turbografx.map[2|3]= [HW,JOY]
4079 TurboGraFX parallel port interface
4081 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
4082 See also Documentation/input/joystick-parport.txt
4084 udbg-immortal [PPC] When debugging early kernel crashes that
4085 happen after console_init() and before a proper
4086 console driver takes over, this boot options might
4087 help "seeing" what's going on.
4089 uhash_entries= [KNL,NET]
4090 Set number of hash buckets for UDP/UDP-Lite connections
4093 [USB] Ignore overcurrent events (default N).
4094 Some badly-designed motherboards generate lots of
4095 bogus events, for ports that aren't wired to
4096 anything. Set this parameter to avoid log spamming.
4097 Note that genuine overcurrent events won't be
4101 [X86] Cause panic on unknown NMI.
4103 usbcore.authorized_default=
4104 [USB] Default USB device authorization:
4105 (default -1 = authorized except for wireless USB,
4106 0 = not authorized, 1 = authorized)
4108 usbcore.autosuspend=
4109 [USB] The autosuspend time delay (in seconds) used
4110 for newly-detected USB devices (default 2). This
4111 is the time required before an idle device will be
4112 autosuspended. Devices for which the delay is set
4113 to a negative value won't be autosuspended at all.
4115 usbcore.usbfs_snoop=
4116 [USB] Set to log all usbfs traffic (default 0 = off).
4118 usbcore.usbfs_snoop_max=
4119 [USB] Maximum number of bytes to snoop in each URB
4122 usbcore.blinkenlights=
4123 [USB] Set to cycle leds on hubs (default 0 = off).
4125 usbcore.old_scheme_first=
4126 [USB] Start with the old device initialization
4127 scheme (default 0 = off).
4129 usbcore.usbfs_memory_mb=
4130 [USB] Memory limit (in MB) for buffers allocated by
4131 usbfs (default = 16, 0 = max = 2047).
4133 usbcore.use_both_schemes=
4134 [USB] Try the other device initialization scheme
4135 if the first one fails (default 1 = enabled).
4137 usbcore.initial_descriptor_timeout=
4138 [USB] Specifies timeout for the initial 64-byte
4139 USB_REQ_GET_DESCRIPTOR request in milliseconds
4140 (default 5000 = 5.0 seconds).
4142 usbcore.nousb [USB] Disable the USB subsystem
4145 [USBHID] The interval which mice are to be polled at.
4148 [USBHID] The interval which joysticks are to be polled at.
4150 usb-storage.delay_use=
4151 [UMS] The delay in seconds before a new device is
4152 scanned for Logical Units (default 1).
4155 [UMS] A list of quirks entries to supplement or
4156 override the built-in unusual_devs list. List
4157 entries are separated by commas. Each entry has
4158 the form VID:PID:Flags where VID and PID are Vendor
4159 and Product ID values (4-digit hex numbers) and
4160 Flags is a set of characters, each corresponding
4161 to a common usb-storage quirk flag as follows:
4162 a = SANE_SENSE (collect more than 18 bytes
4164 b = BAD_SENSE (don't collect more than 18
4165 bytes of sense data);
4166 c = FIX_CAPACITY (decrease the reported
4167 device capacity by one sector);
4168 d = NO_READ_DISC_INFO (don't use
4169 READ_DISC_INFO command);
4170 e = NO_READ_CAPACITY_16 (don't use
4171 READ_CAPACITY_16 command);
4172 f = NO_REPORT_OPCODES (don't use report opcodes
4174 g = MAX_SECTORS_240 (don't transfer more than
4175 240 sectors at a time, uas only);
4176 h = CAPACITY_HEURISTICS (decrease the
4177 reported device capacity by one
4178 sector if the number is odd);
4179 i = IGNORE_DEVICE (don't bind to this
4181 j = NO_REPORT_LUNS (don't use report luns
4183 l = NOT_LOCKABLE (don't try to lock and
4184 unlock ejectable media);
4185 m = MAX_SECTORS_64 (don't transfer more
4186 than 64 sectors = 32 KB at a time);
4187 n = INITIAL_READ10 (force a retry of the
4188 initial READ(10) command);
4189 o = CAPACITY_OK (accept the capacity
4190 reported by the device);
4191 p = WRITE_CACHE (the device cache is ON
4193 r = IGNORE_RESIDUE (the device reports
4194 bogus residue values);
4195 s = SINGLE_LUN (the device has only one
4197 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4198 commands, uas only);
4199 u = IGNORE_UAS (don't bind to the uas driver);
4200 w = NO_WP_DETECT (don't test whether the
4201 medium is write-protected).
4202 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
4203 even if the device claims no cache)
4204 Example: quirks=0419:aaf5:rl,0421:0433:rc
4206 user_debug= [KNL,ARM]
4208 See arch/arm/Kconfig.debug help text.
4209 1 - undefined instruction events
4211 4 - invalid data aborts
4214 Example: user_debug=31
4217 [X86] Flags controlling user PTE allocations.
4219 nohigh = do not allocate PTE pages in
4220 HIGHMEM regardless of setting
4224 On X86_32, this is an alias for vdso32=. Otherwise:
4226 vdso=1: enable VDSO (the default)
4227 vdso=0: disable VDSO mapping
4229 vdso32= [X86] Control the 32-bit vDSO
4230 vdso32=1: enable 32-bit VDSO
4231 vdso32=0 or vdso32=2: disable 32-bit VDSO
4233 See the help text for CONFIG_COMPAT_VDSO for more
4234 details. If CONFIG_COMPAT_VDSO is set, the default is
4235 vdso32=0; otherwise, the default is vdso32=1.
4237 For compatibility with older kernels, vdso32=2 is an
4240 Try vdso32=0 if you encounter an error that says:
4241 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
4244 vector=percpu: enable percpu vector domain
4246 video= [FB] Frame buffer configuration
4247 See Documentation/fb/modedb.txt.
4249 video.brightness_switch_enabled= [0,1]
4250 If set to 1, on receiving an ACPI notify event
4251 generated by hotkey, video driver will adjust brightness
4252 level and then send out the event to user space through
4253 the allocated input device; If set to 0, video driver
4254 will only send out the event without touching backlight
4259 [VMMIO] Memory mapped virtio (platform) device.
4261 <size>@<baseaddr>:<irq>[:<id>]
4263 <size> := size (can use standard suffixes
4265 <baseaddr> := physical base address
4266 <irq> := interrupt number (as passed to
4268 <id> := (optional) platform device id
4270 virtio_mmio.device=1K@0x100b0000:48:7
4272 Can be used multiple times for multiple devices.
4274 vga= [BOOT,X86-32] Select a particular video mode
4275 See Documentation/x86/boot.txt and
4276 Documentation/svga.txt.
4277 Use vga=ask for menu.
4278 This is actually a boot loader parameter; the value is
4279 passed to the kernel using a special protocol.
4281 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4282 size of <nn>. This can be used to increase the
4283 minimum size (128MB on x86). It can also be used to
4284 decrease the size and leave more room for directly
4287 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4290 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4293 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4297 Controls the behavior of vsyscalls (i.e. calls to
4298 fixed addresses of 0xffffffffff600x00 from legacy
4299 code). Most statically-linked binaries and older
4300 versions of glibc use these calls. Because these
4301 functions are at fixed addresses, they make nice
4302 targets for exploits that can control RIP.
4304 emulate [default] Vsyscalls turn into traps and are
4305 emulated reasonably safely.
4307 native Vsyscalls are native syscall instructions.
4308 This is a little bit faster than trapping
4309 and makes a few dynamic recompilers work
4310 better than they would in emulation mode.
4311 It also makes exploits much easier to write.
4313 none Vsyscalls don't work at all. This makes
4314 them quite hard to use for exploits but
4315 might break your system.
4317 vt.color= [VT] Default text color.
4318 Format: 0xYX, X = foreground, Y = background.
4319 Default: 0x07 = light gray on black.
4321 vt.cur_default= [VT] Default cursor shape.
4322 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4323 the parameters of the <Esc>[?A;B;Cc escape sequence;
4324 see VGA-softcursor.txt. Default: 2 = underline.
4326 vt.default_blu= [VT]
4327 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4328 Change the default blue palette of the console.
4329 This is a 16-member array composed of values
4332 vt.default_grn= [VT]
4333 Format: <green0>,<green1>,<green2>,...,<green15>
4334 Change the default green palette of the console.
4335 This is a 16-member array composed of values
4338 vt.default_red= [VT]
4339 Format: <red0>,<red1>,<red2>,...,<red15>
4340 Change the default red palette of the console.
4341 This is a 16-member array composed of values
4347 Set system-wide default UTF-8 mode for all tty's.
4348 Default is 1, i.e. UTF-8 mode is enabled for all
4349 newly opened terminals.
4351 vt.global_cursor_default=
4354 Set system-wide default for whether a cursor
4355 is shown on new VTs. Default is -1,
4356 i.e. cursors will be created by default unless
4357 overridden by individual drivers. 0 will hide
4358 cursors, 1 will display them.
4360 vt.italic= [VT] Default color for italic text; 0-15.
4363 vt.underline= [VT] Default color for underlined text; 0-15.
4366 watchdog timers [HW,WDT] For information on watchdog timers,
4367 see Documentation/watchdog/watchdog-parameters.txt
4368 or other driver-specific files in the
4369 Documentation/watchdog/ directory.
4371 workqueue.watchdog_thresh=
4372 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4373 warn stall conditions and dump internal state to
4374 help debugging. 0 disables workqueue stall
4375 detection; otherwise, it's the stall threshold
4376 duration in seconds. The default value is 30 and
4377 it can be updated at runtime by writing to the
4378 corresponding sysfs file.
4380 workqueue.disable_numa
4381 By default, all work items queued to unbound
4382 workqueues are affine to the NUMA nodes they're
4383 issued on, which results in better behavior in
4384 general. If NUMA affinity needs to be disabled for
4385 whatever reason, this option can be used. Note
4386 that this also can be controlled per-workqueue for
4387 workqueues visible under /sys/bus/workqueue/.
4389 workqueue.power_efficient
4390 Per-cpu workqueues are generally preferred because
4391 they show better performance thanks to cache
4392 locality; unfortunately, per-cpu workqueues tend to
4393 be more power hungry than unbound workqueues.
4395 Enabling this makes the per-cpu workqueues which
4396 were observed to contribute significantly to power
4397 consumption unbound, leading to measurably lower
4398 power usage at the cost of small performance
4401 The default value of this parameter is determined by
4402 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4404 workqueue.debug_force_rr_cpu
4405 Workqueue used to implicitly guarantee that work
4406 items queued without explicit CPU specified are put
4407 on the local CPU. This guarantee is no longer true
4408 and while local CPU is still preferred work items
4409 may be put on foreign CPUs. This debug option
4410 forces round-robin CPU selection to flush out
4411 usages which depend on the now broken guarantee.
4412 When enabled, memory and cache locality will be
4415 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4416 default x2apic cluster mode on platforms
4419 x86_intel_mid_timer= [X86-32,APBT]
4420 Choose timer option for x86 Intel MID platform.
4421 Two valid options are apbt timer only and lapic timer
4422 plus one apbt timer for broadcast timer.
4423 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4425 xen_512gb_limit [KNL,X86-64,XEN]
4426 Restricts the kernel running paravirtualized under Xen
4427 to use only up to 512 GB of RAM. The reason to do so is
4428 crash analysis tools and Xen tools for doing domain
4429 save/restore/migration must be enabled to handle larger
4432 xen_emul_unplug= [HW,X86,XEN]
4433 Unplug Xen emulated devices
4434 Format: [unplug0,][unplug1]
4435 ide-disks -- unplug primary master IDE devices
4436 aux-ide-disks -- unplug non-primary-master IDE devices
4437 nics -- unplug network devices
4438 all -- unplug all emulated devices (NICs and IDE disks)
4439 unnecessary -- unplugging emulated devices is
4440 unnecessary even if the host did not respond to
4442 never -- do not unplug even if version check succeeds
4444 xen_nopvspin [X86,XEN]
4445 Disables the ticketlock slowpath using Xen PV
4449 Disables the PV optimizations forcing the HVM guest to
4450 run as generic HVM guest with no PV drivers.
4452 xirc2ps_cs= [NET,PCMCIA]
4454 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
git.samba.org / sfrench / cifs-2.6.git / blob