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.
870 Format: {"off" | "known"}
871 Control how the dt_cpu_ftrs device-tree binding is
872 used for CPU feature discovery and setup (if it
874 off: Do not use it, fall back to legacy cpu table.
875 known: Do not pass through unknown features to guests
876 or userspace, only those that the kernel is aware of.
878 dump_apple_properties [X86]
879 Dump name and content of EFI device properties on
880 x86 Macs. Useful for driver authors to determine
881 what data is available or for reverse-engineering.
883 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
884 module.dyndbg[="val"]
885 Enable debug messages at boot time. See
886 Documentation/dynamic-debug-howto.txt for details.
888 nompx [X86] Disables Intel Memory Protection Extensions.
889 See Documentation/x86/intel_mpx.txt for more
890 information about the feature.
892 nopku [X86] Disable Memory Protection Keys CPU feature found
895 module.async_probe [KNL]
896 Enable asynchronous probe on this module.
898 early_ioremap_debug [KNL]
899 Enable debug messages in early_ioremap support. This
900 is useful for tracking down temporary early mappings
901 which are not unmapped.
903 earlycon= [KNL] Output early console device and options.
905 When used with no options, the early console is
906 determined by the stdout-path property in device
909 cdns,<addr>[,options]
910 Start an early, polled-mode console on a Cadence
911 (xuartps) serial port at the specified address. Only
912 supported option is baud rate. If baud rate is not
913 specified, the serial port must already be setup and
916 uart[8250],io,<addr>[,options]
917 uart[8250],mmio,<addr>[,options]
918 uart[8250],mmio32,<addr>[,options]
919 uart[8250],mmio32be,<addr>[,options]
920 uart[8250],0x<addr>[,options]
921 Start an early, polled-mode console on the 8250/16550
922 UART at the specified I/O port or MMIO address.
923 MMIO inter-register address stride is either 8-bit
924 (mmio) or 32-bit (mmio32 or mmio32be).
925 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
926 to be equivalent to 'mmio'. 'options' are specified
927 in the same format described for "console=ttyS<n>"; if
928 unspecified, the h/w is not initialized.
932 Start an early, polled-mode console on a pl011 serial
933 port at the specified address. The pl011 serial port
934 must already be setup and configured. Options are not
935 yet supported. If 'mmio32' is specified, then only
936 the driver will use only 32-bit accessors to read/write
937 the device registers.
940 Start an early, polled-mode console on a meson serial
941 port at the specified address. The serial port must
942 already be setup and configured. Options are not yet
946 Start an early, polled-mode console on an msm serial
947 port at the specified address. The serial port
948 must already be setup and configured. Options are not
952 Start an early, polled-mode console on an msm serial
953 dm port at the specified address. The serial port
954 must already be setup and configured. Options are not
957 smh Use ARM semihosting calls for early console.
965 Use early console provided by serial driver available
966 on Samsung SoCs, requires selecting proper type and
967 a correct base address of the selected UART port. The
968 serial port must already be setup and configured.
969 Options are not yet supported.
972 Start an early, polled-mode console on a lantiq serial
973 (lqasc) port at the specified address. The serial port
974 must already be setup and configured. Options are not
979 Use early console provided by Freescale LP UART driver
980 found on Freescale Vybrid and QorIQ LS1021A processors.
981 A valid base address must be provided, and the serial
982 port must already be setup and configured.
985 Start an early, polled-mode console on the
986 Armada 3700 serial port at the specified
987 address. The serial port must already be setup
988 and configured. Options are not yet supported.
990 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k,S390]
995 earlyprintk=serial[,ttySn[,baudrate]]
996 earlyprintk=serial[,0x...[,baudrate]]
997 earlyprintk=ttySn[,baudrate]
998 earlyprintk=dbgp[debugController#]
999 earlyprintk=pciserial,bus:device.function[,baudrate]
1000 earlyprintk=xdbc[xhciController#]
1002 earlyprintk is useful when the kernel crashes before
1003 the normal console is initialized. It is not enabled by
1004 default because it has some cosmetic problems.
1006 Append ",keep" to not disable it when the real console
1009 Only one of vga, efi, serial, or usb debug port can
1012 Currently only ttyS0 and ttyS1 may be specified by
1013 name. Other I/O ports may be explicitly specified
1014 on some architectures (x86 and arm at least) by
1015 replacing ttySn with an I/O port address, like this:
1016 earlyprintk=serial,0x1008,115200
1017 You can find the port for a given device in
1018 /proc/tty/driver/serial:
1019 2: uart:ST16650V2 port:00001008 irq:18 ...
1021 Interaction with the standard serial driver is not
1024 The VGA and EFI output is eventually overwritten by
1027 The xen output can only be used by Xen PV guests.
1029 The sclp output can only be used on s390.
1031 edac_report= [HW,EDAC] Control how to report EDAC event
1032 Format: {"on" | "off" | "force"}
1033 on: enable EDAC to report H/W event. May be overridden
1034 by other higher priority error reporting module.
1035 off: disable H/W event reporting through EDAC.
1036 force: enforce the use of EDAC to report H/W event.
1039 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1042 This is designed to be used in conjunction with
1043 the boot argument: earlyprintk=vga
1046 Format: {"off" | "on" | "skip[mbr]"}
1049 Format: { "old_map", "nochunk", "noruntime", "debug" }
1050 old_map [X86-64]: switch to the old ioremap-based EFI
1051 runtime services mapping. 32-bit still uses this one by
1053 nochunk: disable reading files in "chunks" in the EFI
1054 boot stub, as chunking can cause problems with some
1055 firmware implementations.
1056 noruntime : disable EFI runtime services support
1057 debug: enable misc debug output
1059 efi_no_storage_paranoia [EFI; X86]
1060 Using this parameter you can use more than 50% of
1061 your efi variable storage. Use this parameter only if
1062 you are really sure that your UEFI does sane gc and
1063 fulfills the spec otherwise your board may brick.
1065 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1066 Add arbitrary attribute to specific memory range by
1067 updating original EFI memory map.
1068 Region of memory which aa attribute is added to is
1070 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1071 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1072 attribute is added to range 0x100000000-0x180000000 and
1073 0x10a0000000-0x1120000000.
1075 Using this parameter you can do debugging of EFI memmap
1076 related feature. For example, you can do debugging of
1077 Address Range Mirroring feature even if your box
1080 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1081 that is to be dynamically loaded by Linux. If there are
1082 multiple variables with the same name but with different
1083 vendor GUIDs, all of them will be loaded. See
1084 Documentation/acpi/ssdt-overlays.txt for details.
1087 eisa_irq_edge= [PARISC,HW]
1088 See header of drivers/parisc/eisa.c.
1091 See comment before function elanfreq_setup() in
1092 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1095 Format: {"cfq" | "deadline" | "noop"}
1096 See Documentation/block/cfq-iosched.txt and
1097 Documentation/block/deadline-iosched.txt for details.
1099 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1100 Specifies physical address of start of kernel core
1101 image elf header and optionally the size. Generally
1102 kexec loader will pass this option to capture kernel.
1103 See Documentation/kdump/kdump.txt for details.
1105 enable_mtrr_cleanup [X86]
1106 The kernel tries to adjust MTRR layout from continuous
1107 to discrete, to make X server driver able to add WB
1108 entry later. This parameter enables that.
1110 enable_timer_pin_1 [X86]
1111 Enable PIN 1 of APIC timer
1112 Can be useful to work around chipset bugs
1113 (in particular on some ATI chipsets).
1114 The kernel tries to set a reasonable default.
1116 enforcing [SELINUX] Set initial enforcing status.
1118 See security/selinux/Kconfig help text.
1119 0 -- permissive (log only, no denials).
1120 1 -- enforcing (deny and log).
1122 Value can be changed at runtime via /selinux/enforce.
1125 Disable Error Record Serialization Table (ERST)
1128 ether= [HW,NET] Ethernet cards parameters
1129 This option is obsoleted by the "netdev=" option, which
1130 has equivalent usage. See its documentation for details.
1134 Permit 'security.evm' to be updated regardless of
1135 current integrity status.
1139 fail_make_request=[KNL]
1140 General fault injection mechanism.
1141 Format: <interval>,<probability>,<space>,<times>
1142 See also Documentation/fault-injection/.
1145 See Documentation/blockdev/floppy.txt.
1147 force_pal_cache_flush
1148 [IA-64] Avoid check_sal_cache_flush which may hang on
1149 buggy SAL_CACHE_FLUSH implementations. Using this
1150 parameter will force ia64_sal_cache_flush to call
1151 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1154 Forcefully enable Physical Address Extension (PAE).
1155 Many Pentium M systems disable PAE but may have a
1156 functionally usable PAE implementation.
1157 Warning: use of this parameter will taint the kernel
1158 and may cause unknown problems.
1161 [FTRACE] will set and start the specified tracer
1162 as early as possible in order to facilitate early
1165 ftrace_dump_on_oops[=orig_cpu]
1166 [FTRACE] will dump the trace buffers on oops.
1167 If no parameter is passed, ftrace will dump
1168 buffers of all CPUs, but if you pass orig_cpu, it will
1169 dump only the buffer of the CPU that triggered the
1172 ftrace_filter=[function-list]
1173 [FTRACE] Limit the functions traced by the function
1174 tracer at boot up. function-list is a comma separated
1175 list of functions. This list can be changed at run
1176 time by the set_ftrace_filter file in the debugfs
1179 ftrace_notrace=[function-list]
1180 [FTRACE] Do not trace the functions specified in
1181 function-list. This list can be changed at run time
1182 by the set_ftrace_notrace file in the debugfs
1185 ftrace_graph_filter=[function-list]
1186 [FTRACE] Limit the top level callers functions traced
1187 by the function graph tracer at boot up.
1188 function-list is a comma separated list of functions
1189 that can be changed at run time by the
1190 set_graph_function file in the debugfs tracing directory.
1192 ftrace_graph_notrace=[function-list]
1193 [FTRACE] Do not trace from the functions specified in
1194 function-list. This list is a comma separated list of
1195 functions that can be changed at run time by the
1196 set_graph_notrace file in the debugfs tracing directory.
1198 ftrace_graph_max_depth=<uint>
1199 [FTRACE] Used with the function graph tracer. This is
1200 the max depth it will trace into a function. This value
1201 can be changed at run time by the max_graph_depth file
1202 in the tracefs tracing directory. default: 0 (no limit)
1205 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1206 support via parallel port (up to 5 devices per port)
1207 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1208 See also Documentation/input/joystick-parport.txt
1212 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1216 gcov_persist= [GCOV] When non-zero (default), profiling data for
1217 kernel modules is saved and remains accessible via
1218 debugfs, even when the module is unloaded/reloaded.
1219 When zero, profiling data is discarded and associated
1220 debugfs files are removed at module unload time.
1222 goldfish [X86] Enable the goldfish android emulator platform.
1223 Don't use this when you are not running on the
1226 gpt [EFI] Forces disk with valid GPT signature but
1227 invalid Protective MBR to be treated as GPT. If the
1228 primary GPT is corrupted, it enables the backup/alternate
1229 GPT to be used instead.
1231 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1232 the "Enable 0" bit of the configuration register.
1235 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1236 the "Enable 0" bit of the configuration register.
1239 grcan.select= [HW] Select which physical interface to use.
1242 grcan.txsize= [HW] Sets the size of the tx buffer.
1243 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1245 grcan.rxsize= [HW] Sets the size of the rx buffer.
1246 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1249 gpio-mockup.gpio_mockup_ranges
1250 [HW] Sets the ranges of gpiochip of for this device.
1251 Format: <start1>,<end1>,<start2>,<end2>...
1253 hardlockup_all_cpu_backtrace=
1254 [KNL] Should the hard-lockup detector generate
1255 backtraces on all cpus.
1258 hashdist= [KNL,NUMA] Large hashes allocated during boot
1259 are distributed across NUMA nodes. Defaults on
1260 for 64-bit NUMA, off otherwise.
1261 Format: 0 | 1 (for off | on)
1263 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1265 hd= [EIDE] (E)IDE hard drive subsystem geometry
1266 Format: <cyl>,<head>,<sect>
1269 Disable Hardware Error Source Table (HEST) support;
1270 corresponding firmware-first mode error processing
1271 logic will be disabled.
1273 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1274 size of <nn>. This works even on boxes that have no
1275 highmem otherwise. This also works to reduce highmem
1276 size on bigger boxes.
1278 highres= [KNL] Enable/disable high resolution timer mode.
1279 Valid parameters: "on", "off"
1283 See Documentation/isdn/README.HiSax.
1287 hpet= [X86-32,HPET] option to control HPET usage
1288 Format: { enable (default) | disable | force |
1290 disable: disable HPET and use PIT instead
1291 force: allow force enabled of undocumented chips (ICH4,
1293 verbose: show contents of HPET registers during setup
1295 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1296 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1298 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1299 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1300 On x86-64 and powerpc, this option can be specified
1301 multiple times interleaved with hugepages= to reserve
1302 huge pages of different sizes. Valid pages sizes on
1303 x86-64 are 2M (when the CPU supports "pse") and 1G
1304 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1306 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1307 terminal devices. Valid values: 0..8
1308 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1309 If specified, z/VM IUCV HVC accepts connections
1310 from listed z/VM user IDs only.
1312 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1313 hardware thread id mappings.
1314 Format: <cpu>:<hwthread>
1317 Do not unregister boot console at start. This is only
1318 useful for debugging when something happens in the window
1319 between unregistering the boot console and initializing
1322 i2c_bus= [HW] Override the default board specific I2C bus speed
1323 or register an additional I2C bus that is not
1324 registered from board initialization code.
1328 i8042.debug [HW] Toggle i8042 debug mode
1329 i8042.unmask_kbd_data
1330 [HW] Enable printing of interrupt data from the KBD port
1331 (disabled by default, and as a pre-condition
1332 requires that i8042.debug=1 be enabled)
1333 i8042.direct [HW] Put keyboard port into non-translated mode
1334 i8042.dumbkbd [HW] Pretend that controller can only read data from
1335 keyboard and cannot control its state
1336 (Don't attempt to blink the leds)
1337 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1338 i8042.nokbd [HW] Don't check/create keyboard port
1339 i8042.noloop [HW] Disable the AUX Loopback command while probing
1341 i8042.nomux [HW] Don't check presence of an active multiplexing
1343 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1345 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1346 i8042.reset [HW] Reset the controller during init, cleanup and
1347 suspend-to-ram transitions, only during s2r
1348 transitions, or never reset
1349 Format: { 1 | Y | y | 0 | N | n }
1350 1, Y, y: always reset controller
1351 0, N, n: don't ever reset controller
1352 Default: only on s2r transitions on x86; most other
1353 architectures force reset to be always executed
1354 i8042.unlock [HW] Unlock (ignore) the keylock
1355 i8042.kbdreset [HW] Reset device connected to KBD port
1359 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1360 indicates that the driver is running on unsupported
1362 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1363 does not match list of supported models.
1365 [HW] Report power status in /proc/i8k
1366 (disabled by default)
1367 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1370 i915.invert_brightness=
1371 [DRM] Invert the sense of the variable that is used to
1372 set the brightness of the panel backlight. Normally a
1373 brightness value of 0 indicates backlight switched off,
1374 and the maximum of the brightness value sets the backlight
1375 to maximum brightness. If this parameter is set to 0
1376 (default) and the machine requires it, or this parameter
1377 is set to 1, a brightness value of 0 sets the backlight
1378 to maximum brightness, and the maximum of the brightness
1379 value switches the backlight off.
1380 -1 -- never invert brightness
1381 0 -- machine default
1382 1 -- force brightness inversion
1385 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1387 ide-core.nodma= [HW] (E)IDE subsystem
1388 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1389 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1390 .cdrom .chs .ignore_cable are additional options
1391 See Documentation/ide/ide.txt.
1393 ide-generic.probe-mask= [HW] (E)IDE subsystem
1395 Probe mask for legacy ISA IDE ports. Depending on
1396 platform up to 6 ports are supported, enabled by
1397 setting corresponding bits in the mask to 1. The
1398 default value is 0x0, which has a special meaning.
1399 On systems that have PCI, it triggers scanning the
1400 PCI bus for the first and the second port, which
1401 are then probed. On systems without PCI the value
1402 of 0x0 enables probing the two first ports as if it
1405 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1406 Claim all unknown PCI IDE storage controllers.
1409 Format: idle=poll, idle=halt, idle=nomwait
1410 Poll forces a polling idle loop that can slightly
1411 improve the performance of waking up a idle CPU, but
1412 will use a lot of power and make the system run hot.
1414 idle=halt: Halt is forced to be used for CPU idle.
1415 In such case C2/C3 won't be used again.
1416 idle=nomwait: Disable mwait for CPU C-states
1418 ieee754= [MIPS] Select IEEE Std 754 conformance mode
1419 Format: { strict | legacy | 2008 | relaxed }
1422 Choose which programs will be accepted for execution
1423 based on the IEEE 754 NaN encoding(s) supported by
1424 the FPU and the NaN encoding requested with the value
1425 of an ELF file header flag individually set by each
1426 binary. Hardware implementations are permitted to
1427 support either or both of the legacy and the 2008 NaN
1430 Available settings are as follows:
1431 strict accept binaries that request a NaN encoding
1432 supported by the FPU
1433 legacy only accept legacy-NaN binaries, if supported
1435 2008 only accept 2008-NaN binaries, if supported
1437 relaxed accept any binaries regardless of whether
1438 supported by the FPU
1440 The FPU emulator is always able to support both NaN
1441 encodings, so if no FPU hardware is present or it has
1442 been disabled with 'nofpu', then the settings of
1443 'legacy' and '2008' strap the emulator accordingly,
1444 'relaxed' straps the emulator for both legacy-NaN and
1445 2008-NaN, whereas 'strict' enables legacy-NaN only on
1446 legacy processors and both NaN encodings on MIPS32 or
1449 The setting for ABS.fmt/NEG.fmt instruction execution
1450 mode generally follows that for the NaN encoding,
1451 except where unsupported by hardware.
1453 ignore_loglevel [KNL]
1454 Ignore loglevel setting - this will print /all/
1455 kernel messages to the console. Useful for debugging.
1456 We also add it as printk module parameter, so users
1457 could change it dynamically, usually by
1458 /sys/module/printk/parameters/ignore_loglevel.
1461 Ignore RLIMIT_DATA setting for data mappings,
1462 print warning at first misuse. Can be changed via
1463 /sys/module/kernel/parameters/ignore_rlimit_data.
1465 ihash_entries= [KNL]
1466 Set number of hash buckets for inode cache.
1468 ima_appraise= [IMA] appraise integrity measurements
1469 Format: { "off" | "enforce" | "fix" | "log" }
1472 ima_appraise_tcb [IMA]
1473 The builtin appraise policy appraises all files
1476 ima_canonical_fmt [IMA]
1477 Use the canonical format for the binary runtime
1478 measurements, instead of host native format.
1481 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1485 The list of supported hash algorithms is defined
1486 in crypto/hash_info.h.
1489 The builtin measurement policy to load during IMA
1490 setup. Specyfing "tcb" as the value, measures all
1491 programs exec'd, files mmap'd for exec, and all files
1492 opened with the read mode bit set by either the
1493 effective uid (euid=0) or uid=0.
1496 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1497 Load a policy which meets the needs of the Trusted
1498 Computing Base. This means IMA will measure all
1499 programs exec'd, files mmap'd for exec, and all files
1500 opened for read by uid=0.
1503 Select one of defined IMA measurements template formats.
1504 Formats: { "ima" | "ima-ng" | "ima-sig" }
1508 [IMA] Define a custom template format.
1509 Format: { "field1|...|fieldN" }
1511 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1512 Format: <min_file_size>
1513 Set the minimal file size for using asynchronous hash.
1514 If left unspecified, ahash usage is disabled.
1516 ahash performance varies for different data sizes on
1517 different crypto accelerators. This option can be used
1518 to achieve the best performance for a particular HW.
1520 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1522 Set hashing buffer size. Default: 4k.
1524 ahash performance varies for different chunk sizes on
1525 different crypto accelerators. This option can be used
1526 to achieve best performance for particular HW.
1530 Run specified binary instead of /sbin/init as init
1533 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1534 for working out where the kernel is dying during
1537 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1538 initcall functions. Useful for debugging built-in
1539 modules and initcalls.
1541 initrd= [BOOT] Specify the location of the initial ramdisk
1543 init_pkru= [x86] Specify the default memory protection keys rights
1544 register contents for all processes. 0x55555554 by
1545 default (disallow access to all but pkey 0). Can
1546 override in debugfs after boot.
1548 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1551 int_pln_enable [x86] Enable power limit notification interrupt
1553 integrity_audit=[IMA]
1554 Format: { "0" | "1" }
1555 0 -- basic integrity auditing messages. (Default)
1556 1 -- additional integrity auditing messages.
1558 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1560 Enable intel iommu driver.
1562 Disable intel iommu driver.
1563 igfx_off [Default Off]
1564 By default, gfx is mapped as normal device. If a gfx
1565 device has a dedicated DMAR unit, the DMAR unit is
1566 bypassed by not enabling DMAR with this option. In
1567 this case, gfx device will use physical address for
1570 With this option iommu will not optimize to look
1571 for io virtual address below 32-bit forcing dual
1572 address cycle on pci bus for cards supporting greater
1573 than 32-bit addressing. The default is to look
1574 for translation below 32-bit and if not available
1575 then look in the higher range.
1576 strict [Default Off]
1577 With this option on every unmap_single operation will
1578 result in a hardware IOTLB flush operation as opposed
1579 to batching them for performance.
1580 sp_off [Default Off]
1581 By default, super page will be supported if Intel IOMMU
1582 has the capability. With this option, super page will
1584 ecs_off [Default Off]
1585 By default, extended context tables will be supported if
1586 the hardware advertises that it has support both for the
1587 extended tables themselves, and also PASID support. With
1588 this option set, extended tables will not be used even
1589 on hardware which claims to support them.
1590 tboot_noforce [Default Off]
1591 Do not force the Intel IOMMU enabled under tboot.
1592 By default, tboot will force Intel IOMMU on, which
1593 could harm performance of some high-throughput
1594 devices like 40GBit network cards, even if identity
1596 Note that using this option lowers the security
1597 provided by tboot because it makes the system
1598 vulnerable to DMA attacks.
1600 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1601 0 disables intel_idle and fall back on acpi_idle.
1602 1 to 9 specify maximum depth of C-state.
1606 Do not enable intel_pstate as the default
1607 scaling driver for the supported processors
1609 Use intel_pstate as a scaling driver, but configure it
1610 to work with generic cpufreq governors (instead of
1611 enabling its internal governor). This mode cannot be
1612 used along with the hardware-managed P-states (HWP)
1615 Enable intel_pstate on systems that prohibit it by default
1616 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1617 instead of acpi-cpufreq may disable platform features, such
1618 as thermal controls and power capping, that rely on ACPI
1619 P-States information being indicated to OSPM and therefore
1620 should be used with caution. This option does not work with
1621 processors that aren't supported by the intel_pstate driver
1622 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1624 Do not enable hardware P state control (HWP)
1627 Only load intel_pstate on systems which support
1628 hardware P state control (HWP) if available.
1630 Enforce ACPI _PPC performance limits. If the Fixed ACPI
1631 Description Table, specifies preferred power management
1632 profile as "Enterprise Server" or "Performance Server",
1633 then this feature is turned on by default.
1635 Allow per-logical-CPU P-State performance control limits using
1636 cpufreq sysfs interface
1638 intremap= [X86-64, Intel-IOMMU]
1639 on enable Interrupt Remapping (default)
1640 off disable Interrupt Remapping
1641 nosid disable Source ID checking
1643 BIOS x2APIC opt-out request will be ignored
1644 nopost disable Interrupt Posting
1646 iomem= Disable strict checking of access to MMIO memory
1647 strict regions from userspace.
1662 nobypass [PPC/POWERNV]
1663 Disable IOMMU bypass, using IOMMU for PCI devices.
1666 [ARM64] Configure DMA to bypass the IOMMU by default.
1667 Format: { "0" | "1" }
1668 0 - Use IOMMU translation for DMA.
1669 1 - Bypass the IOMMU for DMA.
1670 unset - Use IOMMU translation for DMA.
1672 io7= [HW] IO7 for Marvel based alpha systems
1673 See comment before marvel_specify_io7 in
1674 arch/alpha/kernel/core_marvel.c.
1676 io_delay= [X86] I/O delay method
1678 Standard port 0x80 based delay
1680 Alternate port 0xed based delay (needed on some systems)
1682 Simple two microseconds delay
1687 See Documentation/filesystems/nfs/nfsroot.txt.
1689 irqaffinity= [SMP] Set the default irq affinity mask
1690 The argument is a cpu list, as described above.
1693 When an interrupt is not handled search all handlers
1694 for it. Intended to get systems with badly broken
1698 When an interrupt is not handled search all handlers
1699 for it. Also check all handlers each timer
1700 interrupt. Intended to get systems with badly broken
1704 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1706 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1707 The argument is a cpu list, as described above.
1709 This option can be used to specify one or more CPUs
1710 to isolate from the general SMP balancing and scheduling
1711 algorithms. You can move a process onto or off an
1712 "isolated" CPU via the CPU affinity syscalls or cpuset.
1713 <cpu number> begins at 0 and the maximum value is
1714 "number of CPUs in system - 1".
1716 This option is the preferred way to isolate CPUs. The
1717 alternative -- manually setting the CPU mask of all
1718 tasks in the system -- can cause problems and
1719 suboptimal load balancer performance.
1723 ivrs_ioapic [HW,X86_64]
1724 Provide an override to the IOAPIC-ID<->DEVICE-ID
1725 mapping provided in the IVRS ACPI table. For
1726 example, to map IOAPIC-ID decimal 10 to
1727 PCI device 00:14.0 write the parameter as:
1728 ivrs_ioapic[10]=00:14.0
1730 ivrs_hpet [HW,X86_64]
1731 Provide an override to the HPET-ID<->DEVICE-ID
1732 mapping provided in the IVRS ACPI table. For
1733 example, to map HPET-ID decimal 0 to
1734 PCI device 00:14.0 write the parameter as:
1735 ivrs_hpet[0]=00:14.0
1737 ivrs_acpihid [HW,X86_64]
1738 Provide an override to the ACPI-HID:UID<->DEVICE-ID
1739 mapping provided in the IVRS ACPI table. For
1740 example, to map UART-HID:UID AMD0020:0 to
1741 PCI device 00:14.5 write the parameter as:
1742 ivrs_acpihid[00:14.5]=AMD0020:0
1744 js= [HW,JOY] Analog joystick
1745 See Documentation/input/joystick.txt.
1748 When CONFIG_RANDOMIZE_BASE is set, this disables
1749 kernel and module base offset ASLR (Address Space
1750 Layout Randomization).
1753 [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
1754 report on every invalid memory access. Without this
1755 parameter KASAN will print report only for the first
1760 kernelcore= [KNL,X86,IA-64,PPC]
1761 Format: nn[KMGTPE] | "mirror"
1763 specifies the amount of memory usable by the kernel
1764 for non-movable allocations. The requested amount is
1765 spread evenly throughout all nodes in the system. The
1766 remaining memory in each node is used for Movable
1767 pages. In the event, a node is too small to have both
1768 kernelcore and Movable pages, kernelcore pages will
1769 take priority and other nodes will have a larger number
1770 of Movable pages. The Movable zone is used for the
1771 allocation of pages that may be reclaimed or moved
1772 by the page migration subsystem. This means that
1773 HugeTLB pages may not be allocated from this zone.
1774 Note that allocations like PTEs-from-HighMem still
1775 use the HighMem zone if it exists, and the Normal
1776 zone if it does not.
1778 Instead of specifying the amount of memory (nn[KMGTPE]),
1779 you can specify "mirror" option. In case "mirror"
1780 option is specified, mirrored (reliable) memory is used
1781 for non-movable allocations and remaining memory is used
1782 for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
1783 so you can NOT specify nn[KMGTPE] and "mirror" at the same
1786 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1787 Format: <Controller#>[,poll interval]
1788 The controller # is the number of the ehci usb debug
1789 port as it is probed via PCI. The poll interval is
1790 optional and is the number seconds in between
1791 each poll cycle to the debug port in case you need
1792 the functionality for interrupting the kernel with
1793 gdb or control-c on the dbgp connection. When
1794 not using this parameter you use sysrq-g to break into
1795 the kernel debugger.
1797 kgdboc= [KGDB,HW] kgdb over consoles.
1798 Requires a tty driver that supports console polling,
1799 or a supported polling keyboard driver (non-usb).
1800 Serial only format: <serial_device>[,baud]
1801 keyboard only format: kbd
1802 keyboard and serial format: kbd,<serial_device>[,baud]
1803 Optional Kernel mode setting:
1804 kms, kbd format: kms,kbd
1805 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1807 kgdbwait [KGDB] Stop kernel execution and enter the
1808 kernel debugger at the earliest opportunity.
1810 kmac= [MIPS] korina ethernet MAC address.
1811 Configure the RouterBoard 532 series on-chip
1812 Ethernet adapter MAC address.
1814 kmemleak= [KNL] Boot-time kmemleak enable/disable
1815 Valid arguments: on, off
1817 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1820 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1821 Valid arguments: 0, 1, 2
1822 kmemcheck=0 (disabled)
1823 kmemcheck=1 (enabled)
1824 kmemcheck=2 (one-shot mode)
1825 Default: 2 (one-shot mode)
1827 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1828 Default is 0 (don't ignore, but inject #GP)
1830 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1834 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1835 Default is 1 (enabled)
1837 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1839 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1841 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1842 (virtualized MMU) support on capable Intel chips.
1843 Default is 1 (enabled)
1845 kvm-intel.emulate_invalid_guest_state=
1846 [KVM,Intel] Enable emulation of invalid guest states
1847 Default is 0 (disabled)
1849 kvm-intel.flexpriority=
1850 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1851 Default is 1 (enabled)
1854 [KVM,Intel] Enable VMX nesting (nVMX).
1855 Default is 0 (disabled)
1857 kvm-intel.unrestricted_guest=
1858 [KVM,Intel] Disable unrestricted guest feature
1859 (virtualized real and unpaged mode) on capable
1860 Intel chips. Default is 1 (enabled)
1862 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1863 feature (tagged TLBs) on capable Intel chips.
1864 Default is 1 (enabled)
1870 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1873 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1874 value for LAPIC timer one-shot implementation. Default
1875 back to the programmable timer unit in the LAPIC.
1877 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1880 libata.dma= [LIBATA] DMA control
1881 libata.dma=0 Disable all PATA and SATA DMA
1882 libata.dma=1 PATA and SATA Disk DMA only
1883 libata.dma=2 ATAPI (CDROM) DMA only
1884 libata.dma=4 Compact Flash DMA only
1885 Combinations also work, so libata.dma=3 enables DMA
1886 for disks and CDROMs, but not CFs.
1888 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1889 libata.ignore_hpa=0 keep BIOS limits (default)
1890 libata.ignore_hpa=1 ignore limits, using full disk
1892 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1896 libata.force= [LIBATA] Force configurations. The format is comma
1897 separated list of "[ID:]VAL" where ID is
1898 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1899 matching port, link or device. Basically, it matches
1900 the ATA ID string printed on console by libata. If
1901 the whole ID part is omitted, the last PORT and DEVICE
1902 values are used. If ID hasn't been specified yet, the
1903 configuration applies to all ports, links and devices.
1905 If only DEVICE is omitted, the parameter applies to
1906 the port and all links and devices behind it. DEVICE
1907 number of 0 either selects the first device or the
1908 first fan-out link behind PMP device. It does not
1909 select the host link. DEVICE number of 15 selects the
1910 host link and device attached to it.
1912 The VAL specifies the configuration to force. As long
1913 as there's no ambiguity shortcut notation is allowed.
1914 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1915 The following configurations can be forced.
1917 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1918 Any ID with matching PORT is used.
1920 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1922 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1923 udma[/][16,25,33,44,66,100,133] notation is also
1926 * [no]ncq: Turn on or off NCQ.
1928 * [no]ncqtrim: Turn off queued DSM TRIM.
1930 * nohrst, nosrst, norst: suppress hard, soft
1933 * rstonce: only attempt one reset during
1934 hot-unplug link recovery
1936 * dump_id: dump IDENTIFY data.
1938 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1940 * disable: Disable this device.
1942 If there are multiple matching configurations changing
1943 the same attribute, the last one is used.
1945 memblock=debug [KNL] Enable memblock debug messages.
1947 load_ramdisk= [RAM] List of ramdisks to load from floppy
1948 See Documentation/blockdev/ramdisk.txt.
1950 lockd.nlm_grace_period=P [NFS] Assign grace period.
1953 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1956 lockd.nlm_timeout=T [NFS] Assign timeout value.
1959 lockd.nlm_udpport=M [NFS] Assign UDP port.
1962 locktorture.nreaders_stress= [KNL]
1963 Set the number of locking read-acquisition kthreads.
1964 Defaults to being automatically set based on the
1965 number of online CPUs.
1967 locktorture.nwriters_stress= [KNL]
1968 Set the number of locking write-acquisition kthreads.
1970 locktorture.onoff_holdoff= [KNL]
1971 Set time (s) after boot for CPU-hotplug testing.
1973 locktorture.onoff_interval= [KNL]
1974 Set time (s) between CPU-hotplug operations, or
1975 zero to disable CPU-hotplug testing.
1977 locktorture.shuffle_interval= [KNL]
1978 Set task-shuffle interval (jiffies). Shuffling
1979 tasks allows some CPUs to go into dyntick-idle
1980 mode during the locktorture test.
1982 locktorture.shutdown_secs= [KNL]
1983 Set time (s) after boot system shutdown. This
1984 is useful for hands-off automated testing.
1986 locktorture.stat_interval= [KNL]
1987 Time (s) between statistics printk()s.
1989 locktorture.stutter= [KNL]
1990 Time (s) to stutter testing, for example,
1991 specifying five seconds causes the test to run for
1992 five seconds, wait for five seconds, and so on.
1993 This tests the locking primitive's ability to
1994 transition abruptly to and from idle.
1996 locktorture.torture_runnable= [BOOT]
1997 Start locktorture running at boot time.
1999 locktorture.torture_type= [KNL]
2000 Specify the locking implementation to test.
2002 locktorture.verbose= [KNL]
2003 Enable additional printk() statements.
2005 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
2008 loglevel= All Kernel Messages with a loglevel smaller than the
2009 console loglevel will be printed to the console. It can
2010 also be changed with klogd or other programs. The
2011 loglevels are defined as follows:
2013 0 (KERN_EMERG) system is unusable
2014 1 (KERN_ALERT) action must be taken immediately
2015 2 (KERN_CRIT) critical conditions
2016 3 (KERN_ERR) error conditions
2017 4 (KERN_WARNING) warning conditions
2018 5 (KERN_NOTICE) normal but significant condition
2019 6 (KERN_INFO) informational
2020 7 (KERN_DEBUG) debug-level messages
2022 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
2023 in bytes. n must be a power of two and greater
2024 than the minimal size. The minimal size is defined
2025 by LOG_BUF_SHIFT kernel config parameter. There is
2026 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
2027 that allows to increase the default size depending on
2028 the number of CPUs. See init/Kconfig for more details.
2030 logo.nologo [FB] Disables display of the built-in Linux logo.
2031 This may be used to provide more screen space for
2032 kernel log messages and is useful when debugging
2033 kernel boot problems.
2035 lp=0 [LP] Specify parallel ports to use, e.g,
2036 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
2037 lp=reset first parallel port). 'lp=0' disables the
2038 lp=auto printer driver. 'lp=reset' (which can be
2039 specified in addition to the ports) causes
2040 attached printers to be reset. Using
2041 lp=port1,port2,... specifies the parallel ports
2042 to associate lp devices with, starting with
2043 lp0. A port specification may be 'none' to skip
2044 that lp device, or a parport name such as
2045 'parport0'. Specifying 'lp=auto' instead of a
2046 port specification list means that device IDs
2047 from each port should be examined, to see if
2048 an IEEE 1284-compliant printer is attached; if
2049 so, the driver will manage that printer.
2050 See also header of drivers/char/lp.c.
2053 Sets loops_per_jiffy to given constant, thus avoiding
2054 time-consuming boot-time autodetection (up to 250 ms per
2055 CPU). 0 enables autodetection (default). To determine
2056 the correct value for your kernel, boot with normal
2057 autodetection and see what value is printed. Note that
2058 on SMP systems the preset will be applied to all CPUs,
2059 which is likely to cause problems if your CPUs need
2060 significantly divergent settings. An incorrect value
2061 will cause delays in the kernel to be wrong, leading to
2062 unpredictable I/O errors and other breakage. Although
2063 unlikely, in the extreme case this might damage your
2067 Format: <io>,<irq>,<dma>
2069 machvec= [IA-64] Force the use of a particular machine-vector
2070 (machvec) in a generic kernel.
2071 Example: machvec=hpzx1_swiotlb
2073 machtype= [Loongson] Share the same kernel image file between different
2075 Example: machtype=lemote-yeeloong-2f-7inch
2077 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2078 than or equal to this physical address is ignored.
2080 maxcpus= [SMP] Maximum number of processors that an SMP kernel
2081 will bring up during bootup. maxcpus=n : n >= 0 limits
2082 the kernel to bring up 'n' processors. Surely after
2083 bootup you can bring up the other plugged cpu by executing
2084 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
2085 only takes effect during system bootup.
2086 While n=0 is a special case, it is equivalent to "nosmp",
2087 which also disables the IO APIC.
2089 max_loop= [LOOP] The number of loop block devices that get
2090 (loop.max_loop) unconditionally pre-created at init time. The default
2091 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2092 of statically allocating a predefined number, loop
2093 devices can be requested on-demand with the
2094 /dev/loop-control interface.
2096 mce [X86-32] Machine Check Exception
2098 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2100 md= [HW] RAID subsystems devices and level
2101 See Documentation/admin-guide/md.rst.
2104 Format: <first>,<last>
2105 Specifies range of consoles to be captured by the MDA.
2107 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2108 Amount of memory to be used when the kernel is not able
2109 to see the whole system memory or for test.
2110 [X86] Work as limiting max address. Use together
2111 with memmap= to avoid physical address space collisions.
2112 Without memmap= PCI devices could be placed at addresses
2113 belonging to unused RAM.
2115 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2119 [KNL,SH] Allow user to override the default size for
2120 per-device physically contiguous DMA buffers.
2122 memhp_default_state=online/offline
2123 [KNL] Set the initial state for the memory hotplug
2124 onlining policy. If not specified, the default value is
2125 set according to the
2126 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
2128 See Documentation/memory-hotplug.txt.
2130 memmap=exactmap [KNL,X86] Enable setting of an exact
2131 E820 memory map, as specified by the user.
2132 Such memmap=exactmap lines can be constructed based on
2133 BIOS output or other requirements. See the memmap=nn@ss
2136 memmap=nn[KMG]@ss[KMG]
2137 [KNL] Force usage of a specific region of memory.
2138 Region of memory to be used is from ss to ss+nn.
2140 memmap=nn[KMG]#ss[KMG]
2141 [KNL,ACPI] Mark specific memory as ACPI data.
2142 Region of memory to be marked is from ss to ss+nn.
2144 memmap=nn[KMG]$ss[KMG]
2145 [KNL,ACPI] Mark specific memory as reserved.
2146 Region of memory to be reserved is from ss to ss+nn.
2147 Example: Exclude memory from 0x18690000-0x1869ffff
2148 memmap=64K$0x18690000
2150 memmap=0x10000$0x18690000
2152 memmap=nn[KMG]!ss[KMG]
2153 [KNL,X86] Mark specific memory as protected.
2154 Region of memory to be used, from ss to ss+nn.
2155 The memory region may be marked as e820 type 12 (0xc)
2156 and is NVDIMM or ADR memory.
2158 memory_corruption_check=0/1 [X86]
2159 Some BIOSes seem to corrupt the first 64k of
2160 memory when doing things like suspend/resume.
2161 Setting this option will scan the memory
2162 looking for corruption. Enabling this will
2163 both detect corruption and prevent the kernel
2164 from using the memory being corrupted.
2165 However, its intended as a diagnostic tool; if
2166 repeatable BIOS-originated corruption always
2167 affects the same memory, you can use memmap=
2168 to prevent the kernel from using that memory.
2170 memory_corruption_check_size=size [X86]
2171 By default it checks for corruption in the low
2172 64k, making this memory unavailable for normal
2173 use. Use this parameter to scan for
2174 corruption in more or less memory.
2176 memory_corruption_check_period=seconds [X86]
2177 By default it checks for corruption every 60
2178 seconds. Use this parameter to check at some
2179 other rate. 0 disables periodic checking.
2181 memtest= [KNL,X86,ARM] Enable memtest
2183 default : 0 <disable>
2184 Specifies the number of memtest passes to be
2185 performed. Each pass selects another test
2186 pattern from a given set of patterns. Memtest
2187 fills the memory with this pattern, validates
2188 memory contents and reserves bad memory
2189 regions that are detected.
2191 mem_sleep_default= [SUSPEND] Default system suspend mode:
2192 s2idle - Suspend-To-Idle
2193 shallow - Power-On Suspend or equivalent (if supported)
2194 deep - Suspend-To-RAM or equivalent (if supported)
2195 See Documentation/power/states.txt.
2197 meye.*= [HW] Set MotionEye Camera parameters
2198 See Documentation/video4linux/meye.txt.
2200 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2201 Multi-Function General Purpose Timers on AMD Geode
2204 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2205 the BIOS has incorrectly applied a workaround. TinyBIOS
2206 version 0.98 is known to be affected, 0.99 fixes the
2207 problem by letting the user disable the workaround.
2211 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2212 physical address is ignored.
2214 mini2440= [ARM,HW,KNL]
2215 Format:[0..2][b][c][t]
2217 MINI2440 configuration specification:
2218 0 - The attached screen is the 3.5" TFT
2219 1 - The attached screen is the 7" TFT
2220 2 - The VGA Shield is attached (1024x768)
2221 Leaving out the screen size parameter will not load
2222 the TFT driver, and the framebuffer will be left
2224 b - Enable backlight. The TFT backlight pin will be
2225 linked to the kernel VESA blanking code and a GPIO
2226 LED. This parameter is not necessary when using the
2228 c - Enable the s3c camera interface.
2229 t - Reserved for enabling touchscreen support. The
2230 touchscreen support is not enabled in the mainstream
2231 kernel as of 2.6.30, a preliminary port can be found
2232 in the "bleeding edge" mini2440 support kernel at
2233 http://repo.or.cz/w/linux-2.6/mini2440.git
2236 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2237 parameter allows control of the logging verbosity for
2238 the additional memory initialisation checks. A value
2239 of 0 disables mminit logging and a level of 4 will
2240 log everything. Information is printed at KERN_DEBUG
2241 so loglevel=8 may also need to be specified.
2244 [KNL] When CONFIG_MODULE_SIG is set, this means that
2245 modules without (valid) signatures will fail to load.
2246 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2247 is always true, so this option does nothing.
2249 module_blacklist= [KNL] Do not load a comma-separated list of
2250 modules. Useful for debugging problem modules.
2253 [MOUSE] Maximum time between finger touching and
2254 leaving touchpad surface for touch to be considered
2255 a tap and be reported as a left button click (for
2256 touchpads working in absolute mode only).
2258 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2259 reporting absolute coordinates, such as tablets
2260 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2261 reporting absolute coordinates, such as tablets
2263 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2264 is similar to kernelcore except it specifies the
2265 amount of memory used for migratable allocations.
2266 If both kernelcore and movablecore is specified,
2267 then kernelcore will be at *least* the specified
2268 value but may be more. If movablecore on its own
2269 is specified, the administrator must be careful
2270 that the amount of memory usable for all allocations
2273 movable_node [KNL] Boot-time switch to enable the effects
2274 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2276 MTD_Partition= [MTD]
2277 Format: <name>,<region-number>,<size>,<offset>
2279 MTD_Region= [MTD] Format:
2280 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2283 See drivers/mtd/cmdlinepart.c.
2285 multitce=off [PPC] This parameter disables the use of the pSeries
2286 firmware feature for updating multiple TCE entries
2289 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2291 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2293 boundary - index of last SLC block on Flex-OneNAND.
2294 The remaining blocks are configured as MLC blocks.
2295 lock - Configure if Flex-OneNAND boundary should be locked.
2296 Once locked, the boundary cannot be changed.
2297 1 indicates lock status, 0 indicates unlock status.
2300 ARM/S3C2412 JIVE boot control
2302 See arch/arm/mach-s3c2412/mach-jive.c
2304 mtouchusb.raw_coordinates=
2305 [HW] Make the MicroTouch USB driver use raw coordinates
2306 ('y', default) or cooked coordinates ('n')
2308 mtrr_chunk_size=nn[KMG] [X86]
2309 used for mtrr cleanup. It is largest continuous chunk
2310 that could hold holes aka. UC entries.
2312 mtrr_gran_size=nn[KMG] [X86]
2313 Used for mtrr cleanup. It is granularity of mtrr block.
2315 Large value could prevent small alignment from
2318 mtrr_spare_reg_nr=n [X86]
2320 Range: 0,7 : spare reg number
2322 Used for mtrr cleanup. It is spare mtrr entries number.
2323 Set to 2 or more if your graphical card needs more.
2325 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2327 netdev= [NET] Network devices parameters
2328 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2329 Note that mem_start is often overloaded to mean
2330 something different and driver-specific.
2331 This usage is only documented in each driver source
2335 [NETFILTER] Enable connection tracking flow accounting
2336 0 to disable accounting
2337 1 to enable accounting
2340 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2341 See Documentation/filesystems/nfs/nfsroot.txt.
2343 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2344 See Documentation/filesystems/nfs/nfsroot.txt.
2346 nfsrootdebug [NFS] enable nfsroot debugging messages.
2347 See Documentation/filesystems/nfs/nfsroot.txt.
2349 nfs.callback_nr_threads=
2350 [NFSv4] set the total number of threads that the
2351 NFS client will assign to service NFSv4 callback
2354 nfs.callback_tcpport=
2355 [NFS] set the TCP port on which the NFSv4 callback
2356 channel should listen.
2359 [NFS] sets the pathname to the program which is used
2360 to update the NFS client cache entries.
2362 nfs.cache_getent_timeout=
2363 [NFS] sets the timeout after which an attempt to
2364 update a cache entry is deemed to have failed.
2366 nfs.idmap_cache_timeout=
2367 [NFS] set the maximum lifetime for idmapper cache
2371 [NFS] enable 64-bit inode numbers.
2372 If zero, the NFS client will fake up a 32-bit inode
2373 number for the readdir() and stat() syscalls instead
2374 of returning the full 64-bit number.
2375 The default is to return 64-bit inode numbers.
2377 nfs.max_session_cb_slots=
2378 [NFSv4.1] Sets the maximum number of session
2379 slots the client will assign to the callback
2380 channel. This determines the maximum number of
2381 callbacks the client will process in parallel for
2382 a particular server.
2384 nfs.max_session_slots=
2385 [NFSv4.1] Sets the maximum number of session slots
2386 the client will attempt to negotiate with the server.
2387 This limits the number of simultaneous RPC requests
2388 that the client can send to the NFSv4.1 server.
2389 Note that there is little point in setting this
2390 value higher than the max_tcp_slot_table_limit.
2392 nfs.nfs4_disable_idmapping=
2393 [NFSv4] When set to the default of '1', this option
2394 ensures that both the RPC level authentication
2395 scheme and the NFS level operations agree to use
2396 numeric uids/gids if the mount is using the
2397 'sec=sys' security flavour. In effect it is
2398 disabling idmapping, which can make migration from
2399 legacy NFSv2/v3 systems to NFSv4 easier.
2400 Servers that do not support this mode of operation
2401 will be autodetected by the client, and it will fall
2402 back to using the idmapper.
2403 To turn off this behaviour, set the value to '0'.
2405 [NFS4] Specify an additional fixed unique ident-
2406 ification string that NFSv4 clients can insert into
2407 their nfs_client_id4 string. This is typically a
2408 UUID that is generated at system install time.
2410 nfs.send_implementation_id =
2411 [NFSv4.1] Send client implementation identification
2412 information in exchange_id requests.
2413 If zero, no implementation identification information
2415 The default is to send the implementation identification
2418 nfs.recover_lost_locks =
2419 [NFSv4] Attempt to recover locks that were lost due
2420 to a lease timeout on the server. Please note that
2421 doing this risks data corruption, since there are
2422 no guarantees that the file will remain unchanged
2423 after the locks are lost.
2424 If you want to enable the kernel legacy behaviour of
2425 attempting to recover these locks, then set this
2427 The default parameter value of '0' causes the kernel
2428 not to attempt recovery of lost locks.
2430 nfs4.layoutstats_timer =
2431 [NFSv4.2] Change the rate at which the kernel sends
2432 layoutstats to the pNFS metadata server.
2434 Setting this to value to 0 causes the kernel to use
2435 whatever value is the default set by the layout
2436 driver. A non-zero value sets the minimum interval
2437 in seconds between layoutstats transmissions.
2439 nfsd.nfs4_disable_idmapping=
2440 [NFSv4] When set to the default of '1', the NFSv4
2441 server will return only numeric uids and gids to
2442 clients using auth_sys, and will accept numeric uids
2443 and gids from such clients. This is intended to ease
2444 migration from NFSv2/v3.
2446 nmi_debug= [KNL,SH] Specify one or more actions to take
2447 when a NMI is triggered.
2448 Format: [state][,regs][,debounce][,die]
2450 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2451 Format: [panic,][nopanic,][num]
2453 0 - turn hardlockup detector in nmi_watchdog off
2454 1 - turn hardlockup detector in nmi_watchdog on
2455 When panic is specified, panic when an NMI watchdog
2456 timeout occurs (or 'nopanic' to override the opposite
2457 default). To disable both hard and soft lockup detectors,
2458 please see 'nowatchdog'.
2459 This is useful when you use a panic=... timeout and
2460 need the box quickly up again.
2462 netpoll.carrier_timeout=
2463 [NET] Specifies amount of time (in seconds) that
2464 netpoll should wait for a carrier. By default netpoll
2467 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2468 emulation library even if a 387 maths coprocessor
2472 [HW] Never suspend the console
2473 Disable suspending of consoles during suspend and
2474 hibernate operations. Once disabled, debugging
2475 messages can reach various consoles while the rest
2476 of the system is being put to sleep (ie, while
2477 debugging driver suspend/resume hooks). This may
2478 not work reliably with all consoles, but is known
2479 to work with serial and VGA consoles.
2480 To facilitate more flexible debugging, we also add
2481 console_suspend, a printk module parameter to control
2482 it. Users could use console_suspend (usually
2483 /sys/module/printk/parameters/console_suspend) to
2484 turn on/off it dynamically.
2486 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2487 caches in the slab allocator. Saves per-node memory,
2488 but will impact performance.
2492 noapic [SMP,APIC] Tells the kernel to not make use of any
2493 IOAPICs that may be present in the system.
2495 noautogroup Disable scheduler automatic task group creation.
2497 nobats [PPC] Do not use BATs for mapping kernel lowmem
2498 on "Classic" PPC cores.
2502 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2504 nodelayacct [KNL] Disable per-task delay accounting
2506 nodsp [SH] Disable hardware DSP at boot time.
2508 noefi Disable EFI runtime services support.
2513 On X86-32 available only on PAE configured kernels.
2514 noexec=on: enable non-executable mappings (default)
2515 noexec=off: disable non-executable mappings
2518 Disable SMAP (Supervisor Mode Access Prevention)
2519 even if it is supported by processor.
2522 Disable SMEP (Supervisor Mode Execution Prevention)
2523 even if it is supported by processor.
2526 This affects only 32-bit executables.
2527 noexec32=on: enable non-executable mappings (default)
2528 read doesn't imply executable mappings
2529 noexec32=off: disable non-executable mappings
2530 read implies executable mappings
2532 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2534 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2535 register save and restore. The kernel will only save
2536 legacy floating-point registers on task switch.
2538 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2540 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
2541 Equivalent to smt=1.
2543 noxsave [BUGS=X86] Disables x86 extended register state save
2544 and restore using xsave. The kernel will fallback to
2545 enabling legacy floating-point and sse state.
2547 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2548 register states. The kernel will fall back to use
2549 xsave to save the states. By using this parameter,
2550 performance of saving the states is degraded because
2551 xsave doesn't support modified optimization while
2552 xsaveopt supports it on xsaveopt enabled systems.
2554 noxsaves [X86] Disables xsaves and xrstors used in saving and
2555 restoring x86 extended register state in compacted
2556 form of xsave area. The kernel will fall back to use
2557 xsaveopt and xrstor to save and restore the states
2558 in standard form of xsave area. By using this
2559 parameter, xsave area per process might occupy more
2560 memory on xsaves enabled systems.
2562 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2563 wfi(ARM) instruction doesn't work correctly and not to
2564 use it. This is also useful when using JTAG debugger.
2566 no_file_caps Tells the kernel not to honor file capabilities. The
2567 only way then for a file to be executed with privilege
2568 is to be setuid root or executed by root.
2570 nohalt [IA-64] Tells the kernel not to use the power saving
2571 function PAL_HALT_LIGHT when idle. This increases
2572 power-consumption. On the positive side, it reduces
2573 interrupt wake-up latency, which may improve performance
2574 in certain environments such as networked servers or
2577 nohibernate [HIBERNATION] Disable hibernation and resume.
2579 nohz= [KNL] Boottime enable/disable dynamic ticks
2580 Valid arguments: on, off
2583 nohz_full= [KNL,BOOT]
2584 The argument is a cpu list, as described above.
2585 In kernels built with CONFIG_NO_HZ_FULL=y, set
2586 the specified list of CPUs whose tick will be stopped
2587 whenever possible. The boot CPU will be forced outside
2588 the range to maintain the timekeeping.
2589 The CPUs in this range must also be included in the
2592 noiotrap [SH] Disables trapped I/O port accesses.
2594 noirqdebug [X86-32] Disables the code which attempts to detect and
2595 disable unhandled interrupt sources.
2597 no_timer_check [X86,APIC] Disables the code which tests for
2598 broken timer IRQ sources.
2600 noisapnp [ISAPNP] Disables ISA PnP code.
2602 noinitrd [RAM] Tells the kernel not to load any configured
2605 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2607 [Deprecated - use intremap=off]
2611 noinvpcid [X86] Disable the INVPCID cpu feature.
2613 nojitter [IA-64] Disables jitter checking for ITC timers.
2615 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2617 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2621 [X86,PV_OPS] Disable paravirtualized VMware scheduler
2622 clock and use the default one.
2624 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2625 steal time is computed, but won't influence scheduler
2628 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2630 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2632 noltlbs [PPC] Do not use large page/tlb entries for kernel
2633 lowmem mapping on PPC40x and PPC8xx
2635 nomca [IA-64] Disable machine check abort handling
2637 nomce [X86-32] Disable Machine Check Exception
2639 nomfgpt [X86-32] Disable Multi-Function General Purpose
2640 Timer usage (for AMD Geode machines).
2642 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2643 shutdown the other cpus. Instead use the REBOOT_VECTOR
2646 nomodule Disable module load
2648 nopat [X86] Disable PAT (page attribute table extension of
2649 pagetables) support.
2651 norandmaps Don't use address space randomization. Equivalent to
2652 echo 0 > /proc/sys/kernel/randomize_va_space
2654 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2656 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2657 with UP alternatives
2659 nordrand [X86] Disable kernel use of the RDRAND and
2660 RDSEED instructions even if they are supported
2661 by the processor. RDRAND and RDSEED are still
2662 available to user space applications.
2664 noresume [SWSUSP] Disables resume and restores original swap
2667 no-scroll [VGA] Disables scrollback.
2668 This is required for the Braillex ib80-piezo Braille
2669 reader made by F.H. Papenmeier (Germany).
2673 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2675 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2676 and disable the IO APIC. legacy for "maxcpus=0".
2678 nosoftlockup [KNL] Disable the soft-lockup detector.
2680 nosync [HW,M68K] Disables sync negotiation for all devices.
2682 notsc [BUGS=X86-32] Disable Time Stamp Counter
2684 nowatchdog [KNL] Disable both lockup detectors, i.e.
2685 soft-lockup and NMI watchdog (hard-lockup).
2689 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2691 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2692 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2693 Some features depend on CPU0. Known dependencies are:
2694 1. Resume from suspend/hibernate depends on CPU0.
2695 Suspend/hibernate will fail if CPU0 is offline and you
2696 need to online CPU0 before suspend/hibernate.
2697 2. PIC interrupts also depend on CPU0. CPU0 can't be
2698 removed if a PIC interrupt is detected.
2699 It's said poweroff/reboot may depend on CPU0 on some
2700 machines although I haven't seen such issues so far
2701 after CPU0 is offline on a few tested machines.
2702 If the dependencies are under your control, you can
2703 turn on cpu0_hotplug.
2705 nptcg= [IA-64] Override max number of concurrent global TLB
2706 purges which is reported from either PAL_VM_SUMMARY or
2709 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2710 could support. nr_cpus=n : n >= 1 limits the kernel to
2711 support 'n' processors. It could be larger than the
2712 number of already plugged CPU during bootup, later in
2713 runtime you can physically add extra cpu until it reaches
2714 n. So during boot up some boot time memory for per-cpu
2715 variables need be pre-allocated for later physical cpu
2718 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2720 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2721 Allowed values are enable and disable
2723 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2724 one of ['zone', 'node', 'default'] can be specified
2725 This can be set from sysctl after boot.
2726 See Documentation/sysctl/vm.txt for details.
2728 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2729 See Documentation/debugging-via-ohci1394.txt for more
2732 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2733 Rather than timing out after 20 ms if an EC
2734 command is not properly ACKed, override the length
2735 of the timeout. We have interrupts disabled while
2736 waiting for the ACK, so if this is set too high
2737 interrupts *may* be lost!
2739 omap_mux= [OMAP] Override bootloader pin multiplexing.
2740 Format: <mux_mode0.mode_name=value>...
2741 For example, to override I2C bus2:
2742 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2744 oprofile.timer= [HW]
2745 Use timer interrupt instead of performance counters
2747 oprofile.cpu_type= Force an oprofile cpu type
2748 This might be useful if you have an older oprofile
2749 userland or if you want common events.
2750 Format: { arch_perfmon }
2751 arch_perfmon: [X86] Force use of architectural
2752 perfmon on Intel CPUs instead of the
2753 CPU specific event set.
2754 timer: [X86] Force use of architectural NMI
2755 timer mode (see also oprofile.timer
2756 for generic hr timer mode)
2758 oops=panic Always panic on oopses. Default is to just kill the
2759 process, but there is a small probability of
2760 deadlocking the machine.
2761 This will also cause panics on machine check exceptions.
2762 Useful together with panic=30 to trigger a reboot.
2765 See Documentation/sound/oss/oss-parameters.txt
2767 page_owner= [KNL] Boot-time page_owner enabling option.
2768 Storage of the information about who allocated
2769 each page is disabled in default. With this switch,
2771 on: enable the feature
2773 page_poison= [KNL] Boot-time parameter changing the state of
2774 poisoning on the buddy allocator.
2775 off: turn off poisoning
2776 on: turn on poisoning
2778 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2779 timeout > 0: seconds before rebooting
2780 timeout = 0: wait forever
2781 timeout < 0: reboot immediately
2784 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2787 crash_kexec_post_notifiers
2788 Run kdump after running panic-notifiers and dumping
2789 kmsg. This only for the users who doubt kdump always
2790 succeeds in any situation.
2791 Note that this also increases risks of kdump failure,
2792 because some panic notifiers can make the crashed
2793 kernel more unstable.
2795 parkbd.port= [HW] Parallel port number the keyboard adapter is
2796 connected to, default is 0.
2798 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2799 0 for XT, 1 for AT (default is AT).
2802 parport= [HW,PPT] Specify parallel ports. 0 disables.
2803 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2804 Use 'auto' to force the driver to use any
2805 IRQ/DMA settings detected (the default is to
2806 ignore detected IRQ/DMA settings because of
2807 possible conflicts). You can specify the base
2808 address, IRQ, and DMA settings; IRQ and DMA
2809 should be numbers, or 'auto' (for using detected
2810 settings on that particular port), or 'nofifo'
2811 (to avoid using a FIFO even if it is detected).
2812 Parallel ports are assigned in the order they
2813 are specified on the command line, starting
2816 parport_init_mode= [HW,PPT]
2817 Configure VIA parallel port to operate in
2818 a specific mode. This is necessary on Pegasos
2819 computer where firmware has no options for setting
2820 up parallel port mode and sets it to spp.
2821 Currently this function knows 686a and 8231 chips.
2822 Format: [spp|ps2|epp|ecp|ecpepp]
2825 Halt all CPUs after the first oops has been printed for
2826 the specified number of seconds. This is to be used if
2827 your oopses keep scrolling off the screen.
2832 See header of drivers/block/paride/pcd.c.
2833 See also Documentation/blockdev/paride.txt.
2835 pci=option[,option...] [PCI] various PCI subsystem options:
2836 earlydump [X86] dump PCI config space before the kernel
2838 off [X86] don't probe for the PCI bus
2839 bios [X86-32] force use of PCI BIOS, don't access
2840 the hardware directly. Use this if your machine
2841 has a non-standard PCI host bridge.
2842 nobios [X86-32] disallow use of PCI BIOS, only direct
2843 hardware access methods are allowed. Use this
2844 if you experience crashes upon bootup and you
2845 suspect they are caused by the BIOS.
2846 conf1 [X86] Force use of PCI Configuration Access
2847 Mechanism 1 (config address in IO port 0xCF8,
2848 data in IO port 0xCFC, both 32-bit).
2849 conf2 [X86] Force use of PCI Configuration Access
2850 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
2851 the function, IO port 0xCFA, also 8-bit, sets
2852 bus number. The config space is then accessed
2853 through ports 0xC000-0xCFFF).
2854 See http://wiki.osdev.org/PCI for more info
2855 on the configuration access mechanisms.
2856 noaer [PCIE] If the PCIEAER kernel config parameter is
2857 enabled, this kernel boot option can be used to
2858 disable the use of PCIE advanced error reporting.
2859 nodomains [PCI] Disable support for multiple PCI
2860 root domains (aka PCI segments, in ACPI-speak).
2861 nommconf [X86] Disable use of MMCONFIG for PCI
2863 check_enable_amd_mmconf [X86] check for and enable
2864 properly configured MMIO access to PCI
2865 config space on AMD family 10h CPU
2866 nomsi [MSI] If the PCI_MSI kernel config parameter is
2867 enabled, this kernel boot option can be used to
2868 disable the use of MSI interrupts system-wide.
2869 noioapicquirk [APIC] Disable all boot interrupt quirks.
2870 Safety option to keep boot IRQs enabled. This
2871 should never be necessary.
2872 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2873 primary IO-APIC for bridges that cannot disable
2874 boot IRQs. This fixes a source of spurious IRQs
2875 when the system masks IRQs.
2876 noioapicreroute [APIC] Disable workaround that uses the
2877 boot IRQ equivalent of an IRQ that connects to
2878 a chipset where boot IRQs cannot be disabled.
2879 The opposite of ioapicreroute.
2880 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2881 routing table. These calls are known to be buggy
2882 on several machines and they hang the machine
2883 when used, but on other computers it's the only
2884 way to get the interrupt routing table. Try
2885 this option if the kernel is unable to allocate
2886 IRQs or discover secondary PCI buses on your
2888 rom [X86] Assign address space to expansion ROMs.
2889 Use with caution as certain devices share
2890 address decoders between ROMs and other
2892 norom [X86] Do not assign address space to
2893 expansion ROMs that do not already have
2894 BIOS assigned address ranges.
2895 nobar [X86] Do not assign address space to the
2896 BARs that weren't assigned by the BIOS.
2897 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2898 assigned automatically to PCI devices. You can
2899 make the kernel exclude IRQs of your ISA cards
2901 pirqaddr=0xAAAAA [X86] Specify the physical address
2902 of the PIRQ table (normally generated
2903 by the BIOS) if it is outside the
2904 F0000h-100000h range.
2905 lastbus=N [X86] Scan all buses thru bus #N. Can be
2906 useful if the kernel is unable to find your
2907 secondary buses and you want to tell it
2908 explicitly which ones they are.
2909 assign-busses [X86] Always assign all PCI bus
2910 numbers ourselves, overriding
2911 whatever the firmware may have done.
2912 usepirqmask [X86] Honor the possible IRQ mask stored
2913 in the BIOS $PIR table. This is needed on
2914 some systems with broken BIOSes, notably
2915 some HP Pavilion N5400 and Omnibook XE3
2916 notebooks. This will have no effect if ACPI
2917 IRQ routing is enabled.
2918 noacpi [X86] Do not use ACPI for IRQ routing
2919 or for PCI scanning.
2920 use_crs [X86] Use PCI host bridge window information
2921 from ACPI. On BIOSes from 2008 or later, this
2922 is enabled by default. If you need to use this,
2923 please report a bug.
2924 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2925 If you need to use this, please report a bug.
2926 routeirq Do IRQ routing for all PCI devices.
2927 This is normally done in pci_enable_device(),
2928 so this option is a temporary workaround
2929 for broken drivers that don't call it.
2930 skip_isa_align [X86] do not align io start addr, so can
2931 handle more pci cards
2932 noearly [X86] Don't do any early type 1 scanning.
2933 This might help on some broken boards which
2934 machine check when some devices' config space
2935 is read. But various workarounds are disabled
2936 and some IOMMU drivers will not work.
2937 bfsort Sort PCI devices into breadth-first order.
2938 This sorting is done to get a device
2939 order compatible with older (<= 2.4) kernels.
2940 nobfsort Don't sort PCI devices into breadth-first order.
2941 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2942 tuning and use the BIOS-configured MPS defaults.
2943 pcie_bus_safe Set every device's MPS to the largest value
2944 supported by all devices below the root complex.
2945 pcie_bus_perf Set device MPS to the largest allowable MPS
2946 based on its parent bus. Also set MRRS (Max
2947 Read Request Size) to the largest supported
2948 value (no larger than the MPS that the device
2949 or bus can support) for best performance.
2950 pcie_bus_peer2peer Set every device's MPS to 128B, which
2951 every device is guaranteed to support. This
2952 configuration allows peer-to-peer DMA between
2953 any pair of devices, possibly at the cost of
2954 reduced performance. This also guarantees
2955 that hot-added devices will work.
2956 cbiosize=nn[KMG] The fixed amount of bus space which is
2957 reserved for the CardBus bridge's IO window.
2958 The default value is 256 bytes.
2959 cbmemsize=nn[KMG] The fixed amount of bus space which is
2960 reserved for the CardBus bridge's memory
2961 window. The default value is 64 megabytes.
2964 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2965 [<order of align>@]pci:<vendor>:<device>\
2966 [:<subvendor>:<subdevice>][; ...]
2967 Specifies alignment and device to reassign
2968 aligned memory resources.
2969 If <order of align> is not specified,
2970 PAGE_SIZE is used as alignment.
2971 PCI-PCI bridge can be specified, if resource
2972 windows need to be expanded.
2973 To specify the alignment for several
2974 instances of a device, the PCI vendor,
2975 device, subvendor, and subdevice may be
2976 specified, e.g., 4096@pci:8086:9c22:103c:198f
2977 ecrc= Enable/disable PCIe ECRC (transaction layer
2978 end-to-end CRC checking).
2979 bios: Use BIOS/firmware settings. This is the
2983 hpiosize=nn[KMG] The fixed amount of bus space which is
2984 reserved for hotplug bridge's IO window.
2985 Default size is 256 bytes.
2986 hpmemsize=nn[KMG] The fixed amount of bus space which is
2987 reserved for hotplug bridge's memory window.
2988 Default size is 2 megabytes.
2989 hpbussize=nn The minimum amount of additional bus numbers
2990 reserved for buses below a hotplug bridge.
2992 realloc= Enable/disable reallocating PCI bridge resources
2993 if allocations done by BIOS are too small to
2994 accommodate resources required by all child
2996 off: Turn realloc off
2998 realloc same as realloc=on
2999 noari do not use PCIe ARI.
3000 pcie_scan_all Scan all possible PCIe devices. Otherwise we
3001 only look for one device below a PCIe downstream
3004 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
3007 force Enable ASPM even on devices that claim not to support it.
3008 WARNING: Forcing ASPM on may cause system lockups.
3010 pcie_hp= [PCIE] PCI Express Hotplug driver options:
3011 nomsi Do not use MSI for PCI Express Native Hotplug (this
3012 makes all PCIe ports use INTx for hotplug services).
3014 pcie_ports= [PCIE] PCIe ports handling:
3015 auto Ask the BIOS whether or not to use native PCIe services
3016 associated with PCIe ports (PME, hot-plug, AER). Use
3017 them only if that is allowed by the BIOS.
3018 native Use native PCIe services associated with PCIe ports
3020 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
3023 pcie_port_pm= [PCIE] PCIe port power management handling:
3024 off Disable power management of all PCIe ports
3025 force Forcibly enable power management of all PCIe ports
3027 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
3028 nomsi Do not use MSI for native PCIe PME signaling (this makes
3029 all PCIe root ports use INTx for all services).
3031 pcmv= [HW,PCMCIA] BadgePAD 4
3035 Keep all power-domains already enabled by bootloader on,
3036 even if no driver has claimed them. This is useful
3037 for debug and development, but should not be
3038 needed on a platform with proper driver support.
3041 See Documentation/blockdev/paride.txt.
3043 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
3046 See arch/parisc/kernel/pdc_chassis.c
3048 percpu_alloc= Select which percpu first chunk allocator to use.
3049 Currently supported values are "embed" and "page".
3050 Archs may support subset or none of the selections.
3051 See comments in mm/percpu.c for details on each
3052 allocator. This parameter is primarily for debugging
3053 and performance comparison.
3056 See Documentation/blockdev/paride.txt.
3059 See Documentation/blockdev/paride.txt.
3061 pirq= [SMP,APIC] Manual mp-table setup
3062 See Documentation/x86/i386/IO-APIC.txt.
3064 plip= [PPT,NET] Parallel port network link
3065 Format: { parport<nr> | timid | 0 }
3066 See also Documentation/parport.txt.
3068 pmtmr= [X86] Manual setup of pmtmr I/O Port.
3069 Override pmtimer IOPort with a hex value.
3073 Enable PNP debug messages (depends on the
3074 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
3075 via /sys/module/pnp/parameters/debug. We always show
3076 current resource usage; turning this on also shows
3077 possible settings and some assignment information.
3083 { on | off | curr | res | no-curr | no-res }
3086 [ISAPNP] Exclude IRQs for the autoconfiguration
3089 [ISAPNP] Exclude DMAs for the autoconfiguration
3091 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
3092 Ranges are in pairs (I/O port base and size).
3095 [ISAPNP] Exclude memory regions for the
3097 Ranges are in pairs (memory base and size).
3099 ports= [IP_VS_FTP] IPVS ftp helper module
3101 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3103 Format: <port>,<port>....
3105 powersave=off [PPC] This option disables power saving features.
3106 It specifically disables cpuidle and sets the
3107 platform machine description specific power_save
3108 function to NULL. On Idle the CPU just reduces
3111 ppc_strict_facility_enable
3112 [PPC] This option catches any kernel floating point,
3113 Altivec, VSX and SPE outside of regions specifically
3114 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3115 There is some performance impact when enabling this.
3117 print-fatal-signals=
3118 [KNL] debug: print fatal signals
3120 If enabled, warn about various signal handling
3121 related application anomalies: too many signals,
3122 too many POSIX.1 timers, fatal signals causing a
3125 If you hit the warning due to signal overflow,
3126 you might want to try "ulimit -i unlimited".
3130 printk.always_kmsg_dump=
3131 Trigger kmsg_dump for cases other than kernel oops or
3133 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3136 printk.devkmsg={on,off,ratelimit}
3137 Control writing to /dev/kmsg.
3138 on - unlimited logging to /dev/kmsg from userspace
3139 off - logging to /dev/kmsg disabled
3140 ratelimit - ratelimit the logging
3143 printk.time= Show timing data prefixed to each printk message line
3144 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3146 processor.max_cstate= [HW,ACPI]
3147 Limit processor to maximum C-state
3148 max_cstate=9 overrides any DMI blacklist limit.
3150 processor.nocst [HW,ACPI]
3151 Ignore the _CST method to determine C-states,
3152 instead using the legacy FADT method
3154 profile= [KNL] Enable kernel profiling via /proc/profile
3155 Format: [schedule,]<number>
3156 Param: "schedule" - profile schedule points.
3157 Param: <number> - step/bucket size as a power of 2 for
3158 statistical time based profiling.
3159 Param: "sleep" - profile D-state sleeping (millisecs).
3160 Requires CONFIG_SCHEDSTATS
3161 Param: "kvm" - profile VM exits.
3163 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3165 See Documentation/blockdev/ramdisk.txt.
3167 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3168 probe for; one of (bare|imps|exps|lifebook|any).
3169 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3171 psmouse.resetafter= [HW,MOUSE]
3172 Try to reset the device after so many bad packets
3175 [HW,MOUSE] Set desired mouse resolution, in dpi.
3176 psmouse.smartscroll=
3177 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3178 0 = disabled, 1 = enabled (default).
3180 pstore.backend= Specify the name of the pstore backend to use
3183 See Documentation/blockdev/paride.txt.
3186 [KNL] Number of legacy pty's. Overwrites compiled-in
3189 quiet [KNL] Disable most log messages
3194 See Documentation/admin-guide/md.rst.
3196 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3197 See Documentation/blockdev/ramdisk.txt.
3199 ras=option[,option,...] [KNL] RAS-specific options
3202 Disable the Correctable Errors Collector,
3203 see CONFIG_RAS_CEC help text.
3206 The argument is a cpu list, as described above.
3208 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3209 the specified list of CPUs to be no-callback CPUs.
3210 Invocation of these CPUs' RCU callbacks will
3211 be offloaded to "rcuox/N" kthreads created for
3212 that purpose, where "x" is "b" for RCU-bh, "p"
3213 for RCU-preempt, and "s" for RCU-sched, and "N"
3214 is the CPU number. This reduces OS jitter on the
3215 offloaded CPUs, which can be useful for HPC and
3216 real-time workloads. It can also improve energy
3217 efficiency for asymmetric multiprocessors.
3220 Rather than requiring that offloaded CPUs
3221 (specified by rcu_nocbs= above) explicitly
3222 awaken the corresponding "rcuoN" kthreads,
3223 make these kthreads poll for callbacks.
3224 This improves the real-time response for the
3225 offloaded CPUs by relieving them of the need to
3226 wake up the corresponding kthread, but degrades
3227 energy efficiency by requiring that the kthreads
3228 periodically wake up to do the polling.
3230 rcutree.blimit= [KNL]
3231 Set maximum number of finished RCU callbacks to
3232 process in one batch.
3234 rcutree.dump_tree= [KNL]
3235 Dump the structure of the rcu_node combining tree
3236 out at early boot. This is used for diagnostic
3237 purposes, to verify correct tree setup.
3239 rcutree.gp_cleanup_delay= [KNL]
3240 Set the number of jiffies to delay each step of
3241 RCU grace-period cleanup. This only has effect
3242 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3244 rcutree.gp_init_delay= [KNL]
3245 Set the number of jiffies to delay each step of
3246 RCU grace-period initialization. This only has
3247 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3250 rcutree.gp_preinit_delay= [KNL]
3251 Set the number of jiffies to delay each step of
3252 RCU grace-period pre-initialization, that is,
3253 the propagation of recent CPU-hotplug changes up
3254 the rcu_node combining tree. This only has effect
3255 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3257 rcutree.rcu_fanout_exact= [KNL]
3258 Disable autobalancing of the rcu_node combining
3259 tree. This is used by rcutorture, and might
3260 possibly be useful for architectures having high
3261 cache-to-cache transfer latencies.
3263 rcutree.rcu_fanout_leaf= [KNL]
3264 Change the number of CPUs assigned to each
3265 leaf rcu_node structure. Useful for very
3266 large systems, which will choose the value 64,
3267 and for NUMA systems with large remote-access
3268 latencies, which will choose a value aligned
3269 with the appropriate hardware boundaries.
3271 rcutree.jiffies_till_sched_qs= [KNL]
3272 Set required age in jiffies for a
3273 given grace period before RCU starts
3274 soliciting quiescent-state help from
3275 rcu_note_context_switch().
3277 rcutree.jiffies_till_first_fqs= [KNL]
3278 Set delay from grace-period initialization to
3279 first attempt to force quiescent states.
3280 Units are jiffies, minimum value is zero,
3281 and maximum value is HZ.
3283 rcutree.jiffies_till_next_fqs= [KNL]
3284 Set delay between subsequent attempts to force
3285 quiescent states. Units are jiffies, minimum
3286 value is one, and maximum value is HZ.
3288 rcutree.kthread_prio= [KNL,BOOT]
3289 Set the SCHED_FIFO priority of the RCU per-CPU
3290 kthreads (rcuc/N). This value is also used for
3291 the priority of the RCU boost threads (rcub/N)
3292 and for the RCU grace-period kthreads (rcu_bh,
3293 rcu_preempt, and rcu_sched). If RCU_BOOST is
3294 set, valid values are 1-99 and the default is 1
3295 (the least-favored priority). Otherwise, when
3296 RCU_BOOST is not set, valid values are 0-99 and
3297 the default is zero (non-realtime operation).
3299 rcutree.rcu_nocb_leader_stride= [KNL]
3300 Set the number of NOCB kthread groups, which
3301 defaults to the square root of the number of
3302 CPUs. Larger numbers reduces the wakeup overhead
3303 on the per-CPU grace-period kthreads, but increases
3304 that same overhead on each group's leader.
3306 rcutree.qhimark= [KNL]
3307 Set threshold of queued RCU callbacks beyond which
3308 batch limiting is disabled.
3310 rcutree.qlowmark= [KNL]
3311 Set threshold of queued RCU callbacks below which
3312 batch limiting is re-enabled.
3314 rcutree.rcu_idle_gp_delay= [KNL]
3315 Set wakeup interval for idle CPUs that have
3316 RCU callbacks (RCU_FAST_NO_HZ=y).
3318 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3319 Set wakeup interval for idle CPUs that have
3320 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3321 Lazy RCU callbacks are those which RCU can
3322 prove do nothing more than free memory.
3324 rcutree.rcu_kick_kthreads= [KNL]
3325 Cause the grace-period kthread to get an extra
3326 wake_up() if it sleeps three times longer than
3327 it should at force-quiescent-state time.
3328 This wake_up() will be accompanied by a
3329 WARN_ONCE() splat and an ftrace_dump().
3331 rcuperf.gp_exp= [KNL]
3332 Measure performance of expedited synchronous
3333 grace-period primitives.
3335 rcuperf.holdoff= [KNL]
3336 Set test-start holdoff period. The purpose of
3337 this parameter is to delay the start of the
3338 test until boot completes in order to avoid
3341 rcuperf.nreaders= [KNL]
3342 Set number of RCU readers. The value -1 selects
3343 N, where N is the number of CPUs. A value
3344 "n" less than -1 selects N-n+1, where N is again
3345 the number of CPUs. For example, -2 selects N
3346 (the number of CPUs), -3 selects N+1, and so on.
3347 A value of "n" less than or equal to -N selects
3350 rcuperf.nwriters= [KNL]
3351 Set number of RCU writers. The values operate
3352 the same as for rcuperf.nreaders.
3353 N, where N is the number of CPUs
3355 rcuperf.perf_runnable= [BOOT]
3356 Start rcuperf running at boot time.
3358 rcuperf.shutdown= [KNL]
3359 Shut the system down after performance tests
3360 complete. This is useful for hands-off automated
3363 rcuperf.perf_type= [KNL]
3364 Specify the RCU implementation to test.
3366 rcuperf.verbose= [KNL]
3367 Enable additional printk() statements.
3369 rcutorture.cbflood_inter_holdoff= [KNL]
3370 Set holdoff time (jiffies) between successive
3371 callback-flood tests.
3373 rcutorture.cbflood_intra_holdoff= [KNL]
3374 Set holdoff time (jiffies) between successive
3375 bursts of callbacks within a given callback-flood
3378 rcutorture.cbflood_n_burst= [KNL]
3379 Set the number of bursts making up a given
3380 callback-flood test. Set this to zero to
3381 disable callback-flood testing.
3383 rcutorture.cbflood_n_per_burst= [KNL]
3384 Set the number of callbacks to be registered
3385 in a given burst of a callback-flood test.
3387 rcutorture.fqs_duration= [KNL]
3388 Set duration of force_quiescent_state bursts
3391 rcutorture.fqs_holdoff= [KNL]
3392 Set holdoff time within force_quiescent_state bursts
3395 rcutorture.fqs_stutter= [KNL]
3396 Set wait time between force_quiescent_state bursts
3399 rcutorture.gp_cond= [KNL]
3400 Use conditional/asynchronous update-side
3401 primitives, if available.
3403 rcutorture.gp_exp= [KNL]
3404 Use expedited update-side primitives, if available.
3406 rcutorture.gp_normal= [KNL]
3407 Use normal (non-expedited) asynchronous
3408 update-side primitives, if available.
3410 rcutorture.gp_sync= [KNL]
3411 Use normal (non-expedited) synchronous
3412 update-side primitives, if available. If all
3413 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3414 rcutorture.gp_normal=, and rcutorture.gp_sync=
3415 are zero, rcutorture acts as if is interpreted
3416 they are all non-zero.
3418 rcutorture.n_barrier_cbs= [KNL]
3419 Set callbacks/threads for rcu_barrier() testing.
3421 rcutorture.nfakewriters= [KNL]
3422 Set number of concurrent RCU writers. These just
3423 stress RCU, they don't participate in the actual
3424 test, hence the "fake".
3426 rcutorture.nreaders= [KNL]
3427 Set number of RCU readers. The value -1 selects
3428 N-1, where N is the number of CPUs. A value
3429 "n" less than -1 selects N-n-2, where N is again
3430 the number of CPUs. For example, -2 selects N
3431 (the number of CPUs), -3 selects N+1, and so on.
3433 rcutorture.object_debug= [KNL]
3434 Enable debug-object double-call_rcu() testing.
3436 rcutorture.onoff_holdoff= [KNL]
3437 Set time (s) after boot for CPU-hotplug testing.
3439 rcutorture.onoff_interval= [KNL]
3440 Set time (s) between CPU-hotplug operations, or
3441 zero to disable CPU-hotplug testing.
3443 rcutorture.shuffle_interval= [KNL]
3444 Set task-shuffle interval (s). Shuffling tasks
3445 allows some CPUs to go into dyntick-idle mode
3446 during the rcutorture test.
3448 rcutorture.shutdown_secs= [KNL]
3449 Set time (s) after boot system shutdown. This
3450 is useful for hands-off automated testing.
3452 rcutorture.stall_cpu= [KNL]
3453 Duration of CPU stall (s) to test RCU CPU stall
3454 warnings, zero to disable.
3456 rcutorture.stall_cpu_holdoff= [KNL]
3457 Time to wait (s) after boot before inducing stall.
3459 rcutorture.stat_interval= [KNL]
3460 Time (s) between statistics printk()s.
3462 rcutorture.stutter= [KNL]
3463 Time (s) to stutter testing, for example, specifying
3464 five seconds causes the test to run for five seconds,
3465 wait for five seconds, and so on. This tests RCU's
3466 ability to transition abruptly to and from idle.
3468 rcutorture.test_boost= [KNL]
3469 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3470 "Maybe" means test if the RCU implementation
3471 under test support RCU priority boosting.
3473 rcutorture.test_boost_duration= [KNL]
3474 Duration (s) of each individual boost test.
3476 rcutorture.test_boost_interval= [KNL]
3477 Interval (s) between each boost test.
3479 rcutorture.test_no_idle_hz= [KNL]
3480 Test RCU's dyntick-idle handling. See also the
3481 rcutorture.shuffle_interval parameter.
3483 rcutorture.torture_runnable= [BOOT]
3484 Start rcutorture running at boot time.
3486 rcutorture.torture_type= [KNL]
3487 Specify the RCU implementation to test.
3489 rcutorture.verbose= [KNL]
3490 Enable additional printk() statements.
3492 rcupdate.rcu_cpu_stall_suppress= [KNL]
3493 Suppress RCU CPU stall warning messages.
3495 rcupdate.rcu_cpu_stall_timeout= [KNL]
3496 Set timeout for RCU CPU stall warning messages.
3498 rcupdate.rcu_expedited= [KNL]
3499 Use expedited grace-period primitives, for
3500 example, synchronize_rcu_expedited() instead
3501 of synchronize_rcu(). This reduces latency,
3502 but can increase CPU utilization, degrade
3503 real-time latency, and degrade energy efficiency.
3504 No effect on CONFIG_TINY_RCU kernels.
3506 rcupdate.rcu_normal= [KNL]
3507 Use only normal grace-period primitives,
3508 for example, synchronize_rcu() instead of
3509 synchronize_rcu_expedited(). This improves
3510 real-time latency, CPU utilization, and
3511 energy efficiency, but can expose users to
3512 increased grace-period latency. This parameter
3513 overrides rcupdate.rcu_expedited. No effect on
3514 CONFIG_TINY_RCU kernels.
3516 rcupdate.rcu_normal_after_boot= [KNL]
3517 Once boot has completed (that is, after
3518 rcu_end_inkernel_boot() has been invoked), use
3519 only normal grace-period primitives. No effect
3520 on CONFIG_TINY_RCU kernels.
3522 rcupdate.rcu_task_stall_timeout= [KNL]
3523 Set timeout in jiffies for RCU task stall warning
3524 messages. Disable with a value less than or equal
3527 rcupdate.rcu_self_test= [KNL]
3528 Run the RCU early boot self tests
3530 rcupdate.rcu_self_test_bh= [KNL]
3531 Run the RCU bh early boot self tests
3533 rcupdate.rcu_self_test_sched= [KNL]
3534 Run the RCU sched early boot self tests
3538 Run specified binary instead of /init from the ramdisk,
3539 used for early userspace startup. See initrd.
3542 Format (x86 or x86_64):
3543 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3545 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3547 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3548 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3549 reboot_force is either force or not specified,
3550 reboot_cpu is s[mp]#### with #### being the processor
3551 to be used for rebooting.
3554 [KNL, SMP] Set scheduler's default relax_domain_level.
3555 See Documentation/cgroup-v1/cpusets.txt.
3557 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3559 reservetop= [X86-32]
3561 Reserves a hole at the top of the kernel virtual
3566 Set the amount of memory to reserve for BIOS at
3567 the bottom of the address space.
3569 reset_devices [KNL] Force drivers to reset the underlying device
3570 during initialization.
3573 Specify the partition device for software suspend
3575 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3577 resume_offset= [SWSUSP]
3578 Specify the offset from the beginning of the partition
3579 given by "resume=" at which the swap header is located,
3580 in <PAGE_SIZE> units (needed only for swap files).
3581 See Documentation/power/swsusp-and-swap-files.txt
3583 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3584 read the resume files
3586 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3587 Useful for devices that are detected asynchronously
3588 (e.g. USB and MMC devices).
3590 hibernate= [HIBERNATION]
3591 noresume Don't check if there's a hibernation image
3592 present during boot.
3593 nocompress Don't compress/decompress hibernation images.
3594 no Disable hibernation and resume.
3595 protect_image Turn on image protection during restoration
3596 (that will set all pages holding image data
3597 during restoration read-only).
3599 retain_initrd [RAM] Keep initrd memory after extraction
3601 rfkill.default_state=
3602 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3603 etc. communication is blocked by default.
3606 rfkill.master_switch_mode=
3607 0 The "airplane mode" button does nothing.
3608 1 The "airplane mode" button toggles between everything
3609 blocked and the previous configuration.
3610 2 The "airplane mode" button toggles between everything
3611 blocked and everything unblocked.
3613 rhash_entries= [KNL,NET]
3614 Set number of hash buckets for route cache
3617 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
3620 ro [KNL] Mount root device read-only on boot
3623 on Mark read-only kernel memory as read-only (default).
3624 off Leave read-only kernel memory writable for debugging.
3627 Enable the uart passthrough on the designated usb port
3628 on Rockchip SoCs. When active, the signals of the
3629 debug-uart get routed to the D+ and D- pins of the usb
3630 port and the regular usb controller gets disabled.
3632 root= [KNL] Root filesystem
3633 See name_to_dev_t comment in init/do_mounts.c.
3635 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3636 mount the root filesystem
3638 rootflags= [KNL] Set root filesystem mount option string
3640 rootfstype= [KNL] Set root filesystem type
3642 rootwait [KNL] Wait (indefinitely) for root device to show up.
3643 Useful for devices that are detected asynchronously
3644 (e.g. USB and MMC devices).
3646 rproc_mem=nn[KMG][@address]
3647 [KNL,ARM,CMA] Remoteproc physical memory block.
3648 Memory area to be used by remote processor image,
3651 rw [KNL] Mount root device read-write on boot
3653 S [KNL] Run init in single mode
3655 s390_iommu= [HW,S390]
3656 Set s390 IOTLB flushing mode
3658 With strict flushing every unmap operation will result in
3659 an IOTLB flush. Default is lazy flushing before reuse,
3663 See drivers/net/irda/sa1100_ir.c.
3665 sbni= [NET] Granch SBNI12 leased line adapter
3667 sched_debug [KNL] Enables verbose scheduler debug messages.
3669 schedstats= [KNL,X86] Enable or disable scheduled statistics.
3670 Allowed values are enable and disable. This feature
3671 incurs a small amount of overhead in the scheduler
3672 but is useful for debugging and performance tuning.
3674 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3675 xtime_lock contention on larger systems, and/or RCU lock
3676 contention on all systems with CONFIG_MAXSMP set.
3677 Format: { "0" | "1" }
3678 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3680 Note: increases power consumption, thus should only be
3681 enabled if running jitter sensitive (HPC/RT) workloads.
3683 security= [SECURITY] Choose a security module to enable at boot.
3684 If this boot parameter is not specified, only the first
3685 security module asking for security registration will be
3686 loaded. An invalid security module name will be treated
3687 as if no module has been chosen.
3689 selinux= [SELINUX] Disable or enable SELinux at boot time.
3690 Format: { "0" | "1" }
3691 See security/selinux/Kconfig help text.
3694 Default value is set via kernel config option.
3695 If enabled at boot time, /selinux/disable can be used
3696 later to disable prior to initial policy load.
3698 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3699 Format: { "0" | "1" }
3700 See security/apparmor/Kconfig help text
3703 Default value is set via kernel config option.
3705 serialnumber [BUGS=X86-32]
3708 Maximal number of shapers.
3716 Disable merging of slabs with similar size. May be
3717 necessary if there is some reason to distinguish
3718 allocs to different slabs. Debug options disable
3719 merging on their own.
3720 For more information see Documentation/vm/slub.txt.
3722 slab_max_order= [MM, SLAB]
3723 Determines the maximum allowed order for slabs.
3724 A high setting may cause OOMs due to memory
3725 fragmentation. Defaults to 1 for systems with
3726 more than 32MB of RAM, 0 otherwise.
3728 slub_debug[=options[,slabs]] [MM, SLUB]
3729 Enabling slub_debug allows one to determine the
3730 culprit if slab objects become corrupted. Enabling
3731 slub_debug can create guard zones around objects and
3732 may poison objects when not in use. Also tracks the
3733 last alloc / free. For more information see
3734 Documentation/vm/slub.txt.
3736 slub_memcg_sysfs= [MM, SLUB]
3737 Determines whether to enable sysfs directories for
3738 memory cgroup sub-caches. 1 to enable, 0 to disable.
3739 The default is determined by CONFIG_SLUB_MEMCG_SYSFS_ON.
3740 Enabling this can lead to a very high number of debug
3741 directories and files being created under
3744 slub_max_order= [MM, SLUB]
3745 Determines the maximum allowed order for slabs.
3746 A high setting may cause OOMs due to memory
3747 fragmentation. For more information see
3748 Documentation/vm/slub.txt.
3750 slub_min_objects= [MM, SLUB]
3751 The minimum number of objects per slab. SLUB will
3752 increase the slab order up to slub_max_order to
3753 generate a sufficiently large slab able to contain
3754 the number of objects indicated. The higher the number
3755 of objects the smaller the overhead of tracking slabs
3756 and the less frequently locks need to be acquired.
3757 For more information see Documentation/vm/slub.txt.
3759 slub_min_order= [MM, SLUB]
3760 Determines the minimum page order for slabs. Must be
3761 lower than slub_max_order.
3762 For more information see Documentation/vm/slub.txt.
3764 slub_nomerge [MM, SLUB]
3765 Same with slab_nomerge. This is supported for legacy.
3766 See slab_nomerge for more information.
3769 Format: <io1>[,<io2>[,...,<io8>]]
3771 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3772 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3773 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3774 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3775 smsc-ircc2.ircc_irq= [HW] IRQ line
3776 smsc-ircc2.ircc_dma= [HW] DMA channel
3777 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3778 0: Toshiba Satellite 1800 (GP data pin select)
3779 1: Fast pin select (default)
3782 smt [KNL,S390] Set the maximum number of threads (logical
3783 CPUs) to use per physical CPU on systems capable of
3784 symmetric multithreading (SMT). Will be capped to the
3785 actual hardware limit.
3787 Default: -1 (no limit)
3790 [KNL] Should the soft-lockup detector generate panics.
3793 softlockup_all_cpu_backtrace=
3794 [KNL] Should the soft-lockup detector generate
3795 backtraces on all cpus.
3798 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3799 See Documentation/laptops/sonypi.txt
3801 spia_io_base= [HW,MTD]
3806 srcutree.exp_holdoff [KNL]
3807 Specifies how many nanoseconds must elapse
3808 since the end of the last SRCU grace period for
3809 a given srcu_struct until the next normal SRCU
3810 grace period will be considered for automatic
3811 expediting. Set to zero to disable automatic
3814 stack_guard_gap= [MM]
3815 override the default stack gap protection. The value
3816 is in page units and it defines how many pages prior
3817 to (for stacks growing down) resp. after (for stacks
3818 growing up) the main stack are reserved for no other
3819 mapping. Default value is 256 pages.
3822 Enabled the stack tracer on boot up.
3824 stacktrace_filter=[function-list]
3825 [FTRACE] Limit the functions that the stack tracer
3826 will trace at boot up. function-list is a comma separated
3827 list of functions. This list can be changed at run
3828 time by the stack_trace_filter file in the debugfs
3829 tracing directory. Note, this enables stack tracing
3830 and the stacktrace above is not needed.
3834 Set the STI (builtin display/keyboard on the HP-PARISC
3835 machines) console (graphic card) which should be used
3836 as the initial boot-console.
3837 See also comment in drivers/video/console/sticore.c.
3840 See comment in drivers/video/console/sticore.c.
3843 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3845 sunrpc.min_resvport=
3846 sunrpc.max_resvport=
3848 SunRPC servers often require that client requests
3849 originate from a privileged port (i.e. a port in the
3850 range 0 < portnr < 1024).
3851 An administrator who wishes to reserve some of these
3852 ports for other uses may adjust the range that the
3853 kernel's sunrpc client considers to be privileged
3854 using these two parameters to set the minimum and
3855 maximum port values.
3857 sunrpc.svc_rpc_per_connection_limit=
3859 Limit the number of requests that the server will
3860 process in parallel from a single connection.
3861 The default value is 0 (no limit).
3865 Control how the NFS server code allocates CPUs to
3866 service thread pools. Depending on how many NICs
3867 you have and where their interrupts are bound, this
3868 option will affect which CPUs will do NFS serving.
3869 Note: this parameter cannot be changed while the
3870 NFS server is running.
3872 auto the server chooses an appropriate mode
3873 automatically using heuristics
3874 global a single global pool contains all CPUs
3875 percpu one pool for each CPU
3876 pernode one pool for each NUMA node (equivalent
3877 to global on non-NUMA machines)
3879 sunrpc.tcp_slot_table_entries=
3880 sunrpc.udp_slot_table_entries=
3882 Sets the upper limit on the number of simultaneous
3883 RPC calls that can be sent from the client to a
3884 server. Increasing these values may allow you to
3885 improve throughput, but will also increase the
3886 amount of memory reserved for use by the client.
3888 suspend.pm_test_delay=
3890 Sets the number of seconds to remain in a suspend test
3891 mode before resuming the system (see
3892 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3893 is set. Default value is 5.
3896 [KNL] Enable accounting of swap in memory resource
3897 controller if no parameter or 1 is given or disable
3898 it if 0 is given (See Documentation/cgroup-v1/memory.txt)
3900 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3901 Format: { <int> | force | noforce }
3902 <int> -- Number of I/O TLB slabs
3903 force -- force using of bounce buffers even if they
3904 wouldn't be automatically used by the kernel
3905 noforce -- Never use bounce buffers (for debugging)
3909 sysfs.deprecated=0|1 [KNL]
3910 Enable/disable old style sysfs layout for old udev
3911 on older distributions. When this option is enabled
3912 very new udev will not work anymore. When this option
3913 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3914 in older udev will not work anymore.
3915 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3916 the kernel configuration.
3918 sysrq_always_enabled
3920 Ignore sysrq setting - this boot parameter will
3921 neutralize any effect of /proc/sys/kernel/sysrq.
3922 Useful for debugging.
3924 tcpmhash_entries= [KNL,NET]
3925 Set the number of tcp_metrics_hash slots.
3926 Default value is 8192 or 16384 depending on total
3927 ram pages. This is used to specify the TCP metrics
3928 cache size. See Documentation/networking/ip-sysctl.txt
3929 "tcp_no_metrics_save" section for more details.
3933 test_suspend= [SUSPEND][,N]
3934 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3935 standby suspend) or "freeze" (for suspend type freeze)
3936 as the system sleep state during system startup with
3937 the optional capability to repeat N number of times.
3938 The system is woken from this state using a
3939 wakeup-capable RTC alarm.
3941 thash_entries= [KNL,NET]
3942 Set number of hash buckets for TCP connection
3944 thermal.act= [HW,ACPI]
3945 -1: disable all active trip points in all thermal zones
3946 <degrees C>: override all lowest active trip points
3948 thermal.crt= [HW,ACPI]
3949 -1: disable all critical trip points in all thermal zones
3950 <degrees C>: override all critical trip points
3952 thermal.nocrt= [HW,ACPI]
3953 Set to disable actions on ACPI thermal zone
3954 critical and hot trip points.
3956 thermal.off= [HW,ACPI]
3957 1: disable ACPI thermal control
3959 thermal.psv= [HW,ACPI]
3960 -1: disable all passive trip points
3961 <degrees C>: override all passive trip points to this
3964 thermal.tzp= [HW,ACPI]
3965 Specify global default ACPI thermal zone polling rate
3966 <deci-seconds>: poll all this frequency
3967 0: no polling (default)
3970 Force threading of all interrupt handlers except those
3971 marked explicitly IRQF_NO_THREAD.
3974 Enable the Transcendent memory driver if built-in.
3976 tmem.cleancache=0|1 [KNL, XEN]
3977 Default is on (1). Disable the usage of the cleancache
3978 API to send anonymous pages to the hypervisor.
3980 tmem.frontswap=0|1 [KNL, XEN]
3981 Default is on (1). Disable the usage of the frontswap
3982 API to send swap pages to the hypervisor. If disabled
3983 the selfballooning and selfshrinking are force disabled.
3985 tmem.selfballooning=0|1 [KNL, XEN]
3986 Default is on (1). Disable the driving of swap pages
3989 tmem.selfshrinking=0|1 [KNL, XEN]
3990 Default is on (1). Partial swapoff that immediately
3991 transfers pages from Xen hypervisor back to the
3992 kernel based on different criteria.
3996 Specify if the kernel should make use of the cpu
3997 topology information if the hardware supports this.
3998 The scheduler will make use of this information and
3999 e.g. base its process migration decisions on it.
4002 topology_updates= [KNL, PPC, NUMA]
4004 Specify if the kernel should ignore (off)
4005 topology updates sent by the hypervisor to this
4010 tpm_suspend_pcr=[HW,TPM]
4011 Format: integer pcr id
4012 Specify that at suspend time, the tpm driver
4013 should extend the specified pcr with zeros,
4014 as a workaround for some chips which fail to
4015 flush the last written pcr on TPM_SaveState.
4016 This will guarantee that all the other pcrs
4019 trace_buf_size=nn[KMG]
4020 [FTRACE] will set tracing buffer size on each cpu.
4022 trace_event=[event-list]
4023 [FTRACE] Set and start specified trace events in order
4024 to facilitate early boot debugging. The event-list is a
4025 comma separated list of trace events to enable. See
4026 also Documentation/trace/events.txt
4028 trace_options=[option-list]
4029 [FTRACE] Enable or disable tracer options at boot.
4030 The option-list is a comma delimited list of options
4031 that can be enabled or disabled just as if you were
4032 to echo the option name into
4034 /sys/kernel/debug/tracing/trace_options
4036 For example, to enable stacktrace option (to dump the
4037 stack trace of each event), add to the command line:
4039 trace_options=stacktrace
4041 See also Documentation/trace/ftrace.txt "trace options"
4045 Have the tracepoints sent to printk as well as the
4046 tracing ring buffer. This is useful for early boot up
4047 where the system hangs or reboots and does not give the
4048 option for reading the tracing buffer or performing a
4049 ftrace_dump_on_oops.
4051 To turn off having tracepoints sent to printk,
4052 echo 0 > /proc/sys/kernel/tracepoint_printk
4053 Note, echoing 1 into this file without the
4054 tracepoint_printk kernel cmdline option has no effect.
4058 Having tracepoints sent to printk() and activating high
4059 frequency tracepoints such as irq or sched, can cause
4060 the system to live lock.
4063 [FTRACE] enable this option to disable tracing when a
4064 warning is hit. This turns off "tracing_on". Tracing can
4065 be enabled again by echoing '1' into the "tracing_on"
4066 file located in /sys/kernel/debug/tracing/
4068 This option is useful, as it disables the trace before
4069 the WARNING dump is called, which prevents the trace to
4070 be filled with content caused by the warning output.
4072 This option can also be set at run time via the sysctl
4073 option: kernel/traceoff_on_warning
4075 transparent_hugepage=
4077 Format: [always|madvise|never]
4078 Can be used to control the default behavior of the system
4079 with respect to transparent hugepages.
4080 See Documentation/vm/transhuge.txt for more details.
4082 tsc= Disable clocksource stability checks for TSC.
4084 [x86] reliable: mark tsc clocksource as reliable, this
4085 disables clocksource verification at runtime, as well
4086 as the stability checks done at bootup. Used to enable
4087 high-resolution timer mode on older hardware, and in
4088 virtualized environment.
4089 [x86] noirqtime: Do not use TSC to do irq accounting.
4090 Used to run time disable IRQ_TIME_ACCOUNTING on any
4091 platforms where RDTSC is slow and this accounting
4094 turbografx.map[2|3]= [HW,JOY]
4095 TurboGraFX parallel port interface
4097 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
4098 See also Documentation/input/joystick-parport.txt
4100 udbg-immortal [PPC] When debugging early kernel crashes that
4101 happen after console_init() and before a proper
4102 console driver takes over, this boot options might
4103 help "seeing" what's going on.
4105 uhash_entries= [KNL,NET]
4106 Set number of hash buckets for UDP/UDP-Lite connections
4109 [USB] Ignore overcurrent events (default N).
4110 Some badly-designed motherboards generate lots of
4111 bogus events, for ports that aren't wired to
4112 anything. Set this parameter to avoid log spamming.
4113 Note that genuine overcurrent events won't be
4117 [X86] Cause panic on unknown NMI.
4119 usbcore.authorized_default=
4120 [USB] Default USB device authorization:
4121 (default -1 = authorized except for wireless USB,
4122 0 = not authorized, 1 = authorized)
4124 usbcore.autosuspend=
4125 [USB] The autosuspend time delay (in seconds) used
4126 for newly-detected USB devices (default 2). This
4127 is the time required before an idle device will be
4128 autosuspended. Devices for which the delay is set
4129 to a negative value won't be autosuspended at all.
4131 usbcore.usbfs_snoop=
4132 [USB] Set to log all usbfs traffic (default 0 = off).
4134 usbcore.usbfs_snoop_max=
4135 [USB] Maximum number of bytes to snoop in each URB
4138 usbcore.blinkenlights=
4139 [USB] Set to cycle leds on hubs (default 0 = off).
4141 usbcore.old_scheme_first=
4142 [USB] Start with the old device initialization
4143 scheme (default 0 = off).
4145 usbcore.usbfs_memory_mb=
4146 [USB] Memory limit (in MB) for buffers allocated by
4147 usbfs (default = 16, 0 = max = 2047).
4149 usbcore.use_both_schemes=
4150 [USB] Try the other device initialization scheme
4151 if the first one fails (default 1 = enabled).
4153 usbcore.initial_descriptor_timeout=
4154 [USB] Specifies timeout for the initial 64-byte
4155 USB_REQ_GET_DESCRIPTOR request in milliseconds
4156 (default 5000 = 5.0 seconds).
4158 usbcore.nousb [USB] Disable the USB subsystem
4161 [USBHID] The interval which mice are to be polled at.
4164 [USBHID] The interval which joysticks are to be polled at.
4166 usb-storage.delay_use=
4167 [UMS] The delay in seconds before a new device is
4168 scanned for Logical Units (default 1).
4171 [UMS] A list of quirks entries to supplement or
4172 override the built-in unusual_devs list. List
4173 entries are separated by commas. Each entry has
4174 the form VID:PID:Flags where VID and PID are Vendor
4175 and Product ID values (4-digit hex numbers) and
4176 Flags is a set of characters, each corresponding
4177 to a common usb-storage quirk flag as follows:
4178 a = SANE_SENSE (collect more than 18 bytes
4180 b = BAD_SENSE (don't collect more than 18
4181 bytes of sense data);
4182 c = FIX_CAPACITY (decrease the reported
4183 device capacity by one sector);
4184 d = NO_READ_DISC_INFO (don't use
4185 READ_DISC_INFO command);
4186 e = NO_READ_CAPACITY_16 (don't use
4187 READ_CAPACITY_16 command);
4188 f = NO_REPORT_OPCODES (don't use report opcodes
4190 g = MAX_SECTORS_240 (don't transfer more than
4191 240 sectors at a time, uas only);
4192 h = CAPACITY_HEURISTICS (decrease the
4193 reported device capacity by one
4194 sector if the number is odd);
4195 i = IGNORE_DEVICE (don't bind to this
4197 j = NO_REPORT_LUNS (don't use report luns
4199 l = NOT_LOCKABLE (don't try to lock and
4200 unlock ejectable media);
4201 m = MAX_SECTORS_64 (don't transfer more
4202 than 64 sectors = 32 KB at a time);
4203 n = INITIAL_READ10 (force a retry of the
4204 initial READ(10) command);
4205 o = CAPACITY_OK (accept the capacity
4206 reported by the device);
4207 p = WRITE_CACHE (the device cache is ON
4209 r = IGNORE_RESIDUE (the device reports
4210 bogus residue values);
4211 s = SINGLE_LUN (the device has only one
4213 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4214 commands, uas only);
4215 u = IGNORE_UAS (don't bind to the uas driver);
4216 w = NO_WP_DETECT (don't test whether the
4217 medium is write-protected).
4218 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
4219 even if the device claims no cache)
4220 Example: quirks=0419:aaf5:rl,0421:0433:rc
4222 user_debug= [KNL,ARM]
4224 See arch/arm/Kconfig.debug help text.
4225 1 - undefined instruction events
4227 4 - invalid data aborts
4230 Example: user_debug=31
4233 [X86] Flags controlling user PTE allocations.
4235 nohigh = do not allocate PTE pages in
4236 HIGHMEM regardless of setting
4240 On X86_32, this is an alias for vdso32=. Otherwise:
4242 vdso=1: enable VDSO (the default)
4243 vdso=0: disable VDSO mapping
4245 vdso32= [X86] Control the 32-bit vDSO
4246 vdso32=1: enable 32-bit VDSO
4247 vdso32=0 or vdso32=2: disable 32-bit VDSO
4249 See the help text for CONFIG_COMPAT_VDSO for more
4250 details. If CONFIG_COMPAT_VDSO is set, the default is
4251 vdso32=0; otherwise, the default is vdso32=1.
4253 For compatibility with older kernels, vdso32=2 is an
4256 Try vdso32=0 if you encounter an error that says:
4257 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
4260 vector=percpu: enable percpu vector domain
4262 video= [FB] Frame buffer configuration
4263 See Documentation/fb/modedb.txt.
4265 video.brightness_switch_enabled= [0,1]
4266 If set to 1, on receiving an ACPI notify event
4267 generated by hotkey, video driver will adjust brightness
4268 level and then send out the event to user space through
4269 the allocated input device; If set to 0, video driver
4270 will only send out the event without touching backlight
4275 [VMMIO] Memory mapped virtio (platform) device.
4277 <size>@<baseaddr>:<irq>[:<id>]
4279 <size> := size (can use standard suffixes
4281 <baseaddr> := physical base address
4282 <irq> := interrupt number (as passed to
4284 <id> := (optional) platform device id
4286 virtio_mmio.device=1K@0x100b0000:48:7
4288 Can be used multiple times for multiple devices.
4290 vga= [BOOT,X86-32] Select a particular video mode
4291 See Documentation/x86/boot.txt and
4292 Documentation/svga.txt.
4293 Use vga=ask for menu.
4294 This is actually a boot loader parameter; the value is
4295 passed to the kernel using a special protocol.
4297 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4298 size of <nn>. This can be used to increase the
4299 minimum size (128MB on x86). It can also be used to
4300 decrease the size and leave more room for directly
4303 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4306 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4309 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4313 Controls the behavior of vsyscalls (i.e. calls to
4314 fixed addresses of 0xffffffffff600x00 from legacy
4315 code). Most statically-linked binaries and older
4316 versions of glibc use these calls. Because these
4317 functions are at fixed addresses, they make nice
4318 targets for exploits that can control RIP.
4320 emulate [default] Vsyscalls turn into traps and are
4321 emulated reasonably safely.
4323 native Vsyscalls are native syscall instructions.
4324 This is a little bit faster than trapping
4325 and makes a few dynamic recompilers work
4326 better than they would in emulation mode.
4327 It also makes exploits much easier to write.
4329 none Vsyscalls don't work at all. This makes
4330 them quite hard to use for exploits but
4331 might break your system.
4333 vt.color= [VT] Default text color.
4334 Format: 0xYX, X = foreground, Y = background.
4335 Default: 0x07 = light gray on black.
4337 vt.cur_default= [VT] Default cursor shape.
4338 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4339 the parameters of the <Esc>[?A;B;Cc escape sequence;
4340 see VGA-softcursor.txt. Default: 2 = underline.
4342 vt.default_blu= [VT]
4343 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4344 Change the default blue palette of the console.
4345 This is a 16-member array composed of values
4348 vt.default_grn= [VT]
4349 Format: <green0>,<green1>,<green2>,...,<green15>
4350 Change the default green palette of the console.
4351 This is a 16-member array composed of values
4354 vt.default_red= [VT]
4355 Format: <red0>,<red1>,<red2>,...,<red15>
4356 Change the default red palette of the console.
4357 This is a 16-member array composed of values
4363 Set system-wide default UTF-8 mode for all tty's.
4364 Default is 1, i.e. UTF-8 mode is enabled for all
4365 newly opened terminals.
4367 vt.global_cursor_default=
4370 Set system-wide default for whether a cursor
4371 is shown on new VTs. Default is -1,
4372 i.e. cursors will be created by default unless
4373 overridden by individual drivers. 0 will hide
4374 cursors, 1 will display them.
4376 vt.italic= [VT] Default color for italic text; 0-15.
4379 vt.underline= [VT] Default color for underlined text; 0-15.
4382 watchdog timers [HW,WDT] For information on watchdog timers,
4383 see Documentation/watchdog/watchdog-parameters.txt
4384 or other driver-specific files in the
4385 Documentation/watchdog/ directory.
4387 workqueue.watchdog_thresh=
4388 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4389 warn stall conditions and dump internal state to
4390 help debugging. 0 disables workqueue stall
4391 detection; otherwise, it's the stall threshold
4392 duration in seconds. The default value is 30 and
4393 it can be updated at runtime by writing to the
4394 corresponding sysfs file.
4396 workqueue.disable_numa
4397 By default, all work items queued to unbound
4398 workqueues are affine to the NUMA nodes they're
4399 issued on, which results in better behavior in
4400 general. If NUMA affinity needs to be disabled for
4401 whatever reason, this option can be used. Note
4402 that this also can be controlled per-workqueue for
4403 workqueues visible under /sys/bus/workqueue/.
4405 workqueue.power_efficient
4406 Per-cpu workqueues are generally preferred because
4407 they show better performance thanks to cache
4408 locality; unfortunately, per-cpu workqueues tend to
4409 be more power hungry than unbound workqueues.
4411 Enabling this makes the per-cpu workqueues which
4412 were observed to contribute significantly to power
4413 consumption unbound, leading to measurably lower
4414 power usage at the cost of small performance
4417 The default value of this parameter is determined by
4418 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4420 workqueue.debug_force_rr_cpu
4421 Workqueue used to implicitly guarantee that work
4422 items queued without explicit CPU specified are put
4423 on the local CPU. This guarantee is no longer true
4424 and while local CPU is still preferred work items
4425 may be put on foreign CPUs. This debug option
4426 forces round-robin CPU selection to flush out
4427 usages which depend on the now broken guarantee.
4428 When enabled, memory and cache locality will be
4431 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4432 default x2apic cluster mode on platforms
4435 x86_intel_mid_timer= [X86-32,APBT]
4436 Choose timer option for x86 Intel MID platform.
4437 Two valid options are apbt timer only and lapic timer
4438 plus one apbt timer for broadcast timer.
4439 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4441 xen_512gb_limit [KNL,X86-64,XEN]
4442 Restricts the kernel running paravirtualized under Xen
4443 to use only up to 512 GB of RAM. The reason to do so is
4444 crash analysis tools and Xen tools for doing domain
4445 save/restore/migration must be enabled to handle larger
4448 xen_emul_unplug= [HW,X86,XEN]
4449 Unplug Xen emulated devices
4450 Format: [unplug0,][unplug1]
4451 ide-disks -- unplug primary master IDE devices
4452 aux-ide-disks -- unplug non-primary-master IDE devices
4453 nics -- unplug network devices
4454 all -- unplug all emulated devices (NICs and IDE disks)
4455 unnecessary -- unplugging emulated devices is
4456 unnecessary even if the host did not respond to
4458 never -- do not unplug even if version check succeeds
4460 xen_nopvspin [X86,XEN]
4461 Disables the ticketlock slowpath using Xen PV
4465 Disables the PV optimizations forcing the HVM guest to
4466 run as generic HVM guest with no PV drivers.
4468 xirc2ps_cs= [NET,PCMCIA]
4470 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
git.samba.org / sfrench / cifs-2.6.git / blob