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
535 [X86-32] pit,hpet,tsc;
536 scx200_hrt on Geode; cyclone on IBM x440
544 clocksource.arm_arch_timer.evtstrm=
547 Enable/disable the eventstream feature of the ARM
548 architected timer so that code using WFE-based polling
549 loops can be debugged more effectively on production
552 clearcpuid=BITNUM [X86]
553 Disable CPUID feature X for the kernel. See
554 arch/x86/include/asm/cpufeatures.h for the valid bit
555 numbers. Note the Linux specific bits are not necessarily
556 stable over kernel options, but the vendor specific
558 Also note that user programs calling CPUID directly
559 or using the feature without checking anything
560 will still see it. This just prevents it from
561 being used by the kernel or shown in /proc/cpuinfo.
562 Also note the kernel might malfunction if you disable
565 cma=nn[MG]@[start[MG][-end[MG]]]
567 Sets the size of kernel global memory area for
568 contiguous memory allocations and optionally the
569 placement constraint by the physical address range of
570 memory allocations. A value of 0 disables CMA
571 altogether. For more information, see
572 include/linux/dma-contiguous.h
574 cmo_free_hint= [PPC] Format: { yes | no }
575 Specify whether pages are marked as being inactive
576 when they are freed. This is used in CMO environments
577 to determine OS memory pressure for page stealing by
581 coherent_pool=nn[KMG] [ARM,KNL]
582 Sets the size of memory pool for coherent, atomic dma
583 allocations, by default set to 256K.
585 code_bytes [X86] How many bytes of object code to print
590 com20020= [HW,NET] ARCnet - COM20020 chipset
592 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
594 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
598 ARCnet - COM90xx chipset (memory-mapped buffers)
599 Format: <io>[,<irq>[,<memstart>]]
601 condev= [HW,S390] console device
604 console= [KNL] Output console device and options.
606 tty<n> Use the virtual console device <n>.
610 Use the specified serial port. The options are of
611 the form "bbbbpnf", where "bbbb" is the baud rate,
612 "p" is parity ("n", "o", or "e"), "n" is number of
613 bits, and "f" is flow control ("r" for RTS or
614 omit it). Default is "9600n8".
616 See Documentation/admin-guide/serial-console.rst for more
618 Documentation/networking/netconsole.txt for an
621 uart[8250],io,<addr>[,options]
622 uart[8250],mmio,<addr>[,options]
623 uart[8250],mmio16,<addr>[,options]
624 uart[8250],mmio32,<addr>[,options]
625 uart[8250],0x<addr>[,options]
626 Start an early, polled-mode console on the 8250/16550
627 UART at the specified I/O port or MMIO address,
628 switching to the matching ttyS device later.
629 MMIO inter-register address stride is either 8-bit
630 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
631 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
632 to be equivalent to 'mmio'. 'options' are specified in
633 the same format described for ttyS above; if unspecified,
634 the h/w is not re-initialized.
636 hvc<n> Use the hypervisor console device <n>. This is for
637 both Xen and PowerPC hypervisors.
639 If the device connected to the port is not a TTY but a braille
640 device, prepend "brl," before the device type, for instance
642 For now, only VisioBraille is supported.
644 consoleblank= [KNL] The console blank (screen saver) timeout in
645 seconds. Defaults to 10*60 = 10mins. A value of 0
646 disables the blank timer.
649 [KNL] Change the default value for
650 /proc/<pid>/coredump_filter.
651 See also Documentation/filesystems/proc.txt.
653 cpuidle.off=1 [CPU_IDLE]
654 disable the cpuidle sub-system
656 cpufreq.off=1 [CPU_FREQ]
657 disable the cpufreq sub-system
660 [X86] Delay for N microsec between assert and de-assert
661 of APIC INIT to start processors. This delay occurs
662 on every CPU online, such as boot, and resume from suspend.
665 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
667 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
669 crashkernel=size[KMG][@offset[KMG]]
670 [KNL] Using kexec, Linux can switch to a 'crash kernel'
671 upon panic. This parameter reserves the physical
672 memory region [offset, offset + size] for that kernel
673 image. If '@offset' is omitted, then a suitable offset
674 is selected automatically. Check
675 Documentation/kdump/kdump.txt for further details.
677 crashkernel=range1:size1[,range2:size2,...][@offset]
678 [KNL] Same as above, but depends on the memory
679 in the running system. The syntax of range is
680 start-[end] where start and end are both
681 a memory unit (amount[KMG]). See also
682 Documentation/kdump/kdump.txt for an example.
684 crashkernel=size[KMG],high
685 [KNL, x86_64] range could be above 4G. Allow kernel
686 to allocate physical memory region from top, so could
687 be above 4G if system have more than 4G ram installed.
688 Otherwise memory region will be allocated below 4G, if
690 It will be ignored if crashkernel=X is specified.
691 crashkernel=size[KMG],low
692 [KNL, x86_64] range under 4G. When crashkernel=X,high
693 is passed, kernel could allocate physical memory region
694 above 4G, that cause second kernel crash on system
695 that require some amount of low memory, e.g. swiotlb
696 requires at least 64M+32K low memory, also enough extra
697 low memory is needed to make sure DMA buffers for 32-bit
698 devices won't run out. Kernel would try to allocate at
699 at least 256M below 4G automatically.
700 This one let user to specify own low range under 4G
701 for second kernel instead.
702 0: to disable low allocation.
703 It will be ignored when crashkernel=X,high is not used
704 or memory reserved is below 4G.
707 [KNL] Disable crypto self-tests
712 cs89x0_media= [HW,NET]
713 Format: { rj45 | aui | bnc }
716 See header of drivers/s390/block/dasd_devmap.c.
718 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
719 (one device per port)
720 Format: <port#>,<type>
721 See also Documentation/input/joystick-parport.txt
723 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
724 time. See Documentation/dynamic-debug-howto.txt for
725 details. Deprecated, see dyndbg.
727 debug [KNL] Enable kernel debugging (events log level).
730 [KNL] verbose self-tests
732 Print debugging info while doing the locking API
734 We default to 0 (no extra messages), setting it to
735 1 will print _a lot_ more information - normally
736 only useful to kernel developers.
738 debug_objects [KNL] Enable object debugging
741 [KNL] Disable object debugging
743 debug_guardpage_minorder=
744 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
745 parameter allows control of the order of pages that will
746 be intentionally kept free (and hence protected) by the
747 buddy allocator. Bigger value increase the probability
748 of catching random memory corruption, but reduce the
749 amount of memory for normal system use. The maximum
750 possible value is MAX_ORDER/2. Setting this parameter
751 to 1 or 2 should be enough to identify most random
752 memory corruption problems caused by bugs in kernel or
753 driver code when a CPU writes to (or reads from) a
754 random memory location. Note that there exists a class
755 of memory corruptions problems caused by buggy H/W or
756 F/W or by drivers badly programing DMA (basically when
757 memory is written at bus level and the CPU MMU is
758 bypassed) which are not detectable by
759 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
760 tracking down these problems.
763 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
764 parameter enables the feature at boot time. In
765 default, it is disabled. We can avoid allocating huge
766 chunk of memory for debug pagealloc if we don't enable
767 it at boot time and the system will work mostly same
768 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
769 on: enable the feature
771 debugpat [X86] Enable PAT debugging
773 decnet.addr= [HW,NET]
774 Format: <area>[,<node>]
775 See also Documentation/networking/decnet.txt.
778 [same as hugepagesz=] The size of the default
779 HugeTLB page size. This is the size represented by
780 the legacy /proc/ hugepages APIs, used for SHM, and
781 default size when mounting hugetlbfs filesystems.
782 Defaults to the default architecture's huge page size
786 Set number of hash buckets for dentry cache.
788 disable_1tb_segments [PPC]
789 Disables the use of 1TB hash page table segments. This
790 causes the kernel to fall back to 256MB segments which
791 can be useful when debugging issues that require an SLB
795 See Documentation/networking/ipv6.txt.
798 Disable RADIX MMU mode on POWER9
800 disable_cpu_apicid= [X86,APIC,SMP]
802 The number of initial APIC ID for the
803 corresponding CPU to be disabled at boot,
804 mostly used for the kdump 2nd kernel to
805 disable BSP to wake up multiple CPUs without
806 causing system reset or hang due to sending
809 disable_ddw [PPC/PSERIES]
810 Disable Dynamic DMA Window support. Use this if
811 to workaround buggy firmware.
814 See Documentation/networking/ipv6.txt.
816 disable_mtrr_cleanup [X86]
817 The kernel tries to adjust MTRR layout from continuous
818 to discrete, to make X server driver able to add WB
819 entry later. This parameter disables that.
821 disable_mtrr_trim [X86, Intel and AMD only]
822 By default the kernel will trim any uncacheable
823 memory out of your available memory pool based on
824 MTRR settings. This parameter disables that behavior,
825 possibly causing your machine to run very slowly.
827 disable_timer_pin_1 [X86]
828 Disable PIN 1 of APIC timer
829 Can be useful to work around chipset bugs.
831 dis_ucode_ldr [X86] Disable the microcode loader.
833 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
834 this option disables the debugging code at boot.
836 dma_debug_entries=<number>
837 This option allows to tune the number of preallocated
838 entries for DMA-API debugging code. One entry is
839 required per DMA-API allocation. Use this if the
840 DMA-API debugging code disables itself because the
841 architectural default is too low.
843 dma_debug_driver=<driver_name>
844 With this option the DMA-API debugging driver
845 filter feature can be enabled at boot time. Just
846 pass the driver to filter for as the parameter.
847 The filter can be disabled or changed to another
848 driver later using sysfs.
850 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
851 Broken monitors, graphic adapters, KVMs and EDIDless
852 panels may send no or incorrect EDID data sets.
853 This parameter allows to specify an EDID data sets
854 in the /lib/firmware directory that are used instead.
855 Generic built-in EDID data sets are used, if one of
856 edid/1024x768.bin, edid/1280x1024.bin,
857 edid/1680x1050.bin, or edid/1920x1080.bin is given
858 and no file with the same name exists. Details and
859 instructions how to build your own EDID data are
860 available in Documentation/EDID/HOWTO.txt. An EDID
861 data set will only be used for a particular connector,
862 if its name and a colon are prepended to the EDID
863 name. Each connector may use a unique EDID data
864 set by separating the files with a comma. An EDID
865 data set with no connector name will be used for
866 any connectors not explicitly specified.
870 dump_apple_properties [X86]
871 Dump name and content of EFI device properties on
872 x86 Macs. Useful for driver authors to determine
873 what data is available or for reverse-engineering.
875 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
876 module.dyndbg[="val"]
877 Enable debug messages at boot time. See
878 Documentation/dynamic-debug-howto.txt for details.
880 nompx [X86] Disables Intel Memory Protection Extensions.
881 See Documentation/x86/intel_mpx.txt for more
882 information about the feature.
884 nopku [X86] Disable Memory Protection Keys CPU feature found
887 module.async_probe [KNL]
888 Enable asynchronous probe on this module.
890 early_ioremap_debug [KNL]
891 Enable debug messages in early_ioremap support. This
892 is useful for tracking down temporary early mappings
893 which are not unmapped.
895 earlycon= [KNL] Output early console device and options.
897 When used with no options, the early console is
898 determined by the stdout-path property in device
901 cdns,<addr>[,options]
902 Start an early, polled-mode console on a Cadence
903 (xuartps) serial port at the specified address. Only
904 supported option is baud rate. If baud rate is not
905 specified, the serial port must already be setup and
908 uart[8250],io,<addr>[,options]
909 uart[8250],mmio,<addr>[,options]
910 uart[8250],mmio32,<addr>[,options]
911 uart[8250],mmio32be,<addr>[,options]
912 uart[8250],0x<addr>[,options]
913 Start an early, polled-mode console on the 8250/16550
914 UART at the specified I/O port or MMIO address.
915 MMIO inter-register address stride is either 8-bit
916 (mmio) or 32-bit (mmio32 or mmio32be).
917 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
918 to be equivalent to 'mmio'. 'options' are specified
919 in the same format described for "console=ttyS<n>"; if
920 unspecified, the h/w is not initialized.
924 Start an early, polled-mode console on a pl011 serial
925 port at the specified address. The pl011 serial port
926 must already be setup and configured. Options are not
927 yet supported. If 'mmio32' is specified, then only
928 the driver will use only 32-bit accessors to read/write
929 the device registers.
932 Start an early, polled-mode console on a meson serial
933 port at the specified address. The serial port must
934 already be setup and configured. Options are not yet
938 Start an early, polled-mode console on an msm serial
939 port at the specified address. The serial port
940 must already be setup and configured. Options are not
944 Start an early, polled-mode console on an msm serial
945 dm port at the specified address. The serial port
946 must already be setup and configured. Options are not
949 smh Use ARM semihosting calls for early console.
957 Use early console provided by serial driver available
958 on Samsung SoCs, requires selecting proper type and
959 a correct base address of the selected UART port. The
960 serial port must already be setup and configured.
961 Options are not yet supported.
964 Start an early, polled-mode console on a lantiq serial
965 (lqasc) port at the specified address. The serial port
966 must already be setup and configured. Options are not
971 Use early console provided by Freescale LP UART driver
972 found on Freescale Vybrid and QorIQ LS1021A processors.
973 A valid base address must be provided, and the serial
974 port must already be setup and configured.
976 armada3700_uart,<addr>
977 Start an early, polled-mode console on the
978 Armada 3700 serial port at the specified
979 address. The serial port must already be setup
980 and configured. Options are not yet supported.
982 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k,S390]
987 earlyprintk=serial[,ttySn[,baudrate]]
988 earlyprintk=serial[,0x...[,baudrate]]
989 earlyprintk=ttySn[,baudrate]
990 earlyprintk=dbgp[debugController#]
991 earlyprintk=pciserial,bus:device.function[,baudrate]
993 earlyprintk is useful when the kernel crashes before
994 the normal console is initialized. It is not enabled by
995 default because it has some cosmetic problems.
997 Append ",keep" to not disable it when the real console
1000 Only one of vga, efi, serial, or usb debug port can
1003 Currently only ttyS0 and ttyS1 may be specified by
1004 name. Other I/O ports may be explicitly specified
1005 on some architectures (x86 and arm at least) by
1006 replacing ttySn with an I/O port address, like this:
1007 earlyprintk=serial,0x1008,115200
1008 You can find the port for a given device in
1009 /proc/tty/driver/serial:
1010 2: uart:ST16650V2 port:00001008 irq:18 ...
1012 Interaction with the standard serial driver is not
1015 The VGA and EFI output is eventually overwritten by
1018 The xen output can only be used by Xen PV guests.
1020 The sclp output can only be used on s390.
1022 edac_report= [HW,EDAC] Control how to report EDAC event
1023 Format: {"on" | "off" | "force"}
1024 on: enable EDAC to report H/W event. May be overridden
1025 by other higher priority error reporting module.
1026 off: disable H/W event reporting through EDAC.
1027 force: enforce the use of EDAC to report H/W event.
1030 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1033 This is designed to be used in conjunction with
1034 the boot argument: earlyprintk=vga
1037 Format: {"off" | "on" | "skip[mbr]"}
1040 Format: { "old_map", "nochunk", "noruntime", "debug" }
1041 old_map [X86-64]: switch to the old ioremap-based EFI
1042 runtime services mapping. 32-bit still uses this one by
1044 nochunk: disable reading files in "chunks" in the EFI
1045 boot stub, as chunking can cause problems with some
1046 firmware implementations.
1047 noruntime : disable EFI runtime services support
1048 debug: enable misc debug output
1050 efi_no_storage_paranoia [EFI; X86]
1051 Using this parameter you can use more than 50% of
1052 your efi variable storage. Use this parameter only if
1053 you are really sure that your UEFI does sane gc and
1054 fulfills the spec otherwise your board may brick.
1056 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1057 Add arbitrary attribute to specific memory range by
1058 updating original EFI memory map.
1059 Region of memory which aa attribute is added to is
1061 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1062 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1063 attribute is added to range 0x100000000-0x180000000 and
1064 0x10a0000000-0x1120000000.
1066 Using this parameter you can do debugging of EFI memmap
1067 related feature. For example, you can do debugging of
1068 Address Range Mirroring feature even if your box
1071 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1072 that is to be dynamically loaded by Linux. If there are
1073 multiple variables with the same name but with different
1074 vendor GUIDs, all of them will be loaded. See
1075 Documentation/acpi/ssdt-overlays.txt for details.
1078 eisa_irq_edge= [PARISC,HW]
1079 See header of drivers/parisc/eisa.c.
1082 See comment before function elanfreq_setup() in
1083 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1086 Format: {"cfq" | "deadline" | "noop"}
1087 See Documentation/block/cfq-iosched.txt and
1088 Documentation/block/deadline-iosched.txt for details.
1090 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1091 Specifies physical address of start of kernel core
1092 image elf header and optionally the size. Generally
1093 kexec loader will pass this option to capture kernel.
1094 See Documentation/kdump/kdump.txt for details.
1096 enable_mtrr_cleanup [X86]
1097 The kernel tries to adjust MTRR layout from continuous
1098 to discrete, to make X server driver able to add WB
1099 entry later. This parameter enables that.
1101 enable_timer_pin_1 [X86]
1102 Enable PIN 1 of APIC timer
1103 Can be useful to work around chipset bugs
1104 (in particular on some ATI chipsets).
1105 The kernel tries to set a reasonable default.
1107 enforcing [SELINUX] Set initial enforcing status.
1109 See security/selinux/Kconfig help text.
1110 0 -- permissive (log only, no denials).
1111 1 -- enforcing (deny and log).
1113 Value can be changed at runtime via /selinux/enforce.
1116 Disable Error Record Serialization Table (ERST)
1119 ether= [HW,NET] Ethernet cards parameters
1120 This option is obsoleted by the "netdev=" option, which
1121 has equivalent usage. See its documentation for details.
1125 Permit 'security.evm' to be updated regardless of
1126 current integrity status.
1130 fail_make_request=[KNL]
1131 General fault injection mechanism.
1132 Format: <interval>,<probability>,<space>,<times>
1133 See also Documentation/fault-injection/.
1136 See Documentation/blockdev/floppy.txt.
1138 force_pal_cache_flush
1139 [IA-64] Avoid check_sal_cache_flush which may hang on
1140 buggy SAL_CACHE_FLUSH implementations. Using this
1141 parameter will force ia64_sal_cache_flush to call
1142 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1145 Forcefully enable Physical Address Extension (PAE).
1146 Many Pentium M systems disable PAE but may have a
1147 functionally usable PAE implementation.
1148 Warning: use of this parameter will taint the kernel
1149 and may cause unknown problems.
1152 [FTRACE] will set and start the specified tracer
1153 as early as possible in order to facilitate early
1156 ftrace_dump_on_oops[=orig_cpu]
1157 [FTRACE] will dump the trace buffers on oops.
1158 If no parameter is passed, ftrace will dump
1159 buffers of all CPUs, but if you pass orig_cpu, it will
1160 dump only the buffer of the CPU that triggered the
1163 ftrace_filter=[function-list]
1164 [FTRACE] Limit the functions traced by the function
1165 tracer at boot up. function-list is a comma separated
1166 list of functions. This list can be changed at run
1167 time by the set_ftrace_filter file in the debugfs
1170 ftrace_notrace=[function-list]
1171 [FTRACE] Do not trace the functions specified in
1172 function-list. This list can be changed at run time
1173 by the set_ftrace_notrace file in the debugfs
1176 ftrace_graph_filter=[function-list]
1177 [FTRACE] Limit the top level callers functions traced
1178 by the function graph tracer at boot up.
1179 function-list is a comma separated list of functions
1180 that can be changed at run time by the
1181 set_graph_function file in the debugfs tracing directory.
1183 ftrace_graph_notrace=[function-list]
1184 [FTRACE] Do not trace from the functions specified in
1185 function-list. This list is a comma separated list of
1186 functions that can be changed at run time by the
1187 set_graph_notrace file in the debugfs tracing directory.
1190 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1191 support via parallel port (up to 5 devices per port)
1192 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1193 See also Documentation/input/joystick-parport.txt
1197 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1201 gcov_persist= [GCOV] When non-zero (default), profiling data for
1202 kernel modules is saved and remains accessible via
1203 debugfs, even when the module is unloaded/reloaded.
1204 When zero, profiling data is discarded and associated
1205 debugfs files are removed at module unload time.
1207 goldfish [X86] Enable the goldfish android emulator platform.
1208 Don't use this when you are not running on the
1211 gpt [EFI] Forces disk with valid GPT signature but
1212 invalid Protective MBR to be treated as GPT. If the
1213 primary GPT is corrupted, it enables the backup/alternate
1214 GPT to be used instead.
1216 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1217 the "Enable 0" bit of the configuration register.
1220 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1221 the "Enable 0" bit of the configuration register.
1224 grcan.select= [HW] Select which physical interface to use.
1227 grcan.txsize= [HW] Sets the size of the tx buffer.
1228 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1230 grcan.rxsize= [HW] Sets the size of the rx buffer.
1231 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1234 gpio-mockup.gpio_mockup_ranges
1235 [HW] Sets the ranges of gpiochip of for this device.
1236 Format: <start1>,<end1>,<start2>,<end2>...
1238 hardlockup_all_cpu_backtrace=
1239 [KNL] Should the hard-lockup detector generate
1240 backtraces on all cpus.
1243 hashdist= [KNL,NUMA] Large hashes allocated during boot
1244 are distributed across NUMA nodes. Defaults on
1245 for 64-bit NUMA, off otherwise.
1246 Format: 0 | 1 (for off | on)
1248 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1250 hd= [EIDE] (E)IDE hard drive subsystem geometry
1251 Format: <cyl>,<head>,<sect>
1254 Disable Hardware Error Source Table (HEST) support;
1255 corresponding firmware-first mode error processing
1256 logic will be disabled.
1258 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1259 size of <nn>. This works even on boxes that have no
1260 highmem otherwise. This also works to reduce highmem
1261 size on bigger boxes.
1263 highres= [KNL] Enable/disable high resolution timer mode.
1264 Valid parameters: "on", "off"
1268 See Documentation/isdn/README.HiSax.
1272 hpet= [X86-32,HPET] option to control HPET usage
1273 Format: { enable (default) | disable | force |
1275 disable: disable HPET and use PIT instead
1276 force: allow force enabled of undocumented chips (ICH4,
1278 verbose: show contents of HPET registers during setup
1280 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1281 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1283 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1284 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1285 On x86-64 and powerpc, this option can be specified
1286 multiple times interleaved with hugepages= to reserve
1287 huge pages of different sizes. Valid pages sizes on
1288 x86-64 are 2M (when the CPU supports "pse") and 1G
1289 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1291 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1292 terminal devices. Valid values: 0..8
1293 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1294 If specified, z/VM IUCV HVC accepts connections
1295 from listed z/VM user IDs only.
1297 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1298 hardware thread id mappings.
1299 Format: <cpu>:<hwthread>
1302 Do not unregister boot console at start. This is only
1303 useful for debugging when something happens in the window
1304 between unregistering the boot console and initializing
1307 i2c_bus= [HW] Override the default board specific I2C bus speed
1308 or register an additional I2C bus that is not
1309 registered from board initialization code.
1313 i8042.debug [HW] Toggle i8042 debug mode
1314 i8042.unmask_kbd_data
1315 [HW] Enable printing of interrupt data from the KBD port
1316 (disabled by default, and as a pre-condition
1317 requires that i8042.debug=1 be enabled)
1318 i8042.direct [HW] Put keyboard port into non-translated mode
1319 i8042.dumbkbd [HW] Pretend that controller can only read data from
1320 keyboard and cannot control its state
1321 (Don't attempt to blink the leds)
1322 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1323 i8042.nokbd [HW] Don't check/create keyboard port
1324 i8042.noloop [HW] Disable the AUX Loopback command while probing
1326 i8042.nomux [HW] Don't check presence of an active multiplexing
1328 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1330 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1331 i8042.reset [HW] Reset the controller during init, cleanup and
1332 suspend-to-ram transitions, only during s2r
1333 transitions, or never reset
1334 Format: { 1 | Y | y | 0 | N | n }
1335 1, Y, y: always reset controller
1336 0, N, n: don't ever reset controller
1337 Default: only on s2r transitions on x86; most other
1338 architectures force reset to be always executed
1339 i8042.unlock [HW] Unlock (ignore) the keylock
1340 i8042.kbdreset [HW] Reset device connected to KBD port
1344 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1345 indicates that the driver is running on unsupported
1347 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1348 does not match list of supported models.
1350 [HW] Report power status in /proc/i8k
1351 (disabled by default)
1352 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1355 i915.invert_brightness=
1356 [DRM] Invert the sense of the variable that is used to
1357 set the brightness of the panel backlight. Normally a
1358 brightness value of 0 indicates backlight switched off,
1359 and the maximum of the brightness value sets the backlight
1360 to maximum brightness. If this parameter is set to 0
1361 (default) and the machine requires it, or this parameter
1362 is set to 1, a brightness value of 0 sets the backlight
1363 to maximum brightness, and the maximum of the brightness
1364 value switches the backlight off.
1365 -1 -- never invert brightness
1366 0 -- machine default
1367 1 -- force brightness inversion
1370 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1372 ide-core.nodma= [HW] (E)IDE subsystem
1373 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1374 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1375 .cdrom .chs .ignore_cable are additional options
1376 See Documentation/ide/ide.txt.
1378 ide-generic.probe-mask= [HW] (E)IDE subsystem
1380 Probe mask for legacy ISA IDE ports. Depending on
1381 platform up to 6 ports are supported, enabled by
1382 setting corresponding bits in the mask to 1. The
1383 default value is 0x0, which has a special meaning.
1384 On systems that have PCI, it triggers scanning the
1385 PCI bus for the first and the second port, which
1386 are then probed. On systems without PCI the value
1387 of 0x0 enables probing the two first ports as if it
1390 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1391 Claim all unknown PCI IDE storage controllers.
1394 Format: idle=poll, idle=halt, idle=nomwait
1395 Poll forces a polling idle loop that can slightly
1396 improve the performance of waking up a idle CPU, but
1397 will use a lot of power and make the system run hot.
1399 idle=halt: Halt is forced to be used for CPU idle.
1400 In such case C2/C3 won't be used again.
1401 idle=nomwait: Disable mwait for CPU C-states
1403 ieee754= [MIPS] Select IEEE Std 754 conformance mode
1404 Format: { strict | legacy | 2008 | relaxed }
1407 Choose which programs will be accepted for execution
1408 based on the IEEE 754 NaN encoding(s) supported by
1409 the FPU and the NaN encoding requested with the value
1410 of an ELF file header flag individually set by each
1411 binary. Hardware implementations are permitted to
1412 support either or both of the legacy and the 2008 NaN
1415 Available settings are as follows:
1416 strict accept binaries that request a NaN encoding
1417 supported by the FPU
1418 legacy only accept legacy-NaN binaries, if supported
1420 2008 only accept 2008-NaN binaries, if supported
1422 relaxed accept any binaries regardless of whether
1423 supported by the FPU
1425 The FPU emulator is always able to support both NaN
1426 encodings, so if no FPU hardware is present or it has
1427 been disabled with 'nofpu', then the settings of
1428 'legacy' and '2008' strap the emulator accordingly,
1429 'relaxed' straps the emulator for both legacy-NaN and
1430 2008-NaN, whereas 'strict' enables legacy-NaN only on
1431 legacy processors and both NaN encodings on MIPS32 or
1434 The setting for ABS.fmt/NEG.fmt instruction execution
1435 mode generally follows that for the NaN encoding,
1436 except where unsupported by hardware.
1438 ignore_loglevel [KNL]
1439 Ignore loglevel setting - this will print /all/
1440 kernel messages to the console. Useful for debugging.
1441 We also add it as printk module parameter, so users
1442 could change it dynamically, usually by
1443 /sys/module/printk/parameters/ignore_loglevel.
1446 Ignore RLIMIT_DATA setting for data mappings,
1447 print warning at first misuse. Can be changed via
1448 /sys/module/kernel/parameters/ignore_rlimit_data.
1450 ihash_entries= [KNL]
1451 Set number of hash buckets for inode cache.
1453 ima_appraise= [IMA] appraise integrity measurements
1454 Format: { "off" | "enforce" | "fix" | "log" }
1457 ima_appraise_tcb [IMA]
1458 The builtin appraise policy appraises all files
1461 ima_canonical_fmt [IMA]
1462 Use the canonical format for the binary runtime
1463 measurements, instead of host native format.
1466 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1470 The list of supported hash algorithms is defined
1471 in crypto/hash_info.h.
1474 The builtin measurement policy to load during IMA
1475 setup. Specyfing "tcb" as the value, measures all
1476 programs exec'd, files mmap'd for exec, and all files
1477 opened with the read mode bit set by either the
1478 effective uid (euid=0) or uid=0.
1481 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1482 Load a policy which meets the needs of the Trusted
1483 Computing Base. This means IMA will measure all
1484 programs exec'd, files mmap'd for exec, and all files
1485 opened for read by uid=0.
1488 Select one of defined IMA measurements template formats.
1489 Formats: { "ima" | "ima-ng" | "ima-sig" }
1493 [IMA] Define a custom template format.
1494 Format: { "field1|...|fieldN" }
1496 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1497 Format: <min_file_size>
1498 Set the minimal file size for using asynchronous hash.
1499 If left unspecified, ahash usage is disabled.
1501 ahash performance varies for different data sizes on
1502 different crypto accelerators. This option can be used
1503 to achieve the best performance for a particular HW.
1505 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1507 Set hashing buffer size. Default: 4k.
1509 ahash performance varies for different chunk sizes on
1510 different crypto accelerators. This option can be used
1511 to achieve best performance for particular HW.
1515 Run specified binary instead of /sbin/init as init
1518 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1519 for working out where the kernel is dying during
1522 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1523 initcall functions. Useful for debugging built-in
1524 modules and initcalls.
1526 initrd= [BOOT] Specify the location of the initial ramdisk
1528 init_pkru= [x86] Specify the default memory protection keys rights
1529 register contents for all processes. 0x55555554 by
1530 default (disallow access to all but pkey 0). Can
1531 override in debugfs after boot.
1533 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1536 int_pln_enable [x86] Enable power limit notification interrupt
1538 integrity_audit=[IMA]
1539 Format: { "0" | "1" }
1540 0 -- basic integrity auditing messages. (Default)
1541 1 -- additional integrity auditing messages.
1543 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1545 Enable intel iommu driver.
1547 Disable intel iommu driver.
1548 igfx_off [Default Off]
1549 By default, gfx is mapped as normal device. If a gfx
1550 device has a dedicated DMAR unit, the DMAR unit is
1551 bypassed by not enabling DMAR with this option. In
1552 this case, gfx device will use physical address for
1555 With this option iommu will not optimize to look
1556 for io virtual address below 32-bit forcing dual
1557 address cycle on pci bus for cards supporting greater
1558 than 32-bit addressing. The default is to look
1559 for translation below 32-bit and if not available
1560 then look in the higher range.
1561 strict [Default Off]
1562 With this option on every unmap_single operation will
1563 result in a hardware IOTLB flush operation as opposed
1564 to batching them for performance.
1565 sp_off [Default Off]
1566 By default, super page will be supported if Intel IOMMU
1567 has the capability. With this option, super page will
1569 ecs_off [Default Off]
1570 By default, extended context tables will be supported if
1571 the hardware advertises that it has support both for the
1572 extended tables themselves, and also PASID support. With
1573 this option set, extended tables will not be used even
1574 on hardware which claims to support them.
1576 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1577 0 disables intel_idle and fall back on acpi_idle.
1578 1 to 9 specify maximum depth of C-state.
1582 Do not enable intel_pstate as the default
1583 scaling driver for the supported processors
1585 Use intel_pstate as a scaling driver, but configure it
1586 to work with generic cpufreq governors (instead of
1587 enabling its internal governor). This mode cannot be
1588 used along with the hardware-managed P-states (HWP)
1591 Enable intel_pstate on systems that prohibit it by default
1592 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1593 instead of acpi-cpufreq may disable platform features, such
1594 as thermal controls and power capping, that rely on ACPI
1595 P-States information being indicated to OSPM and therefore
1596 should be used with caution. This option does not work with
1597 processors that aren't supported by the intel_pstate driver
1598 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1600 Do not enable hardware P state control (HWP)
1603 Only load intel_pstate on systems which support
1604 hardware P state control (HWP) if available.
1606 Enforce ACPI _PPC performance limits. If the Fixed ACPI
1607 Description Table, specifies preferred power management
1608 profile as "Enterprise Server" or "Performance Server",
1609 then this feature is turned on by default.
1611 Allow per-logical-CPU P-State performance control limits using
1612 cpufreq sysfs interface
1614 intremap= [X86-64, Intel-IOMMU]
1615 on enable Interrupt Remapping (default)
1616 off disable Interrupt Remapping
1617 nosid disable Source ID checking
1619 BIOS x2APIC opt-out request will be ignored
1620 nopost disable Interrupt Posting
1622 iomem= Disable strict checking of access to MMIO memory
1623 strict regions from userspace.
1638 nobypass [PPC/POWERNV]
1639 Disable IOMMU bypass, using IOMMU for PCI devices.
1642 io7= [HW] IO7 for Marvel based alpha systems
1643 See comment before marvel_specify_io7 in
1644 arch/alpha/kernel/core_marvel.c.
1646 io_delay= [X86] I/O delay method
1648 Standard port 0x80 based delay
1650 Alternate port 0xed based delay (needed on some systems)
1652 Simple two microseconds delay
1657 See Documentation/filesystems/nfs/nfsroot.txt.
1659 irqaffinity= [SMP] Set the default irq affinity mask
1660 The argument is a cpu list, as described above.
1663 When an interrupt is not handled search all handlers
1664 for it. Intended to get systems with badly broken
1668 When an interrupt is not handled search all handlers
1669 for it. Also check all handlers each timer
1670 interrupt. Intended to get systems with badly broken
1674 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1676 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1677 The argument is a cpu list, as described above.
1679 This option can be used to specify one or more CPUs
1680 to isolate from the general SMP balancing and scheduling
1681 algorithms. You can move a process onto or off an
1682 "isolated" CPU via the CPU affinity syscalls or cpuset.
1683 <cpu number> begins at 0 and the maximum value is
1684 "number of CPUs in system - 1".
1686 This option is the preferred way to isolate CPUs. The
1687 alternative -- manually setting the CPU mask of all
1688 tasks in the system -- can cause problems and
1689 suboptimal load balancer performance.
1693 ivrs_ioapic [HW,X86_64]
1694 Provide an override to the IOAPIC-ID<->DEVICE-ID
1695 mapping provided in the IVRS ACPI table. For
1696 example, to map IOAPIC-ID decimal 10 to
1697 PCI device 00:14.0 write the parameter as:
1698 ivrs_ioapic[10]=00:14.0
1700 ivrs_hpet [HW,X86_64]
1701 Provide an override to the HPET-ID<->DEVICE-ID
1702 mapping provided in the IVRS ACPI table. For
1703 example, to map HPET-ID decimal 0 to
1704 PCI device 00:14.0 write the parameter as:
1705 ivrs_hpet[0]=00:14.0
1707 ivrs_acpihid [HW,X86_64]
1708 Provide an override to the ACPI-HID:UID<->DEVICE-ID
1709 mapping provided in the IVRS ACPI table. For
1710 example, to map UART-HID:UID AMD0020:0 to
1711 PCI device 00:14.5 write the parameter as:
1712 ivrs_acpihid[00:14.5]=AMD0020:0
1714 js= [HW,JOY] Analog joystick
1715 See Documentation/input/joystick.txt.
1718 When CONFIG_RANDOMIZE_BASE is set, this disables
1719 kernel and module base offset ASLR (Address Space
1720 Layout Randomization).
1724 kernelcore= [KNL,X86,IA-64,PPC]
1725 Format: nn[KMGTPE] | "mirror"
1727 specifies the amount of memory usable by the kernel
1728 for non-movable allocations. The requested amount is
1729 spread evenly throughout all nodes in the system. The
1730 remaining memory in each node is used for Movable
1731 pages. In the event, a node is too small to have both
1732 kernelcore and Movable pages, kernelcore pages will
1733 take priority and other nodes will have a larger number
1734 of Movable pages. The Movable zone is used for the
1735 allocation of pages that may be reclaimed or moved
1736 by the page migration subsystem. This means that
1737 HugeTLB pages may not be allocated from this zone.
1738 Note that allocations like PTEs-from-HighMem still
1739 use the HighMem zone if it exists, and the Normal
1740 zone if it does not.
1742 Instead of specifying the amount of memory (nn[KMGTPE]),
1743 you can specify "mirror" option. In case "mirror"
1744 option is specified, mirrored (reliable) memory is used
1745 for non-movable allocations and remaining memory is used
1746 for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
1747 so you can NOT specify nn[KMGTPE] and "mirror" at the same
1750 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1751 Format: <Controller#>[,poll interval]
1752 The controller # is the number of the ehci usb debug
1753 port as it is probed via PCI. The poll interval is
1754 optional and is the number seconds in between
1755 each poll cycle to the debug port in case you need
1756 the functionality for interrupting the kernel with
1757 gdb or control-c on the dbgp connection. When
1758 not using this parameter you use sysrq-g to break into
1759 the kernel debugger.
1761 kgdboc= [KGDB,HW] kgdb over consoles.
1762 Requires a tty driver that supports console polling,
1763 or a supported polling keyboard driver (non-usb).
1764 Serial only format: <serial_device>[,baud]
1765 keyboard only format: kbd
1766 keyboard and serial format: kbd,<serial_device>[,baud]
1767 Optional Kernel mode setting:
1768 kms, kbd format: kms,kbd
1769 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1771 kgdbwait [KGDB] Stop kernel execution and enter the
1772 kernel debugger at the earliest opportunity.
1774 kmac= [MIPS] korina ethernet MAC address.
1775 Configure the RouterBoard 532 series on-chip
1776 Ethernet adapter MAC address.
1778 kmemleak= [KNL] Boot-time kmemleak enable/disable
1779 Valid arguments: on, off
1781 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1784 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1785 Valid arguments: 0, 1, 2
1786 kmemcheck=0 (disabled)
1787 kmemcheck=1 (enabled)
1788 kmemcheck=2 (one-shot mode)
1789 Default: 2 (one-shot mode)
1791 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1792 Default is 0 (don't ignore, but inject #GP)
1794 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1798 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1799 Default is 1 (enabled)
1801 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1803 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1805 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1806 (virtualized MMU) support on capable Intel chips.
1807 Default is 1 (enabled)
1809 kvm-intel.emulate_invalid_guest_state=
1810 [KVM,Intel] Enable emulation of invalid guest states
1811 Default is 0 (disabled)
1813 kvm-intel.flexpriority=
1814 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1815 Default is 1 (enabled)
1818 [KVM,Intel] Enable VMX nesting (nVMX).
1819 Default is 0 (disabled)
1821 kvm-intel.unrestricted_guest=
1822 [KVM,Intel] Disable unrestricted guest feature
1823 (virtualized real and unpaged mode) on capable
1824 Intel chips. Default is 1 (enabled)
1826 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1827 feature (tagged TLBs) on capable Intel chips.
1828 Default is 1 (enabled)
1834 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1837 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1838 value for LAPIC timer one-shot implementation. Default
1839 back to the programmable timer unit in the LAPIC.
1841 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1844 libata.dma= [LIBATA] DMA control
1845 libata.dma=0 Disable all PATA and SATA DMA
1846 libata.dma=1 PATA and SATA Disk DMA only
1847 libata.dma=2 ATAPI (CDROM) DMA only
1848 libata.dma=4 Compact Flash DMA only
1849 Combinations also work, so libata.dma=3 enables DMA
1850 for disks and CDROMs, but not CFs.
1852 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1853 libata.ignore_hpa=0 keep BIOS limits (default)
1854 libata.ignore_hpa=1 ignore limits, using full disk
1856 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1860 libata.force= [LIBATA] Force configurations. The format is comma
1861 separated list of "[ID:]VAL" where ID is
1862 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1863 matching port, link or device. Basically, it matches
1864 the ATA ID string printed on console by libata. If
1865 the whole ID part is omitted, the last PORT and DEVICE
1866 values are used. If ID hasn't been specified yet, the
1867 configuration applies to all ports, links and devices.
1869 If only DEVICE is omitted, the parameter applies to
1870 the port and all links and devices behind it. DEVICE
1871 number of 0 either selects the first device or the
1872 first fan-out link behind PMP device. It does not
1873 select the host link. DEVICE number of 15 selects the
1874 host link and device attached to it.
1876 The VAL specifies the configuration to force. As long
1877 as there's no ambiguity shortcut notation is allowed.
1878 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1879 The following configurations can be forced.
1881 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1882 Any ID with matching PORT is used.
1884 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1886 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1887 udma[/][16,25,33,44,66,100,133] notation is also
1890 * [no]ncq: Turn on or off NCQ.
1892 * [no]ncqtrim: Turn off queued DSM TRIM.
1894 * nohrst, nosrst, norst: suppress hard, soft
1897 * rstonce: only attempt one reset during
1898 hot-unplug link recovery
1900 * dump_id: dump IDENTIFY data.
1902 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1904 * disable: Disable this device.
1906 If there are multiple matching configurations changing
1907 the same attribute, the last one is used.
1909 memblock=debug [KNL] Enable memblock debug messages.
1911 load_ramdisk= [RAM] List of ramdisks to load from floppy
1912 See Documentation/blockdev/ramdisk.txt.
1914 lockd.nlm_grace_period=P [NFS] Assign grace period.
1917 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1920 lockd.nlm_timeout=T [NFS] Assign timeout value.
1923 lockd.nlm_udpport=M [NFS] Assign UDP port.
1926 locktorture.nreaders_stress= [KNL]
1927 Set the number of locking read-acquisition kthreads.
1928 Defaults to being automatically set based on the
1929 number of online CPUs.
1931 locktorture.nwriters_stress= [KNL]
1932 Set the number of locking write-acquisition kthreads.
1934 locktorture.onoff_holdoff= [KNL]
1935 Set time (s) after boot for CPU-hotplug testing.
1937 locktorture.onoff_interval= [KNL]
1938 Set time (s) between CPU-hotplug operations, or
1939 zero to disable CPU-hotplug testing.
1941 locktorture.shuffle_interval= [KNL]
1942 Set task-shuffle interval (jiffies). Shuffling
1943 tasks allows some CPUs to go into dyntick-idle
1944 mode during the locktorture test.
1946 locktorture.shutdown_secs= [KNL]
1947 Set time (s) after boot system shutdown. This
1948 is useful for hands-off automated testing.
1950 locktorture.stat_interval= [KNL]
1951 Time (s) between statistics printk()s.
1953 locktorture.stutter= [KNL]
1954 Time (s) to stutter testing, for example,
1955 specifying five seconds causes the test to run for
1956 five seconds, wait for five seconds, and so on.
1957 This tests the locking primitive's ability to
1958 transition abruptly to and from idle.
1960 locktorture.torture_runnable= [BOOT]
1961 Start locktorture running at boot time.
1963 locktorture.torture_type= [KNL]
1964 Specify the locking implementation to test.
1966 locktorture.verbose= [KNL]
1967 Enable additional printk() statements.
1969 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1972 loglevel= All Kernel Messages with a loglevel smaller than the
1973 console loglevel will be printed to the console. It can
1974 also be changed with klogd or other programs. The
1975 loglevels are defined as follows:
1977 0 (KERN_EMERG) system is unusable
1978 1 (KERN_ALERT) action must be taken immediately
1979 2 (KERN_CRIT) critical conditions
1980 3 (KERN_ERR) error conditions
1981 4 (KERN_WARNING) warning conditions
1982 5 (KERN_NOTICE) normal but significant condition
1983 6 (KERN_INFO) informational
1984 7 (KERN_DEBUG) debug-level messages
1986 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1987 in bytes. n must be a power of two and greater
1988 than the minimal size. The minimal size is defined
1989 by LOG_BUF_SHIFT kernel config parameter. There is
1990 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1991 that allows to increase the default size depending on
1992 the number of CPUs. See init/Kconfig for more details.
1994 logo.nologo [FB] Disables display of the built-in Linux logo.
1995 This may be used to provide more screen space for
1996 kernel log messages and is useful when debugging
1997 kernel boot problems.
1999 lp=0 [LP] Specify parallel ports to use, e.g,
2000 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
2001 lp=reset first parallel port). 'lp=0' disables the
2002 lp=auto printer driver. 'lp=reset' (which can be
2003 specified in addition to the ports) causes
2004 attached printers to be reset. Using
2005 lp=port1,port2,... specifies the parallel ports
2006 to associate lp devices with, starting with
2007 lp0. A port specification may be 'none' to skip
2008 that lp device, or a parport name such as
2009 'parport0'. Specifying 'lp=auto' instead of a
2010 port specification list means that device IDs
2011 from each port should be examined, to see if
2012 an IEEE 1284-compliant printer is attached; if
2013 so, the driver will manage that printer.
2014 See also header of drivers/char/lp.c.
2017 Sets loops_per_jiffy to given constant, thus avoiding
2018 time-consuming boot-time autodetection (up to 250 ms per
2019 CPU). 0 enables autodetection (default). To determine
2020 the correct value for your kernel, boot with normal
2021 autodetection and see what value is printed. Note that
2022 on SMP systems the preset will be applied to all CPUs,
2023 which is likely to cause problems if your CPUs need
2024 significantly divergent settings. An incorrect value
2025 will cause delays in the kernel to be wrong, leading to
2026 unpredictable I/O errors and other breakage. Although
2027 unlikely, in the extreme case this might damage your
2031 Format: <io>,<irq>,<dma>
2033 machvec= [IA-64] Force the use of a particular machine-vector
2034 (machvec) in a generic kernel.
2035 Example: machvec=hpzx1_swiotlb
2037 machtype= [Loongson] Share the same kernel image file between different
2039 Example: machtype=lemote-yeeloong-2f-7inch
2041 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2042 than or equal to this physical address is ignored.
2044 maxcpus= [SMP] Maximum number of processors that an SMP kernel
2045 will bring up during bootup. maxcpus=n : n >= 0 limits
2046 the kernel to bring up 'n' processors. Surely after
2047 bootup you can bring up the other plugged cpu by executing
2048 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
2049 only takes effect during system bootup.
2050 While n=0 is a special case, it is equivalent to "nosmp",
2051 which also disables the IO APIC.
2053 max_loop= [LOOP] The number of loop block devices that get
2054 (loop.max_loop) unconditionally pre-created at init time. The default
2055 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2056 of statically allocating a predefined number, loop
2057 devices can be requested on-demand with the
2058 /dev/loop-control interface.
2060 mce [X86-32] Machine Check Exception
2062 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2064 md= [HW] RAID subsystems devices and level
2065 See Documentation/admin-guide/md.rst.
2068 Format: <first>,<last>
2069 Specifies range of consoles to be captured by the MDA.
2071 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2072 Amount of memory to be used when the kernel is not able
2073 to see the whole system memory or for test.
2074 [X86] Work as limiting max address. Use together
2075 with memmap= to avoid physical address space collisions.
2076 Without memmap= PCI devices could be placed at addresses
2077 belonging to unused RAM.
2079 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2083 [KNL,SH] Allow user to override the default size for
2084 per-device physically contiguous DMA buffers.
2086 memhp_default_state=online/offline
2087 [KNL] Set the initial state for the memory hotplug
2088 onlining policy. If not specified, the default value is
2089 set according to the
2090 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
2092 See Documentation/memory-hotplug.txt.
2094 memmap=exactmap [KNL,X86] Enable setting of an exact
2095 E820 memory map, as specified by the user.
2096 Such memmap=exactmap lines can be constructed based on
2097 BIOS output or other requirements. See the memmap=nn@ss
2100 memmap=nn[KMG]@ss[KMG]
2101 [KNL] Force usage of a specific region of memory.
2102 Region of memory to be used is from ss to ss+nn.
2104 memmap=nn[KMG]#ss[KMG]
2105 [KNL,ACPI] Mark specific memory as ACPI data.
2106 Region of memory to be marked is from ss to ss+nn.
2108 memmap=nn[KMG]$ss[KMG]
2109 [KNL,ACPI] Mark specific memory as reserved.
2110 Region of memory to be reserved is from ss to ss+nn.
2111 Example: Exclude memory from 0x18690000-0x1869ffff
2112 memmap=64K$0x18690000
2114 memmap=0x10000$0x18690000
2116 memmap=nn[KMG]!ss[KMG]
2117 [KNL,X86] Mark specific memory as protected.
2118 Region of memory to be used, from ss to ss+nn.
2119 The memory region may be marked as e820 type 12 (0xc)
2120 and is NVDIMM or ADR memory.
2122 memory_corruption_check=0/1 [X86]
2123 Some BIOSes seem to corrupt the first 64k of
2124 memory when doing things like suspend/resume.
2125 Setting this option will scan the memory
2126 looking for corruption. Enabling this will
2127 both detect corruption and prevent the kernel
2128 from using the memory being corrupted.
2129 However, its intended as a diagnostic tool; if
2130 repeatable BIOS-originated corruption always
2131 affects the same memory, you can use memmap=
2132 to prevent the kernel from using that memory.
2134 memory_corruption_check_size=size [X86]
2135 By default it checks for corruption in the low
2136 64k, making this memory unavailable for normal
2137 use. Use this parameter to scan for
2138 corruption in more or less memory.
2140 memory_corruption_check_period=seconds [X86]
2141 By default it checks for corruption every 60
2142 seconds. Use this parameter to check at some
2143 other rate. 0 disables periodic checking.
2145 memtest= [KNL,X86,ARM] Enable memtest
2147 default : 0 <disable>
2148 Specifies the number of memtest passes to be
2149 performed. Each pass selects another test
2150 pattern from a given set of patterns. Memtest
2151 fills the memory with this pattern, validates
2152 memory contents and reserves bad memory
2153 regions that are detected.
2155 mem_sleep_default= [SUSPEND] Default system suspend mode:
2156 s2idle - Suspend-To-Idle
2157 shallow - Power-On Suspend or equivalent (if supported)
2158 deep - Suspend-To-RAM or equivalent (if supported)
2159 See Documentation/power/states.txt.
2161 meye.*= [HW] Set MotionEye Camera parameters
2162 See Documentation/video4linux/meye.txt.
2164 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2165 Multi-Function General Purpose Timers on AMD Geode
2168 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2169 the BIOS has incorrectly applied a workaround. TinyBIOS
2170 version 0.98 is known to be affected, 0.99 fixes the
2171 problem by letting the user disable the workaround.
2175 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2176 physical address is ignored.
2178 mini2440= [ARM,HW,KNL]
2179 Format:[0..2][b][c][t]
2181 MINI2440 configuration specification:
2182 0 - The attached screen is the 3.5" TFT
2183 1 - The attached screen is the 7" TFT
2184 2 - The VGA Shield is attached (1024x768)
2185 Leaving out the screen size parameter will not load
2186 the TFT driver, and the framebuffer will be left
2188 b - Enable backlight. The TFT backlight pin will be
2189 linked to the kernel VESA blanking code and a GPIO
2190 LED. This parameter is not necessary when using the
2192 c - Enable the s3c camera interface.
2193 t - Reserved for enabling touchscreen support. The
2194 touchscreen support is not enabled in the mainstream
2195 kernel as of 2.6.30, a preliminary port can be found
2196 in the "bleeding edge" mini2440 support kernel at
2197 http://repo.or.cz/w/linux-2.6/mini2440.git
2200 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2201 parameter allows control of the logging verbosity for
2202 the additional memory initialisation checks. A value
2203 of 0 disables mminit logging and a level of 4 will
2204 log everything. Information is printed at KERN_DEBUG
2205 so loglevel=8 may also need to be specified.
2208 [KNL] When CONFIG_MODULE_SIG is set, this means that
2209 modules without (valid) signatures will fail to load.
2210 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2211 is always true, so this option does nothing.
2213 module_blacklist= [KNL] Do not load a comma-separated list of
2214 modules. Useful for debugging problem modules.
2217 [MOUSE] Maximum time between finger touching and
2218 leaving touchpad surface for touch to be considered
2219 a tap and be reported as a left button click (for
2220 touchpads working in absolute mode only).
2222 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2223 reporting absolute coordinates, such as tablets
2224 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2225 reporting absolute coordinates, such as tablets
2227 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2228 is similar to kernelcore except it specifies the
2229 amount of memory used for migratable allocations.
2230 If both kernelcore and movablecore is specified,
2231 then kernelcore will be at *least* the specified
2232 value but may be more. If movablecore on its own
2233 is specified, the administrator must be careful
2234 that the amount of memory usable for all allocations
2237 movable_node [KNL] Boot-time switch to enable the effects
2238 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2240 MTD_Partition= [MTD]
2241 Format: <name>,<region-number>,<size>,<offset>
2243 MTD_Region= [MTD] Format:
2244 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2247 See drivers/mtd/cmdlinepart.c.
2249 multitce=off [PPC] This parameter disables the use of the pSeries
2250 firmware feature for updating multiple TCE entries
2253 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2255 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2257 boundary - index of last SLC block on Flex-OneNAND.
2258 The remaining blocks are configured as MLC blocks.
2259 lock - Configure if Flex-OneNAND boundary should be locked.
2260 Once locked, the boundary cannot be changed.
2261 1 indicates lock status, 0 indicates unlock status.
2264 ARM/S3C2412 JIVE boot control
2266 See arch/arm/mach-s3c2412/mach-jive.c
2268 mtouchusb.raw_coordinates=
2269 [HW] Make the MicroTouch USB driver use raw coordinates
2270 ('y', default) or cooked coordinates ('n')
2272 mtrr_chunk_size=nn[KMG] [X86]
2273 used for mtrr cleanup. It is largest continuous chunk
2274 that could hold holes aka. UC entries.
2276 mtrr_gran_size=nn[KMG] [X86]
2277 Used for mtrr cleanup. It is granularity of mtrr block.
2279 Large value could prevent small alignment from
2282 mtrr_spare_reg_nr=n [X86]
2284 Range: 0,7 : spare reg number
2286 Used for mtrr cleanup. It is spare mtrr entries number.
2287 Set to 2 or more if your graphical card needs more.
2289 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2291 netdev= [NET] Network devices parameters
2292 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2293 Note that mem_start is often overloaded to mean
2294 something different and driver-specific.
2295 This usage is only documented in each driver source
2299 [NETFILTER] Enable connection tracking flow accounting
2300 0 to disable accounting
2301 1 to enable accounting
2304 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2305 See Documentation/filesystems/nfs/nfsroot.txt.
2307 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2308 See Documentation/filesystems/nfs/nfsroot.txt.
2310 nfsrootdebug [NFS] enable nfsroot debugging messages.
2311 See Documentation/filesystems/nfs/nfsroot.txt.
2313 nfs.callback_nr_threads=
2314 [NFSv4] set the total number of threads that the
2315 NFS client will assign to service NFSv4 callback
2318 nfs.callback_tcpport=
2319 [NFS] set the TCP port on which the NFSv4 callback
2320 channel should listen.
2323 [NFS] sets the pathname to the program which is used
2324 to update the NFS client cache entries.
2326 nfs.cache_getent_timeout=
2327 [NFS] sets the timeout after which an attempt to
2328 update a cache entry is deemed to have failed.
2330 nfs.idmap_cache_timeout=
2331 [NFS] set the maximum lifetime for idmapper cache
2335 [NFS] enable 64-bit inode numbers.
2336 If zero, the NFS client will fake up a 32-bit inode
2337 number for the readdir() and stat() syscalls instead
2338 of returning the full 64-bit number.
2339 The default is to return 64-bit inode numbers.
2341 nfs.max_session_cb_slots=
2342 [NFSv4.1] Sets the maximum number of session
2343 slots the client will assign to the callback
2344 channel. This determines the maximum number of
2345 callbacks the client will process in parallel for
2346 a particular server.
2348 nfs.max_session_slots=
2349 [NFSv4.1] Sets the maximum number of session slots
2350 the client will attempt to negotiate with the server.
2351 This limits the number of simultaneous RPC requests
2352 that the client can send to the NFSv4.1 server.
2353 Note that there is little point in setting this
2354 value higher than the max_tcp_slot_table_limit.
2356 nfs.nfs4_disable_idmapping=
2357 [NFSv4] When set to the default of '1', this option
2358 ensures that both the RPC level authentication
2359 scheme and the NFS level operations agree to use
2360 numeric uids/gids if the mount is using the
2361 'sec=sys' security flavour. In effect it is
2362 disabling idmapping, which can make migration from
2363 legacy NFSv2/v3 systems to NFSv4 easier.
2364 Servers that do not support this mode of operation
2365 will be autodetected by the client, and it will fall
2366 back to using the idmapper.
2367 To turn off this behaviour, set the value to '0'.
2369 [NFS4] Specify an additional fixed unique ident-
2370 ification string that NFSv4 clients can insert into
2371 their nfs_client_id4 string. This is typically a
2372 UUID that is generated at system install time.
2374 nfs.send_implementation_id =
2375 [NFSv4.1] Send client implementation identification
2376 information in exchange_id requests.
2377 If zero, no implementation identification information
2379 The default is to send the implementation identification
2382 nfs.recover_lost_locks =
2383 [NFSv4] Attempt to recover locks that were lost due
2384 to a lease timeout on the server. Please note that
2385 doing this risks data corruption, since there are
2386 no guarantees that the file will remain unchanged
2387 after the locks are lost.
2388 If you want to enable the kernel legacy behaviour of
2389 attempting to recover these locks, then set this
2391 The default parameter value of '0' causes the kernel
2392 not to attempt recovery of lost locks.
2394 nfs4.layoutstats_timer =
2395 [NFSv4.2] Change the rate at which the kernel sends
2396 layoutstats to the pNFS metadata server.
2398 Setting this to value to 0 causes the kernel to use
2399 whatever value is the default set by the layout
2400 driver. A non-zero value sets the minimum interval
2401 in seconds between layoutstats transmissions.
2403 nfsd.nfs4_disable_idmapping=
2404 [NFSv4] When set to the default of '1', the NFSv4
2405 server will return only numeric uids and gids to
2406 clients using auth_sys, and will accept numeric uids
2407 and gids from such clients. This is intended to ease
2408 migration from NFSv2/v3.
2410 objlayoutdriver.osd_login_prog=
2411 [NFS] [OBJLAYOUT] sets the pathname to the program which
2412 is used to automatically discover and login into new
2413 osd-targets. Please see:
2414 Documentation/filesystems/pnfs.txt for more explanations
2416 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2417 when a NMI is triggered.
2418 Format: [state][,regs][,debounce][,die]
2420 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2421 Format: [panic,][nopanic,][num]
2423 0 - turn hardlockup detector in nmi_watchdog off
2424 1 - turn hardlockup detector in nmi_watchdog on
2425 When panic is specified, panic when an NMI watchdog
2426 timeout occurs (or 'nopanic' to override the opposite
2427 default). To disable both hard and soft lockup detectors,
2428 please see 'nowatchdog'.
2429 This is useful when you use a panic=... timeout and
2430 need the box quickly up again.
2432 netpoll.carrier_timeout=
2433 [NET] Specifies amount of time (in seconds) that
2434 netpoll should wait for a carrier. By default netpoll
2437 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2438 emulation library even if a 387 maths coprocessor
2442 [HW] Never suspend the console
2443 Disable suspending of consoles during suspend and
2444 hibernate operations. Once disabled, debugging
2445 messages can reach various consoles while the rest
2446 of the system is being put to sleep (ie, while
2447 debugging driver suspend/resume hooks). This may
2448 not work reliably with all consoles, but is known
2449 to work with serial and VGA consoles.
2450 To facilitate more flexible debugging, we also add
2451 console_suspend, a printk module parameter to control
2452 it. Users could use console_suspend (usually
2453 /sys/module/printk/parameters/console_suspend) to
2454 turn on/off it dynamically.
2456 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2457 caches in the slab allocator. Saves per-node memory,
2458 but will impact performance.
2462 noapic [SMP,APIC] Tells the kernel to not make use of any
2463 IOAPICs that may be present in the system.
2465 noautogroup Disable scheduler automatic task group creation.
2467 nobats [PPC] Do not use BATs for mapping kernel lowmem
2468 on "Classic" PPC cores.
2472 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2474 nodelayacct [KNL] Disable per-task delay accounting
2476 nodsp [SH] Disable hardware DSP at boot time.
2478 noefi Disable EFI runtime services support.
2483 On X86-32 available only on PAE configured kernels.
2484 noexec=on: enable non-executable mappings (default)
2485 noexec=off: disable non-executable mappings
2488 Disable SMAP (Supervisor Mode Access Prevention)
2489 even if it is supported by processor.
2492 Disable SMEP (Supervisor Mode Execution Prevention)
2493 even if it is supported by processor.
2496 This affects only 32-bit executables.
2497 noexec32=on: enable non-executable mappings (default)
2498 read doesn't imply executable mappings
2499 noexec32=off: disable non-executable mappings
2500 read implies executable mappings
2502 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2504 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2505 register save and restore. The kernel will only save
2506 legacy floating-point registers on task switch.
2508 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2510 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
2511 Equivalent to smt=1.
2513 noxsave [BUGS=X86] Disables x86 extended register state save
2514 and restore using xsave. The kernel will fallback to
2515 enabling legacy floating-point and sse state.
2517 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2518 register states. The kernel will fall back to use
2519 xsave to save the states. By using this parameter,
2520 performance of saving the states is degraded because
2521 xsave doesn't support modified optimization while
2522 xsaveopt supports it on xsaveopt enabled systems.
2524 noxsaves [X86] Disables xsaves and xrstors used in saving and
2525 restoring x86 extended register state in compacted
2526 form of xsave area. The kernel will fall back to use
2527 xsaveopt and xrstor to save and restore the states
2528 in standard form of xsave area. By using this
2529 parameter, xsave area per process might occupy more
2530 memory on xsaves enabled systems.
2532 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2533 wfi(ARM) instruction doesn't work correctly and not to
2534 use it. This is also useful when using JTAG debugger.
2536 no_file_caps Tells the kernel not to honor file capabilities. The
2537 only way then for a file to be executed with privilege
2538 is to be setuid root or executed by root.
2540 nohalt [IA-64] Tells the kernel not to use the power saving
2541 function PAL_HALT_LIGHT when idle. This increases
2542 power-consumption. On the positive side, it reduces
2543 interrupt wake-up latency, which may improve performance
2544 in certain environments such as networked servers or
2547 nohibernate [HIBERNATION] Disable hibernation and resume.
2549 nohz= [KNL] Boottime enable/disable dynamic ticks
2550 Valid arguments: on, off
2553 nohz_full= [KNL,BOOT]
2554 The argument is a cpu list, as described above.
2555 In kernels built with CONFIG_NO_HZ_FULL=y, set
2556 the specified list of CPUs whose tick will be stopped
2557 whenever possible. The boot CPU will be forced outside
2558 the range to maintain the timekeeping.
2559 The CPUs in this range must also be included in the
2562 noiotrap [SH] Disables trapped I/O port accesses.
2564 noirqdebug [X86-32] Disables the code which attempts to detect and
2565 disable unhandled interrupt sources.
2567 no_timer_check [X86,APIC] Disables the code which tests for
2568 broken timer IRQ sources.
2570 noisapnp [ISAPNP] Disables ISA PnP code.
2572 noinitrd [RAM] Tells the kernel not to load any configured
2575 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2577 [Deprecated - use intremap=off]
2581 noinvpcid [X86] Disable the INVPCID cpu feature.
2583 nojitter [IA-64] Disables jitter checking for ITC timers.
2585 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2587 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2591 [X86,PV_OPS] Disable paravirtualized VMware scheduler
2592 clock and use the default one.
2594 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2595 steal time is computed, but won't influence scheduler
2598 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2600 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2602 noltlbs [PPC] Do not use large page/tlb entries for kernel
2603 lowmem mapping on PPC40x and PPC8xx
2605 nomca [IA-64] Disable machine check abort handling
2607 nomce [X86-32] Disable Machine Check Exception
2609 nomfgpt [X86-32] Disable Multi-Function General Purpose
2610 Timer usage (for AMD Geode machines).
2612 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2613 shutdown the other cpus. Instead use the REBOOT_VECTOR
2616 nomodule Disable module load
2618 nopat [X86] Disable PAT (page attribute table extension of
2619 pagetables) support.
2621 norandmaps Don't use address space randomization. Equivalent to
2622 echo 0 > /proc/sys/kernel/randomize_va_space
2624 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2626 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2627 with UP alternatives
2629 nordrand [X86] Disable kernel use of the RDRAND and
2630 RDSEED instructions even if they are supported
2631 by the processor. RDRAND and RDSEED are still
2632 available to user space applications.
2634 noresume [SWSUSP] Disables resume and restores original swap
2637 no-scroll [VGA] Disables scrollback.
2638 This is required for the Braillex ib80-piezo Braille
2639 reader made by F.H. Papenmeier (Germany).
2643 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2645 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2646 and disable the IO APIC. legacy for "maxcpus=0".
2648 nosoftlockup [KNL] Disable the soft-lockup detector.
2650 nosync [HW,M68K] Disables sync negotiation for all devices.
2652 notsc [BUGS=X86-32] Disable Time Stamp Counter
2654 nowatchdog [KNL] Disable both lockup detectors, i.e.
2655 soft-lockup and NMI watchdog (hard-lockup).
2659 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2661 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2662 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2663 Some features depend on CPU0. Known dependencies are:
2664 1. Resume from suspend/hibernate depends on CPU0.
2665 Suspend/hibernate will fail if CPU0 is offline and you
2666 need to online CPU0 before suspend/hibernate.
2667 2. PIC interrupts also depend on CPU0. CPU0 can't be
2668 removed if a PIC interrupt is detected.
2669 It's said poweroff/reboot may depend on CPU0 on some
2670 machines although I haven't seen such issues so far
2671 after CPU0 is offline on a few tested machines.
2672 If the dependencies are under your control, you can
2673 turn on cpu0_hotplug.
2675 nptcg= [IA-64] Override max number of concurrent global TLB
2676 purges which is reported from either PAL_VM_SUMMARY or
2679 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2680 could support. nr_cpus=n : n >= 1 limits the kernel to
2681 support 'n' processors. It could be larger than the
2682 number of already plugged CPU during bootup, later in
2683 runtime you can physically add extra cpu until it reaches
2684 n. So during boot up some boot time memory for per-cpu
2685 variables need be pre-allocated for later physical cpu
2688 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2690 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2691 Allowed values are enable and disable
2693 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2694 one of ['zone', 'node', 'default'] can be specified
2695 This can be set from sysctl after boot.
2696 See Documentation/sysctl/vm.txt for details.
2698 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2699 See Documentation/debugging-via-ohci1394.txt for more
2702 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2703 Rather than timing out after 20 ms if an EC
2704 command is not properly ACKed, override the length
2705 of the timeout. We have interrupts disabled while
2706 waiting for the ACK, so if this is set too high
2707 interrupts *may* be lost!
2709 omap_mux= [OMAP] Override bootloader pin multiplexing.
2710 Format: <mux_mode0.mode_name=value>...
2711 For example, to override I2C bus2:
2712 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2714 oprofile.timer= [HW]
2715 Use timer interrupt instead of performance counters
2717 oprofile.cpu_type= Force an oprofile cpu type
2718 This might be useful if you have an older oprofile
2719 userland or if you want common events.
2720 Format: { arch_perfmon }
2721 arch_perfmon: [X86] Force use of architectural
2722 perfmon on Intel CPUs instead of the
2723 CPU specific event set.
2724 timer: [X86] Force use of architectural NMI
2725 timer mode (see also oprofile.timer
2726 for generic hr timer mode)
2728 oops=panic Always panic on oopses. Default is to just kill the
2729 process, but there is a small probability of
2730 deadlocking the machine.
2731 This will also cause panics on machine check exceptions.
2732 Useful together with panic=30 to trigger a reboot.
2735 See Documentation/sound/oss/oss-parameters.txt
2737 page_owner= [KNL] Boot-time page_owner enabling option.
2738 Storage of the information about who allocated
2739 each page is disabled in default. With this switch,
2741 on: enable the feature
2743 page_poison= [KNL] Boot-time parameter changing the state of
2744 poisoning on the buddy allocator.
2745 off: turn off poisoning
2746 on: turn on poisoning
2748 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2749 timeout > 0: seconds before rebooting
2750 timeout = 0: wait forever
2751 timeout < 0: reboot immediately
2754 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2757 crash_kexec_post_notifiers
2758 Run kdump after running panic-notifiers and dumping
2759 kmsg. This only for the users who doubt kdump always
2760 succeeds in any situation.
2761 Note that this also increases risks of kdump failure,
2762 because some panic notifiers can make the crashed
2763 kernel more unstable.
2765 parkbd.port= [HW] Parallel port number the keyboard adapter is
2766 connected to, default is 0.
2768 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2769 0 for XT, 1 for AT (default is AT).
2772 parport= [HW,PPT] Specify parallel ports. 0 disables.
2773 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2774 Use 'auto' to force the driver to use any
2775 IRQ/DMA settings detected (the default is to
2776 ignore detected IRQ/DMA settings because of
2777 possible conflicts). You can specify the base
2778 address, IRQ, and DMA settings; IRQ and DMA
2779 should be numbers, or 'auto' (for using detected
2780 settings on that particular port), or 'nofifo'
2781 (to avoid using a FIFO even if it is detected).
2782 Parallel ports are assigned in the order they
2783 are specified on the command line, starting
2786 parport_init_mode= [HW,PPT]
2787 Configure VIA parallel port to operate in
2788 a specific mode. This is necessary on Pegasos
2789 computer where firmware has no options for setting
2790 up parallel port mode and sets it to spp.
2791 Currently this function knows 686a and 8231 chips.
2792 Format: [spp|ps2|epp|ecp|ecpepp]
2795 Halt all CPUs after the first oops has been printed for
2796 the specified number of seconds. This is to be used if
2797 your oopses keep scrolling off the screen.
2802 See header of drivers/block/paride/pcd.c.
2803 See also Documentation/blockdev/paride.txt.
2805 pci=option[,option...] [PCI] various PCI subsystem options:
2806 earlydump [X86] dump PCI config space before the kernel
2808 off [X86] don't probe for the PCI bus
2809 bios [X86-32] force use of PCI BIOS, don't access
2810 the hardware directly. Use this if your machine
2811 has a non-standard PCI host bridge.
2812 nobios [X86-32] disallow use of PCI BIOS, only direct
2813 hardware access methods are allowed. Use this
2814 if you experience crashes upon bootup and you
2815 suspect they are caused by the BIOS.
2816 conf1 [X86] Force use of PCI Configuration Access
2817 Mechanism 1 (config address in IO port 0xCF8,
2818 data in IO port 0xCFC, both 32-bit).
2819 conf2 [X86] Force use of PCI Configuration Access
2820 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
2821 the function, IO port 0xCFA, also 8-bit, sets
2822 bus number. The config space is then accessed
2823 through ports 0xC000-0xCFFF).
2824 See http://wiki.osdev.org/PCI for more info
2825 on the configuration access mechanisms.
2826 noaer [PCIE] If the PCIEAER kernel config parameter is
2827 enabled, this kernel boot option can be used to
2828 disable the use of PCIE advanced error reporting.
2829 nodomains [PCI] Disable support for multiple PCI
2830 root domains (aka PCI segments, in ACPI-speak).
2831 nommconf [X86] Disable use of MMCONFIG for PCI
2833 check_enable_amd_mmconf [X86] check for and enable
2834 properly configured MMIO access to PCI
2835 config space on AMD family 10h CPU
2836 nomsi [MSI] If the PCI_MSI kernel config parameter is
2837 enabled, this kernel boot option can be used to
2838 disable the use of MSI interrupts system-wide.
2839 noioapicquirk [APIC] Disable all boot interrupt quirks.
2840 Safety option to keep boot IRQs enabled. This
2841 should never be necessary.
2842 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2843 primary IO-APIC for bridges that cannot disable
2844 boot IRQs. This fixes a source of spurious IRQs
2845 when the system masks IRQs.
2846 noioapicreroute [APIC] Disable workaround that uses the
2847 boot IRQ equivalent of an IRQ that connects to
2848 a chipset where boot IRQs cannot be disabled.
2849 The opposite of ioapicreroute.
2850 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2851 routing table. These calls are known to be buggy
2852 on several machines and they hang the machine
2853 when used, but on other computers it's the only
2854 way to get the interrupt routing table. Try
2855 this option if the kernel is unable to allocate
2856 IRQs or discover secondary PCI buses on your
2858 rom [X86] Assign address space to expansion ROMs.
2859 Use with caution as certain devices share
2860 address decoders between ROMs and other
2862 norom [X86] Do not assign address space to
2863 expansion ROMs that do not already have
2864 BIOS assigned address ranges.
2865 nobar [X86] Do not assign address space to the
2866 BARs that weren't assigned by the BIOS.
2867 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2868 assigned automatically to PCI devices. You can
2869 make the kernel exclude IRQs of your ISA cards
2871 pirqaddr=0xAAAAA [X86] Specify the physical address
2872 of the PIRQ table (normally generated
2873 by the BIOS) if it is outside the
2874 F0000h-100000h range.
2875 lastbus=N [X86] Scan all buses thru bus #N. Can be
2876 useful if the kernel is unable to find your
2877 secondary buses and you want to tell it
2878 explicitly which ones they are.
2879 assign-busses [X86] Always assign all PCI bus
2880 numbers ourselves, overriding
2881 whatever the firmware may have done.
2882 usepirqmask [X86] Honor the possible IRQ mask stored
2883 in the BIOS $PIR table. This is needed on
2884 some systems with broken BIOSes, notably
2885 some HP Pavilion N5400 and Omnibook XE3
2886 notebooks. This will have no effect if ACPI
2887 IRQ routing is enabled.
2888 noacpi [X86] Do not use ACPI for IRQ routing
2889 or for PCI scanning.
2890 use_crs [X86] Use PCI host bridge window information
2891 from ACPI. On BIOSes from 2008 or later, this
2892 is enabled by default. If you need to use this,
2893 please report a bug.
2894 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2895 If you need to use this, please report a bug.
2896 routeirq Do IRQ routing for all PCI devices.
2897 This is normally done in pci_enable_device(),
2898 so this option is a temporary workaround
2899 for broken drivers that don't call it.
2900 skip_isa_align [X86] do not align io start addr, so can
2901 handle more pci cards
2902 noearly [X86] Don't do any early type 1 scanning.
2903 This might help on some broken boards which
2904 machine check when some devices' config space
2905 is read. But various workarounds are disabled
2906 and some IOMMU drivers will not work.
2907 bfsort Sort PCI devices into breadth-first order.
2908 This sorting is done to get a device
2909 order compatible with older (<= 2.4) kernels.
2910 nobfsort Don't sort PCI devices into breadth-first order.
2911 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2912 tuning and use the BIOS-configured MPS defaults.
2913 pcie_bus_safe Set every device's MPS to the largest value
2914 supported by all devices below the root complex.
2915 pcie_bus_perf Set device MPS to the largest allowable MPS
2916 based on its parent bus. Also set MRRS (Max
2917 Read Request Size) to the largest supported
2918 value (no larger than the MPS that the device
2919 or bus can support) for best performance.
2920 pcie_bus_peer2peer Set every device's MPS to 128B, which
2921 every device is guaranteed to support. This
2922 configuration allows peer-to-peer DMA between
2923 any pair of devices, possibly at the cost of
2924 reduced performance. This also guarantees
2925 that hot-added devices will work.
2926 cbiosize=nn[KMG] The fixed amount of bus space which is
2927 reserved for the CardBus bridge's IO window.
2928 The default value is 256 bytes.
2929 cbmemsize=nn[KMG] The fixed amount of bus space which is
2930 reserved for the CardBus bridge's memory
2931 window. The default value is 64 megabytes.
2934 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2935 [<order of align>@]pci:<vendor>:<device>\
2936 [:<subvendor>:<subdevice>][; ...]
2937 Specifies alignment and device to reassign
2938 aligned memory resources.
2939 If <order of align> is not specified,
2940 PAGE_SIZE is used as alignment.
2941 PCI-PCI bridge can be specified, if resource
2942 windows need to be expanded.
2943 To specify the alignment for several
2944 instances of a device, the PCI vendor,
2945 device, subvendor, and subdevice may be
2946 specified, e.g., 4096@pci:8086:9c22:103c:198f
2947 ecrc= Enable/disable PCIe ECRC (transaction layer
2948 end-to-end CRC checking).
2949 bios: Use BIOS/firmware settings. This is the
2953 hpiosize=nn[KMG] The fixed amount of bus space which is
2954 reserved for hotplug bridge's IO window.
2955 Default size is 256 bytes.
2956 hpmemsize=nn[KMG] The fixed amount of bus space which is
2957 reserved for hotplug bridge's memory window.
2958 Default size is 2 megabytes.
2959 hpbussize=nn The minimum amount of additional bus numbers
2960 reserved for buses below a hotplug bridge.
2962 realloc= Enable/disable reallocating PCI bridge resources
2963 if allocations done by BIOS are too small to
2964 accommodate resources required by all child
2966 off: Turn realloc off
2968 realloc same as realloc=on
2969 noari do not use PCIe ARI.
2970 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2971 only look for one device below a PCIe downstream
2974 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2977 force Enable ASPM even on devices that claim not to support it.
2978 WARNING: Forcing ASPM on may cause system lockups.
2980 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2981 nomsi Do not use MSI for PCI Express Native Hotplug (this
2982 makes all PCIe ports use INTx for hotplug services).
2984 pcie_ports= [PCIE] PCIe ports handling:
2985 auto Ask the BIOS whether or not to use native PCIe services
2986 associated with PCIe ports (PME, hot-plug, AER). Use
2987 them only if that is allowed by the BIOS.
2988 native Use native PCIe services associated with PCIe ports
2990 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2993 pcie_port_pm= [PCIE] PCIe port power management handling:
2994 off Disable power management of all PCIe ports
2995 force Forcibly enable power management of all PCIe ports
2997 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2998 nomsi Do not use MSI for native PCIe PME signaling (this makes
2999 all PCIe root ports use INTx for all services).
3001 pcmv= [HW,PCMCIA] BadgePAD 4
3005 Keep all power-domains already enabled by bootloader on,
3006 even if no driver has claimed them. This is useful
3007 for debug and development, but should not be
3008 needed on a platform with proper driver support.
3011 See Documentation/blockdev/paride.txt.
3013 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
3016 See arch/parisc/kernel/pdc_chassis.c
3018 percpu_alloc= Select which percpu first chunk allocator to use.
3019 Currently supported values are "embed" and "page".
3020 Archs may support subset or none of the selections.
3021 See comments in mm/percpu.c for details on each
3022 allocator. This parameter is primarily for debugging
3023 and performance comparison.
3026 See Documentation/blockdev/paride.txt.
3029 See Documentation/blockdev/paride.txt.
3031 pirq= [SMP,APIC] Manual mp-table setup
3032 See Documentation/x86/i386/IO-APIC.txt.
3034 plip= [PPT,NET] Parallel port network link
3035 Format: { parport<nr> | timid | 0 }
3036 See also Documentation/parport.txt.
3038 pmtmr= [X86] Manual setup of pmtmr I/O Port.
3039 Override pmtimer IOPort with a hex value.
3043 Enable PNP debug messages (depends on the
3044 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
3045 via /sys/module/pnp/parameters/debug. We always show
3046 current resource usage; turning this on also shows
3047 possible settings and some assignment information.
3053 { on | off | curr | res | no-curr | no-res }
3056 [ISAPNP] Exclude IRQs for the autoconfiguration
3059 [ISAPNP] Exclude DMAs for the autoconfiguration
3061 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
3062 Ranges are in pairs (I/O port base and size).
3065 [ISAPNP] Exclude memory regions for the
3067 Ranges are in pairs (memory base and size).
3069 ports= [IP_VS_FTP] IPVS ftp helper module
3071 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3073 Format: <port>,<port>....
3075 powersave=off [PPC] This option disables power saving features.
3076 It specifically disables cpuidle and sets the
3077 platform machine description specific power_save
3078 function to NULL. On Idle the CPU just reduces
3081 ppc_strict_facility_enable
3082 [PPC] This option catches any kernel floating point,
3083 Altivec, VSX and SPE outside of regions specifically
3084 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3085 There is some performance impact when enabling this.
3087 print-fatal-signals=
3088 [KNL] debug: print fatal signals
3090 If enabled, warn about various signal handling
3091 related application anomalies: too many signals,
3092 too many POSIX.1 timers, fatal signals causing a
3095 If you hit the warning due to signal overflow,
3096 you might want to try "ulimit -i unlimited".
3100 printk.always_kmsg_dump=
3101 Trigger kmsg_dump for cases other than kernel oops or
3103 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3106 printk.devkmsg={on,off,ratelimit}
3107 Control writing to /dev/kmsg.
3108 on - unlimited logging to /dev/kmsg from userspace
3109 off - logging to /dev/kmsg disabled
3110 ratelimit - ratelimit the logging
3113 printk.time= Show timing data prefixed to each printk message line
3114 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3116 processor.max_cstate= [HW,ACPI]
3117 Limit processor to maximum C-state
3118 max_cstate=9 overrides any DMI blacklist limit.
3120 processor.nocst [HW,ACPI]
3121 Ignore the _CST method to determine C-states,
3122 instead using the legacy FADT method
3124 profile= [KNL] Enable kernel profiling via /proc/profile
3125 Format: [schedule,]<number>
3126 Param: "schedule" - profile schedule points.
3127 Param: <number> - step/bucket size as a power of 2 for
3128 statistical time based profiling.
3129 Param: "sleep" - profile D-state sleeping (millisecs).
3130 Requires CONFIG_SCHEDSTATS
3131 Param: "kvm" - profile VM exits.
3133 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3135 See Documentation/blockdev/ramdisk.txt.
3137 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3138 probe for; one of (bare|imps|exps|lifebook|any).
3139 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3141 psmouse.resetafter= [HW,MOUSE]
3142 Try to reset the device after so many bad packets
3145 [HW,MOUSE] Set desired mouse resolution, in dpi.
3146 psmouse.smartscroll=
3147 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3148 0 = disabled, 1 = enabled (default).
3150 pstore.backend= Specify the name of the pstore backend to use
3153 See Documentation/blockdev/paride.txt.
3156 [KNL] Number of legacy pty's. Overwrites compiled-in
3159 quiet [KNL] Disable most log messages
3164 See Documentation/admin-guide/md.rst.
3166 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3167 See Documentation/blockdev/ramdisk.txt.
3170 The argument is a cpu list, as described above.
3172 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3173 the specified list of CPUs to be no-callback CPUs.
3174 Invocation of these CPUs' RCU callbacks will
3175 be offloaded to "rcuox/N" kthreads created for
3176 that purpose, where "x" is "b" for RCU-bh, "p"
3177 for RCU-preempt, and "s" for RCU-sched, and "N"
3178 is the CPU number. This reduces OS jitter on the
3179 offloaded CPUs, which can be useful for HPC and
3180 real-time workloads. It can also improve energy
3181 efficiency for asymmetric multiprocessors.
3184 Rather than requiring that offloaded CPUs
3185 (specified by rcu_nocbs= above) explicitly
3186 awaken the corresponding "rcuoN" kthreads,
3187 make these kthreads poll for callbacks.
3188 This improves the real-time response for the
3189 offloaded CPUs by relieving them of the need to
3190 wake up the corresponding kthread, but degrades
3191 energy efficiency by requiring that the kthreads
3192 periodically wake up to do the polling.
3194 rcutree.blimit= [KNL]
3195 Set maximum number of finished RCU callbacks to
3196 process in one batch.
3198 rcutree.dump_tree= [KNL]
3199 Dump the structure of the rcu_node combining tree
3200 out at early boot. This is used for diagnostic
3201 purposes, to verify correct tree setup.
3203 rcutree.gp_cleanup_delay= [KNL]
3204 Set the number of jiffies to delay each step of
3205 RCU grace-period cleanup. This only has effect
3206 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3208 rcutree.gp_init_delay= [KNL]
3209 Set the number of jiffies to delay each step of
3210 RCU grace-period initialization. This only has
3211 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3214 rcutree.gp_preinit_delay= [KNL]
3215 Set the number of jiffies to delay each step of
3216 RCU grace-period pre-initialization, that is,
3217 the propagation of recent CPU-hotplug changes up
3218 the rcu_node combining tree. This only has effect
3219 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3221 rcutree.rcu_fanout_exact= [KNL]
3222 Disable autobalancing of the rcu_node combining
3223 tree. This is used by rcutorture, and might
3224 possibly be useful for architectures having high
3225 cache-to-cache transfer latencies.
3227 rcutree.rcu_fanout_leaf= [KNL]
3228 Change the number of CPUs assigned to each
3229 leaf rcu_node structure. Useful for very
3230 large systems, which will choose the value 64,
3231 and for NUMA systems with large remote-access
3232 latencies, which will choose a value aligned
3233 with the appropriate hardware boundaries.
3235 rcutree.jiffies_till_sched_qs= [KNL]
3236 Set required age in jiffies for a
3237 given grace period before RCU starts
3238 soliciting quiescent-state help from
3239 rcu_note_context_switch().
3241 rcutree.jiffies_till_first_fqs= [KNL]
3242 Set delay from grace-period initialization to
3243 first attempt to force quiescent states.
3244 Units are jiffies, minimum value is zero,
3245 and maximum value is HZ.
3247 rcutree.jiffies_till_next_fqs= [KNL]
3248 Set delay between subsequent attempts to force
3249 quiescent states. Units are jiffies, minimum
3250 value is one, and maximum value is HZ.
3252 rcutree.kthread_prio= [KNL,BOOT]
3253 Set the SCHED_FIFO priority of the RCU per-CPU
3254 kthreads (rcuc/N). This value is also used for
3255 the priority of the RCU boost threads (rcub/N)
3256 and for the RCU grace-period kthreads (rcu_bh,
3257 rcu_preempt, and rcu_sched). If RCU_BOOST is
3258 set, valid values are 1-99 and the default is 1
3259 (the least-favored priority). Otherwise, when
3260 RCU_BOOST is not set, valid values are 0-99 and
3261 the default is zero (non-realtime operation).
3263 rcutree.rcu_nocb_leader_stride= [KNL]
3264 Set the number of NOCB kthread groups, which
3265 defaults to the square root of the number of
3266 CPUs. Larger numbers reduces the wakeup overhead
3267 on the per-CPU grace-period kthreads, but increases
3268 that same overhead on each group's leader.
3270 rcutree.qhimark= [KNL]
3271 Set threshold of queued RCU callbacks beyond which
3272 batch limiting is disabled.
3274 rcutree.qlowmark= [KNL]
3275 Set threshold of queued RCU callbacks below which
3276 batch limiting is re-enabled.
3278 rcutree.rcu_idle_gp_delay= [KNL]
3279 Set wakeup interval for idle CPUs that have
3280 RCU callbacks (RCU_FAST_NO_HZ=y).
3282 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3283 Set wakeup interval for idle CPUs that have
3284 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3285 Lazy RCU callbacks are those which RCU can
3286 prove do nothing more than free memory.
3288 rcutree.rcu_kick_kthreads= [KNL]
3289 Cause the grace-period kthread to get an extra
3290 wake_up() if it sleeps three times longer than
3291 it should at force-quiescent-state time.
3292 This wake_up() will be accompanied by a
3293 WARN_ONCE() splat and an ftrace_dump().
3295 rcuperf.gp_exp= [KNL]
3296 Measure performance of expedited synchronous
3297 grace-period primitives.
3299 rcuperf.holdoff= [KNL]
3300 Set test-start holdoff period. The purpose of
3301 this parameter is to delay the start of the
3302 test until boot completes in order to avoid
3305 rcuperf.nreaders= [KNL]
3306 Set number of RCU readers. The value -1 selects
3307 N, where N is the number of CPUs. A value
3308 "n" less than -1 selects N-n+1, where N is again
3309 the number of CPUs. For example, -2 selects N
3310 (the number of CPUs), -3 selects N+1, and so on.
3311 A value of "n" less than or equal to -N selects
3314 rcuperf.nwriters= [KNL]
3315 Set number of RCU writers. The values operate
3316 the same as for rcuperf.nreaders.
3317 N, where N is the number of CPUs
3319 rcuperf.perf_runnable= [BOOT]
3320 Start rcuperf running at boot time.
3322 rcuperf.shutdown= [KNL]
3323 Shut the system down after performance tests
3324 complete. This is useful for hands-off automated
3327 rcuperf.perf_type= [KNL]
3328 Specify the RCU implementation to test.
3330 rcuperf.verbose= [KNL]
3331 Enable additional printk() statements.
3333 rcutorture.cbflood_inter_holdoff= [KNL]
3334 Set holdoff time (jiffies) between successive
3335 callback-flood tests.
3337 rcutorture.cbflood_intra_holdoff= [KNL]
3338 Set holdoff time (jiffies) between successive
3339 bursts of callbacks within a given callback-flood
3342 rcutorture.cbflood_n_burst= [KNL]
3343 Set the number of bursts making up a given
3344 callback-flood test. Set this to zero to
3345 disable callback-flood testing.
3347 rcutorture.cbflood_n_per_burst= [KNL]
3348 Set the number of callbacks to be registered
3349 in a given burst of a callback-flood test.
3351 rcutorture.fqs_duration= [KNL]
3352 Set duration of force_quiescent_state bursts
3355 rcutorture.fqs_holdoff= [KNL]
3356 Set holdoff time within force_quiescent_state bursts
3359 rcutorture.fqs_stutter= [KNL]
3360 Set wait time between force_quiescent_state bursts
3363 rcutorture.gp_cond= [KNL]
3364 Use conditional/asynchronous update-side
3365 primitives, if available.
3367 rcutorture.gp_exp= [KNL]
3368 Use expedited update-side primitives, if available.
3370 rcutorture.gp_normal= [KNL]
3371 Use normal (non-expedited) asynchronous
3372 update-side primitives, if available.
3374 rcutorture.gp_sync= [KNL]
3375 Use normal (non-expedited) synchronous
3376 update-side primitives, if available. If all
3377 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3378 rcutorture.gp_normal=, and rcutorture.gp_sync=
3379 are zero, rcutorture acts as if is interpreted
3380 they are all non-zero.
3382 rcutorture.n_barrier_cbs= [KNL]
3383 Set callbacks/threads for rcu_barrier() testing.
3385 rcutorture.nfakewriters= [KNL]
3386 Set number of concurrent RCU writers. These just
3387 stress RCU, they don't participate in the actual
3388 test, hence the "fake".
3390 rcutorture.nreaders= [KNL]
3391 Set number of RCU readers. The value -1 selects
3392 N-1, where N is the number of CPUs. A value
3393 "n" less than -1 selects N-n-2, where N is again
3394 the number of CPUs. For example, -2 selects N
3395 (the number of CPUs), -3 selects N+1, and so on.
3397 rcutorture.object_debug= [KNL]
3398 Enable debug-object double-call_rcu() testing.
3400 rcutorture.onoff_holdoff= [KNL]
3401 Set time (s) after boot for CPU-hotplug testing.
3403 rcutorture.onoff_interval= [KNL]
3404 Set time (s) between CPU-hotplug operations, or
3405 zero to disable CPU-hotplug testing.
3407 rcutorture.shuffle_interval= [KNL]
3408 Set task-shuffle interval (s). Shuffling tasks
3409 allows some CPUs to go into dyntick-idle mode
3410 during the rcutorture test.
3412 rcutorture.shutdown_secs= [KNL]
3413 Set time (s) after boot system shutdown. This
3414 is useful for hands-off automated testing.
3416 rcutorture.stall_cpu= [KNL]
3417 Duration of CPU stall (s) to test RCU CPU stall
3418 warnings, zero to disable.
3420 rcutorture.stall_cpu_holdoff= [KNL]
3421 Time to wait (s) after boot before inducing stall.
3423 rcutorture.stat_interval= [KNL]
3424 Time (s) between statistics printk()s.
3426 rcutorture.stutter= [KNL]
3427 Time (s) to stutter testing, for example, specifying
3428 five seconds causes the test to run for five seconds,
3429 wait for five seconds, and so on. This tests RCU's
3430 ability to transition abruptly to and from idle.
3432 rcutorture.test_boost= [KNL]
3433 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3434 "Maybe" means test if the RCU implementation
3435 under test support RCU priority boosting.
3437 rcutorture.test_boost_duration= [KNL]
3438 Duration (s) of each individual boost test.
3440 rcutorture.test_boost_interval= [KNL]
3441 Interval (s) between each boost test.
3443 rcutorture.test_no_idle_hz= [KNL]
3444 Test RCU's dyntick-idle handling. See also the
3445 rcutorture.shuffle_interval parameter.
3447 rcutorture.torture_runnable= [BOOT]
3448 Start rcutorture running at boot time.
3450 rcutorture.torture_type= [KNL]
3451 Specify the RCU implementation to test.
3453 rcutorture.verbose= [KNL]
3454 Enable additional printk() statements.
3456 rcupdate.rcu_cpu_stall_suppress= [KNL]
3457 Suppress RCU CPU stall warning messages.
3459 rcupdate.rcu_cpu_stall_timeout= [KNL]
3460 Set timeout for RCU CPU stall warning messages.
3462 rcupdate.rcu_expedited= [KNL]
3463 Use expedited grace-period primitives, for
3464 example, synchronize_rcu_expedited() instead
3465 of synchronize_rcu(). This reduces latency,
3466 but can increase CPU utilization, degrade
3467 real-time latency, and degrade energy efficiency.
3468 No effect on CONFIG_TINY_RCU kernels.
3470 rcupdate.rcu_normal= [KNL]
3471 Use only normal grace-period primitives,
3472 for example, synchronize_rcu() instead of
3473 synchronize_rcu_expedited(). This improves
3474 real-time latency, CPU utilization, and
3475 energy efficiency, but can expose users to
3476 increased grace-period latency. This parameter
3477 overrides rcupdate.rcu_expedited. No effect on
3478 CONFIG_TINY_RCU kernels.
3480 rcupdate.rcu_normal_after_boot= [KNL]
3481 Once boot has completed (that is, after
3482 rcu_end_inkernel_boot() has been invoked), use
3483 only normal grace-period primitives. No effect
3484 on CONFIG_TINY_RCU kernels.
3486 rcupdate.rcu_task_stall_timeout= [KNL]
3487 Set timeout in jiffies for RCU task stall warning
3488 messages. Disable with a value less than or equal
3491 rcupdate.rcu_self_test= [KNL]
3492 Run the RCU early boot self tests
3494 rcupdate.rcu_self_test_bh= [KNL]
3495 Run the RCU bh early boot self tests
3497 rcupdate.rcu_self_test_sched= [KNL]
3498 Run the RCU sched early boot self tests
3502 Run specified binary instead of /init from the ramdisk,
3503 used for early userspace startup. See initrd.
3506 Format (x86 or x86_64):
3507 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3509 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3511 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3512 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3513 reboot_force is either force or not specified,
3514 reboot_cpu is s[mp]#### with #### being the processor
3515 to be used for rebooting.
3518 [KNL, SMP] Set scheduler's default relax_domain_level.
3519 See Documentation/cgroup-v1/cpusets.txt.
3521 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3523 reservetop= [X86-32]
3525 Reserves a hole at the top of the kernel virtual
3530 Set the amount of memory to reserve for BIOS at
3531 the bottom of the address space.
3533 reset_devices [KNL] Force drivers to reset the underlying device
3534 during initialization.
3537 Specify the partition device for software suspend
3539 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3541 resume_offset= [SWSUSP]
3542 Specify the offset from the beginning of the partition
3543 given by "resume=" at which the swap header is located,
3544 in <PAGE_SIZE> units (needed only for swap files).
3545 See Documentation/power/swsusp-and-swap-files.txt
3547 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3548 read the resume files
3550 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3551 Useful for devices that are detected asynchronously
3552 (e.g. USB and MMC devices).
3554 hibernate= [HIBERNATION]
3555 noresume Don't check if there's a hibernation image
3556 present during boot.
3557 nocompress Don't compress/decompress hibernation images.
3558 no Disable hibernation and resume.
3559 protect_image Turn on image protection during restoration
3560 (that will set all pages holding image data
3561 during restoration read-only).
3563 retain_initrd [RAM] Keep initrd memory after extraction
3565 rfkill.default_state=
3566 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3567 etc. communication is blocked by default.
3570 rfkill.master_switch_mode=
3571 0 The "airplane mode" button does nothing.
3572 1 The "airplane mode" button toggles between everything
3573 blocked and the previous configuration.
3574 2 The "airplane mode" button toggles between everything
3575 blocked and everything unblocked.
3577 rhash_entries= [KNL,NET]
3578 Set number of hash buckets for route cache
3581 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
3584 ro [KNL] Mount root device read-only on boot
3587 on Mark read-only kernel memory as read-only (default).
3588 off Leave read-only kernel memory writable for debugging.
3591 Enable the uart passthrough on the designated usb port
3592 on Rockchip SoCs. When active, the signals of the
3593 debug-uart get routed to the D+ and D- pins of the usb
3594 port and the regular usb controller gets disabled.
3596 root= [KNL] Root filesystem
3597 See name_to_dev_t comment in init/do_mounts.c.
3599 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3600 mount the root filesystem
3602 rootflags= [KNL] Set root filesystem mount option string
3604 rootfstype= [KNL] Set root filesystem type
3606 rootwait [KNL] Wait (indefinitely) for root device to show up.
3607 Useful for devices that are detected asynchronously
3608 (e.g. USB and MMC devices).
3610 rproc_mem=nn[KMG][@address]
3611 [KNL,ARM,CMA] Remoteproc physical memory block.
3612 Memory area to be used by remote processor image,
3615 rw [KNL] Mount root device read-write on boot
3617 S [KNL] Run init in single mode
3619 s390_iommu= [HW,S390]
3620 Set s390 IOTLB flushing mode
3622 With strict flushing every unmap operation will result in
3623 an IOTLB flush. Default is lazy flushing before reuse,
3627 See drivers/net/irda/sa1100_ir.c.
3629 sbni= [NET] Granch SBNI12 leased line adapter
3631 sched_debug [KNL] Enables verbose scheduler debug messages.
3633 schedstats= [KNL,X86] Enable or disable scheduled statistics.
3634 Allowed values are enable and disable. This feature
3635 incurs a small amount of overhead in the scheduler
3636 but is useful for debugging and performance tuning.
3638 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3639 xtime_lock contention on larger systems, and/or RCU lock
3640 contention on all systems with CONFIG_MAXSMP set.
3641 Format: { "0" | "1" }
3642 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3644 Note: increases power consumption, thus should only be
3645 enabled if running jitter sensitive (HPC/RT) workloads.
3647 security= [SECURITY] Choose a security module to enable at boot.
3648 If this boot parameter is not specified, only the first
3649 security module asking for security registration will be
3650 loaded. An invalid security module name will be treated
3651 as if no module has been chosen.
3653 selinux= [SELINUX] Disable or enable SELinux at boot time.
3654 Format: { "0" | "1" }
3655 See security/selinux/Kconfig help text.
3658 Default value is set via kernel config option.
3659 If enabled at boot time, /selinux/disable can be used
3660 later to disable prior to initial policy load.
3662 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3663 Format: { "0" | "1" }
3664 See security/apparmor/Kconfig help text
3667 Default value is set via kernel config option.
3669 serialnumber [BUGS=X86-32]
3672 Maximal number of shapers.
3680 Disable merging of slabs with similar size. May be
3681 necessary if there is some reason to distinguish
3682 allocs to different slabs. Debug options disable
3683 merging on their own.
3684 For more information see Documentation/vm/slub.txt.
3686 slab_max_order= [MM, SLAB]
3687 Determines the maximum allowed order for slabs.
3688 A high setting may cause OOMs due to memory
3689 fragmentation. Defaults to 1 for systems with
3690 more than 32MB of RAM, 0 otherwise.
3692 slub_debug[=options[,slabs]] [MM, SLUB]
3693 Enabling slub_debug allows one to determine the
3694 culprit if slab objects become corrupted. Enabling
3695 slub_debug can create guard zones around objects and
3696 may poison objects when not in use. Also tracks the
3697 last alloc / free. For more information see
3698 Documentation/vm/slub.txt.
3700 slub_memcg_sysfs= [MM, SLUB]
3701 Determines whether to enable sysfs directories for
3702 memory cgroup sub-caches. 1 to enable, 0 to disable.
3703 The default is determined by CONFIG_SLUB_MEMCG_SYSFS_ON.
3704 Enabling this can lead to a very high number of debug
3705 directories and files being created under
3708 slub_max_order= [MM, SLUB]
3709 Determines the maximum allowed order for slabs.
3710 A high setting may cause OOMs due to memory
3711 fragmentation. For more information see
3712 Documentation/vm/slub.txt.
3714 slub_min_objects= [MM, SLUB]
3715 The minimum number of objects per slab. SLUB will
3716 increase the slab order up to slub_max_order to
3717 generate a sufficiently large slab able to contain
3718 the number of objects indicated. The higher the number
3719 of objects the smaller the overhead of tracking slabs
3720 and the less frequently locks need to be acquired.
3721 For more information see Documentation/vm/slub.txt.
3723 slub_min_order= [MM, SLUB]
3724 Determines the minimum page order for slabs. Must be
3725 lower than slub_max_order.
3726 For more information see Documentation/vm/slub.txt.
3728 slub_nomerge [MM, SLUB]
3729 Same with slab_nomerge. This is supported for legacy.
3730 See slab_nomerge for more information.
3733 Format: <io1>[,<io2>[,...,<io8>]]
3735 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3736 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3737 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3738 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3739 smsc-ircc2.ircc_irq= [HW] IRQ line
3740 smsc-ircc2.ircc_dma= [HW] DMA channel
3741 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3742 0: Toshiba Satellite 1800 (GP data pin select)
3743 1: Fast pin select (default)
3746 smt [KNL,S390] Set the maximum number of threads (logical
3747 CPUs) to use per physical CPU on systems capable of
3748 symmetric multithreading (SMT). Will be capped to the
3749 actual hardware limit.
3751 Default: -1 (no limit)
3754 [KNL] Should the soft-lockup detector generate panics.
3757 softlockup_all_cpu_backtrace=
3758 [KNL] Should the soft-lockup detector generate
3759 backtraces on all cpus.
3762 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3763 See Documentation/laptops/sonypi.txt
3765 spia_io_base= [HW,MTD]
3771 Enabled the stack tracer on boot up.
3773 stacktrace_filter=[function-list]
3774 [FTRACE] Limit the functions that the stack tracer
3775 will trace at boot up. function-list is a comma separated
3776 list of functions. This list can be changed at run
3777 time by the stack_trace_filter file in the debugfs
3778 tracing directory. Note, this enables stack tracing
3779 and the stacktrace above is not needed.
3783 Set the STI (builtin display/keyboard on the HP-PARISC
3784 machines) console (graphic card) which should be used
3785 as the initial boot-console.
3786 See also comment in drivers/video/console/sticore.c.
3789 See comment in drivers/video/console/sticore.c.
3792 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3794 sunrpc.min_resvport=
3795 sunrpc.max_resvport=
3797 SunRPC servers often require that client requests
3798 originate from a privileged port (i.e. a port in the
3799 range 0 < portnr < 1024).
3800 An administrator who wishes to reserve some of these
3801 ports for other uses may adjust the range that the
3802 kernel's sunrpc client considers to be privileged
3803 using these two parameters to set the minimum and
3804 maximum port values.
3806 sunrpc.svc_rpc_per_connection_limit=
3808 Limit the number of requests that the server will
3809 process in parallel from a single connection.
3810 The default value is 0 (no limit).
3814 Control how the NFS server code allocates CPUs to
3815 service thread pools. Depending on how many NICs
3816 you have and where their interrupts are bound, this
3817 option will affect which CPUs will do NFS serving.
3818 Note: this parameter cannot be changed while the
3819 NFS server is running.
3821 auto the server chooses an appropriate mode
3822 automatically using heuristics
3823 global a single global pool contains all CPUs
3824 percpu one pool for each CPU
3825 pernode one pool for each NUMA node (equivalent
3826 to global on non-NUMA machines)
3828 sunrpc.tcp_slot_table_entries=
3829 sunrpc.udp_slot_table_entries=
3831 Sets the upper limit on the number of simultaneous
3832 RPC calls that can be sent from the client to a
3833 server. Increasing these values may allow you to
3834 improve throughput, but will also increase the
3835 amount of memory reserved for use by the client.
3837 suspend.pm_test_delay=
3839 Sets the number of seconds to remain in a suspend test
3840 mode before resuming the system (see
3841 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3842 is set. Default value is 5.
3845 [KNL] Enable accounting of swap in memory resource
3846 controller if no parameter or 1 is given or disable
3847 it if 0 is given (See Documentation/cgroup-v1/memory.txt)
3849 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3850 Format: { <int> | force | noforce }
3851 <int> -- Number of I/O TLB slabs
3852 force -- force using of bounce buffers even if they
3853 wouldn't be automatically used by the kernel
3854 noforce -- Never use bounce buffers (for debugging)
3858 sysfs.deprecated=0|1 [KNL]
3859 Enable/disable old style sysfs layout for old udev
3860 on older distributions. When this option is enabled
3861 very new udev will not work anymore. When this option
3862 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3863 in older udev will not work anymore.
3864 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3865 the kernel configuration.
3867 sysrq_always_enabled
3869 Ignore sysrq setting - this boot parameter will
3870 neutralize any effect of /proc/sys/kernel/sysrq.
3871 Useful for debugging.
3873 tcpmhash_entries= [KNL,NET]
3874 Set the number of tcp_metrics_hash slots.
3875 Default value is 8192 or 16384 depending on total
3876 ram pages. This is used to specify the TCP metrics
3877 cache size. See Documentation/networking/ip-sysctl.txt
3878 "tcp_no_metrics_save" section for more details.
3882 test_suspend= [SUSPEND][,N]
3883 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3884 standby suspend) or "freeze" (for suspend type freeze)
3885 as the system sleep state during system startup with
3886 the optional capability to repeat N number of times.
3887 The system is woken from this state using a
3888 wakeup-capable RTC alarm.
3890 thash_entries= [KNL,NET]
3891 Set number of hash buckets for TCP connection
3893 thermal.act= [HW,ACPI]
3894 -1: disable all active trip points in all thermal zones
3895 <degrees C>: override all lowest active trip points
3897 thermal.crt= [HW,ACPI]
3898 -1: disable all critical trip points in all thermal zones
3899 <degrees C>: override all critical trip points
3901 thermal.nocrt= [HW,ACPI]
3902 Set to disable actions on ACPI thermal zone
3903 critical and hot trip points.
3905 thermal.off= [HW,ACPI]
3906 1: disable ACPI thermal control
3908 thermal.psv= [HW,ACPI]
3909 -1: disable all passive trip points
3910 <degrees C>: override all passive trip points to this
3913 thermal.tzp= [HW,ACPI]
3914 Specify global default ACPI thermal zone polling rate
3915 <deci-seconds>: poll all this frequency
3916 0: no polling (default)
3919 Force threading of all interrupt handlers except those
3920 marked explicitly IRQF_NO_THREAD.
3923 Enable the Transcendent memory driver if built-in.
3925 tmem.cleancache=0|1 [KNL, XEN]
3926 Default is on (1). Disable the usage of the cleancache
3927 API to send anonymous pages to the hypervisor.
3929 tmem.frontswap=0|1 [KNL, XEN]
3930 Default is on (1). Disable the usage of the frontswap
3931 API to send swap pages to the hypervisor. If disabled
3932 the selfballooning and selfshrinking are force disabled.
3934 tmem.selfballooning=0|1 [KNL, XEN]
3935 Default is on (1). Disable the driving of swap pages
3938 tmem.selfshrinking=0|1 [KNL, XEN]
3939 Default is on (1). Partial swapoff that immediately
3940 transfers pages from Xen hypervisor back to the
3941 kernel based on different criteria.
3945 Specify if the kernel should make use of the cpu
3946 topology information if the hardware supports this.
3947 The scheduler will make use of this information and
3948 e.g. base its process migration decisions on it.
3951 topology_updates= [KNL, PPC, NUMA]
3953 Specify if the kernel should ignore (off)
3954 topology updates sent by the hypervisor to this
3959 tpm_suspend_pcr=[HW,TPM]
3960 Format: integer pcr id
3961 Specify that at suspend time, the tpm driver
3962 should extend the specified pcr with zeros,
3963 as a workaround for some chips which fail to
3964 flush the last written pcr on TPM_SaveState.
3965 This will guarantee that all the other pcrs
3968 trace_buf_size=nn[KMG]
3969 [FTRACE] will set tracing buffer size on each cpu.
3971 trace_event=[event-list]
3972 [FTRACE] Set and start specified trace events in order
3973 to facilitate early boot debugging. The event-list is a
3974 comma separated list of trace events to enable. See
3975 also Documentation/trace/events.txt
3977 trace_options=[option-list]
3978 [FTRACE] Enable or disable tracer options at boot.
3979 The option-list is a comma delimited list of options
3980 that can be enabled or disabled just as if you were
3981 to echo the option name into
3983 /sys/kernel/debug/tracing/trace_options
3985 For example, to enable stacktrace option (to dump the
3986 stack trace of each event), add to the command line:
3988 trace_options=stacktrace
3990 See also Documentation/trace/ftrace.txt "trace options"
3994 Have the tracepoints sent to printk as well as the
3995 tracing ring buffer. This is useful for early boot up
3996 where the system hangs or reboots and does not give the
3997 option for reading the tracing buffer or performing a
3998 ftrace_dump_on_oops.
4000 To turn off having tracepoints sent to printk,
4001 echo 0 > /proc/sys/kernel/tracepoint_printk
4002 Note, echoing 1 into this file without the
4003 tracepoint_printk kernel cmdline option has no effect.
4007 Having tracepoints sent to printk() and activating high
4008 frequency tracepoints such as irq or sched, can cause
4009 the system to live lock.
4012 [FTRACE] enable this option to disable tracing when a
4013 warning is hit. This turns off "tracing_on". Tracing can
4014 be enabled again by echoing '1' into the "tracing_on"
4015 file located in /sys/kernel/debug/tracing/
4017 This option is useful, as it disables the trace before
4018 the WARNING dump is called, which prevents the trace to
4019 be filled with content caused by the warning output.
4021 This option can also be set at run time via the sysctl
4022 option: kernel/traceoff_on_warning
4024 transparent_hugepage=
4026 Format: [always|madvise|never]
4027 Can be used to control the default behavior of the system
4028 with respect to transparent hugepages.
4029 See Documentation/vm/transhuge.txt for more details.
4031 tsc= Disable clocksource stability checks for TSC.
4033 [x86] reliable: mark tsc clocksource as reliable, this
4034 disables clocksource verification at runtime, as well
4035 as the stability checks done at bootup. Used to enable
4036 high-resolution timer mode on older hardware, and in
4037 virtualized environment.
4038 [x86] noirqtime: Do not use TSC to do irq accounting.
4039 Used to run time disable IRQ_TIME_ACCOUNTING on any
4040 platforms where RDTSC is slow and this accounting
4043 turbografx.map[2|3]= [HW,JOY]
4044 TurboGraFX parallel port interface
4046 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
4047 See also Documentation/input/joystick-parport.txt
4049 udbg-immortal [PPC] When debugging early kernel crashes that
4050 happen after console_init() and before a proper
4051 console driver takes over, this boot options might
4052 help "seeing" what's going on.
4054 uhash_entries= [KNL,NET]
4055 Set number of hash buckets for UDP/UDP-Lite connections
4058 [USB] Ignore overcurrent events (default N).
4059 Some badly-designed motherboards generate lots of
4060 bogus events, for ports that aren't wired to
4061 anything. Set this parameter to avoid log spamming.
4062 Note that genuine overcurrent events won't be
4066 [X86] Cause panic on unknown NMI.
4068 usbcore.authorized_default=
4069 [USB] Default USB device authorization:
4070 (default -1 = authorized except for wireless USB,
4071 0 = not authorized, 1 = authorized)
4073 usbcore.autosuspend=
4074 [USB] The autosuspend time delay (in seconds) used
4075 for newly-detected USB devices (default 2). This
4076 is the time required before an idle device will be
4077 autosuspended. Devices for which the delay is set
4078 to a negative value won't be autosuspended at all.
4080 usbcore.usbfs_snoop=
4081 [USB] Set to log all usbfs traffic (default 0 = off).
4083 usbcore.usbfs_snoop_max=
4084 [USB] Maximum number of bytes to snoop in each URB
4087 usbcore.blinkenlights=
4088 [USB] Set to cycle leds on hubs (default 0 = off).
4090 usbcore.old_scheme_first=
4091 [USB] Start with the old device initialization
4092 scheme (default 0 = off).
4094 usbcore.usbfs_memory_mb=
4095 [USB] Memory limit (in MB) for buffers allocated by
4096 usbfs (default = 16, 0 = max = 2047).
4098 usbcore.use_both_schemes=
4099 [USB] Try the other device initialization scheme
4100 if the first one fails (default 1 = enabled).
4102 usbcore.initial_descriptor_timeout=
4103 [USB] Specifies timeout for the initial 64-byte
4104 USB_REQ_GET_DESCRIPTOR request in milliseconds
4105 (default 5000 = 5.0 seconds).
4107 usbcore.nousb [USB] Disable the USB subsystem
4110 [USBHID] The interval which mice are to be polled at.
4112 usb-storage.delay_use=
4113 [UMS] The delay in seconds before a new device is
4114 scanned for Logical Units (default 1).
4117 [UMS] A list of quirks entries to supplement or
4118 override the built-in unusual_devs list. List
4119 entries are separated by commas. Each entry has
4120 the form VID:PID:Flags where VID and PID are Vendor
4121 and Product ID values (4-digit hex numbers) and
4122 Flags is a set of characters, each corresponding
4123 to a common usb-storage quirk flag as follows:
4124 a = SANE_SENSE (collect more than 18 bytes
4126 b = BAD_SENSE (don't collect more than 18
4127 bytes of sense data);
4128 c = FIX_CAPACITY (decrease the reported
4129 device capacity by one sector);
4130 d = NO_READ_DISC_INFO (don't use
4131 READ_DISC_INFO command);
4132 e = NO_READ_CAPACITY_16 (don't use
4133 READ_CAPACITY_16 command);
4134 f = NO_REPORT_OPCODES (don't use report opcodes
4136 g = MAX_SECTORS_240 (don't transfer more than
4137 240 sectors at a time, uas only);
4138 h = CAPACITY_HEURISTICS (decrease the
4139 reported device capacity by one
4140 sector if the number is odd);
4141 i = IGNORE_DEVICE (don't bind to this
4143 j = NO_REPORT_LUNS (don't use report luns
4145 l = NOT_LOCKABLE (don't try to lock and
4146 unlock ejectable media);
4147 m = MAX_SECTORS_64 (don't transfer more
4148 than 64 sectors = 32 KB at a time);
4149 n = INITIAL_READ10 (force a retry of the
4150 initial READ(10) command);
4151 o = CAPACITY_OK (accept the capacity
4152 reported by the device);
4153 p = WRITE_CACHE (the device cache is ON
4155 r = IGNORE_RESIDUE (the device reports
4156 bogus residue values);
4157 s = SINGLE_LUN (the device has only one
4159 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4160 commands, uas only);
4161 u = IGNORE_UAS (don't bind to the uas driver);
4162 w = NO_WP_DETECT (don't test whether the
4163 medium is write-protected).
4164 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
4165 even if the device claims no cache)
4166 Example: quirks=0419:aaf5:rl,0421:0433:rc
4168 user_debug= [KNL,ARM]
4170 See arch/arm/Kconfig.debug help text.
4171 1 - undefined instruction events
4173 4 - invalid data aborts
4176 Example: user_debug=31
4179 [X86] Flags controlling user PTE allocations.
4181 nohigh = do not allocate PTE pages in
4182 HIGHMEM regardless of setting
4186 On X86_32, this is an alias for vdso32=. Otherwise:
4188 vdso=1: enable VDSO (the default)
4189 vdso=0: disable VDSO mapping
4191 vdso32= [X86] Control the 32-bit vDSO
4192 vdso32=1: enable 32-bit VDSO
4193 vdso32=0 or vdso32=2: disable 32-bit VDSO
4195 See the help text for CONFIG_COMPAT_VDSO for more
4196 details. If CONFIG_COMPAT_VDSO is set, the default is
4197 vdso32=0; otherwise, the default is vdso32=1.
4199 For compatibility with older kernels, vdso32=2 is an
4202 Try vdso32=0 if you encounter an error that says:
4203 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
4206 vector=percpu: enable percpu vector domain
4208 video= [FB] Frame buffer configuration
4209 See Documentation/fb/modedb.txt.
4211 video.brightness_switch_enabled= [0,1]
4212 If set to 1, on receiving an ACPI notify event
4213 generated by hotkey, video driver will adjust brightness
4214 level and then send out the event to user space through
4215 the allocated input device; If set to 0, video driver
4216 will only send out the event without touching backlight
4221 [VMMIO] Memory mapped virtio (platform) device.
4223 <size>@<baseaddr>:<irq>[:<id>]
4225 <size> := size (can use standard suffixes
4227 <baseaddr> := physical base address
4228 <irq> := interrupt number (as passed to
4230 <id> := (optional) platform device id
4232 virtio_mmio.device=1K@0x100b0000:48:7
4234 Can be used multiple times for multiple devices.
4236 vga= [BOOT,X86-32] Select a particular video mode
4237 See Documentation/x86/boot.txt and
4238 Documentation/svga.txt.
4239 Use vga=ask for menu.
4240 This is actually a boot loader parameter; the value is
4241 passed to the kernel using a special protocol.
4243 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4244 size of <nn>. This can be used to increase the
4245 minimum size (128MB on x86). It can also be used to
4246 decrease the size and leave more room for directly
4249 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4252 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4255 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4259 Controls the behavior of vsyscalls (i.e. calls to
4260 fixed addresses of 0xffffffffff600x00 from legacy
4261 code). Most statically-linked binaries and older
4262 versions of glibc use these calls. Because these
4263 functions are at fixed addresses, they make nice
4264 targets for exploits that can control RIP.
4266 emulate [default] Vsyscalls turn into traps and are
4267 emulated reasonably safely.
4269 native Vsyscalls are native syscall instructions.
4270 This is a little bit faster than trapping
4271 and makes a few dynamic recompilers work
4272 better than they would in emulation mode.
4273 It also makes exploits much easier to write.
4275 none Vsyscalls don't work at all. This makes
4276 them quite hard to use for exploits but
4277 might break your system.
4279 vt.color= [VT] Default text color.
4280 Format: 0xYX, X = foreground, Y = background.
4281 Default: 0x07 = light gray on black.
4283 vt.cur_default= [VT] Default cursor shape.
4284 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4285 the parameters of the <Esc>[?A;B;Cc escape sequence;
4286 see VGA-softcursor.txt. Default: 2 = underline.
4288 vt.default_blu= [VT]
4289 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4290 Change the default blue palette of the console.
4291 This is a 16-member array composed of values
4294 vt.default_grn= [VT]
4295 Format: <green0>,<green1>,<green2>,...,<green15>
4296 Change the default green palette of the console.
4297 This is a 16-member array composed of values
4300 vt.default_red= [VT]
4301 Format: <red0>,<red1>,<red2>,...,<red15>
4302 Change the default red palette of the console.
4303 This is a 16-member array composed of values
4309 Set system-wide default UTF-8 mode for all tty's.
4310 Default is 1, i.e. UTF-8 mode is enabled for all
4311 newly opened terminals.
4313 vt.global_cursor_default=
4316 Set system-wide default for whether a cursor
4317 is shown on new VTs. Default is -1,
4318 i.e. cursors will be created by default unless
4319 overridden by individual drivers. 0 will hide
4320 cursors, 1 will display them.
4322 vt.italic= [VT] Default color for italic text; 0-15.
4325 vt.underline= [VT] Default color for underlined text; 0-15.
4328 watchdog timers [HW,WDT] For information on watchdog timers,
4329 see Documentation/watchdog/watchdog-parameters.txt
4330 or other driver-specific files in the
4331 Documentation/watchdog/ directory.
4333 workqueue.watchdog_thresh=
4334 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4335 warn stall conditions and dump internal state to
4336 help debugging. 0 disables workqueue stall
4337 detection; otherwise, it's the stall threshold
4338 duration in seconds. The default value is 30 and
4339 it can be updated at runtime by writing to the
4340 corresponding sysfs file.
4342 workqueue.disable_numa
4343 By default, all work items queued to unbound
4344 workqueues are affine to the NUMA nodes they're
4345 issued on, which results in better behavior in
4346 general. If NUMA affinity needs to be disabled for
4347 whatever reason, this option can be used. Note
4348 that this also can be controlled per-workqueue for
4349 workqueues visible under /sys/bus/workqueue/.
4351 workqueue.power_efficient
4352 Per-cpu workqueues are generally preferred because
4353 they show better performance thanks to cache
4354 locality; unfortunately, per-cpu workqueues tend to
4355 be more power hungry than unbound workqueues.
4357 Enabling this makes the per-cpu workqueues which
4358 were observed to contribute significantly to power
4359 consumption unbound, leading to measurably lower
4360 power usage at the cost of small performance
4363 The default value of this parameter is determined by
4364 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4366 workqueue.debug_force_rr_cpu
4367 Workqueue used to implicitly guarantee that work
4368 items queued without explicit CPU specified are put
4369 on the local CPU. This guarantee is no longer true
4370 and while local CPU is still preferred work items
4371 may be put on foreign CPUs. This debug option
4372 forces round-robin CPU selection to flush out
4373 usages which depend on the now broken guarantee.
4374 When enabled, memory and cache locality will be
4377 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4378 default x2apic cluster mode on platforms
4381 x86_intel_mid_timer= [X86-32,APBT]
4382 Choose timer option for x86 Intel MID platform.
4383 Two valid options are apbt timer only and lapic timer
4384 plus one apbt timer for broadcast timer.
4385 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4387 xen_512gb_limit [KNL,X86-64,XEN]
4388 Restricts the kernel running paravirtualized under Xen
4389 to use only up to 512 GB of RAM. The reason to do so is
4390 crash analysis tools and Xen tools for doing domain
4391 save/restore/migration must be enabled to handle larger
4394 xen_emul_unplug= [HW,X86,XEN]
4395 Unplug Xen emulated devices
4396 Format: [unplug0,][unplug1]
4397 ide-disks -- unplug primary master IDE devices
4398 aux-ide-disks -- unplug non-primary-master IDE devices
4399 nics -- unplug network devices
4400 all -- unplug all emulated devices (NICs and IDE disks)
4401 unnecessary -- unplugging emulated devices is
4402 unnecessary even if the host did not respond to
4404 never -- do not unplug even if version check succeeds
4406 xen_nopvspin [X86,XEN]
4407 Disables the ticketlock slowpath using Xen PV
4411 Disables the PV optimizations forcing the HVM guest to
4412 run as generic HVM guest with no PV drivers.
4414 xirc2ps_cs= [NET,PCMCIA]
4416 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
git.samba.org / sfrench / cifs-2.6.git / blob