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
118 acpi_no_auto_serialize [HW,ACPI]
119 Disable auto-serialization of AML methods
120 AML control methods that contain the opcodes to create
121 named objects will be marked as "Serialized" by the
122 auto-serialization feature.
123 This feature is enabled by default.
124 This option allows to turn off the feature.
126 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
129 acpi_no_static_ssdt [HW,ACPI]
130 Disable installation of static SSDTs at early boot time
131 By default, SSDTs contained in the RSDT/XSDT will be
132 installed automatically and they will appear under
133 /sys/firmware/acpi/tables.
134 This option turns off this feature.
135 Note that specifying this option does not affect
136 dynamic table installation which will install SSDT
137 tables to /sys/firmware/acpi/tables/dynamic.
139 acpi_rsdp= [ACPI,EFI,KEXEC]
140 Pass the RSDP address to the kernel, mostly used
141 on machines running EFI runtime service to boot the
142 second kernel for kdump.
144 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
145 Format: To spoof as Windows 98: ="Microsoft Windows"
147 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
148 of 2 which is mandated by ACPI 6) as the supported ACPI
149 specification revision (when using this switch, it may
150 be necessary to carry out a cold reboot _twice_ in a
151 row to make it take effect on the platform firmware).
153 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
154 acpi_osi="string1" # add string1
155 acpi_osi="!string2" # remove string2
156 acpi_osi=!* # remove all strings
157 acpi_osi=! # disable all built-in OS vendor
159 acpi_osi=!! # enable all built-in OS vendor
161 acpi_osi= # disable all strings
163 'acpi_osi=!' can be used in combination with single or
164 multiple 'acpi_osi="string1"' to support specific OS
165 vendor string(s). Note that such command can only
166 affect the default state of the OS vendor strings, thus
167 it cannot affect the default state of the feature group
168 strings and the current state of the OS vendor strings,
169 specifying it multiple times through kernel command line
170 is meaningless. This command is useful when one do not
171 care about the state of the feature group strings which
172 should be controlled by the OSPM.
174 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
175 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
176 can make '_OSI("Windows 2000")' TRUE.
178 'acpi_osi=' cannot be used in combination with other
179 'acpi_osi=' command lines, the _OSI method will not
180 exist in the ACPI namespace. NOTE that such command can
181 only affect the _OSI support state, thus specifying it
182 multiple times through kernel command line is also
185 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
188 'acpi_osi=!*' can be used in combination with single or
189 multiple 'acpi_osi="string1"' to support specific
190 string(s). Note that such command can affect the
191 current state of both the OS vendor strings and the
192 feature group strings, thus specifying it multiple times
193 through kernel command line is meaningful. But it may
194 still not able to affect the final state of a string if
195 there are quirks related to this string. This command
196 is useful when one want to control the state of the
197 feature group strings to debug BIOS issues related to
200 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
201 '_OSI("Module Device")' FALSE.
202 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
203 '_OSI("Module Device")' TRUE.
204 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
206 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
208 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
209 they all will make '_OSI("Windows 2000")' TRUE.
212 Override the pmtimer bug detection: force the kernel
213 to assume that this machine's pmtimer latches its value
214 and always returns good values.
216 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
217 Format: { level | edge | high | low }
219 acpi_skip_timer_override [HW,ACPI]
220 Recognize and ignore IRQ0/pin2 Interrupt Override.
221 For broken nForce2 BIOS resulting in XT-PIC timer.
223 acpi_sleep= [HW,ACPI] Sleep options
224 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
225 old_ordering, nonvs, sci_force_enable, nobl }
226 See Documentation/power/video.txt for information on
228 s3_beep is for debugging; it makes the PC's speaker beep
229 as soon as the kernel's real-mode entry point is called.
230 s4_nohwsig prevents ACPI hardware signature from being
231 used during resume from hibernation.
232 old_ordering causes the ACPI 1.0 ordering of the _PTS
233 control method, with respect to putting devices into
234 low power states, to be enforced (the ACPI 2.0 ordering
235 of _PTS is used by default).
236 nonvs prevents the kernel from saving/restoring the
237 ACPI NVS memory during suspend/hibernation and resume.
238 sci_force_enable causes the kernel to set SCI_EN directly
239 on resume from S1/S3 (which is against the ACPI spec,
240 but some broken systems don't work without it).
241 nobl causes the internal blacklist of systems known to
242 behave incorrectly in some ways with respect to system
243 suspend and resume to be ignored (use wisely).
245 acpi_use_timer_override [HW,ACPI]
246 Use timer override. For some broken Nvidia NF5 boards
247 that require a timer override, but don't have HPET
249 add_efi_memmap [EFI; X86] Include EFI memory map in
250 kernel's map of available physical RAM.
253 { off | try_unsupported }
254 off: disable AGP support
255 try_unsupported: try to drive unsupported chipsets
256 (may crash computer or cause data corruption)
259 See Documentation/sound/alsa/alsa-parameters.txt
262 Allow the default userspace alignment fault handler
263 behaviour to be specified. Bit 0 enables warnings,
264 bit 1 enables fixups, and bit 2 sends a segfault.
266 align_va_addr= [X86-64]
267 Align virtual addresses by clearing slice [14:12] when
268 allocating a VMA at process creation time. This option
269 gives you up to 3% performance improvement on AMD F15h
270 machines (where it is enabled by default) for a
271 CPU-intensive style benchmark, and it can vary highly in
272 a microbenchmark depending on workload and compiler.
274 32: only for 32-bit processes
275 64: only for 64-bit processes
276 on: enable for both 32- and 64-bit processes
277 off: disable for both 32- and 64-bit processes
279 alloc_snapshot [FTRACE]
280 Allocate the ftrace snapshot buffer on boot up when the
281 main buffer is allocated. This is handy if debugging
282 and you need to use tracing_snapshot() on boot up, and
283 do not want to use tracing_snapshot_alloc() as it needs
284 to be done where GFP_KERNEL allocations are allowed.
286 amd_iommu= [HW,X86-64]
287 Pass parameters to the AMD IOMMU driver in the system.
289 fullflush - enable flushing of IO/TLB entries when
290 they are unmapped. Otherwise they are
291 flushed before they will be reused, which
293 off - do not initialize any AMD IOMMU found in
295 force_isolation - Force device isolation for all
296 devices. The IOMMU driver is not
297 allowed anymore to lift isolation
298 requirements as needed. This option
299 does not override iommu=pt
301 amd_iommu_dump= [HW,X86-64]
302 Enable AMD IOMMU driver option to dump the ACPI table
303 for AMD IOMMU. With this option enabled, AMD IOMMU
304 driver will print ACPI tables for AMD IOMMU during
305 IOMMU initialization.
307 amd_iommu_intr= [HW,X86-64]
308 Specifies one of the following AMD IOMMU interrupt
310 legacy - Use legacy interrupt remapping mode.
311 vapic - Use virtual APIC mode, which allows IOMMU
312 to inject interrupts directly into guest.
313 This mode requires kvm-amd.avic=1.
314 (Default when IOMMU HW support is present.)
316 amijoy.map= [HW,JOY] Amiga joystick support
317 Map of devices attached to JOY0DAT and JOY1DAT
319 See also Documentation/input/joydev/joystick.rst
321 analog.map= [HW,JOY] Analog joystick and gamepad support
322 Specifies type or capabilities of an analog joystick
323 connected to one of 16 gameports
324 Format: <type1>,<type2>,..<type16>
327 Power management functions (SPARCstation-4/5 + deriv.)
329 Disable APC CPU standby support. SPARCstation-Fox does
330 not play well with APC CPU idle - disable it if you have
331 APC and your system crashes randomly.
333 apic= [APIC,X86] Advanced Programmable Interrupt Controller
334 Change the output verbosity whilst booting
335 Format: { quiet (default) | verbose | debug }
336 Change the amount of debugging information output
337 when initialising the APIC and IO-APIC components.
338 For X86-32, this can also be used to specify an APIC
340 Format: apic=driver_name
341 Examples: apic=bigsmp
343 apic_extnmi= [APIC,X86] External NMI delivery setting
344 Format: { bsp (default) | all | none }
345 bsp: External NMI is delivered only to CPU 0
346 all: External NMIs are broadcast to all CPUs as a
348 none: External NMI is masked for all CPUs. This is
349 useful so that a dump capture kernel won't be
353 See Documentation/networking/ipv6.txt.
355 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
356 Limit apic dumping. The parameter defines the maximal
357 number of local apics being dumped. Also it is possible
358 to set it to "all" by meaning -- no limit here.
359 Format: { 1 (default) | 2 | ... | all }.
360 The parameter valid if only apic=debug or
361 apic=verbose is specified.
362 Example: apic=debug show_lapic=all
364 apm= [APM] Advanced Power Management
365 See header of arch/x86/kernel/apm_32.c.
367 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
368 Format: <io>,<irq>,<nodeID>
372 atarimouse= [HW,MOUSE] Atari Mouse
374 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
375 EzKey and similar keyboards
377 atkbd.reset= [HW] Reset keyboard during initialization
379 atkbd.set= [HW] Select keyboard code set
380 Format: <int> (2 = AT (default), 3 = PS/2)
382 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
385 atkbd.softraw= [HW] Choose between synthetic and real raw mode
386 Format: <bool> (0 = real, 1 = synthetic (default))
388 atkbd.softrepeat= [HW]
389 Use software keyboard repeat
391 audit= [KNL] Enable the audit sub-system
392 Format: { "0" | "1" | "off" | "on" }
393 0 | off - kernel audit is disabled and can not be
394 enabled until the next reboot
395 unset - kernel audit is initialized but disabled and
396 will be fully enabled by the userspace auditd.
397 1 | on - kernel audit is initialized and partially
398 enabled, storing at most audit_backlog_limit
399 messages in RAM until it is fully enabled by the
403 audit_backlog_limit= [KNL] Set the audit queue size limit.
404 Format: <int> (must be >=0)
407 bau= [X86_UV] Enable the BAU on SGI UV. The default
408 behavior is to disable the BAU (i.e. bau=0).
409 Format: { "0" | "1" }
412 unset - Disable the BAU.
414 baycom_epp= [HW,AX25]
417 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
419 See header of drivers/net/hamradio/baycom_par.c.
421 baycom_ser_fdx= [HW,AX25]
422 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
423 Format: <io>,<irq>,<mode>[,<baud>]
424 See header of drivers/net/hamradio/baycom_ser_fdx.c.
426 baycom_ser_hdx= [HW,AX25]
427 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
428 Format: <io>,<irq>,<mode>
429 See header of drivers/net/hamradio/baycom_ser_hdx.c.
431 blkdevparts= Manual partition parsing of block device(s) for
432 embedded devices based on command line input.
433 See Documentation/block/cmdline-partition.txt
435 boot_delay= Milliseconds to delay each printk during boot.
436 Values larger than 10 seconds (10000) are changed to
440 bootmem_debug [KNL] Enable bootmem allocator debug messages.
443 Disable BERT OS support on buggy BIOSes.
445 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
446 bttv.radio= Most important insmod options are available as
448 bttv.pll= See Documentation/media/v4l-drivers/bttv.rst
451 bulk_remove=off [PPC] This parameter disables the use of the pSeries
452 firmware feature for flushing multiple hpte entries
455 c101= [NET] Moxa C101 synchronous serial card
457 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
458 Sometimes CPU hardware bugs make them report the cache
459 size incorrectly. The kernel will attempt work arounds
460 to fix known problems, but for some CPUs it is not
461 possible to determine what the correct size should be.
462 This option provides an override for these situations.
464 ca_keys= [KEYS] This parameter identifies a specific key(s) on
465 the system trusted keyring to be used for certificate
467 format: { id:<keyid> | builtin }
469 cca= [MIPS] Override the kernel pages' cache coherency
470 algorithm. Accepted values range from 0 to 7
471 inclusive. See arch/mips/include/asm/pgtable-bits.h
472 for platform specific values (SB1, Loongson3 and
475 ccw_timeout_log [S390]
476 See Documentation/s390/CommonIO for details.
478 cgroup_disable= [KNL] Disable a particular controller
479 Format: {name of the controller(s) to disable}
480 The effects of cgroup_disable=foo are:
481 - foo isn't auto-mounted if you mount all cgroups in
483 - foo isn't visible as an individually mountable
485 {Currently only "memory" controller deal with this and
486 cut the overhead, others just disable the usage. So
487 only cgroup_disable=memory is actually worthy}
489 cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1
490 Format: { controller[,controller...] | "all" }
491 Like cgroup_disable, but only applies to cgroup v1;
492 the blacklisted controllers remain available in cgroup2.
494 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
496 nosocket -- Disable socket memory accounting.
497 nokmem -- Disable kernel memory accounting.
499 checkreqprot [SELINUX] Set initial checkreqprot flag value.
500 Format: { "0" | "1" }
501 See security/selinux/Kconfig help text.
502 0 -- check protection applied by kernel (includes
503 any implied execute protection).
504 1 -- check protection requested by application.
505 Default value is set via a kernel config option.
506 Value can be changed at runtime via
507 /selinux/checkreqprot.
510 See Documentation/s390/CommonIO for details.
513 Prevents the clock framework from automatically gating
514 clocks that have not been explicitly enabled by a Linux
515 device driver but are enabled in hardware at reset or
516 by the bootloader/firmware. Note that this does not
517 force such clocks to be always-on nor does it reserve
518 those clocks in any way. This parameter is useful for
519 debug and development, but should not be needed on a
520 platform with proper driver support. For more
521 information, see Documentation/driver-api/clk.rst.
523 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
525 Forces specified clocksource (if available) to be used
526 when calculating gettimeofday(). If specified
527 clocksource is not available, it defaults to PIT.
528 Format: { pit | tsc | cyclone | pmtmr }
530 clocksource= Override the default clocksource
532 Override the default clocksource and use the clocksource
533 with the name specified.
534 Some clocksource names to choose from, depending on
536 [all] jiffies (this is the base, fallback clocksource)
538 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
539 pxa_timer,timer3,32k_counter,timer0_1
540 [X86-32] pit,hpet,tsc;
541 scx200_hrt on Geode; cyclone on IBM x440
549 clocksource.arm_arch_timer.evtstrm=
552 Enable/disable the eventstream feature of the ARM
553 architected timer so that code using WFE-based polling
554 loops can be debugged more effectively on production
557 clearcpuid=BITNUM [X86]
558 Disable CPUID feature X for the kernel. See
559 arch/x86/include/asm/cpufeatures.h for the valid bit
560 numbers. Note the Linux specific bits are not necessarily
561 stable over kernel options, but the vendor specific
563 Also note that user programs calling CPUID directly
564 or using the feature without checking anything
565 will still see it. This just prevents it from
566 being used by the kernel or shown in /proc/cpuinfo.
567 Also note the kernel might malfunction if you disable
570 cma=nn[MG]@[start[MG][-end[MG]]]
572 Sets the size of kernel global memory area for
573 contiguous memory allocations and optionally the
574 placement constraint by the physical address range of
575 memory allocations. A value of 0 disables CMA
576 altogether. For more information, see
577 include/linux/dma-contiguous.h
579 cmo_free_hint= [PPC] Format: { yes | no }
580 Specify whether pages are marked as being inactive
581 when they are freed. This is used in CMO environments
582 to determine OS memory pressure for page stealing by
586 coherent_pool=nn[KMG] [ARM,KNL]
587 Sets the size of memory pool for coherent, atomic dma
588 allocations, by default set to 256K.
590 code_bytes [X86] How many bytes of object code to print
595 com20020= [HW,NET] ARCnet - COM20020 chipset
597 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
599 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
603 ARCnet - COM90xx chipset (memory-mapped buffers)
604 Format: <io>[,<irq>[,<memstart>]]
606 condev= [HW,S390] console device
609 console= [KNL] Output console device and options.
611 tty<n> Use the virtual console device <n>.
615 Use the specified serial port. The options are of
616 the form "bbbbpnf", where "bbbb" is the baud rate,
617 "p" is parity ("n", "o", or "e"), "n" is number of
618 bits, and "f" is flow control ("r" for RTS or
619 omit it). Default is "9600n8".
621 See Documentation/admin-guide/serial-console.rst for more
623 Documentation/networking/netconsole.txt for an
626 uart[8250],io,<addr>[,options]
627 uart[8250],mmio,<addr>[,options]
628 uart[8250],mmio16,<addr>[,options]
629 uart[8250],mmio32,<addr>[,options]
630 uart[8250],0x<addr>[,options]
631 Start an early, polled-mode console on the 8250/16550
632 UART at the specified I/O port or MMIO address,
633 switching to the matching ttyS device later.
634 MMIO inter-register address stride is either 8-bit
635 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
636 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
637 to be equivalent to 'mmio'. 'options' are specified in
638 the same format described for ttyS above; if unspecified,
639 the h/w is not re-initialized.
641 hvc<n> Use the hypervisor console device <n>. This is for
642 both Xen and PowerPC hypervisors.
644 If the device connected to the port is not a TTY but a braille
645 device, prepend "brl," before the device type, for instance
647 For now, only VisioBraille is supported.
650 [KNL] Change console messages format
652 By default we print messages on consoles in
653 "[time stamp] text\n" format (time stamp may not be
654 printed, depending on CONFIG_PRINTK_TIME or
655 `printk_time' param).
657 Switch to syslog format: "<%u>[time stamp] text\n"
658 IOW, each message will have a facility and loglevel
659 prefix. The format is similar to one used by syslog()
660 syscall, or to executing "dmesg -S --raw" or to reading
663 consoleblank= [KNL] The console blank (screen saver) timeout in
664 seconds. A value of 0 disables the blank timer.
668 [KNL] Change the default value for
669 /proc/<pid>/coredump_filter.
670 See also Documentation/filesystems/proc.txt.
672 coresight_cpu_debug.enable
675 Enable/disable the CPU sampling based debugging.
676 0: default value, disable debugging
677 1: enable debugging at boot time
679 cpuidle.off=1 [CPU_IDLE]
680 disable the cpuidle sub-system
682 cpufreq.off=1 [CPU_FREQ]
683 disable the cpufreq sub-system
686 [X86] Delay for N microsec between assert and de-assert
687 of APIC INIT to start processors. This delay occurs
688 on every CPU online, such as boot, and resume from suspend.
691 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
693 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
695 crashkernel=size[KMG][@offset[KMG]]
696 [KNL] Using kexec, Linux can switch to a 'crash kernel'
697 upon panic. This parameter reserves the physical
698 memory region [offset, offset + size] for that kernel
699 image. If '@offset' is omitted, then a suitable offset
700 is selected automatically. Check
701 Documentation/kdump/kdump.txt for further details.
703 crashkernel=range1:size1[,range2:size2,...][@offset]
704 [KNL] Same as above, but depends on the memory
705 in the running system. The syntax of range is
706 start-[end] where start and end are both
707 a memory unit (amount[KMG]). See also
708 Documentation/kdump/kdump.txt for an example.
710 crashkernel=size[KMG],high
711 [KNL, x86_64] range could be above 4G. Allow kernel
712 to allocate physical memory region from top, so could
713 be above 4G if system have more than 4G ram installed.
714 Otherwise memory region will be allocated below 4G, if
716 It will be ignored if crashkernel=X is specified.
717 crashkernel=size[KMG],low
718 [KNL, x86_64] range under 4G. When crashkernel=X,high
719 is passed, kernel could allocate physical memory region
720 above 4G, that cause second kernel crash on system
721 that require some amount of low memory, e.g. swiotlb
722 requires at least 64M+32K low memory, also enough extra
723 low memory is needed to make sure DMA buffers for 32-bit
724 devices won't run out. Kernel would try to allocate at
725 at least 256M below 4G automatically.
726 This one let user to specify own low range under 4G
727 for second kernel instead.
728 0: to disable low allocation.
729 It will be ignored when crashkernel=X,high is not used
730 or memory reserved is below 4G.
733 [KNL] Disable crypto self-tests
738 cs89x0_media= [HW,NET]
739 Format: { rj45 | aui | bnc }
742 See header of drivers/s390/block/dasd_devmap.c.
744 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
745 (one device per port)
746 Format: <port#>,<type>
747 See also Documentation/input/devices/joystick-parport.rst
749 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
751 Documentation/admin-guide/dynamic-debug-howto.rst for
752 details. Deprecated, see dyndbg.
754 debug [KNL] Enable kernel debugging (events log level).
757 [KNL] verbose self-tests
759 Print debugging info while doing the locking API
761 We default to 0 (no extra messages), setting it to
762 1 will print _a lot_ more information - normally
763 only useful to kernel developers.
765 debug_objects [KNL] Enable object debugging
768 [KNL] Disable object debugging
770 debug_guardpage_minorder=
771 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
772 parameter allows control of the order of pages that will
773 be intentionally kept free (and hence protected) by the
774 buddy allocator. Bigger value increase the probability
775 of catching random memory corruption, but reduce the
776 amount of memory for normal system use. The maximum
777 possible value is MAX_ORDER/2. Setting this parameter
778 to 1 or 2 should be enough to identify most random
779 memory corruption problems caused by bugs in kernel or
780 driver code when a CPU writes to (or reads from) a
781 random memory location. Note that there exists a class
782 of memory corruptions problems caused by buggy H/W or
783 F/W or by drivers badly programing DMA (basically when
784 memory is written at bus level and the CPU MMU is
785 bypassed) which are not detectable by
786 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
787 tracking down these problems.
790 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
791 parameter enables the feature at boot time. In
792 default, it is disabled. We can avoid allocating huge
793 chunk of memory for debug pagealloc if we don't enable
794 it at boot time and the system will work mostly same
795 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
796 on: enable the feature
798 debugpat [X86] Enable PAT debugging
800 decnet.addr= [HW,NET]
801 Format: <area>[,<node>]
802 See also Documentation/networking/decnet.txt.
805 [same as hugepagesz=] The size of the default
806 HugeTLB page size. This is the size represented by
807 the legacy /proc/ hugepages APIs, used for SHM, and
808 default size when mounting hugetlbfs filesystems.
809 Defaults to the default architecture's huge page size
813 Set number of hash buckets for dentry cache.
815 disable_1tb_segments [PPC]
816 Disables the use of 1TB hash page table segments. This
817 causes the kernel to fall back to 256MB segments which
818 can be useful when debugging issues that require an SLB
822 See Documentation/networking/ipv6.txt.
825 Disable RADIX MMU mode on POWER9
827 disable_cpu_apicid= [X86,APIC,SMP]
829 The number of initial APIC ID for the
830 corresponding CPU to be disabled at boot,
831 mostly used for the kdump 2nd kernel to
832 disable BSP to wake up multiple CPUs without
833 causing system reset or hang due to sending
836 disable_ddw [PPC/PSERIES]
837 Disable Dynamic DMA Window support. Use this if
838 to workaround buggy firmware.
841 See Documentation/networking/ipv6.txt.
843 disable_mtrr_cleanup [X86]
844 The kernel tries to adjust MTRR layout from continuous
845 to discrete, to make X server driver able to add WB
846 entry later. This parameter disables that.
848 disable_mtrr_trim [X86, Intel and AMD only]
849 By default the kernel will trim any uncacheable
850 memory out of your available memory pool based on
851 MTRR settings. This parameter disables that behavior,
852 possibly causing your machine to run very slowly.
854 disable_timer_pin_1 [X86]
855 Disable PIN 1 of APIC timer
856 Can be useful to work around chipset bugs.
858 dis_ucode_ldr [X86] Disable the microcode loader.
860 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
861 this option disables the debugging code at boot.
863 dma_debug_entries=<number>
864 This option allows to tune the number of preallocated
865 entries for DMA-API debugging code. One entry is
866 required per DMA-API allocation. Use this if the
867 DMA-API debugging code disables itself because the
868 architectural default is too low.
870 dma_debug_driver=<driver_name>
871 With this option the DMA-API debugging driver
872 filter feature can be enabled at boot time. Just
873 pass the driver to filter for as the parameter.
874 The filter can be disabled or changed to another
875 driver later using sysfs.
877 drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
878 Broken monitors, graphic adapters, KVMs and EDIDless
879 panels may send no or incorrect EDID data sets.
880 This parameter allows to specify an EDID data sets
881 in the /lib/firmware directory that are used instead.
882 Generic built-in EDID data sets are used, if one of
883 edid/1024x768.bin, edid/1280x1024.bin,
884 edid/1680x1050.bin, or edid/1920x1080.bin is given
885 and no file with the same name exists. Details and
886 instructions how to build your own EDID data are
887 available in Documentation/EDID/HOWTO.txt. An EDID
888 data set will only be used for a particular connector,
889 if its name and a colon are prepended to the EDID
890 name. Each connector may use a unique EDID data
891 set by separating the files with a comma. An EDID
892 data set with no connector name will be used for
893 any connectors not explicitly specified.
898 Format: {"off" | "known"}
899 Control how the dt_cpu_ftrs device-tree binding is
900 used for CPU feature discovery and setup (if it
902 off: Do not use it, fall back to legacy cpu table.
903 known: Do not pass through unknown features to guests
904 or userspace, only those that the kernel is aware of.
906 dump_apple_properties [X86]
907 Dump name and content of EFI device properties on
908 x86 Macs. Useful for driver authors to determine
909 what data is available or for reverse-engineering.
911 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
912 module.dyndbg[="val"]
913 Enable debug messages at boot time. See
914 Documentation/admin-guide/dynamic-debug-howto.rst
917 nompx [X86] Disables Intel Memory Protection Extensions.
918 See Documentation/x86/intel_mpx.txt for more
919 information about the feature.
921 nopku [X86] Disable Memory Protection Keys CPU feature found
924 module.async_probe [KNL]
925 Enable asynchronous probe on this module.
927 early_ioremap_debug [KNL]
928 Enable debug messages in early_ioremap support. This
929 is useful for tracking down temporary early mappings
930 which are not unmapped.
932 earlycon= [KNL] Output early console device and options.
934 [ARM64] The early console is determined by the
935 stdout-path property in device tree's chosen node,
936 or determined by the ACPI SPCR table.
938 [X86] When used with no options the early console is
939 determined by the ACPI SPCR table.
941 cdns,<addr>[,options]
942 Start an early, polled-mode console on a Cadence
943 (xuartps) serial port at the specified address. Only
944 supported option is baud rate. If baud rate is not
945 specified, the serial port must already be setup and
948 uart[8250],io,<addr>[,options]
949 uart[8250],mmio,<addr>[,options]
950 uart[8250],mmio32,<addr>[,options]
951 uart[8250],mmio32be,<addr>[,options]
952 uart[8250],0x<addr>[,options]
953 Start an early, polled-mode console on the 8250/16550
954 UART at the specified I/O port or MMIO address.
955 MMIO inter-register address stride is either 8-bit
956 (mmio) or 32-bit (mmio32 or mmio32be).
957 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
958 to be equivalent to 'mmio'. 'options' are specified
959 in the same format described for "console=ttyS<n>"; if
960 unspecified, the h/w is not initialized.
964 Start an early, polled-mode console on a pl011 serial
965 port at the specified address. The pl011 serial port
966 must already be setup and configured. Options are not
967 yet supported. If 'mmio32' is specified, then only
968 the driver will use only 32-bit accessors to read/write
969 the device registers.
972 Start an early, polled-mode console on a meson serial
973 port at the specified address. The serial port must
974 already be setup and configured. Options are not yet
978 Start an early, polled-mode console on an msm serial
979 port at the specified address. The serial port
980 must already be setup and configured. Options are not
984 Start an early, polled-mode console on an msm serial
985 dm port at the specified address. The serial port
986 must already be setup and configured. Options are not
990 Start an early, polled-mode console on a serial port
991 of an Actions Semi SoC, such as S500 or S900, at the
992 specified address. The serial port must already be
993 setup and configured. Options are not yet supported.
995 smh Use ARM semihosting calls for early console.
1003 Use early console provided by serial driver available
1004 on Samsung SoCs, requires selecting proper type and
1005 a correct base address of the selected UART port. The
1006 serial port must already be setup and configured.
1007 Options are not yet supported.
1010 Start an early, polled-mode console on a lantiq serial
1011 (lqasc) port at the specified address. The serial port
1012 must already be setup and configured. Options are not
1017 Use early console provided by Freescale LP UART driver
1018 found on Freescale Vybrid and QorIQ LS1021A processors.
1019 A valid base address must be provided, and the serial
1020 port must already be setup and configured.
1023 Start an early, polled-mode console on the
1024 Armada 3700 serial port at the specified
1025 address. The serial port must already be setup
1026 and configured. Options are not yet supported.
1028 earlyprintk= [X86,SH,ARM,M68k,S390]
1033 earlyprintk=serial[,ttySn[,baudrate]]
1034 earlyprintk=serial[,0x...[,baudrate]]
1035 earlyprintk=ttySn[,baudrate]
1036 earlyprintk=dbgp[debugController#]
1037 earlyprintk=pciserial,bus:device.function[,baudrate]
1038 earlyprintk=xdbc[xhciController#]
1040 earlyprintk is useful when the kernel crashes before
1041 the normal console is initialized. It is not enabled by
1042 default because it has some cosmetic problems.
1044 Append ",keep" to not disable it when the real console
1047 Only one of vga, efi, serial, or usb debug port can
1050 Currently only ttyS0 and ttyS1 may be specified by
1051 name. Other I/O ports may be explicitly specified
1052 on some architectures (x86 and arm at least) by
1053 replacing ttySn with an I/O port address, like this:
1054 earlyprintk=serial,0x1008,115200
1055 You can find the port for a given device in
1056 /proc/tty/driver/serial:
1057 2: uart:ST16650V2 port:00001008 irq:18 ...
1059 Interaction with the standard serial driver is not
1062 The VGA and EFI output is eventually overwritten by
1065 The xen output can only be used by Xen PV guests.
1067 The sclp output can only be used on s390.
1069 edac_report= [HW,EDAC] Control how to report EDAC event
1070 Format: {"on" | "off" | "force"}
1071 on: enable EDAC to report H/W event. May be overridden
1072 by other higher priority error reporting module.
1073 off: disable H/W event reporting through EDAC.
1074 force: enforce the use of EDAC to report H/W event.
1077 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1080 This is designed to be used in conjunction with
1081 the boot argument: earlyprintk=vga
1084 Format: {"off" | "on" | "skip[mbr]"}
1087 Format: { "old_map", "nochunk", "noruntime", "debug" }
1088 old_map [X86-64]: switch to the old ioremap-based EFI
1089 runtime services mapping. 32-bit still uses this one by
1091 nochunk: disable reading files in "chunks" in the EFI
1092 boot stub, as chunking can cause problems with some
1093 firmware implementations.
1094 noruntime : disable EFI runtime services support
1095 debug: enable misc debug output
1097 efi_no_storage_paranoia [EFI; X86]
1098 Using this parameter you can use more than 50% of
1099 your efi variable storage. Use this parameter only if
1100 you are really sure that your UEFI does sane gc and
1101 fulfills the spec otherwise your board may brick.
1103 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1104 Add arbitrary attribute to specific memory range by
1105 updating original EFI memory map.
1106 Region of memory which aa attribute is added to is
1108 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1109 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1110 attribute is added to range 0x100000000-0x180000000 and
1111 0x10a0000000-0x1120000000.
1113 Using this parameter you can do debugging of EFI memmap
1114 related feature. For example, you can do debugging of
1115 Address Range Mirroring feature even if your box
1118 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1119 that is to be dynamically loaded by Linux. If there are
1120 multiple variables with the same name but with different
1121 vendor GUIDs, all of them will be loaded. See
1122 Documentation/acpi/ssdt-overlays.txt for details.
1125 eisa_irq_edge= [PARISC,HW]
1126 See header of drivers/parisc/eisa.c.
1129 See comment before function elanfreq_setup() in
1130 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1133 Format: {"cfq" | "deadline" | "noop"}
1134 See Documentation/block/cfq-iosched.txt and
1135 Documentation/block/deadline-iosched.txt for details.
1137 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1138 Specifies physical address of start of kernel core
1139 image elf header and optionally the size. Generally
1140 kexec loader will pass this option to capture kernel.
1141 See Documentation/kdump/kdump.txt for details.
1143 enable_mtrr_cleanup [X86]
1144 The kernel tries to adjust MTRR layout from continuous
1145 to discrete, to make X server driver able to add WB
1146 entry later. This parameter enables that.
1148 enable_timer_pin_1 [X86]
1149 Enable PIN 1 of APIC timer
1150 Can be useful to work around chipset bugs
1151 (in particular on some ATI chipsets).
1152 The kernel tries to set a reasonable default.
1154 enforcing [SELINUX] Set initial enforcing status.
1156 See security/selinux/Kconfig help text.
1157 0 -- permissive (log only, no denials).
1158 1 -- enforcing (deny and log).
1160 Value can be changed at runtime via /selinux/enforce.
1163 Disable Error Record Serialization Table (ERST)
1166 ether= [HW,NET] Ethernet cards parameters
1167 This option is obsoleted by the "netdev=" option, which
1168 has equivalent usage. See its documentation for details.
1172 Permit 'security.evm' to be updated regardless of
1173 current integrity status.
1177 fail_make_request=[KNL]
1178 General fault injection mechanism.
1179 Format: <interval>,<probability>,<space>,<times>
1180 See also Documentation/fault-injection/.
1183 See Documentation/blockdev/floppy.txt.
1185 force_pal_cache_flush
1186 [IA-64] Avoid check_sal_cache_flush which may hang on
1187 buggy SAL_CACHE_FLUSH implementations. Using this
1188 parameter will force ia64_sal_cache_flush to call
1189 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1192 Forcefully enable Physical Address Extension (PAE).
1193 Many Pentium M systems disable PAE but may have a
1194 functionally usable PAE implementation.
1195 Warning: use of this parameter will taint the kernel
1196 and may cause unknown problems.
1199 [FTRACE] will set and start the specified tracer
1200 as early as possible in order to facilitate early
1203 ftrace_dump_on_oops[=orig_cpu]
1204 [FTRACE] will dump the trace buffers on oops.
1205 If no parameter is passed, ftrace will dump
1206 buffers of all CPUs, but if you pass orig_cpu, it will
1207 dump only the buffer of the CPU that triggered the
1210 ftrace_filter=[function-list]
1211 [FTRACE] Limit the functions traced by the function
1212 tracer at boot up. function-list is a comma separated
1213 list of functions. This list can be changed at run
1214 time by the set_ftrace_filter file in the debugfs
1217 ftrace_notrace=[function-list]
1218 [FTRACE] Do not trace the functions specified in
1219 function-list. This list can be changed at run time
1220 by the set_ftrace_notrace file in the debugfs
1223 ftrace_graph_filter=[function-list]
1224 [FTRACE] Limit the top level callers functions traced
1225 by the function graph tracer at boot up.
1226 function-list is a comma separated list of functions
1227 that can be changed at run time by the
1228 set_graph_function file in the debugfs tracing directory.
1230 ftrace_graph_notrace=[function-list]
1231 [FTRACE] Do not trace from the functions specified in
1232 function-list. This list is a comma separated list of
1233 functions that can be changed at run time by the
1234 set_graph_notrace file in the debugfs tracing directory.
1236 ftrace_graph_max_depth=<uint>
1237 [FTRACE] Used with the function graph tracer. This is
1238 the max depth it will trace into a function. This value
1239 can be changed at run time by the max_graph_depth file
1240 in the tracefs tracing directory. default: 0 (no limit)
1243 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1244 support via parallel port (up to 5 devices per port)
1245 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1246 See also Documentation/input/devices/joystick-parport.rst
1250 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1254 gcov_persist= [GCOV] When non-zero (default), profiling data for
1255 kernel modules is saved and remains accessible via
1256 debugfs, even when the module is unloaded/reloaded.
1257 When zero, profiling data is discarded and associated
1258 debugfs files are removed at module unload time.
1260 goldfish [X86] Enable the goldfish android emulator platform.
1261 Don't use this when you are not running on the
1264 gpt [EFI] Forces disk with valid GPT signature but
1265 invalid Protective MBR to be treated as GPT. If the
1266 primary GPT is corrupted, it enables the backup/alternate
1267 GPT to be used instead.
1269 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1270 the "Enable 0" bit of the configuration register.
1273 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1274 the "Enable 0" bit of the configuration register.
1277 grcan.select= [HW] Select which physical interface to use.
1280 grcan.txsize= [HW] Sets the size of the tx buffer.
1281 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1283 grcan.rxsize= [HW] Sets the size of the rx buffer.
1284 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1287 gpio-mockup.gpio_mockup_ranges
1288 [HW] Sets the ranges of gpiochip of for this device.
1289 Format: <start1>,<end1>,<start2>,<end2>...
1291 hardlockup_all_cpu_backtrace=
1292 [KNL] Should the hard-lockup detector generate
1293 backtraces on all cpus.
1296 hashdist= [KNL,NUMA] Large hashes allocated during boot
1297 are distributed across NUMA nodes. Defaults on
1298 for 64-bit NUMA, off otherwise.
1299 Format: 0 | 1 (for off | on)
1301 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1303 hd= [EIDE] (E)IDE hard drive subsystem geometry
1304 Format: <cyl>,<head>,<sect>
1307 Disable Hardware Error Source Table (HEST) support;
1308 corresponding firmware-first mode error processing
1309 logic will be disabled.
1311 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1312 size of <nn>. This works even on boxes that have no
1313 highmem otherwise. This also works to reduce highmem
1314 size on bigger boxes.
1316 highres= [KNL] Enable/disable high resolution timer mode.
1317 Valid parameters: "on", "off"
1321 See Documentation/isdn/README.HiSax.
1325 hpet= [X86-32,HPET] option to control HPET usage
1326 Format: { enable (default) | disable | force |
1328 disable: disable HPET and use PIT instead
1329 force: allow force enabled of undocumented chips (ICH4,
1331 verbose: show contents of HPET registers during setup
1333 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1334 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1336 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1337 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1338 On x86-64 and powerpc, this option can be specified
1339 multiple times interleaved with hugepages= to reserve
1340 huge pages of different sizes. Valid pages sizes on
1341 x86-64 are 2M (when the CPU supports "pse") and 1G
1342 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1345 [KNL] Should the hung task detector generate panics.
1348 A nonzero value instructs the kernel to panic when a
1349 hung task is detected. The default value is controlled
1350 by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1351 option. The value selected by this boot parameter can
1352 be changed later by the kernel.hung_task_panic sysctl.
1354 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1355 terminal devices. Valid values: 0..8
1356 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1357 If specified, z/VM IUCV HVC accepts connections
1358 from listed z/VM user IDs only.
1360 Do not unregister boot console at start. This is only
1361 useful for debugging when something happens in the window
1362 between unregistering the boot console and initializing
1365 i2c_bus= [HW] Override the default board specific I2C bus speed
1366 or register an additional I2C bus that is not
1367 registered from board initialization code.
1371 i8042.debug [HW] Toggle i8042 debug mode
1372 i8042.unmask_kbd_data
1373 [HW] Enable printing of interrupt data from the KBD port
1374 (disabled by default, and as a pre-condition
1375 requires that i8042.debug=1 be enabled)
1376 i8042.direct [HW] Put keyboard port into non-translated mode
1377 i8042.dumbkbd [HW] Pretend that controller can only read data from
1378 keyboard and cannot control its state
1379 (Don't attempt to blink the leds)
1380 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1381 i8042.nokbd [HW] Don't check/create keyboard port
1382 i8042.noloop [HW] Disable the AUX Loopback command while probing
1384 i8042.nomux [HW] Don't check presence of an active multiplexing
1386 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1388 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1389 i8042.reset [HW] Reset the controller during init, cleanup and
1390 suspend-to-ram transitions, only during s2r
1391 transitions, or never reset
1392 Format: { 1 | Y | y | 0 | N | n }
1393 1, Y, y: always reset controller
1394 0, N, n: don't ever reset controller
1395 Default: only on s2r transitions on x86; most other
1396 architectures force reset to be always executed
1397 i8042.unlock [HW] Unlock (ignore) the keylock
1398 i8042.kbdreset [HW] Reset device connected to KBD port
1402 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1403 indicates that the driver is running on unsupported
1405 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1406 does not match list of supported models.
1408 [HW] Report power status in /proc/i8k
1409 (disabled by default)
1410 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1413 i915.invert_brightness=
1414 [DRM] Invert the sense of the variable that is used to
1415 set the brightness of the panel backlight. Normally a
1416 brightness value of 0 indicates backlight switched off,
1417 and the maximum of the brightness value sets the backlight
1418 to maximum brightness. If this parameter is set to 0
1419 (default) and the machine requires it, or this parameter
1420 is set to 1, a brightness value of 0 sets the backlight
1421 to maximum brightness, and the maximum of the brightness
1422 value switches the backlight off.
1423 -1 -- never invert brightness
1424 0 -- machine default
1425 1 -- force brightness inversion
1428 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1430 ide-core.nodma= [HW] (E)IDE subsystem
1431 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1432 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1433 .cdrom .chs .ignore_cable are additional options
1434 See Documentation/ide/ide.txt.
1436 ide-generic.probe-mask= [HW] (E)IDE subsystem
1438 Probe mask for legacy ISA IDE ports. Depending on
1439 platform up to 6 ports are supported, enabled by
1440 setting corresponding bits in the mask to 1. The
1441 default value is 0x0, which has a special meaning.
1442 On systems that have PCI, it triggers scanning the
1443 PCI bus for the first and the second port, which
1444 are then probed. On systems without PCI the value
1445 of 0x0 enables probing the two first ports as if it
1448 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1449 Claim all unknown PCI IDE storage controllers.
1452 Format: idle=poll, idle=halt, idle=nomwait
1453 Poll forces a polling idle loop that can slightly
1454 improve the performance of waking up a idle CPU, but
1455 will use a lot of power and make the system run hot.
1457 idle=halt: Halt is forced to be used for CPU idle.
1458 In such case C2/C3 won't be used again.
1459 idle=nomwait: Disable mwait for CPU C-states
1461 ieee754= [MIPS] Select IEEE Std 754 conformance mode
1462 Format: { strict | legacy | 2008 | relaxed }
1465 Choose which programs will be accepted for execution
1466 based on the IEEE 754 NaN encoding(s) supported by
1467 the FPU and the NaN encoding requested with the value
1468 of an ELF file header flag individually set by each
1469 binary. Hardware implementations are permitted to
1470 support either or both of the legacy and the 2008 NaN
1473 Available settings are as follows:
1474 strict accept binaries that request a NaN encoding
1475 supported by the FPU
1476 legacy only accept legacy-NaN binaries, if supported
1478 2008 only accept 2008-NaN binaries, if supported
1480 relaxed accept any binaries regardless of whether
1481 supported by the FPU
1483 The FPU emulator is always able to support both NaN
1484 encodings, so if no FPU hardware is present or it has
1485 been disabled with 'nofpu', then the settings of
1486 'legacy' and '2008' strap the emulator accordingly,
1487 'relaxed' straps the emulator for both legacy-NaN and
1488 2008-NaN, whereas 'strict' enables legacy-NaN only on
1489 legacy processors and both NaN encodings on MIPS32 or
1492 The setting for ABS.fmt/NEG.fmt instruction execution
1493 mode generally follows that for the NaN encoding,
1494 except where unsupported by hardware.
1496 ignore_loglevel [KNL]
1497 Ignore loglevel setting - this will print /all/
1498 kernel messages to the console. Useful for debugging.
1499 We also add it as printk module parameter, so users
1500 could change it dynamically, usually by
1501 /sys/module/printk/parameters/ignore_loglevel.
1504 Ignore RLIMIT_DATA setting for data mappings,
1505 print warning at first misuse. Can be changed via
1506 /sys/module/kernel/parameters/ignore_rlimit_data.
1508 ihash_entries= [KNL]
1509 Set number of hash buckets for inode cache.
1511 ima_appraise= [IMA] appraise integrity measurements
1512 Format: { "off" | "enforce" | "fix" | "log" }
1515 ima_appraise_tcb [IMA]
1516 The builtin appraise policy appraises all files
1519 ima_canonical_fmt [IMA]
1520 Use the canonical format for the binary runtime
1521 measurements, instead of host native format.
1524 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1528 The list of supported hash algorithms is defined
1529 in crypto/hash_info.h.
1532 The builtin policies to load during IMA setup.
1533 Format: "tcb | appraise_tcb | secure_boot |
1536 The "tcb" policy measures all programs exec'd, files
1537 mmap'd for exec, and all files opened with the read
1538 mode bit set by either the effective uid (euid=0) or
1541 The "appraise_tcb" policy appraises the integrity of
1542 all files owned by root. (This is the equivalent
1543 of ima_appraise_tcb.)
1545 The "secure_boot" policy appraises the integrity
1546 of files (eg. kexec kernel image, kernel modules,
1547 firmware, policy, etc) based on file signatures.
1549 The "fail_securely" policy forces file signature
1550 verification failure also on privileged mounted
1551 filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
1554 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1555 Load a policy which meets the needs of the Trusted
1556 Computing Base. This means IMA will measure all
1557 programs exec'd, files mmap'd for exec, and all files
1558 opened for read by uid=0.
1561 Select one of defined IMA measurements template formats.
1562 Formats: { "ima" | "ima-ng" | "ima-sig" }
1566 [IMA] Define a custom template format.
1567 Format: { "field1|...|fieldN" }
1569 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1570 Format: <min_file_size>
1571 Set the minimal file size for using asynchronous hash.
1572 If left unspecified, ahash usage is disabled.
1574 ahash performance varies for different data sizes on
1575 different crypto accelerators. This option can be used
1576 to achieve the best performance for a particular HW.
1578 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1580 Set hashing buffer size. Default: 4k.
1582 ahash performance varies for different chunk sizes on
1583 different crypto accelerators. This option can be used
1584 to achieve best performance for particular HW.
1588 Run specified binary instead of /sbin/init as init
1591 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1592 for working out where the kernel is dying during
1595 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1596 initcall functions. Useful for debugging built-in
1597 modules and initcalls.
1599 initrd= [BOOT] Specify the location of the initial ramdisk
1601 init_pkru= [x86] Specify the default memory protection keys rights
1602 register contents for all processes. 0x55555554 by
1603 default (disallow access to all but pkey 0). Can
1604 override in debugfs after boot.
1606 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1609 int_pln_enable [x86] Enable power limit notification interrupt
1611 integrity_audit=[IMA]
1612 Format: { "0" | "1" }
1613 0 -- basic integrity auditing messages. (Default)
1614 1 -- additional integrity auditing messages.
1616 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1618 Enable intel iommu driver.
1620 Disable intel iommu driver.
1621 igfx_off [Default Off]
1622 By default, gfx is mapped as normal device. If a gfx
1623 device has a dedicated DMAR unit, the DMAR unit is
1624 bypassed by not enabling DMAR with this option. In
1625 this case, gfx device will use physical address for
1628 With this option iommu will not optimize to look
1629 for io virtual address below 32-bit forcing dual
1630 address cycle on pci bus for cards supporting greater
1631 than 32-bit addressing. The default is to look
1632 for translation below 32-bit and if not available
1633 then look in the higher range.
1634 strict [Default Off]
1635 With this option on every unmap_single operation will
1636 result in a hardware IOTLB flush operation as opposed
1637 to batching them for performance.
1638 sp_off [Default Off]
1639 By default, super page will be supported if Intel IOMMU
1640 has the capability. With this option, super page will
1642 ecs_off [Default Off]
1643 By default, extended context tables will be supported if
1644 the hardware advertises that it has support both for the
1645 extended tables themselves, and also PASID support. With
1646 this option set, extended tables will not be used even
1647 on hardware which claims to support them.
1648 tboot_noforce [Default Off]
1649 Do not force the Intel IOMMU enabled under tboot.
1650 By default, tboot will force Intel IOMMU on, which
1651 could harm performance of some high-throughput
1652 devices like 40GBit network cards, even if identity
1654 Note that using this option lowers the security
1655 provided by tboot because it makes the system
1656 vulnerable to DMA attacks.
1658 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1659 0 disables intel_idle and fall back on acpi_idle.
1660 1 to 9 specify maximum depth of C-state.
1664 Do not enable intel_pstate as the default
1665 scaling driver for the supported processors
1667 Use intel_pstate as a scaling driver, but configure it
1668 to work with generic cpufreq governors (instead of
1669 enabling its internal governor). This mode cannot be
1670 used along with the hardware-managed P-states (HWP)
1673 Enable intel_pstate on systems that prohibit it by default
1674 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1675 instead of acpi-cpufreq may disable platform features, such
1676 as thermal controls and power capping, that rely on ACPI
1677 P-States information being indicated to OSPM and therefore
1678 should be used with caution. This option does not work with
1679 processors that aren't supported by the intel_pstate driver
1680 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1682 Do not enable hardware P state control (HWP)
1685 Only load intel_pstate on systems which support
1686 hardware P state control (HWP) if available.
1688 Enforce ACPI _PPC performance limits. If the Fixed ACPI
1689 Description Table, specifies preferred power management
1690 profile as "Enterprise Server" or "Performance Server",
1691 then this feature is turned on by default.
1693 Allow per-logical-CPU P-State performance control limits using
1694 cpufreq sysfs interface
1696 intremap= [X86-64, Intel-IOMMU]
1697 on enable Interrupt Remapping (default)
1698 off disable Interrupt Remapping
1699 nosid disable Source ID checking
1701 BIOS x2APIC opt-out request will be ignored
1702 nopost disable Interrupt Posting
1704 iomem= Disable strict checking of access to MMIO memory
1705 strict regions from userspace.
1719 nobypass [PPC/POWERNV]
1720 Disable IOMMU bypass, using IOMMU for PCI devices.
1723 [ARM64] Configure DMA to bypass the IOMMU by default.
1724 Format: { "0" | "1" }
1725 0 - Use IOMMU translation for DMA.
1726 1 - Bypass the IOMMU for DMA.
1727 unset - Use IOMMU translation for DMA.
1729 io7= [HW] IO7 for Marvel based alpha systems
1730 See comment before marvel_specify_io7 in
1731 arch/alpha/kernel/core_marvel.c.
1733 io_delay= [X86] I/O delay method
1735 Standard port 0x80 based delay
1737 Alternate port 0xed based delay (needed on some systems)
1739 Simple two microseconds delay
1744 See Documentation/filesystems/nfs/nfsroot.txt.
1746 irqaffinity= [SMP] Set the default irq affinity mask
1747 The argument is a cpu list, as described above.
1749 irqchip.gicv2_force_probe=
1752 Force the kernel to look for the second 4kB page
1753 of a GICv2 controller even if the memory range
1754 exposed by the device tree is too small.
1756 irqchip.gicv3_nolpi=
1758 Force the kernel to ignore the availability of
1759 LPIs (and by consequence ITSs). Intended for system
1760 that use the kernel as a bootloader, and thus want
1761 to let secondary kernels in charge of setting up
1765 When an interrupt is not handled search all handlers
1766 for it. Intended to get systems with badly broken
1770 When an interrupt is not handled search all handlers
1771 for it. Also check all handlers each timer
1772 interrupt. Intended to get systems with badly broken
1776 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1778 isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
1779 [Deprecated - use cpusets instead]
1780 Format: [flag-list,]<cpu-list>
1782 Specify one or more CPUs to isolate from disturbances
1783 specified in the flag list (default: domain):
1786 Disable the tick when a single task runs.
1788 A residual 1Hz tick is offloaded to workqueues, which you
1789 need to affine to housekeeping through the global
1790 workqueue's affinity configured via the
1791 /sys/devices/virtual/workqueue/cpumask sysfs file, or
1792 by using the 'domain' flag described below.
1794 NOTE: by default the global workqueue runs on all CPUs,
1795 so to protect individual CPUs the 'cpumask' file has to
1796 be configured manually after bootup.
1799 Isolate from the general SMP balancing and scheduling
1800 algorithms. Note that performing domain isolation this way
1801 is irreversible: it's not possible to bring back a CPU to
1802 the domains once isolated through isolcpus. It's strongly
1803 advised to use cpusets instead to disable scheduler load
1804 balancing through the "cpuset.sched_load_balance" file.
1805 It offers a much more flexible interface where CPUs can
1806 move in and out of an isolated set anytime.
1808 You can move a process onto or off an "isolated" CPU via
1809 the CPU affinity syscalls or cpuset.
1810 <cpu number> begins at 0 and the maximum value is
1811 "number of CPUs in system - 1".
1813 The format of <cpu-list> is described above.
1819 ivrs_ioapic [HW,X86_64]
1820 Provide an override to the IOAPIC-ID<->DEVICE-ID
1821 mapping provided in the IVRS ACPI table. For
1822 example, to map IOAPIC-ID decimal 10 to
1823 PCI device 00:14.0 write the parameter as:
1824 ivrs_ioapic[10]=00:14.0
1826 ivrs_hpet [HW,X86_64]
1827 Provide an override to the HPET-ID<->DEVICE-ID
1828 mapping provided in the IVRS ACPI table. For
1829 example, to map HPET-ID decimal 0 to
1830 PCI device 00:14.0 write the parameter as:
1831 ivrs_hpet[0]=00:14.0
1833 ivrs_acpihid [HW,X86_64]
1834 Provide an override to the ACPI-HID:UID<->DEVICE-ID
1835 mapping provided in the IVRS ACPI table. For
1836 example, to map UART-HID:UID AMD0020:0 to
1837 PCI device 00:14.5 write the parameter as:
1838 ivrs_acpihid[00:14.5]=AMD0020:0
1840 js= [HW,JOY] Analog joystick
1841 See Documentation/input/joydev/joystick.rst.
1844 When CONFIG_RANDOMIZE_BASE is set, this disables
1845 kernel and module base offset ASLR (Address Space
1846 Layout Randomization).
1849 [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
1850 report on every invalid memory access. Without this
1851 parameter KASAN will print report only for the first
1856 kernelcore= [KNL,X86,IA-64,PPC]
1857 Format: nn[KMGTPE] | nn% | "mirror"
1858 This parameter specifies the amount of memory usable by
1859 the kernel for non-movable allocations. The requested
1860 amount is spread evenly throughout all nodes in the
1861 system as ZONE_NORMAL. The remaining memory is used for
1862 movable memory in its own zone, ZONE_MOVABLE. In the
1863 event, a node is too small to have both ZONE_NORMAL and
1864 ZONE_MOVABLE, kernelcore memory will take priority and
1865 other nodes will have a larger ZONE_MOVABLE.
1867 ZONE_MOVABLE is used for the allocation of pages that
1868 may be reclaimed or moved by the page migration
1869 subsystem. Note that allocations like PTEs-from-HighMem
1870 still use the HighMem zone if it exists, and the Normal
1871 zone if it does not.
1873 It is possible to specify the exact amount of memory in
1874 the form of "nn[KMGTPE]", a percentage of total system
1875 memory in the form of "nn%", or "mirror". If "mirror"
1876 option is specified, mirrored (reliable) memory is used
1877 for non-movable allocations and remaining memory is used
1878 for Movable pages. "nn[KMGTPE]", "nn%", and "mirror"
1879 are exclusive, so you cannot specify multiple forms.
1881 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1882 Format: <Controller#>[,poll interval]
1883 The controller # is the number of the ehci usb debug
1884 port as it is probed via PCI. The poll interval is
1885 optional and is the number seconds in between
1886 each poll cycle to the debug port in case you need
1887 the functionality for interrupting the kernel with
1888 gdb or control-c on the dbgp connection. When
1889 not using this parameter you use sysrq-g to break into
1890 the kernel debugger.
1892 kgdboc= [KGDB,HW] kgdb over consoles.
1893 Requires a tty driver that supports console polling,
1894 or a supported polling keyboard driver (non-usb).
1895 Serial only format: <serial_device>[,baud]
1896 keyboard only format: kbd
1897 keyboard and serial format: kbd,<serial_device>[,baud]
1898 Optional Kernel mode setting:
1899 kms, kbd format: kms,kbd
1900 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1902 kgdbwait [KGDB] Stop kernel execution and enter the
1903 kernel debugger at the earliest opportunity.
1905 kmac= [MIPS] korina ethernet MAC address.
1906 Configure the RouterBoard 532 series on-chip
1907 Ethernet adapter MAC address.
1909 kmemleak= [KNL] Boot-time kmemleak enable/disable
1910 Valid arguments: on, off
1912 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1915 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1916 Default is 0 (don't ignore, but inject #GP)
1918 kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
1919 Default is false (don't support).
1921 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1925 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1926 Default is 1 (enabled)
1928 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1930 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1932 kvm-arm.vgic_v3_group0_trap=
1933 [KVM,ARM] Trap guest accesses to GICv3 group-0
1936 kvm-arm.vgic_v3_group1_trap=
1937 [KVM,ARM] Trap guest accesses to GICv3 group-1
1940 kvm-arm.vgic_v3_common_trap=
1941 [KVM,ARM] Trap guest accesses to GICv3 common
1944 kvm-arm.vgic_v4_enable=
1945 [KVM,ARM] Allow use of GICv4 for direct injection of
1948 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1949 (virtualized MMU) support on capable Intel chips.
1950 Default is 1 (enabled)
1952 kvm-intel.emulate_invalid_guest_state=
1953 [KVM,Intel] Enable emulation of invalid guest states
1954 Default is 0 (disabled)
1956 kvm-intel.flexpriority=
1957 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1958 Default is 1 (enabled)
1961 [KVM,Intel] Enable VMX nesting (nVMX).
1962 Default is 0 (disabled)
1964 kvm-intel.unrestricted_guest=
1965 [KVM,Intel] Disable unrestricted guest feature
1966 (virtualized real and unpaged mode) on capable
1967 Intel chips. Default is 1 (enabled)
1969 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1970 feature (tagged TLBs) on capable Intel chips.
1971 Default is 1 (enabled)
1977 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1980 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1981 value for LAPIC timer one-shot implementation. Default
1982 back to the programmable timer unit in the LAPIC.
1984 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1987 libata.dma= [LIBATA] DMA control
1988 libata.dma=0 Disable all PATA and SATA DMA
1989 libata.dma=1 PATA and SATA Disk DMA only
1990 libata.dma=2 ATAPI (CDROM) DMA only
1991 libata.dma=4 Compact Flash DMA only
1992 Combinations also work, so libata.dma=3 enables DMA
1993 for disks and CDROMs, but not CFs.
1995 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1996 libata.ignore_hpa=0 keep BIOS limits (default)
1997 libata.ignore_hpa=1 ignore limits, using full disk
1999 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
2003 libata.force= [LIBATA] Force configurations. The format is comma
2004 separated list of "[ID:]VAL" where ID is
2005 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
2006 matching port, link or device. Basically, it matches
2007 the ATA ID string printed on console by libata. If
2008 the whole ID part is omitted, the last PORT and DEVICE
2009 values are used. If ID hasn't been specified yet, the
2010 configuration applies to all ports, links and devices.
2012 If only DEVICE is omitted, the parameter applies to
2013 the port and all links and devices behind it. DEVICE
2014 number of 0 either selects the first device or the
2015 first fan-out link behind PMP device. It does not
2016 select the host link. DEVICE number of 15 selects the
2017 host link and device attached to it.
2019 The VAL specifies the configuration to force. As long
2020 as there's no ambiguity shortcut notation is allowed.
2021 For example, both 1.5 and 1.5G would work for 1.5Gbps.
2022 The following configurations can be forced.
2024 * Cable type: 40c, 80c, short40c, unk, ign or sata.
2025 Any ID with matching PORT is used.
2027 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
2029 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2030 udma[/][16,25,33,44,66,100,133] notation is also
2033 * [no]ncq: Turn on or off NCQ.
2035 * [no]ncqtrim: Turn off queued DSM TRIM.
2037 * nohrst, nosrst, norst: suppress hard, soft
2040 * rstonce: only attempt one reset during
2041 hot-unplug link recovery
2043 * dump_id: dump IDENTIFY data.
2045 * atapi_dmadir: Enable ATAPI DMADIR bridge support
2047 * disable: Disable this device.
2049 If there are multiple matching configurations changing
2050 the same attribute, the last one is used.
2052 memblock=debug [KNL] Enable memblock debug messages.
2054 load_ramdisk= [RAM] List of ramdisks to load from floppy
2055 See Documentation/blockdev/ramdisk.txt.
2057 lockd.nlm_grace_period=P [NFS] Assign grace period.
2060 lockd.nlm_tcpport=N [NFS] Assign TCP port.
2063 lockd.nlm_timeout=T [NFS] Assign timeout value.
2066 lockd.nlm_udpport=M [NFS] Assign UDP port.
2069 locktorture.nreaders_stress= [KNL]
2070 Set the number of locking read-acquisition kthreads.
2071 Defaults to being automatically set based on the
2072 number of online CPUs.
2074 locktorture.nwriters_stress= [KNL]
2075 Set the number of locking write-acquisition kthreads.
2077 locktorture.onoff_holdoff= [KNL]
2078 Set time (s) after boot for CPU-hotplug testing.
2080 locktorture.onoff_interval= [KNL]
2081 Set time (s) between CPU-hotplug operations, or
2082 zero to disable CPU-hotplug testing.
2084 locktorture.shuffle_interval= [KNL]
2085 Set task-shuffle interval (jiffies). Shuffling
2086 tasks allows some CPUs to go into dyntick-idle
2087 mode during the locktorture test.
2089 locktorture.shutdown_secs= [KNL]
2090 Set time (s) after boot system shutdown. This
2091 is useful for hands-off automated testing.
2093 locktorture.stat_interval= [KNL]
2094 Time (s) between statistics printk()s.
2096 locktorture.stutter= [KNL]
2097 Time (s) to stutter testing, for example,
2098 specifying five seconds causes the test to run for
2099 five seconds, wait for five seconds, and so on.
2100 This tests the locking primitive's ability to
2101 transition abruptly to and from idle.
2103 locktorture.torture_type= [KNL]
2104 Specify the locking implementation to test.
2106 locktorture.verbose= [KNL]
2107 Enable additional printk() statements.
2109 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
2112 loglevel= All Kernel Messages with a loglevel smaller than the
2113 console loglevel will be printed to the console. It can
2114 also be changed with klogd or other programs. The
2115 loglevels are defined as follows:
2117 0 (KERN_EMERG) system is unusable
2118 1 (KERN_ALERT) action must be taken immediately
2119 2 (KERN_CRIT) critical conditions
2120 3 (KERN_ERR) error conditions
2121 4 (KERN_WARNING) warning conditions
2122 5 (KERN_NOTICE) normal but significant condition
2123 6 (KERN_INFO) informational
2124 7 (KERN_DEBUG) debug-level messages
2126 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
2127 in bytes. n must be a power of two and greater
2128 than the minimal size. The minimal size is defined
2129 by LOG_BUF_SHIFT kernel config parameter. There is
2130 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
2131 that allows to increase the default size depending on
2132 the number of CPUs. See init/Kconfig for more details.
2134 logo.nologo [FB] Disables display of the built-in Linux logo.
2135 This may be used to provide more screen space for
2136 kernel log messages and is useful when debugging
2137 kernel boot problems.
2139 lp=0 [LP] Specify parallel ports to use, e.g,
2140 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
2141 lp=reset first parallel port). 'lp=0' disables the
2142 lp=auto printer driver. 'lp=reset' (which can be
2143 specified in addition to the ports) causes
2144 attached printers to be reset. Using
2145 lp=port1,port2,... specifies the parallel ports
2146 to associate lp devices with, starting with
2147 lp0. A port specification may be 'none' to skip
2148 that lp device, or a parport name such as
2149 'parport0'. Specifying 'lp=auto' instead of a
2150 port specification list means that device IDs
2151 from each port should be examined, to see if
2152 an IEEE 1284-compliant printer is attached; if
2153 so, the driver will manage that printer.
2154 See also header of drivers/char/lp.c.
2157 Sets loops_per_jiffy to given constant, thus avoiding
2158 time-consuming boot-time autodetection (up to 250 ms per
2159 CPU). 0 enables autodetection (default). To determine
2160 the correct value for your kernel, boot with normal
2161 autodetection and see what value is printed. Note that
2162 on SMP systems the preset will be applied to all CPUs,
2163 which is likely to cause problems if your CPUs need
2164 significantly divergent settings. An incorrect value
2165 will cause delays in the kernel to be wrong, leading to
2166 unpredictable I/O errors and other breakage. Although
2167 unlikely, in the extreme case this might damage your
2171 Format: <io>,<irq>,<dma>
2173 machvec= [IA-64] Force the use of a particular machine-vector
2174 (machvec) in a generic kernel.
2175 Example: machvec=hpzx1_swiotlb
2177 machtype= [Loongson] Share the same kernel image file between different
2179 Example: machtype=lemote-yeeloong-2f-7inch
2181 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2182 than or equal to this physical address is ignored.
2184 maxcpus= [SMP] Maximum number of processors that an SMP kernel
2185 will bring up during bootup. maxcpus=n : n >= 0 limits
2186 the kernel to bring up 'n' processors. Surely after
2187 bootup you can bring up the other plugged cpu by executing
2188 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
2189 only takes effect during system bootup.
2190 While n=0 is a special case, it is equivalent to "nosmp",
2191 which also disables the IO APIC.
2193 max_loop= [LOOP] The number of loop block devices that get
2194 (loop.max_loop) unconditionally pre-created at init time. The default
2195 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2196 of statically allocating a predefined number, loop
2197 devices can be requested on-demand with the
2198 /dev/loop-control interface.
2200 mce [X86-32] Machine Check Exception
2202 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2204 md= [HW] RAID subsystems devices and level
2205 See Documentation/admin-guide/md.rst.
2208 Format: <first>,<last>
2209 Specifies range of consoles to be captured by the MDA.
2211 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2212 Amount of memory to be used when the kernel is not able
2213 to see the whole system memory or for test.
2214 [X86] Work as limiting max address. Use together
2215 with memmap= to avoid physical address space collisions.
2216 Without memmap= PCI devices could be placed at addresses
2217 belonging to unused RAM.
2219 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2223 [KNL,SH] Allow user to override the default size for
2224 per-device physically contiguous DMA buffers.
2226 memhp_default_state=online/offline
2227 [KNL] Set the initial state for the memory hotplug
2228 onlining policy. If not specified, the default value is
2229 set according to the
2230 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
2232 See Documentation/memory-hotplug.txt.
2234 memmap=exactmap [KNL,X86] Enable setting of an exact
2235 E820 memory map, as specified by the user.
2236 Such memmap=exactmap lines can be constructed based on
2237 BIOS output or other requirements. See the memmap=nn@ss
2240 memmap=nn[KMG]@ss[KMG]
2241 [KNL] Force usage of a specific region of memory.
2242 Region of memory to be used is from ss to ss+nn.
2243 If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
2244 which limits max address to nn[KMG].
2245 Multiple different regions can be specified,
2248 memmap=100M@2G,100M#3G,1G!1024G
2250 memmap=nn[KMG]#ss[KMG]
2251 [KNL,ACPI] Mark specific memory as ACPI data.
2252 Region of memory to be marked is from ss to ss+nn.
2254 memmap=nn[KMG]$ss[KMG]
2255 [KNL,ACPI] Mark specific memory as reserved.
2256 Region of memory to be reserved is from ss to ss+nn.
2257 Example: Exclude memory from 0x18690000-0x1869ffff
2258 memmap=64K$0x18690000
2260 memmap=0x10000$0x18690000
2261 Some bootloaders may need an escape character before '$',
2262 like Grub2, otherwise '$' and the following number
2265 memmap=nn[KMG]!ss[KMG]
2266 [KNL,X86] Mark specific memory as protected.
2267 Region of memory to be used, from ss to ss+nn.
2268 The memory region may be marked as e820 type 12 (0xc)
2269 and is NVDIMM or ADR memory.
2271 memmap=<size>%<offset>-<oldtype>+<newtype>
2272 [KNL,ACPI] Convert memory within the specified region
2273 from <oldtype> to <newtype>. If "-<oldtype>" is left
2274 out, the whole region will be marked as <newtype>,
2275 even if previously unavailable. If "+<newtype>" is left
2276 out, matching memory will be removed. Types are
2277 specified as e820 types, e.g., 1 = RAM, 2 = reserved,
2278 3 = ACPI, 12 = PRAM.
2280 memory_corruption_check=0/1 [X86]
2281 Some BIOSes seem to corrupt the first 64k of
2282 memory when doing things like suspend/resume.
2283 Setting this option will scan the memory
2284 looking for corruption. Enabling this will
2285 both detect corruption and prevent the kernel
2286 from using the memory being corrupted.
2287 However, its intended as a diagnostic tool; if
2288 repeatable BIOS-originated corruption always
2289 affects the same memory, you can use memmap=
2290 to prevent the kernel from using that memory.
2292 memory_corruption_check_size=size [X86]
2293 By default it checks for corruption in the low
2294 64k, making this memory unavailable for normal
2295 use. Use this parameter to scan for
2296 corruption in more or less memory.
2298 memory_corruption_check_period=seconds [X86]
2299 By default it checks for corruption every 60
2300 seconds. Use this parameter to check at some
2301 other rate. 0 disables periodic checking.
2303 memtest= [KNL,X86,ARM] Enable memtest
2305 default : 0 <disable>
2306 Specifies the number of memtest passes to be
2307 performed. Each pass selects another test
2308 pattern from a given set of patterns. Memtest
2309 fills the memory with this pattern, validates
2310 memory contents and reserves bad memory
2311 regions that are detected.
2313 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
2314 Valid arguments: on, off
2315 Default (depends on kernel configuration option):
2316 on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
2317 off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
2318 mem_encrypt=on: Activate SME
2319 mem_encrypt=off: Do not activate SME
2321 Refer to Documentation/x86/amd-memory-encryption.txt
2322 for details on when memory encryption can be activated.
2324 mem_sleep_default= [SUSPEND] Default system suspend mode:
2325 s2idle - Suspend-To-Idle
2326 shallow - Power-On Suspend or equivalent (if supported)
2327 deep - Suspend-To-RAM or equivalent (if supported)
2328 See Documentation/admin-guide/pm/sleep-states.rst.
2330 meye.*= [HW] Set MotionEye Camera parameters
2331 See Documentation/media/v4l-drivers/meye.rst.
2333 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2334 Multi-Function General Purpose Timers on AMD Geode
2337 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2338 the BIOS has incorrectly applied a workaround. TinyBIOS
2339 version 0.98 is known to be affected, 0.99 fixes the
2340 problem by letting the user disable the workaround.
2344 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2345 physical address is ignored.
2347 mini2440= [ARM,HW,KNL]
2348 Format:[0..2][b][c][t]
2350 MINI2440 configuration specification:
2351 0 - The attached screen is the 3.5" TFT
2352 1 - The attached screen is the 7" TFT
2353 2 - The VGA Shield is attached (1024x768)
2354 Leaving out the screen size parameter will not load
2355 the TFT driver, and the framebuffer will be left
2357 b - Enable backlight. The TFT backlight pin will be
2358 linked to the kernel VESA blanking code and a GPIO
2359 LED. This parameter is not necessary when using the
2361 c - Enable the s3c camera interface.
2362 t - Reserved for enabling touchscreen support. The
2363 touchscreen support is not enabled in the mainstream
2364 kernel as of 2.6.30, a preliminary port can be found
2365 in the "bleeding edge" mini2440 support kernel at
2366 http://repo.or.cz/w/linux-2.6/mini2440.git
2369 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2370 parameter allows control of the logging verbosity for
2371 the additional memory initialisation checks. A value
2372 of 0 disables mminit logging and a level of 4 will
2373 log everything. Information is printed at KERN_DEBUG
2374 so loglevel=8 may also need to be specified.
2377 [KNL] When CONFIG_MODULE_SIG is set, this means that
2378 modules without (valid) signatures will fail to load.
2379 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2380 is always true, so this option does nothing.
2382 module_blacklist= [KNL] Do not load a comma-separated list of
2383 modules. Useful for debugging problem modules.
2386 [MOUSE] Maximum time between finger touching and
2387 leaving touchpad surface for touch to be considered
2388 a tap and be reported as a left button click (for
2389 touchpads working in absolute mode only).
2391 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2392 reporting absolute coordinates, such as tablets
2393 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2394 reporting absolute coordinates, such as tablets
2396 movablecore= [KNL,X86,IA-64,PPC]
2397 Format: nn[KMGTPE] | nn%
2398 This parameter is the complement to kernelcore=, it
2399 specifies the amount of memory used for migratable
2400 allocations. If both kernelcore and movablecore is
2401 specified, then kernelcore will be at *least* the
2402 specified value but may be more. If movablecore on its
2403 own is specified, the administrator must be careful
2404 that the amount of memory usable for all allocations
2407 movable_node [KNL] Boot-time switch to make hotplugable memory
2408 NUMA nodes to be movable. This means that the memory
2409 of such nodes will be usable only for movable
2410 allocations which rules out almost all kernel
2411 allocations. Use with caution!
2413 MTD_Partition= [MTD]
2414 Format: <name>,<region-number>,<size>,<offset>
2416 MTD_Region= [MTD] Format:
2417 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2420 See drivers/mtd/cmdlinepart.c.
2422 multitce=off [PPC] This parameter disables the use of the pSeries
2423 firmware feature for updating multiple TCE entries
2426 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2428 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2430 boundary - index of last SLC block on Flex-OneNAND.
2431 The remaining blocks are configured as MLC blocks.
2432 lock - Configure if Flex-OneNAND boundary should be locked.
2433 Once locked, the boundary cannot be changed.
2434 1 indicates lock status, 0 indicates unlock status.
2437 ARM/S3C2412 JIVE boot control
2439 See arch/arm/mach-s3c2412/mach-jive.c
2441 mtouchusb.raw_coordinates=
2442 [HW] Make the MicroTouch USB driver use raw coordinates
2443 ('y', default) or cooked coordinates ('n')
2445 mtrr_chunk_size=nn[KMG] [X86]
2446 used for mtrr cleanup. It is largest continuous chunk
2447 that could hold holes aka. UC entries.
2449 mtrr_gran_size=nn[KMG] [X86]
2450 Used for mtrr cleanup. It is granularity of mtrr block.
2452 Large value could prevent small alignment from
2455 mtrr_spare_reg_nr=n [X86]
2457 Range: 0,7 : spare reg number
2459 Used for mtrr cleanup. It is spare mtrr entries number.
2460 Set to 2 or more if your graphical card needs more.
2462 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2464 netdev= [NET] Network devices parameters
2465 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2466 Note that mem_start is often overloaded to mean
2467 something different and driver-specific.
2468 This usage is only documented in each driver source
2472 [NETFILTER] Enable connection tracking flow accounting
2473 0 to disable accounting
2474 1 to enable accounting
2477 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2478 See Documentation/filesystems/nfs/nfsroot.txt.
2480 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2481 See Documentation/filesystems/nfs/nfsroot.txt.
2483 nfsrootdebug [NFS] enable nfsroot debugging messages.
2484 See Documentation/filesystems/nfs/nfsroot.txt.
2486 nfs.callback_nr_threads=
2487 [NFSv4] set the total number of threads that the
2488 NFS client will assign to service NFSv4 callback
2491 nfs.callback_tcpport=
2492 [NFS] set the TCP port on which the NFSv4 callback
2493 channel should listen.
2496 [NFS] sets the pathname to the program which is used
2497 to update the NFS client cache entries.
2499 nfs.cache_getent_timeout=
2500 [NFS] sets the timeout after which an attempt to
2501 update a cache entry is deemed to have failed.
2503 nfs.idmap_cache_timeout=
2504 [NFS] set the maximum lifetime for idmapper cache
2508 [NFS] enable 64-bit inode numbers.
2509 If zero, the NFS client will fake up a 32-bit inode
2510 number for the readdir() and stat() syscalls instead
2511 of returning the full 64-bit number.
2512 The default is to return 64-bit inode numbers.
2514 nfs.max_session_cb_slots=
2515 [NFSv4.1] Sets the maximum number of session
2516 slots the client will assign to the callback
2517 channel. This determines the maximum number of
2518 callbacks the client will process in parallel for
2519 a particular server.
2521 nfs.max_session_slots=
2522 [NFSv4.1] Sets the maximum number of session slots
2523 the client will attempt to negotiate with the server.
2524 This limits the number of simultaneous RPC requests
2525 that the client can send to the NFSv4.1 server.
2526 Note that there is little point in setting this
2527 value higher than the max_tcp_slot_table_limit.
2529 nfs.nfs4_disable_idmapping=
2530 [NFSv4] When set to the default of '1', this option
2531 ensures that both the RPC level authentication
2532 scheme and the NFS level operations agree to use
2533 numeric uids/gids if the mount is using the
2534 'sec=sys' security flavour. In effect it is
2535 disabling idmapping, which can make migration from
2536 legacy NFSv2/v3 systems to NFSv4 easier.
2537 Servers that do not support this mode of operation
2538 will be autodetected by the client, and it will fall
2539 back to using the idmapper.
2540 To turn off this behaviour, set the value to '0'.
2542 [NFS4] Specify an additional fixed unique ident-
2543 ification string that NFSv4 clients can insert into
2544 their nfs_client_id4 string. This is typically a
2545 UUID that is generated at system install time.
2547 nfs.send_implementation_id =
2548 [NFSv4.1] Send client implementation identification
2549 information in exchange_id requests.
2550 If zero, no implementation identification information
2552 The default is to send the implementation identification
2555 nfs.recover_lost_locks =
2556 [NFSv4] Attempt to recover locks that were lost due
2557 to a lease timeout on the server. Please note that
2558 doing this risks data corruption, since there are
2559 no guarantees that the file will remain unchanged
2560 after the locks are lost.
2561 If you want to enable the kernel legacy behaviour of
2562 attempting to recover these locks, then set this
2564 The default parameter value of '0' causes the kernel
2565 not to attempt recovery of lost locks.
2567 nfs4.layoutstats_timer =
2568 [NFSv4.2] Change the rate at which the kernel sends
2569 layoutstats to the pNFS metadata server.
2571 Setting this to value to 0 causes the kernel to use
2572 whatever value is the default set by the layout
2573 driver. A non-zero value sets the minimum interval
2574 in seconds between layoutstats transmissions.
2576 nfsd.nfs4_disable_idmapping=
2577 [NFSv4] When set to the default of '1', the NFSv4
2578 server will return only numeric uids and gids to
2579 clients using auth_sys, and will accept numeric uids
2580 and gids from such clients. This is intended to ease
2581 migration from NFSv2/v3.
2583 nmi_debug= [KNL,SH] Specify one or more actions to take
2584 when a NMI is triggered.
2585 Format: [state][,regs][,debounce][,die]
2587 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2588 Format: [panic,][nopanic,][num]
2590 0 - turn hardlockup detector in nmi_watchdog off
2591 1 - turn hardlockup detector in nmi_watchdog on
2592 When panic is specified, panic when an NMI watchdog
2593 timeout occurs (or 'nopanic' to override the opposite
2594 default). To disable both hard and soft lockup detectors,
2595 please see 'nowatchdog'.
2596 This is useful when you use a panic=... timeout and
2597 need the box quickly up again.
2599 These settings can be accessed at runtime via
2600 the nmi_watchdog and hardlockup_panic sysctls.
2602 netpoll.carrier_timeout=
2603 [NET] Specifies amount of time (in seconds) that
2604 netpoll should wait for a carrier. By default netpoll
2607 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2608 emulation library even if a 387 maths coprocessor
2612 [HW] Never suspend the console
2613 Disable suspending of consoles during suspend and
2614 hibernate operations. Once disabled, debugging
2615 messages can reach various consoles while the rest
2616 of the system is being put to sleep (ie, while
2617 debugging driver suspend/resume hooks). This may
2618 not work reliably with all consoles, but is known
2619 to work with serial and VGA consoles.
2620 To facilitate more flexible debugging, we also add
2621 console_suspend, a printk module parameter to control
2622 it. Users could use console_suspend (usually
2623 /sys/module/printk/parameters/console_suspend) to
2624 turn on/off it dynamically.
2626 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2627 caches in the slab allocator. Saves per-node memory,
2628 but will impact performance.
2632 noaltinstr [S390] Disables alternative instructions patching
2633 (CPU alternatives feature).
2635 noapic [SMP,APIC] Tells the kernel to not make use of any
2636 IOAPICs that may be present in the system.
2638 noautogroup Disable scheduler automatic task group creation.
2640 nobats [PPC] Do not use BATs for mapping kernel lowmem
2641 on "Classic" PPC cores.
2645 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2647 nodelayacct [KNL] Disable per-task delay accounting
2649 nodsp [SH] Disable hardware DSP at boot time.
2651 noefi Disable EFI runtime services support.
2656 On X86-32 available only on PAE configured kernels.
2657 noexec=on: enable non-executable mappings (default)
2658 noexec=off: disable non-executable mappings
2661 Disable SMAP (Supervisor Mode Access Prevention)
2662 even if it is supported by processor.
2665 Disable SMEP (Supervisor Mode Execution Prevention)
2666 even if it is supported by processor.
2669 This affects only 32-bit executables.
2670 noexec32=on: enable non-executable mappings (default)
2671 read doesn't imply executable mappings
2672 noexec32=off: disable non-executable mappings
2673 read implies executable mappings
2675 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2677 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2678 register save and restore. The kernel will only save
2679 legacy floating-point registers on task switch.
2681 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2683 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
2684 Equivalent to smt=1.
2686 nospectre_v2 [X86] Disable all mitigations for the Spectre variant 2
2687 (indirect branch prediction) vulnerability. System may
2688 allow data leaks with this option, which is equivalent
2691 nospec_store_bypass_disable
2692 [HW] Disable all mitigations for the Speculative Store Bypass vulnerability
2694 noxsave [BUGS=X86] Disables x86 extended register state save
2695 and restore using xsave. The kernel will fallback to
2696 enabling legacy floating-point and sse state.
2698 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2699 register states. The kernel will fall back to use
2700 xsave to save the states. By using this parameter,
2701 performance of saving the states is degraded because
2702 xsave doesn't support modified optimization while
2703 xsaveopt supports it on xsaveopt enabled systems.
2705 noxsaves [X86] Disables xsaves and xrstors used in saving and
2706 restoring x86 extended register state in compacted
2707 form of xsave area. The kernel will fall back to use
2708 xsaveopt and xrstor to save and restore the states
2709 in standard form of xsave area. By using this
2710 parameter, xsave area per process might occupy more
2711 memory on xsaves enabled systems.
2713 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2714 wfi(ARM) instruction doesn't work correctly and not to
2715 use it. This is also useful when using JTAG debugger.
2717 no_file_caps Tells the kernel not to honor file capabilities. The
2718 only way then for a file to be executed with privilege
2719 is to be setuid root or executed by root.
2721 nohalt [IA-64] Tells the kernel not to use the power saving
2722 function PAL_HALT_LIGHT when idle. This increases
2723 power-consumption. On the positive side, it reduces
2724 interrupt wake-up latency, which may improve performance
2725 in certain environments such as networked servers or
2728 nohibernate [HIBERNATION] Disable hibernation and resume.
2730 nohz= [KNL] Boottime enable/disable dynamic ticks
2731 Valid arguments: on, off
2734 nohz_full= [KNL,BOOT,SMP,ISOL]
2735 The argument is a cpu list, as described above.
2736 In kernels built with CONFIG_NO_HZ_FULL=y, set
2737 the specified list of CPUs whose tick will be stopped
2738 whenever possible. The boot CPU will be forced outside
2739 the range to maintain the timekeeping. Any CPUs
2740 in this list will have their RCU callbacks offloaded,
2741 just as if they had also been called out in the
2742 rcu_nocbs= boot parameter.
2744 noiotrap [SH] Disables trapped I/O port accesses.
2746 noirqdebug [X86-32] Disables the code which attempts to detect and
2747 disable unhandled interrupt sources.
2749 no_timer_check [X86,APIC] Disables the code which tests for
2750 broken timer IRQ sources.
2752 noisapnp [ISAPNP] Disables ISA PnP code.
2754 noinitrd [RAM] Tells the kernel not to load any configured
2757 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2759 [Deprecated - use intremap=off]
2763 noinvpcid [X86] Disable the INVPCID cpu feature.
2765 nojitter [IA-64] Disables jitter checking for ITC timers.
2767 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2769 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2773 [X86,PV_OPS] Disable paravirtualized VMware scheduler
2774 clock and use the default one.
2776 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2777 steal time is computed, but won't influence scheduler
2780 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2782 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2784 noltlbs [PPC] Do not use large page/tlb entries for kernel
2785 lowmem mapping on PPC40x and PPC8xx
2787 nomca [IA-64] Disable machine check abort handling
2789 nomce [X86-32] Disable Machine Check Exception
2791 nomfgpt [X86-32] Disable Multi-Function General Purpose
2792 Timer usage (for AMD Geode machines).
2794 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2795 shutdown the other cpus. Instead use the REBOOT_VECTOR
2798 nomodule Disable module load
2800 nopat [X86] Disable PAT (page attribute table extension of
2801 pagetables) support.
2803 nopcid [X86-64] Disable the PCID cpu feature.
2805 norandmaps Don't use address space randomization. Equivalent to
2806 echo 0 > /proc/sys/kernel/randomize_va_space
2808 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2809 with UP alternatives
2811 nordrand [X86] Disable kernel use of the RDRAND and
2812 RDSEED instructions even if they are supported
2813 by the processor. RDRAND and RDSEED are still
2814 available to user space applications.
2816 noresume [SWSUSP] Disables resume and restores original swap
2819 no-scroll [VGA] Disables scrollback.
2820 This is required for the Braillex ib80-piezo Braille
2821 reader made by F.H. Papenmeier (Germany).
2825 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2827 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2828 and disable the IO APIC. legacy for "maxcpus=0".
2830 nosoftlockup [KNL] Disable the soft-lockup detector.
2832 nosync [HW,M68K] Disables sync negotiation for all devices.
2834 notsc [BUGS=X86-32] Disable Time Stamp Counter
2836 nowatchdog [KNL] Disable both lockup detectors, i.e.
2837 soft-lockup and NMI watchdog (hard-lockup).
2841 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2843 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2844 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2845 Some features depend on CPU0. Known dependencies are:
2846 1. Resume from suspend/hibernate depends on CPU0.
2847 Suspend/hibernate will fail if CPU0 is offline and you
2848 need to online CPU0 before suspend/hibernate.
2849 2. PIC interrupts also depend on CPU0. CPU0 can't be
2850 removed if a PIC interrupt is detected.
2851 It's said poweroff/reboot may depend on CPU0 on some
2852 machines although I haven't seen such issues so far
2853 after CPU0 is offline on a few tested machines.
2854 If the dependencies are under your control, you can
2855 turn on cpu0_hotplug.
2857 nps_mtm_hs_ctr= [KNL,ARC]
2858 This parameter sets the maximum duration, in
2859 cycles, each HW thread of the CTOP can run
2860 without interruptions, before HW switches it.
2861 The actual maximum duration is 16 times this
2863 Format: integer between 1 and 255
2866 nptcg= [IA-64] Override max number of concurrent global TLB
2867 purges which is reported from either PAL_VM_SUMMARY or
2870 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2871 could support. nr_cpus=n : n >= 1 limits the kernel to
2872 support 'n' processors. It could be larger than the
2873 number of already plugged CPU during bootup, later in
2874 runtime you can physically add extra cpu until it reaches
2875 n. So during boot up some boot time memory for per-cpu
2876 variables need be pre-allocated for later physical cpu
2879 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2881 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2882 Allowed values are enable and disable
2884 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2885 'node', 'default' can be specified
2886 This can be set from sysctl after boot.
2887 See Documentation/sysctl/vm.txt for details.
2889 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2890 See Documentation/debugging-via-ohci1394.txt for more
2893 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2894 Rather than timing out after 20 ms if an EC
2895 command is not properly ACKed, override the length
2896 of the timeout. We have interrupts disabled while
2897 waiting for the ACK, so if this is set too high
2898 interrupts *may* be lost!
2900 omap_mux= [OMAP] Override bootloader pin multiplexing.
2901 Format: <mux_mode0.mode_name=value>...
2902 For example, to override I2C bus2:
2903 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2905 oprofile.timer= [HW]
2906 Use timer interrupt instead of performance counters
2908 oprofile.cpu_type= Force an oprofile cpu type
2909 This might be useful if you have an older oprofile
2910 userland or if you want common events.
2911 Format: { arch_perfmon }
2912 arch_perfmon: [X86] Force use of architectural
2913 perfmon on Intel CPUs instead of the
2914 CPU specific event set.
2915 timer: [X86] Force use of architectural NMI
2916 timer mode (see also oprofile.timer
2917 for generic hr timer mode)
2919 oops=panic Always panic on oopses. Default is to just kill the
2920 process, but there is a small probability of
2921 deadlocking the machine.
2922 This will also cause panics on machine check exceptions.
2923 Useful together with panic=30 to trigger a reboot.
2926 See Documentation/sound/oss/oss-parameters.txt
2928 page_owner= [KNL] Boot-time page_owner enabling option.
2929 Storage of the information about who allocated
2930 each page is disabled in default. With this switch,
2932 on: enable the feature
2934 page_poison= [KNL] Boot-time parameter changing the state of
2935 poisoning on the buddy allocator.
2936 off: turn off poisoning
2937 on: turn on poisoning
2939 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2940 timeout > 0: seconds before rebooting
2941 timeout = 0: wait forever
2942 timeout < 0: reboot immediately
2945 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2948 crash_kexec_post_notifiers
2949 Run kdump after running panic-notifiers and dumping
2950 kmsg. This only for the users who doubt kdump always
2951 succeeds in any situation.
2952 Note that this also increases risks of kdump failure,
2953 because some panic notifiers can make the crashed
2954 kernel more unstable.
2956 parkbd.port= [HW] Parallel port number the keyboard adapter is
2957 connected to, default is 0.
2959 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2960 0 for XT, 1 for AT (default is AT).
2963 parport= [HW,PPT] Specify parallel ports. 0 disables.
2964 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2965 Use 'auto' to force the driver to use any
2966 IRQ/DMA settings detected (the default is to
2967 ignore detected IRQ/DMA settings because of
2968 possible conflicts). You can specify the base
2969 address, IRQ, and DMA settings; IRQ and DMA
2970 should be numbers, or 'auto' (for using detected
2971 settings on that particular port), or 'nofifo'
2972 (to avoid using a FIFO even if it is detected).
2973 Parallel ports are assigned in the order they
2974 are specified on the command line, starting
2977 parport_init_mode= [HW,PPT]
2978 Configure VIA parallel port to operate in
2979 a specific mode. This is necessary on Pegasos
2980 computer where firmware has no options for setting
2981 up parallel port mode and sets it to spp.
2982 Currently this function knows 686a and 8231 chips.
2983 Format: [spp|ps2|epp|ecp|ecpepp]
2986 Halt all CPUs after the first oops has been printed for
2987 the specified number of seconds. This is to be used if
2988 your oopses keep scrolling off the screen.
2993 See header of drivers/block/paride/pcd.c.
2994 See also Documentation/blockdev/paride.txt.
2996 pci=option[,option...] [PCI] various PCI subsystem options:
2997 earlydump [X86] dump PCI config space before the kernel
2999 off [X86] don't probe for the PCI bus
3000 bios [X86-32] force use of PCI BIOS, don't access
3001 the hardware directly. Use this if your machine
3002 has a non-standard PCI host bridge.
3003 nobios [X86-32] disallow use of PCI BIOS, only direct
3004 hardware access methods are allowed. Use this
3005 if you experience crashes upon bootup and you
3006 suspect they are caused by the BIOS.
3007 conf1 [X86] Force use of PCI Configuration Access
3008 Mechanism 1 (config address in IO port 0xCF8,
3009 data in IO port 0xCFC, both 32-bit).
3010 conf2 [X86] Force use of PCI Configuration Access
3011 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
3012 the function, IO port 0xCFA, also 8-bit, sets
3013 bus number. The config space is then accessed
3014 through ports 0xC000-0xCFFF).
3015 See http://wiki.osdev.org/PCI for more info
3016 on the configuration access mechanisms.
3017 noaer [PCIE] If the PCIEAER kernel config parameter is
3018 enabled, this kernel boot option can be used to
3019 disable the use of PCIE advanced error reporting.
3020 nodomains [PCI] Disable support for multiple PCI
3021 root domains (aka PCI segments, in ACPI-speak).
3022 nommconf [X86] Disable use of MMCONFIG for PCI
3024 check_enable_amd_mmconf [X86] check for and enable
3025 properly configured MMIO access to PCI
3026 config space on AMD family 10h CPU
3027 nomsi [MSI] If the PCI_MSI kernel config parameter is
3028 enabled, this kernel boot option can be used to
3029 disable the use of MSI interrupts system-wide.
3030 noioapicquirk [APIC] Disable all boot interrupt quirks.
3031 Safety option to keep boot IRQs enabled. This
3032 should never be necessary.
3033 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
3034 primary IO-APIC for bridges that cannot disable
3035 boot IRQs. This fixes a source of spurious IRQs
3036 when the system masks IRQs.
3037 noioapicreroute [APIC] Disable workaround that uses the
3038 boot IRQ equivalent of an IRQ that connects to
3039 a chipset where boot IRQs cannot be disabled.
3040 The opposite of ioapicreroute.
3041 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
3042 routing table. These calls are known to be buggy
3043 on several machines and they hang the machine
3044 when used, but on other computers it's the only
3045 way to get the interrupt routing table. Try
3046 this option if the kernel is unable to allocate
3047 IRQs or discover secondary PCI buses on your
3049 rom [X86] Assign address space to expansion ROMs.
3050 Use with caution as certain devices share
3051 address decoders between ROMs and other
3053 norom [X86] Do not assign address space to
3054 expansion ROMs that do not already have
3055 BIOS assigned address ranges.
3056 nobar [X86] Do not assign address space to the
3057 BARs that weren't assigned by the BIOS.
3058 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
3059 assigned automatically to PCI devices. You can
3060 make the kernel exclude IRQs of your ISA cards
3062 pirqaddr=0xAAAAA [X86] Specify the physical address
3063 of the PIRQ table (normally generated
3064 by the BIOS) if it is outside the
3065 F0000h-100000h range.
3066 lastbus=N [X86] Scan all buses thru bus #N. Can be
3067 useful if the kernel is unable to find your
3068 secondary buses and you want to tell it
3069 explicitly which ones they are.
3070 assign-busses [X86] Always assign all PCI bus
3071 numbers ourselves, overriding
3072 whatever the firmware may have done.
3073 usepirqmask [X86] Honor the possible IRQ mask stored
3074 in the BIOS $PIR table. This is needed on
3075 some systems with broken BIOSes, notably
3076 some HP Pavilion N5400 and Omnibook XE3
3077 notebooks. This will have no effect if ACPI
3078 IRQ routing is enabled.
3079 noacpi [X86] Do not use ACPI for IRQ routing
3080 or for PCI scanning.
3081 use_crs [X86] Use PCI host bridge window information
3082 from ACPI. On BIOSes from 2008 or later, this
3083 is enabled by default. If you need to use this,
3084 please report a bug.
3085 nocrs [X86] Ignore PCI host bridge windows from ACPI.
3086 If you need to use this, please report a bug.
3087 routeirq Do IRQ routing for all PCI devices.
3088 This is normally done in pci_enable_device(),
3089 so this option is a temporary workaround
3090 for broken drivers that don't call it.
3091 skip_isa_align [X86] do not align io start addr, so can
3092 handle more pci cards
3093 noearly [X86] Don't do any early type 1 scanning.
3094 This might help on some broken boards which
3095 machine check when some devices' config space
3096 is read. But various workarounds are disabled
3097 and some IOMMU drivers will not work.
3098 bfsort Sort PCI devices into breadth-first order.
3099 This sorting is done to get a device
3100 order compatible with older (<= 2.4) kernels.
3101 nobfsort Don't sort PCI devices into breadth-first order.
3102 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
3103 tuning and use the BIOS-configured MPS defaults.
3104 pcie_bus_safe Set every device's MPS to the largest value
3105 supported by all devices below the root complex.
3106 pcie_bus_perf Set device MPS to the largest allowable MPS
3107 based on its parent bus. Also set MRRS (Max
3108 Read Request Size) to the largest supported
3109 value (no larger than the MPS that the device
3110 or bus can support) for best performance.
3111 pcie_bus_peer2peer Set every device's MPS to 128B, which
3112 every device is guaranteed to support. This
3113 configuration allows peer-to-peer DMA between
3114 any pair of devices, possibly at the cost of
3115 reduced performance. This also guarantees
3116 that hot-added devices will work.
3117 cbiosize=nn[KMG] The fixed amount of bus space which is
3118 reserved for the CardBus bridge's IO window.
3119 The default value is 256 bytes.
3120 cbmemsize=nn[KMG] The fixed amount of bus space which is
3121 reserved for the CardBus bridge's memory
3122 window. The default value is 64 megabytes.
3125 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
3126 [<order of align>@]pci:<vendor>:<device>\
3127 [:<subvendor>:<subdevice>][; ...]
3128 Specifies alignment and device to reassign
3129 aligned memory resources.
3130 If <order of align> is not specified,
3131 PAGE_SIZE is used as alignment.
3132 PCI-PCI bridge can be specified, if resource
3133 windows need to be expanded.
3134 To specify the alignment for several
3135 instances of a device, the PCI vendor,
3136 device, subvendor, and subdevice may be
3137 specified, e.g., 4096@pci:8086:9c22:103c:198f
3138 ecrc= Enable/disable PCIe ECRC (transaction layer
3139 end-to-end CRC checking).
3140 bios: Use BIOS/firmware settings. This is the
3144 hpiosize=nn[KMG] The fixed amount of bus space which is
3145 reserved for hotplug bridge's IO window.
3146 Default size is 256 bytes.
3147 hpmemsize=nn[KMG] The fixed amount of bus space which is
3148 reserved for hotplug bridge's memory window.
3149 Default size is 2 megabytes.
3150 hpbussize=nn The minimum amount of additional bus numbers
3151 reserved for buses below a hotplug bridge.
3153 realloc= Enable/disable reallocating PCI bridge resources
3154 if allocations done by BIOS are too small to
3155 accommodate resources required by all child
3157 off: Turn realloc off
3159 realloc same as realloc=on
3160 noari do not use PCIe ARI.
3161 pcie_scan_all Scan all possible PCIe devices. Otherwise we
3162 only look for one device below a PCIe downstream
3164 big_root_window Try to add a big 64bit memory window to the PCIe
3165 root complex on AMD CPUs. Some GFX hardware
3166 can resize a BAR to allow access to all VRAM.
3167 Adding the window is slightly risky (it may
3168 conflict with unreported devices), so this
3171 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
3174 force Enable ASPM even on devices that claim not to support it.
3175 WARNING: Forcing ASPM on may cause system lockups.
3177 pcie_ports= [PCIE] PCIe port services handling:
3178 native Use native PCIe services (PME, AER, DPC, PCIe hotplug)
3179 even if the platform doesn't give the OS permission to
3180 use them. This may cause conflicts if the platform
3181 also tries to use these services.
3182 compat Disable native PCIe services (PME, AER, DPC, PCIe
3185 pcie_port_pm= [PCIE] PCIe port power management handling:
3186 off Disable power management of all PCIe ports
3187 force Forcibly enable power management of all PCIe ports
3189 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
3190 nomsi Do not use MSI for native PCIe PME signaling (this makes
3191 all PCIe root ports use INTx for all services).
3193 pcmv= [HW,PCMCIA] BadgePAD 4
3197 Keep all power-domains already enabled by bootloader on,
3198 even if no driver has claimed them. This is useful
3199 for debug and development, but should not be
3200 needed on a platform with proper driver support.
3203 See Documentation/blockdev/paride.txt.
3205 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
3208 See arch/parisc/kernel/pdc_chassis.c
3210 percpu_alloc= Select which percpu first chunk allocator to use.
3211 Currently supported values are "embed" and "page".
3212 Archs may support subset or none of the selections.
3213 See comments in mm/percpu.c for details on each
3214 allocator. This parameter is primarily for debugging
3215 and performance comparison.
3218 See Documentation/blockdev/paride.txt.
3221 See Documentation/blockdev/paride.txt.
3223 pirq= [SMP,APIC] Manual mp-table setup
3224 See Documentation/x86/i386/IO-APIC.txt.
3226 plip= [PPT,NET] Parallel port network link
3227 Format: { parport<nr> | timid | 0 }
3228 See also Documentation/admin-guide/parport.rst.
3230 pmtmr= [X86] Manual setup of pmtmr I/O Port.
3231 Override pmtimer IOPort with a hex value.
3235 Enable PNP debug messages (depends on the
3236 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
3237 via /sys/module/pnp/parameters/debug. We always show
3238 current resource usage; turning this on also shows
3239 possible settings and some assignment information.
3245 { on | off | curr | res | no-curr | no-res }
3248 [ISAPNP] Exclude IRQs for the autoconfiguration
3251 [ISAPNP] Exclude DMAs for the autoconfiguration
3253 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
3254 Ranges are in pairs (I/O port base and size).
3257 [ISAPNP] Exclude memory regions for the
3259 Ranges are in pairs (memory base and size).
3261 ports= [IP_VS_FTP] IPVS ftp helper module
3263 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3265 Format: <port>,<port>....
3267 powersave=off [PPC] This option disables power saving features.
3268 It specifically disables cpuidle and sets the
3269 platform machine description specific power_save
3270 function to NULL. On Idle the CPU just reduces
3273 ppc_strict_facility_enable
3274 [PPC] This option catches any kernel floating point,
3275 Altivec, VSX and SPE outside of regions specifically
3276 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3277 There is some performance impact when enabling this.
3281 Disable Hardware Transactional Memory
3283 print-fatal-signals=
3284 [KNL] debug: print fatal signals
3286 If enabled, warn about various signal handling
3287 related application anomalies: too many signals,
3288 too many POSIX.1 timers, fatal signals causing a
3291 If you hit the warning due to signal overflow,
3292 you might want to try "ulimit -i unlimited".
3296 printk.always_kmsg_dump=
3297 Trigger kmsg_dump for cases other than kernel oops or
3299 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3302 printk.devkmsg={on,off,ratelimit}
3303 Control writing to /dev/kmsg.
3304 on - unlimited logging to /dev/kmsg from userspace
3305 off - logging to /dev/kmsg disabled
3306 ratelimit - ratelimit the logging
3309 printk.time= Show timing data prefixed to each printk message line
3310 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3312 processor.max_cstate= [HW,ACPI]
3313 Limit processor to maximum C-state
3314 max_cstate=9 overrides any DMI blacklist limit.
3316 processor.nocst [HW,ACPI]
3317 Ignore the _CST method to determine C-states,
3318 instead using the legacy FADT method
3320 profile= [KNL] Enable kernel profiling via /proc/profile
3321 Format: [<profiletype>,]<number>
3322 Param: <profiletype>: "schedule", "sleep", or "kvm"
3323 [defaults to kernel profiling]
3324 Param: "schedule" - profile schedule points.
3325 Param: "sleep" - profile D-state sleeping (millisecs).
3326 Requires CONFIG_SCHEDSTATS
3327 Param: "kvm" - profile VM exits.
3328 Param: <number> - step/bucket size as a power of 2 for
3329 statistical time based profiling.
3331 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3333 See Documentation/blockdev/ramdisk.txt.
3335 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3336 probe for; one of (bare|imps|exps|lifebook|any).
3337 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3339 psmouse.resetafter= [HW,MOUSE]
3340 Try to reset the device after so many bad packets
3343 [HW,MOUSE] Set desired mouse resolution, in dpi.
3344 psmouse.smartscroll=
3345 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3346 0 = disabled, 1 = enabled (default).
3348 pstore.backend= Specify the name of the pstore backend to use
3351 See Documentation/blockdev/paride.txt.
3353 pti= [X86_64] Control Page Table Isolation of user and
3354 kernel address spaces. Disabling this feature
3355 removes hardening, but improves performance of
3356 system calls and interrupts.
3358 on - unconditionally enable
3359 off - unconditionally disable
3360 auto - kernel detects whether your CPU model is
3361 vulnerable to issues that PTI mitigates
3363 Not specifying this option is equivalent to pti=auto.
3366 Equivalent to pti=off
3369 [KNL] Number of legacy pty's. Overwrites compiled-in
3372 quiet [KNL] Disable most log messages
3377 See Documentation/admin-guide/md.rst.
3379 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3380 See Documentation/blockdev/ramdisk.txt.
3382 ras=option[,option,...] [KNL] RAS-specific options
3385 Disable the Correctable Errors Collector,
3386 see CONFIG_RAS_CEC help text.
3389 The argument is a cpu list, as described above.
3391 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3392 the specified list of CPUs to be no-callback CPUs.
3393 Invocation of these CPUs' RCU callbacks will
3394 be offloaded to "rcuox/N" kthreads created for
3395 that purpose, where "x" is "b" for RCU-bh, "p"
3396 for RCU-preempt, and "s" for RCU-sched, and "N"
3397 is the CPU number. This reduces OS jitter on the
3398 offloaded CPUs, which can be useful for HPC and
3399 real-time workloads. It can also improve energy
3400 efficiency for asymmetric multiprocessors.
3403 Rather than requiring that offloaded CPUs
3404 (specified by rcu_nocbs= above) explicitly
3405 awaken the corresponding "rcuoN" kthreads,
3406 make these kthreads poll for callbacks.
3407 This improves the real-time response for the
3408 offloaded CPUs by relieving them of the need to
3409 wake up the corresponding kthread, but degrades
3410 energy efficiency by requiring that the kthreads
3411 periodically wake up to do the polling.
3413 rcutree.blimit= [KNL]
3414 Set maximum number of finished RCU callbacks to
3415 process in one batch.
3417 rcutree.dump_tree= [KNL]
3418 Dump the structure of the rcu_node combining tree
3419 out at early boot. This is used for diagnostic
3420 purposes, to verify correct tree setup.
3422 rcutree.gp_cleanup_delay= [KNL]
3423 Set the number of jiffies to delay each step of
3424 RCU grace-period cleanup.
3426 rcutree.gp_init_delay= [KNL]
3427 Set the number of jiffies to delay each step of
3428 RCU grace-period initialization.
3430 rcutree.gp_preinit_delay= [KNL]
3431 Set the number of jiffies to delay each step of
3432 RCU grace-period pre-initialization, that is,
3433 the propagation of recent CPU-hotplug changes up
3434 the rcu_node combining tree.
3436 rcutree.rcu_fanout_exact= [KNL]
3437 Disable autobalancing of the rcu_node combining
3438 tree. This is used by rcutorture, and might
3439 possibly be useful for architectures having high
3440 cache-to-cache transfer latencies.
3442 rcutree.rcu_fanout_leaf= [KNL]
3443 Change the number of CPUs assigned to each
3444 leaf rcu_node structure. Useful for very
3445 large systems, which will choose the value 64,
3446 and for NUMA systems with large remote-access
3447 latencies, which will choose a value aligned
3448 with the appropriate hardware boundaries.
3450 rcutree.jiffies_till_sched_qs= [KNL]
3451 Set required age in jiffies for a
3452 given grace period before RCU starts
3453 soliciting quiescent-state help from
3454 rcu_note_context_switch().
3456 rcutree.jiffies_till_first_fqs= [KNL]
3457 Set delay from grace-period initialization to
3458 first attempt to force quiescent states.
3459 Units are jiffies, minimum value is zero,
3460 and maximum value is HZ.
3462 rcutree.jiffies_till_next_fqs= [KNL]
3463 Set delay between subsequent attempts to force
3464 quiescent states. Units are jiffies, minimum
3465 value is one, and maximum value is HZ.
3467 rcutree.kthread_prio= [KNL,BOOT]
3468 Set the SCHED_FIFO priority of the RCU per-CPU
3469 kthreads (rcuc/N). This value is also used for
3470 the priority of the RCU boost threads (rcub/N)
3471 and for the RCU grace-period kthreads (rcu_bh,
3472 rcu_preempt, and rcu_sched). If RCU_BOOST is
3473 set, valid values are 1-99 and the default is 1
3474 (the least-favored priority). Otherwise, when
3475 RCU_BOOST is not set, valid values are 0-99 and
3476 the default is zero (non-realtime operation).
3478 rcutree.rcu_nocb_leader_stride= [KNL]
3479 Set the number of NOCB kthread groups, which
3480 defaults to the square root of the number of
3481 CPUs. Larger numbers reduces the wakeup overhead
3482 on the per-CPU grace-period kthreads, but increases
3483 that same overhead on each group's leader.
3485 rcutree.qhimark= [KNL]
3486 Set threshold of queued RCU callbacks beyond which
3487 batch limiting is disabled.
3489 rcutree.qlowmark= [KNL]
3490 Set threshold of queued RCU callbacks below which
3491 batch limiting is re-enabled.
3493 rcutree.rcu_idle_gp_delay= [KNL]
3494 Set wakeup interval for idle CPUs that have
3495 RCU callbacks (RCU_FAST_NO_HZ=y).
3497 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3498 Set wakeup interval for idle CPUs that have
3499 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3500 Lazy RCU callbacks are those which RCU can
3501 prove do nothing more than free memory.
3503 rcutree.rcu_kick_kthreads= [KNL]
3504 Cause the grace-period kthread to get an extra
3505 wake_up() if it sleeps three times longer than
3506 it should at force-quiescent-state time.
3507 This wake_up() will be accompanied by a
3508 WARN_ONCE() splat and an ftrace_dump().
3510 rcuperf.gp_async= [KNL]
3511 Measure performance of asynchronous
3512 grace-period primitives such as call_rcu().
3514 rcuperf.gp_async_max= [KNL]
3515 Specify the maximum number of outstanding
3516 callbacks per writer thread. When a writer
3517 thread exceeds this limit, it invokes the
3518 corresponding flavor of rcu_barrier() to allow
3519 previously posted callbacks to drain.
3521 rcuperf.gp_exp= [KNL]
3522 Measure performance of expedited synchronous
3523 grace-period primitives.
3525 rcuperf.holdoff= [KNL]
3526 Set test-start holdoff period. The purpose of
3527 this parameter is to delay the start of the
3528 test until boot completes in order to avoid
3531 rcuperf.nreaders= [KNL]
3532 Set number of RCU readers. The value -1 selects
3533 N, where N is the number of CPUs. A value
3534 "n" less than -1 selects N-n+1, where N is again
3535 the number of CPUs. For example, -2 selects N
3536 (the number of CPUs), -3 selects N+1, and so on.
3537 A value of "n" less than or equal to -N selects
3540 rcuperf.nwriters= [KNL]
3541 Set number of RCU writers. The values operate
3542 the same as for rcuperf.nreaders.
3543 N, where N is the number of CPUs
3545 rcuperf.perf_type= [KNL]
3546 Specify the RCU implementation to test.
3548 rcuperf.shutdown= [KNL]
3549 Shut the system down after performance tests
3550 complete. This is useful for hands-off automated
3553 rcuperf.verbose= [KNL]
3554 Enable additional printk() statements.
3556 rcuperf.writer_holdoff= [KNL]
3557 Write-side holdoff between grace periods,
3558 in microseconds. The default of zero says
3561 rcutorture.cbflood_inter_holdoff= [KNL]
3562 Set holdoff time (jiffies) between successive
3563 callback-flood tests.
3565 rcutorture.cbflood_intra_holdoff= [KNL]
3566 Set holdoff time (jiffies) between successive
3567 bursts of callbacks within a given callback-flood
3570 rcutorture.cbflood_n_burst= [KNL]
3571 Set the number of bursts making up a given
3572 callback-flood test. Set this to zero to
3573 disable callback-flood testing.
3575 rcutorture.cbflood_n_per_burst= [KNL]
3576 Set the number of callbacks to be registered
3577 in a given burst of a callback-flood test.
3579 rcutorture.fqs_duration= [KNL]
3580 Set duration of force_quiescent_state bursts
3583 rcutorture.fqs_holdoff= [KNL]
3584 Set holdoff time within force_quiescent_state bursts
3587 rcutorture.fqs_stutter= [KNL]
3588 Set wait time between force_quiescent_state bursts
3591 rcutorture.gp_cond= [KNL]
3592 Use conditional/asynchronous update-side
3593 primitives, if available.
3595 rcutorture.gp_exp= [KNL]
3596 Use expedited update-side primitives, if available.
3598 rcutorture.gp_normal= [KNL]
3599 Use normal (non-expedited) asynchronous
3600 update-side primitives, if available.
3602 rcutorture.gp_sync= [KNL]
3603 Use normal (non-expedited) synchronous
3604 update-side primitives, if available. If all
3605 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3606 rcutorture.gp_normal=, and rcutorture.gp_sync=
3607 are zero, rcutorture acts as if is interpreted
3608 they are all non-zero.
3610 rcutorture.n_barrier_cbs= [KNL]
3611 Set callbacks/threads for rcu_barrier() testing.
3613 rcutorture.nfakewriters= [KNL]
3614 Set number of concurrent RCU writers. These just
3615 stress RCU, they don't participate in the actual
3616 test, hence the "fake".
3618 rcutorture.nreaders= [KNL]
3619 Set number of RCU readers. The value -1 selects
3620 N-1, where N is the number of CPUs. A value
3621 "n" less than -1 selects N-n-2, where N is again
3622 the number of CPUs. For example, -2 selects N
3623 (the number of CPUs), -3 selects N+1, and so on.
3625 rcutorture.object_debug= [KNL]
3626 Enable debug-object double-call_rcu() testing.
3628 rcutorture.onoff_holdoff= [KNL]
3629 Set time (s) after boot for CPU-hotplug testing.
3631 rcutorture.onoff_interval= [KNL]
3632 Set time (s) between CPU-hotplug operations, or
3633 zero to disable CPU-hotplug testing.
3635 rcutorture.shuffle_interval= [KNL]
3636 Set task-shuffle interval (s). Shuffling tasks
3637 allows some CPUs to go into dyntick-idle mode
3638 during the rcutorture test.
3640 rcutorture.shutdown_secs= [KNL]
3641 Set time (s) after boot system shutdown. This
3642 is useful for hands-off automated testing.
3644 rcutorture.stall_cpu= [KNL]
3645 Duration of CPU stall (s) to test RCU CPU stall
3646 warnings, zero to disable.
3648 rcutorture.stall_cpu_holdoff= [KNL]
3649 Time to wait (s) after boot before inducing stall.
3651 rcutorture.stall_cpu_irqsoff= [KNL]
3652 Disable interrupts while stalling if set.
3654 rcutorture.stat_interval= [KNL]
3655 Time (s) between statistics printk()s.
3657 rcutorture.stutter= [KNL]
3658 Time (s) to stutter testing, for example, specifying
3659 five seconds causes the test to run for five seconds,
3660 wait for five seconds, and so on. This tests RCU's
3661 ability to transition abruptly to and from idle.
3663 rcutorture.test_boost= [KNL]
3664 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3665 "Maybe" means test if the RCU implementation
3666 under test support RCU priority boosting.
3668 rcutorture.test_boost_duration= [KNL]
3669 Duration (s) of each individual boost test.
3671 rcutorture.test_boost_interval= [KNL]
3672 Interval (s) between each boost test.
3674 rcutorture.test_no_idle_hz= [KNL]
3675 Test RCU's dyntick-idle handling. See also the
3676 rcutorture.shuffle_interval parameter.
3678 rcutorture.torture_type= [KNL]
3679 Specify the RCU implementation to test.
3681 rcutorture.verbose= [KNL]
3682 Enable additional printk() statements.
3684 rcupdate.rcu_cpu_stall_suppress= [KNL]
3685 Suppress RCU CPU stall warning messages.
3687 rcupdate.rcu_cpu_stall_timeout= [KNL]
3688 Set timeout for RCU CPU stall warning messages.
3690 rcupdate.rcu_expedited= [KNL]
3691 Use expedited grace-period primitives, for
3692 example, synchronize_rcu_expedited() instead
3693 of synchronize_rcu(). This reduces latency,
3694 but can increase CPU utilization, degrade
3695 real-time latency, and degrade energy efficiency.
3696 No effect on CONFIG_TINY_RCU kernels.
3698 rcupdate.rcu_normal= [KNL]
3699 Use only normal grace-period primitives,
3700 for example, synchronize_rcu() instead of
3701 synchronize_rcu_expedited(). This improves
3702 real-time latency, CPU utilization, and
3703 energy efficiency, but can expose users to
3704 increased grace-period latency. This parameter
3705 overrides rcupdate.rcu_expedited. No effect on
3706 CONFIG_TINY_RCU kernels.
3708 rcupdate.rcu_normal_after_boot= [KNL]
3709 Once boot has completed (that is, after
3710 rcu_end_inkernel_boot() has been invoked), use
3711 only normal grace-period primitives. No effect
3712 on CONFIG_TINY_RCU kernels.
3714 rcupdate.rcu_task_stall_timeout= [KNL]
3715 Set timeout in jiffies for RCU task stall warning
3716 messages. Disable with a value less than or equal
3719 rcupdate.rcu_self_test= [KNL]
3720 Run the RCU early boot self tests
3722 rcupdate.rcu_self_test_bh= [KNL]
3723 Run the RCU bh early boot self tests
3725 rcupdate.rcu_self_test_sched= [KNL]
3726 Run the RCU sched early boot self tests
3730 Run specified binary instead of /init from the ramdisk,
3731 used for early userspace startup. See initrd.
3734 Turn on/off individual RDT features. List is:
3735 cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
3737 E.g. to turn on cmt and turn off mba use:
3741 Format (x86 or x86_64):
3742 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3744 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3746 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3747 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3748 reboot_force is either force or not specified,
3749 reboot_cpu is s[mp]#### with #### being the processor
3750 to be used for rebooting.
3753 [KNL, SMP] Set scheduler's default relax_domain_level.
3754 See Documentation/cgroup-v1/cpusets.txt.
3756 reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory
3757 Format: <base1>,<size1>[,<base2>,<size2>,...]
3758 Reserve I/O ports or memory so the kernel won't use
3759 them. If <base> is less than 0x10000, the region
3760 is assumed to be I/O ports; otherwise it is memory.
3762 reservetop= [X86-32]
3764 Reserves a hole at the top of the kernel virtual
3769 Set the amount of memory to reserve for BIOS at
3770 the bottom of the address space.
3772 reset_devices [KNL] Force drivers to reset the underlying device
3773 during initialization.
3776 Specify the partition device for software suspend
3778 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3780 resume_offset= [SWSUSP]
3781 Specify the offset from the beginning of the partition
3782 given by "resume=" at which the swap header is located,
3783 in <PAGE_SIZE> units (needed only for swap files).
3784 See Documentation/power/swsusp-and-swap-files.txt
3786 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3787 read the resume files
3789 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3790 Useful for devices that are detected asynchronously
3791 (e.g. USB and MMC devices).
3793 hibernate= [HIBERNATION]
3794 noresume Don't check if there's a hibernation image
3795 present during boot.
3796 nocompress Don't compress/decompress hibernation images.
3797 no Disable hibernation and resume.
3798 protect_image Turn on image protection during restoration
3799 (that will set all pages holding image data
3800 during restoration read-only).
3802 retain_initrd [RAM] Keep initrd memory after extraction
3804 rfkill.default_state=
3805 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3806 etc. communication is blocked by default.
3809 rfkill.master_switch_mode=
3810 0 The "airplane mode" button does nothing.
3811 1 The "airplane mode" button toggles between everything
3812 blocked and the previous configuration.
3813 2 The "airplane mode" button toggles between everything
3814 blocked and everything unblocked.
3816 rhash_entries= [KNL,NET]
3817 Set number of hash buckets for route cache
3820 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
3823 ro [KNL] Mount root device read-only on boot
3826 on Mark read-only kernel memory as read-only (default).
3827 off Leave read-only kernel memory writable for debugging.
3830 Enable the uart passthrough on the designated usb port
3831 on Rockchip SoCs. When active, the signals of the
3832 debug-uart get routed to the D+ and D- pins of the usb
3833 port and the regular usb controller gets disabled.
3835 root= [KNL] Root filesystem
3836 See name_to_dev_t comment in init/do_mounts.c.
3838 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3839 mount the root filesystem
3841 rootflags= [KNL] Set root filesystem mount option string
3843 rootfstype= [KNL] Set root filesystem type
3845 rootwait [KNL] Wait (indefinitely) for root device to show up.
3846 Useful for devices that are detected asynchronously
3847 (e.g. USB and MMC devices).
3849 rproc_mem=nn[KMG][@address]
3850 [KNL,ARM,CMA] Remoteproc physical memory block.
3851 Memory area to be used by remote processor image,
3854 rw [KNL] Mount root device read-write on boot
3856 S [KNL] Run init in single mode
3858 s390_iommu= [HW,S390]
3859 Set s390 IOTLB flushing mode
3861 With strict flushing every unmap operation will result in
3862 an IOTLB flush. Default is lazy flushing before reuse,
3866 See drivers/net/irda/sa1100_ir.c.
3868 sbni= [NET] Granch SBNI12 leased line adapter
3870 sched_debug [KNL] Enables verbose scheduler debug messages.
3872 schedstats= [KNL,X86] Enable or disable scheduled statistics.
3873 Allowed values are enable and disable. This feature
3874 incurs a small amount of overhead in the scheduler
3875 but is useful for debugging and performance tuning.
3877 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3878 xtime_lock contention on larger systems, and/or RCU lock
3879 contention on all systems with CONFIG_MAXSMP set.
3880 Format: { "0" | "1" }
3881 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3883 Note: increases power consumption, thus should only be
3884 enabled if running jitter sensitive (HPC/RT) workloads.
3886 security= [SECURITY] Choose a security module to enable at boot.
3887 If this boot parameter is not specified, only the first
3888 security module asking for security registration will be
3889 loaded. An invalid security module name will be treated
3890 as if no module has been chosen.
3892 selinux= [SELINUX] Disable or enable SELinux at boot time.
3893 Format: { "0" | "1" }
3894 See security/selinux/Kconfig help text.
3897 Default value is set via kernel config option.
3898 If enabled at boot time, /selinux/disable can be used
3899 later to disable prior to initial policy load.
3901 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3902 Format: { "0" | "1" }
3903 See security/apparmor/Kconfig help text
3906 Default value is set via kernel config option.
3908 serialnumber [BUGS=X86-32]
3911 Maximal number of shapers.
3919 Disable merging of slabs with similar size. May be
3920 necessary if there is some reason to distinguish
3921 allocs to different slabs, especially in hardened
3922 environments where the risk of heap overflows and
3923 layout control by attackers can usually be
3924 frustrated by disabling merging. This will reduce
3925 most of the exposure of a heap attack to a single
3926 cache (risks via metadata attacks are mostly
3927 unchanged). Debug options disable merging on their
3929 For more information see Documentation/vm/slub.rst.
3931 slab_max_order= [MM, SLAB]
3932 Determines the maximum allowed order for slabs.
3933 A high setting may cause OOMs due to memory
3934 fragmentation. Defaults to 1 for systems with
3935 more than 32MB of RAM, 0 otherwise.
3937 slub_debug[=options[,slabs]] [MM, SLUB]
3938 Enabling slub_debug allows one to determine the
3939 culprit if slab objects become corrupted. Enabling
3940 slub_debug can create guard zones around objects and
3941 may poison objects when not in use. Also tracks the
3942 last alloc / free. For more information see
3943 Documentation/vm/slub.rst.
3945 slub_memcg_sysfs= [MM, SLUB]
3946 Determines whether to enable sysfs directories for
3947 memory cgroup sub-caches. 1 to enable, 0 to disable.
3948 The default is determined by CONFIG_SLUB_MEMCG_SYSFS_ON.
3949 Enabling this can lead to a very high number of debug
3950 directories and files being created under
3953 slub_max_order= [MM, SLUB]
3954 Determines the maximum allowed order for slabs.
3955 A high setting may cause OOMs due to memory
3956 fragmentation. For more information see
3957 Documentation/vm/slub.rst.
3959 slub_min_objects= [MM, SLUB]
3960 The minimum number of objects per slab. SLUB will
3961 increase the slab order up to slub_max_order to
3962 generate a sufficiently large slab able to contain
3963 the number of objects indicated. The higher the number
3964 of objects the smaller the overhead of tracking slabs
3965 and the less frequently locks need to be acquired.
3966 For more information see Documentation/vm/slub.rst.
3968 slub_min_order= [MM, SLUB]
3969 Determines the minimum page order for slabs. Must be
3970 lower than slub_max_order.
3971 For more information see Documentation/vm/slub.rst.
3973 slub_nomerge [MM, SLUB]
3974 Same with slab_nomerge. This is supported for legacy.
3975 See slab_nomerge for more information.
3978 Format: <io1>[,<io2>[,...,<io8>]]
3980 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3981 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3982 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3983 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3984 smsc-ircc2.ircc_irq= [HW] IRQ line
3985 smsc-ircc2.ircc_dma= [HW] DMA channel
3986 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3987 0: Toshiba Satellite 1800 (GP data pin select)
3988 1: Fast pin select (default)
3991 smt [KNL,S390] Set the maximum number of threads (logical
3992 CPUs) to use per physical CPU on systems capable of
3993 symmetric multithreading (SMT). Will be capped to the
3994 actual hardware limit.
3996 Default: -1 (no limit)
3999 [KNL] Should the soft-lockup detector generate panics.
4002 A nonzero value instructs the soft-lockup detector
4003 to panic the machine when a soft-lockup occurs. This
4004 is also controlled by CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC
4005 which is the respective build-time switch to that
4008 softlockup_all_cpu_backtrace=
4009 [KNL] Should the soft-lockup detector generate
4010 backtraces on all cpus.
4013 sonypi.*= [HW] Sony Programmable I/O Control Device driver
4014 See Documentation/laptops/sonypi.txt
4016 spectre_v2= [X86] Control mitigation of Spectre variant 2
4017 (indirect branch speculation) vulnerability.
4019 on - unconditionally enable
4020 off - unconditionally disable
4021 auto - kernel detects whether your CPU model is
4024 Selecting 'on' will, and 'auto' may, choose a
4025 mitigation method at run time according to the
4026 CPU, the available microcode, the setting of the
4027 CONFIG_RETPOLINE configuration option, and the
4028 compiler with which the kernel was built.
4030 Specific mitigations can also be selected manually:
4032 retpoline - replace indirect branches
4033 retpoline,generic - google's original retpoline
4034 retpoline,amd - AMD-specific minimal thunk
4036 Not specifying this option is equivalent to
4039 spec_store_bypass_disable=
4040 [HW] Control Speculative Store Bypass (SSB) Disable mitigation
4041 (Speculative Store Bypass vulnerability)
4043 Certain CPUs are vulnerable to an exploit against a
4044 a common industry wide performance optimization known
4045 as "Speculative Store Bypass" in which recent stores
4046 to the same memory location may not be observed by
4047 later loads during speculative execution. The idea
4048 is that such stores are unlikely and that they can
4049 be detected prior to instruction retirement at the
4050 end of a particular speculation execution window.
4052 In vulnerable processors, the speculatively forwarded
4053 store can be used in a cache side channel attack, for
4054 example to read memory to which the attacker does not
4055 directly have access (e.g. inside sandboxed code).
4057 This parameter controls whether the Speculative Store
4058 Bypass optimization is used.
4060 on - Unconditionally disable Speculative Store Bypass
4061 off - Unconditionally enable Speculative Store Bypass
4062 auto - Kernel detects whether the CPU model contains an
4063 implementation of Speculative Store Bypass and
4064 picks the most appropriate mitigation. If the
4065 CPU is not vulnerable, "off" is selected. If the
4066 CPU is vulnerable the default mitigation is
4067 architecture and Kconfig dependent. See below.
4068 prctl - Control Speculative Store Bypass per thread
4069 via prctl. Speculative Store Bypass is enabled
4070 for a process by default. The state of the control
4071 is inherited on fork.
4072 seccomp - Same as "prctl" above, but all seccomp threads
4073 will disable SSB unless they explicitly opt out.
4075 Not specifying this option is equivalent to
4076 spec_store_bypass_disable=auto.
4078 Default mitigations:
4079 X86: If CONFIG_SECCOMP=y "seccomp", otherwise "prctl"
4081 spia_io_base= [HW,MTD]
4086 srcutree.counter_wrap_check [KNL]
4087 Specifies how frequently to check for
4088 grace-period sequence counter wrap for the
4089 srcu_data structure's ->srcu_gp_seq_needed field.
4090 The greater the number of bits set in this kernel
4091 parameter, the less frequently counter wrap will
4092 be checked for. Note that the bottom two bits
4095 srcutree.exp_holdoff [KNL]
4096 Specifies how many nanoseconds must elapse
4097 since the end of the last SRCU grace period for
4098 a given srcu_struct until the next normal SRCU
4099 grace period will be considered for automatic
4100 expediting. Set to zero to disable automatic
4103 stack_guard_gap= [MM]
4104 override the default stack gap protection. The value
4105 is in page units and it defines how many pages prior
4106 to (for stacks growing down) resp. after (for stacks
4107 growing up) the main stack are reserved for no other
4108 mapping. Default value is 256 pages.
4111 Enabled the stack tracer on boot up.
4113 stacktrace_filter=[function-list]
4114 [FTRACE] Limit the functions that the stack tracer
4115 will trace at boot up. function-list is a comma separated
4116 list of functions. This list can be changed at run
4117 time by the stack_trace_filter file in the debugfs
4118 tracing directory. Note, this enables stack tracing
4119 and the stacktrace above is not needed.
4123 Set the STI (builtin display/keyboard on the HP-PARISC
4124 machines) console (graphic card) which should be used
4125 as the initial boot-console.
4126 See also comment in drivers/video/console/sticore.c.
4129 See comment in drivers/video/console/sticore.c.
4132 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
4134 sunrpc.min_resvport=
4135 sunrpc.max_resvport=
4137 SunRPC servers often require that client requests
4138 originate from a privileged port (i.e. a port in the
4139 range 0 < portnr < 1024).
4140 An administrator who wishes to reserve some of these
4141 ports for other uses may adjust the range that the
4142 kernel's sunrpc client considers to be privileged
4143 using these two parameters to set the minimum and
4144 maximum port values.
4146 sunrpc.svc_rpc_per_connection_limit=
4148 Limit the number of requests that the server will
4149 process in parallel from a single connection.
4150 The default value is 0 (no limit).
4154 Control how the NFS server code allocates CPUs to
4155 service thread pools. Depending on how many NICs
4156 you have and where their interrupts are bound, this
4157 option will affect which CPUs will do NFS serving.
4158 Note: this parameter cannot be changed while the
4159 NFS server is running.
4161 auto the server chooses an appropriate mode
4162 automatically using heuristics
4163 global a single global pool contains all CPUs
4164 percpu one pool for each CPU
4165 pernode one pool for each NUMA node (equivalent
4166 to global on non-NUMA machines)
4168 sunrpc.tcp_slot_table_entries=
4169 sunrpc.udp_slot_table_entries=
4171 Sets the upper limit on the number of simultaneous
4172 RPC calls that can be sent from the client to a
4173 server. Increasing these values may allow you to
4174 improve throughput, but will also increase the
4175 amount of memory reserved for use by the client.
4177 suspend.pm_test_delay=
4179 Sets the number of seconds to remain in a suspend test
4180 mode before resuming the system (see
4181 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
4182 is set. Default value is 5.
4185 [KNL] Enable accounting of swap in memory resource
4186 controller if no parameter or 1 is given or disable
4187 it if 0 is given (See Documentation/cgroup-v1/memory.txt)
4189 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
4190 Format: { <int> | force | noforce }
4191 <int> -- Number of I/O TLB slabs
4192 force -- force using of bounce buffers even if they
4193 wouldn't be automatically used by the kernel
4194 noforce -- Never use bounce buffers (for debugging)
4198 sysfs.deprecated=0|1 [KNL]
4199 Enable/disable old style sysfs layout for old udev
4200 on older distributions. When this option is enabled
4201 very new udev will not work anymore. When this option
4202 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
4203 in older udev will not work anymore.
4204 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
4205 the kernel configuration.
4207 sysrq_always_enabled
4209 Ignore sysrq setting - this boot parameter will
4210 neutralize any effect of /proc/sys/kernel/sysrq.
4211 Useful for debugging.
4213 tcpmhash_entries= [KNL,NET]
4214 Set the number of tcp_metrics_hash slots.
4215 Default value is 8192 or 16384 depending on total
4216 ram pages. This is used to specify the TCP metrics
4217 cache size. See Documentation/networking/ip-sysctl.txt
4218 "tcp_no_metrics_save" section for more details.
4222 test_suspend= [SUSPEND][,N]
4223 Specify "mem" (for Suspend-to-RAM) or "standby" (for
4224 standby suspend) or "freeze" (for suspend type freeze)
4225 as the system sleep state during system startup with
4226 the optional capability to repeat N number of times.
4227 The system is woken from this state using a
4228 wakeup-capable RTC alarm.
4230 thash_entries= [KNL,NET]
4231 Set number of hash buckets for TCP connection
4233 thermal.act= [HW,ACPI]
4234 -1: disable all active trip points in all thermal zones
4235 <degrees C>: override all lowest active trip points
4237 thermal.crt= [HW,ACPI]
4238 -1: disable all critical trip points in all thermal zones
4239 <degrees C>: override all critical trip points
4241 thermal.nocrt= [HW,ACPI]
4242 Set to disable actions on ACPI thermal zone
4243 critical and hot trip points.
4245 thermal.off= [HW,ACPI]
4246 1: disable ACPI thermal control
4248 thermal.psv= [HW,ACPI]
4249 -1: disable all passive trip points
4250 <degrees C>: override all passive trip points to this
4253 thermal.tzp= [HW,ACPI]
4254 Specify global default ACPI thermal zone polling rate
4255 <deci-seconds>: poll all this frequency
4256 0: no polling (default)
4259 Force threading of all interrupt handlers except those
4260 marked explicitly IRQF_NO_THREAD.
4263 Enable the Transcendent memory driver if built-in.
4265 tmem.cleancache=0|1 [KNL, XEN]
4266 Default is on (1). Disable the usage of the cleancache
4267 API to send anonymous pages to the hypervisor.
4269 tmem.frontswap=0|1 [KNL, XEN]
4270 Default is on (1). Disable the usage of the frontswap
4271 API to send swap pages to the hypervisor. If disabled
4272 the selfballooning and selfshrinking are force disabled.
4274 tmem.selfballooning=0|1 [KNL, XEN]
4275 Default is on (1). Disable the driving of swap pages
4278 tmem.selfshrinking=0|1 [KNL, XEN]
4279 Default is on (1). Partial swapoff that immediately
4280 transfers pages from Xen hypervisor back to the
4281 kernel based on different criteria.
4285 Specify if the kernel should make use of the cpu
4286 topology information if the hardware supports this.
4287 The scheduler will make use of this information and
4288 e.g. base its process migration decisions on it.
4291 topology_updates= [KNL, PPC, NUMA]
4293 Specify if the kernel should ignore (off)
4294 topology updates sent by the hypervisor to this
4299 tpm_suspend_pcr=[HW,TPM]
4300 Format: integer pcr id
4301 Specify that at suspend time, the tpm driver
4302 should extend the specified pcr with zeros,
4303 as a workaround for some chips which fail to
4304 flush the last written pcr on TPM_SaveState.
4305 This will guarantee that all the other pcrs
4308 trace_buf_size=nn[KMG]
4309 [FTRACE] will set tracing buffer size on each cpu.
4311 trace_event=[event-list]
4312 [FTRACE] Set and start specified trace events in order
4313 to facilitate early boot debugging. The event-list is a
4314 comma separated list of trace events to enable. See
4315 also Documentation/trace/events.txt
4317 trace_options=[option-list]
4318 [FTRACE] Enable or disable tracer options at boot.
4319 The option-list is a comma delimited list of options
4320 that can be enabled or disabled just as if you were
4321 to echo the option name into
4323 /sys/kernel/debug/tracing/trace_options
4325 For example, to enable stacktrace option (to dump the
4326 stack trace of each event), add to the command line:
4328 trace_options=stacktrace
4330 See also Documentation/trace/ftrace.txt "trace options"
4334 Have the tracepoints sent to printk as well as the
4335 tracing ring buffer. This is useful for early boot up
4336 where the system hangs or reboots and does not give the
4337 option for reading the tracing buffer or performing a
4338 ftrace_dump_on_oops.
4340 To turn off having tracepoints sent to printk,
4341 echo 0 > /proc/sys/kernel/tracepoint_printk
4342 Note, echoing 1 into this file without the
4343 tracepoint_printk kernel cmdline option has no effect.
4347 Having tracepoints sent to printk() and activating high
4348 frequency tracepoints such as irq or sched, can cause
4349 the system to live lock.
4352 [FTRACE] enable this option to disable tracing when a
4353 warning is hit. This turns off "tracing_on". Tracing can
4354 be enabled again by echoing '1' into the "tracing_on"
4355 file located in /sys/kernel/debug/tracing/
4357 This option is useful, as it disables the trace before
4358 the WARNING dump is called, which prevents the trace to
4359 be filled with content caused by the warning output.
4361 This option can also be set at run time via the sysctl
4362 option: kernel/traceoff_on_warning
4364 transparent_hugepage=
4366 Format: [always|madvise|never]
4367 Can be used to control the default behavior of the system
4368 with respect to transparent hugepages.
4369 See Documentation/admin-guide/mm/transhuge.rst
4372 tsc= Disable clocksource stability checks for TSC.
4374 [x86] reliable: mark tsc clocksource as reliable, this
4375 disables clocksource verification at runtime, as well
4376 as the stability checks done at bootup. Used to enable
4377 high-resolution timer mode on older hardware, and in
4378 virtualized environment.
4379 [x86] noirqtime: Do not use TSC to do irq accounting.
4380 Used to run time disable IRQ_TIME_ACCOUNTING on any
4381 platforms where RDTSC is slow and this accounting
4383 [x86] unstable: mark the TSC clocksource as unstable, this
4384 marks the TSC unconditionally unstable at bootup and
4385 avoids any further wobbles once the TSC watchdog notices.
4387 turbografx.map[2|3]= [HW,JOY]
4388 TurboGraFX parallel port interface
4390 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
4391 See also Documentation/input/devices/joystick-parport.rst
4393 udbg-immortal [PPC] When debugging early kernel crashes that
4394 happen after console_init() and before a proper
4395 console driver takes over, this boot options might
4396 help "seeing" what's going on.
4398 uhash_entries= [KNL,NET]
4399 Set number of hash buckets for UDP/UDP-Lite connections
4402 [USB] Ignore overcurrent events (default N).
4403 Some badly-designed motherboards generate lots of
4404 bogus events, for ports that aren't wired to
4405 anything. Set this parameter to avoid log spamming.
4406 Note that genuine overcurrent events won't be
4410 [X86] Cause panic on unknown NMI.
4412 usbcore.authorized_default=
4413 [USB] Default USB device authorization:
4414 (default -1 = authorized except for wireless USB,
4415 0 = not authorized, 1 = authorized)
4417 usbcore.autosuspend=
4418 [USB] The autosuspend time delay (in seconds) used
4419 for newly-detected USB devices (default 2). This
4420 is the time required before an idle device will be
4421 autosuspended. Devices for which the delay is set
4422 to a negative value won't be autosuspended at all.
4424 usbcore.usbfs_snoop=
4425 [USB] Set to log all usbfs traffic (default 0 = off).
4427 usbcore.usbfs_snoop_max=
4428 [USB] Maximum number of bytes to snoop in each URB
4431 usbcore.blinkenlights=
4432 [USB] Set to cycle leds on hubs (default 0 = off).
4434 usbcore.old_scheme_first=
4435 [USB] Start with the old device initialization
4436 scheme (default 0 = off).
4438 usbcore.usbfs_memory_mb=
4439 [USB] Memory limit (in MB) for buffers allocated by
4440 usbfs (default = 16, 0 = max = 2047).
4442 usbcore.use_both_schemes=
4443 [USB] Try the other device initialization scheme
4444 if the first one fails (default 1 = enabled).
4446 usbcore.initial_descriptor_timeout=
4447 [USB] Specifies timeout for the initial 64-byte
4448 USB_REQ_GET_DESCRIPTOR request in milliseconds
4449 (default 5000 = 5.0 seconds).
4451 usbcore.nousb [USB] Disable the USB subsystem
4454 [USB] A list of quirk entries to augment the built-in
4455 usb core quirk list. List entries are separated by
4456 commas. Each entry has the form
4457 VendorID:ProductID:Flags. The IDs are 4-digit hex
4458 numbers and Flags is a set of letters. Each letter
4459 will change the built-in quirk; setting it if it is
4460 clear and clearing it if it is set. The letters have
4461 the following meanings:
4462 a = USB_QUIRK_STRING_FETCH_255 (string
4463 descriptors must not be fetched using
4465 b = USB_QUIRK_RESET_RESUME (device can't resume
4466 correctly so reset it instead);
4467 c = USB_QUIRK_NO_SET_INTF (device can't handle
4468 Set-Interface requests);
4469 d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
4470 handle its Configuration or Interface
4472 e = USB_QUIRK_RESET (device can't be reset
4473 (e.g morph devices), don't use reset);
4474 f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
4475 more interface descriptions than the
4476 bNumInterfaces count, and can't handle
4477 talking to these interfaces);
4478 g = USB_QUIRK_DELAY_INIT (device needs a pause
4479 during initialization, after we read
4480 the device descriptor);
4481 h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
4482 high speed and super speed interrupt
4483 endpoints, the USB 2.0 and USB 3.0 spec
4484 require the interval in microframes (1
4485 microframe = 125 microseconds) to be
4486 calculated as interval = 2 ^
4488 Devices with this quirk report their
4489 bInterval as the result of this
4490 calculation instead of the exponent
4491 variable used in the calculation);
4492 i = USB_QUIRK_DEVICE_QUALIFIER (device can't
4493 handle device_qualifier descriptor
4495 j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
4496 generates spurious wakeup, ignore
4497 remote wakeup capability);
4498 k = USB_QUIRK_NO_LPM (device can't handle Link
4500 l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
4501 (Device reports its bInterval as linear
4502 frames instead of the USB 2.0
4504 m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
4505 to be disconnected before suspend to
4506 prevent spurious wakeup);
4507 n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
4508 pause after every control message);
4509 Example: quirks=0781:5580:bk,0a5c:5834:gij
4512 [USBHID] The interval which mice are to be polled at.
4515 [USBHID] The interval which joysticks are to be polled at.
4518 [USBHID] The interval which keyboards are to be polled at.
4520 usb-storage.delay_use=
4521 [UMS] The delay in seconds before a new device is
4522 scanned for Logical Units (default 1).
4525 [UMS] A list of quirks entries to supplement or
4526 override the built-in unusual_devs list. List
4527 entries are separated by commas. Each entry has
4528 the form VID:PID:Flags where VID and PID are Vendor
4529 and Product ID values (4-digit hex numbers) and
4530 Flags is a set of characters, each corresponding
4531 to a common usb-storage quirk flag as follows:
4532 a = SANE_SENSE (collect more than 18 bytes
4534 b = BAD_SENSE (don't collect more than 18
4535 bytes of sense data);
4536 c = FIX_CAPACITY (decrease the reported
4537 device capacity by one sector);
4538 d = NO_READ_DISC_INFO (don't use
4539 READ_DISC_INFO command);
4540 e = NO_READ_CAPACITY_16 (don't use
4541 READ_CAPACITY_16 command);
4542 f = NO_REPORT_OPCODES (don't use report opcodes
4544 g = MAX_SECTORS_240 (don't transfer more than
4545 240 sectors at a time, uas only);
4546 h = CAPACITY_HEURISTICS (decrease the
4547 reported device capacity by one
4548 sector if the number is odd);
4549 i = IGNORE_DEVICE (don't bind to this
4551 j = NO_REPORT_LUNS (don't use report luns
4553 l = NOT_LOCKABLE (don't try to lock and
4554 unlock ejectable media);
4555 m = MAX_SECTORS_64 (don't transfer more
4556 than 64 sectors = 32 KB at a time);
4557 n = INITIAL_READ10 (force a retry of the
4558 initial READ(10) command);
4559 o = CAPACITY_OK (accept the capacity
4560 reported by the device);
4561 p = WRITE_CACHE (the device cache is ON
4563 r = IGNORE_RESIDUE (the device reports
4564 bogus residue values);
4565 s = SINGLE_LUN (the device has only one
4567 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4568 commands, uas only);
4569 u = IGNORE_UAS (don't bind to the uas driver);
4570 w = NO_WP_DETECT (don't test whether the
4571 medium is write-protected).
4572 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
4573 even if the device claims no cache)
4574 Example: quirks=0419:aaf5:rl,0421:0433:rc
4576 user_debug= [KNL,ARM]
4578 See arch/arm/Kconfig.debug help text.
4579 1 - undefined instruction events
4581 4 - invalid data aborts
4584 Example: user_debug=31
4587 [X86] Flags controlling user PTE allocations.
4589 nohigh = do not allocate PTE pages in
4590 HIGHMEM regardless of setting
4594 On X86_32, this is an alias for vdso32=. Otherwise:
4596 vdso=1: enable VDSO (the default)
4597 vdso=0: disable VDSO mapping
4599 vdso32= [X86] Control the 32-bit vDSO
4600 vdso32=1: enable 32-bit VDSO
4601 vdso32=0 or vdso32=2: disable 32-bit VDSO
4603 See the help text for CONFIG_COMPAT_VDSO for more
4604 details. If CONFIG_COMPAT_VDSO is set, the default is
4605 vdso32=0; otherwise, the default is vdso32=1.
4607 For compatibility with older kernels, vdso32=2 is an
4610 Try vdso32=0 if you encounter an error that says:
4611 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
4614 vector=percpu: enable percpu vector domain
4616 video= [FB] Frame buffer configuration
4617 See Documentation/fb/modedb.txt.
4619 video.brightness_switch_enabled= [0,1]
4620 If set to 1, on receiving an ACPI notify event
4621 generated by hotkey, video driver will adjust brightness
4622 level and then send out the event to user space through
4623 the allocated input device; If set to 0, video driver
4624 will only send out the event without touching backlight
4629 [VMMIO] Memory mapped virtio (platform) device.
4631 <size>@<baseaddr>:<irq>[:<id>]
4633 <size> := size (can use standard suffixes
4635 <baseaddr> := physical base address
4636 <irq> := interrupt number (as passed to
4638 <id> := (optional) platform device id
4640 virtio_mmio.device=1K@0x100b0000:48:7
4642 Can be used multiple times for multiple devices.
4644 vga= [BOOT,X86-32] Select a particular video mode
4645 See Documentation/x86/boot.txt and
4646 Documentation/svga.txt.
4647 Use vga=ask for menu.
4648 This is actually a boot loader parameter; the value is
4649 passed to the kernel using a special protocol.
4651 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4652 size of <nn>. This can be used to increase the
4653 minimum size (128MB on x86). It can also be used to
4654 decrease the size and leave more room for directly
4657 vmcp_cma=nn[MG] [KNL,S390]
4658 Sets the memory size reserved for contiguous memory
4659 allocations for the vmcp device driver.
4661 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4664 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4667 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4671 Controls the behavior of vsyscalls (i.e. calls to
4672 fixed addresses of 0xffffffffff600x00 from legacy
4673 code). Most statically-linked binaries and older
4674 versions of glibc use these calls. Because these
4675 functions are at fixed addresses, they make nice
4676 targets for exploits that can control RIP.
4678 emulate [default] Vsyscalls turn into traps and are
4679 emulated reasonably safely.
4681 native Vsyscalls are native syscall instructions.
4682 This is a little bit faster than trapping
4683 and makes a few dynamic recompilers work
4684 better than they would in emulation mode.
4685 It also makes exploits much easier to write.
4687 none Vsyscalls don't work at all. This makes
4688 them quite hard to use for exploits but
4689 might break your system.
4691 vt.color= [VT] Default text color.
4692 Format: 0xYX, X = foreground, Y = background.
4693 Default: 0x07 = light gray on black.
4695 vt.cur_default= [VT] Default cursor shape.
4696 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4697 the parameters of the <Esc>[?A;B;Cc escape sequence;
4698 see VGA-softcursor.txt. Default: 2 = underline.
4700 vt.default_blu= [VT]
4701 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4702 Change the default blue palette of the console.
4703 This is a 16-member array composed of values
4706 vt.default_grn= [VT]
4707 Format: <green0>,<green1>,<green2>,...,<green15>
4708 Change the default green palette of the console.
4709 This is a 16-member array composed of values
4712 vt.default_red= [VT]
4713 Format: <red0>,<red1>,<red2>,...,<red15>
4714 Change the default red palette of the console.
4715 This is a 16-member array composed of values
4721 Set system-wide default UTF-8 mode for all tty's.
4722 Default is 1, i.e. UTF-8 mode is enabled for all
4723 newly opened terminals.
4725 vt.global_cursor_default=
4728 Set system-wide default for whether a cursor
4729 is shown on new VTs. Default is -1,
4730 i.e. cursors will be created by default unless
4731 overridden by individual drivers. 0 will hide
4732 cursors, 1 will display them.
4734 vt.italic= [VT] Default color for italic text; 0-15.
4737 vt.underline= [VT] Default color for underlined text; 0-15.
4740 watchdog timers [HW,WDT] For information on watchdog timers,
4741 see Documentation/watchdog/watchdog-parameters.txt
4742 or other driver-specific files in the
4743 Documentation/watchdog/ directory.
4745 workqueue.watchdog_thresh=
4746 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4747 warn stall conditions and dump internal state to
4748 help debugging. 0 disables workqueue stall
4749 detection; otherwise, it's the stall threshold
4750 duration in seconds. The default value is 30 and
4751 it can be updated at runtime by writing to the
4752 corresponding sysfs file.
4754 workqueue.disable_numa
4755 By default, all work items queued to unbound
4756 workqueues are affine to the NUMA nodes they're
4757 issued on, which results in better behavior in
4758 general. If NUMA affinity needs to be disabled for
4759 whatever reason, this option can be used. Note
4760 that this also can be controlled per-workqueue for
4761 workqueues visible under /sys/bus/workqueue/.
4763 workqueue.power_efficient
4764 Per-cpu workqueues are generally preferred because
4765 they show better performance thanks to cache
4766 locality; unfortunately, per-cpu workqueues tend to
4767 be more power hungry than unbound workqueues.
4769 Enabling this makes the per-cpu workqueues which
4770 were observed to contribute significantly to power
4771 consumption unbound, leading to measurably lower
4772 power usage at the cost of small performance
4775 The default value of this parameter is determined by
4776 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4778 workqueue.debug_force_rr_cpu
4779 Workqueue used to implicitly guarantee that work
4780 items queued without explicit CPU specified are put
4781 on the local CPU. This guarantee is no longer true
4782 and while local CPU is still preferred work items
4783 may be put on foreign CPUs. This debug option
4784 forces round-robin CPU selection to flush out
4785 usages which depend on the now broken guarantee.
4786 When enabled, memory and cache locality will be
4789 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4790 default x2apic cluster mode on platforms
4793 x86_intel_mid_timer= [X86-32,APBT]
4794 Choose timer option for x86 Intel MID platform.
4795 Two valid options are apbt timer only and lapic timer
4796 plus one apbt timer for broadcast timer.
4797 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4799 xen_512gb_limit [KNL,X86-64,XEN]
4800 Restricts the kernel running paravirtualized under Xen
4801 to use only up to 512 GB of RAM. The reason to do so is
4802 crash analysis tools and Xen tools for doing domain
4803 save/restore/migration must be enabled to handle larger
4806 xen_emul_unplug= [HW,X86,XEN]
4807 Unplug Xen emulated devices
4808 Format: [unplug0,][unplug1]
4809 ide-disks -- unplug primary master IDE devices
4810 aux-ide-disks -- unplug non-primary-master IDE devices
4811 nics -- unplug network devices
4812 all -- unplug all emulated devices (NICs and IDE disks)
4813 unnecessary -- unplugging emulated devices is
4814 unnecessary even if the host did not respond to
4816 never -- do not unplug even if version check succeeds
4818 xen_nopvspin [X86,XEN]
4819 Disables the ticketlock slowpath using Xen PV
4823 Disables the PV optimizations forcing the HVM guest to
4824 run as generic HVM guest with no PV drivers.
4826 xirc2ps_cs= [NET,PCMCIA]
4828 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
projects / linux-2.6-microblaze.git / blob