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-configuration.rst
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 while 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.
465 [NET] Specifies amount of time (in seconds) that
466 the kernel should wait for a network carrier. By default
467 it waits 120 seconds.
469 ca_keys= [KEYS] This parameter identifies a specific key(s) on
470 the system trusted keyring to be used for certificate
472 format: { id:<keyid> | builtin }
474 cca= [MIPS] Override the kernel pages' cache coherency
475 algorithm. Accepted values range from 0 to 7
476 inclusive. See arch/mips/include/asm/pgtable-bits.h
477 for platform specific values (SB1, Loongson3 and
480 ccw_timeout_log [S390]
481 See Documentation/s390/CommonIO for details.
483 cgroup_disable= [KNL] Disable a particular controller
484 Format: {name of the controller(s) to disable}
485 The effects of cgroup_disable=foo are:
486 - foo isn't auto-mounted if you mount all cgroups in
488 - foo isn't visible as an individually mountable
490 {Currently only "memory" controller deal with this and
491 cut the overhead, others just disable the usage. So
492 only cgroup_disable=memory is actually worthy}
494 cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1
495 Format: { { controller | "all" | "named" }
496 [,{ controller | "all" | "named" }...] }
497 Like cgroup_disable, but only applies to cgroup v1;
498 the blacklisted controllers remain available in cgroup2.
499 "all" blacklists all controllers and "named" disables
500 named mounts. Specifying both "all" and "named" disables
503 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
505 nosocket -- Disable socket memory accounting.
506 nokmem -- Disable kernel memory accounting.
508 checkreqprot [SELINUX] Set initial checkreqprot flag value.
509 Format: { "0" | "1" }
510 See security/selinux/Kconfig help text.
511 0 -- check protection applied by kernel (includes
512 any implied execute protection).
513 1 -- check protection requested by application.
514 Default value is set via a kernel config option.
515 Value can be changed at runtime via
516 /selinux/checkreqprot.
519 See Documentation/s390/CommonIO for details.
522 Prevents the clock framework from automatically gating
523 clocks that have not been explicitly enabled by a Linux
524 device driver but are enabled in hardware at reset or
525 by the bootloader/firmware. Note that this does not
526 force such clocks to be always-on nor does it reserve
527 those clocks in any way. This parameter is useful for
528 debug and development, but should not be needed on a
529 platform with proper driver support. For more
530 information, see Documentation/driver-api/clk.rst.
532 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
534 Forces specified clocksource (if available) to be used
535 when calculating gettimeofday(). If specified
536 clocksource is not available, it defaults to PIT.
537 Format: { pit | tsc | cyclone | pmtmr }
539 clocksource= Override the default clocksource
541 Override the default clocksource and use the clocksource
542 with the name specified.
543 Some clocksource names to choose from, depending on
545 [all] jiffies (this is the base, fallback clocksource)
547 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
548 pxa_timer,timer3,32k_counter,timer0_1
549 [X86-32] pit,hpet,tsc;
550 scx200_hrt on Geode; cyclone on IBM x440
558 clocksource.arm_arch_timer.evtstrm=
561 Enable/disable the eventstream feature of the ARM
562 architected timer so that code using WFE-based polling
563 loops can be debugged more effectively on production
566 clearcpuid=BITNUM [X86]
567 Disable CPUID feature X for the kernel. See
568 arch/x86/include/asm/cpufeatures.h for the valid bit
569 numbers. Note the Linux specific bits are not necessarily
570 stable over kernel options, but the vendor specific
572 Also note that user programs calling CPUID directly
573 or using the feature without checking anything
574 will still see it. This just prevents it from
575 being used by the kernel or shown in /proc/cpuinfo.
576 Also note the kernel might malfunction if you disable
579 cma=nn[MG]@[start[MG][-end[MG]]]
581 Sets the size of kernel global memory area for
582 contiguous memory allocations and optionally the
583 placement constraint by the physical address range of
584 memory allocations. A value of 0 disables CMA
585 altogether. For more information, see
586 include/linux/dma-contiguous.h
588 cmo_free_hint= [PPC] Format: { yes | no }
589 Specify whether pages are marked as being inactive
590 when they are freed. This is used in CMO environments
591 to determine OS memory pressure for page stealing by
595 coherent_pool=nn[KMG] [ARM,KNL]
596 Sets the size of memory pool for coherent, atomic dma
597 allocations, by default set to 256K.
599 com20020= [HW,NET] ARCnet - COM20020 chipset
601 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
603 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
607 ARCnet - COM90xx chipset (memory-mapped buffers)
608 Format: <io>[,<irq>[,<memstart>]]
610 condev= [HW,S390] console device
613 console= [KNL] Output console device and options.
615 tty<n> Use the virtual console device <n>.
619 Use the specified serial port. The options are of
620 the form "bbbbpnf", where "bbbb" is the baud rate,
621 "p" is parity ("n", "o", or "e"), "n" is number of
622 bits, and "f" is flow control ("r" for RTS or
623 omit it). Default is "9600n8".
625 See Documentation/admin-guide/serial-console.rst for more
627 Documentation/networking/netconsole.txt for an
630 uart[8250],io,<addr>[,options]
631 uart[8250],mmio,<addr>[,options]
632 uart[8250],mmio16,<addr>[,options]
633 uart[8250],mmio32,<addr>[,options]
634 uart[8250],0x<addr>[,options]
635 Start an early, polled-mode console on the 8250/16550
636 UART at the specified I/O port or MMIO address,
637 switching to the matching ttyS device later.
638 MMIO inter-register address stride is either 8-bit
639 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
640 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
641 to be equivalent to 'mmio'. 'options' are specified in
642 the same format described for ttyS above; if unspecified,
643 the h/w is not re-initialized.
645 hvc<n> Use the hypervisor console device <n>. This is for
646 both Xen and PowerPC hypervisors.
648 If the device connected to the port is not a TTY but a braille
649 device, prepend "brl," before the device type, for instance
651 For now, only VisioBraille is supported.
654 [KNL] Change console messages format
656 By default we print messages on consoles in
657 "[time stamp] text\n" format (time stamp may not be
658 printed, depending on CONFIG_PRINTK_TIME or
659 `printk_time' param).
661 Switch to syslog format: "<%u>[time stamp] text\n"
662 IOW, each message will have a facility and loglevel
663 prefix. The format is similar to one used by syslog()
664 syscall, or to executing "dmesg -S --raw" or to reading
667 consoleblank= [KNL] The console blank (screen saver) timeout in
668 seconds. A value of 0 disables the blank timer.
672 [KNL] Change the default value for
673 /proc/<pid>/coredump_filter.
674 See also Documentation/filesystems/proc.txt.
676 coresight_cpu_debug.enable
679 Enable/disable the CPU sampling based debugging.
680 0: default value, disable debugging
681 1: enable debugging at boot time
683 cpuidle.off=1 [CPU_IDLE]
684 disable the cpuidle sub-system
687 [CPU_IDLE] Name of the cpuidle governor to use.
689 cpufreq.off=1 [CPU_FREQ]
690 disable the cpufreq sub-system
693 [X86] Delay for N microsec between assert and de-assert
694 of APIC INIT to start processors. This delay occurs
695 on every CPU online, such as boot, and resume from suspend.
698 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
700 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
702 crashkernel=size[KMG][@offset[KMG]]
703 [KNL] Using kexec, Linux can switch to a 'crash kernel'
704 upon panic. This parameter reserves the physical
705 memory region [offset, offset + size] for that kernel
706 image. If '@offset' is omitted, then a suitable offset
707 is selected automatically. Check
708 Documentation/kdump/kdump.txt for further details.
710 crashkernel=range1:size1[,range2:size2,...][@offset]
711 [KNL] Same as above, but depends on the memory
712 in the running system. The syntax of range is
713 start-[end] where start and end are both
714 a memory unit (amount[KMG]). See also
715 Documentation/kdump/kdump.txt for an example.
717 crashkernel=size[KMG],high
718 [KNL, x86_64] range could be above 4G. Allow kernel
719 to allocate physical memory region from top, so could
720 be above 4G if system have more than 4G ram installed.
721 Otherwise memory region will be allocated below 4G, if
723 It will be ignored if crashkernel=X is specified.
724 crashkernel=size[KMG],low
725 [KNL, x86_64] range under 4G. When crashkernel=X,high
726 is passed, kernel could allocate physical memory region
727 above 4G, that cause second kernel crash on system
728 that require some amount of low memory, e.g. swiotlb
729 requires at least 64M+32K low memory, also enough extra
730 low memory is needed to make sure DMA buffers for 32-bit
731 devices won't run out. Kernel would try to allocate at
732 at least 256M below 4G automatically.
733 This one let user to specify own low range under 4G
734 for second kernel instead.
735 0: to disable low allocation.
736 It will be ignored when crashkernel=X,high is not used
737 or memory reserved is below 4G.
740 [KNL] Disable crypto self-tests
745 cs89x0_media= [HW,NET]
746 Format: { rj45 | aui | bnc }
749 See header of drivers/s390/block/dasd_devmap.c.
751 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
752 (one device per port)
753 Format: <port#>,<type>
754 See also Documentation/input/devices/joystick-parport.rst
756 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
758 Documentation/admin-guide/dynamic-debug-howto.rst for
759 details. Deprecated, see dyndbg.
761 debug [KNL] Enable kernel debugging (events log level).
764 [KNL] Enable printing [hashed] pointers early in the
765 boot sequence. If enabled, we use a weak hash instead
766 of siphash to hash pointers. Use this option if you are
767 seeing instances of '(___ptrval___)') and need to see a
768 value (hashed pointer) instead. Cryptographically
769 insecure, please do not use on production kernels.
772 [KNL] verbose self-tests
774 Print debugging info while doing the locking API
776 We default to 0 (no extra messages), setting it to
777 1 will print _a lot_ more information - normally
778 only useful to kernel developers.
780 debug_objects [KNL] Enable object debugging
783 [KNL] Disable object debugging
785 debug_guardpage_minorder=
786 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
787 parameter allows control of the order of pages that will
788 be intentionally kept free (and hence protected) by the
789 buddy allocator. Bigger value increase the probability
790 of catching random memory corruption, but reduce the
791 amount of memory for normal system use. The maximum
792 possible value is MAX_ORDER/2. Setting this parameter
793 to 1 or 2 should be enough to identify most random
794 memory corruption problems caused by bugs in kernel or
795 driver code when a CPU writes to (or reads from) a
796 random memory location. Note that there exists a class
797 of memory corruptions problems caused by buggy H/W or
798 F/W or by drivers badly programing DMA (basically when
799 memory is written at bus level and the CPU MMU is
800 bypassed) which are not detectable by
801 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
802 tracking down these problems.
805 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
806 parameter enables the feature at boot time. In
807 default, it is disabled. We can avoid allocating huge
808 chunk of memory for debug pagealloc if we don't enable
809 it at boot time and the system will work mostly same
810 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
811 on: enable the feature
813 debugpat [X86] Enable PAT debugging
815 decnet.addr= [HW,NET]
816 Format: <area>[,<node>]
817 See also Documentation/networking/decnet.txt.
820 [same as hugepagesz=] The size of the default
821 HugeTLB page size. This is the size represented by
822 the legacy /proc/ hugepages APIs, used for SHM, and
823 default size when mounting hugetlbfs filesystems.
824 Defaults to the default architecture's huge page size
827 deferred_probe_timeout=
828 [KNL] Debugging option to set a timeout in seconds for
829 deferred probe to give up waiting on dependencies to
830 probe. Only specific dependencies (subsystems or
831 drivers) that have opted in will be ignored. A timeout of 0
832 will timeout at the end of initcalls. This option will also
833 dump out devices still on the deferred probe list after
837 Set number of hash buckets for dentry cache.
839 disable_1tb_segments [PPC]
840 Disables the use of 1TB hash page table segments. This
841 causes the kernel to fall back to 256MB segments which
842 can be useful when debugging issues that require an SLB
846 See Documentation/networking/ipv6.txt.
849 [KNL] Under CONFIG_HARDENED_USERCOPY, whether
850 hardening is enabled for this boot. Hardened
851 usercopy checking is used to protect the kernel
852 from reading or writing beyond known memory
853 allocation boundaries as a proactive defense
854 against bounds-checking flaws in the kernel's
855 copy_to_user()/copy_from_user() interface.
856 on Perform hardened usercopy checks (default).
857 off Disable hardened usercopy checks.
860 Disable RADIX MMU mode on POWER9
862 disable_cpu_apicid= [X86,APIC,SMP]
864 The number of initial APIC ID for the
865 corresponding CPU to be disabled at boot,
866 mostly used for the kdump 2nd kernel to
867 disable BSP to wake up multiple CPUs without
868 causing system reset or hang due to sending
871 perf_v4_pmi= [X86,INTEL]
873 Disable Intel PMU counter freezing feature.
874 The feature only exists starting from
875 Arch Perfmon v4 (Skylake and newer).
877 disable_ddw [PPC/PSERIES]
878 Disable Dynamic DMA Window support. Use this if
879 to workaround buggy firmware.
882 See Documentation/networking/ipv6.txt.
884 disable_mtrr_cleanup [X86]
885 The kernel tries to adjust MTRR layout from continuous
886 to discrete, to make X server driver able to add WB
887 entry later. This parameter disables that.
889 disable_mtrr_trim [X86, Intel and AMD only]
890 By default the kernel will trim any uncacheable
891 memory out of your available memory pool based on
892 MTRR settings. This parameter disables that behavior,
893 possibly causing your machine to run very slowly.
895 disable_timer_pin_1 [X86]
896 Disable PIN 1 of APIC timer
897 Can be useful to work around chipset bugs.
899 dis_ucode_ldr [X86] Disable the microcode loader.
901 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
902 this option disables the debugging code at boot.
904 dma_debug_entries=<number>
905 This option allows to tune the number of preallocated
906 entries for DMA-API debugging code. One entry is
907 required per DMA-API allocation. Use this if the
908 DMA-API debugging code disables itself because the
909 architectural default is too low.
911 dma_debug_driver=<driver_name>
912 With this option the DMA-API debugging driver
913 filter feature can be enabled at boot time. Just
914 pass the driver to filter for as the parameter.
915 The filter can be disabled or changed to another
916 driver later using sysfs.
918 driver_async_probe= [KNL]
919 List of driver names to be probed asynchronously.
920 Format: <driver_name1>,<driver_name2>...
922 drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
923 Broken monitors, graphic adapters, KVMs and EDIDless
924 panels may send no or incorrect EDID data sets.
925 This parameter allows to specify an EDID data sets
926 in the /lib/firmware directory that are used instead.
927 Generic built-in EDID data sets are used, if one of
928 edid/1024x768.bin, edid/1280x1024.bin,
929 edid/1680x1050.bin, or edid/1920x1080.bin is given
930 and no file with the same name exists. Details and
931 instructions how to build your own EDID data are
932 available in Documentation/EDID/HOWTO.txt. An EDID
933 data set will only be used for a particular connector,
934 if its name and a colon are prepended to the EDID
935 name. Each connector may use a unique EDID data
936 set by separating the files with a comma. An EDID
937 data set with no connector name will be used for
938 any connectors not explicitly specified.
943 Format: {"off" | "known"}
944 Control how the dt_cpu_ftrs device-tree binding is
945 used for CPU feature discovery and setup (if it
947 off: Do not use it, fall back to legacy cpu table.
948 known: Do not pass through unknown features to guests
949 or userspace, only those that the kernel is aware of.
951 dump_apple_properties [X86]
952 Dump name and content of EFI device properties on
953 x86 Macs. Useful for driver authors to determine
954 what data is available or for reverse-engineering.
956 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
957 module.dyndbg[="val"]
958 Enable debug messages at boot time. See
959 Documentation/admin-guide/dynamic-debug-howto.rst
962 nompx [X86] Disables Intel Memory Protection Extensions.
963 See Documentation/x86/intel_mpx.txt for more
964 information about the feature.
966 nopku [X86] Disable Memory Protection Keys CPU feature found
969 module.async_probe [KNL]
970 Enable asynchronous probe on this module.
972 early_ioremap_debug [KNL]
973 Enable debug messages in early_ioremap support. This
974 is useful for tracking down temporary early mappings
975 which are not unmapped.
977 earlycon= [KNL] Output early console device and options.
979 [ARM64] The early console is determined by the
980 stdout-path property in device tree's chosen node,
981 or determined by the ACPI SPCR table.
983 [X86] When used with no options the early console is
984 determined by the ACPI SPCR table.
986 cdns,<addr>[,options]
987 Start an early, polled-mode console on a Cadence
988 (xuartps) serial port at the specified address. Only
989 supported option is baud rate. If baud rate is not
990 specified, the serial port must already be setup and
993 uart[8250],io,<addr>[,options]
994 uart[8250],mmio,<addr>[,options]
995 uart[8250],mmio32,<addr>[,options]
996 uart[8250],mmio32be,<addr>[,options]
997 uart[8250],0x<addr>[,options]
998 Start an early, polled-mode console on the 8250/16550
999 UART at the specified I/O port or MMIO address.
1000 MMIO inter-register address stride is either 8-bit
1001 (mmio) or 32-bit (mmio32 or mmio32be).
1002 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1003 to be equivalent to 'mmio'. 'options' are specified
1004 in the same format described for "console=ttyS<n>"; if
1005 unspecified, the h/w is not initialized.
1009 Start an early, polled-mode console on a pl011 serial
1010 port at the specified address. The pl011 serial port
1011 must already be setup and configured. Options are not
1012 yet supported. If 'mmio32' is specified, then only
1013 the driver will use only 32-bit accessors to read/write
1014 the device registers.
1017 Start an early, polled-mode console on a meson serial
1018 port at the specified address. The serial port must
1019 already be setup and configured. Options are not yet
1023 Start an early, polled-mode console on an msm serial
1024 port at the specified address. The serial port
1025 must already be setup and configured. Options are not
1028 msm_serial_dm,<addr>
1029 Start an early, polled-mode console on an msm serial
1030 dm port at the specified address. The serial port
1031 must already be setup and configured. Options are not
1035 Start an early, polled-mode console on a serial port
1036 of an Actions Semi SoC, such as S500 or S900, at the
1037 specified address. The serial port must already be
1038 setup and configured. Options are not yet supported.
1041 Start an early, polled-mode console on a serial port
1042 of an RDA Micro SoC, such as RDA8810PL, at the
1043 specified address. The serial port must already be
1044 setup and configured. Options are not yet supported.
1046 smh Use ARM semihosting calls for early console.
1054 Use early console provided by serial driver available
1055 on Samsung SoCs, requires selecting proper type and
1056 a correct base address of the selected UART port. The
1057 serial port must already be setup and configured.
1058 Options are not yet supported.
1061 Start an early, polled-mode console on a lantiq serial
1062 (lqasc) port at the specified address. The serial port
1063 must already be setup and configured. Options are not
1068 Use early console provided by Freescale LP UART driver
1069 found on Freescale Vybrid and QorIQ LS1021A processors.
1070 A valid base address must be provided, and the serial
1071 port must already be setup and configured.
1074 Start an early, polled-mode console on the
1075 Armada 3700 serial port at the specified
1076 address. The serial port must already be setup
1077 and configured. Options are not yet supported.
1080 Start an early, polled-mode console on a Qualcomm
1081 Generic Interface (GENI) based serial port at the
1082 specified address. The serial port must already be
1083 setup and configured. Options are not yet supported.
1086 Start an early, unaccelerated console on the EFI
1087 memory mapped framebuffer (if available). On cache
1088 coherent non-x86 systems that use system memory for
1089 the framebuffer, pass the 'ram' option so that it is
1090 mapped with the correct attributes.
1092 earlyprintk= [X86,SH,ARM,M68k,S390]
1096 earlyprintk=serial[,ttySn[,baudrate]]
1097 earlyprintk=serial[,0x...[,baudrate]]
1098 earlyprintk=ttySn[,baudrate]
1099 earlyprintk=dbgp[debugController#]
1100 earlyprintk=pciserial[,force],bus:device.function[,baudrate]
1101 earlyprintk=xdbc[xhciController#]
1103 earlyprintk is useful when the kernel crashes before
1104 the normal console is initialized. It is not enabled by
1105 default because it has some cosmetic problems.
1107 Append ",keep" to not disable it when the real console
1110 Only one of vga, efi, serial, or usb debug port can
1113 Currently only ttyS0 and ttyS1 may be specified by
1114 name. Other I/O ports may be explicitly specified
1115 on some architectures (x86 and arm at least) by
1116 replacing ttySn with an I/O port address, like this:
1117 earlyprintk=serial,0x1008,115200
1118 You can find the port for a given device in
1119 /proc/tty/driver/serial:
1120 2: uart:ST16650V2 port:00001008 irq:18 ...
1122 Interaction with the standard serial driver is not
1125 The VGA and EFI output is eventually overwritten by
1128 The xen output can only be used by Xen PV guests.
1130 The sclp output can only be used on s390.
1132 The optional "force" to "pciserial" enables use of a
1133 PCI device even when its classcode is not of the
1136 edac_report= [HW,EDAC] Control how to report EDAC event
1137 Format: {"on" | "off" | "force"}
1138 on: enable EDAC to report H/W event. May be overridden
1139 by other higher priority error reporting module.
1140 off: disable H/W event reporting through EDAC.
1141 force: enforce the use of EDAC to report H/W event.
1144 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1147 This is designed to be used in conjunction with
1148 the boot argument: earlyprintk=vga
1151 Format: {"off" | "on" | "skip[mbr]"}
1154 Format: { "old_map", "nochunk", "noruntime", "debug" }
1155 old_map [X86-64]: switch to the old ioremap-based EFI
1156 runtime services mapping. 32-bit still uses this one by
1158 nochunk: disable reading files in "chunks" in the EFI
1159 boot stub, as chunking can cause problems with some
1160 firmware implementations.
1161 noruntime : disable EFI runtime services support
1162 debug: enable misc debug output
1164 efi_no_storage_paranoia [EFI; X86]
1165 Using this parameter you can use more than 50% of
1166 your efi variable storage. Use this parameter only if
1167 you are really sure that your UEFI does sane gc and
1168 fulfills the spec otherwise your board may brick.
1170 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1171 Add arbitrary attribute to specific memory range by
1172 updating original EFI memory map.
1173 Region of memory which aa attribute is added to is
1175 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1176 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1177 attribute is added to range 0x100000000-0x180000000 and
1178 0x10a0000000-0x1120000000.
1180 Using this parameter you can do debugging of EFI memmap
1181 related feature. For example, you can do debugging of
1182 Address Range Mirroring feature even if your box
1185 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1186 that is to be dynamically loaded by Linux. If there are
1187 multiple variables with the same name but with different
1188 vendor GUIDs, all of them will be loaded. See
1189 Documentation/acpi/ssdt-overlays.txt for details.
1192 eisa_irq_edge= [PARISC,HW]
1193 See header of drivers/parisc/eisa.c.
1196 See comment before function elanfreq_setup() in
1197 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1200 Format: {"cfq" | "deadline" | "noop"}
1201 See Documentation/block/cfq-iosched.txt and
1202 Documentation/block/deadline-iosched.txt for details.
1204 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1205 Specifies physical address of start of kernel core
1206 image elf header and optionally the size. Generally
1207 kexec loader will pass this option to capture kernel.
1208 See Documentation/kdump/kdump.txt for details.
1210 enable_mtrr_cleanup [X86]
1211 The kernel tries to adjust MTRR layout from continuous
1212 to discrete, to make X server driver able to add WB
1213 entry later. This parameter enables that.
1215 enable_timer_pin_1 [X86]
1216 Enable PIN 1 of APIC timer
1217 Can be useful to work around chipset bugs
1218 (in particular on some ATI chipsets).
1219 The kernel tries to set a reasonable default.
1221 enforcing [SELINUX] Set initial enforcing status.
1223 See security/selinux/Kconfig help text.
1224 0 -- permissive (log only, no denials).
1225 1 -- enforcing (deny and log).
1227 Value can be changed at runtime via /selinux/enforce.
1230 Disable Error Record Serialization Table (ERST)
1233 ether= [HW,NET] Ethernet cards parameters
1234 This option is obsoleted by the "netdev=" option, which
1235 has equivalent usage. See its documentation for details.
1239 Permit 'security.evm' to be updated regardless of
1240 current integrity status.
1244 fail_make_request=[KNL]
1245 General fault injection mechanism.
1246 Format: <interval>,<probability>,<space>,<times>
1247 See also Documentation/fault-injection/.
1250 See Documentation/blockdev/floppy.txt.
1252 force_pal_cache_flush
1253 [IA-64] Avoid check_sal_cache_flush which may hang on
1254 buggy SAL_CACHE_FLUSH implementations. Using this
1255 parameter will force ia64_sal_cache_flush to call
1256 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1259 Forcefully enable Physical Address Extension (PAE).
1260 Many Pentium M systems disable PAE but may have a
1261 functionally usable PAE implementation.
1262 Warning: use of this parameter will taint the kernel
1263 and may cause unknown problems.
1266 [FTRACE] will set and start the specified tracer
1267 as early as possible in order to facilitate early
1270 ftrace_dump_on_oops[=orig_cpu]
1271 [FTRACE] will dump the trace buffers on oops.
1272 If no parameter is passed, ftrace will dump
1273 buffers of all CPUs, but if you pass orig_cpu, it will
1274 dump only the buffer of the CPU that triggered the
1277 ftrace_filter=[function-list]
1278 [FTRACE] Limit the functions traced by the function
1279 tracer at boot up. function-list is a comma separated
1280 list of functions. This list can be changed at run
1281 time by the set_ftrace_filter file in the debugfs
1284 ftrace_notrace=[function-list]
1285 [FTRACE] Do not trace the functions specified in
1286 function-list. This list can be changed at run time
1287 by the set_ftrace_notrace file in the debugfs
1290 ftrace_graph_filter=[function-list]
1291 [FTRACE] Limit the top level callers functions traced
1292 by the function graph tracer at boot up.
1293 function-list is a comma separated list of functions
1294 that can be changed at run time by the
1295 set_graph_function file in the debugfs tracing directory.
1297 ftrace_graph_notrace=[function-list]
1298 [FTRACE] Do not trace from the functions specified in
1299 function-list. This list is a comma separated list of
1300 functions that can be changed at run time by the
1301 set_graph_notrace file in the debugfs tracing directory.
1303 ftrace_graph_max_depth=<uint>
1304 [FTRACE] Used with the function graph tracer. This is
1305 the max depth it will trace into a function. This value
1306 can be changed at run time by the max_graph_depth file
1307 in the tracefs tracing directory. default: 0 (no limit)
1310 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1311 support via parallel port (up to 5 devices per port)
1312 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1313 See also Documentation/input/devices/joystick-parport.rst
1317 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1321 gcov_persist= [GCOV] When non-zero (default), profiling data for
1322 kernel modules is saved and remains accessible via
1323 debugfs, even when the module is unloaded/reloaded.
1324 When zero, profiling data is discarded and associated
1325 debugfs files are removed at module unload time.
1327 goldfish [X86] Enable the goldfish android emulator platform.
1328 Don't use this when you are not running on the
1331 gpt [EFI] Forces disk with valid GPT signature but
1332 invalid Protective MBR to be treated as GPT. If the
1333 primary GPT is corrupted, it enables the backup/alternate
1334 GPT to be used instead.
1336 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1337 the "Enable 0" bit of the configuration register.
1340 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1341 the "Enable 0" bit of the configuration register.
1344 grcan.select= [HW] Select which physical interface to use.
1347 grcan.txsize= [HW] Sets the size of the tx buffer.
1348 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1350 grcan.rxsize= [HW] Sets the size of the rx buffer.
1351 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1354 gpio-mockup.gpio_mockup_ranges
1355 [HW] Sets the ranges of gpiochip of for this device.
1356 Format: <start1>,<end1>,<start2>,<end2>...
1358 hardlockup_all_cpu_backtrace=
1359 [KNL] Should the hard-lockup detector generate
1360 backtraces on all cpus.
1363 hashdist= [KNL,NUMA] Large hashes allocated during boot
1364 are distributed across NUMA nodes. Defaults on
1365 for 64-bit NUMA, off otherwise.
1366 Format: 0 | 1 (for off | on)
1368 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1370 hd= [EIDE] (E)IDE hard drive subsystem geometry
1371 Format: <cyl>,<head>,<sect>
1374 Disable Hardware Error Source Table (HEST) support;
1375 corresponding firmware-first mode error processing
1376 logic will be disabled.
1378 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1379 size of <nn>. This works even on boxes that have no
1380 highmem otherwise. This also works to reduce highmem
1381 size on bigger boxes.
1383 highres= [KNL] Enable/disable high resolution timer mode.
1384 Valid parameters: "on", "off"
1388 See Documentation/isdn/README.HiSax.
1392 hpet= [X86-32,HPET] option to control HPET usage
1393 Format: { enable (default) | disable | force |
1395 disable: disable HPET and use PIT instead
1396 force: allow force enabled of undocumented chips (ICH4,
1398 verbose: show contents of HPET registers during setup
1400 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1401 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1403 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1404 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1405 On x86-64 and powerpc, this option can be specified
1406 multiple times interleaved with hugepages= to reserve
1407 huge pages of different sizes. Valid pages sizes on
1408 x86-64 are 2M (when the CPU supports "pse") and 1G
1409 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1412 [KNL] Should the hung task detector generate panics.
1415 A nonzero value instructs the kernel to panic when a
1416 hung task is detected. The default value is controlled
1417 by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1418 option. The value selected by this boot parameter can
1419 be changed later by the kernel.hung_task_panic sysctl.
1421 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1422 terminal devices. Valid values: 0..8
1423 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1424 If specified, z/VM IUCV HVC accepts connections
1425 from listed z/VM user IDs only.
1427 hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations
1428 which allow the hypervisor to 'idle' the
1429 guest on lock contention.
1432 Do not unregister boot console at start. This is only
1433 useful for debugging when something happens in the window
1434 between unregistering the boot console and initializing
1437 i2c_bus= [HW] Override the default board specific I2C bus speed
1438 or register an additional I2C bus that is not
1439 registered from board initialization code.
1443 i8042.debug [HW] Toggle i8042 debug mode
1444 i8042.unmask_kbd_data
1445 [HW] Enable printing of interrupt data from the KBD port
1446 (disabled by default, and as a pre-condition
1447 requires that i8042.debug=1 be enabled)
1448 i8042.direct [HW] Put keyboard port into non-translated mode
1449 i8042.dumbkbd [HW] Pretend that controller can only read data from
1450 keyboard and cannot control its state
1451 (Don't attempt to blink the leds)
1452 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1453 i8042.nokbd [HW] Don't check/create keyboard port
1454 i8042.noloop [HW] Disable the AUX Loopback command while probing
1456 i8042.nomux [HW] Don't check presence of an active multiplexing
1458 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1460 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1461 i8042.reset [HW] Reset the controller during init, cleanup and
1462 suspend-to-ram transitions, only during s2r
1463 transitions, or never reset
1464 Format: { 1 | Y | y | 0 | N | n }
1465 1, Y, y: always reset controller
1466 0, N, n: don't ever reset controller
1467 Default: only on s2r transitions on x86; most other
1468 architectures force reset to be always executed
1469 i8042.unlock [HW] Unlock (ignore) the keylock
1470 i8042.kbdreset [HW] Reset device connected to KBD port
1474 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1475 indicates that the driver is running on unsupported
1477 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1478 does not match list of supported models.
1480 [HW] Report power status in /proc/i8k
1481 (disabled by default)
1482 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1485 i915.invert_brightness=
1486 [DRM] Invert the sense of the variable that is used to
1487 set the brightness of the panel backlight. Normally a
1488 brightness value of 0 indicates backlight switched off,
1489 and the maximum of the brightness value sets the backlight
1490 to maximum brightness. If this parameter is set to 0
1491 (default) and the machine requires it, or this parameter
1492 is set to 1, a brightness value of 0 sets the backlight
1493 to maximum brightness, and the maximum of the brightness
1494 value switches the backlight off.
1495 -1 -- never invert brightness
1496 0 -- machine default
1497 1 -- force brightness inversion
1500 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1502 ide-core.nodma= [HW] (E)IDE subsystem
1503 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1504 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1505 .cdrom .chs .ignore_cable are additional options
1506 See Documentation/ide/ide.txt.
1508 ide-generic.probe-mask= [HW] (E)IDE subsystem
1510 Probe mask for legacy ISA IDE ports. Depending on
1511 platform up to 6 ports are supported, enabled by
1512 setting corresponding bits in the mask to 1. The
1513 default value is 0x0, which has a special meaning.
1514 On systems that have PCI, it triggers scanning the
1515 PCI bus for the first and the second port, which
1516 are then probed. On systems without PCI the value
1517 of 0x0 enables probing the two first ports as if it
1520 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1521 Claim all unknown PCI IDE storage controllers.
1524 Format: idle=poll, idle=halt, idle=nomwait
1525 Poll forces a polling idle loop that can slightly
1526 improve the performance of waking up a idle CPU, but
1527 will use a lot of power and make the system run hot.
1529 idle=halt: Halt is forced to be used for CPU idle.
1530 In such case C2/C3 won't be used again.
1531 idle=nomwait: Disable mwait for CPU C-states
1533 ieee754= [MIPS] Select IEEE Std 754 conformance mode
1534 Format: { strict | legacy | 2008 | relaxed }
1537 Choose which programs will be accepted for execution
1538 based on the IEEE 754 NaN encoding(s) supported by
1539 the FPU and the NaN encoding requested with the value
1540 of an ELF file header flag individually set by each
1541 binary. Hardware implementations are permitted to
1542 support either or both of the legacy and the 2008 NaN
1545 Available settings are as follows:
1546 strict accept binaries that request a NaN encoding
1547 supported by the FPU
1548 legacy only accept legacy-NaN binaries, if supported
1550 2008 only accept 2008-NaN binaries, if supported
1552 relaxed accept any binaries regardless of whether
1553 supported by the FPU
1555 The FPU emulator is always able to support both NaN
1556 encodings, so if no FPU hardware is present or it has
1557 been disabled with 'nofpu', then the settings of
1558 'legacy' and '2008' strap the emulator accordingly,
1559 'relaxed' straps the emulator for both legacy-NaN and
1560 2008-NaN, whereas 'strict' enables legacy-NaN only on
1561 legacy processors and both NaN encodings on MIPS32 or
1564 The setting for ABS.fmt/NEG.fmt instruction execution
1565 mode generally follows that for the NaN encoding,
1566 except where unsupported by hardware.
1568 ignore_loglevel [KNL]
1569 Ignore loglevel setting - this will print /all/
1570 kernel messages to the console. Useful for debugging.
1571 We also add it as printk module parameter, so users
1572 could change it dynamically, usually by
1573 /sys/module/printk/parameters/ignore_loglevel.
1576 Ignore RLIMIT_DATA setting for data mappings,
1577 print warning at first misuse. Can be changed via
1578 /sys/module/kernel/parameters/ignore_rlimit_data.
1580 ihash_entries= [KNL]
1581 Set number of hash buckets for inode cache.
1583 ima_appraise= [IMA] appraise integrity measurements
1584 Format: { "off" | "enforce" | "fix" | "log" }
1587 ima_appraise_tcb [IMA]
1588 The builtin appraise policy appraises all files
1591 ima_canonical_fmt [IMA]
1592 Use the canonical format for the binary runtime
1593 measurements, instead of host native format.
1596 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1600 The list of supported hash algorithms is defined
1601 in crypto/hash_info.h.
1604 The builtin policies to load during IMA setup.
1605 Format: "tcb | appraise_tcb | secure_boot |
1608 The "tcb" policy measures all programs exec'd, files
1609 mmap'd for exec, and all files opened with the read
1610 mode bit set by either the effective uid (euid=0) or
1613 The "appraise_tcb" policy appraises the integrity of
1614 all files owned by root. (This is the equivalent
1615 of ima_appraise_tcb.)
1617 The "secure_boot" policy appraises the integrity
1618 of files (eg. kexec kernel image, kernel modules,
1619 firmware, policy, etc) based on file signatures.
1621 The "fail_securely" policy forces file signature
1622 verification failure also on privileged mounted
1623 filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
1626 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1627 Load a policy which meets the needs of the Trusted
1628 Computing Base. This means IMA will measure all
1629 programs exec'd, files mmap'd for exec, and all files
1630 opened for read by uid=0.
1633 Select one of defined IMA measurements template formats.
1634 Formats: { "ima" | "ima-ng" | "ima-sig" }
1638 [IMA] Define a custom template format.
1639 Format: { "field1|...|fieldN" }
1641 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1642 Format: <min_file_size>
1643 Set the minimal file size for using asynchronous hash.
1644 If left unspecified, ahash usage is disabled.
1646 ahash performance varies for different data sizes on
1647 different crypto accelerators. This option can be used
1648 to achieve the best performance for a particular HW.
1650 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1652 Set hashing buffer size. Default: 4k.
1654 ahash performance varies for different chunk sizes on
1655 different crypto accelerators. This option can be used
1656 to achieve best performance for particular HW.
1660 Run specified binary instead of /sbin/init as init
1663 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1664 for working out where the kernel is dying during
1667 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1668 initcall functions. Useful for debugging built-in
1669 modules and initcalls.
1671 initrd= [BOOT] Specify the location of the initial ramdisk
1673 init_pkru= [x86] Specify the default memory protection keys rights
1674 register contents for all processes. 0x55555554 by
1675 default (disallow access to all but pkey 0). Can
1676 override in debugfs after boot.
1678 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1681 int_pln_enable [x86] Enable power limit notification interrupt
1683 integrity_audit=[IMA]
1684 Format: { "0" | "1" }
1685 0 -- basic integrity auditing messages. (Default)
1686 1 -- additional integrity auditing messages.
1688 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1690 Enable intel iommu driver.
1692 Disable intel iommu driver.
1693 igfx_off [Default Off]
1694 By default, gfx is mapped as normal device. If a gfx
1695 device has a dedicated DMAR unit, the DMAR unit is
1696 bypassed by not enabling DMAR with this option. In
1697 this case, gfx device will use physical address for
1700 With this option iommu will not optimize to look
1701 for io virtual address below 32-bit forcing dual
1702 address cycle on pci bus for cards supporting greater
1703 than 32-bit addressing. The default is to look
1704 for translation below 32-bit and if not available
1705 then look in the higher range.
1706 strict [Default Off]
1707 With this option on every unmap_single operation will
1708 result in a hardware IOTLB flush operation as opposed
1709 to batching them for performance.
1710 sp_off [Default Off]
1711 By default, super page will be supported if Intel IOMMU
1712 has the capability. With this option, super page will
1715 By default, scalable mode will be disabled even if the
1716 hardware advertises that it has support for the scalable
1717 mode translation. With this option set, scalable mode
1718 will be used on hardware which claims to support it.
1719 tboot_noforce [Default Off]
1720 Do not force the Intel IOMMU enabled under tboot.
1721 By default, tboot will force Intel IOMMU on, which
1722 could harm performance of some high-throughput
1723 devices like 40GBit network cards, even if identity
1725 Note that using this option lowers the security
1726 provided by tboot because it makes the system
1727 vulnerable to DMA attacks.
1729 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1730 0 disables intel_idle and fall back on acpi_idle.
1731 1 to 9 specify maximum depth of C-state.
1735 Do not enable intel_pstate as the default
1736 scaling driver for the supported processors
1738 Use intel_pstate as a scaling driver, but configure it
1739 to work with generic cpufreq governors (instead of
1740 enabling its internal governor). This mode cannot be
1741 used along with the hardware-managed P-states (HWP)
1744 Enable intel_pstate on systems that prohibit it by default
1745 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1746 instead of acpi-cpufreq may disable platform features, such
1747 as thermal controls and power capping, that rely on ACPI
1748 P-States information being indicated to OSPM and therefore
1749 should be used with caution. This option does not work with
1750 processors that aren't supported by the intel_pstate driver
1751 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1753 Do not enable hardware P state control (HWP)
1756 Only load intel_pstate on systems which support
1757 hardware P state control (HWP) if available.
1759 Enforce ACPI _PPC performance limits. If the Fixed ACPI
1760 Description Table, specifies preferred power management
1761 profile as "Enterprise Server" or "Performance Server",
1762 then this feature is turned on by default.
1764 Allow per-logical-CPU P-State performance control limits using
1765 cpufreq sysfs interface
1767 intremap= [X86-64, Intel-IOMMU]
1768 on enable Interrupt Remapping (default)
1769 off disable Interrupt Remapping
1770 nosid disable Source ID checking
1772 BIOS x2APIC opt-out request will be ignored
1773 nopost disable Interrupt Posting
1775 iomem= Disable strict checking of access to MMIO memory
1776 strict regions from userspace.
1791 nobypass [PPC/POWERNV]
1792 Disable IOMMU bypass, using IOMMU for PCI devices.
1794 iommu.strict= [ARM64] Configure TLB invalidation behaviour
1795 Format: { "0" | "1" }
1797 Request that DMA unmap operations use deferred
1798 invalidation of hardware TLBs, for increased
1799 throughput at the cost of reduced device isolation.
1800 Will fall back to strict mode if not supported by
1801 the relevant IOMMU driver.
1802 1 - Strict mode (default).
1803 DMA unmap operations invalidate IOMMU hardware TLBs
1807 [ARM64] Configure DMA to bypass the IOMMU by default.
1808 Format: { "0" | "1" }
1809 0 - Use IOMMU translation for DMA.
1810 1 - Bypass the IOMMU for DMA.
1811 unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
1813 io7= [HW] IO7 for Marvel based alpha systems
1814 See comment before marvel_specify_io7 in
1815 arch/alpha/kernel/core_marvel.c.
1817 io_delay= [X86] I/O delay method
1819 Standard port 0x80 based delay
1821 Alternate port 0xed based delay (needed on some systems)
1823 Simple two microseconds delay
1828 See Documentation/filesystems/nfs/nfsroot.txt.
1830 irqaffinity= [SMP] Set the default irq affinity mask
1831 The argument is a cpu list, as described above.
1833 irqchip.gicv2_force_probe=
1836 Force the kernel to look for the second 4kB page
1837 of a GICv2 controller even if the memory range
1838 exposed by the device tree is too small.
1840 irqchip.gicv3_nolpi=
1842 Force the kernel to ignore the availability of
1843 LPIs (and by consequence ITSs). Intended for system
1844 that use the kernel as a bootloader, and thus want
1845 to let secondary kernels in charge of setting up
1849 When an interrupt is not handled search all handlers
1850 for it. Intended to get systems with badly broken
1854 When an interrupt is not handled search all handlers
1855 for it. Also check all handlers each timer
1856 interrupt. Intended to get systems with badly broken
1860 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1862 isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
1863 [Deprecated - use cpusets instead]
1864 Format: [flag-list,]<cpu-list>
1866 Specify one or more CPUs to isolate from disturbances
1867 specified in the flag list (default: domain):
1870 Disable the tick when a single task runs.
1872 A residual 1Hz tick is offloaded to workqueues, which you
1873 need to affine to housekeeping through the global
1874 workqueue's affinity configured via the
1875 /sys/devices/virtual/workqueue/cpumask sysfs file, or
1876 by using the 'domain' flag described below.
1878 NOTE: by default the global workqueue runs on all CPUs,
1879 so to protect individual CPUs the 'cpumask' file has to
1880 be configured manually after bootup.
1883 Isolate from the general SMP balancing and scheduling
1884 algorithms. Note that performing domain isolation this way
1885 is irreversible: it's not possible to bring back a CPU to
1886 the domains once isolated through isolcpus. It's strongly
1887 advised to use cpusets instead to disable scheduler load
1888 balancing through the "cpuset.sched_load_balance" file.
1889 It offers a much more flexible interface where CPUs can
1890 move in and out of an isolated set anytime.
1892 You can move a process onto or off an "isolated" CPU via
1893 the CPU affinity syscalls or cpuset.
1894 <cpu number> begins at 0 and the maximum value is
1895 "number of CPUs in system - 1".
1897 The format of <cpu-list> is described above.
1903 ivrs_ioapic [HW,X86_64]
1904 Provide an override to the IOAPIC-ID<->DEVICE-ID
1905 mapping provided in the IVRS ACPI table. For
1906 example, to map IOAPIC-ID decimal 10 to
1907 PCI device 00:14.0 write the parameter as:
1908 ivrs_ioapic[10]=00:14.0
1910 ivrs_hpet [HW,X86_64]
1911 Provide an override to the HPET-ID<->DEVICE-ID
1912 mapping provided in the IVRS ACPI table. For
1913 example, to map HPET-ID decimal 0 to
1914 PCI device 00:14.0 write the parameter as:
1915 ivrs_hpet[0]=00:14.0
1917 ivrs_acpihid [HW,X86_64]
1918 Provide an override to the ACPI-HID:UID<->DEVICE-ID
1919 mapping provided in the IVRS ACPI table. For
1920 example, to map UART-HID:UID AMD0020:0 to
1921 PCI device 00:14.5 write the parameter as:
1922 ivrs_acpihid[00:14.5]=AMD0020:0
1924 js= [HW,JOY] Analog joystick
1925 See Documentation/input/joydev/joystick.rst.
1928 When CONFIG_RANDOMIZE_BASE is set, this disables
1929 kernel and module base offset ASLR (Address Space
1930 Layout Randomization).
1933 [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
1934 report on every invalid memory access. Without this
1935 parameter KASAN will print report only for the first
1940 kernelcore= [KNL,X86,IA-64,PPC]
1941 Format: nn[KMGTPE] | nn% | "mirror"
1942 This parameter specifies the amount of memory usable by
1943 the kernel for non-movable allocations. The requested
1944 amount is spread evenly throughout all nodes in the
1945 system as ZONE_NORMAL. The remaining memory is used for
1946 movable memory in its own zone, ZONE_MOVABLE. In the
1947 event, a node is too small to have both ZONE_NORMAL and
1948 ZONE_MOVABLE, kernelcore memory will take priority and
1949 other nodes will have a larger ZONE_MOVABLE.
1951 ZONE_MOVABLE is used for the allocation of pages that
1952 may be reclaimed or moved by the page migration
1953 subsystem. Note that allocations like PTEs-from-HighMem
1954 still use the HighMem zone if it exists, and the Normal
1955 zone if it does not.
1957 It is possible to specify the exact amount of memory in
1958 the form of "nn[KMGTPE]", a percentage of total system
1959 memory in the form of "nn%", or "mirror". If "mirror"
1960 option is specified, mirrored (reliable) memory is used
1961 for non-movable allocations and remaining memory is used
1962 for Movable pages. "nn[KMGTPE]", "nn%", and "mirror"
1963 are exclusive, so you cannot specify multiple forms.
1965 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1966 Format: <Controller#>[,poll interval]
1967 The controller # is the number of the ehci usb debug
1968 port as it is probed via PCI. The poll interval is
1969 optional and is the number seconds in between
1970 each poll cycle to the debug port in case you need
1971 the functionality for interrupting the kernel with
1972 gdb or control-c on the dbgp connection. When
1973 not using this parameter you use sysrq-g to break into
1974 the kernel debugger.
1976 kgdboc= [KGDB,HW] kgdb over consoles.
1977 Requires a tty driver that supports console polling,
1978 or a supported polling keyboard driver (non-usb).
1979 Serial only format: <serial_device>[,baud]
1980 keyboard only format: kbd
1981 keyboard and serial format: kbd,<serial_device>[,baud]
1982 Optional Kernel mode setting:
1983 kms, kbd format: kms,kbd
1984 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1986 kgdbwait [KGDB] Stop kernel execution and enter the
1987 kernel debugger at the earliest opportunity.
1989 kmac= [MIPS] korina ethernet MAC address.
1990 Configure the RouterBoard 532 series on-chip
1991 Ethernet adapter MAC address.
1993 kmemleak= [KNL] Boot-time kmemleak enable/disable
1994 Valid arguments: on, off
1996 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1999 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
2000 Default is 0 (don't ignore, but inject #GP)
2002 kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
2003 Default is false (don't support).
2005 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
2009 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
2010 Default is 1 (enabled)
2012 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
2014 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
2016 kvm-arm.vgic_v3_group0_trap=
2017 [KVM,ARM] Trap guest accesses to GICv3 group-0
2020 kvm-arm.vgic_v3_group1_trap=
2021 [KVM,ARM] Trap guest accesses to GICv3 group-1
2024 kvm-arm.vgic_v3_common_trap=
2025 [KVM,ARM] Trap guest accesses to GICv3 common
2028 kvm-arm.vgic_v4_enable=
2029 [KVM,ARM] Allow use of GICv4 for direct injection of
2032 kvm-intel.ept= [KVM,Intel] Disable extended page tables
2033 (virtualized MMU) support on capable Intel chips.
2034 Default is 1 (enabled)
2036 kvm-intel.emulate_invalid_guest_state=
2037 [KVM,Intel] Enable emulation of invalid guest states
2038 Default is 0 (disabled)
2040 kvm-intel.flexpriority=
2041 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
2042 Default is 1 (enabled)
2045 [KVM,Intel] Enable VMX nesting (nVMX).
2046 Default is 0 (disabled)
2048 kvm-intel.unrestricted_guest=
2049 [KVM,Intel] Disable unrestricted guest feature
2050 (virtualized real and unpaged mode) on capable
2051 Intel chips. Default is 1 (enabled)
2053 kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2056 Valid arguments: never, cond, always
2058 always: L1D cache flush on every VMENTER.
2059 cond: Flush L1D on VMENTER only when the code between
2060 VMEXIT and VMENTER can leak host memory.
2061 never: Disables the mitigation
2063 Default is cond (do L1 cache flush in specific instances)
2065 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
2066 feature (tagged TLBs) on capable Intel chips.
2067 Default is 1 (enabled)
2069 l1tf= [X86] Control mitigation of the L1TF vulnerability on
2072 The kernel PTE inversion protection is unconditionally
2073 enabled and cannot be disabled.
2076 Provides all available mitigations for the
2077 L1TF vulnerability. Disables SMT and
2078 enables all mitigations in the
2079 hypervisors, i.e. unconditional L1D flush.
2081 SMT control and L1D flush control via the
2082 sysfs interface is still possible after
2083 boot. Hypervisors will issue a warning
2084 when the first VM is started in a
2085 potentially insecure configuration,
2086 i.e. SMT enabled or L1D flush disabled.
2089 Same as 'full', but disables SMT and L1D
2090 flush runtime control. Implies the
2091 'nosmt=force' command line option.
2092 (i.e. sysfs control of SMT is disabled.)
2095 Leaves SMT enabled and enables the default
2096 hypervisor mitigation, i.e. conditional
2099 SMT control and L1D flush control via the
2100 sysfs interface is still possible after
2101 boot. Hypervisors will issue a warning
2102 when the first VM is started in a
2103 potentially insecure configuration,
2104 i.e. SMT enabled or L1D flush disabled.
2108 Disables SMT and enables the default
2109 hypervisor mitigation.
2111 SMT control and L1D flush control via the
2112 sysfs interface is still possible after
2113 boot. Hypervisors will issue a warning
2114 when the first VM is started in a
2115 potentially insecure configuration,
2116 i.e. SMT enabled or L1D flush disabled.
2119 Same as 'flush', but hypervisors will not
2120 warn when a VM is started in a potentially
2121 insecure configuration.
2124 Disables hypervisor mitigations and doesn't
2126 It also drops the swap size and available
2127 RAM limit restriction on both hypervisor and
2132 For details see: Documentation/admin-guide/l1tf.rst
2138 lapic [X86-32,APIC] Enable the local APIC even if BIOS
2141 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
2142 value for LAPIC timer one-shot implementation. Default
2143 back to the programmable timer unit in the LAPIC.
2145 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
2148 libata.dma= [LIBATA] DMA control
2149 libata.dma=0 Disable all PATA and SATA DMA
2150 libata.dma=1 PATA and SATA Disk DMA only
2151 libata.dma=2 ATAPI (CDROM) DMA only
2152 libata.dma=4 Compact Flash DMA only
2153 Combinations also work, so libata.dma=3 enables DMA
2154 for disks and CDROMs, but not CFs.
2156 libata.ignore_hpa= [LIBATA] Ignore HPA limit
2157 libata.ignore_hpa=0 keep BIOS limits (default)
2158 libata.ignore_hpa=1 ignore limits, using full disk
2160 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
2164 libata.force= [LIBATA] Force configurations. The format is comma
2165 separated list of "[ID:]VAL" where ID is
2166 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
2167 matching port, link or device. Basically, it matches
2168 the ATA ID string printed on console by libata. If
2169 the whole ID part is omitted, the last PORT and DEVICE
2170 values are used. If ID hasn't been specified yet, the
2171 configuration applies to all ports, links and devices.
2173 If only DEVICE is omitted, the parameter applies to
2174 the port and all links and devices behind it. DEVICE
2175 number of 0 either selects the first device or the
2176 first fan-out link behind PMP device. It does not
2177 select the host link. DEVICE number of 15 selects the
2178 host link and device attached to it.
2180 The VAL specifies the configuration to force. As long
2181 as there's no ambiguity shortcut notation is allowed.
2182 For example, both 1.5 and 1.5G would work for 1.5Gbps.
2183 The following configurations can be forced.
2185 * Cable type: 40c, 80c, short40c, unk, ign or sata.
2186 Any ID with matching PORT is used.
2188 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
2190 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2191 udma[/][16,25,33,44,66,100,133] notation is also
2194 * [no]ncq: Turn on or off NCQ.
2196 * [no]ncqtrim: Turn off queued DSM TRIM.
2198 * nohrst, nosrst, norst: suppress hard, soft
2201 * rstonce: only attempt one reset during
2202 hot-unplug link recovery
2204 * dump_id: dump IDENTIFY data.
2206 * atapi_dmadir: Enable ATAPI DMADIR bridge support
2208 * disable: Disable this device.
2210 If there are multiple matching configurations changing
2211 the same attribute, the last one is used.
2213 memblock=debug [KNL] Enable memblock debug messages.
2215 load_ramdisk= [RAM] List of ramdisks to load from floppy
2216 See Documentation/blockdev/ramdisk.txt.
2218 lockd.nlm_grace_period=P [NFS] Assign grace period.
2221 lockd.nlm_tcpport=N [NFS] Assign TCP port.
2224 lockd.nlm_timeout=T [NFS] Assign timeout value.
2227 lockd.nlm_udpport=M [NFS] Assign UDP port.
2230 locktorture.nreaders_stress= [KNL]
2231 Set the number of locking read-acquisition kthreads.
2232 Defaults to being automatically set based on the
2233 number of online CPUs.
2235 locktorture.nwriters_stress= [KNL]
2236 Set the number of locking write-acquisition kthreads.
2238 locktorture.onoff_holdoff= [KNL]
2239 Set time (s) after boot for CPU-hotplug testing.
2241 locktorture.onoff_interval= [KNL]
2242 Set time (s) between CPU-hotplug operations, or
2243 zero to disable CPU-hotplug testing.
2245 locktorture.shuffle_interval= [KNL]
2246 Set task-shuffle interval (jiffies). Shuffling
2247 tasks allows some CPUs to go into dyntick-idle
2248 mode during the locktorture test.
2250 locktorture.shutdown_secs= [KNL]
2251 Set time (s) after boot system shutdown. This
2252 is useful for hands-off automated testing.
2254 locktorture.stat_interval= [KNL]
2255 Time (s) between statistics printk()s.
2257 locktorture.stutter= [KNL]
2258 Time (s) to stutter testing, for example,
2259 specifying five seconds causes the test to run for
2260 five seconds, wait for five seconds, and so on.
2261 This tests the locking primitive's ability to
2262 transition abruptly to and from idle.
2264 locktorture.torture_type= [KNL]
2265 Specify the locking implementation to test.
2267 locktorture.verbose= [KNL]
2268 Enable additional printk() statements.
2270 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
2273 loglevel= All Kernel Messages with a loglevel smaller than the
2274 console loglevel will be printed to the console. It can
2275 also be changed with klogd or other programs. The
2276 loglevels are defined as follows:
2278 0 (KERN_EMERG) system is unusable
2279 1 (KERN_ALERT) action must be taken immediately
2280 2 (KERN_CRIT) critical conditions
2281 3 (KERN_ERR) error conditions
2282 4 (KERN_WARNING) warning conditions
2283 5 (KERN_NOTICE) normal but significant condition
2284 6 (KERN_INFO) informational
2285 7 (KERN_DEBUG) debug-level messages
2287 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
2288 in bytes. n must be a power of two and greater
2289 than the minimal size. The minimal size is defined
2290 by LOG_BUF_SHIFT kernel config parameter. There is
2291 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
2292 that allows to increase the default size depending on
2293 the number of CPUs. See init/Kconfig for more details.
2295 logo.nologo [FB] Disables display of the built-in Linux logo.
2296 This may be used to provide more screen space for
2297 kernel log messages and is useful when debugging
2298 kernel boot problems.
2300 lp=0 [LP] Specify parallel ports to use, e.g,
2301 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
2302 lp=reset first parallel port). 'lp=0' disables the
2303 lp=auto printer driver. 'lp=reset' (which can be
2304 specified in addition to the ports) causes
2305 attached printers to be reset. Using
2306 lp=port1,port2,... specifies the parallel ports
2307 to associate lp devices with, starting with
2308 lp0. A port specification may be 'none' to skip
2309 that lp device, or a parport name such as
2310 'parport0'. Specifying 'lp=auto' instead of a
2311 port specification list means that device IDs
2312 from each port should be examined, to see if
2313 an IEEE 1284-compliant printer is attached; if
2314 so, the driver will manage that printer.
2315 See also header of drivers/char/lp.c.
2318 Sets loops_per_jiffy to given constant, thus avoiding
2319 time-consuming boot-time autodetection (up to 250 ms per
2320 CPU). 0 enables autodetection (default). To determine
2321 the correct value for your kernel, boot with normal
2322 autodetection and see what value is printed. Note that
2323 on SMP systems the preset will be applied to all CPUs,
2324 which is likely to cause problems if your CPUs need
2325 significantly divergent settings. An incorrect value
2326 will cause delays in the kernel to be wrong, leading to
2327 unpredictable I/O errors and other breakage. Although
2328 unlikely, in the extreme case this might damage your
2332 Format: <io>,<irq>,<dma>
2334 lsm.debug [SECURITY] Enable LSM initialization debugging output.
2337 [SECURITY] Choose order of LSM initialization. This
2338 overrides CONFIG_LSM, and the "security=" parameter.
2340 machvec= [IA-64] Force the use of a particular machine-vector
2341 (machvec) in a generic kernel.
2342 Example: machvec=hpzx1_swiotlb
2344 machtype= [Loongson] Share the same kernel image file between different
2346 Example: machtype=lemote-yeeloong-2f-7inch
2348 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2349 than or equal to this physical address is ignored.
2351 maxcpus= [SMP] Maximum number of processors that an SMP kernel
2352 will bring up during bootup. maxcpus=n : n >= 0 limits
2353 the kernel to bring up 'n' processors. Surely after
2354 bootup you can bring up the other plugged cpu by executing
2355 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
2356 only takes effect during system bootup.
2357 While n=0 is a special case, it is equivalent to "nosmp",
2358 which also disables the IO APIC.
2360 max_loop= [LOOP] The number of loop block devices that get
2361 (loop.max_loop) unconditionally pre-created at init time. The default
2362 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2363 of statically allocating a predefined number, loop
2364 devices can be requested on-demand with the
2365 /dev/loop-control interface.
2367 mce [X86-32] Machine Check Exception
2369 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2371 md= [HW] RAID subsystems devices and level
2372 See Documentation/admin-guide/md.rst.
2375 Format: <first>,<last>
2376 Specifies range of consoles to be captured by the MDA.
2378 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2379 Amount of memory to be used when the kernel is not able
2380 to see the whole system memory or for test.
2381 [X86] Work as limiting max address. Use together
2382 with memmap= to avoid physical address space collisions.
2383 Without memmap= PCI devices could be placed at addresses
2384 belonging to unused RAM.
2386 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2390 [KNL,SH] Allow user to override the default size for
2391 per-device physically contiguous DMA buffers.
2393 memhp_default_state=online/offline
2394 [KNL] Set the initial state for the memory hotplug
2395 onlining policy. If not specified, the default value is
2396 set according to the
2397 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
2399 See Documentation/memory-hotplug.txt.
2401 memmap=exactmap [KNL,X86] Enable setting of an exact
2402 E820 memory map, as specified by the user.
2403 Such memmap=exactmap lines can be constructed based on
2404 BIOS output or other requirements. See the memmap=nn@ss
2407 memmap=nn[KMG]@ss[KMG]
2408 [KNL] Force usage of a specific region of memory.
2409 Region of memory to be used is from ss to ss+nn.
2410 If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
2411 which limits max address to nn[KMG].
2412 Multiple different regions can be specified,
2415 memmap=100M@2G,100M#3G,1G!1024G
2417 memmap=nn[KMG]#ss[KMG]
2418 [KNL,ACPI] Mark specific memory as ACPI data.
2419 Region of memory to be marked is from ss to ss+nn.
2421 memmap=nn[KMG]$ss[KMG]
2422 [KNL,ACPI] Mark specific memory as reserved.
2423 Region of memory to be reserved is from ss to ss+nn.
2424 Example: Exclude memory from 0x18690000-0x1869ffff
2425 memmap=64K$0x18690000
2427 memmap=0x10000$0x18690000
2428 Some bootloaders may need an escape character before '$',
2429 like Grub2, otherwise '$' and the following number
2432 memmap=nn[KMG]!ss[KMG]
2433 [KNL,X86] Mark specific memory as protected.
2434 Region of memory to be used, from ss to ss+nn.
2435 The memory region may be marked as e820 type 12 (0xc)
2436 and is NVDIMM or ADR memory.
2438 memmap=<size>%<offset>-<oldtype>+<newtype>
2439 [KNL,ACPI] Convert memory within the specified region
2440 from <oldtype> to <newtype>. If "-<oldtype>" is left
2441 out, the whole region will be marked as <newtype>,
2442 even if previously unavailable. If "+<newtype>" is left
2443 out, matching memory will be removed. Types are
2444 specified as e820 types, e.g., 1 = RAM, 2 = reserved,
2445 3 = ACPI, 12 = PRAM.
2447 memory_corruption_check=0/1 [X86]
2448 Some BIOSes seem to corrupt the first 64k of
2449 memory when doing things like suspend/resume.
2450 Setting this option will scan the memory
2451 looking for corruption. Enabling this will
2452 both detect corruption and prevent the kernel
2453 from using the memory being corrupted.
2454 However, its intended as a diagnostic tool; if
2455 repeatable BIOS-originated corruption always
2456 affects the same memory, you can use memmap=
2457 to prevent the kernel from using that memory.
2459 memory_corruption_check_size=size [X86]
2460 By default it checks for corruption in the low
2461 64k, making this memory unavailable for normal
2462 use. Use this parameter to scan for
2463 corruption in more or less memory.
2465 memory_corruption_check_period=seconds [X86]
2466 By default it checks for corruption every 60
2467 seconds. Use this parameter to check at some
2468 other rate. 0 disables periodic checking.
2470 memtest= [KNL,X86,ARM,PPC] Enable memtest
2472 default : 0 <disable>
2473 Specifies the number of memtest passes to be
2474 performed. Each pass selects another test
2475 pattern from a given set of patterns. Memtest
2476 fills the memory with this pattern, validates
2477 memory contents and reserves bad memory
2478 regions that are detected.
2480 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
2481 Valid arguments: on, off
2482 Default (depends on kernel configuration option):
2483 on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
2484 off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
2485 mem_encrypt=on: Activate SME
2486 mem_encrypt=off: Do not activate SME
2488 Refer to Documentation/x86/amd-memory-encryption.txt
2489 for details on when memory encryption can be activated.
2491 mem_sleep_default= [SUSPEND] Default system suspend mode:
2492 s2idle - Suspend-To-Idle
2493 shallow - Power-On Suspend or equivalent (if supported)
2494 deep - Suspend-To-RAM or equivalent (if supported)
2495 See Documentation/admin-guide/pm/sleep-states.rst.
2497 meye.*= [HW] Set MotionEye Camera parameters
2498 See Documentation/media/v4l-drivers/meye.rst.
2500 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2501 Multi-Function General Purpose Timers on AMD Geode
2504 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2505 the BIOS has incorrectly applied a workaround. TinyBIOS
2506 version 0.98 is known to be affected, 0.99 fixes the
2507 problem by letting the user disable the workaround.
2511 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2512 physical address is ignored.
2514 mini2440= [ARM,HW,KNL]
2515 Format:[0..2][b][c][t]
2517 MINI2440 configuration specification:
2518 0 - The attached screen is the 3.5" TFT
2519 1 - The attached screen is the 7" TFT
2520 2 - The VGA Shield is attached (1024x768)
2521 Leaving out the screen size parameter will not load
2522 the TFT driver, and the framebuffer will be left
2524 b - Enable backlight. The TFT backlight pin will be
2525 linked to the kernel VESA blanking code and a GPIO
2526 LED. This parameter is not necessary when using the
2528 c - Enable the s3c camera interface.
2529 t - Reserved for enabling touchscreen support. The
2530 touchscreen support is not enabled in the mainstream
2531 kernel as of 2.6.30, a preliminary port can be found
2532 in the "bleeding edge" mini2440 support kernel at
2533 http://repo.or.cz/w/linux-2.6/mini2440.git
2536 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2537 parameter allows control of the logging verbosity for
2538 the additional memory initialisation checks. A value
2539 of 0 disables mminit logging and a level of 4 will
2540 log everything. Information is printed at KERN_DEBUG
2541 so loglevel=8 may also need to be specified.
2544 [KNL] When CONFIG_MODULE_SIG is set, this means that
2545 modules without (valid) signatures will fail to load.
2546 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2547 is always true, so this option does nothing.
2549 module_blacklist= [KNL] Do not load a comma-separated list of
2550 modules. Useful for debugging problem modules.
2553 [MOUSE] Maximum time between finger touching and
2554 leaving touchpad surface for touch to be considered
2555 a tap and be reported as a left button click (for
2556 touchpads working in absolute mode only).
2558 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2559 reporting absolute coordinates, such as tablets
2560 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2561 reporting absolute coordinates, such as tablets
2563 movablecore= [KNL,X86,IA-64,PPC]
2564 Format: nn[KMGTPE] | nn%
2565 This parameter is the complement to kernelcore=, it
2566 specifies the amount of memory used for migratable
2567 allocations. If both kernelcore and movablecore is
2568 specified, then kernelcore will be at *least* the
2569 specified value but may be more. If movablecore on its
2570 own is specified, the administrator must be careful
2571 that the amount of memory usable for all allocations
2574 movable_node [KNL] Boot-time switch to make hotplugable memory
2575 NUMA nodes to be movable. This means that the memory
2576 of such nodes will be usable only for movable
2577 allocations which rules out almost all kernel
2578 allocations. Use with caution!
2580 MTD_Partition= [MTD]
2581 Format: <name>,<region-number>,<size>,<offset>
2583 MTD_Region= [MTD] Format:
2584 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2587 See drivers/mtd/cmdlinepart.c.
2589 multitce=off [PPC] This parameter disables the use of the pSeries
2590 firmware feature for updating multiple TCE entries
2593 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2595 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2597 boundary - index of last SLC block on Flex-OneNAND.
2598 The remaining blocks are configured as MLC blocks.
2599 lock - Configure if Flex-OneNAND boundary should be locked.
2600 Once locked, the boundary cannot be changed.
2601 1 indicates lock status, 0 indicates unlock status.
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