strictly ACPI specification compliant.
rsdt -- prefer RSDT over (default) XSDT
copy_dsdt -- copy DSDT to memory
+ nocmcff -- Disable firmware first mode for corrected
+ errors. This disables parsing the HEST CMC error
+ source to check if firmware has set the FF flag. This
+ may result in duplicate corrected error reports.
nospcr -- disable console in ACPI SPCR table as
default _serial_ console on ARM64
For ARM64, ONLY "acpi=off", "acpi=on", "acpi=force" or
not play well with APC CPU idle - disable it if you have
APC and your system crashes randomly.
+ apic [APIC,X86-64] Use IO-APIC. Default.
+
apic= [APIC,X86,EARLY] Advanced Programmable Interrupt Controller
Change the output verbosity while booting
Format: { quiet (default) | verbose | debug }
useful so that a dump capture kernel won't be
shot down by NMI
+ apicpmtimer Do APIC timer calibration using the pmtimer. Implies
+ apicmaintimer. Useful when your PIT timer is totally
+ broken.
+
autoconf= [IPV6]
See Documentation/networking/ipv6.rst.
off: Disable GDS mitigation.
+ gbpages [X86] Use GB pages for kernel direct mappings.
+
gcov_persist= [GCOV] When non-zero (default), profiling data for
kernel modules is saved and remains accessible via
debugfs, even when the module is unloaded/reloaded.
idle= [X86,EARLY]
Format: idle=poll, idle=halt, idle=nomwait
- Poll forces a polling idle loop that can slightly
- improve the performance of waking up a idle CPU, but
- will use a lot of power and make the system run hot.
- Not recommended.
+
+ idle=poll: Don't do power saving in the idle loop
+ using HLT, but poll for rescheduling event. This will
+ make the CPUs eat a lot more power, but may be useful
+ to get slightly better performance in multiprocessor
+ benchmarks. It also makes some profiling using
+ performance counters more accurate. Please note that
+ on systems with MONITOR/MWAIT support (like Intel
+ EM64T CPUs) this option has no performance advantage
+ over the normal idle loop. It may also interact badly
+ with hyperthreading.
+
idle=halt: Halt is forced to be used for CPU idle.
In such case C2/C3 won't be used again.
+
idle=nomwait: Disable mwait for CPU C-states
idxd.sva= [HW]
relaxed
iommu= [X86,EARLY]
+
off
+ Don't initialize and use any kind of IOMMU.
+
force
+ Force the use of the hardware IOMMU even when
+ it is not actually needed (e.g. because < 3 GB
+ memory).
+
noforce
+ Don't force hardware IOMMU usage when it is not
+ needed. (default).
+
biomerge
panic
nopanic
merge
nomerge
+
soft
- pt [X86]
- nopt [X86]
- nobypass [PPC/POWERNV]
+ Use software bounce buffering (SWIOTLB) (default for
+ Intel machines). This can be used to prevent the usage
+ of an available hardware IOMMU.
+
+ [X86]
+ pt
+ [X86]
+ nopt
+ [PPC/POWERNV]
+ nobypass
Disable IOMMU bypass, using IOMMU for PCI devices.
+ [X86]
+ AMD Gart HW IOMMU-specific options:
+
+ <size>
+ Set the size of the remapping area in bytes.
+
+ allowed
+ Overwrite iommu off workarounds for specific chipsets
+
+ fullflush
+ Flush IOMMU on each allocation (default).
+
+ nofullflush
+ Don't use IOMMU fullflush.
+
+ memaper[=<order>]
+ Allocate an own aperture over RAM with size
+ 32MB<<order. (default: order=1, i.e. 64MB)
+
+ merge
+ Do scatter-gather (SG) merging. Implies "force"
+ (experimental).
+
+ nomerge
+ Don't do scatter-gather (SG) merging.
+
+ noaperture
+ Ask the IOMMU not to touch the aperture for AGP.
+
+ noagp
+ Don't initialize the AGP driver and use full aperture.
+
+ panic
+ Always panic when IOMMU overflows.
+
iommu.forcedac= [ARM64,X86,EARLY] Control IOVA allocation for PCI devices.
Format: { "0" | "1" }
0 - Try to allocate a 32-bit DMA address first, before
specified in the flag list (default: domain):
nohz
- Disable the tick when a single task runs.
+ Disable the tick when a single task runs as well as
+ disabling other kernel noises like having RCU callbacks
+ offloaded. This is equivalent to the nohz_full parameter.
A residual 1Hz tick is offloaded to workqueues, which you
need to affine to housekeeping through the global
VMs, i.e. on the 0=>1 and 1=>0 transitions of the
number of VMs.
- Enabling virtualization at module lode avoids potential
+ Enabling virtualization at module load avoids potential
latency for creation of the 0=>1 VM, as KVM serializes
virtualization enabling across all online CPUs. The
"cost" of enabling virtualization when KVM is loaded,
devices can be requested on-demand with the
/dev/loop-control interface.
- mce [X86-32] Machine Check Exception
+ mce= [X86-{32,64}]
+
+ Please see Documentation/arch/x86/x86_64/machinecheck.rst for sysfs runtime tunables.
+
+ off
+ disable machine check
+
+ no_cmci
+ disable CMCI(Corrected Machine Check Interrupt) that
+ Intel processor supports. Usually this disablement is
+ not recommended, but it might be handy if your
+ hardware is misbehaving.
+
+ Note that you'll get more problems without CMCI than
+ with due to the shared banks, i.e. you might get
+ duplicated error logs.
+
+ dont_log_ce
+ don't make logs for corrected errors. All events
+ reported as corrected are silently cleared by OS. This
+ option will be useful if you have no interest in any
+ of corrected errors.
+
+ ignore_ce
+ disable features for corrected errors, e.g.
+ polling timer and CMCI. All events reported as
+ corrected are not cleared by OS and remained in its
+ error banks.
+
+ Usually this disablement is not recommended, however
+ if there is an agent checking/clearing corrected
+ errors (e.g. BIOS or hardware monitoring
+ applications), conflicting with OS's error handling,
+ and you cannot deactivate the agent, then this option
+ will be a help.
+
+ no_lmce
+ do not opt-in to Local MCE delivery. Use legacy method
+ to broadcast MCEs.
+
+ bootlog
+ enable logging of machine checks left over from
+ booting. Disabled by default on AMD Fam10h and older
+ because some BIOS leave bogus ones.
+
+ If your BIOS doesn't do that it's a good idea to
+ enable though to make sure you log even machine check
+ events that result in a reboot. On Intel systems it is
+ enabled by default.
+
+ nobootlog
+ disable boot machine check logging.
+
+ monarchtimeout (number)
+ sets the time in us to wait for other CPUs on machine
+ checks. 0 to disable.
+
+ bios_cmci_threshold
+ don't overwrite the bios-set CMCI threshold. This boot
+ option prevents Linux from overwriting the CMCI
+ threshold set by the bios. Without this option, Linux
+ always sets the CMCI threshold to 1. Enabling this may
+ make memory predictive failure analysis less effective
+ if the bios sets thresholds for memory errors since we
+ will not see details for all errors.
+
+ recovery
+ force-enable recoverable machine check code paths
+
+ Everything else is in sysfs now.
- mce=option [X86-64] See Documentation/arch/x86/x86_64/boot-options.rst
md= [HW] RAID subsystems devices and level
See Documentation/admin-guide/md.rst.
noapic [SMP,APIC,EARLY] Tells the kernel to not make use of any
IOAPICs that may be present in the system.
+ noapictimer [APIC,X86] Don't set up the APIC timer
+
noautogroup Disable scheduler automatic task group creation.
nocache [ARM,EARLY]
register save and restore. The kernel will only save
legacy floating-point registers on task switch.
+ nogbpages [X86] Do not use GB pages for kernel direct mappings.
+
no_hash_pointers
[KNL,EARLY]
Force pointers printed to the console or buffers to be
the impact of the sleep instructions. This is also
useful when using JTAG debugger.
+ nohpet [X86] Don't use the HPET timer.
+
nohugeiomap [KNL,X86,PPC,ARM64,EARLY] Disable kernel huge I/O mappings.
nohugevmalloc [KNL,X86,PPC,ARM64,EARLY] Disable kernel huge vmalloc mappings.
nosync [HW,M68K] Disables sync negotiation for all devices.
- no_timer_check [X86,APIC] Disables the code which tests for
- broken timer IRQ sources.
+ no_timer_check [X86,APIC] Disables the code which tests for broken
+ timer IRQ sources, i.e., the IO-APIC timer. This can
+ work around problems with incorrect timer
+ initialization on some boards.
no_uaccess_flush
[PPC,EARLY] Don't flush the L1-D cache after accessing user data.
If given as an integer followed by 'U', it will
divide each physical node into N emulated nodes.
+ numa=noacpi [X86] Don't parse the SRAT table for NUMA setup
+
+ numa=nohmat [X86] Don't parse the HMAT table for NUMA setup, or
+ soft-reserved memory partitioning.
+
numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic
NUMA balancing.
Allowed values are enable and disable
'1' – force enabled
'x' – unchanged
For example,
- pci=config_acs=10x
+ pci=config_acs=10x@pci:0:0
would configure all devices that support
ACS to enable P2P Request Redirect, disable
Translation Blocking, and leave Source
rcutorture.gp_cond= [KNL]
Use conditional/asynchronous update-side
- primitives, if available.
+ normal-grace-period primitives, if available.
+
+ rcutorture.gp_cond_exp= [KNL]
+ Use conditional/asynchronous update-side
+ expedited-grace-period primitives, if available.
+
+ rcutorture.gp_cond_full= [KNL]
+ Use conditional/asynchronous update-side
+ normal-grace-period primitives that also take
+ concurrent expedited grace periods into account,
+ if available.
+
+ rcutorture.gp_cond_exp_full= [KNL]
+ Use conditional/asynchronous update-side
+ expedited-grace-period primitives that also take
+ concurrent normal grace periods into account,
+ if available.
+
+ rcutorture.gp_cond_wi= [KNL]
+ Nominal wait interval for normal conditional
+ grace periods (specified by rcutorture's
+ gp_cond and gp_cond_full module parameters),
+ in microseconds. The actual wait interval will
+ be randomly selected to nanosecond granularity up
+ to this wait interval. Defaults to 16 jiffies,
+ for example, 16,000 microseconds on a system
+ with HZ=1000.
+
+ rcutorture.gp_cond_wi_exp= [KNL]
+ Nominal wait interval for expedited conditional
+ grace periods (specified by rcutorture's
+ gp_cond_exp and gp_cond_exp_full module
+ parameters), in microseconds. The actual wait
+ interval will be randomly selected to nanosecond
+ granularity up to this wait interval. Defaults to
+ 128 microseconds.
rcutorture.gp_exp= [KNL]
Use expedited update-side primitives, if available.
Use normal (non-expedited) asynchronous
update-side primitives, if available.
+ rcutorture.gp_poll= [KNL]
+ Use polled update-side normal-grace-period
+ primitives, if available.
+
+ rcutorture.gp_poll_exp= [KNL]
+ Use polled update-side expedited-grace-period
+ primitives, if available.
+
+ rcutorture.gp_poll_full= [KNL]
+ Use polled update-side normal-grace-period
+ primitives that also take concurrent expedited
+ grace periods into account, if available.
+
+ rcutorture.gp_poll_exp_full= [KNL]
+ Use polled update-side expedited-grace-period
+ primitives that also take concurrent normal
+ grace periods into account, if available.
+
+ rcutorture.gp_poll_wi= [KNL]
+ Nominal wait interval for normal conditional
+ grace periods (specified by rcutorture's
+ gp_poll and gp_poll_full module parameters),
+ in microseconds. The actual wait interval will
+ be randomly selected to nanosecond granularity up
+ to this wait interval. Defaults to 16 jiffies,
+ for example, 16,000 microseconds on a system
+ with HZ=1000.
+
+ rcutorture.gp_poll_wi_exp= [KNL]
+ Nominal wait interval for expedited conditional
+ grace periods (specified by rcutorture's
+ gp_poll_exp and gp_poll_exp_full module
+ parameters), in microseconds. The actual wait
+ interval will be randomly selected to nanosecond
+ granularity up to this wait interval. Defaults to
+ 128 microseconds.
+
rcutorture.gp_sync= [KNL]
Use normal (non-expedited) synchronous
update-side primitives, if available. If all
Set time (jiffies) between CPU-hotplug operations,
or zero to disable CPU-hotplug testing.
+ rcutorture.preempt_duration= [KNL]
+ Set duration (in milliseconds) of preemptions
+ by a high-priority FIFO real-time task. Set to
+ zero (the default) to disable. The CPUs to
+ preempt are selected randomly from the set that
+ are online at a given point in time. Races with
+ CPUs going offline are ignored, with that attempt
+ at preemption skipped.
+
+ rcutorture.preempt_interval= [KNL]
+ Set interval (in milliseconds, defaulting to one
+ second) between preemptions by a high-priority
+ FIFO real-time task. This delay is mediated
+ by an hrtimer and is further fuzzed to avoid
+ inadvertent synchronizations.
+
rcutorture.read_exit_burst= [KNL]
The number of times in a given read-then-exit
episode that a set of read-then-exit kthreads
reboot_cpu is s[mp]#### with #### being the processor
to be used for rebooting.
+ acpi
+ Use the ACPI RESET_REG in the FADT. If ACPI is not
+ configured or the ACPI reset does not work, the reboot
+ path attempts the reset using the keyboard controller.
+
+ bios
+ Use the CPU reboot vector for warm reset
+
+ cold
+ Set the cold reboot flag
+
+ default
+ There are some built-in platform specific "quirks"
+ - you may see: "reboot: <name> series board detected.
+ Selecting <type> for reboots." In the case where you
+ think the quirk is in error (e.g. you have newer BIOS,
+ or newer board) using this option will ignore the
+ built-in quirk table, and use the generic default
+ reboot actions.
+
+ efi
+ Use efi reset_system runtime service. If EFI is not
+ configured or the EFI reset does not work, the reboot
+ path attempts the reset using the keyboard controller.
+
+ force
+ Don't stop other CPUs on reboot. This can make reboot
+ more reliable in some cases.
+
+ kbd
+ Use the keyboard controller. cold reset (default)
+
+ pci
+ Use a write to the PCI config space register 0xcf9 to
+ trigger reboot.
+
+ triple
+ Force a triple fault (init)
+
+ warm
+ Don't set the cold reboot flag
+
+ Using warm reset will be much faster especially on big
+ memory systems because the BIOS will not go through
+ the memory check. Disadvantage is that not all
+ hardware will be completely reinitialized on reboot so
+ there may be boot problems on some systems.
+
+
refscale.holdoff= [KNL]
Set test-start holdoff period. The purpose of
this parameter is to delay the start of the
serialnumber [BUGS=X86-32]
- sev=option[,option...] [X86-64] See Documentation/arch/x86/x86_64/boot-options.rst
+ sev=option[,option...] [X86-64]
+
+ debug
+ Enable debug messages.
+
+ nosnp
+ Do not enable SEV-SNP (applies to host/hypervisor
+ only). Setting 'nosnp' avoids the RMP check overhead
+ in memory accesses when users do not want to run
+ SEV-SNP guests.
shapers= [NET]
Maximal number of shapers.
comma-separated list of trace events to enable. See
also Documentation/trace/events.rst
+ To enable modules, use :mod: keyword:
+
+ trace_event=:mod:<module>
+
+ The value before :mod: will only enable specific events
+ that are part of the module. See the above mentioned
+ document for more information.
+
trace_instance=[instance-info]
[FTRACE] Create a ring buffer instance early in boot up.
This will be listed in:
vt.cur_default= [VT] Default cursor shape.
Format: 0xCCBBAA, where AA, BB, and CC are the same as
the parameters of the <Esc>[?A;B;Cc escape sequence;
- see VGA-softcursor.txt. Default: 2 = underline.
+ see vga-softcursor.rst. Default: 2 = underline.
vt.default_blu= [VT]
Format: <blue0>,<blue1>,<blue2>,...,<blue15>
projects / linux.git / blobdiff