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Diffstat (limited to 'Documentation/admin-guide/kernel-parameters.txt')
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 348 |
1 files changed, 332 insertions, 16 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index dc663c0ca670..8fbb481db515 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -21,6 +21,10 @@ 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 @@ -405,6 +409,8 @@ 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 } @@ -424,6 +430,10 @@ 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. @@ -1726,6 +1736,8 @@ 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. @@ -2008,12 +2020,21 @@ 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] @@ -2311,20 +2332,73 @@ 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 @@ -2432,7 +2506,9 @@ 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 @@ -2695,7 +2771,7 @@ 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, @@ -3259,9 +3335,77 @@ 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. @@ -3887,6 +4031,8 @@ 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] @@ -3934,6 +4080,8 @@ 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 @@ -3960,6 +4108,8 @@ 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. @@ -4111,8 +4261,10 @@ 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. @@ -4192,6 +4344,11 @@ 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 @@ -4822,6 +4979,11 @@ can be preempted anytime. Tasks will also yield contended spinlocks (if the critical section isn't explicitly preempt disabled beyond the lock itself). + lazy - Scheduler controlled. Similar to full but instead + of preempting the task immediately, the task gets + one HZ tick time to yield itself before the + preemption will be forced. One preemption is when the + task returns to user space. print-fatal-signals= [KNL] debug: print fatal signals @@ -5362,7 +5524,42 @@ 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. @@ -5371,6 +5568,43 @@ 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 @@ -5424,6 +5658,22 @@ 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 @@ -5710,6 +5960,55 @@ 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 @@ -6101,7 +6400,16 @@ 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. @@ -6853,6 +7161,14 @@ 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: @@ -7469,7 +7785,7 @@ 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> |