diff options
Diffstat (limited to 'Documentation/admin-guide/kernel-parameters.txt')
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 244 |
1 files changed, 149 insertions, 95 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index c5e7bb4babf0..85fb0fa5d091 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1,17 +1,17 @@ - acpi= [HW,ACPI,X86,ARM64] + acpi= [HW,ACPI,X86,ARM64,RISCV64] Advanced Configuration and Power Interface Format: { force | on | off | strict | noirq | rsdt | copy_dsdt } force -- enable ACPI if default was off - on -- enable ACPI but allow fallback to DT [arm64] + on -- enable ACPI but allow fallback to DT [arm64,riscv64] off -- disable ACPI if default was on noirq -- do not use ACPI for IRQ routing strict -- Be less tolerant of platforms that are not strictly ACPI specification compliant. rsdt -- prefer RSDT over (default) XSDT copy_dsdt -- copy DSDT to memory - For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force" - are available + For ARM64 and RISCV64, ONLY "acpi=off", "acpi=on" or + "acpi=force" are available See also Documentation/power/runtime_pm.rst, pci=noacpi @@ -304,7 +304,7 @@ EL0 is indicated by /sys/devices/system/cpu/aarch32_el0 and hot-unplug operations may be restricted. - See Documentation/arm64/asymmetric-32bit.rst for more + See Documentation/arch/arm64/asymmetric-32bit.rst for more information. amd_iommu= [HW,X86-64] @@ -323,6 +323,7 @@ option with care. pgtbl_v1 - Use v1 page table for DMA-API (Default). pgtbl_v2 - Use v2 page table for DMA-API. + irtcachedis - Disable Interrupt Remapping Table (IRT) caching. amd_iommu_dump= [HW,X86-64] Enable AMD IOMMU driver option to dump the ACPI table @@ -2112,6 +2113,16 @@ disable Do not enable intel_pstate as the default scaling driver for the supported processors + active + Use intel_pstate driver to bypass the scaling + governors layer of cpufreq and provides it own + algorithms for p-state selection. There are two + P-state selection algorithms provided by + intel_pstate in the active mode: powersave and + performance. The way they both operate depends + on whether or not the hardware managed P-states + (HWP) feature has been enabled in the processor + and possibly on the processor model. passive Use intel_pstate as a scaling driver, but configure it to work with generic cpufreq governors (instead of @@ -2546,12 +2557,13 @@ If the value is 0 (the default), KVM will pick a period based on the ratio, such that a page is zapped after 1 hour on average. - kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM. - Default is 1 (enabled) + kvm-amd.nested= [KVM,AMD] Control nested virtualization feature in + KVM/SVM. Default is 1 (enabled). - kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU) - for all guests. - Default is 1 (enabled) if in 64-bit or 32-bit PAE mode. + kvm-amd.npt= [KVM,AMD] Control KVM's use of Nested Page Tables, + a.k.a. Two-Dimensional Page Tables. Default is 1 + (enabled). Disable by KVM if hardware lacks support + for NPT. kvm-arm.mode= [KVM,ARM] Select one of KVM/arm64's modes of operation. @@ -2597,30 +2609,33 @@ Format: <integer> Default: 5 - kvm-intel.ept= [KVM,Intel] Disable extended page tables - (virtualized MMU) support on capable Intel chips. - Default is 1 (enabled) + kvm-intel.ept= [KVM,Intel] Control KVM's use of Extended Page Tables, + a.k.a. Two-Dimensional Page Tables. Default is 1 + (enabled). Disable by KVM if hardware lacks support + for EPT. kvm-intel.emulate_invalid_guest_state= - [KVM,Intel] Disable emulation of invalid guest state. - Ignored if kvm-intel.enable_unrestricted_guest=1, as - guest state is never invalid for unrestricted guests. - This param doesn't apply to nested guests (L2), as KVM - never emulates invalid L2 guest state. - Default is 1 (enabled) + [KVM,Intel] Control whether to emulate invalid guest + state. Ignored if kvm-intel.enable_unrestricted_guest=1, + as guest state is never invalid for unrestricted + guests. This param doesn't apply to nested guests (L2), + as KVM never emulates invalid L2 guest state. + Default is 1 (enabled). kvm-intel.flexpriority= - [KVM,Intel] Disable FlexPriority feature (TPR shadow). - Default is 1 (enabled) + [KVM,Intel] Control KVM's use of FlexPriority feature + (TPR shadow). Default is 1 (enabled). Disalbe by KVM if + hardware lacks support for it. kvm-intel.nested= - [KVM,Intel] Enable VMX nesting (nVMX). - Default is 0 (disabled) + [KVM,Intel] Control nested virtualization feature in + KVM/VMX. Default is 1 (enabled). kvm-intel.unrestricted_guest= - [KVM,Intel] Disable unrestricted guest feature - (virtualized real and unpaged mode) on capable - Intel chips. Default is 1 (enabled) + [KVM,Intel] Control KVM's use of unrestricted guest + feature (virtualized real and unpaged mode). Default + is 1 (enabled). Disable by KVM if EPT is disabled or + hardware lacks support for it. kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault CVE-2018-3620. @@ -2634,9 +2649,10 @@ Default is cond (do L1 cache flush in specific instances) - kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification - feature (tagged TLBs) on capable Intel chips. - Default is 1 (enabled) + kvm-intel.vpid= [KVM,Intel] Control KVM's use of Virtual Processor + Identification feature (tagged TLBs). Default is 1 + (enabled). Disable by KVM if hardware lacks support + for it. l1d_flush= [X86,INTEL] Control mitigation for L1D based snooping vulnerability. @@ -3418,6 +3434,10 @@ [HW] Make the MicroTouch USB driver use raw coordinates ('y', default) or cooked coordinates ('n') + mtrr=debug [X86] + Enable printing debug information related to MTRR + registers at boot time. + mtrr_chunk_size=nn[KMG] [X86] used for mtrr cleanup. It is largest continuous chunk that could hold holes aka. UC entries. @@ -3697,8 +3717,8 @@ nohibernate [HIBERNATION] Disable hibernation and resume. - nohlt [ARM,ARM64,MICROBLAZE,SH] Forces the kernel to busy wait - in do_idle() and not use the arch_cpu_idle() + nohlt [ARM,ARM64,MICROBLAZE,MIPS,SH] Forces the kernel to + busy wait in do_idle() and not use the arch_cpu_idle() implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP to be effective. This is useful on platforms where the sleep(SH) or wfi(ARM,ARM64) instructions do not work @@ -3833,7 +3853,7 @@ nosmp [SMP] Tells an SMP kernel to act as a UP kernel, and disable the IO APIC. legacy for "maxcpus=0". - nosmt [KNL,S390] Disable symmetric multithreading (SMT). + nosmt [KNL,MIPS,S390] Disable symmetric multithreading (SMT). Equivalent to smt=1. [KNL,X86] Disable symmetric multithreading (SMT). @@ -4731,43 +4751,6 @@ the propagation of recent CPU-hotplug changes up the rcu_node combining tree. - rcutree.use_softirq= [KNL] - If set to zero, move all RCU_SOFTIRQ processing to - per-CPU rcuc kthreads. Defaults to a non-zero - value, meaning that RCU_SOFTIRQ is used by default. - Specify rcutree.use_softirq=0 to use rcuc kthreads. - - But note that CONFIG_PREEMPT_RT=y kernels disable - this kernel boot parameter, forcibly setting it - to zero. - - rcutree.rcu_fanout_exact= [KNL] - Disable autobalancing of the rcu_node combining - tree. This is used by rcutorture, and might - possibly be useful for architectures having high - cache-to-cache transfer latencies. - - rcutree.rcu_fanout_leaf= [KNL] - Change the number of CPUs assigned to each - leaf rcu_node structure. Useful for very - large systems, which will choose the value 64, - and for NUMA systems with large remote-access - latencies, which will choose a value aligned - with the appropriate hardware boundaries. - - rcutree.rcu_min_cached_objs= [KNL] - Minimum number of objects which are cached and - maintained per one CPU. Object size is equal - to PAGE_SIZE. The cache allows to reduce the - pressure to page allocator, also it makes the - whole algorithm to behave better in low memory - condition. - - rcutree.rcu_delay_page_cache_fill_msec= [KNL] - Set the page-cache refill delay (in milliseconds) - in response to low-memory conditions. The range - of permitted values is in the range 0:100000. - rcutree.jiffies_till_first_fqs= [KNL] Set delay from grace-period initialization to first attempt to force quiescent states. @@ -4806,21 +4789,6 @@ When RCU_NOCB_CPU is set, also adjust the priority of NOCB callback kthreads. - rcutree.rcu_divisor= [KNL] - Set the shift-right count to use to compute - the callback-invocation batch limit bl from - the number of callbacks queued on this CPU. - The result will be bounded below by the value of - the rcutree.blimit kernel parameter. Every bl - callbacks, the softirq handler will exit in - order to allow the CPU to do other work. - - Please note that this callback-invocation batch - limit applies only to non-offloaded callback - invocation. Offloaded callbacks are instead - invoked in the context of an rcuoc kthread, which - scheduler will preempt as it does any other task. - rcutree.nocb_nobypass_lim_per_jiffy= [KNL] On callback-offloaded (rcu_nocbs) CPUs, RCU reduces the lock contention that would @@ -4834,14 +4802,6 @@ the ->nocb_bypass queue. The definition of "too many" is supplied by this kernel boot parameter. - rcutree.rcu_nocb_gp_stride= [KNL] - Set the number of NOCB callback kthreads in - each group, which defaults to the square root - of the number of CPUs. Larger numbers reduce - the wakeup overhead on the global grace-period - kthread, but increases that same overhead on - each group's NOCB grace-period kthread. - rcutree.qhimark= [KNL] Set threshold of queued RCU callbacks beyond which batch limiting is disabled. @@ -4859,6 +4819,56 @@ on rcutree.qhimark at boot time and to zero to disable more aggressive help enlistment. + rcutree.rcu_delay_page_cache_fill_msec= [KNL] + Set the page-cache refill delay (in milliseconds) + in response to low-memory conditions. The range + of permitted values is in the range 0:100000. + + rcutree.rcu_divisor= [KNL] + Set the shift-right count to use to compute + the callback-invocation batch limit bl from + the number of callbacks queued on this CPU. + The result will be bounded below by the value of + the rcutree.blimit kernel parameter. Every bl + callbacks, the softirq handler will exit in + order to allow the CPU to do other work. + + Please note that this callback-invocation batch + limit applies only to non-offloaded callback + invocation. Offloaded callbacks are instead + invoked in the context of an rcuoc kthread, which + scheduler will preempt as it does any other task. + + rcutree.rcu_fanout_exact= [KNL] + Disable autobalancing of the rcu_node combining + tree. This is used by rcutorture, and might + possibly be useful for architectures having high + cache-to-cache transfer latencies. + + rcutree.rcu_fanout_leaf= [KNL] + Change the number of CPUs assigned to each + leaf rcu_node structure. Useful for very + large systems, which will choose the value 64, + and for NUMA systems with large remote-access + latencies, which will choose a value aligned + with the appropriate hardware boundaries. + + rcutree.rcu_min_cached_objs= [KNL] + Minimum number of objects which are cached and + maintained per one CPU. Object size is equal + to PAGE_SIZE. The cache allows to reduce the + pressure to page allocator, also it makes the + whole algorithm to behave better in low memory + condition. + + rcutree.rcu_nocb_gp_stride= [KNL] + Set the number of NOCB callback kthreads in + each group, which defaults to the square root + of the number of CPUs. Larger numbers reduce + the wakeup overhead on the global grace-period + kthread, but increases that same overhead on + each group's NOCB grace-period kthread. + rcutree.rcu_kick_kthreads= [KNL] Cause the grace-period kthread to get an extra wake_up() if it sleeps three times longer than @@ -4866,6 +4876,13 @@ This wake_up() will be accompanied by a WARN_ONCE() splat and an ftrace_dump(). + rcutree.rcu_resched_ns= [KNL] + Limit the time spend invoking a batch of RCU + callbacks to the specified number of nanoseconds. + By default, this limit is checked only once + every 32 callbacks in order to limit the pain + inflicted by local_clock() overhead. + rcutree.rcu_unlock_delay= [KNL] In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels, this specifies an rcu_read_unlock()-time delay @@ -4880,6 +4897,16 @@ rcu_node tree with an eye towards determining why a new grace period has not yet started. + rcutree.use_softirq= [KNL] + If set to zero, move all RCU_SOFTIRQ processing to + per-CPU rcuc kthreads. Defaults to a non-zero + value, meaning that RCU_SOFTIRQ is used by default. + Specify rcutree.use_softirq=0 to use rcuc kthreads. + + But note that CONFIG_PREEMPT_RT=y kernels disable + this kernel boot parameter, forcibly setting it + to zero. + rcuscale.gp_async= [KNL] Measure performance of asynchronous grace-period primitives such as call_rcu(). @@ -5082,8 +5109,17 @@ rcutorture.stall_cpu_block= [KNL] Sleep while stalling if set. This will result - in warnings from preemptible RCU in addition - to any other stall-related activity. + in warnings from preemptible RCU in addition to + any other stall-related activity. Note that + in kernels built with CONFIG_PREEMPTION=n and + CONFIG_PREEMPT_COUNT=y, this parameter will + cause the CPU to pass through a quiescent state. + Given CONFIG_PREEMPTION=n, this will suppress + RCU CPU stall warnings, but will instead result + in scheduling-while-atomic splats. + + Use of this module parameter results in splats. + rcutorture.stall_cpu_holdoff= [KNL] Time to wait (s) after boot before inducing stall. @@ -5735,7 +5771,7 @@ 1: Fast pin select (default) 2: ATC IRMode - smt= [KNL,S390] Set the maximum number of threads (logical + smt= [KNL,MIPS,S390] Set the maximum number of threads (logical CPUs) to use per physical CPU on systems capable of symmetric multithreading (SMT). Will be capped to the actual hardware limit. @@ -6563,6 +6599,12 @@ unknown_nmi_panic [X86] Cause panic on unknown NMI. + unwind_debug [X86-64] + Enable unwinder debug output. This can be + useful for debugging certain unwinder error + conditions, including corrupt stacks and + bad/missing unwinder metadata. + usbcore.authorized_default= [USB] Default USB device authorization: (default -1 = authorized except for wireless USB, @@ -6931,6 +6973,18 @@ it can be updated at runtime by writing to the corresponding sysfs file. + workqueue.cpu_intensive_thresh_us= + Per-cpu work items which run for longer than this + threshold are automatically considered CPU intensive + and excluded from concurrency management to prevent + them from noticeably delaying other per-cpu work + items. Default is 10000 (10ms). + + If CONFIG_WQ_CPU_INTENSIVE_REPORT is set, the kernel + will report the work functions which violate this + threshold repeatedly. They are likely good + candidates for using WQ_UNBOUND workqueues instead. + workqueue.disable_numa By default, all work items queued to unbound workqueues are affine to the NUMA nodes they're |