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linux/Documentation/ABI/testing/sysfs-devices-system-cpu
Linus Torvalds 47cf96fbe3 arm64 updates for 6.16 
ACPI, EFI and PSCI:
  - Decouple Arm's "Software Delegated Exception Interface" (SDEI)
    support from the ACPI GHES code so that it can be used by platforms
    booted with device-tree.
 
  - Remove unnecessary per-CPU tracking of the FPSIMD state across EFI
    runtime calls.
 
  - Fix a node refcount imbalance in the PSCI device-tree code.
 
 CPU Features:
  - Ensure register sanitisation is applied to fields in ID_AA64MMFR4.
 
  - Expose AIDR_EL1 to userspace via sysfs, primarily so that KVM guests
    can reliably query the underlying CPU types from the VMM.
 
  - Re-enabling of SME support (CONFIG_ARM64_SME) as a result of fixes
    to our context-switching, signal handling and ptrace code.
 
 Entry code:
  - Hook up TIF_NEED_RESCHED_LAZY so that CONFIG_PREEMPT_LAZY can be
    selected.
 
 Memory management:
  - Prevent BSS exports from being used by the early PI code.
 
  - Propagate level and stride information to the low-level TLB
    invalidation routines when operating on hugetlb entries.
 
  - Use the page-table contiguous hint for vmap() mappings with
    VM_ALLOW_HUGE_VMAP where possible.
 
  - Optimise vmalloc()/vmap() page-table updates to use "lazy MMU mode"
    and hook this up on arm64 so that the trailing DSB (used to publish
    the updates to the hardware walker) can be deferred until the end of
    the mapping operation.
 
  - Extend mmap() randomisation for 52-bit virtual addresses (on par with
    48-bit addressing) and remove limited support for randomisation of
    the linear map.
 
 Perf and PMUs:
  - Add support for probing the CMN-S3 driver using ACPI.
 
  - Minor driver fixes to the CMN, Arm-NI and amlogic PMU drivers.
 
 Selftests:
  - Fix FPSIMD and SME tests to align with the freshly re-enabled SME
    support.
 
  - Fix default setting of the OUTPUT variable so that tests are
    installed in the right location.
 
 vDSO:
  - Replace raw counter access from inline assembly code with a call to
    the the __arch_counter_get_cntvct() helper function.
 
 Miscellaneous:
  - Add some missing header inclusions to the CCA headers.
 
  - Rework rendering of /proc/cpuinfo to follow the x86-approach and
    avoid repeated buffer expansion (the user-visible format remains
    identical).
 
  - Remove redundant selection of CONFIG_CRC32
 
  - Extend early error message when failing to map the device-tree blob.
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Merge tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

Pull arm64 updates from Will Deacon:
 "The headline feature is the re-enablement of support for Arm's
  Scalable Matrix Extension (SME) thanks to a bumper crop of fixes
  from Mark Rutland.

  If matrices aren't your thing, then Ryan's page-table optimisation
  work is much more interesting.

  Summary:

  ACPI, EFI and PSCI:

   - Decouple Arm's "Software Delegated Exception Interface" (SDEI)
     support from the ACPI GHES code so that it can be used by platforms
     booted with device-tree

   - Remove unnecessary per-CPU tracking of the FPSIMD state across EFI
     runtime calls

   - Fix a node refcount imbalance in the PSCI device-tree code

  CPU Features:

   - Ensure register sanitisation is applied to fields in ID_AA64MMFR4

   - Expose AIDR_EL1 to userspace via sysfs, primarily so that KVM
     guests can reliably query the underlying CPU types from the VMM

   - Re-enabling of SME support (CONFIG_ARM64_SME) as a result of fixes
     to our context-switching, signal handling and ptrace code

  Entry code:

   - Hook up TIF_NEED_RESCHED_LAZY so that CONFIG_PREEMPT_LAZY can be
     selected

  Memory management:

   - Prevent BSS exports from being used by the early PI code

   - Propagate level and stride information to the low-level TLB
     invalidation routines when operating on hugetlb entries

   - Use the page-table contiguous hint for vmap() mappings with
     VM_ALLOW_HUGE_VMAP where possible

   - Optimise vmalloc()/vmap() page-table updates to use "lazy MMU mode"
     and hook this up on arm64 so that the trailing DSB (used to publish
     the updates to the hardware walker) can be deferred until the end
     of the mapping operation

   - Extend mmap() randomisation for 52-bit virtual addresses (on par
     with 48-bit addressing) and remove limited support for
     randomisation of the linear map

  Perf and PMUs:

   - Add support for probing the CMN-S3 driver using ACPI

   - Minor driver fixes to the CMN, Arm-NI and amlogic PMU drivers

  Selftests:

   - Fix FPSIMD and SME tests to align with the freshly re-enabled SME
     support

   - Fix default setting of the OUTPUT variable so that tests are
     installed in the right location

  vDSO:

   - Replace raw counter access from inline assembly code with a call to
     the the __arch_counter_get_cntvct() helper function

  Miscellaneous:

   - Add some missing header inclusions to the CCA headers

   - Rework rendering of /proc/cpuinfo to follow the x86-approach and
     avoid repeated buffer expansion (the user-visible format remains
     identical)

   - Remove redundant selection of CONFIG_CRC32

   - Extend early error message when failing to map the device-tree
     blob"

* tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux: (83 commits)
  arm64: cputype: Add cputype definition for HIP12
  arm64: el2_setup.h: Make __init_el2_fgt labels consistent, again
  perf/arm-cmn: Add CMN S3 ACPI binding
  arm64/boot: Disallow BSS exports to startup code
  arm64/boot: Move global CPU override variables out of BSS
  arm64/boot: Move init_pgdir[] and init_idmap_pgdir[] into __pi_ namespace
  perf/arm-cmn: Initialise cmn->cpu earlier
  kselftest/arm64: Set default OUTPUT path when undefined
  arm64: Update comment regarding values in __boot_cpu_mode
  arm64: mm: Drop redundant check in pmd_trans_huge()
  arm64/mm: Re-organise setting up FEAT_S1PIE registers PIRE0_EL1 and PIR_EL1
  arm64/mm: Permit lazy_mmu_mode to be nested
  arm64/mm: Disable barrier batching in interrupt contexts
  arm64/cpuinfo: only show one cpu's info in c_show()
  arm64/mm: Batch barriers when updating kernel mappings
  mm/vmalloc: Enter lazy mmu mode while manipulating vmalloc ptes
  arm64/mm: Support huge pte-mapped pages in vmap
  mm/vmalloc: Gracefully unmap huge ptes
  mm/vmalloc: Warn on improper use of vunmap_range()
  arm64/mm: Hoist barriers out of set_ptes_anysz() loop
  ...
2025-05-28 14:55:35 -07:00

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What: /sys/devices/system/cpu/
Date: pre-git history
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
Description:
A collection of both global and individual CPU attributes
Individual CPU attributes are contained in subdirectories
named by the kernel's logical CPU number, e.g.:
/sys/devices/system/cpu/cpuX/
What: /sys/devices/system/cpu/kernel_max
/sys/devices/system/cpu/offline
/sys/devices/system/cpu/online
/sys/devices/system/cpu/possible
/sys/devices/system/cpu/present
Date: December 2008
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
Description: CPU topology files that describe kernel limits related to
hotplug. Briefly:
kernel_max: the maximum cpu index allowed by the kernel
configuration.
offline: cpus that are not online because they have been
HOTPLUGGED off or exceed the limit of cpus allowed by the
kernel configuration (kernel_max above).
online: cpus that are online and being scheduled.
possible: cpus that have been allocated resources and can be
brought online if they are present.
present: cpus that have been identified as being present in
the system.
See Documentation/admin-guide/cputopology.rst for more information.
What: /sys/devices/system/cpu/probe
/sys/devices/system/cpu/release
Date: November 2009
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
Description: Dynamic addition and removal of CPU's. This is not hotplug
removal, this is meant complete removal/addition of the CPU
from the system.
probe: writes to this file will dynamically add a CPU to the
system. Information written to the file to add CPU's is
architecture specific.
release: writes to this file dynamically remove a CPU from
the system. Information written to the file to remove CPU's
is architecture specific.
What: /sys/devices/system/cpu/cpuX/node
Date: October 2009
Contact: Linux memory management mailing list <linux-mm@kvack.org>
Description: Discover NUMA node a CPU belongs to
When CONFIG_NUMA is enabled, a symbolic link that points
to the corresponding NUMA node directory.
For example, the following symlink is created for cpu42
in NUMA node 2:
/sys/devices/system/cpu/cpu42/node2 -> ../../node/node2
What: /sys/devices/system/cpu/cpuX/topology/core_siblings
/sys/devices/system/cpu/cpuX/topology/core_siblings_list
/sys/devices/system/cpu/cpuX/topology/physical_package_id
/sys/devices/system/cpu/cpuX/topology/thread_siblings
/sys/devices/system/cpu/cpuX/topology/thread_siblings_list
/sys/devices/system/cpu/cpuX/topology/ppin
Date: December 2008
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
Description: CPU topology files that describe a logical CPU's relationship
to other cores and threads in the same physical package.
One cpuX directory is created per logical CPU in the system,
e.g. /sys/devices/system/cpu/cpu42/.
Briefly, the files above are:
core_siblings: internal kernel map of cpuX's hardware threads
within the same physical_package_id.
core_siblings_list: human-readable list of the logical CPU
numbers within the same physical_package_id as cpuX.
physical_package_id: physical package id of cpuX. Typically
corresponds to a physical socket number, but the actual value
is architecture and platform dependent.
thread_siblings: internal kernel map of cpuX's hardware
threads within the same core as cpuX
thread_siblings_list: human-readable list of cpuX's hardware
threads within the same core as cpuX
ppin: human-readable Protected Processor Identification
Number of the socket the cpu# belongs to. There should be
one per physical_package_id. File is readable only to
admin.
See Documentation/admin-guide/cputopology.rst for more information.
What: /sys/devices/system/cpu/cpuidle/available_governors
/sys/devices/system/cpu/cpuidle/current_driver
/sys/devices/system/cpu/cpuidle/current_governor
/sys/devices/system/cpu/cpuidle/current_governer_ro
/sys/devices/system/cpu/cpuidle/intel_c1_demotion
Date: September 2007
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
Description: Discover cpuidle policy and mechanism
Various CPUs today support multiple idle levels that are
differentiated by varying exit latencies and power
consumption during idle.
Idle policy (governor) is differentiated from idle mechanism
(driver).
available_governors: (RO) displays a space separated list of
available governors.
current_driver: (RO) displays current idle mechanism.
current_governor: (RW) displays current idle policy. Users can
switch the governor at runtime by writing to this file.
current_governor_ro: (RO) displays current idle policy.
intel_c1_demotion: (RW) enables/disables the C1 demotion
feature on Intel CPUs.
See Documentation/admin-guide/pm/cpuidle.rst,
Documentation/admin-guide/pm/intel_idle.rst, and
Documentation/driver-api/pm/cpuidle.rst for more information.
What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/name
/sys/devices/system/cpu/cpuX/cpuidle/stateN/latency
/sys/devices/system/cpu/cpuX/cpuidle/stateN/power
/sys/devices/system/cpu/cpuX/cpuidle/stateN/time
/sys/devices/system/cpu/cpuX/cpuidle/stateN/usage
/sys/devices/system/cpu/cpuX/cpuidle/stateN/above
/sys/devices/system/cpu/cpuX/cpuidle/stateN/below
Date: September 2007
KernelVersion: v2.6.24
Contact: Linux power management list <linux-pm@vger.kernel.org>
Description:
The directory /sys/devices/system/cpu/cpuX/cpuidle contains per
logical CPU specific cpuidle information for each online cpu X.
The processor idle states which are available for use have the
following attributes:
======== ==== =================================================
name: (RO) Name of the idle state (string).
latency: (RO) The latency to exit out of this idle state (in
microseconds).
power: (RO) The power consumed while in this idle state (in
milliwatts).
time: (RO) The total time spent in this idle state
(in microseconds).
usage: (RO) Number of times this state was entered (a count).
above: (RO) Number of times this state was entered, but the
observed CPU idle duration was too short for it
(a count).
below: (RO) Number of times this state was entered, but the
observed CPU idle duration was too long for it
(a count).
======== ==== =================================================
What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/desc
Date: February 2008
KernelVersion: v2.6.25
Contact: Linux power management list <linux-pm@vger.kernel.org>
Description:
(RO) A small description about the idle state (string).
What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/disable
Date: March 2012
KernelVersion: v3.10
Contact: Linux power management list <linux-pm@vger.kernel.org>
Description:
(RW) Option to disable this idle state (bool). The behavior and
the effect of the disable variable depends on the implementation
of a particular governor. In the ladder governor, for example,
it is not coherent, i.e. if one is disabling a light state, then
all deeper states are disabled as well, but the disable variable
does not reflect it. Likewise, if one enables a deep state but a
lighter state still is disabled, then this has no effect.
What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/default_status
Date: December 2019
KernelVersion: v5.6
Contact: Linux power management list <linux-pm@vger.kernel.org>
Description:
(RO) The default status of this state, "enabled" or "disabled".
What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/residency
Date: March 2014
KernelVersion: v3.15
Contact: Linux power management list <linux-pm@vger.kernel.org>
Description:
(RO) Display the target residency i.e. the minimum amount of
time (in microseconds) this cpu should spend in this idle state
to make the transition worth the effort.
What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/s2idle/
Date: March 2018
KernelVersion: v4.17
Contact: Linux power management list <linux-pm@vger.kernel.org>
Description:
Idle state usage statistics related to suspend-to-idle.
This attribute group is only present for states that can be
used in suspend-to-idle with suspended timekeeping.
What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/s2idle/time
Date: March 2018
KernelVersion: v4.17
Contact: Linux power management list <linux-pm@vger.kernel.org>
Description:
Total time spent by the CPU in suspend-to-idle (with scheduler
tick suspended) after requesting this state.
What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/s2idle/usage
Date: March 2018
KernelVersion: v4.17
Contact: Linux power management list <linux-pm@vger.kernel.org>
Description:
Total number of times this state has been requested by the CPU
while entering suspend-to-idle.
What: /sys/devices/system/cpu/cpuX/cpufreq/*
Date: pre-git history
Contact: linux-pm@vger.kernel.org
Description: Discover and change clock speed of CPUs
Clock scaling allows you to change the clock speed of the
CPUs on the fly. This is a nice method to save battery
power, because the lower the clock speed, the less power
the CPU consumes.
There are many knobs to tweak in this directory.
See files in Documentation/cpu-freq/ for more information.
What: /sys/devices/system/cpu/cpuX/cpufreq/freqdomain_cpus
Date: June 2013
Contact: linux-pm@vger.kernel.org
Description: Discover CPUs in the same CPU frequency coordination domain
freqdomain_cpus is the list of CPUs (online+offline) that share
the same clock/freq domain (possibly at the hardware level).
That information may be hidden from the cpufreq core and the
value of related_cpus may be different from freqdomain_cpus. This
attribute is useful for user space DVFS controllers to get better
power/performance results for platforms using acpi-cpufreq.
This file is only present if the acpi-cpufreq or the cppc-cpufreq
drivers are in use.
What: /sys/devices/system/cpu/cpuX/cpufreq/auto_select
Date: May 2025
Contact: linux-pm@vger.kernel.org
Description: Autonomous selection enable
Read/write interface to control autonomous selection enable
Read returns autonomous selection status:
0: autonomous selection is disabled
1: autonomous selection is enabled
Write 'y' or '1' or 'on' to enable autonomous selection.
Write 'n' or '0' or 'off' to disable autonomous selection.
This file is only present if the cppc-cpufreq driver is in use.
What: /sys/devices/system/cpu/cpuX/cpufreq/auto_act_window
Date: May 2025
Contact: linux-pm@vger.kernel.org
Description: Autonomous activity window
This file indicates a moving utilization sensitivity window to
the platform's autonomous selection policy.
Read/write an integer represents autonomous activity window (in
microseconds) from/to this file. The max value to write is
1270000000 but the max significand is 127. This means that if 128
is written to this file, 127 will be stored. If the value is
greater than 130, only the first two digits will be saved as
significand.
Writing a zero value to this file enable the platform to
determine an appropriate Activity Window depending on the workload.
Writing to this file only has meaning when Autonomous Selection is
enabled.
This file is only present if the cppc-cpufreq driver is in use.
What: /sys/devices/system/cpu/cpuX/cpufreq/energy_performance_preference_val
Date: May 2025
Contact: linux-pm@vger.kernel.org
Description: Energy performance preference
Read/write an 8-bit integer from/to this file. This file
represents a range of values from 0 (performance preference) to
0xFF (energy efficiency preference) that influences the rate of
performance increase/decrease and the result of the hardware's
energy efficiency and performance optimization policies.
Writing to this file only has meaning when Autonomous Selection is
enabled.
This file is only present if the cppc-cpufreq driver is in use.
What: /sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1}
Date: August 2008
KernelVersion: 2.6.27
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
Description: Disable L3 cache indices
These files exist in every CPU's cache/index3 directory. Each
cache_disable_{0,1} file corresponds to one disable slot which
can be used to disable a cache index. Reading from these files
on a processor with this functionality will return the currently
disabled index for that node. There is one L3 structure per
node, or per internal node on MCM machines. Writing a valid
index to one of these files will cause the specified cache
index to be disabled.
All AMD processors with L3 caches provide this functionality.
For details, see BKDGs at
https://www.amd.com/en/support/tech-docs?keyword=bios+kernel
What: /sys/devices/system/cpu/cpufreq/boost
Date: August 2012
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
Description: Processor frequency boosting control
This switch controls the boost setting for the whole system.
Boosting allows the CPU and the firmware to run at a frequency
beyond its nominal limit.
More details can be found in
Documentation/admin-guide/pm/cpufreq.rst
What: /sys/devices/system/cpu/cpuX/crash_notes
/sys/devices/system/cpu/cpuX/crash_notes_size
Date: April 2013
Contact: kexec@lists.infradead.org
Description: address and size of the percpu note.
crash_notes: the physical address of the memory that holds the
note of cpuX.
crash_notes_size: size of the note of cpuX.
What: /sys/devices/system/cpu/intel_pstate/max_perf_pct
/sys/devices/system/cpu/intel_pstate/min_perf_pct
/sys/devices/system/cpu/intel_pstate/no_turbo
Date: February 2013
Contact: linux-pm@vger.kernel.org
Description: Parameters for the Intel P-state driver
Logic for selecting the current P-state in Intel
Sandybridge+ processors. The three knobs control
limits for the P-state that will be requested by the
driver.
max_perf_pct: limits the maximum P state that will be requested by
the driver stated as a percentage of the available performance.
min_perf_pct: limits the minimum P state that will be requested by
the driver stated as a percentage of the available performance.
no_turbo: limits the driver to selecting P states below the turbo
frequency range.
More details can be found in
Documentation/admin-guide/pm/intel_pstate.rst
What: /sys/devices/system/cpu/cpu*/cache/index*/<set_of_attributes_mentioned_below>
Date: July 2014(documented, existed before August 2008)
Contact: Sudeep Holla <sudeep.holla@arm.com>
Linux kernel mailing list <linux-kernel@vger.kernel.org>
Description: Parameters for the CPU cache attributes
allocation_policy:
- WriteAllocate:
allocate a memory location to a cache line
on a cache miss because of a write
- ReadAllocate:
allocate a memory location to a cache line
on a cache miss because of a read
- ReadWriteAllocate:
both writeallocate and readallocate
coherency_line_size:
the minimum amount of data in bytes that gets
transferred from memory to cache
level:
the cache hierarchy in the multi-level cache configuration
number_of_sets:
total number of sets in the cache, a set is a
collection of cache lines with the same cache index
physical_line_partition:
number of physical cache line per cache tag
shared_cpu_list:
the list of logical cpus sharing the cache
shared_cpu_map:
logical cpu mask containing the list of cpus sharing
the cache
size:
the total cache size in kB
type:
- Instruction: cache that only holds instructions
- Data: cache that only caches data
- Unified: cache that holds both data and instructions
ways_of_associativity:
degree of freedom in placing a particular block
of memory in the cache
write_policy:
- WriteThrough:
data is written to both the cache line
and to the block in the lower-level memory
- WriteBack:
data is written only to the cache line and
the modified cache line is written to main
memory only when it is replaced
What: /sys/devices/system/cpu/cpu*/cache/index*/id
Date: September 2016
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
Description: Cache id
The id provides a unique number for a specific instance of
a cache of a particular type. E.g. there may be a level
3 unified cache on each socket in a server and we may
assign them ids 0, 1, 2, ...
Note that id value can be non-contiguous. E.g. level 1
caches typically exist per core, but there may not be a
power of two cores on a socket, so these caches may be
numbered 0, 1, 2, 3, 4, 5, 8, 9, 10, ...
What: /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats
/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/turbo_stat
/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/sub_turbo_stat
/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/unthrottle
/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/powercap
/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overtemp
/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/supply_fault
/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overcurrent
/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/occ_reset
Date: March 2016
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
Linux for PowerPC mailing list <linuxppc-dev@lists.ozlabs.org>
Description: POWERNV CPUFreq driver's frequency throttle stats directory and
attributes
'cpuX/cpufreq/throttle_stats' directory contains the CPU frequency
throttle stat attributes for the chip. The throttle stats of a cpu
is common across all the cpus belonging to a chip. Below are the
throttle attributes exported in the 'throttle_stats' directory:
- turbo_stat : This file gives the total number of times the max
frequency is throttled to lower frequency in turbo (at and above
nominal frequency) range of frequencies.
- sub_turbo_stat : This file gives the total number of times the
max frequency is throttled to lower frequency in sub-turbo(below
nominal frequency) range of frequencies.
- unthrottle : This file gives the total number of times the max
frequency is unthrottled after being throttled.
- powercap : This file gives the total number of times the max
frequency is throttled due to 'Power Capping'.
- overtemp : This file gives the total number of times the max
frequency is throttled due to 'CPU Over Temperature'.
- supply_fault : This file gives the total number of times the
max frequency is throttled due to 'Power Supply Failure'.
- overcurrent : This file gives the total number of times the
max frequency is throttled due to 'Overcurrent'.
- occ_reset : This file gives the total number of times the max
frequency is throttled due to 'OCC Reset'.
The sysfs attributes representing different throttle reasons like
powercap, overtemp, supply_fault, overcurrent and occ_reset map to
the reasons provided by OCC firmware for throttling the frequency.
What: /sys/devices/system/cpu/cpufreq/policyX/throttle_stats
/sys/devices/system/cpu/cpufreq/policyX/throttle_stats/turbo_stat
/sys/devices/system/cpu/cpufreq/policyX/throttle_stats/sub_turbo_stat
/sys/devices/system/cpu/cpufreq/policyX/throttle_stats/unthrottle
/sys/devices/system/cpu/cpufreq/policyX/throttle_stats/powercap
/sys/devices/system/cpu/cpufreq/policyX/throttle_stats/overtemp
/sys/devices/system/cpu/cpufreq/policyX/throttle_stats/supply_fault
/sys/devices/system/cpu/cpufreq/policyX/throttle_stats/overcurrent
/sys/devices/system/cpu/cpufreq/policyX/throttle_stats/occ_reset
Date: March 2016
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
Linux for PowerPC mailing list <linuxppc-dev@lists.ozlabs.org>
Description: POWERNV CPUFreq driver's frequency throttle stats directory and
attributes
'policyX/throttle_stats' directory and all the attributes are same as
the /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats directory and
attributes which give the frequency throttle information of the chip.
What: /sys/devices/system/cpu/cpuX/regs/
/sys/devices/system/cpu/cpuX/regs/identification/
/sys/devices/system/cpu/cpuX/regs/identification/midr_el1
/sys/devices/system/cpu/cpuX/regs/identification/revidr_el1
/sys/devices/system/cpu/cpuX/regs/identification/aidr_el1
/sys/devices/system/cpu/cpuX/regs/identification/smidr_el1
Date: June 2016
Contact: Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org>
Description: AArch64 CPU registers
'identification' directory exposes the CPU ID registers for
identifying model and revision of the CPU and SMCU.
What: /sys/devices/system/cpu/aarch32_el0
Date: May 2021
Contact: Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org>
Description: Identifies the subset of CPUs in the system that can execute
AArch32 (32-bit ARM) applications. If present, the same format as
/sys/devices/system/cpu/{offline,online,possible,present} is used.
If absent, then all or none of the CPUs can execute AArch32
applications and execve() will behave accordingly.
What: /sys/devices/system/cpu/cpuX/cpu_capacity
Date: December 2016
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
Description: information about CPUs heterogeneity.
cpu_capacity: capacity of cpuX.
What: /sys/devices/system/cpu/vulnerabilities
/sys/devices/system/cpu/vulnerabilities/gather_data_sampling
/sys/devices/system/cpu/vulnerabilities/indirect_target_selection
/sys/devices/system/cpu/vulnerabilities/itlb_multihit
/sys/devices/system/cpu/vulnerabilities/l1tf
/sys/devices/system/cpu/vulnerabilities/mds
/sys/devices/system/cpu/vulnerabilities/meltdown
/sys/devices/system/cpu/vulnerabilities/mmio_stale_data
/sys/devices/system/cpu/vulnerabilities/old_microcode
/sys/devices/system/cpu/vulnerabilities/reg_file_data_sampling
/sys/devices/system/cpu/vulnerabilities/retbleed
/sys/devices/system/cpu/vulnerabilities/spec_store_bypass
/sys/devices/system/cpu/vulnerabilities/spectre_v1
/sys/devices/system/cpu/vulnerabilities/spectre_v2
/sys/devices/system/cpu/vulnerabilities/srbds
/sys/devices/system/cpu/vulnerabilities/tsx_async_abort
Date: January 2018
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
Description: Information about CPU vulnerabilities
The files are named after the code names of CPU
vulnerabilities. The output of those files reflects the
state of the CPUs in the system. Possible output values:
================ ==============================================
"Not affected" CPU is not affected by the vulnerability
"Vulnerable" CPU is affected and no mitigation in effect
"Mitigation: $M" CPU is affected and mitigation $M is in effect
================ ==============================================
See also: Documentation/admin-guide/hw-vuln/index.rst
What: /sys/devices/system/cpu/smt
/sys/devices/system/cpu/smt/active
/sys/devices/system/cpu/smt/control
Date: June 2018
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
Description: Control Symmetric Multi Threading (SMT)
active: Tells whether SMT is active (enabled and siblings online)
control: Read/write interface to control SMT. Possible
values:
================ =========================================
"on" SMT is enabled
"off" SMT is disabled
"<N>" SMT is enabled with N threads per core.
"forceoff" SMT is force disabled. Cannot be changed.
"notsupported" SMT is not supported by the CPU
"notimplemented" SMT runtime toggling is not
implemented for the architecture
================ =========================================
If control status is "forceoff" or "notsupported" writes
are rejected. Note that enabling SMT on PowerPC skips
offline cores.
What: /sys/devices/system/cpu/cpuX/power/energy_perf_bias
Date: March 2019
Contact: linux-pm@vger.kernel.org
Description: Intel Energy and Performance Bias Hint (EPB)
EPB for the given CPU in a sliding scale 0 - 15, where a value
of 0 corresponds to a hint preference for highest performance
and a value of 15 corresponds to the maximum energy savings.
In order to change the EPB value for the CPU, write either
a number in the 0 - 15 sliding scale above, or one of the
strings: "performance", "balance-performance", "normal",
"balance-power", "power" (that represent values reflected by
their meaning), to this attribute.
This attribute is present for all online CPUs supporting the
Intel EPB feature.
What: /sys/devices/system/cpu/umwait_control
/sys/devices/system/cpu/umwait_control/enable_c02
/sys/devices/system/cpu/umwait_control/max_time
Date: May 2019
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
Description: Umwait control
enable_c02: Read/write interface to control umwait C0.2 state
Read returns C0.2 state status:
0: C0.2 is disabled
1: C0.2 is enabled
Write 'y' or '1' or 'on' to enable C0.2 state.
Write 'n' or '0' or 'off' to disable C0.2 state.
The interface is case insensitive.
max_time: Read/write interface to control umwait maximum time
in TSC-quanta that the CPU can reside in either C0.1
or C0.2 state. The time is an unsigned 32-bit number.
Note that a value of zero means there is no limit.
Low order two bits must be zero.
What: /sys/devices/system/cpu/sev
/sys/devices/system/cpu/sev/vmpl
Date: May 2024
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
Description: Secure Encrypted Virtualization (SEV) information
This directory is only present when running as an SEV-SNP guest.
vmpl: Reports the Virtual Machine Privilege Level (VMPL) at which
the SEV-SNP guest is running.
What: /sys/devices/system/cpu/svm
Date: August 2019
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
Linux for PowerPC mailing list <linuxppc-dev@lists.ozlabs.org>
Description: Secure Virtual Machine
If 1, it means the system is using the Protected Execution
Facility in POWER9 and newer processors. i.e., it is a Secure
Virtual Machine.
What: /sys/devices/system/cpu/cpuX/purr
Date: Apr 2005
Contact: Linux for PowerPC mailing list <linuxppc-dev@lists.ozlabs.org>
Description: PURR ticks for this CPU since the system boot.
The Processor Utilization Resources Register (PURR) is
a 64-bit counter which provides an estimate of the
resources used by the CPU thread. The contents of this
register increases monotonically. This sysfs interface
exposes the number of PURR ticks for cpuX.
What: /sys/devices/system/cpu/cpuX/spurr
Date: Dec 2006
Contact: Linux for PowerPC mailing list <linuxppc-dev@lists.ozlabs.org>
Description: SPURR ticks for this CPU since the system boot.
The Scaled Processor Utilization Resources Register
(SPURR) is a 64-bit counter that provides a frequency
invariant estimate of the resources used by the CPU
thread. The contents of this register increases
monotonically. This sysfs interface exposes the number
of SPURR ticks for cpuX.
What: /sys/devices/system/cpu/cpuX/idle_purr
Date: Apr 2020
Contact: Linux for PowerPC mailing list <linuxppc-dev@lists.ozlabs.org>
Description: PURR ticks for cpuX when it was idle.
This sysfs interface exposes the number of PURR ticks
for cpuX when it was idle.
What: /sys/devices/system/cpu/cpuX/idle_spurr
Date: Apr 2020
Contact: Linux for PowerPC mailing list <linuxppc-dev@lists.ozlabs.org>
Description: SPURR ticks for cpuX when it was idle.
This sysfs interface exposes the number of SPURR ticks
for cpuX when it was idle.
What: /sys/devices/system/cpu/cpuX/mte_tcf_preferred
Date: July 2021
Contact: Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org>
Description: Preferred MTE tag checking mode
When a user program specifies more than one MTE tag checking
mode, this sysfs node is used to specify which mode should
be preferred when scheduling a task on that CPU. Possible
values:
================ ==============================================
"sync" Prefer synchronous mode
"asymm" Prefer asymmetric mode
"async" Prefer asynchronous mode
================ ==============================================
See also: Documentation/arch/arm64/memory-tagging-extension.rst
What: /sys/devices/system/cpu/nohz_full
Date: Apr 2015
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
Description:
(RO) the list of CPUs that are in nohz_full mode.
These CPUs are set by boot parameter "nohz_full=".
What: /sys/devices/system/cpu/isolated
Date: Apr 2015
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
Description:
(RO) the list of CPUs that are isolated and don't
participate in load balancing. These CPUs are set by
boot parameter "isolcpus=".
What: /sys/devices/system/cpu/crash_hotplug
Date: Aug 2023
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
Description:
(RO) indicates whether or not the kernel updates relevant kexec
segments on memory hot un/plug and/or on/offline events, avoiding the
need to reload kdump kernel.
What: /sys/devices/system/cpu/enabled
Date: Nov 2022
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
Description:
(RO) the list of CPUs that can be brought online.
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