8974eb5882
Gather Data Sampling (GDS) is a hardware vulnerability which allows
unprivileged speculative access to data which was previously stored in
vector registers.
Intel processors that support AVX2 and AVX512 have gather instructions
that fetch non-contiguous data elements from memory. On vulnerable
hardware, when a gather instruction is transiently executed and
encounters a fault, stale data from architectural or internal vector
registers may get transiently stored to the destination vector
register allowing an attacker to infer the stale data using typical
side channel techniques like cache timing attacks.
This mitigation is different from many earlier ones for two reasons.
First, it is enabled by default and a bit must be set to *DISABLE* it.
This is the opposite of normal mitigation polarity. This means GDS can
be mitigated simply by updating microcode and leaving the new control
bit alone.
Second, GDS has a "lock" bit. This lock bit is there because the
mitigation affects the hardware security features KeyLocker and SGX.
It needs to be enabled and *STAY* enabled for these features to be
mitigated against GDS.
The mitigation is enabled in the microcode by default. Disable it by
setting gather_data_sampling=off or by disabling all mitigations with
mitigations=off. The mitigation status can be checked by reading:
/sys/devices/system/cpu/vulnerabilities/gather_data_sampling
Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
26 KiB
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 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.
See Documentation/admin-guide/pm/cpuidle.rst and
Documentation/driver-api/pm/cpuidle.rst for more information.
What: /sys/devices/system/cpu/cpuX/cpuidle/state/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/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/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/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/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/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/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/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/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
attributes:
LEGACY used only on IA64 and is same as write_policy
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@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@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/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/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/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
"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.
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/svm Date: August 2019 Contact: Linux kernel mailing list linux-kernel@vger.kernel.org Linux for PowerPC mailing list linuxppc-dev@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@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@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@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@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=".