1 What: /sys/devices/system/cpu/
2 Date: pre-git history
3 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
4 Description:
5 A collection of both global and individual CPU attributes
6
7 Individual CPU attributes are contained in subdirectories
8 named by the kernel's logical CPU number, e.g.:
9
10 /sys/devices/system/cpu/cpuX/
11
12 What: /sys/devices/system/cpu/kernel_max
13 /sys/devices/system/cpu/offline
14 /sys/devices/system/cpu/online
15 /sys/devices/system/cpu/possible
16 /sys/devices/system/cpu/present
17 Date: December 2008
18 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
19 Description: CPU topology files that describe kernel limits related to
20 hotplug. Briefly:
21
22 kernel_max: the maximum cpu index allowed by the kernel
23 configuration.
24
25 offline: cpus that are not online because they have been
26 HOTPLUGGED off or exceed the limit of cpus allowed by the
27 kernel configuration (kernel_max above).
28
29 online: cpus that are online and being scheduled.
30
31 possible: cpus that have been allocated resources and can be
32 brought online if they are present.
33
34 present: cpus that have been identified as being present in
35 the system.
36
37 See Documentation/admin-guide/cputopology.rst for more information.
38
39
40 What: /sys/devices/system/cpu/probe
41 /sys/devices/system/cpu/release
42 Date: November 2009
43 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
44 Description: Dynamic addition and removal of CPU's. This is not hotplug
45 removal, this is meant complete removal/addition of the CPU
46 from the system.
47
48 probe: writes to this file will dynamically add a CPU to the
49 system. Information written to the file to add CPU's is
50 architecture specific.
51
52 release: writes to this file dynamically remove a CPU from
53 the system. Information written to the file to remove CPU's
54 is architecture specific.
55
56 What: /sys/devices/system/cpu/cpuX/node
57 Date: October 2009
58 Contact: Linux memory management mailing list <linux-mm@kvack.org>
59 Description: Discover NUMA node a CPU belongs to
60
61 When CONFIG_NUMA is enabled, a symbolic link that points
62 to the corresponding NUMA node directory.
63
64 For example, the following symlink is created for cpu42
65 in NUMA node 2:
66
67 /sys/devices/system/cpu/cpu42/node2 -> ../../node/node2
68
69
70 What: /sys/devices/system/cpu/cpuX/topology/core_siblings
71 /sys/devices/system/cpu/cpuX/topology/core_siblings_list
72 /sys/devices/system/cpu/cpuX/topology/physical_package_id
73 /sys/devices/system/cpu/cpuX/topology/thread_siblings
74 /sys/devices/system/cpu/cpuX/topology/thread_siblings_list
75 /sys/devices/system/cpu/cpuX/topology/ppin
76 Date: December 2008
77 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
78 Description: CPU topology files that describe a logical CPU's relationship
79 to other cores and threads in the same physical package.
80
81 One cpuX directory is created per logical CPU in the system,
82 e.g. /sys/devices/system/cpu/cpu42/.
83
84 Briefly, the files above are:
85
86 core_siblings: internal kernel map of cpuX's hardware threads
87 within the same physical_package_id.
88
89 core_siblings_list: human-readable list of the logical CPU
90 numbers within the same physical_package_id as cpuX.
91
92 physical_package_id: physical package id of cpuX. Typically
93 corresponds to a physical socket number, but the actual value
94 is architecture and platform dependent.
95
96 thread_siblings: internal kernel map of cpuX's hardware
97 threads within the same core as cpuX
98
99 thread_siblings_list: human-readable list of cpuX's hardware
100 threads within the same core as cpuX
101
102 ppin: human-readable Protected Processor Identification
103 Number of the socket the cpu# belongs to. There should be
104 one per physical_package_id. File is readable only to
105 admin.
106
107 See Documentation/admin-guide/cputopology.rst for more information.
108
109
110 What: /sys/devices/system/cpu/cpuidle/available_governors
111 /sys/devices/system/cpu/cpuidle/current_driver
112 /sys/devices/system/cpu/cpuidle/current_governor
113 /sys/devices/system/cpu/cpuidle/current_governer_ro
114 Date: September 2007
115 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
116 Description: Discover cpuidle policy and mechanism
117
118 Various CPUs today support multiple idle levels that are
119 differentiated by varying exit latencies and power
120 consumption during idle.
121
122 Idle policy (governor) is differentiated from idle mechanism
123 (driver).
124
125 available_governors: (RO) displays a space separated list of
126 available governors.
127
128 current_driver: (RO) displays current idle mechanism.
129
130 current_governor: (RW) displays current idle policy. Users can
131 switch the governor at runtime by writing to this file.
132
133 current_governor_ro: (RO) displays current idle policy.
134
135 See Documentation/admin-guide/pm/cpuidle.rst and
136 Documentation/driver-api/pm/cpuidle.rst for more information.
137
138
139 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/name
140 /sys/devices/system/cpu/cpuX/cpuidle/stateN/latency
141 /sys/devices/system/cpu/cpuX/cpuidle/stateN/power
142 /sys/devices/system/cpu/cpuX/cpuidle/stateN/time
143 /sys/devices/system/cpu/cpuX/cpuidle/stateN/usage
144 /sys/devices/system/cpu/cpuX/cpuidle/stateN/above
145 /sys/devices/system/cpu/cpuX/cpuidle/stateN/below
146 Date: September 2007
147 KernelVersion: v2.6.24
148 Contact: Linux power management list <linux-pm@vger.kernel.org>
149 Description:
150 The directory /sys/devices/system/cpu/cpuX/cpuidle contains per
151 logical CPU specific cpuidle information for each online cpu X.
152 The processor idle states which are available for use have the
153 following attributes:
154
155 ======== ==== =================================================
156 name: (RO) Name of the idle state (string).
157
158 latency: (RO) The latency to exit out of this idle state (in
159 microseconds).
160
161 power: (RO) The power consumed while in this idle state (in
162 milliwatts).
163
164 time: (RO) The total time spent in this idle state
165 (in microseconds).
166
167 usage: (RO) Number of times this state was entered (a count).
168
169 above: (RO) Number of times this state was entered, but the
170 observed CPU idle duration was too short for it
171 (a count).
172
173 below: (RO) Number of times this state was entered, but the
174 observed CPU idle duration was too long for it
175 (a count).
176 ======== ==== =================================================
177
178 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/desc
179 Date: February 2008
180 KernelVersion: v2.6.25
181 Contact: Linux power management list <linux-pm@vger.kernel.org>
182 Description:
183 (RO) A small description about the idle state (string).
184
185
186 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/disable
187 Date: March 2012
188 KernelVersion: v3.10
189 Contact: Linux power management list <linux-pm@vger.kernel.org>
190 Description:
191 (RW) Option to disable this idle state (bool). The behavior and
192 the effect of the disable variable depends on the implementation
193 of a particular governor. In the ladder governor, for example,
194 it is not coherent, i.e. if one is disabling a light state, then
195 all deeper states are disabled as well, but the disable variable
196 does not reflect it. Likewise, if one enables a deep state but a
197 lighter state still is disabled, then this has no effect.
198
199 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/default_status
200 Date: December 2019
201 KernelVersion: v5.6
202 Contact: Linux power management list <linux-pm@vger.kernel.org>
203 Description:
204 (RO) The default status of this state, "enabled" or "disabled".
205
206 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/residency
207 Date: March 2014
208 KernelVersion: v3.15
209 Contact: Linux power management list <linux-pm@vger.kernel.org>
210 Description:
211 (RO) Display the target residency i.e. the minimum amount of
212 time (in microseconds) this cpu should spend in this idle state
213 to make the transition worth the effort.
214
215 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/s2idle/
216 Date: March 2018
217 KernelVersion: v4.17
218 Contact: Linux power management list <linux-pm@vger.kernel.org>
219 Description:
220 Idle state usage statistics related to suspend-to-idle.
221
222 This attribute group is only present for states that can be
223 used in suspend-to-idle with suspended timekeeping.
224
225 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/s2idle/time
226 Date: March 2018
227 KernelVersion: v4.17
228 Contact: Linux power management list <linux-pm@vger.kernel.org>
229 Description:
230 Total time spent by the CPU in suspend-to-idle (with scheduler
231 tick suspended) after requesting this state.
232
233 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/s2idle/usage
234 Date: March 2018
235 KernelVersion: v4.17
236 Contact: Linux power management list <linux-pm@vger.kernel.org>
237 Description:
238 Total number of times this state has been requested by the CPU
239 while entering suspend-to-idle.
240
241 What: /sys/devices/system/cpu/cpuX/cpufreq/*
242 Date: pre-git history
243 Contact: linux-pm@vger.kernel.org
244 Description: Discover and change clock speed of CPUs
245
246 Clock scaling allows you to change the clock speed of the
247 CPUs on the fly. This is a nice method to save battery
248 power, because the lower the clock speed, the less power
249 the CPU consumes.
250
251 There are many knobs to tweak in this directory.
252
253 See files in Documentation/cpu-freq/ for more information.
254
255
256 What: /sys/devices/system/cpu/cpuX/cpufreq/freqdomain_cpus
257 Date: June 2013
258 Contact: linux-pm@vger.kernel.org
259 Description: Discover CPUs in the same CPU frequency coordination domain
260
261 freqdomain_cpus is the list of CPUs (online+offline) that share
262 the same clock/freq domain (possibly at the hardware level).
263 That information may be hidden from the cpufreq core and the
264 value of related_cpus may be different from freqdomain_cpus. This
265 attribute is useful for user space DVFS controllers to get better
266 power/performance results for platforms using acpi-cpufreq.
267
268 This file is only present if the acpi-cpufreq or the cppc-cpufreq
269 drivers are in use.
270
271
272 What: /sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1}
273 Date: August 2008
274 KernelVersion: 2.6.27
275 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
276 Description: Disable L3 cache indices
277
278 These files exist in every CPU's cache/index3 directory. Each
279 cache_disable_{0,1} file corresponds to one disable slot which
280 can be used to disable a cache index. Reading from these files
281 on a processor with this functionality will return the currently
282 disabled index for that node. There is one L3 structure per
283 node, or per internal node on MCM machines. Writing a valid
284 index to one of these files will cause the specified cache
285 index to be disabled.
286
287 All AMD processors with L3 caches provide this functionality.
288 For details, see BKDGs at
289 https://www.amd.com/en/support/tech-docs?keyword=bios+kernel
290
291
292 What: /sys/devices/system/cpu/cpufreq/boost
293 Date: August 2012
294 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
295 Description: Processor frequency boosting control
296
297 This switch controls the boost setting for the whole system.
298 Boosting allows the CPU and the firmware to run at a frequency
299 beyond its nominal limit.
300
301 More details can be found in
302 Documentation/admin-guide/pm/cpufreq.rst
303
304
305 What: /sys/devices/system/cpu/cpuX/crash_notes
306 /sys/devices/system/cpu/cpuX/crash_notes_size
307 Date: April 2013
308 Contact: kexec@lists.infradead.org
309 Description: address and size of the percpu note.
310
311 crash_notes: the physical address of the memory that holds the
312 note of cpuX.
313
314 crash_notes_size: size of the note of cpuX.
315
316
317 What: /sys/devices/system/cpu/intel_pstate/max_perf_pct
318 /sys/devices/system/cpu/intel_pstate/min_perf_pct
319 /sys/devices/system/cpu/intel_pstate/no_turbo
320 Date: February 2013
321 Contact: linux-pm@vger.kernel.org
322 Description: Parameters for the Intel P-state driver
323
324 Logic for selecting the current P-state in Intel
325 Sandybridge+ processors. The three knobs control
326 limits for the P-state that will be requested by the
327 driver.
328
329 max_perf_pct: limits the maximum P state that will be requested by
330 the driver stated as a percentage of the available performance.
331
332 min_perf_pct: limits the minimum P state that will be requested by
333 the driver stated as a percentage of the available performance.
334
335 no_turbo: limits the driver to selecting P states below the turbo
336 frequency range.
337
338 More details can be found in
339 Documentation/admin-guide/pm/intel_pstate.rst
340
341 What: /sys/devices/system/cpu/cpu*/cache/index*/<set_of_attributes_mentioned_below>
342 Date: July 2014(documented, existed before August 2008)
343 Contact: Sudeep Holla <sudeep.holla@arm.com>
344 Linux kernel mailing list <linux-kernel@vger.kernel.org>
345 Description: Parameters for the CPU cache attributes
346
347 allocation_policy:
348 - WriteAllocate:
349 allocate a memory location to a cache line
350 on a cache miss because of a write
351 - ReadAllocate:
352 allocate a memory location to a cache line
353 on a cache miss because of a read
354 - ReadWriteAllocate:
355 both writeallocate and readallocate
356
357 coherency_line_size:
358 the minimum amount of data in bytes that gets
359 transferred from memory to cache
360
361 level:
362 the cache hierarchy in the multi-level cache configuration
363
364 number_of_sets:
365 total number of sets in the cache, a set is a
366 collection of cache lines with the same cache index
367
368 physical_line_partition:
369 number of physical cache line per cache tag
370
371 shared_cpu_list:
372 the list of logical cpus sharing the cache
373
374 shared_cpu_map:
375 logical cpu mask containing the list of cpus sharing
376 the cache
377
378 size:
379 the total cache size in kB
380
381 type:
382 - Instruction: cache that only holds instructions
383 - Data: cache that only caches data
384 - Unified: cache that holds both data and instructions
385
386 ways_of_associativity:
387 degree of freedom in placing a particular block
388 of memory in the cache
389
390 write_policy:
391 - WriteThrough:
392 data is written to both the cache line
393 and to the block in the lower-level memory
394 - WriteBack:
395 data is written only to the cache line and
396 the modified cache line is written to main
397 memory only when it is replaced
398
399
400 What: /sys/devices/system/cpu/cpu*/cache/index*/id
401 Date: September 2016
402 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
403 Description: Cache id
404
405 The id provides a unique number for a specific instance of
406 a cache of a particular type. E.g. there may be a level
407 3 unified cache on each socket in a server and we may
408 assign them ids 0, 1, 2, ...
409
410 Note that id value can be non-contiguous. E.g. level 1
411 caches typically exist per core, but there may not be a
412 power of two cores on a socket, so these caches may be
413 numbered 0, 1, 2, 3, 4, 5, 8, 9, 10, ...
414
415 What: /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats
416 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/turbo_stat
417 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/sub_turbo_stat
418 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/unthrottle
419 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/powercap
420 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overtemp
421 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/supply_fault
422 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overcurrent
423 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/occ_reset
424 Date: March 2016
425 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
426 Linux for PowerPC mailing list <linuxppc-dev@lists.ozlabs.org>
427 Description: POWERNV CPUFreq driver's frequency throttle stats directory and
428 attributes
429
430 'cpuX/cpufreq/throttle_stats' directory contains the CPU frequency
431 throttle stat attributes for the chip. The throttle stats of a cpu
432 is common across all the cpus belonging to a chip. Below are the
433 throttle attributes exported in the 'throttle_stats' directory:
434
435 - turbo_stat : This file gives the total number of times the max
436 frequency is throttled to lower frequency in turbo (at and above
437 nominal frequency) range of frequencies.
438
439 - sub_turbo_stat : This file gives the total number of times the
440 max frequency is throttled to lower frequency in sub-turbo(below
441 nominal frequency) range of frequencies.
442
443 - unthrottle : This file gives the total number of times the max
444 frequency is unthrottled after being throttled.
445
446 - powercap : This file gives the total number of times the max
447 frequency is throttled due to 'Power Capping'.
448
449 - overtemp : This file gives the total number of times the max
450 frequency is throttled due to 'CPU Over Temperature'.
451
452 - supply_fault : This file gives the total number of times the
453 max frequency is throttled due to 'Power Supply Failure'.
454
455 - overcurrent : This file gives the total number of times the
456 max frequency is throttled due to 'Overcurrent'.
457
458 - occ_reset : This file gives the total number of times the max
459 frequency is throttled due to 'OCC Reset'.
460
461 The sysfs attributes representing different throttle reasons like
462 powercap, overtemp, supply_fault, overcurrent and occ_reset map to
463 the reasons provided by OCC firmware for throttling the frequency.
464
465 What: /sys/devices/system/cpu/cpufreq/policyX/throttle_stats
466 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/turbo_stat
467 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/sub_turbo_stat
468 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/unthrottle
469 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/powercap
470 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/overtemp
471 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/supply_fault
472 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/overcurrent
473 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/occ_reset
474 Date: March 2016
475 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
476 Linux for PowerPC mailing list <linuxppc-dev@lists.ozlabs.org>
477 Description: POWERNV CPUFreq driver's frequency throttle stats directory and
478 attributes
479
480 'policyX/throttle_stats' directory and all the attributes are same as
481 the /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats directory and
482 attributes which give the frequency throttle information of the chip.
483
484 What: /sys/devices/system/cpu/cpuX/regs/
485 /sys/devices/system/cpu/cpuX/regs/identification/
486 /sys/devices/system/cpu/cpuX/regs/identification/midr_el1
487 /sys/devices/system/cpu/cpuX/regs/identification/revidr_el1
488 /sys/devices/system/cpu/cpuX/regs/identification/smidr_el1
489 Date: June 2016
490 Contact: Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org>
491 Description: AArch64 CPU registers
492
493 'identification' directory exposes the CPU ID registers for
494 identifying model and revision of the CPU and SMCU.
495
496 What: /sys/devices/system/cpu/aarch32_el0
497 Date: May 2021
498 Contact: Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org>
499 Description: Identifies the subset of CPUs in the system that can execute
500 AArch32 (32-bit ARM) applications. If present, the same format as
501 /sys/devices/system/cpu/{offline,online,possible,present} is used.
502 If absent, then all or none of the CPUs can execute AArch32
503 applications and execve() will behave accordingly.
504
505 What: /sys/devices/system/cpu/cpuX/cpu_capacity
506 Date: December 2016
507 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
508 Description: information about CPUs heterogeneity.
509
510 cpu_capacity: capacity of cpuX.
511
512 What: /sys/devices/system/cpu/vulnerabilities
513 /sys/devices/system/cpu/vulnerabilities/gather_data_sampling
514 /sys/devices/system/cpu/vulnerabilities/itlb_multihit
515 /sys/devices/system/cpu/vulnerabilities/l1tf
516 /sys/devices/system/cpu/vulnerabilities/mds
517 /sys/devices/system/cpu/vulnerabilities/meltdown
518 /sys/devices/system/cpu/vulnerabilities/mmio_stale_data
519 /sys/devices/system/cpu/vulnerabilities/reg_file_data_sampling
520 /sys/devices/system/cpu/vulnerabilities/retbleed
521 /sys/devices/system/cpu/vulnerabilities/spec_store_bypass
522 /sys/devices/system/cpu/vulnerabilities/spectre_v1
523 /sys/devices/system/cpu/vulnerabilities/spectre_v2
524 /sys/devices/system/cpu/vulnerabilities/srbds
525 /sys/devices/system/cpu/vulnerabilities/tsx_async_abort
526 Date: January 2018
527 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
528 Description: Information about CPU vulnerabilities
529
530 The files are named after the code names of CPU
531 vulnerabilities. The output of those files reflects the
532 state of the CPUs in the system. Possible output values:
533
534 ================ ==============================================
535 "Not affected" CPU is not affected by the vulnerability
536 "Vulnerable" CPU is affected and no mitigation in effect
537 "Mitigation: $M" CPU is affected and mitigation $M is in effect
538 ================ ==============================================
539
540 See also: Documentation/admin-guide/hw-vuln/index.rst
541
542 What: /sys/devices/system/cpu/smt
543 /sys/devices/system/cpu/smt/active
544 /sys/devices/system/cpu/smt/control
545 Date: June 2018
546 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
547 Description: Control Symmetric Multi Threading (SMT)
548
549 active: Tells whether SMT is active (enabled and siblings online)
550
551 control: Read/write interface to control SMT. Possible
552 values:
553
554 ================ =========================================
555 "on" SMT is enabled
556 "off" SMT is disabled
557 "<N>" SMT is enabled with N threads per core.
558 "forceoff" SMT is force disabled. Cannot be changed.
559 "notsupported" SMT is not supported by the CPU
560 "notimplemented" SMT runtime toggling is not
561 implemented for the architecture
562 ================ =========================================
563
564 If control status is "forceoff" or "notsupported" writes
565 are rejected. Note that enabling SMT on PowerPC skips
566 offline cores.
567
568 What: /sys/devices/system/cpu/cpuX/power/energy_perf_bias
569 Date: March 2019
570 Contact: linux-pm@vger.kernel.org
571 Description: Intel Energy and Performance Bias Hint (EPB)
572
573 EPB for the given CPU in a sliding scale 0 - 15, where a value
574 of 0 corresponds to a hint preference for highest performance
575 and a value of 15 corresponds to the maximum energy savings.
576
577 In order to change the EPB value for the CPU, write either
578 a number in the 0 - 15 sliding scale above, or one of the
579 strings: "performance", "balance-performance", "normal",
580 "balance-power", "power" (that represent values reflected by
581 their meaning), to this attribute.
582
583 This attribute is present for all online CPUs supporting the
584 Intel EPB feature.
585
586 What: /sys/devices/system/cpu/umwait_control
587 /sys/devices/system/cpu/umwait_control/enable_c02
588 /sys/devices/system/cpu/umwait_control/max_time
589 Date: May 2019
590 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
591 Description: Umwait control
592
593 enable_c02: Read/write interface to control umwait C0.2 state
594 Read returns C0.2 state status:
595 0: C0.2 is disabled
596 1: C0.2 is enabled
597
598 Write 'y' or '1' or 'on' to enable C0.2 state.
599 Write 'n' or '0' or 'off' to disable C0.2 state.
600
601 The interface is case insensitive.
602
603 max_time: Read/write interface to control umwait maximum time
604 in TSC-quanta that the CPU can reside in either C0.1
605 or C0.2 state. The time is an unsigned 32-bit number.
606 Note that a value of zero means there is no limit.
607 Low order two bits must be zero.
608
609 What: /sys/devices/system/cpu/sev
610 /sys/devices/system/cpu/sev/vmpl
611 Date: May 2024
612 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
613 Description: Secure Encrypted Virtualization (SEV) information
614
615 This directory is only present when running as an SEV-SNP guest.
616
617 vmpl: Reports the Virtual Machine Privilege Level (VMPL) at which
618 the SEV-SNP guest is running.
619
620
621 What: /sys/devices/system/cpu/svm
622 Date: August 2019
623 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
624 Linux for PowerPC mailing list <linuxppc-dev@lists.ozlabs.org>
625 Description: Secure Virtual Machine
626
627 If 1, it means the system is using the Protected Execution
628 Facility in POWER9 and newer processors. i.e., it is a Secure
629 Virtual Machine.
630
631 What: /sys/devices/system/cpu/cpuX/purr
632 Date: Apr 2005
633 Contact: Linux for PowerPC mailing list <linuxppc-dev@lists.ozlabs.org>
634 Description: PURR ticks for this CPU since the system boot.
635
636 The Processor Utilization Resources Register (PURR) is
637 a 64-bit counter which provides an estimate of the
638 resources used by the CPU thread. The contents of this
639 register increases monotonically. This sysfs interface
640 exposes the number of PURR ticks for cpuX.
641
642 What: /sys/devices/system/cpu/cpuX/spurr
643 Date: Dec 2006
644 Contact: Linux for PowerPC mailing list <linuxppc-dev@lists.ozlabs.org>
645 Description: SPURR ticks for this CPU since the system boot.
646
647 The Scaled Processor Utilization Resources Register
648 (SPURR) is a 64-bit counter that provides a frequency
649 invariant estimate of the resources used by the CPU
650 thread. The contents of this register increases
651 monotonically. This sysfs interface exposes the number
652 of SPURR ticks for cpuX.
653
654 What: /sys/devices/system/cpu/cpuX/idle_purr
655 Date: Apr 2020
656 Contact: Linux for PowerPC mailing list <linuxppc-dev@lists.ozlabs.org>
657 Description: PURR ticks for cpuX when it was idle.
658
659 This sysfs interface exposes the number of PURR ticks
660 for cpuX when it was idle.
661
662 What: /sys/devices/system/cpu/cpuX/idle_spurr
663 Date: Apr 2020
664 Contact: Linux for PowerPC mailing list <linuxppc-dev@lists.ozlabs.org>
665 Description: SPURR ticks for cpuX when it was idle.
666
667 This sysfs interface exposes the number of SPURR ticks
668 for cpuX when it was idle.
669
670 What: /sys/devices/system/cpu/cpuX/mte_tcf_preferred
671 Date: July 2021
672 Contact: Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org>
673 Description: Preferred MTE tag checking mode
674
675 When a user program specifies more than one MTE tag checking
676 mode, this sysfs node is used to specify which mode should
677 be preferred when scheduling a task on that CPU. Possible
678 values:
679
680 ================ ==============================================
681 "sync" Prefer synchronous mode
682 "asymm" Prefer asymmetric mode
683 "async" Prefer asynchronous mode
684 ================ ==============================================
685
686 See also: Documentation/arch/arm64/memory-tagging-extension.rst
687
688 What: /sys/devices/system/cpu/nohz_full
689 Date: Apr 2015
690 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
691 Description:
692 (RO) the list of CPUs that are in nohz_full mode.
693 These CPUs are set by boot parameter "nohz_full=".
694
695 What: /sys/devices/system/cpu/isolated
696 Date: Apr 2015
697 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
698 Description:
699 (RO) the list of CPUs that are isolated and don't
700 participate in load balancing. These CPUs are set by
701 boot parameter "isolcpus=".
702
703 What: /sys/devices/system/cpu/crash_hotplug
704 Date: Aug 2023
705 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
706 Description:
707 (RO) indicates whether or not the kernel updates relevant kexec
708 segments on memory hot un/plug and/or on/offline events, avoiding the
709 need to reload kdump kernel.
710
711 What: /sys/devices/system/cpu/enabled
712 Date: Nov 2022
713 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
714 Description:
715 (RO) the list of CPUs that can be brought online.
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