1What:		/sys/devices/system/cpu/
2Date:		pre-git history
3Contact:	Linux kernel mailing list <linux-kernel@vger.kernel.org>
4Description:
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
12What:		/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
17Date:		December 2008
18Contact:	Linux kernel mailing list <linux-kernel@vger.kernel.org>
19Description:	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
40What:		/sys/devices/system/cpu/probe
41		/sys/devices/system/cpu/release
42Date:		November 2009
43Contact:	Linux kernel mailing list <linux-kernel@vger.kernel.org>
44Description:	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
56What:		/sys/devices/system/cpu/cpuX/node
57Date:		October 2009
58Contact:	Linux memory management mailing list <linux-mm@kvack.org>
59Description:	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
70What:		/sys/devices/system/cpu/cpuX/topology/core_id
71		/sys/devices/system/cpu/cpuX/topology/core_siblings
72		/sys/devices/system/cpu/cpuX/topology/core_siblings_list
73		/sys/devices/system/cpu/cpuX/topology/physical_package_id
74		/sys/devices/system/cpu/cpuX/topology/thread_siblings
75		/sys/devices/system/cpu/cpuX/topology/thread_siblings_list
76		/sys/devices/system/cpu/cpuX/topology/ppin
77Date:		December 2008
78Contact:	Linux kernel mailing list <linux-kernel@vger.kernel.org>
79Description:	CPU topology files that describe a logical CPU's relationship
80		to other cores and threads in the same physical package.
81
82		One cpuX directory is created per logical CPU in the system,
83		e.g. /sys/devices/system/cpu/cpu42/.
84
85		Briefly, the files above are:
86
87		core_id: the CPU core ID of cpuX. Typically it is the
88		hardware platform's identifier (rather than the kernel's).
89		The actual value is architecture and platform dependent.
90
91		core_siblings: internal kernel map of cpuX's hardware threads
92		within the same physical_package_id.
93
94		core_siblings_list: human-readable list of the logical CPU
95		numbers within the same physical_package_id as cpuX.
96
97		physical_package_id: physical package id of cpuX. Typically
98		corresponds to a physical socket number, but the actual value
99		is architecture and platform dependent.
100
101		thread_siblings: internal kernel map of cpuX's hardware
102		threads within the same core as cpuX
103
104		thread_siblings_list: human-readable list of cpuX's hardware
105		threads within the same core as cpuX
106
107		ppin: human-readable Protected Processor Identification
108		Number of the socket the cpu# belongs to. There should be
109		one per physical_package_id. File is readable only to
110		admin.
111
112		See Documentation/admin-guide/cputopology.rst for more information.
113
114
115What:		/sys/devices/system/cpu/cpuidle/available_governors
116		/sys/devices/system/cpu/cpuidle/current_driver
117		/sys/devices/system/cpu/cpuidle/current_governor
118		/sys/devices/system/cpu/cpuidle/current_governer_ro
119Date:		September 2007
120Contact:	Linux kernel mailing list <linux-kernel@vger.kernel.org>
121Description:	Discover cpuidle policy and mechanism
122
123		Various CPUs today support multiple idle levels that are
124		differentiated by varying exit latencies and power
125		consumption during idle.
126
127		Idle policy (governor) is differentiated from idle mechanism
128		(driver).
129
130		available_governors: (RO) displays a space separated list of
131		available governors.
132
133		current_driver: (RO) displays current idle mechanism.
134
135		current_governor: (RW) displays current idle policy. Users can
136		switch the governor at runtime by writing to this file.
137
138		current_governor_ro: (RO) displays current idle policy.
139
140		See Documentation/admin-guide/pm/cpuidle.rst and
141		Documentation/driver-api/pm/cpuidle.rst for more information.
142
143
144What:		/sys/devices/system/cpu/cpuX/cpuidle/state<N>/name
145		/sys/devices/system/cpu/cpuX/cpuidle/stateN/latency
146		/sys/devices/system/cpu/cpuX/cpuidle/stateN/power
147		/sys/devices/system/cpu/cpuX/cpuidle/stateN/time
148		/sys/devices/system/cpu/cpuX/cpuidle/stateN/usage
149		/sys/devices/system/cpu/cpuX/cpuidle/stateN/above
150		/sys/devices/system/cpu/cpuX/cpuidle/stateN/below
151Date:		September 2007
152KernelVersion:	v2.6.24
153Contact:	Linux power management list <linux-pm@vger.kernel.org>
154Description:
155		The directory /sys/devices/system/cpu/cpuX/cpuidle contains per
156		logical CPU specific cpuidle information for each online cpu X.
157		The processor idle states which are available for use have the
158		following attributes:
159
160		======== ==== =================================================
161		name:	 (RO) Name of the idle state (string).
162
163		latency: (RO) The latency to exit out of this idle state (in
164			      microseconds).
165
166		power:   (RO) The power consumed while in this idle state (in
167			      milliwatts).
168
169		time:    (RO) The total time spent in this idle state
170			      (in microseconds).
171
172		usage:	 (RO) Number of times this state was entered (a count).
173
174		above:	 (RO) Number of times this state was entered, but the
175			      observed CPU idle duration was too short for it
176			      (a count).
177
178		below:	 (RO) Number of times this state was entered, but the
179			      observed CPU idle duration was too long for it
180			      (a count).
181		======== ==== =================================================
182
183What:		/sys/devices/system/cpu/cpuX/cpuidle/state<N>/desc
184Date:		February 2008
185KernelVersion:	v2.6.25
186Contact:	Linux power management list <linux-pm@vger.kernel.org>
187Description:
188		(RO) A small description about the idle state (string).
189
190
191What:		/sys/devices/system/cpu/cpuX/cpuidle/state<N>/disable
192Date:		March 2012
193KernelVersion:	v3.10
194Contact:	Linux power management list <linux-pm@vger.kernel.org>
195Description:
196		(RW) Option to disable this idle state (bool). The behavior and
197		the effect of the disable variable depends on the implementation
198		of a particular governor. In the ladder governor, for example,
199		it is not coherent, i.e. if one is disabling a light state, then
200		all deeper states are disabled as well, but the disable variable
201		does not reflect it. Likewise, if one enables a deep state but a
202		lighter state still is disabled, then this has no effect.
203
204What:		/sys/devices/system/cpu/cpuX/cpuidle/state<N>/default_status
205Date:		December 2019
206KernelVersion:	v5.6
207Contact:	Linux power management list <linux-pm@vger.kernel.org>
208Description:
209		(RO) The default status of this state, "enabled" or "disabled".
210
211What:		/sys/devices/system/cpu/cpuX/cpuidle/state<N>/residency
212Date:		March 2014
213KernelVersion:	v3.15
214Contact:	Linux power management list <linux-pm@vger.kernel.org>
215Description:
216		(RO) Display the target residency i.e. the minimum amount of
217		time (in microseconds) this cpu should spend in this idle state
218		to make the transition worth the effort.
219
220What:		/sys/devices/system/cpu/cpuX/cpuidle/state<N>/s2idle/
221Date:		March 2018
222KernelVersion:	v4.17
223Contact:	Linux power management list <linux-pm@vger.kernel.org>
224Description:
225		Idle state usage statistics related to suspend-to-idle.
226
227		This attribute group is only present for states that can be
228		used in suspend-to-idle with suspended timekeeping.
229
230What:		/sys/devices/system/cpu/cpuX/cpuidle/state<N>/s2idle/time
231Date:		March 2018
232KernelVersion:	v4.17
233Contact:	Linux power management list <linux-pm@vger.kernel.org>
234Description:
235		Total time spent by the CPU in suspend-to-idle (with scheduler
236		tick suspended) after requesting this state.
237
238What:		/sys/devices/system/cpu/cpuX/cpuidle/state<N>/s2idle/usage
239Date:		March 2018
240KernelVersion:	v4.17
241Contact:	Linux power management list <linux-pm@vger.kernel.org>
242Description:
243		Total number of times this state has been requested by the CPU
244		while entering suspend-to-idle.
245
246What:		/sys/devices/system/cpu/cpuX/cpufreq/*
247Date:		pre-git history
248Contact:	linux-pm@vger.kernel.org
249Description:	Discover and change clock speed of CPUs
250
251		Clock scaling allows you to change the clock speed of the
252		CPUs on the fly. This is a nice method to save battery
253		power, because the lower the clock speed, the less power
254		the CPU consumes.
255
256		There are many knobs to tweak in this directory.
257
258		See files in Documentation/cpu-freq/ for more information.
259
260
261What:		/sys/devices/system/cpu/cpuX/cpufreq/freqdomain_cpus
262Date:		June 2013
263Contact:	linux-pm@vger.kernel.org
264Description:	Discover CPUs in the same CPU frequency coordination domain
265
266		freqdomain_cpus is the list of CPUs (online+offline) that share
267		the same clock/freq domain (possibly at the hardware level).
268		That information may be hidden from the cpufreq core and the
269		value of related_cpus may be different from freqdomain_cpus. This
270		attribute is useful for user space DVFS controllers to get better
271		power/performance results for platforms using acpi-cpufreq.
272
273		This file is only present if the acpi-cpufreq or the cppc-cpufreq
274		drivers are in use.
275
276
277What:		/sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1}
278Date:		August 2008
279KernelVersion:	2.6.27
280Contact:	Linux kernel mailing list <linux-kernel@vger.kernel.org>
281Description:	Disable L3 cache indices
282
283		These files exist in every CPU's cache/index3 directory. Each
284		cache_disable_{0,1} file corresponds to one disable slot which
285		can be used to disable a cache index. Reading from these files
286		on a processor with this functionality will return the currently
287		disabled index for that node. There is one L3 structure per
288		node, or per internal node on MCM machines. Writing a valid
289		index to one of these files will cause the specified cache
290		index to be disabled.
291
292		All AMD processors with L3 caches provide this functionality.
293		For details, see BKDGs at
294                https://www.amd.com/en/support/tech-docs?keyword=bios+kernel
295
296
297What:		/sys/devices/system/cpu/cpufreq/boost
298Date:		August 2012
299Contact:	Linux kernel mailing list <linux-kernel@vger.kernel.org>
300Description:	Processor frequency boosting control
301
302		This switch controls the boost setting for the whole system.
303		Boosting allows the CPU and the firmware to run at a frequency
304		beyond it's nominal limit.
305
306		More details can be found in
307		Documentation/admin-guide/pm/cpufreq.rst
308
309
310What:		/sys/devices/system/cpu/cpuX/crash_notes
311		/sys/devices/system/cpu/cpuX/crash_notes_size
312Date:		April 2013
313Contact:	kexec@lists.infradead.org
314Description:	address and size of the percpu note.
315
316		crash_notes: the physical address of the memory that holds the
317		note of cpuX.
318
319		crash_notes_size: size of the note of cpuX.
320
321
322What:		/sys/devices/system/cpu/intel_pstate/max_perf_pct
323		/sys/devices/system/cpu/intel_pstate/min_perf_pct
324		/sys/devices/system/cpu/intel_pstate/no_turbo
325Date:		February 2013
326Contact:	linux-pm@vger.kernel.org
327Description:	Parameters for the Intel P-state driver
328
329		Logic for selecting the current P-state in Intel
330		Sandybridge+ processors. The three knobs control
331		limits for the P-state that will be requested by the
332		driver.
333
334		max_perf_pct: limits the maximum P state that will be requested by
335		the driver stated as a percentage of the available performance.
336
337		min_perf_pct: limits the minimum P state that will be requested by
338		the driver stated as a percentage of the available performance.
339
340		no_turbo: limits the driver to selecting P states below the turbo
341		frequency range.
342
343		More details can be found in
344		Documentation/admin-guide/pm/intel_pstate.rst
345
346What:		/sys/devices/system/cpu/cpu*/cache/index*/<set_of_attributes_mentioned_below>
347Date:		July 2014(documented, existed before August 2008)
348Contact:	Sudeep Holla <sudeep.holla@arm.com>
349		Linux kernel mailing list <linux-kernel@vger.kernel.org>
350Description:	Parameters for the CPU cache attributes
351
352		allocation_policy:
353			- WriteAllocate:
354					allocate a memory location to a cache line
355					on a cache miss because of a write
356			- ReadAllocate:
357					allocate a memory location to a cache line
358					on a cache miss because of a read
359			- ReadWriteAllocate:
360					both writeallocate and readallocate
361
362		attributes:
363			    LEGACY used only on IA64 and is same as write_policy
364
365		coherency_line_size:
366				     the minimum amount of data in bytes that gets
367				     transferred from memory to cache
368
369		level:
370			the cache hierarchy in the multi-level cache configuration
371
372		number_of_sets:
373				total number of sets in the cache, a set is a
374				collection of cache lines with the same cache index
375
376		physical_line_partition:
377				number of physical cache line per cache tag
378
379		shared_cpu_list:
380				the list of logical cpus sharing the cache
381
382		shared_cpu_map:
383				logical cpu mask containing the list of cpus sharing
384				the cache
385
386		size:
387			the total cache size in kB
388
389		type:
390			- Instruction: cache that only holds instructions
391			- Data: cache that only caches data
392			- Unified: cache that holds both data and instructions
393
394		ways_of_associativity:
395			degree of freedom in placing a particular block
396			of memory in the cache
397
398		write_policy:
399			- WriteThrough:
400					data is written to both the cache line
401					and to the block in the lower-level memory
402			- WriteBack:
403				     data is written only to the cache line and
404				     the modified cache line is written to main
405				     memory only when it is replaced
406
407
408What:		/sys/devices/system/cpu/cpu*/cache/index*/id
409Date:		September 2016
410Contact:	Linux kernel mailing list <linux-kernel@vger.kernel.org>
411Description:	Cache id
412
413		The id provides a unique number for a specific instance of
414		a cache of a particular type. E.g. there may be a level
415		3 unified cache on each socket in a server and we may
416		assign them ids 0, 1, 2, ...
417
418		Note that id value can be non-contiguous. E.g. level 1
419		caches typically exist per core, but there may not be a
420		power of two cores on a socket, so these caches may be
421		numbered 0, 1, 2, 3, 4, 5, 8, 9, 10, ...
422
423What:		/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats
424		/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/turbo_stat
425		/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/sub_turbo_stat
426		/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/unthrottle
427		/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/powercap
428		/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overtemp
429		/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/supply_fault
430		/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overcurrent
431		/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/occ_reset
432Date:		March 2016
433Contact:	Linux kernel mailing list <linux-kernel@vger.kernel.org>
434		Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
435Description:	POWERNV CPUFreq driver's frequency throttle stats directory and
436		attributes
437
438		'cpuX/cpufreq/throttle_stats' directory contains the CPU frequency
439		throttle stat attributes for the chip. The throttle stats of a cpu
440		is common across all the cpus belonging to a chip. Below are the
441		throttle attributes exported in the 'throttle_stats' directory:
442
443		- turbo_stat : This file gives the total number of times the max
444		  frequency is throttled to lower frequency in turbo (at and above
445		  nominal frequency) range of frequencies.
446
447		- sub_turbo_stat : This file gives the total number of times the
448		  max frequency is throttled to lower frequency in sub-turbo(below
449		  nominal frequency) range of frequencies.
450
451		- unthrottle : This file gives the total number of times the max
452		  frequency is unthrottled after being throttled.
453
454		- powercap : This file gives the total number of times the max
455		  frequency is throttled due to 'Power Capping'.
456
457		- overtemp : This file gives the total number of times the max
458		  frequency is throttled due to 'CPU Over Temperature'.
459
460		- supply_fault : This file gives the total number of times the
461		  max frequency is throttled due to 'Power Supply Failure'.
462
463		- overcurrent : This file gives the total number of times the
464		  max frequency is throttled due to 'Overcurrent'.
465
466		- occ_reset : This file gives the total number of times the max
467		  frequency is throttled due to 'OCC Reset'.
468
469		The sysfs attributes representing different throttle reasons like
470		powercap, overtemp, supply_fault, overcurrent and occ_reset map to
471		the reasons provided by OCC firmware for throttling the frequency.
472
473What:		/sys/devices/system/cpu/cpufreq/policyX/throttle_stats
474		/sys/devices/system/cpu/cpufreq/policyX/throttle_stats/turbo_stat
475		/sys/devices/system/cpu/cpufreq/policyX/throttle_stats/sub_turbo_stat
476		/sys/devices/system/cpu/cpufreq/policyX/throttle_stats/unthrottle
477		/sys/devices/system/cpu/cpufreq/policyX/throttle_stats/powercap
478		/sys/devices/system/cpu/cpufreq/policyX/throttle_stats/overtemp
479		/sys/devices/system/cpu/cpufreq/policyX/throttle_stats/supply_fault
480		/sys/devices/system/cpu/cpufreq/policyX/throttle_stats/overcurrent
481		/sys/devices/system/cpu/cpufreq/policyX/throttle_stats/occ_reset
482Date:		March 2016
483Contact:	Linux kernel mailing list <linux-kernel@vger.kernel.org>
484		Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
485Description:	POWERNV CPUFreq driver's frequency throttle stats directory and
486		attributes
487
488		'policyX/throttle_stats' directory and all the attributes are same as
489		the /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats directory and
490		attributes which give the frequency throttle information of the chip.
491
492What:		/sys/devices/system/cpu/cpuX/regs/
493		/sys/devices/system/cpu/cpuX/regs/identification/
494		/sys/devices/system/cpu/cpuX/regs/identification/midr_el1
495		/sys/devices/system/cpu/cpuX/regs/identification/revidr_el1
496Date:		June 2016
497Contact:	Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org>
498Description:	AArch64 CPU registers
499
500		'identification' directory exposes the CPU ID registers for
501		identifying model and revision of the CPU.
502
503What:		/sys/devices/system/cpu/aarch32_el0
504Date:		May 2021
505Contact:	Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org>
506Description:	Identifies the subset of CPUs in the system that can execute
507		AArch32 (32-bit ARM) applications. If present, the same format as
508		/sys/devices/system/cpu/{offline,online,possible,present} is used.
509		If absent, then all or none of the CPUs can execute AArch32
510		applications and execve() will behave accordingly.
511
512What:		/sys/devices/system/cpu/cpuX/cpu_capacity
513Date:		December 2016
514Contact:	Linux kernel mailing list <linux-kernel@vger.kernel.org>
515Description:	information about CPUs heterogeneity.
516
517		cpu_capacity: capacity of cpuX.
518
519What:		/sys/devices/system/cpu/vulnerabilities
520		/sys/devices/system/cpu/vulnerabilities/meltdown
521		/sys/devices/system/cpu/vulnerabilities/spectre_v1
522		/sys/devices/system/cpu/vulnerabilities/spectre_v2
523		/sys/devices/system/cpu/vulnerabilities/spec_store_bypass
524		/sys/devices/system/cpu/vulnerabilities/l1tf
525		/sys/devices/system/cpu/vulnerabilities/mds
526		/sys/devices/system/cpu/vulnerabilities/srbds
527		/sys/devices/system/cpu/vulnerabilities/tsx_async_abort
528		/sys/devices/system/cpu/vulnerabilities/itlb_multihit
529		/sys/devices/system/cpu/vulnerabilities/mmio_stale_data
530Date:		January 2018
531Contact:	Linux kernel mailing list <linux-kernel@vger.kernel.org>
532Description:	Information about CPU vulnerabilities
533
534		The files are named after the code names of CPU
535		vulnerabilities. The output of those files reflects the
536		state of the CPUs in the system. Possible output values:
537
538		================  ==============================================
539		"Not affected"	  CPU is not affected by the vulnerability
540		"Vulnerable"	  CPU is affected and no mitigation in effect
541		"Mitigation: $M"  CPU is affected and mitigation $M is in effect
542		================  ==============================================
543
544		See also: Documentation/admin-guide/hw-vuln/index.rst
545
546What:		/sys/devices/system/cpu/smt
547		/sys/devices/system/cpu/smt/active
548		/sys/devices/system/cpu/smt/control
549Date:		June 2018
550Contact:	Linux kernel mailing list <linux-kernel@vger.kernel.org>
551Description:	Control Symmetric Multi Threading (SMT)
552
553		active:  Tells whether SMT is active (enabled and siblings online)
554
555		control: Read/write interface to control SMT. Possible
556			 values:
557
558			 ================ =========================================
559			 "on"		  SMT is enabled
560			 "off"		  SMT is disabled
561			 "forceoff"	  SMT is force disabled. Cannot be changed.
562			 "notsupported"   SMT is not supported by the CPU
563			 "notimplemented" SMT runtime toggling is not
564					  implemented for the architecture
565			 ================ =========================================
566
567			 If control status is "forceoff" or "notsupported" writes
568			 are rejected.
569
570What:		/sys/devices/system/cpu/cpuX/power/energy_perf_bias
571Date:		March 2019
572Contact:	linux-pm@vger.kernel.org
573Description:	Intel Energy and Performance Bias Hint (EPB)
574
575		EPB for the given CPU in a sliding scale 0 - 15, where a value
576		of 0 corresponds to a hint preference for highest performance
577		and a value of 15 corresponds to the maximum energy savings.
578
579		In order to change the EPB value for the CPU, write either
580		a number in the 0 - 15 sliding scale above, or one of the
581		strings: "performance", "balance-performance", "normal",
582		"balance-power", "power" (that represent values reflected by
583		their meaning), to this attribute.
584
585		This attribute is present for all online CPUs supporting the
586		Intel EPB feature.
587
588What:		/sys/devices/system/cpu/umwait_control
589		/sys/devices/system/cpu/umwait_control/enable_c02
590		/sys/devices/system/cpu/umwait_control/max_time
591Date:		May 2019
592Contact:	Linux kernel mailing list <linux-kernel@vger.kernel.org>
593Description:	Umwait control
594
595		enable_c02: Read/write interface to control umwait C0.2 state
596			Read returns C0.2 state status:
597				0: C0.2 is disabled
598				1: C0.2 is enabled
599
600			Write 'y' or '1'  or 'on' to enable C0.2 state.
601			Write 'n' or '0'  or 'off' to disable C0.2 state.
602
603			The interface is case insensitive.
604
605		max_time: Read/write interface to control umwait maximum time
606			  in TSC-quanta that the CPU can reside in either C0.1
607			  or C0.2 state. The time is an unsigned 32-bit number.
608			  Note that a value of zero means there is no limit.
609			  Low order two bits must be zero.
610
611What:		/sys/devices/system/cpu/svm
612Date:		August 2019
613Contact:	Linux kernel mailing list <linux-kernel@vger.kernel.org>
614		Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
615Description:	Secure Virtual Machine
616
617		If 1, it means the system is using the Protected Execution
618		Facility in POWER9 and newer processors. i.e., it is a Secure
619		Virtual Machine.
620
621What:		/sys/devices/system/cpu/cpuX/purr
622Date:		Apr 2005
623Contact:	Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
624Description:	PURR ticks for this CPU since the system boot.
625
626		The Processor Utilization Resources Register (PURR) is
627		a 64-bit counter which provides an estimate of the
628		resources used by the CPU thread. The contents of this
629		register increases monotonically. This sysfs interface
630		exposes the number of PURR ticks for cpuX.
631
632What: 		/sys/devices/system/cpu/cpuX/spurr
633Date:		Dec 2006
634Contact:	Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
635Description:	SPURR ticks for this CPU since the system boot.
636
637		The Scaled Processor Utilization Resources Register
638		(SPURR) is a 64-bit counter that provides a frequency
639		invariant estimate of the resources used by the CPU
640		thread. The contents of this register increases
641		monotonically. This sysfs interface exposes the number
642		of SPURR ticks for cpuX.
643
644What: 		/sys/devices/system/cpu/cpuX/idle_purr
645Date:		Apr 2020
646Contact:	Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
647Description:	PURR ticks for cpuX when it was idle.
648
649		This sysfs interface exposes the number of PURR ticks
650		for cpuX when it was idle.
651
652What: 		/sys/devices/system/cpu/cpuX/idle_spurr
653Date:		Apr 2020
654Contact:	Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
655Description:	SPURR ticks for cpuX when it was idle.
656
657		This sysfs interface exposes the number of SPURR ticks
658		for cpuX when it was idle.
659
660What: 		/sys/devices/system/cpu/cpuX/mte_tcf_preferred
661Date:		July 2021
662Contact:	Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org>
663Description:	Preferred MTE tag checking mode
664
665		When a user program specifies more than one MTE tag checking
666		mode, this sysfs node is used to specify which mode should
667		be preferred when scheduling a task on that CPU. Possible
668		values:
669
670		================  ==============================================
671		"sync"	  	  Prefer synchronous mode
672		"asymm"	  	  Prefer asymmetric mode
673		"async"	  	  Prefer asynchronous mode
674		================  ==============================================
675
676		See also: Documentation/arm64/memory-tagging-extension.rst
677
678What:		/sys/devices/system/cpu/nohz_full
679Date:		Apr 2015
680Contact:	Linux kernel mailing list <linux-kernel@vger.kernel.org>
681Description:
682		(RO) the list of CPUs that are in nohz_full mode.
683		These CPUs are set by boot parameter "nohz_full=".
684
685What:		/sys/devices/system/cpu/isolated
686Date:		Apr 2015
687Contact:	Linux kernel mailing list <linux-kernel@vger.kernel.org>
688Description:
689		(RO) the list of CPUs that are isolated and don't
690		participate in load balancing. These CPUs are set by
691		boot parameter "isolcpus=".
692