Merge tag 'gfs2-v6.3-fix' of git://git.kernel.org/pub/scm/linux/kernel/git/gfs2/linux...
[platform/kernel/linux-starfive.git] / kernel / cpu.c
1 /* CPU control.
2  * (C) 2001, 2002, 2003, 2004 Rusty Russell
3  *
4  * This code is licenced under the GPL.
5  */
6 #include <linux/sched/mm.h>
7 #include <linux/proc_fs.h>
8 #include <linux/smp.h>
9 #include <linux/init.h>
10 #include <linux/notifier.h>
11 #include <linux/sched/signal.h>
12 #include <linux/sched/hotplug.h>
13 #include <linux/sched/isolation.h>
14 #include <linux/sched/task.h>
15 #include <linux/sched/smt.h>
16 #include <linux/unistd.h>
17 #include <linux/cpu.h>
18 #include <linux/oom.h>
19 #include <linux/rcupdate.h>
20 #include <linux/export.h>
21 #include <linux/bug.h>
22 #include <linux/kthread.h>
23 #include <linux/stop_machine.h>
24 #include <linux/mutex.h>
25 #include <linux/gfp.h>
26 #include <linux/suspend.h>
27 #include <linux/lockdep.h>
28 #include <linux/tick.h>
29 #include <linux/irq.h>
30 #include <linux/nmi.h>
31 #include <linux/smpboot.h>
32 #include <linux/relay.h>
33 #include <linux/slab.h>
34 #include <linux/scs.h>
35 #include <linux/percpu-rwsem.h>
36 #include <linux/cpuset.h>
37 #include <linux/random.h>
38 #include <linux/cc_platform.h>
39
40 #include <trace/events/power.h>
41 #define CREATE_TRACE_POINTS
42 #include <trace/events/cpuhp.h>
43
44 #include "smpboot.h"
45
46 /**
47  * struct cpuhp_cpu_state - Per cpu hotplug state storage
48  * @state:      The current cpu state
49  * @target:     The target state
50  * @fail:       Current CPU hotplug callback state
51  * @thread:     Pointer to the hotplug thread
52  * @should_run: Thread should execute
53  * @rollback:   Perform a rollback
54  * @single:     Single callback invocation
55  * @bringup:    Single callback bringup or teardown selector
56  * @cpu:        CPU number
57  * @node:       Remote CPU node; for multi-instance, do a
58  *              single entry callback for install/remove
59  * @last:       For multi-instance rollback, remember how far we got
60  * @cb_state:   The state for a single callback (install/uninstall)
61  * @result:     Result of the operation
62  * @done_up:    Signal completion to the issuer of the task for cpu-up
63  * @done_down:  Signal completion to the issuer of the task for cpu-down
64  */
65 struct cpuhp_cpu_state {
66         enum cpuhp_state        state;
67         enum cpuhp_state        target;
68         enum cpuhp_state        fail;
69 #ifdef CONFIG_SMP
70         struct task_struct      *thread;
71         bool                    should_run;
72         bool                    rollback;
73         bool                    single;
74         bool                    bringup;
75         struct hlist_node       *node;
76         struct hlist_node       *last;
77         enum cpuhp_state        cb_state;
78         int                     result;
79         struct completion       done_up;
80         struct completion       done_down;
81 #endif
82 };
83
84 static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state) = {
85         .fail = CPUHP_INVALID,
86 };
87
88 #ifdef CONFIG_SMP
89 cpumask_t cpus_booted_once_mask;
90 #endif
91
92 #if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP)
93 static struct lockdep_map cpuhp_state_up_map =
94         STATIC_LOCKDEP_MAP_INIT("cpuhp_state-up", &cpuhp_state_up_map);
95 static struct lockdep_map cpuhp_state_down_map =
96         STATIC_LOCKDEP_MAP_INIT("cpuhp_state-down", &cpuhp_state_down_map);
97
98
99 static inline void cpuhp_lock_acquire(bool bringup)
100 {
101         lock_map_acquire(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
102 }
103
104 static inline void cpuhp_lock_release(bool bringup)
105 {
106         lock_map_release(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
107 }
108 #else
109
110 static inline void cpuhp_lock_acquire(bool bringup) { }
111 static inline void cpuhp_lock_release(bool bringup) { }
112
113 #endif
114
115 /**
116  * struct cpuhp_step - Hotplug state machine step
117  * @name:       Name of the step
118  * @startup:    Startup function of the step
119  * @teardown:   Teardown function of the step
120  * @cant_stop:  Bringup/teardown can't be stopped at this step
121  * @multi_instance:     State has multiple instances which get added afterwards
122  */
123 struct cpuhp_step {
124         const char              *name;
125         union {
126                 int             (*single)(unsigned int cpu);
127                 int             (*multi)(unsigned int cpu,
128                                          struct hlist_node *node);
129         } startup;
130         union {
131                 int             (*single)(unsigned int cpu);
132                 int             (*multi)(unsigned int cpu,
133                                          struct hlist_node *node);
134         } teardown;
135         /* private: */
136         struct hlist_head       list;
137         /* public: */
138         bool                    cant_stop;
139         bool                    multi_instance;
140 };
141
142 static DEFINE_MUTEX(cpuhp_state_mutex);
143 static struct cpuhp_step cpuhp_hp_states[];
144
145 static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
146 {
147         return cpuhp_hp_states + state;
148 }
149
150 static bool cpuhp_step_empty(bool bringup, struct cpuhp_step *step)
151 {
152         return bringup ? !step->startup.single : !step->teardown.single;
153 }
154
155 /**
156  * cpuhp_invoke_callback - Invoke the callbacks for a given state
157  * @cpu:        The cpu for which the callback should be invoked
158  * @state:      The state to do callbacks for
159  * @bringup:    True if the bringup callback should be invoked
160  * @node:       For multi-instance, do a single entry callback for install/remove
161  * @lastp:      For multi-instance rollback, remember how far we got
162  *
163  * Called from cpu hotplug and from the state register machinery.
164  *
165  * Return: %0 on success or a negative errno code
166  */
167 static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state,
168                                  bool bringup, struct hlist_node *node,
169                                  struct hlist_node **lastp)
170 {
171         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
172         struct cpuhp_step *step = cpuhp_get_step(state);
173         int (*cbm)(unsigned int cpu, struct hlist_node *node);
174         int (*cb)(unsigned int cpu);
175         int ret, cnt;
176
177         if (st->fail == state) {
178                 st->fail = CPUHP_INVALID;
179                 return -EAGAIN;
180         }
181
182         if (cpuhp_step_empty(bringup, step)) {
183                 WARN_ON_ONCE(1);
184                 return 0;
185         }
186
187         if (!step->multi_instance) {
188                 WARN_ON_ONCE(lastp && *lastp);
189                 cb = bringup ? step->startup.single : step->teardown.single;
190
191                 trace_cpuhp_enter(cpu, st->target, state, cb);
192                 ret = cb(cpu);
193                 trace_cpuhp_exit(cpu, st->state, state, ret);
194                 return ret;
195         }
196         cbm = bringup ? step->startup.multi : step->teardown.multi;
197
198         /* Single invocation for instance add/remove */
199         if (node) {
200                 WARN_ON_ONCE(lastp && *lastp);
201                 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
202                 ret = cbm(cpu, node);
203                 trace_cpuhp_exit(cpu, st->state, state, ret);
204                 return ret;
205         }
206
207         /* State transition. Invoke on all instances */
208         cnt = 0;
209         hlist_for_each(node, &step->list) {
210                 if (lastp && node == *lastp)
211                         break;
212
213                 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
214                 ret = cbm(cpu, node);
215                 trace_cpuhp_exit(cpu, st->state, state, ret);
216                 if (ret) {
217                         if (!lastp)
218                                 goto err;
219
220                         *lastp = node;
221                         return ret;
222                 }
223                 cnt++;
224         }
225         if (lastp)
226                 *lastp = NULL;
227         return 0;
228 err:
229         /* Rollback the instances if one failed */
230         cbm = !bringup ? step->startup.multi : step->teardown.multi;
231         if (!cbm)
232                 return ret;
233
234         hlist_for_each(node, &step->list) {
235                 if (!cnt--)
236                         break;
237
238                 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
239                 ret = cbm(cpu, node);
240                 trace_cpuhp_exit(cpu, st->state, state, ret);
241                 /*
242                  * Rollback must not fail,
243                  */
244                 WARN_ON_ONCE(ret);
245         }
246         return ret;
247 }
248
249 #ifdef CONFIG_SMP
250 static bool cpuhp_is_ap_state(enum cpuhp_state state)
251 {
252         /*
253          * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
254          * purposes as that state is handled explicitly in cpu_down.
255          */
256         return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;
257 }
258
259 static inline void wait_for_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
260 {
261         struct completion *done = bringup ? &st->done_up : &st->done_down;
262         wait_for_completion(done);
263 }
264
265 static inline void complete_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
266 {
267         struct completion *done = bringup ? &st->done_up : &st->done_down;
268         complete(done);
269 }
270
271 /*
272  * The former STARTING/DYING states, ran with IRQs disabled and must not fail.
273  */
274 static bool cpuhp_is_atomic_state(enum cpuhp_state state)
275 {
276         return CPUHP_AP_IDLE_DEAD <= state && state < CPUHP_AP_ONLINE;
277 }
278
279 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
280 static DEFINE_MUTEX(cpu_add_remove_lock);
281 bool cpuhp_tasks_frozen;
282 EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
283
284 /*
285  * The following two APIs (cpu_maps_update_begin/done) must be used when
286  * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
287  */
288 void cpu_maps_update_begin(void)
289 {
290         mutex_lock(&cpu_add_remove_lock);
291 }
292
293 void cpu_maps_update_done(void)
294 {
295         mutex_unlock(&cpu_add_remove_lock);
296 }
297
298 /*
299  * If set, cpu_up and cpu_down will return -EBUSY and do nothing.
300  * Should always be manipulated under cpu_add_remove_lock
301  */
302 static int cpu_hotplug_disabled;
303
304 #ifdef CONFIG_HOTPLUG_CPU
305
306 DEFINE_STATIC_PERCPU_RWSEM(cpu_hotplug_lock);
307
308 void cpus_read_lock(void)
309 {
310         percpu_down_read(&cpu_hotplug_lock);
311 }
312 EXPORT_SYMBOL_GPL(cpus_read_lock);
313
314 int cpus_read_trylock(void)
315 {
316         return percpu_down_read_trylock(&cpu_hotplug_lock);
317 }
318 EXPORT_SYMBOL_GPL(cpus_read_trylock);
319
320 void cpus_read_unlock(void)
321 {
322         percpu_up_read(&cpu_hotplug_lock);
323 }
324 EXPORT_SYMBOL_GPL(cpus_read_unlock);
325
326 void cpus_write_lock(void)
327 {
328         percpu_down_write(&cpu_hotplug_lock);
329 }
330
331 void cpus_write_unlock(void)
332 {
333         percpu_up_write(&cpu_hotplug_lock);
334 }
335
336 void lockdep_assert_cpus_held(void)
337 {
338         /*
339          * We can't have hotplug operations before userspace starts running,
340          * and some init codepaths will knowingly not take the hotplug lock.
341          * This is all valid, so mute lockdep until it makes sense to report
342          * unheld locks.
343          */
344         if (system_state < SYSTEM_RUNNING)
345                 return;
346
347         percpu_rwsem_assert_held(&cpu_hotplug_lock);
348 }
349
350 #ifdef CONFIG_LOCKDEP
351 int lockdep_is_cpus_held(void)
352 {
353         return percpu_rwsem_is_held(&cpu_hotplug_lock);
354 }
355 #endif
356
357 static void lockdep_acquire_cpus_lock(void)
358 {
359         rwsem_acquire(&cpu_hotplug_lock.dep_map, 0, 0, _THIS_IP_);
360 }
361
362 static void lockdep_release_cpus_lock(void)
363 {
364         rwsem_release(&cpu_hotplug_lock.dep_map, _THIS_IP_);
365 }
366
367 /*
368  * Wait for currently running CPU hotplug operations to complete (if any) and
369  * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
370  * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
371  * hotplug path before performing hotplug operations. So acquiring that lock
372  * guarantees mutual exclusion from any currently running hotplug operations.
373  */
374 void cpu_hotplug_disable(void)
375 {
376         cpu_maps_update_begin();
377         cpu_hotplug_disabled++;
378         cpu_maps_update_done();
379 }
380 EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
381
382 static void __cpu_hotplug_enable(void)
383 {
384         if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
385                 return;
386         cpu_hotplug_disabled--;
387 }
388
389 void cpu_hotplug_enable(void)
390 {
391         cpu_maps_update_begin();
392         __cpu_hotplug_enable();
393         cpu_maps_update_done();
394 }
395 EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
396
397 #else
398
399 static void lockdep_acquire_cpus_lock(void)
400 {
401 }
402
403 static void lockdep_release_cpus_lock(void)
404 {
405 }
406
407 #endif  /* CONFIG_HOTPLUG_CPU */
408
409 /*
410  * Architectures that need SMT-specific errata handling during SMT hotplug
411  * should override this.
412  */
413 void __weak arch_smt_update(void) { }
414
415 #ifdef CONFIG_HOTPLUG_SMT
416 enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED;
417
418 void __init cpu_smt_disable(bool force)
419 {
420         if (!cpu_smt_possible())
421                 return;
422
423         if (force) {
424                 pr_info("SMT: Force disabled\n");
425                 cpu_smt_control = CPU_SMT_FORCE_DISABLED;
426         } else {
427                 pr_info("SMT: disabled\n");
428                 cpu_smt_control = CPU_SMT_DISABLED;
429         }
430 }
431
432 /*
433  * The decision whether SMT is supported can only be done after the full
434  * CPU identification. Called from architecture code.
435  */
436 void __init cpu_smt_check_topology(void)
437 {
438         if (!topology_smt_supported())
439                 cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
440 }
441
442 static int __init smt_cmdline_disable(char *str)
443 {
444         cpu_smt_disable(str && !strcmp(str, "force"));
445         return 0;
446 }
447 early_param("nosmt", smt_cmdline_disable);
448
449 static inline bool cpu_smt_allowed(unsigned int cpu)
450 {
451         if (cpu_smt_control == CPU_SMT_ENABLED)
452                 return true;
453
454         if (topology_is_primary_thread(cpu))
455                 return true;
456
457         /*
458          * On x86 it's required to boot all logical CPUs at least once so
459          * that the init code can get a chance to set CR4.MCE on each
460          * CPU. Otherwise, a broadcasted MCE observing CR4.MCE=0b on any
461          * core will shutdown the machine.
462          */
463         return !cpumask_test_cpu(cpu, &cpus_booted_once_mask);
464 }
465
466 /* Returns true if SMT is not supported of forcefully (irreversibly) disabled */
467 bool cpu_smt_possible(void)
468 {
469         return cpu_smt_control != CPU_SMT_FORCE_DISABLED &&
470                 cpu_smt_control != CPU_SMT_NOT_SUPPORTED;
471 }
472 EXPORT_SYMBOL_GPL(cpu_smt_possible);
473 #else
474 static inline bool cpu_smt_allowed(unsigned int cpu) { return true; }
475 #endif
476
477 static inline enum cpuhp_state
478 cpuhp_set_state(int cpu, struct cpuhp_cpu_state *st, enum cpuhp_state target)
479 {
480         enum cpuhp_state prev_state = st->state;
481         bool bringup = st->state < target;
482
483         st->rollback = false;
484         st->last = NULL;
485
486         st->target = target;
487         st->single = false;
488         st->bringup = bringup;
489         if (cpu_dying(cpu) != !bringup)
490                 set_cpu_dying(cpu, !bringup);
491
492         return prev_state;
493 }
494
495 static inline void
496 cpuhp_reset_state(int cpu, struct cpuhp_cpu_state *st,
497                   enum cpuhp_state prev_state)
498 {
499         bool bringup = !st->bringup;
500
501         st->target = prev_state;
502
503         /*
504          * Already rolling back. No need invert the bringup value or to change
505          * the current state.
506          */
507         if (st->rollback)
508                 return;
509
510         st->rollback = true;
511
512         /*
513          * If we have st->last we need to undo partial multi_instance of this
514          * state first. Otherwise start undo at the previous state.
515          */
516         if (!st->last) {
517                 if (st->bringup)
518                         st->state--;
519                 else
520                         st->state++;
521         }
522
523         st->bringup = bringup;
524         if (cpu_dying(cpu) != !bringup)
525                 set_cpu_dying(cpu, !bringup);
526 }
527
528 /* Regular hotplug invocation of the AP hotplug thread */
529 static void __cpuhp_kick_ap(struct cpuhp_cpu_state *st)
530 {
531         if (!st->single && st->state == st->target)
532                 return;
533
534         st->result = 0;
535         /*
536          * Make sure the above stores are visible before should_run becomes
537          * true. Paired with the mb() above in cpuhp_thread_fun()
538          */
539         smp_mb();
540         st->should_run = true;
541         wake_up_process(st->thread);
542         wait_for_ap_thread(st, st->bringup);
543 }
544
545 static int cpuhp_kick_ap(int cpu, struct cpuhp_cpu_state *st,
546                          enum cpuhp_state target)
547 {
548         enum cpuhp_state prev_state;
549         int ret;
550
551         prev_state = cpuhp_set_state(cpu, st, target);
552         __cpuhp_kick_ap(st);
553         if ((ret = st->result)) {
554                 cpuhp_reset_state(cpu, st, prev_state);
555                 __cpuhp_kick_ap(st);
556         }
557
558         return ret;
559 }
560
561 static int bringup_wait_for_ap(unsigned int cpu)
562 {
563         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
564
565         /* Wait for the CPU to reach CPUHP_AP_ONLINE_IDLE */
566         wait_for_ap_thread(st, true);
567         if (WARN_ON_ONCE((!cpu_online(cpu))))
568                 return -ECANCELED;
569
570         /* Unpark the hotplug thread of the target cpu */
571         kthread_unpark(st->thread);
572
573         /*
574          * SMT soft disabling on X86 requires to bring the CPU out of the
575          * BIOS 'wait for SIPI' state in order to set the CR4.MCE bit.  The
576          * CPU marked itself as booted_once in notify_cpu_starting() so the
577          * cpu_smt_allowed() check will now return false if this is not the
578          * primary sibling.
579          */
580         if (!cpu_smt_allowed(cpu))
581                 return -ECANCELED;
582
583         if (st->target <= CPUHP_AP_ONLINE_IDLE)
584                 return 0;
585
586         return cpuhp_kick_ap(cpu, st, st->target);
587 }
588
589 static int bringup_cpu(unsigned int cpu)
590 {
591         struct task_struct *idle = idle_thread_get(cpu);
592         int ret;
593
594         /*
595          * Reset stale stack state from the last time this CPU was online.
596          */
597         scs_task_reset(idle);
598         kasan_unpoison_task_stack(idle);
599
600         /*
601          * Some architectures have to walk the irq descriptors to
602          * setup the vector space for the cpu which comes online.
603          * Prevent irq alloc/free across the bringup.
604          */
605         irq_lock_sparse();
606
607         /* Arch-specific enabling code. */
608         ret = __cpu_up(cpu, idle);
609         irq_unlock_sparse();
610         if (ret)
611                 return ret;
612         return bringup_wait_for_ap(cpu);
613 }
614
615 static int finish_cpu(unsigned int cpu)
616 {
617         struct task_struct *idle = idle_thread_get(cpu);
618         struct mm_struct *mm = idle->active_mm;
619
620         /*
621          * idle_task_exit() will have switched to &init_mm, now
622          * clean up any remaining active_mm state.
623          */
624         if (mm != &init_mm)
625                 idle->active_mm = &init_mm;
626         mmdrop_lazy_tlb(mm);
627         return 0;
628 }
629
630 /*
631  * Hotplug state machine related functions
632  */
633
634 /*
635  * Get the next state to run. Empty ones will be skipped. Returns true if a
636  * state must be run.
637  *
638  * st->state will be modified ahead of time, to match state_to_run, as if it
639  * has already ran.
640  */
641 static bool cpuhp_next_state(bool bringup,
642                              enum cpuhp_state *state_to_run,
643                              struct cpuhp_cpu_state *st,
644                              enum cpuhp_state target)
645 {
646         do {
647                 if (bringup) {
648                         if (st->state >= target)
649                                 return false;
650
651                         *state_to_run = ++st->state;
652                 } else {
653                         if (st->state <= target)
654                                 return false;
655
656                         *state_to_run = st->state--;
657                 }
658
659                 if (!cpuhp_step_empty(bringup, cpuhp_get_step(*state_to_run)))
660                         break;
661         } while (true);
662
663         return true;
664 }
665
666 static int __cpuhp_invoke_callback_range(bool bringup,
667                                          unsigned int cpu,
668                                          struct cpuhp_cpu_state *st,
669                                          enum cpuhp_state target,
670                                          bool nofail)
671 {
672         enum cpuhp_state state;
673         int ret = 0;
674
675         while (cpuhp_next_state(bringup, &state, st, target)) {
676                 int err;
677
678                 err = cpuhp_invoke_callback(cpu, state, bringup, NULL, NULL);
679                 if (!err)
680                         continue;
681
682                 if (nofail) {
683                         pr_warn("CPU %u %s state %s (%d) failed (%d)\n",
684                                 cpu, bringup ? "UP" : "DOWN",
685                                 cpuhp_get_step(st->state)->name,
686                                 st->state, err);
687                         ret = -1;
688                 } else {
689                         ret = err;
690                         break;
691                 }
692         }
693
694         return ret;
695 }
696
697 static inline int cpuhp_invoke_callback_range(bool bringup,
698                                               unsigned int cpu,
699                                               struct cpuhp_cpu_state *st,
700                                               enum cpuhp_state target)
701 {
702         return __cpuhp_invoke_callback_range(bringup, cpu, st, target, false);
703 }
704
705 static inline void cpuhp_invoke_callback_range_nofail(bool bringup,
706                                                       unsigned int cpu,
707                                                       struct cpuhp_cpu_state *st,
708                                                       enum cpuhp_state target)
709 {
710         __cpuhp_invoke_callback_range(bringup, cpu, st, target, true);
711 }
712
713 static inline bool can_rollback_cpu(struct cpuhp_cpu_state *st)
714 {
715         if (IS_ENABLED(CONFIG_HOTPLUG_CPU))
716                 return true;
717         /*
718          * When CPU hotplug is disabled, then taking the CPU down is not
719          * possible because takedown_cpu() and the architecture and
720          * subsystem specific mechanisms are not available. So the CPU
721          * which would be completely unplugged again needs to stay around
722          * in the current state.
723          */
724         return st->state <= CPUHP_BRINGUP_CPU;
725 }
726
727 static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
728                               enum cpuhp_state target)
729 {
730         enum cpuhp_state prev_state = st->state;
731         int ret = 0;
732
733         ret = cpuhp_invoke_callback_range(true, cpu, st, target);
734         if (ret) {
735                 pr_debug("CPU UP failed (%d) CPU %u state %s (%d)\n",
736                          ret, cpu, cpuhp_get_step(st->state)->name,
737                          st->state);
738
739                 cpuhp_reset_state(cpu, st, prev_state);
740                 if (can_rollback_cpu(st))
741                         WARN_ON(cpuhp_invoke_callback_range(false, cpu, st,
742                                                             prev_state));
743         }
744         return ret;
745 }
746
747 /*
748  * The cpu hotplug threads manage the bringup and teardown of the cpus
749  */
750 static int cpuhp_should_run(unsigned int cpu)
751 {
752         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
753
754         return st->should_run;
755 }
756
757 /*
758  * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
759  * callbacks when a state gets [un]installed at runtime.
760  *
761  * Each invocation of this function by the smpboot thread does a single AP
762  * state callback.
763  *
764  * It has 3 modes of operation:
765  *  - single: runs st->cb_state
766  *  - up:     runs ++st->state, while st->state < st->target
767  *  - down:   runs st->state--, while st->state > st->target
768  *
769  * When complete or on error, should_run is cleared and the completion is fired.
770  */
771 static void cpuhp_thread_fun(unsigned int cpu)
772 {
773         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
774         bool bringup = st->bringup;
775         enum cpuhp_state state;
776
777         if (WARN_ON_ONCE(!st->should_run))
778                 return;
779
780         /*
781          * ACQUIRE for the cpuhp_should_run() load of ->should_run. Ensures
782          * that if we see ->should_run we also see the rest of the state.
783          */
784         smp_mb();
785
786         /*
787          * The BP holds the hotplug lock, but we're now running on the AP,
788          * ensure that anybody asserting the lock is held, will actually find
789          * it so.
790          */
791         lockdep_acquire_cpus_lock();
792         cpuhp_lock_acquire(bringup);
793
794         if (st->single) {
795                 state = st->cb_state;
796                 st->should_run = false;
797         } else {
798                 st->should_run = cpuhp_next_state(bringup, &state, st, st->target);
799                 if (!st->should_run)
800                         goto end;
801         }
802
803         WARN_ON_ONCE(!cpuhp_is_ap_state(state));
804
805         if (cpuhp_is_atomic_state(state)) {
806                 local_irq_disable();
807                 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
808                 local_irq_enable();
809
810                 /*
811                  * STARTING/DYING must not fail!
812                  */
813                 WARN_ON_ONCE(st->result);
814         } else {
815                 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
816         }
817
818         if (st->result) {
819                 /*
820                  * If we fail on a rollback, we're up a creek without no
821                  * paddle, no way forward, no way back. We loose, thanks for
822                  * playing.
823                  */
824                 WARN_ON_ONCE(st->rollback);
825                 st->should_run = false;
826         }
827
828 end:
829         cpuhp_lock_release(bringup);
830         lockdep_release_cpus_lock();
831
832         if (!st->should_run)
833                 complete_ap_thread(st, bringup);
834 }
835
836 /* Invoke a single callback on a remote cpu */
837 static int
838 cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, bool bringup,
839                          struct hlist_node *node)
840 {
841         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
842         int ret;
843
844         if (!cpu_online(cpu))
845                 return 0;
846
847         cpuhp_lock_acquire(false);
848         cpuhp_lock_release(false);
849
850         cpuhp_lock_acquire(true);
851         cpuhp_lock_release(true);
852
853         /*
854          * If we are up and running, use the hotplug thread. For early calls
855          * we invoke the thread function directly.
856          */
857         if (!st->thread)
858                 return cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
859
860         st->rollback = false;
861         st->last = NULL;
862
863         st->node = node;
864         st->bringup = bringup;
865         st->cb_state = state;
866         st->single = true;
867
868         __cpuhp_kick_ap(st);
869
870         /*
871          * If we failed and did a partial, do a rollback.
872          */
873         if ((ret = st->result) && st->last) {
874                 st->rollback = true;
875                 st->bringup = !bringup;
876
877                 __cpuhp_kick_ap(st);
878         }
879
880         /*
881          * Clean up the leftovers so the next hotplug operation wont use stale
882          * data.
883          */
884         st->node = st->last = NULL;
885         return ret;
886 }
887
888 static int cpuhp_kick_ap_work(unsigned int cpu)
889 {
890         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
891         enum cpuhp_state prev_state = st->state;
892         int ret;
893
894         cpuhp_lock_acquire(false);
895         cpuhp_lock_release(false);
896
897         cpuhp_lock_acquire(true);
898         cpuhp_lock_release(true);
899
900         trace_cpuhp_enter(cpu, st->target, prev_state, cpuhp_kick_ap_work);
901         ret = cpuhp_kick_ap(cpu, st, st->target);
902         trace_cpuhp_exit(cpu, st->state, prev_state, ret);
903
904         return ret;
905 }
906
907 static struct smp_hotplug_thread cpuhp_threads = {
908         .store                  = &cpuhp_state.thread,
909         .thread_should_run      = cpuhp_should_run,
910         .thread_fn              = cpuhp_thread_fun,
911         .thread_comm            = "cpuhp/%u",
912         .selfparking            = true,
913 };
914
915 static __init void cpuhp_init_state(void)
916 {
917         struct cpuhp_cpu_state *st;
918         int cpu;
919
920         for_each_possible_cpu(cpu) {
921                 st = per_cpu_ptr(&cpuhp_state, cpu);
922                 init_completion(&st->done_up);
923                 init_completion(&st->done_down);
924         }
925 }
926
927 void __init cpuhp_threads_init(void)
928 {
929         cpuhp_init_state();
930         BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
931         kthread_unpark(this_cpu_read(cpuhp_state.thread));
932 }
933
934 /*
935  *
936  * Serialize hotplug trainwrecks outside of the cpu_hotplug_lock
937  * protected region.
938  *
939  * The operation is still serialized against concurrent CPU hotplug via
940  * cpu_add_remove_lock, i.e. CPU map protection.  But it is _not_
941  * serialized against other hotplug related activity like adding or
942  * removing of state callbacks and state instances, which invoke either the
943  * startup or the teardown callback of the affected state.
944  *
945  * This is required for subsystems which are unfixable vs. CPU hotplug and
946  * evade lock inversion problems by scheduling work which has to be
947  * completed _before_ cpu_up()/_cpu_down() returns.
948  *
949  * Don't even think about adding anything to this for any new code or even
950  * drivers. It's only purpose is to keep existing lock order trainwrecks
951  * working.
952  *
953  * For cpu_down() there might be valid reasons to finish cleanups which are
954  * not required to be done under cpu_hotplug_lock, but that's a different
955  * story and would be not invoked via this.
956  */
957 static void cpu_up_down_serialize_trainwrecks(bool tasks_frozen)
958 {
959         /*
960          * cpusets delegate hotplug operations to a worker to "solve" the
961          * lock order problems. Wait for the worker, but only if tasks are
962          * _not_ frozen (suspend, hibernate) as that would wait forever.
963          *
964          * The wait is required because otherwise the hotplug operation
965          * returns with inconsistent state, which could even be observed in
966          * user space when a new CPU is brought up. The CPU plug uevent
967          * would be delivered and user space reacting on it would fail to
968          * move tasks to the newly plugged CPU up to the point where the
969          * work has finished because up to that point the newly plugged CPU
970          * is not assignable in cpusets/cgroups. On unplug that's not
971          * necessarily a visible issue, but it is still inconsistent state,
972          * which is the real problem which needs to be "fixed". This can't
973          * prevent the transient state between scheduling the work and
974          * returning from waiting for it.
975          */
976         if (!tasks_frozen)
977                 cpuset_wait_for_hotplug();
978 }
979
980 #ifdef CONFIG_HOTPLUG_CPU
981 #ifndef arch_clear_mm_cpumask_cpu
982 #define arch_clear_mm_cpumask_cpu(cpu, mm) cpumask_clear_cpu(cpu, mm_cpumask(mm))
983 #endif
984
985 /**
986  * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
987  * @cpu: a CPU id
988  *
989  * This function walks all processes, finds a valid mm struct for each one and
990  * then clears a corresponding bit in mm's cpumask.  While this all sounds
991  * trivial, there are various non-obvious corner cases, which this function
992  * tries to solve in a safe manner.
993  *
994  * Also note that the function uses a somewhat relaxed locking scheme, so it may
995  * be called only for an already offlined CPU.
996  */
997 void clear_tasks_mm_cpumask(int cpu)
998 {
999         struct task_struct *p;
1000
1001         /*
1002          * This function is called after the cpu is taken down and marked
1003          * offline, so its not like new tasks will ever get this cpu set in
1004          * their mm mask. -- Peter Zijlstra
1005          * Thus, we may use rcu_read_lock() here, instead of grabbing
1006          * full-fledged tasklist_lock.
1007          */
1008         WARN_ON(cpu_online(cpu));
1009         rcu_read_lock();
1010         for_each_process(p) {
1011                 struct task_struct *t;
1012
1013                 /*
1014                  * Main thread might exit, but other threads may still have
1015                  * a valid mm. Find one.
1016                  */
1017                 t = find_lock_task_mm(p);
1018                 if (!t)
1019                         continue;
1020                 arch_clear_mm_cpumask_cpu(cpu, t->mm);
1021                 task_unlock(t);
1022         }
1023         rcu_read_unlock();
1024 }
1025
1026 /* Take this CPU down. */
1027 static int take_cpu_down(void *_param)
1028 {
1029         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1030         enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
1031         int err, cpu = smp_processor_id();
1032
1033         /* Ensure this CPU doesn't handle any more interrupts. */
1034         err = __cpu_disable();
1035         if (err < 0)
1036                 return err;
1037
1038         /*
1039          * Must be called from CPUHP_TEARDOWN_CPU, which means, as we are going
1040          * down, that the current state is CPUHP_TEARDOWN_CPU - 1.
1041          */
1042         WARN_ON(st->state != (CPUHP_TEARDOWN_CPU - 1));
1043
1044         /*
1045          * Invoke the former CPU_DYING callbacks. DYING must not fail!
1046          */
1047         cpuhp_invoke_callback_range_nofail(false, cpu, st, target);
1048
1049         /* Give up timekeeping duties */
1050         tick_handover_do_timer();
1051         /* Remove CPU from timer broadcasting */
1052         tick_offline_cpu(cpu);
1053         /* Park the stopper thread */
1054         stop_machine_park(cpu);
1055         return 0;
1056 }
1057
1058 static int takedown_cpu(unsigned int cpu)
1059 {
1060         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1061         int err;
1062
1063         /* Park the smpboot threads */
1064         kthread_park(st->thread);
1065
1066         /*
1067          * Prevent irq alloc/free while the dying cpu reorganizes the
1068          * interrupt affinities.
1069          */
1070         irq_lock_sparse();
1071
1072         /*
1073          * So now all preempt/rcu users must observe !cpu_active().
1074          */
1075         err = stop_machine_cpuslocked(take_cpu_down, NULL, cpumask_of(cpu));
1076         if (err) {
1077                 /* CPU refused to die */
1078                 irq_unlock_sparse();
1079                 /* Unpark the hotplug thread so we can rollback there */
1080                 kthread_unpark(st->thread);
1081                 return err;
1082         }
1083         BUG_ON(cpu_online(cpu));
1084
1085         /*
1086          * The teardown callback for CPUHP_AP_SCHED_STARTING will have removed
1087          * all runnable tasks from the CPU, there's only the idle task left now
1088          * that the migration thread is done doing the stop_machine thing.
1089          *
1090          * Wait for the stop thread to go away.
1091          */
1092         wait_for_ap_thread(st, false);
1093         BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
1094
1095         /* Interrupts are moved away from the dying cpu, reenable alloc/free */
1096         irq_unlock_sparse();
1097
1098         hotplug_cpu__broadcast_tick_pull(cpu);
1099         /* This actually kills the CPU. */
1100         __cpu_die(cpu);
1101
1102         tick_cleanup_dead_cpu(cpu);
1103         rcutree_migrate_callbacks(cpu);
1104         return 0;
1105 }
1106
1107 static void cpuhp_complete_idle_dead(void *arg)
1108 {
1109         struct cpuhp_cpu_state *st = arg;
1110
1111         complete_ap_thread(st, false);
1112 }
1113
1114 void cpuhp_report_idle_dead(void)
1115 {
1116         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1117
1118         BUG_ON(st->state != CPUHP_AP_OFFLINE);
1119         rcu_report_dead(smp_processor_id());
1120         st->state = CPUHP_AP_IDLE_DEAD;
1121         /*
1122          * We cannot call complete after rcu_report_dead() so we delegate it
1123          * to an online cpu.
1124          */
1125         smp_call_function_single(cpumask_first(cpu_online_mask),
1126                                  cpuhp_complete_idle_dead, st, 0);
1127 }
1128
1129 static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
1130                                 enum cpuhp_state target)
1131 {
1132         enum cpuhp_state prev_state = st->state;
1133         int ret = 0;
1134
1135         ret = cpuhp_invoke_callback_range(false, cpu, st, target);
1136         if (ret) {
1137                 pr_debug("CPU DOWN failed (%d) CPU %u state %s (%d)\n",
1138                          ret, cpu, cpuhp_get_step(st->state)->name,
1139                          st->state);
1140
1141                 cpuhp_reset_state(cpu, st, prev_state);
1142
1143                 if (st->state < prev_state)
1144                         WARN_ON(cpuhp_invoke_callback_range(true, cpu, st,
1145                                                             prev_state));
1146         }
1147
1148         return ret;
1149 }
1150
1151 /* Requires cpu_add_remove_lock to be held */
1152 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
1153                            enum cpuhp_state target)
1154 {
1155         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1156         int prev_state, ret = 0;
1157
1158         if (num_online_cpus() == 1)
1159                 return -EBUSY;
1160
1161         if (!cpu_present(cpu))
1162                 return -EINVAL;
1163
1164         cpus_write_lock();
1165
1166         cpuhp_tasks_frozen = tasks_frozen;
1167
1168         prev_state = cpuhp_set_state(cpu, st, target);
1169         /*
1170          * If the current CPU state is in the range of the AP hotplug thread,
1171          * then we need to kick the thread.
1172          */
1173         if (st->state > CPUHP_TEARDOWN_CPU) {
1174                 st->target = max((int)target, CPUHP_TEARDOWN_CPU);
1175                 ret = cpuhp_kick_ap_work(cpu);
1176                 /*
1177                  * The AP side has done the error rollback already. Just
1178                  * return the error code..
1179                  */
1180                 if (ret)
1181                         goto out;
1182
1183                 /*
1184                  * We might have stopped still in the range of the AP hotplug
1185                  * thread. Nothing to do anymore.
1186                  */
1187                 if (st->state > CPUHP_TEARDOWN_CPU)
1188                         goto out;
1189
1190                 st->target = target;
1191         }
1192         /*
1193          * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
1194          * to do the further cleanups.
1195          */
1196         ret = cpuhp_down_callbacks(cpu, st, target);
1197         if (ret && st->state < prev_state) {
1198                 if (st->state == CPUHP_TEARDOWN_CPU) {
1199                         cpuhp_reset_state(cpu, st, prev_state);
1200                         __cpuhp_kick_ap(st);
1201                 } else {
1202                         WARN(1, "DEAD callback error for CPU%d", cpu);
1203                 }
1204         }
1205
1206 out:
1207         cpus_write_unlock();
1208         /*
1209          * Do post unplug cleanup. This is still protected against
1210          * concurrent CPU hotplug via cpu_add_remove_lock.
1211          */
1212         lockup_detector_cleanup();
1213         arch_smt_update();
1214         cpu_up_down_serialize_trainwrecks(tasks_frozen);
1215         return ret;
1216 }
1217
1218 static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target)
1219 {
1220         /*
1221          * If the platform does not support hotplug, report it explicitly to
1222          * differentiate it from a transient offlining failure.
1223          */
1224         if (cc_platform_has(CC_ATTR_HOTPLUG_DISABLED))
1225                 return -EOPNOTSUPP;
1226         if (cpu_hotplug_disabled)
1227                 return -EBUSY;
1228         return _cpu_down(cpu, 0, target);
1229 }
1230
1231 static int cpu_down(unsigned int cpu, enum cpuhp_state target)
1232 {
1233         int err;
1234
1235         cpu_maps_update_begin();
1236         err = cpu_down_maps_locked(cpu, target);
1237         cpu_maps_update_done();
1238         return err;
1239 }
1240
1241 /**
1242  * cpu_device_down - Bring down a cpu device
1243  * @dev: Pointer to the cpu device to offline
1244  *
1245  * This function is meant to be used by device core cpu subsystem only.
1246  *
1247  * Other subsystems should use remove_cpu() instead.
1248  *
1249  * Return: %0 on success or a negative errno code
1250  */
1251 int cpu_device_down(struct device *dev)
1252 {
1253         return cpu_down(dev->id, CPUHP_OFFLINE);
1254 }
1255
1256 int remove_cpu(unsigned int cpu)
1257 {
1258         int ret;
1259
1260         lock_device_hotplug();
1261         ret = device_offline(get_cpu_device(cpu));
1262         unlock_device_hotplug();
1263
1264         return ret;
1265 }
1266 EXPORT_SYMBOL_GPL(remove_cpu);
1267
1268 void smp_shutdown_nonboot_cpus(unsigned int primary_cpu)
1269 {
1270         unsigned int cpu;
1271         int error;
1272
1273         cpu_maps_update_begin();
1274
1275         /*
1276          * Make certain the cpu I'm about to reboot on is online.
1277          *
1278          * This is inline to what migrate_to_reboot_cpu() already do.
1279          */
1280         if (!cpu_online(primary_cpu))
1281                 primary_cpu = cpumask_first(cpu_online_mask);
1282
1283         for_each_online_cpu(cpu) {
1284                 if (cpu == primary_cpu)
1285                         continue;
1286
1287                 error = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
1288                 if (error) {
1289                         pr_err("Failed to offline CPU%d - error=%d",
1290                                 cpu, error);
1291                         break;
1292                 }
1293         }
1294
1295         /*
1296          * Ensure all but the reboot CPU are offline.
1297          */
1298         BUG_ON(num_online_cpus() > 1);
1299
1300         /*
1301          * Make sure the CPUs won't be enabled by someone else after this
1302          * point. Kexec will reboot to a new kernel shortly resetting
1303          * everything along the way.
1304          */
1305         cpu_hotplug_disabled++;
1306
1307         cpu_maps_update_done();
1308 }
1309
1310 #else
1311 #define takedown_cpu            NULL
1312 #endif /*CONFIG_HOTPLUG_CPU*/
1313
1314 /**
1315  * notify_cpu_starting(cpu) - Invoke the callbacks on the starting CPU
1316  * @cpu: cpu that just started
1317  *
1318  * It must be called by the arch code on the new cpu, before the new cpu
1319  * enables interrupts and before the "boot" cpu returns from __cpu_up().
1320  */
1321 void notify_cpu_starting(unsigned int cpu)
1322 {
1323         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1324         enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
1325
1326         rcu_cpu_starting(cpu);  /* Enables RCU usage on this CPU. */
1327         cpumask_set_cpu(cpu, &cpus_booted_once_mask);
1328
1329         /*
1330          * STARTING must not fail!
1331          */
1332         cpuhp_invoke_callback_range_nofail(true, cpu, st, target);
1333 }
1334
1335 /*
1336  * Called from the idle task. Wake up the controlling task which brings the
1337  * hotplug thread of the upcoming CPU up and then delegates the rest of the
1338  * online bringup to the hotplug thread.
1339  */
1340 void cpuhp_online_idle(enum cpuhp_state state)
1341 {
1342         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1343
1344         /* Happens for the boot cpu */
1345         if (state != CPUHP_AP_ONLINE_IDLE)
1346                 return;
1347
1348         /*
1349          * Unpart the stopper thread before we start the idle loop (and start
1350          * scheduling); this ensures the stopper task is always available.
1351          */
1352         stop_machine_unpark(smp_processor_id());
1353
1354         st->state = CPUHP_AP_ONLINE_IDLE;
1355         complete_ap_thread(st, true);
1356 }
1357
1358 /* Requires cpu_add_remove_lock to be held */
1359 static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
1360 {
1361         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1362         struct task_struct *idle;
1363         int ret = 0;
1364
1365         cpus_write_lock();
1366
1367         if (!cpu_present(cpu)) {
1368                 ret = -EINVAL;
1369                 goto out;
1370         }
1371
1372         /*
1373          * The caller of cpu_up() might have raced with another
1374          * caller. Nothing to do.
1375          */
1376         if (st->state >= target)
1377                 goto out;
1378
1379         if (st->state == CPUHP_OFFLINE) {
1380                 /* Let it fail before we try to bring the cpu up */
1381                 idle = idle_thread_get(cpu);
1382                 if (IS_ERR(idle)) {
1383                         ret = PTR_ERR(idle);
1384                         goto out;
1385                 }
1386         }
1387
1388         cpuhp_tasks_frozen = tasks_frozen;
1389
1390         cpuhp_set_state(cpu, st, target);
1391         /*
1392          * If the current CPU state is in the range of the AP hotplug thread,
1393          * then we need to kick the thread once more.
1394          */
1395         if (st->state > CPUHP_BRINGUP_CPU) {
1396                 ret = cpuhp_kick_ap_work(cpu);
1397                 /*
1398                  * The AP side has done the error rollback already. Just
1399                  * return the error code..
1400                  */
1401                 if (ret)
1402                         goto out;
1403         }
1404
1405         /*
1406          * Try to reach the target state. We max out on the BP at
1407          * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
1408          * responsible for bringing it up to the target state.
1409          */
1410         target = min((int)target, CPUHP_BRINGUP_CPU);
1411         ret = cpuhp_up_callbacks(cpu, st, target);
1412 out:
1413         cpus_write_unlock();
1414         arch_smt_update();
1415         cpu_up_down_serialize_trainwrecks(tasks_frozen);
1416         return ret;
1417 }
1418
1419 static int cpu_up(unsigned int cpu, enum cpuhp_state target)
1420 {
1421         int err = 0;
1422
1423         if (!cpu_possible(cpu)) {
1424                 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
1425                        cpu);
1426 #if defined(CONFIG_IA64)
1427                 pr_err("please check additional_cpus= boot parameter\n");
1428 #endif
1429                 return -EINVAL;
1430         }
1431
1432         err = try_online_node(cpu_to_node(cpu));
1433         if (err)
1434                 return err;
1435
1436         cpu_maps_update_begin();
1437
1438         if (cpu_hotplug_disabled) {
1439                 err = -EBUSY;
1440                 goto out;
1441         }
1442         if (!cpu_smt_allowed(cpu)) {
1443                 err = -EPERM;
1444                 goto out;
1445         }
1446
1447         err = _cpu_up(cpu, 0, target);
1448 out:
1449         cpu_maps_update_done();
1450         return err;
1451 }
1452
1453 /**
1454  * cpu_device_up - Bring up a cpu device
1455  * @dev: Pointer to the cpu device to online
1456  *
1457  * This function is meant to be used by device core cpu subsystem only.
1458  *
1459  * Other subsystems should use add_cpu() instead.
1460  *
1461  * Return: %0 on success or a negative errno code
1462  */
1463 int cpu_device_up(struct device *dev)
1464 {
1465         return cpu_up(dev->id, CPUHP_ONLINE);
1466 }
1467
1468 int add_cpu(unsigned int cpu)
1469 {
1470         int ret;
1471
1472         lock_device_hotplug();
1473         ret = device_online(get_cpu_device(cpu));
1474         unlock_device_hotplug();
1475
1476         return ret;
1477 }
1478 EXPORT_SYMBOL_GPL(add_cpu);
1479
1480 /**
1481  * bringup_hibernate_cpu - Bring up the CPU that we hibernated on
1482  * @sleep_cpu: The cpu we hibernated on and should be brought up.
1483  *
1484  * On some architectures like arm64, we can hibernate on any CPU, but on
1485  * wake up the CPU we hibernated on might be offline as a side effect of
1486  * using maxcpus= for example.
1487  *
1488  * Return: %0 on success or a negative errno code
1489  */
1490 int bringup_hibernate_cpu(unsigned int sleep_cpu)
1491 {
1492         int ret;
1493
1494         if (!cpu_online(sleep_cpu)) {
1495                 pr_info("Hibernated on a CPU that is offline! Bringing CPU up.\n");
1496                 ret = cpu_up(sleep_cpu, CPUHP_ONLINE);
1497                 if (ret) {
1498                         pr_err("Failed to bring hibernate-CPU up!\n");
1499                         return ret;
1500                 }
1501         }
1502         return 0;
1503 }
1504
1505 void bringup_nonboot_cpus(unsigned int setup_max_cpus)
1506 {
1507         unsigned int cpu;
1508
1509         for_each_present_cpu(cpu) {
1510                 if (num_online_cpus() >= setup_max_cpus)
1511                         break;
1512                 if (!cpu_online(cpu))
1513                         cpu_up(cpu, CPUHP_ONLINE);
1514         }
1515 }
1516
1517 #ifdef CONFIG_PM_SLEEP_SMP
1518 static cpumask_var_t frozen_cpus;
1519
1520 int freeze_secondary_cpus(int primary)
1521 {
1522         int cpu, error = 0;
1523
1524         cpu_maps_update_begin();
1525         if (primary == -1) {
1526                 primary = cpumask_first(cpu_online_mask);
1527                 if (!housekeeping_cpu(primary, HK_TYPE_TIMER))
1528                         primary = housekeeping_any_cpu(HK_TYPE_TIMER);
1529         } else {
1530                 if (!cpu_online(primary))
1531                         primary = cpumask_first(cpu_online_mask);
1532         }
1533
1534         /*
1535          * We take down all of the non-boot CPUs in one shot to avoid races
1536          * with the userspace trying to use the CPU hotplug at the same time
1537          */
1538         cpumask_clear(frozen_cpus);
1539
1540         pr_info("Disabling non-boot CPUs ...\n");
1541         for_each_online_cpu(cpu) {
1542                 if (cpu == primary)
1543                         continue;
1544
1545                 if (pm_wakeup_pending()) {
1546                         pr_info("Wakeup pending. Abort CPU freeze\n");
1547                         error = -EBUSY;
1548                         break;
1549                 }
1550
1551                 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
1552                 error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
1553                 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
1554                 if (!error)
1555                         cpumask_set_cpu(cpu, frozen_cpus);
1556                 else {
1557                         pr_err("Error taking CPU%d down: %d\n", cpu, error);
1558                         break;
1559                 }
1560         }
1561
1562         if (!error)
1563                 BUG_ON(num_online_cpus() > 1);
1564         else
1565                 pr_err("Non-boot CPUs are not disabled\n");
1566
1567         /*
1568          * Make sure the CPUs won't be enabled by someone else. We need to do
1569          * this even in case of failure as all freeze_secondary_cpus() users are
1570          * supposed to do thaw_secondary_cpus() on the failure path.
1571          */
1572         cpu_hotplug_disabled++;
1573
1574         cpu_maps_update_done();
1575         return error;
1576 }
1577
1578 void __weak arch_thaw_secondary_cpus_begin(void)
1579 {
1580 }
1581
1582 void __weak arch_thaw_secondary_cpus_end(void)
1583 {
1584 }
1585
1586 void thaw_secondary_cpus(void)
1587 {
1588         int cpu, error;
1589
1590         /* Allow everyone to use the CPU hotplug again */
1591         cpu_maps_update_begin();
1592         __cpu_hotplug_enable();
1593         if (cpumask_empty(frozen_cpus))
1594                 goto out;
1595
1596         pr_info("Enabling non-boot CPUs ...\n");
1597
1598         arch_thaw_secondary_cpus_begin();
1599
1600         for_each_cpu(cpu, frozen_cpus) {
1601                 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
1602                 error = _cpu_up(cpu, 1, CPUHP_ONLINE);
1603                 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
1604                 if (!error) {
1605                         pr_info("CPU%d is up\n", cpu);
1606                         continue;
1607                 }
1608                 pr_warn("Error taking CPU%d up: %d\n", cpu, error);
1609         }
1610
1611         arch_thaw_secondary_cpus_end();
1612
1613         cpumask_clear(frozen_cpus);
1614 out:
1615         cpu_maps_update_done();
1616 }
1617
1618 static int __init alloc_frozen_cpus(void)
1619 {
1620         if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
1621                 return -ENOMEM;
1622         return 0;
1623 }
1624 core_initcall(alloc_frozen_cpus);
1625
1626 /*
1627  * When callbacks for CPU hotplug notifications are being executed, we must
1628  * ensure that the state of the system with respect to the tasks being frozen
1629  * or not, as reported by the notification, remains unchanged *throughout the
1630  * duration* of the execution of the callbacks.
1631  * Hence we need to prevent the freezer from racing with regular CPU hotplug.
1632  *
1633  * This synchronization is implemented by mutually excluding regular CPU
1634  * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
1635  * Hibernate notifications.
1636  */
1637 static int
1638 cpu_hotplug_pm_callback(struct notifier_block *nb,
1639                         unsigned long action, void *ptr)
1640 {
1641         switch (action) {
1642
1643         case PM_SUSPEND_PREPARE:
1644         case PM_HIBERNATION_PREPARE:
1645                 cpu_hotplug_disable();
1646                 break;
1647
1648         case PM_POST_SUSPEND:
1649         case PM_POST_HIBERNATION:
1650                 cpu_hotplug_enable();
1651                 break;
1652
1653         default:
1654                 return NOTIFY_DONE;
1655         }
1656
1657         return NOTIFY_OK;
1658 }
1659
1660
1661 static int __init cpu_hotplug_pm_sync_init(void)
1662 {
1663         /*
1664          * cpu_hotplug_pm_callback has higher priority than x86
1665          * bsp_pm_callback which depends on cpu_hotplug_pm_callback
1666          * to disable cpu hotplug to avoid cpu hotplug race.
1667          */
1668         pm_notifier(cpu_hotplug_pm_callback, 0);
1669         return 0;
1670 }
1671 core_initcall(cpu_hotplug_pm_sync_init);
1672
1673 #endif /* CONFIG_PM_SLEEP_SMP */
1674
1675 int __boot_cpu_id;
1676
1677 #endif /* CONFIG_SMP */
1678
1679 /* Boot processor state steps */
1680 static struct cpuhp_step cpuhp_hp_states[] = {
1681         [CPUHP_OFFLINE] = {
1682                 .name                   = "offline",
1683                 .startup.single         = NULL,
1684                 .teardown.single        = NULL,
1685         },
1686 #ifdef CONFIG_SMP
1687         [CPUHP_CREATE_THREADS]= {
1688                 .name                   = "threads:prepare",
1689                 .startup.single         = smpboot_create_threads,
1690                 .teardown.single        = NULL,
1691                 .cant_stop              = true,
1692         },
1693         [CPUHP_PERF_PREPARE] = {
1694                 .name                   = "perf:prepare",
1695                 .startup.single         = perf_event_init_cpu,
1696                 .teardown.single        = perf_event_exit_cpu,
1697         },
1698         [CPUHP_RANDOM_PREPARE] = {
1699                 .name                   = "random:prepare",
1700                 .startup.single         = random_prepare_cpu,
1701                 .teardown.single        = NULL,
1702         },
1703         [CPUHP_WORKQUEUE_PREP] = {
1704                 .name                   = "workqueue:prepare",
1705                 .startup.single         = workqueue_prepare_cpu,
1706                 .teardown.single        = NULL,
1707         },
1708         [CPUHP_HRTIMERS_PREPARE] = {
1709                 .name                   = "hrtimers:prepare",
1710                 .startup.single         = hrtimers_prepare_cpu,
1711                 .teardown.single        = hrtimers_dead_cpu,
1712         },
1713         [CPUHP_SMPCFD_PREPARE] = {
1714                 .name                   = "smpcfd:prepare",
1715                 .startup.single         = smpcfd_prepare_cpu,
1716                 .teardown.single        = smpcfd_dead_cpu,
1717         },
1718         [CPUHP_RELAY_PREPARE] = {
1719                 .name                   = "relay:prepare",
1720                 .startup.single         = relay_prepare_cpu,
1721                 .teardown.single        = NULL,
1722         },
1723         [CPUHP_SLAB_PREPARE] = {
1724                 .name                   = "slab:prepare",
1725                 .startup.single         = slab_prepare_cpu,
1726                 .teardown.single        = slab_dead_cpu,
1727         },
1728         [CPUHP_RCUTREE_PREP] = {
1729                 .name                   = "RCU/tree:prepare",
1730                 .startup.single         = rcutree_prepare_cpu,
1731                 .teardown.single        = rcutree_dead_cpu,
1732         },
1733         /*
1734          * On the tear-down path, timers_dead_cpu() must be invoked
1735          * before blk_mq_queue_reinit_notify() from notify_dead(),
1736          * otherwise a RCU stall occurs.
1737          */
1738         [CPUHP_TIMERS_PREPARE] = {
1739                 .name                   = "timers:prepare",
1740                 .startup.single         = timers_prepare_cpu,
1741                 .teardown.single        = timers_dead_cpu,
1742         },
1743         /* Kicks the plugged cpu into life */
1744         [CPUHP_BRINGUP_CPU] = {
1745                 .name                   = "cpu:bringup",
1746                 .startup.single         = bringup_cpu,
1747                 .teardown.single        = finish_cpu,
1748                 .cant_stop              = true,
1749         },
1750         /* Final state before CPU kills itself */
1751         [CPUHP_AP_IDLE_DEAD] = {
1752                 .name                   = "idle:dead",
1753         },
1754         /*
1755          * Last state before CPU enters the idle loop to die. Transient state
1756          * for synchronization.
1757          */
1758         [CPUHP_AP_OFFLINE] = {
1759                 .name                   = "ap:offline",
1760                 .cant_stop              = true,
1761         },
1762         /* First state is scheduler control. Interrupts are disabled */
1763         [CPUHP_AP_SCHED_STARTING] = {
1764                 .name                   = "sched:starting",
1765                 .startup.single         = sched_cpu_starting,
1766                 .teardown.single        = sched_cpu_dying,
1767         },
1768         [CPUHP_AP_RCUTREE_DYING] = {
1769                 .name                   = "RCU/tree:dying",
1770                 .startup.single         = NULL,
1771                 .teardown.single        = rcutree_dying_cpu,
1772         },
1773         [CPUHP_AP_SMPCFD_DYING] = {
1774                 .name                   = "smpcfd:dying",
1775                 .startup.single         = NULL,
1776                 .teardown.single        = smpcfd_dying_cpu,
1777         },
1778         /* Entry state on starting. Interrupts enabled from here on. Transient
1779          * state for synchronsization */
1780         [CPUHP_AP_ONLINE] = {
1781                 .name                   = "ap:online",
1782         },
1783         /*
1784          * Handled on control processor until the plugged processor manages
1785          * this itself.
1786          */
1787         [CPUHP_TEARDOWN_CPU] = {
1788                 .name                   = "cpu:teardown",
1789                 .startup.single         = NULL,
1790                 .teardown.single        = takedown_cpu,
1791                 .cant_stop              = true,
1792         },
1793
1794         [CPUHP_AP_SCHED_WAIT_EMPTY] = {
1795                 .name                   = "sched:waitempty",
1796                 .startup.single         = NULL,
1797                 .teardown.single        = sched_cpu_wait_empty,
1798         },
1799
1800         /* Handle smpboot threads park/unpark */
1801         [CPUHP_AP_SMPBOOT_THREADS] = {
1802                 .name                   = "smpboot/threads:online",
1803                 .startup.single         = smpboot_unpark_threads,
1804                 .teardown.single        = smpboot_park_threads,
1805         },
1806         [CPUHP_AP_IRQ_AFFINITY_ONLINE] = {
1807                 .name                   = "irq/affinity:online",
1808                 .startup.single         = irq_affinity_online_cpu,
1809                 .teardown.single        = NULL,
1810         },
1811         [CPUHP_AP_PERF_ONLINE] = {
1812                 .name                   = "perf:online",
1813                 .startup.single         = perf_event_init_cpu,
1814                 .teardown.single        = perf_event_exit_cpu,
1815         },
1816         [CPUHP_AP_WATCHDOG_ONLINE] = {
1817                 .name                   = "lockup_detector:online",
1818                 .startup.single         = lockup_detector_online_cpu,
1819                 .teardown.single        = lockup_detector_offline_cpu,
1820         },
1821         [CPUHP_AP_WORKQUEUE_ONLINE] = {
1822                 .name                   = "workqueue:online",
1823                 .startup.single         = workqueue_online_cpu,
1824                 .teardown.single        = workqueue_offline_cpu,
1825         },
1826         [CPUHP_AP_RANDOM_ONLINE] = {
1827                 .name                   = "random:online",
1828                 .startup.single         = random_online_cpu,
1829                 .teardown.single        = NULL,
1830         },
1831         [CPUHP_AP_RCUTREE_ONLINE] = {
1832                 .name                   = "RCU/tree:online",
1833                 .startup.single         = rcutree_online_cpu,
1834                 .teardown.single        = rcutree_offline_cpu,
1835         },
1836 #endif
1837         /*
1838          * The dynamically registered state space is here
1839          */
1840
1841 #ifdef CONFIG_SMP
1842         /* Last state is scheduler control setting the cpu active */
1843         [CPUHP_AP_ACTIVE] = {
1844                 .name                   = "sched:active",
1845                 .startup.single         = sched_cpu_activate,
1846                 .teardown.single        = sched_cpu_deactivate,
1847         },
1848 #endif
1849
1850         /* CPU is fully up and running. */
1851         [CPUHP_ONLINE] = {
1852                 .name                   = "online",
1853                 .startup.single         = NULL,
1854                 .teardown.single        = NULL,
1855         },
1856 };
1857
1858 /* Sanity check for callbacks */
1859 static int cpuhp_cb_check(enum cpuhp_state state)
1860 {
1861         if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
1862                 return -EINVAL;
1863         return 0;
1864 }
1865
1866 /*
1867  * Returns a free for dynamic slot assignment of the Online state. The states
1868  * are protected by the cpuhp_slot_states mutex and an empty slot is identified
1869  * by having no name assigned.
1870  */
1871 static int cpuhp_reserve_state(enum cpuhp_state state)
1872 {
1873         enum cpuhp_state i, end;
1874         struct cpuhp_step *step;
1875
1876         switch (state) {
1877         case CPUHP_AP_ONLINE_DYN:
1878                 step = cpuhp_hp_states + CPUHP_AP_ONLINE_DYN;
1879                 end = CPUHP_AP_ONLINE_DYN_END;
1880                 break;
1881         case CPUHP_BP_PREPARE_DYN:
1882                 step = cpuhp_hp_states + CPUHP_BP_PREPARE_DYN;
1883                 end = CPUHP_BP_PREPARE_DYN_END;
1884                 break;
1885         default:
1886                 return -EINVAL;
1887         }
1888
1889         for (i = state; i <= end; i++, step++) {
1890                 if (!step->name)
1891                         return i;
1892         }
1893         WARN(1, "No more dynamic states available for CPU hotplug\n");
1894         return -ENOSPC;
1895 }
1896
1897 static int cpuhp_store_callbacks(enum cpuhp_state state, const char *name,
1898                                  int (*startup)(unsigned int cpu),
1899                                  int (*teardown)(unsigned int cpu),
1900                                  bool multi_instance)
1901 {
1902         /* (Un)Install the callbacks for further cpu hotplug operations */
1903         struct cpuhp_step *sp;
1904         int ret = 0;
1905
1906         /*
1907          * If name is NULL, then the state gets removed.
1908          *
1909          * CPUHP_AP_ONLINE_DYN and CPUHP_BP_PREPARE_DYN are handed out on
1910          * the first allocation from these dynamic ranges, so the removal
1911          * would trigger a new allocation and clear the wrong (already
1912          * empty) state, leaving the callbacks of the to be cleared state
1913          * dangling, which causes wreckage on the next hotplug operation.
1914          */
1915         if (name && (state == CPUHP_AP_ONLINE_DYN ||
1916                      state == CPUHP_BP_PREPARE_DYN)) {
1917                 ret = cpuhp_reserve_state(state);
1918                 if (ret < 0)
1919                         return ret;
1920                 state = ret;
1921         }
1922         sp = cpuhp_get_step(state);
1923         if (name && sp->name)
1924                 return -EBUSY;
1925
1926         sp->startup.single = startup;
1927         sp->teardown.single = teardown;
1928         sp->name = name;
1929         sp->multi_instance = multi_instance;
1930         INIT_HLIST_HEAD(&sp->list);
1931         return ret;
1932 }
1933
1934 static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
1935 {
1936         return cpuhp_get_step(state)->teardown.single;
1937 }
1938
1939 /*
1940  * Call the startup/teardown function for a step either on the AP or
1941  * on the current CPU.
1942  */
1943 static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup,
1944                             struct hlist_node *node)
1945 {
1946         struct cpuhp_step *sp = cpuhp_get_step(state);
1947         int ret;
1948
1949         /*
1950          * If there's nothing to do, we done.
1951          * Relies on the union for multi_instance.
1952          */
1953         if (cpuhp_step_empty(bringup, sp))
1954                 return 0;
1955         /*
1956          * The non AP bound callbacks can fail on bringup. On teardown
1957          * e.g. module removal we crash for now.
1958          */
1959 #ifdef CONFIG_SMP
1960         if (cpuhp_is_ap_state(state))
1961                 ret = cpuhp_invoke_ap_callback(cpu, state, bringup, node);
1962         else
1963                 ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1964 #else
1965         ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1966 #endif
1967         BUG_ON(ret && !bringup);
1968         return ret;
1969 }
1970
1971 /*
1972  * Called from __cpuhp_setup_state on a recoverable failure.
1973  *
1974  * Note: The teardown callbacks for rollback are not allowed to fail!
1975  */
1976 static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
1977                                    struct hlist_node *node)
1978 {
1979         int cpu;
1980
1981         /* Roll back the already executed steps on the other cpus */
1982         for_each_present_cpu(cpu) {
1983                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1984                 int cpustate = st->state;
1985
1986                 if (cpu >= failedcpu)
1987                         break;
1988
1989                 /* Did we invoke the startup call on that cpu ? */
1990                 if (cpustate >= state)
1991                         cpuhp_issue_call(cpu, state, false, node);
1992         }
1993 }
1994
1995 int __cpuhp_state_add_instance_cpuslocked(enum cpuhp_state state,
1996                                           struct hlist_node *node,
1997                                           bool invoke)
1998 {
1999         struct cpuhp_step *sp;
2000         int cpu;
2001         int ret;
2002
2003         lockdep_assert_cpus_held();
2004
2005         sp = cpuhp_get_step(state);
2006         if (sp->multi_instance == false)
2007                 return -EINVAL;
2008
2009         mutex_lock(&cpuhp_state_mutex);
2010
2011         if (!invoke || !sp->startup.multi)
2012                 goto add_node;
2013
2014         /*
2015          * Try to call the startup callback for each present cpu
2016          * depending on the hotplug state of the cpu.
2017          */
2018         for_each_present_cpu(cpu) {
2019                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2020                 int cpustate = st->state;
2021
2022                 if (cpustate < state)
2023                         continue;
2024
2025                 ret = cpuhp_issue_call(cpu, state, true, node);
2026                 if (ret) {
2027                         if (sp->teardown.multi)
2028                                 cpuhp_rollback_install(cpu, state, node);
2029                         goto unlock;
2030                 }
2031         }
2032 add_node:
2033         ret = 0;
2034         hlist_add_head(node, &sp->list);
2035 unlock:
2036         mutex_unlock(&cpuhp_state_mutex);
2037         return ret;
2038 }
2039
2040 int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
2041                                bool invoke)
2042 {
2043         int ret;
2044
2045         cpus_read_lock();
2046         ret = __cpuhp_state_add_instance_cpuslocked(state, node, invoke);
2047         cpus_read_unlock();
2048         return ret;
2049 }
2050 EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);
2051
2052 /**
2053  * __cpuhp_setup_state_cpuslocked - Setup the callbacks for an hotplug machine state
2054  * @state:              The state to setup
2055  * @name:               Name of the step
2056  * @invoke:             If true, the startup function is invoked for cpus where
2057  *                      cpu state >= @state
2058  * @startup:            startup callback function
2059  * @teardown:           teardown callback function
2060  * @multi_instance:     State is set up for multiple instances which get
2061  *                      added afterwards.
2062  *
2063  * The caller needs to hold cpus read locked while calling this function.
2064  * Return:
2065  *   On success:
2066  *      Positive state number if @state is CPUHP_AP_ONLINE_DYN;
2067  *      0 for all other states
2068  *   On failure: proper (negative) error code
2069  */
2070 int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state,
2071                                    const char *name, bool invoke,
2072                                    int (*startup)(unsigned int cpu),
2073                                    int (*teardown)(unsigned int cpu),
2074                                    bool multi_instance)
2075 {
2076         int cpu, ret = 0;
2077         bool dynstate;
2078
2079         lockdep_assert_cpus_held();
2080
2081         if (cpuhp_cb_check(state) || !name)
2082                 return -EINVAL;
2083
2084         mutex_lock(&cpuhp_state_mutex);
2085
2086         ret = cpuhp_store_callbacks(state, name, startup, teardown,
2087                                     multi_instance);
2088
2089         dynstate = state == CPUHP_AP_ONLINE_DYN;
2090         if (ret > 0 && dynstate) {
2091                 state = ret;
2092                 ret = 0;
2093         }
2094
2095         if (ret || !invoke || !startup)
2096                 goto out;
2097
2098         /*
2099          * Try to call the startup callback for each present cpu
2100          * depending on the hotplug state of the cpu.
2101          */
2102         for_each_present_cpu(cpu) {
2103                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2104                 int cpustate = st->state;
2105
2106                 if (cpustate < state)
2107                         continue;
2108
2109                 ret = cpuhp_issue_call(cpu, state, true, NULL);
2110                 if (ret) {
2111                         if (teardown)
2112                                 cpuhp_rollback_install(cpu, state, NULL);
2113                         cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
2114                         goto out;
2115                 }
2116         }
2117 out:
2118         mutex_unlock(&cpuhp_state_mutex);
2119         /*
2120          * If the requested state is CPUHP_AP_ONLINE_DYN, return the
2121          * dynamically allocated state in case of success.
2122          */
2123         if (!ret && dynstate)
2124                 return state;
2125         return ret;
2126 }
2127 EXPORT_SYMBOL(__cpuhp_setup_state_cpuslocked);
2128
2129 int __cpuhp_setup_state(enum cpuhp_state state,
2130                         const char *name, bool invoke,
2131                         int (*startup)(unsigned int cpu),
2132                         int (*teardown)(unsigned int cpu),
2133                         bool multi_instance)
2134 {
2135         int ret;
2136
2137         cpus_read_lock();
2138         ret = __cpuhp_setup_state_cpuslocked(state, name, invoke, startup,
2139                                              teardown, multi_instance);
2140         cpus_read_unlock();
2141         return ret;
2142 }
2143 EXPORT_SYMBOL(__cpuhp_setup_state);
2144
2145 int __cpuhp_state_remove_instance(enum cpuhp_state state,
2146                                   struct hlist_node *node, bool invoke)
2147 {
2148         struct cpuhp_step *sp = cpuhp_get_step(state);
2149         int cpu;
2150
2151         BUG_ON(cpuhp_cb_check(state));
2152
2153         if (!sp->multi_instance)
2154                 return -EINVAL;
2155
2156         cpus_read_lock();
2157         mutex_lock(&cpuhp_state_mutex);
2158
2159         if (!invoke || !cpuhp_get_teardown_cb(state))
2160                 goto remove;
2161         /*
2162          * Call the teardown callback for each present cpu depending
2163          * on the hotplug state of the cpu. This function is not
2164          * allowed to fail currently!
2165          */
2166         for_each_present_cpu(cpu) {
2167                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2168                 int cpustate = st->state;
2169
2170                 if (cpustate >= state)
2171                         cpuhp_issue_call(cpu, state, false, node);
2172         }
2173
2174 remove:
2175         hlist_del(node);
2176         mutex_unlock(&cpuhp_state_mutex);
2177         cpus_read_unlock();
2178
2179         return 0;
2180 }
2181 EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance);
2182
2183 /**
2184  * __cpuhp_remove_state_cpuslocked - Remove the callbacks for an hotplug machine state
2185  * @state:      The state to remove
2186  * @invoke:     If true, the teardown function is invoked for cpus where
2187  *              cpu state >= @state
2188  *
2189  * The caller needs to hold cpus read locked while calling this function.
2190  * The teardown callback is currently not allowed to fail. Think
2191  * about module removal!
2192  */
2193 void __cpuhp_remove_state_cpuslocked(enum cpuhp_state state, bool invoke)
2194 {
2195         struct cpuhp_step *sp = cpuhp_get_step(state);
2196         int cpu;
2197
2198         BUG_ON(cpuhp_cb_check(state));
2199
2200         lockdep_assert_cpus_held();
2201
2202         mutex_lock(&cpuhp_state_mutex);
2203         if (sp->multi_instance) {
2204                 WARN(!hlist_empty(&sp->list),
2205                      "Error: Removing state %d which has instances left.\n",
2206                      state);
2207                 goto remove;
2208         }
2209
2210         if (!invoke || !cpuhp_get_teardown_cb(state))
2211                 goto remove;
2212
2213         /*
2214          * Call the teardown callback for each present cpu depending
2215          * on the hotplug state of the cpu. This function is not
2216          * allowed to fail currently!
2217          */
2218         for_each_present_cpu(cpu) {
2219                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2220                 int cpustate = st->state;
2221
2222                 if (cpustate >= state)
2223                         cpuhp_issue_call(cpu, state, false, NULL);
2224         }
2225 remove:
2226         cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
2227         mutex_unlock(&cpuhp_state_mutex);
2228 }
2229 EXPORT_SYMBOL(__cpuhp_remove_state_cpuslocked);
2230
2231 void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
2232 {
2233         cpus_read_lock();
2234         __cpuhp_remove_state_cpuslocked(state, invoke);
2235         cpus_read_unlock();
2236 }
2237 EXPORT_SYMBOL(__cpuhp_remove_state);
2238
2239 #ifdef CONFIG_HOTPLUG_SMT
2240 static void cpuhp_offline_cpu_device(unsigned int cpu)
2241 {
2242         struct device *dev = get_cpu_device(cpu);
2243
2244         dev->offline = true;
2245         /* Tell user space about the state change */
2246         kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
2247 }
2248
2249 static void cpuhp_online_cpu_device(unsigned int cpu)
2250 {
2251         struct device *dev = get_cpu_device(cpu);
2252
2253         dev->offline = false;
2254         /* Tell user space about the state change */
2255         kobject_uevent(&dev->kobj, KOBJ_ONLINE);
2256 }
2257
2258 int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
2259 {
2260         int cpu, ret = 0;
2261
2262         cpu_maps_update_begin();
2263         for_each_online_cpu(cpu) {
2264                 if (topology_is_primary_thread(cpu))
2265                         continue;
2266                 ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
2267                 if (ret)
2268                         break;
2269                 /*
2270                  * As this needs to hold the cpu maps lock it's impossible
2271                  * to call device_offline() because that ends up calling
2272                  * cpu_down() which takes cpu maps lock. cpu maps lock
2273                  * needs to be held as this might race against in kernel
2274                  * abusers of the hotplug machinery (thermal management).
2275                  *
2276                  * So nothing would update device:offline state. That would
2277                  * leave the sysfs entry stale and prevent onlining after
2278                  * smt control has been changed to 'off' again. This is
2279                  * called under the sysfs hotplug lock, so it is properly
2280                  * serialized against the regular offline usage.
2281                  */
2282                 cpuhp_offline_cpu_device(cpu);
2283         }
2284         if (!ret)
2285                 cpu_smt_control = ctrlval;
2286         cpu_maps_update_done();
2287         return ret;
2288 }
2289
2290 int cpuhp_smt_enable(void)
2291 {
2292         int cpu, ret = 0;
2293
2294         cpu_maps_update_begin();
2295         cpu_smt_control = CPU_SMT_ENABLED;
2296         for_each_present_cpu(cpu) {
2297                 /* Skip online CPUs and CPUs on offline nodes */
2298                 if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))
2299                         continue;
2300                 ret = _cpu_up(cpu, 0, CPUHP_ONLINE);
2301                 if (ret)
2302                         break;
2303                 /* See comment in cpuhp_smt_disable() */
2304                 cpuhp_online_cpu_device(cpu);
2305         }
2306         cpu_maps_update_done();
2307         return ret;
2308 }
2309 #endif
2310
2311 #if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
2312 static ssize_t state_show(struct device *dev,
2313                           struct device_attribute *attr, char *buf)
2314 {
2315         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2316
2317         return sprintf(buf, "%d\n", st->state);
2318 }
2319 static DEVICE_ATTR_RO(state);
2320
2321 static ssize_t target_store(struct device *dev, struct device_attribute *attr,
2322                             const char *buf, size_t count)
2323 {
2324         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2325         struct cpuhp_step *sp;
2326         int target, ret;
2327
2328         ret = kstrtoint(buf, 10, &target);
2329         if (ret)
2330                 return ret;
2331
2332 #ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
2333         if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
2334                 return -EINVAL;
2335 #else
2336         if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
2337                 return -EINVAL;
2338 #endif
2339
2340         ret = lock_device_hotplug_sysfs();
2341         if (ret)
2342                 return ret;
2343
2344         mutex_lock(&cpuhp_state_mutex);
2345         sp = cpuhp_get_step(target);
2346         ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
2347         mutex_unlock(&cpuhp_state_mutex);
2348         if (ret)
2349                 goto out;
2350
2351         if (st->state < target)
2352                 ret = cpu_up(dev->id, target);
2353         else if (st->state > target)
2354                 ret = cpu_down(dev->id, target);
2355         else if (WARN_ON(st->target != target))
2356                 st->target = target;
2357 out:
2358         unlock_device_hotplug();
2359         return ret ? ret : count;
2360 }
2361
2362 static ssize_t target_show(struct device *dev,
2363                            struct device_attribute *attr, char *buf)
2364 {
2365         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2366
2367         return sprintf(buf, "%d\n", st->target);
2368 }
2369 static DEVICE_ATTR_RW(target);
2370
2371 static ssize_t fail_store(struct device *dev, struct device_attribute *attr,
2372                           const char *buf, size_t count)
2373 {
2374         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2375         struct cpuhp_step *sp;
2376         int fail, ret;
2377
2378         ret = kstrtoint(buf, 10, &fail);
2379         if (ret)
2380                 return ret;
2381
2382         if (fail == CPUHP_INVALID) {
2383                 st->fail = fail;
2384                 return count;
2385         }
2386
2387         if (fail < CPUHP_OFFLINE || fail > CPUHP_ONLINE)
2388                 return -EINVAL;
2389
2390         /*
2391          * Cannot fail STARTING/DYING callbacks.
2392          */
2393         if (cpuhp_is_atomic_state(fail))
2394                 return -EINVAL;
2395
2396         /*
2397          * DEAD callbacks cannot fail...
2398          * ... neither can CPUHP_BRINGUP_CPU during hotunplug. The latter
2399          * triggering STARTING callbacks, a failure in this state would
2400          * hinder rollback.
2401          */
2402         if (fail <= CPUHP_BRINGUP_CPU && st->state > CPUHP_BRINGUP_CPU)
2403                 return -EINVAL;
2404
2405         /*
2406          * Cannot fail anything that doesn't have callbacks.
2407          */
2408         mutex_lock(&cpuhp_state_mutex);
2409         sp = cpuhp_get_step(fail);
2410         if (!sp->startup.single && !sp->teardown.single)
2411                 ret = -EINVAL;
2412         mutex_unlock(&cpuhp_state_mutex);
2413         if (ret)
2414                 return ret;
2415
2416         st->fail = fail;
2417
2418         return count;
2419 }
2420
2421 static ssize_t fail_show(struct device *dev,
2422                          struct device_attribute *attr, char *buf)
2423 {
2424         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2425
2426         return sprintf(buf, "%d\n", st->fail);
2427 }
2428
2429 static DEVICE_ATTR_RW(fail);
2430
2431 static struct attribute *cpuhp_cpu_attrs[] = {
2432         &dev_attr_state.attr,
2433         &dev_attr_target.attr,
2434         &dev_attr_fail.attr,
2435         NULL
2436 };
2437
2438 static const struct attribute_group cpuhp_cpu_attr_group = {
2439         .attrs = cpuhp_cpu_attrs,
2440         .name = "hotplug",
2441         NULL
2442 };
2443
2444 static ssize_t states_show(struct device *dev,
2445                                  struct device_attribute *attr, char *buf)
2446 {
2447         ssize_t cur, res = 0;
2448         int i;
2449
2450         mutex_lock(&cpuhp_state_mutex);
2451         for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
2452                 struct cpuhp_step *sp = cpuhp_get_step(i);
2453
2454                 if (sp->name) {
2455                         cur = sprintf(buf, "%3d: %s\n", i, sp->name);
2456                         buf += cur;
2457                         res += cur;
2458                 }
2459         }
2460         mutex_unlock(&cpuhp_state_mutex);
2461         return res;
2462 }
2463 static DEVICE_ATTR_RO(states);
2464
2465 static struct attribute *cpuhp_cpu_root_attrs[] = {
2466         &dev_attr_states.attr,
2467         NULL
2468 };
2469
2470 static const struct attribute_group cpuhp_cpu_root_attr_group = {
2471         .attrs = cpuhp_cpu_root_attrs,
2472         .name = "hotplug",
2473         NULL
2474 };
2475
2476 #ifdef CONFIG_HOTPLUG_SMT
2477
2478 static ssize_t
2479 __store_smt_control(struct device *dev, struct device_attribute *attr,
2480                     const char *buf, size_t count)
2481 {
2482         int ctrlval, ret;
2483
2484         if (sysfs_streq(buf, "on"))
2485                 ctrlval = CPU_SMT_ENABLED;
2486         else if (sysfs_streq(buf, "off"))
2487                 ctrlval = CPU_SMT_DISABLED;
2488         else if (sysfs_streq(buf, "forceoff"))
2489                 ctrlval = CPU_SMT_FORCE_DISABLED;
2490         else
2491                 return -EINVAL;
2492
2493         if (cpu_smt_control == CPU_SMT_FORCE_DISABLED)
2494                 return -EPERM;
2495
2496         if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
2497                 return -ENODEV;
2498
2499         ret = lock_device_hotplug_sysfs();
2500         if (ret)
2501                 return ret;
2502
2503         if (ctrlval != cpu_smt_control) {
2504                 switch (ctrlval) {
2505                 case CPU_SMT_ENABLED:
2506                         ret = cpuhp_smt_enable();
2507                         break;
2508                 case CPU_SMT_DISABLED:
2509                 case CPU_SMT_FORCE_DISABLED:
2510                         ret = cpuhp_smt_disable(ctrlval);
2511                         break;
2512                 }
2513         }
2514
2515         unlock_device_hotplug();
2516         return ret ? ret : count;
2517 }
2518
2519 #else /* !CONFIG_HOTPLUG_SMT */
2520 static ssize_t
2521 __store_smt_control(struct device *dev, struct device_attribute *attr,
2522                     const char *buf, size_t count)
2523 {
2524         return -ENODEV;
2525 }
2526 #endif /* CONFIG_HOTPLUG_SMT */
2527
2528 static const char *smt_states[] = {
2529         [CPU_SMT_ENABLED]               = "on",
2530         [CPU_SMT_DISABLED]              = "off",
2531         [CPU_SMT_FORCE_DISABLED]        = "forceoff",
2532         [CPU_SMT_NOT_SUPPORTED]         = "notsupported",
2533         [CPU_SMT_NOT_IMPLEMENTED]       = "notimplemented",
2534 };
2535
2536 static ssize_t control_show(struct device *dev,
2537                             struct device_attribute *attr, char *buf)
2538 {
2539         const char *state = smt_states[cpu_smt_control];
2540
2541         return snprintf(buf, PAGE_SIZE - 2, "%s\n", state);
2542 }
2543
2544 static ssize_t control_store(struct device *dev, struct device_attribute *attr,
2545                              const char *buf, size_t count)
2546 {
2547         return __store_smt_control(dev, attr, buf, count);
2548 }
2549 static DEVICE_ATTR_RW(control);
2550
2551 static ssize_t active_show(struct device *dev,
2552                            struct device_attribute *attr, char *buf)
2553 {
2554         return snprintf(buf, PAGE_SIZE - 2, "%d\n", sched_smt_active());
2555 }
2556 static DEVICE_ATTR_RO(active);
2557
2558 static struct attribute *cpuhp_smt_attrs[] = {
2559         &dev_attr_control.attr,
2560         &dev_attr_active.attr,
2561         NULL
2562 };
2563
2564 static const struct attribute_group cpuhp_smt_attr_group = {
2565         .attrs = cpuhp_smt_attrs,
2566         .name = "smt",
2567         NULL
2568 };
2569
2570 static int __init cpu_smt_sysfs_init(void)
2571 {
2572         struct device *dev_root;
2573         int ret = -ENODEV;
2574
2575         dev_root = bus_get_dev_root(&cpu_subsys);
2576         if (dev_root) {
2577                 ret = sysfs_create_group(&dev_root->kobj, &cpuhp_smt_attr_group);
2578                 put_device(dev_root);
2579         }
2580         return ret;
2581 }
2582
2583 static int __init cpuhp_sysfs_init(void)
2584 {
2585         struct device *dev_root;
2586         int cpu, ret;
2587
2588         ret = cpu_smt_sysfs_init();
2589         if (ret)
2590                 return ret;
2591
2592         dev_root = bus_get_dev_root(&cpu_subsys);
2593         if (dev_root) {
2594                 ret = sysfs_create_group(&dev_root->kobj, &cpuhp_cpu_root_attr_group);
2595                 put_device(dev_root);
2596                 if (ret)
2597                         return ret;
2598         }
2599
2600         for_each_possible_cpu(cpu) {
2601                 struct device *dev = get_cpu_device(cpu);
2602
2603                 if (!dev)
2604                         continue;
2605                 ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
2606                 if (ret)
2607                         return ret;
2608         }
2609         return 0;
2610 }
2611 device_initcall(cpuhp_sysfs_init);
2612 #endif /* CONFIG_SYSFS && CONFIG_HOTPLUG_CPU */
2613
2614 /*
2615  * cpu_bit_bitmap[] is a special, "compressed" data structure that
2616  * represents all NR_CPUS bits binary values of 1<<nr.
2617  *
2618  * It is used by cpumask_of() to get a constant address to a CPU
2619  * mask value that has a single bit set only.
2620  */
2621
2622 /* cpu_bit_bitmap[0] is empty - so we can back into it */
2623 #define MASK_DECLARE_1(x)       [x+1][0] = (1UL << (x))
2624 #define MASK_DECLARE_2(x)       MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
2625 #define MASK_DECLARE_4(x)       MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
2626 #define MASK_DECLARE_8(x)       MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
2627
2628 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
2629
2630         MASK_DECLARE_8(0),      MASK_DECLARE_8(8),
2631         MASK_DECLARE_8(16),     MASK_DECLARE_8(24),
2632 #if BITS_PER_LONG > 32
2633         MASK_DECLARE_8(32),     MASK_DECLARE_8(40),
2634         MASK_DECLARE_8(48),     MASK_DECLARE_8(56),
2635 #endif
2636 };
2637 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
2638
2639 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
2640 EXPORT_SYMBOL(cpu_all_bits);
2641
2642 #ifdef CONFIG_INIT_ALL_POSSIBLE
2643 struct cpumask __cpu_possible_mask __read_mostly
2644         = {CPU_BITS_ALL};
2645 #else
2646 struct cpumask __cpu_possible_mask __read_mostly;
2647 #endif
2648 EXPORT_SYMBOL(__cpu_possible_mask);
2649
2650 struct cpumask __cpu_online_mask __read_mostly;
2651 EXPORT_SYMBOL(__cpu_online_mask);
2652
2653 struct cpumask __cpu_present_mask __read_mostly;
2654 EXPORT_SYMBOL(__cpu_present_mask);
2655
2656 struct cpumask __cpu_active_mask __read_mostly;
2657 EXPORT_SYMBOL(__cpu_active_mask);
2658
2659 struct cpumask __cpu_dying_mask __read_mostly;
2660 EXPORT_SYMBOL(__cpu_dying_mask);
2661
2662 atomic_t __num_online_cpus __read_mostly;
2663 EXPORT_SYMBOL(__num_online_cpus);
2664
2665 void init_cpu_present(const struct cpumask *src)
2666 {
2667         cpumask_copy(&__cpu_present_mask, src);
2668 }
2669
2670 void init_cpu_possible(const struct cpumask *src)
2671 {
2672         cpumask_copy(&__cpu_possible_mask, src);
2673 }
2674
2675 void init_cpu_online(const struct cpumask *src)
2676 {
2677         cpumask_copy(&__cpu_online_mask, src);
2678 }
2679
2680 void set_cpu_online(unsigned int cpu, bool online)
2681 {
2682         /*
2683          * atomic_inc/dec() is required to handle the horrid abuse of this
2684          * function by the reboot and kexec code which invoke it from
2685          * IPI/NMI broadcasts when shutting down CPUs. Invocation from
2686          * regular CPU hotplug is properly serialized.
2687          *
2688          * Note, that the fact that __num_online_cpus is of type atomic_t
2689          * does not protect readers which are not serialized against
2690          * concurrent hotplug operations.
2691          */
2692         if (online) {
2693                 if (!cpumask_test_and_set_cpu(cpu, &__cpu_online_mask))
2694                         atomic_inc(&__num_online_cpus);
2695         } else {
2696                 if (cpumask_test_and_clear_cpu(cpu, &__cpu_online_mask))
2697                         atomic_dec(&__num_online_cpus);
2698         }
2699 }
2700
2701 /*
2702  * Activate the first processor.
2703  */
2704 void __init boot_cpu_init(void)
2705 {
2706         int cpu = smp_processor_id();
2707
2708         /* Mark the boot cpu "present", "online" etc for SMP and UP case */
2709         set_cpu_online(cpu, true);
2710         set_cpu_active(cpu, true);
2711         set_cpu_present(cpu, true);
2712         set_cpu_possible(cpu, true);
2713
2714 #ifdef CONFIG_SMP
2715         __boot_cpu_id = cpu;
2716 #endif
2717 }
2718
2719 /*
2720  * Must be called _AFTER_ setting up the per_cpu areas
2721  */
2722 void __init boot_cpu_hotplug_init(void)
2723 {
2724 #ifdef CONFIG_SMP
2725         cpumask_set_cpu(smp_processor_id(), &cpus_booted_once_mask);
2726 #endif
2727         this_cpu_write(cpuhp_state.state, CPUHP_ONLINE);
2728         this_cpu_write(cpuhp_state.target, CPUHP_ONLINE);
2729 }
2730
2731 /*
2732  * These are used for a global "mitigations=" cmdline option for toggling
2733  * optional CPU mitigations.
2734  */
2735 enum cpu_mitigations {
2736         CPU_MITIGATIONS_OFF,
2737         CPU_MITIGATIONS_AUTO,
2738         CPU_MITIGATIONS_AUTO_NOSMT,
2739 };
2740
2741 static enum cpu_mitigations cpu_mitigations __ro_after_init =
2742         CPU_MITIGATIONS_AUTO;
2743
2744 static int __init mitigations_parse_cmdline(char *arg)
2745 {
2746         if (!strcmp(arg, "off"))
2747                 cpu_mitigations = CPU_MITIGATIONS_OFF;
2748         else if (!strcmp(arg, "auto"))
2749                 cpu_mitigations = CPU_MITIGATIONS_AUTO;
2750         else if (!strcmp(arg, "auto,nosmt"))
2751                 cpu_mitigations = CPU_MITIGATIONS_AUTO_NOSMT;
2752         else
2753                 pr_crit("Unsupported mitigations=%s, system may still be vulnerable\n",
2754                         arg);
2755
2756         return 0;
2757 }
2758 early_param("mitigations", mitigations_parse_cmdline);
2759
2760 /* mitigations=off */
2761 bool cpu_mitigations_off(void)
2762 {
2763         return cpu_mitigations == CPU_MITIGATIONS_OFF;
2764 }
2765 EXPORT_SYMBOL_GPL(cpu_mitigations_off);
2766
2767 /* mitigations=auto,nosmt */
2768 bool cpu_mitigations_auto_nosmt(void)
2769 {
2770         return cpu_mitigations == CPU_MITIGATIONS_AUTO_NOSMT;
2771 }
2772 EXPORT_SYMBOL_GPL(cpu_mitigations_auto_nosmt);