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/delay.h>
21 #include <linux/export.h>
22 #include <linux/bug.h>
23 #include <linux/kthread.h>
24 #include <linux/stop_machine.h>
25 #include <linux/mutex.h>
26 #include <linux/gfp.h>
27 #include <linux/suspend.h>
28 #include <linux/lockdep.h>
29 #include <linux/tick.h>
30 #include <linux/irq.h>
31 #include <linux/nmi.h>
32 #include <linux/smpboot.h>
33 #include <linux/relay.h>
34 #include <linux/slab.h>
35 #include <linux/scs.h>
36 #include <linux/percpu-rwsem.h>
37 #include <linux/cpuset.h>
38 #include <linux/random.h>
39 #include <linux/cc_platform.h>
40
41 #include <trace/events/power.h>
42 #define CREATE_TRACE_POINTS
43 #include <trace/events/cpuhp.h>
44
45 #include "smpboot.h"
46
47 /**
48 * struct cpuhp_cpu_state - Per cpu hotplug state storage
49 * @state: The current cpu state
50 * @target: The target state
51 * @fail: Current CPU hotplug callback state
52 * @thread: Pointer to the hotplug thread
53 * @should_run: Thread should execute
54 * @rollback: Perform a rollback
55 * @single: Single callback invocation
56 * @bringup: Single callback bringup or teardown selector
57 * @cpu: CPU number
58 * @node: Remote CPU node; for multi-instance, do a
59 * single entry callback for install/remove
60 * @last: For multi-instance rollback, remember how far we got
61 * @cb_state: The state for a single callback (install/uninstall)
62 * @result: Result of the operation
63 * @ap_sync_state: State for AP synchronization
64 * @done_up: Signal completion to the issuer of the task for cpu-up
65 * @done_down: Signal completion to the issuer of the task for cpu-down
66 */
67 struct cpuhp_cpu_state {
68 enum cpuhp_state state;
69 enum cpuhp_state target;
70 enum cpuhp_state fail;
71 #ifdef CONFIG_SMP
72 struct task_struct *thread;
73 bool should_run;
74 bool rollback;
75 bool single;
76 bool bringup;
77 struct hlist_node *node;
78 struct hlist_node *last;
79 enum cpuhp_state cb_state;
80 int result;
81 atomic_t ap_sync_state;
82 struct completion done_up;
83 struct completion done_down;
84 #endif
85 };
86
87 static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state) = {
88 .fail = CPUHP_INVALID,
89 };
90
91 #ifdef CONFIG_SMP
92 cpumask_t cpus_booted_once_mask;
93 #endif
94
95 #if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP)
96 static struct lockdep_map cpuhp_state_up_map =
97 STATIC_LOCKDEP_MAP_INIT("cpuhp_state-up", &cpuhp_state_up_map);
98 static struct lockdep_map cpuhp_state_down_map =
99 STATIC_LOCKDEP_MAP_INIT("cpuhp_state-down", &cpuhp_state_down_map);
100
101
cpuhp_lock_acquire(bool bringup)102 static inline void cpuhp_lock_acquire(bool bringup)
103 {
104 lock_map_acquire(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
105 }
106
cpuhp_lock_release(bool bringup)107 static inline void cpuhp_lock_release(bool bringup)
108 {
109 lock_map_release(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
110 }
111 #else
112
cpuhp_lock_acquire(bool bringup)113 static inline void cpuhp_lock_acquire(bool bringup) { }
cpuhp_lock_release(bool bringup)114 static inline void cpuhp_lock_release(bool bringup) { }
115
116 #endif
117
118 /**
119 * struct cpuhp_step - Hotplug state machine step
120 * @name: Name of the step
121 * @startup: Startup function of the step
122 * @teardown: Teardown function of the step
123 * @cant_stop: Bringup/teardown can't be stopped at this step
124 * @multi_instance: State has multiple instances which get added afterwards
125 */
126 struct cpuhp_step {
127 const char *name;
128 union {
129 int (*single)(unsigned int cpu);
130 int (*multi)(unsigned int cpu,
131 struct hlist_node *node);
132 } startup;
133 union {
134 int (*single)(unsigned int cpu);
135 int (*multi)(unsigned int cpu,
136 struct hlist_node *node);
137 } teardown;
138 /* private: */
139 struct hlist_head list;
140 /* public: */
141 bool cant_stop;
142 bool multi_instance;
143 };
144
145 static DEFINE_MUTEX(cpuhp_state_mutex);
146 static struct cpuhp_step cpuhp_hp_states[];
147
cpuhp_get_step(enum cpuhp_state state)148 static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
149 {
150 return cpuhp_hp_states + state;
151 }
152
cpuhp_step_empty(bool bringup,struct cpuhp_step * step)153 static bool cpuhp_step_empty(bool bringup, struct cpuhp_step *step)
154 {
155 return bringup ? !step->startup.single : !step->teardown.single;
156 }
157
158 /**
159 * cpuhp_invoke_callback - Invoke the callbacks for a given state
160 * @cpu: The cpu for which the callback should be invoked
161 * @state: The state to do callbacks for
162 * @bringup: True if the bringup callback should be invoked
163 * @node: For multi-instance, do a single entry callback for install/remove
164 * @lastp: For multi-instance rollback, remember how far we got
165 *
166 * Called from cpu hotplug and from the state register machinery.
167 *
168 * Return: %0 on success or a negative errno code
169 */
cpuhp_invoke_callback(unsigned int cpu,enum cpuhp_state state,bool bringup,struct hlist_node * node,struct hlist_node ** lastp)170 static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state,
171 bool bringup, struct hlist_node *node,
172 struct hlist_node **lastp)
173 {
174 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
175 struct cpuhp_step *step = cpuhp_get_step(state);
176 int (*cbm)(unsigned int cpu, struct hlist_node *node);
177 int (*cb)(unsigned int cpu);
178 int ret, cnt;
179
180 if (st->fail == state) {
181 st->fail = CPUHP_INVALID;
182 return -EAGAIN;
183 }
184
185 if (cpuhp_step_empty(bringup, step)) {
186 WARN_ON_ONCE(1);
187 return 0;
188 }
189
190 if (!step->multi_instance) {
191 WARN_ON_ONCE(lastp && *lastp);
192 cb = bringup ? step->startup.single : step->teardown.single;
193
194 trace_cpuhp_enter(cpu, st->target, state, cb);
195 ret = cb(cpu);
196 trace_cpuhp_exit(cpu, st->state, state, ret);
197 return ret;
198 }
199 cbm = bringup ? step->startup.multi : step->teardown.multi;
200
201 /* Single invocation for instance add/remove */
202 if (node) {
203 WARN_ON_ONCE(lastp && *lastp);
204 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
205 ret = cbm(cpu, node);
206 trace_cpuhp_exit(cpu, st->state, state, ret);
207 return ret;
208 }
209
210 /* State transition. Invoke on all instances */
211 cnt = 0;
212 hlist_for_each(node, &step->list) {
213 if (lastp && node == *lastp)
214 break;
215
216 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
217 ret = cbm(cpu, node);
218 trace_cpuhp_exit(cpu, st->state, state, ret);
219 if (ret) {
220 if (!lastp)
221 goto err;
222
223 *lastp = node;
224 return ret;
225 }
226 cnt++;
227 }
228 if (lastp)
229 *lastp = NULL;
230 return 0;
231 err:
232 /* Rollback the instances if one failed */
233 cbm = !bringup ? step->startup.multi : step->teardown.multi;
234 if (!cbm)
235 return ret;
236
237 hlist_for_each(node, &step->list) {
238 if (!cnt--)
239 break;
240
241 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
242 ret = cbm(cpu, node);
243 trace_cpuhp_exit(cpu, st->state, state, ret);
244 /*
245 * Rollback must not fail,
246 */
247 WARN_ON_ONCE(ret);
248 }
249 return ret;
250 }
251
252 #ifdef CONFIG_SMP
cpuhp_is_ap_state(enum cpuhp_state state)253 static bool cpuhp_is_ap_state(enum cpuhp_state state)
254 {
255 /*
256 * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
257 * purposes as that state is handled explicitly in cpu_down.
258 */
259 return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;
260 }
261
wait_for_ap_thread(struct cpuhp_cpu_state * st,bool bringup)262 static inline void wait_for_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
263 {
264 struct completion *done = bringup ? &st->done_up : &st->done_down;
265 wait_for_completion(done);
266 }
267
complete_ap_thread(struct cpuhp_cpu_state * st,bool bringup)268 static inline void complete_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
269 {
270 struct completion *done = bringup ? &st->done_up : &st->done_down;
271 complete(done);
272 }
273
274 /*
275 * The former STARTING/DYING states, ran with IRQs disabled and must not fail.
276 */
cpuhp_is_atomic_state(enum cpuhp_state state)277 static bool cpuhp_is_atomic_state(enum cpuhp_state state)
278 {
279 return CPUHP_AP_IDLE_DEAD <= state && state < CPUHP_AP_ONLINE;
280 }
281
282 /* Synchronization state management */
283 enum cpuhp_sync_state {
284 SYNC_STATE_DEAD,
285 SYNC_STATE_KICKED,
286 SYNC_STATE_SHOULD_DIE,
287 SYNC_STATE_ALIVE,
288 SYNC_STATE_SHOULD_ONLINE,
289 SYNC_STATE_ONLINE,
290 };
291
292 #ifdef CONFIG_HOTPLUG_CORE_SYNC
293 /**
294 * cpuhp_ap_update_sync_state - Update synchronization state during bringup/teardown
295 * @state: The synchronization state to set
296 *
297 * No synchronization point. Just update of the synchronization state, but implies
298 * a full barrier so that the AP changes are visible before the control CPU proceeds.
299 */
cpuhp_ap_update_sync_state(enum cpuhp_sync_state state)300 static inline void cpuhp_ap_update_sync_state(enum cpuhp_sync_state state)
301 {
302 atomic_t *st = this_cpu_ptr(&cpuhp_state.ap_sync_state);
303
304 (void)atomic_xchg(st, state);
305 }
306
arch_cpuhp_sync_state_poll(void)307 void __weak arch_cpuhp_sync_state_poll(void) { cpu_relax(); }
308
cpuhp_wait_for_sync_state(unsigned int cpu,enum cpuhp_sync_state state,enum cpuhp_sync_state next_state)309 static bool cpuhp_wait_for_sync_state(unsigned int cpu, enum cpuhp_sync_state state,
310 enum cpuhp_sync_state next_state)
311 {
312 atomic_t *st = per_cpu_ptr(&cpuhp_state.ap_sync_state, cpu);
313 ktime_t now, end, start = ktime_get();
314 int sync;
315
316 end = start + 10ULL * NSEC_PER_SEC;
317
318 sync = atomic_read(st);
319 while (1) {
320 if (sync == state) {
321 if (!atomic_try_cmpxchg(st, &sync, next_state))
322 continue;
323 return true;
324 }
325
326 now = ktime_get();
327 if (now > end) {
328 /* Timeout. Leave the state unchanged */
329 return false;
330 } else if (now - start < NSEC_PER_MSEC) {
331 /* Poll for one millisecond */
332 arch_cpuhp_sync_state_poll();
333 } else {
334 usleep_range_state(USEC_PER_MSEC, 2 * USEC_PER_MSEC, TASK_UNINTERRUPTIBLE);
335 }
336 sync = atomic_read(st);
337 }
338 return true;
339 }
340 #else /* CONFIG_HOTPLUG_CORE_SYNC */
cpuhp_ap_update_sync_state(enum cpuhp_sync_state state)341 static inline void cpuhp_ap_update_sync_state(enum cpuhp_sync_state state) { }
342 #endif /* !CONFIG_HOTPLUG_CORE_SYNC */
343
344 #ifdef CONFIG_HOTPLUG_CORE_SYNC_DEAD
345 /**
346 * cpuhp_ap_report_dead - Update synchronization state to DEAD
347 *
348 * No synchronization point. Just update of the synchronization state.
349 */
cpuhp_ap_report_dead(void)350 void cpuhp_ap_report_dead(void)
351 {
352 cpuhp_ap_update_sync_state(SYNC_STATE_DEAD);
353 }
354
arch_cpuhp_cleanup_dead_cpu(unsigned int cpu)355 void __weak arch_cpuhp_cleanup_dead_cpu(unsigned int cpu) { }
356
357 /*
358 * Late CPU shutdown synchronization point. Cannot use cpuhp_state::done_down
359 * because the AP cannot issue complete() at this stage.
360 */
cpuhp_bp_sync_dead(unsigned int cpu)361 static void cpuhp_bp_sync_dead(unsigned int cpu)
362 {
363 atomic_t *st = per_cpu_ptr(&cpuhp_state.ap_sync_state, cpu);
364 int sync = atomic_read(st);
365
366 do {
367 /* CPU can have reported dead already. Don't overwrite that! */
368 if (sync == SYNC_STATE_DEAD)
369 break;
370 } while (!atomic_try_cmpxchg(st, &sync, SYNC_STATE_SHOULD_DIE));
371
372 if (cpuhp_wait_for_sync_state(cpu, SYNC_STATE_DEAD, SYNC_STATE_DEAD)) {
373 /* CPU reached dead state. Invoke the cleanup function */
374 arch_cpuhp_cleanup_dead_cpu(cpu);
375 return;
376 }
377
378 /* No further action possible. Emit message and give up. */
379 pr_err("CPU%u failed to report dead state\n", cpu);
380 }
381 #else /* CONFIG_HOTPLUG_CORE_SYNC_DEAD */
cpuhp_bp_sync_dead(unsigned int cpu)382 static inline void cpuhp_bp_sync_dead(unsigned int cpu) { }
383 #endif /* !CONFIG_HOTPLUG_CORE_SYNC_DEAD */
384
385 #ifdef CONFIG_HOTPLUG_CORE_SYNC_FULL
386 /**
387 * cpuhp_ap_sync_alive - Synchronize AP with the control CPU once it is alive
388 *
389 * Updates the AP synchronization state to SYNC_STATE_ALIVE and waits
390 * for the BP to release it.
391 */
cpuhp_ap_sync_alive(void)392 void cpuhp_ap_sync_alive(void)
393 {
394 atomic_t *st = this_cpu_ptr(&cpuhp_state.ap_sync_state);
395
396 cpuhp_ap_update_sync_state(SYNC_STATE_ALIVE);
397
398 /* Wait for the control CPU to release it. */
399 while (atomic_read(st) != SYNC_STATE_SHOULD_ONLINE)
400 cpu_relax();
401 }
402
cpuhp_can_boot_ap(unsigned int cpu)403 static bool cpuhp_can_boot_ap(unsigned int cpu)
404 {
405 atomic_t *st = per_cpu_ptr(&cpuhp_state.ap_sync_state, cpu);
406 int sync = atomic_read(st);
407
408 again:
409 switch (sync) {
410 case SYNC_STATE_DEAD:
411 /* CPU is properly dead */
412 break;
413 case SYNC_STATE_KICKED:
414 /* CPU did not come up in previous attempt */
415 break;
416 case SYNC_STATE_ALIVE:
417 /* CPU is stuck cpuhp_ap_sync_alive(). */
418 break;
419 default:
420 /* CPU failed to report online or dead and is in limbo state. */
421 return false;
422 }
423
424 /* Prepare for booting */
425 if (!atomic_try_cmpxchg(st, &sync, SYNC_STATE_KICKED))
426 goto again;
427
428 return true;
429 }
430
arch_cpuhp_cleanup_kick_cpu(unsigned int cpu)431 void __weak arch_cpuhp_cleanup_kick_cpu(unsigned int cpu) { }
432
433 /*
434 * Early CPU bringup synchronization point. Cannot use cpuhp_state::done_up
435 * because the AP cannot issue complete() so early in the bringup.
436 */
cpuhp_bp_sync_alive(unsigned int cpu)437 static int cpuhp_bp_sync_alive(unsigned int cpu)
438 {
439 int ret = 0;
440
441 if (!IS_ENABLED(CONFIG_HOTPLUG_CORE_SYNC_FULL))
442 return 0;
443
444 if (!cpuhp_wait_for_sync_state(cpu, SYNC_STATE_ALIVE, SYNC_STATE_SHOULD_ONLINE)) {
445 pr_err("CPU%u failed to report alive state\n", cpu);
446 ret = -EIO;
447 }
448
449 /* Let the architecture cleanup the kick alive mechanics. */
450 arch_cpuhp_cleanup_kick_cpu(cpu);
451 return ret;
452 }
453 #else /* CONFIG_HOTPLUG_CORE_SYNC_FULL */
cpuhp_bp_sync_alive(unsigned int cpu)454 static inline int cpuhp_bp_sync_alive(unsigned int cpu) { return 0; }
cpuhp_can_boot_ap(unsigned int cpu)455 static inline bool cpuhp_can_boot_ap(unsigned int cpu) { return true; }
456 #endif /* !CONFIG_HOTPLUG_CORE_SYNC_FULL */
457
458 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
459 static DEFINE_MUTEX(cpu_add_remove_lock);
460 bool cpuhp_tasks_frozen;
461 EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
462
463 /*
464 * The following two APIs (cpu_maps_update_begin/done) must be used when
465 * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
466 */
cpu_maps_update_begin(void)467 void cpu_maps_update_begin(void)
468 {
469 mutex_lock(&cpu_add_remove_lock);
470 }
471
cpu_maps_update_done(void)472 void cpu_maps_update_done(void)
473 {
474 mutex_unlock(&cpu_add_remove_lock);
475 }
476
477 /*
478 * If set, cpu_up and cpu_down will return -EBUSY and do nothing.
479 * Should always be manipulated under cpu_add_remove_lock
480 */
481 static int cpu_hotplug_disabled;
482
483 #ifdef CONFIG_HOTPLUG_CPU
484
485 DEFINE_STATIC_PERCPU_RWSEM(cpu_hotplug_lock);
486
cpus_read_lock(void)487 void cpus_read_lock(void)
488 {
489 percpu_down_read(&cpu_hotplug_lock);
490 }
491 EXPORT_SYMBOL_GPL(cpus_read_lock);
492
cpus_read_trylock(void)493 int cpus_read_trylock(void)
494 {
495 return percpu_down_read_trylock(&cpu_hotplug_lock);
496 }
497 EXPORT_SYMBOL_GPL(cpus_read_trylock);
498
cpus_read_unlock(void)499 void cpus_read_unlock(void)
500 {
501 percpu_up_read(&cpu_hotplug_lock);
502 }
503 EXPORT_SYMBOL_GPL(cpus_read_unlock);
504
cpus_write_lock(void)505 void cpus_write_lock(void)
506 {
507 percpu_down_write(&cpu_hotplug_lock);
508 }
509
cpus_write_unlock(void)510 void cpus_write_unlock(void)
511 {
512 percpu_up_write(&cpu_hotplug_lock);
513 }
514
lockdep_assert_cpus_held(void)515 void lockdep_assert_cpus_held(void)
516 {
517 /*
518 * We can't have hotplug operations before userspace starts running,
519 * and some init codepaths will knowingly not take the hotplug lock.
520 * This is all valid, so mute lockdep until it makes sense to report
521 * unheld locks.
522 */
523 if (system_state < SYSTEM_RUNNING)
524 return;
525
526 percpu_rwsem_assert_held(&cpu_hotplug_lock);
527 }
528
529 #ifdef CONFIG_LOCKDEP
lockdep_is_cpus_held(void)530 int lockdep_is_cpus_held(void)
531 {
532 return percpu_rwsem_is_held(&cpu_hotplug_lock);
533 }
534 #endif
535
lockdep_acquire_cpus_lock(void)536 static void lockdep_acquire_cpus_lock(void)
537 {
538 rwsem_acquire(&cpu_hotplug_lock.dep_map, 0, 0, _THIS_IP_);
539 }
540
lockdep_release_cpus_lock(void)541 static void lockdep_release_cpus_lock(void)
542 {
543 rwsem_release(&cpu_hotplug_lock.dep_map, _THIS_IP_);
544 }
545
546 /*
547 * Wait for currently running CPU hotplug operations to complete (if any) and
548 * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
549 * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
550 * hotplug path before performing hotplug operations. So acquiring that lock
551 * guarantees mutual exclusion from any currently running hotplug operations.
552 */
cpu_hotplug_disable(void)553 void cpu_hotplug_disable(void)
554 {
555 cpu_maps_update_begin();
556 cpu_hotplug_disabled++;
557 cpu_maps_update_done();
558 }
559 EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
560
__cpu_hotplug_enable(void)561 static void __cpu_hotplug_enable(void)
562 {
563 if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
564 return;
565 cpu_hotplug_disabled--;
566 }
567
cpu_hotplug_enable(void)568 void cpu_hotplug_enable(void)
569 {
570 cpu_maps_update_begin();
571 __cpu_hotplug_enable();
572 cpu_maps_update_done();
573 }
574 EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
575
576 #else
577
lockdep_acquire_cpus_lock(void)578 static void lockdep_acquire_cpus_lock(void)
579 {
580 }
581
lockdep_release_cpus_lock(void)582 static void lockdep_release_cpus_lock(void)
583 {
584 }
585
586 #endif /* CONFIG_HOTPLUG_CPU */
587
588 /*
589 * Architectures that need SMT-specific errata handling during SMT hotplug
590 * should override this.
591 */
arch_smt_update(void)592 void __weak arch_smt_update(void) { }
593
594 #ifdef CONFIG_HOTPLUG_SMT
595
596 enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED;
597 static unsigned int cpu_smt_max_threads __ro_after_init;
598 unsigned int cpu_smt_num_threads __read_mostly = UINT_MAX;
599
cpu_smt_disable(bool force)600 void __init cpu_smt_disable(bool force)
601 {
602 if (!cpu_smt_possible())
603 return;
604
605 if (force) {
606 pr_info("SMT: Force disabled\n");
607 cpu_smt_control = CPU_SMT_FORCE_DISABLED;
608 } else {
609 pr_info("SMT: disabled\n");
610 cpu_smt_control = CPU_SMT_DISABLED;
611 }
612 cpu_smt_num_threads = 1;
613 }
614
615 /*
616 * The decision whether SMT is supported can only be done after the full
617 * CPU identification. Called from architecture code.
618 */
cpu_smt_set_num_threads(unsigned int num_threads,unsigned int max_threads)619 void __init cpu_smt_set_num_threads(unsigned int num_threads,
620 unsigned int max_threads)
621 {
622 WARN_ON(!num_threads || (num_threads > max_threads));
623
624 if (max_threads == 1)
625 cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
626
627 cpu_smt_max_threads = max_threads;
628
629 /*
630 * If SMT has been disabled via the kernel command line or SMT is
631 * not supported, set cpu_smt_num_threads to 1 for consistency.
632 * If enabled, take the architecture requested number of threads
633 * to bring up into account.
634 */
635 if (cpu_smt_control != CPU_SMT_ENABLED)
636 cpu_smt_num_threads = 1;
637 else if (num_threads < cpu_smt_num_threads)
638 cpu_smt_num_threads = num_threads;
639 }
640
smt_cmdline_disable(char * str)641 static int __init smt_cmdline_disable(char *str)
642 {
643 cpu_smt_disable(str && !strcmp(str, "force"));
644 return 0;
645 }
646 early_param("nosmt", smt_cmdline_disable);
647
648 /*
649 * For Archicture supporting partial SMT states check if the thread is allowed.
650 * Otherwise this has already been checked through cpu_smt_max_threads when
651 * setting the SMT level.
652 */
cpu_smt_thread_allowed(unsigned int cpu)653 static inline bool cpu_smt_thread_allowed(unsigned int cpu)
654 {
655 #ifdef CONFIG_SMT_NUM_THREADS_DYNAMIC
656 return topology_smt_thread_allowed(cpu);
657 #else
658 return true;
659 #endif
660 }
661
cpu_bootable(unsigned int cpu)662 static inline bool cpu_bootable(unsigned int cpu)
663 {
664 if (cpu_smt_control == CPU_SMT_ENABLED && cpu_smt_thread_allowed(cpu))
665 return true;
666
667 /* All CPUs are bootable if controls are not configured */
668 if (cpu_smt_control == CPU_SMT_NOT_IMPLEMENTED)
669 return true;
670
671 /* All CPUs are bootable if CPU is not SMT capable */
672 if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
673 return true;
674
675 if (topology_is_primary_thread(cpu))
676 return true;
677
678 /*
679 * On x86 it's required to boot all logical CPUs at least once so
680 * that the init code can get a chance to set CR4.MCE on each
681 * CPU. Otherwise, a broadcasted MCE observing CR4.MCE=0b on any
682 * core will shutdown the machine.
683 */
684 return !cpumask_test_cpu(cpu, &cpus_booted_once_mask);
685 }
686
687 /* Returns true if SMT is supported and not forcefully (irreversibly) disabled */
cpu_smt_possible(void)688 bool cpu_smt_possible(void)
689 {
690 return cpu_smt_control != CPU_SMT_FORCE_DISABLED &&
691 cpu_smt_control != CPU_SMT_NOT_SUPPORTED;
692 }
693 EXPORT_SYMBOL_GPL(cpu_smt_possible);
694
695 #else
cpu_bootable(unsigned int cpu)696 static inline bool cpu_bootable(unsigned int cpu) { return true; }
697 #endif
698
699 static inline enum cpuhp_state
cpuhp_set_state(int cpu,struct cpuhp_cpu_state * st,enum cpuhp_state target)700 cpuhp_set_state(int cpu, struct cpuhp_cpu_state *st, enum cpuhp_state target)
701 {
702 enum cpuhp_state prev_state = st->state;
703 bool bringup = st->state < target;
704
705 st->rollback = false;
706 st->last = NULL;
707
708 st->target = target;
709 st->single = false;
710 st->bringup = bringup;
711 if (cpu_dying(cpu) != !bringup)
712 set_cpu_dying(cpu, !bringup);
713
714 return prev_state;
715 }
716
717 static inline void
cpuhp_reset_state(int cpu,struct cpuhp_cpu_state * st,enum cpuhp_state prev_state)718 cpuhp_reset_state(int cpu, struct cpuhp_cpu_state *st,
719 enum cpuhp_state prev_state)
720 {
721 bool bringup = !st->bringup;
722
723 st->target = prev_state;
724
725 /*
726 * Already rolling back. No need invert the bringup value or to change
727 * the current state.
728 */
729 if (st->rollback)
730 return;
731
732 st->rollback = true;
733
734 /*
735 * If we have st->last we need to undo partial multi_instance of this
736 * state first. Otherwise start undo at the previous state.
737 */
738 if (!st->last) {
739 if (st->bringup)
740 st->state--;
741 else
742 st->state++;
743 }
744
745 st->bringup = bringup;
746 if (cpu_dying(cpu) != !bringup)
747 set_cpu_dying(cpu, !bringup);
748 }
749
750 /* Regular hotplug invocation of the AP hotplug thread */
__cpuhp_kick_ap(struct cpuhp_cpu_state * st)751 static void __cpuhp_kick_ap(struct cpuhp_cpu_state *st)
752 {
753 if (!st->single && st->state == st->target)
754 return;
755
756 st->result = 0;
757 /*
758 * Make sure the above stores are visible before should_run becomes
759 * true. Paired with the mb() above in cpuhp_thread_fun()
760 */
761 smp_mb();
762 st->should_run = true;
763 wake_up_process(st->thread);
764 wait_for_ap_thread(st, st->bringup);
765 }
766
cpuhp_kick_ap(int cpu,struct cpuhp_cpu_state * st,enum cpuhp_state target)767 static int cpuhp_kick_ap(int cpu, struct cpuhp_cpu_state *st,
768 enum cpuhp_state target)
769 {
770 enum cpuhp_state prev_state;
771 int ret;
772
773 prev_state = cpuhp_set_state(cpu, st, target);
774 __cpuhp_kick_ap(st);
775 if ((ret = st->result)) {
776 cpuhp_reset_state(cpu, st, prev_state);
777 __cpuhp_kick_ap(st);
778 }
779
780 return ret;
781 }
782
bringup_wait_for_ap_online(unsigned int cpu)783 static int bringup_wait_for_ap_online(unsigned int cpu)
784 {
785 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
786
787 /* Wait for the CPU to reach CPUHP_AP_ONLINE_IDLE */
788 wait_for_ap_thread(st, true);
789 if (WARN_ON_ONCE((!cpu_online(cpu))))
790 return -ECANCELED;
791
792 /* Unpark the hotplug thread of the target cpu */
793 kthread_unpark(st->thread);
794
795 /*
796 * SMT soft disabling on X86 requires to bring the CPU out of the
797 * BIOS 'wait for SIPI' state in order to set the CR4.MCE bit. The
798 * CPU marked itself as booted_once in notify_cpu_starting() so the
799 * cpu_bootable() check will now return false if this is not the
800 * primary sibling.
801 */
802 if (!cpu_bootable(cpu))
803 return -ECANCELED;
804 return 0;
805 }
806
807 #ifdef CONFIG_HOTPLUG_SPLIT_STARTUP
cpuhp_kick_ap_alive(unsigned int cpu)808 static int cpuhp_kick_ap_alive(unsigned int cpu)
809 {
810 if (!cpuhp_can_boot_ap(cpu))
811 return -EAGAIN;
812
813 return arch_cpuhp_kick_ap_alive(cpu, idle_thread_get(cpu));
814 }
815
cpuhp_bringup_ap(unsigned int cpu)816 static int cpuhp_bringup_ap(unsigned int cpu)
817 {
818 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
819 int ret;
820
821 /*
822 * Some architectures have to walk the irq descriptors to
823 * setup the vector space for the cpu which comes online.
824 * Prevent irq alloc/free across the bringup.
825 */
826 irq_lock_sparse();
827
828 ret = cpuhp_bp_sync_alive(cpu);
829 if (ret)
830 goto out_unlock;
831
832 ret = bringup_wait_for_ap_online(cpu);
833 if (ret)
834 goto out_unlock;
835
836 irq_unlock_sparse();
837
838 if (st->target <= CPUHP_AP_ONLINE_IDLE)
839 return 0;
840
841 return cpuhp_kick_ap(cpu, st, st->target);
842
843 out_unlock:
844 irq_unlock_sparse();
845 return ret;
846 }
847 #else
bringup_cpu(unsigned int cpu)848 static int bringup_cpu(unsigned int cpu)
849 {
850 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
851 struct task_struct *idle = idle_thread_get(cpu);
852 int ret;
853
854 if (!cpuhp_can_boot_ap(cpu))
855 return -EAGAIN;
856
857 /*
858 * Some architectures have to walk the irq descriptors to
859 * setup the vector space for the cpu which comes online.
860 *
861 * Prevent irq alloc/free across the bringup by acquiring the
862 * sparse irq lock. Hold it until the upcoming CPU completes the
863 * startup in cpuhp_online_idle() which allows to avoid
864 * intermediate synchronization points in the architecture code.
865 */
866 irq_lock_sparse();
867
868 ret = __cpu_up(cpu, idle);
869 if (ret)
870 goto out_unlock;
871
872 ret = cpuhp_bp_sync_alive(cpu);
873 if (ret)
874 goto out_unlock;
875
876 ret = bringup_wait_for_ap_online(cpu);
877 if (ret)
878 goto out_unlock;
879
880 irq_unlock_sparse();
881
882 if (st->target <= CPUHP_AP_ONLINE_IDLE)
883 return 0;
884
885 return cpuhp_kick_ap(cpu, st, st->target);
886
887 out_unlock:
888 irq_unlock_sparse();
889 return ret;
890 }
891 #endif
892
finish_cpu(unsigned int cpu)893 static int finish_cpu(unsigned int cpu)
894 {
895 struct task_struct *idle = idle_thread_get(cpu);
896 struct mm_struct *mm = idle->active_mm;
897
898 /*
899 * idle_task_exit() will have switched to &init_mm, now
900 * clean up any remaining active_mm state.
901 */
902 if (mm != &init_mm)
903 idle->active_mm = &init_mm;
904 mmdrop_lazy_tlb(mm);
905 return 0;
906 }
907
908 /*
909 * Hotplug state machine related functions
910 */
911
912 /*
913 * Get the next state to run. Empty ones will be skipped. Returns true if a
914 * state must be run.
915 *
916 * st->state will be modified ahead of time, to match state_to_run, as if it
917 * has already ran.
918 */
cpuhp_next_state(bool bringup,enum cpuhp_state * state_to_run,struct cpuhp_cpu_state * st,enum cpuhp_state target)919 static bool cpuhp_next_state(bool bringup,
920 enum cpuhp_state *state_to_run,
921 struct cpuhp_cpu_state *st,
922 enum cpuhp_state target)
923 {
924 do {
925 if (bringup) {
926 if (st->state >= target)
927 return false;
928
929 *state_to_run = ++st->state;
930 } else {
931 if (st->state <= target)
932 return false;
933
934 *state_to_run = st->state--;
935 }
936
937 if (!cpuhp_step_empty(bringup, cpuhp_get_step(*state_to_run)))
938 break;
939 } while (true);
940
941 return true;
942 }
943
__cpuhp_invoke_callback_range(bool bringup,unsigned int cpu,struct cpuhp_cpu_state * st,enum cpuhp_state target,bool nofail)944 static int __cpuhp_invoke_callback_range(bool bringup,
945 unsigned int cpu,
946 struct cpuhp_cpu_state *st,
947 enum cpuhp_state target,
948 bool nofail)
949 {
950 enum cpuhp_state state;
951 int ret = 0;
952
953 while (cpuhp_next_state(bringup, &state, st, target)) {
954 int err;
955
956 err = cpuhp_invoke_callback(cpu, state, bringup, NULL, NULL);
957 if (!err)
958 continue;
959
960 if (nofail) {
961 pr_warn("CPU %u %s state %s (%d) failed (%d)\n",
962 cpu, bringup ? "UP" : "DOWN",
963 cpuhp_get_step(st->state)->name,
964 st->state, err);
965 ret = -1;
966 } else {
967 ret = err;
968 break;
969 }
970 }
971
972 return ret;
973 }
974
cpuhp_invoke_callback_range(bool bringup,unsigned int cpu,struct cpuhp_cpu_state * st,enum cpuhp_state target)975 static inline int cpuhp_invoke_callback_range(bool bringup,
976 unsigned int cpu,
977 struct cpuhp_cpu_state *st,
978 enum cpuhp_state target)
979 {
980 return __cpuhp_invoke_callback_range(bringup, cpu, st, target, false);
981 }
982
cpuhp_invoke_callback_range_nofail(bool bringup,unsigned int cpu,struct cpuhp_cpu_state * st,enum cpuhp_state target)983 static inline void cpuhp_invoke_callback_range_nofail(bool bringup,
984 unsigned int cpu,
985 struct cpuhp_cpu_state *st,
986 enum cpuhp_state target)
987 {
988 __cpuhp_invoke_callback_range(bringup, cpu, st, target, true);
989 }
990
can_rollback_cpu(struct cpuhp_cpu_state * st)991 static inline bool can_rollback_cpu(struct cpuhp_cpu_state *st)
992 {
993 if (IS_ENABLED(CONFIG_HOTPLUG_CPU))
994 return true;
995 /*
996 * When CPU hotplug is disabled, then taking the CPU down is not
997 * possible because takedown_cpu() and the architecture and
998 * subsystem specific mechanisms are not available. So the CPU
999 * which would be completely unplugged again needs to stay around
1000 * in the current state.
1001 */
1002 return st->state <= CPUHP_BRINGUP_CPU;
1003 }
1004
cpuhp_up_callbacks(unsigned int cpu,struct cpuhp_cpu_state * st,enum cpuhp_state target)1005 static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
1006 enum cpuhp_state target)
1007 {
1008 enum cpuhp_state prev_state = st->state;
1009 int ret = 0;
1010
1011 ret = cpuhp_invoke_callback_range(true, cpu, st, target);
1012 if (ret) {
1013 pr_debug("CPU UP failed (%d) CPU %u state %s (%d)\n",
1014 ret, cpu, cpuhp_get_step(st->state)->name,
1015 st->state);
1016
1017 cpuhp_reset_state(cpu, st, prev_state);
1018 if (can_rollback_cpu(st))
1019 WARN_ON(cpuhp_invoke_callback_range(false, cpu, st,
1020 prev_state));
1021 }
1022 return ret;
1023 }
1024
1025 /*
1026 * The cpu hotplug threads manage the bringup and teardown of the cpus
1027 */
cpuhp_should_run(unsigned int cpu)1028 static int cpuhp_should_run(unsigned int cpu)
1029 {
1030 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1031
1032 return st->should_run;
1033 }
1034
1035 /*
1036 * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
1037 * callbacks when a state gets [un]installed at runtime.
1038 *
1039 * Each invocation of this function by the smpboot thread does a single AP
1040 * state callback.
1041 *
1042 * It has 3 modes of operation:
1043 * - single: runs st->cb_state
1044 * - up: runs ++st->state, while st->state < st->target
1045 * - down: runs st->state--, while st->state > st->target
1046 *
1047 * When complete or on error, should_run is cleared and the completion is fired.
1048 */
cpuhp_thread_fun(unsigned int cpu)1049 static void cpuhp_thread_fun(unsigned int cpu)
1050 {
1051 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1052 bool bringup = st->bringup;
1053 enum cpuhp_state state;
1054
1055 if (WARN_ON_ONCE(!st->should_run))
1056 return;
1057
1058 /*
1059 * ACQUIRE for the cpuhp_should_run() load of ->should_run. Ensures
1060 * that if we see ->should_run we also see the rest of the state.
1061 */
1062 smp_mb();
1063
1064 /*
1065 * The BP holds the hotplug lock, but we're now running on the AP,
1066 * ensure that anybody asserting the lock is held, will actually find
1067 * it so.
1068 */
1069 lockdep_acquire_cpus_lock();
1070 cpuhp_lock_acquire(bringup);
1071
1072 if (st->single) {
1073 state = st->cb_state;
1074 st->should_run = false;
1075 } else {
1076 st->should_run = cpuhp_next_state(bringup, &state, st, st->target);
1077 if (!st->should_run)
1078 goto end;
1079 }
1080
1081 WARN_ON_ONCE(!cpuhp_is_ap_state(state));
1082
1083 if (cpuhp_is_atomic_state(state)) {
1084 local_irq_disable();
1085 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
1086 local_irq_enable();
1087
1088 /*
1089 * STARTING/DYING must not fail!
1090 */
1091 WARN_ON_ONCE(st->result);
1092 } else {
1093 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
1094 }
1095
1096 if (st->result) {
1097 /*
1098 * If we fail on a rollback, we're up a creek without no
1099 * paddle, no way forward, no way back. We loose, thanks for
1100 * playing.
1101 */
1102 WARN_ON_ONCE(st->rollback);
1103 st->should_run = false;
1104 }
1105
1106 end:
1107 cpuhp_lock_release(bringup);
1108 lockdep_release_cpus_lock();
1109
1110 if (!st->should_run)
1111 complete_ap_thread(st, bringup);
1112 }
1113
1114 /* Invoke a single callback on a remote cpu */
1115 static int
cpuhp_invoke_ap_callback(int cpu,enum cpuhp_state state,bool bringup,struct hlist_node * node)1116 cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, bool bringup,
1117 struct hlist_node *node)
1118 {
1119 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1120 int ret;
1121
1122 if (!cpu_online(cpu))
1123 return 0;
1124
1125 cpuhp_lock_acquire(false);
1126 cpuhp_lock_release(false);
1127
1128 cpuhp_lock_acquire(true);
1129 cpuhp_lock_release(true);
1130
1131 /*
1132 * If we are up and running, use the hotplug thread. For early calls
1133 * we invoke the thread function directly.
1134 */
1135 if (!st->thread)
1136 return cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1137
1138 st->rollback = false;
1139 st->last = NULL;
1140
1141 st->node = node;
1142 st->bringup = bringup;
1143 st->cb_state = state;
1144 st->single = true;
1145
1146 __cpuhp_kick_ap(st);
1147
1148 /*
1149 * If we failed and did a partial, do a rollback.
1150 */
1151 if ((ret = st->result) && st->last) {
1152 st->rollback = true;
1153 st->bringup = !bringup;
1154
1155 __cpuhp_kick_ap(st);
1156 }
1157
1158 /*
1159 * Clean up the leftovers so the next hotplug operation wont use stale
1160 * data.
1161 */
1162 st->node = st->last = NULL;
1163 return ret;
1164 }
1165
cpuhp_kick_ap_work(unsigned int cpu)1166 static int cpuhp_kick_ap_work(unsigned int cpu)
1167 {
1168 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1169 enum cpuhp_state prev_state = st->state;
1170 int ret;
1171
1172 cpuhp_lock_acquire(false);
1173 cpuhp_lock_release(false);
1174
1175 cpuhp_lock_acquire(true);
1176 cpuhp_lock_release(true);
1177
1178 trace_cpuhp_enter(cpu, st->target, prev_state, cpuhp_kick_ap_work);
1179 ret = cpuhp_kick_ap(cpu, st, st->target);
1180 trace_cpuhp_exit(cpu, st->state, prev_state, ret);
1181
1182 return ret;
1183 }
1184
1185 static struct smp_hotplug_thread cpuhp_threads = {
1186 .store = &cpuhp_state.thread,
1187 .thread_should_run = cpuhp_should_run,
1188 .thread_fn = cpuhp_thread_fun,
1189 .thread_comm = "cpuhp/%u",
1190 .selfparking = true,
1191 };
1192
cpuhp_init_state(void)1193 static __init void cpuhp_init_state(void)
1194 {
1195 struct cpuhp_cpu_state *st;
1196 int cpu;
1197
1198 for_each_possible_cpu(cpu) {
1199 st = per_cpu_ptr(&cpuhp_state, cpu);
1200 init_completion(&st->done_up);
1201 init_completion(&st->done_down);
1202 }
1203 }
1204
cpuhp_threads_init(void)1205 void __init cpuhp_threads_init(void)
1206 {
1207 cpuhp_init_state();
1208 BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
1209 kthread_unpark(this_cpu_read(cpuhp_state.thread));
1210 }
1211
1212 /*
1213 *
1214 * Serialize hotplug trainwrecks outside of the cpu_hotplug_lock
1215 * protected region.
1216 *
1217 * The operation is still serialized against concurrent CPU hotplug via
1218 * cpu_add_remove_lock, i.e. CPU map protection. But it is _not_
1219 * serialized against other hotplug related activity like adding or
1220 * removing of state callbacks and state instances, which invoke either the
1221 * startup or the teardown callback of the affected state.
1222 *
1223 * This is required for subsystems which are unfixable vs. CPU hotplug and
1224 * evade lock inversion problems by scheduling work which has to be
1225 * completed _before_ cpu_up()/_cpu_down() returns.
1226 *
1227 * Don't even think about adding anything to this for any new code or even
1228 * drivers. It's only purpose is to keep existing lock order trainwrecks
1229 * working.
1230 *
1231 * For cpu_down() there might be valid reasons to finish cleanups which are
1232 * not required to be done under cpu_hotplug_lock, but that's a different
1233 * story and would be not invoked via this.
1234 */
cpu_up_down_serialize_trainwrecks(bool tasks_frozen)1235 static void cpu_up_down_serialize_trainwrecks(bool tasks_frozen)
1236 {
1237 /*
1238 * cpusets delegate hotplug operations to a worker to "solve" the
1239 * lock order problems. Wait for the worker, but only if tasks are
1240 * _not_ frozen (suspend, hibernate) as that would wait forever.
1241 *
1242 * The wait is required because otherwise the hotplug operation
1243 * returns with inconsistent state, which could even be observed in
1244 * user space when a new CPU is brought up. The CPU plug uevent
1245 * would be delivered and user space reacting on it would fail to
1246 * move tasks to the newly plugged CPU up to the point where the
1247 * work has finished because up to that point the newly plugged CPU
1248 * is not assignable in cpusets/cgroups. On unplug that's not
1249 * necessarily a visible issue, but it is still inconsistent state,
1250 * which is the real problem which needs to be "fixed". This can't
1251 * prevent the transient state between scheduling the work and
1252 * returning from waiting for it.
1253 */
1254 if (!tasks_frozen)
1255 cpuset_wait_for_hotplug();
1256 }
1257
1258 #ifdef CONFIG_HOTPLUG_CPU
1259 #ifndef arch_clear_mm_cpumask_cpu
1260 #define arch_clear_mm_cpumask_cpu(cpu, mm) cpumask_clear_cpu(cpu, mm_cpumask(mm))
1261 #endif
1262
1263 /**
1264 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
1265 * @cpu: a CPU id
1266 *
1267 * This function walks all processes, finds a valid mm struct for each one and
1268 * then clears a corresponding bit in mm's cpumask. While this all sounds
1269 * trivial, there are various non-obvious corner cases, which this function
1270 * tries to solve in a safe manner.
1271 *
1272 * Also note that the function uses a somewhat relaxed locking scheme, so it may
1273 * be called only for an already offlined CPU.
1274 */
clear_tasks_mm_cpumask(int cpu)1275 void clear_tasks_mm_cpumask(int cpu)
1276 {
1277 struct task_struct *p;
1278
1279 /*
1280 * This function is called after the cpu is taken down and marked
1281 * offline, so its not like new tasks will ever get this cpu set in
1282 * their mm mask. -- Peter Zijlstra
1283 * Thus, we may use rcu_read_lock() here, instead of grabbing
1284 * full-fledged tasklist_lock.
1285 */
1286 WARN_ON(cpu_online(cpu));
1287 rcu_read_lock();
1288 for_each_process(p) {
1289 struct task_struct *t;
1290
1291 /*
1292 * Main thread might exit, but other threads may still have
1293 * a valid mm. Find one.
1294 */
1295 t = find_lock_task_mm(p);
1296 if (!t)
1297 continue;
1298 arch_clear_mm_cpumask_cpu(cpu, t->mm);
1299 task_unlock(t);
1300 }
1301 rcu_read_unlock();
1302 }
1303
1304 /* Take this CPU down. */
take_cpu_down(void * _param)1305 static int take_cpu_down(void *_param)
1306 {
1307 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1308 enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
1309 int err, cpu = smp_processor_id();
1310
1311 /* Ensure this CPU doesn't handle any more interrupts. */
1312 err = __cpu_disable();
1313 if (err < 0)
1314 return err;
1315
1316 /*
1317 * Must be called from CPUHP_TEARDOWN_CPU, which means, as we are going
1318 * down, that the current state is CPUHP_TEARDOWN_CPU - 1.
1319 */
1320 WARN_ON(st->state != (CPUHP_TEARDOWN_CPU - 1));
1321
1322 /*
1323 * Invoke the former CPU_DYING callbacks. DYING must not fail!
1324 */
1325 cpuhp_invoke_callback_range_nofail(false, cpu, st, target);
1326
1327 /* Give up timekeeping duties */
1328 tick_handover_do_timer();
1329 /* Remove CPU from timer broadcasting */
1330 tick_offline_cpu(cpu);
1331 /* Park the stopper thread */
1332 stop_machine_park(cpu);
1333 return 0;
1334 }
1335
takedown_cpu(unsigned int cpu)1336 static int takedown_cpu(unsigned int cpu)
1337 {
1338 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1339 int err;
1340
1341 /* Park the smpboot threads */
1342 kthread_park(st->thread);
1343
1344 /*
1345 * Prevent irq alloc/free while the dying cpu reorganizes the
1346 * interrupt affinities.
1347 */
1348 irq_lock_sparse();
1349
1350 /*
1351 * So now all preempt/rcu users must observe !cpu_active().
1352 */
1353 err = stop_machine_cpuslocked(take_cpu_down, NULL, cpumask_of(cpu));
1354 if (err) {
1355 /* CPU refused to die */
1356 irq_unlock_sparse();
1357 /* Unpark the hotplug thread so we can rollback there */
1358 kthread_unpark(st->thread);
1359 return err;
1360 }
1361 BUG_ON(cpu_online(cpu));
1362
1363 /*
1364 * The teardown callback for CPUHP_AP_SCHED_STARTING will have removed
1365 * all runnable tasks from the CPU, there's only the idle task left now
1366 * that the migration thread is done doing the stop_machine thing.
1367 *
1368 * Wait for the stop thread to go away.
1369 */
1370 wait_for_ap_thread(st, false);
1371 BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
1372
1373 /* Interrupts are moved away from the dying cpu, reenable alloc/free */
1374 irq_unlock_sparse();
1375
1376 hotplug_cpu__broadcast_tick_pull(cpu);
1377 /* This actually kills the CPU. */
1378 __cpu_die(cpu);
1379
1380 cpuhp_bp_sync_dead(cpu);
1381
1382 tick_cleanup_dead_cpu(cpu);
1383 rcutree_migrate_callbacks(cpu);
1384 return 0;
1385 }
1386
cpuhp_complete_idle_dead(void * arg)1387 static void cpuhp_complete_idle_dead(void *arg)
1388 {
1389 struct cpuhp_cpu_state *st = arg;
1390
1391 complete_ap_thread(st, false);
1392 }
1393
cpuhp_report_idle_dead(void)1394 void cpuhp_report_idle_dead(void)
1395 {
1396 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1397
1398 BUG_ON(st->state != CPUHP_AP_OFFLINE);
1399 rcu_report_dead(smp_processor_id());
1400 st->state = CPUHP_AP_IDLE_DEAD;
1401 /*
1402 * We cannot call complete after rcu_report_dead() so we delegate it
1403 * to an online cpu.
1404 */
1405 smp_call_function_single(cpumask_first(cpu_online_mask),
1406 cpuhp_complete_idle_dead, st, 0);
1407 }
1408
cpuhp_down_callbacks(unsigned int cpu,struct cpuhp_cpu_state * st,enum cpuhp_state target)1409 static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
1410 enum cpuhp_state target)
1411 {
1412 enum cpuhp_state prev_state = st->state;
1413 int ret = 0;
1414
1415 ret = cpuhp_invoke_callback_range(false, cpu, st, target);
1416 if (ret) {
1417 pr_debug("CPU DOWN failed (%d) CPU %u state %s (%d)\n",
1418 ret, cpu, cpuhp_get_step(st->state)->name,
1419 st->state);
1420
1421 cpuhp_reset_state(cpu, st, prev_state);
1422
1423 if (st->state < prev_state)
1424 WARN_ON(cpuhp_invoke_callback_range(true, cpu, st,
1425 prev_state));
1426 }
1427
1428 return ret;
1429 }
1430
1431 /* Requires cpu_add_remove_lock to be held */
_cpu_down(unsigned int cpu,int tasks_frozen,enum cpuhp_state target)1432 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
1433 enum cpuhp_state target)
1434 {
1435 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1436 int prev_state, ret = 0;
1437
1438 if (num_online_cpus() == 1)
1439 return -EBUSY;
1440
1441 if (!cpu_present(cpu))
1442 return -EINVAL;
1443
1444 cpus_write_lock();
1445
1446 cpuhp_tasks_frozen = tasks_frozen;
1447
1448 prev_state = cpuhp_set_state(cpu, st, target);
1449 /*
1450 * If the current CPU state is in the range of the AP hotplug thread,
1451 * then we need to kick the thread.
1452 */
1453 if (st->state > CPUHP_TEARDOWN_CPU) {
1454 st->target = max((int)target, CPUHP_TEARDOWN_CPU);
1455 ret = cpuhp_kick_ap_work(cpu);
1456 /*
1457 * The AP side has done the error rollback already. Just
1458 * return the error code..
1459 */
1460 if (ret)
1461 goto out;
1462
1463 /*
1464 * We might have stopped still in the range of the AP hotplug
1465 * thread. Nothing to do anymore.
1466 */
1467 if (st->state > CPUHP_TEARDOWN_CPU)
1468 goto out;
1469
1470 st->target = target;
1471 }
1472 /*
1473 * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
1474 * to do the further cleanups.
1475 */
1476 ret = cpuhp_down_callbacks(cpu, st, target);
1477 if (ret && st->state < prev_state) {
1478 if (st->state == CPUHP_TEARDOWN_CPU) {
1479 cpuhp_reset_state(cpu, st, prev_state);
1480 __cpuhp_kick_ap(st);
1481 } else {
1482 WARN(1, "DEAD callback error for CPU%d", cpu);
1483 }
1484 }
1485
1486 out:
1487 cpus_write_unlock();
1488 /*
1489 * Do post unplug cleanup. This is still protected against
1490 * concurrent CPU hotplug via cpu_add_remove_lock.
1491 */
1492 lockup_detector_cleanup();
1493 arch_smt_update();
1494 cpu_up_down_serialize_trainwrecks(tasks_frozen);
1495 return ret;
1496 }
1497
1498 struct cpu_down_work {
1499 unsigned int cpu;
1500 enum cpuhp_state target;
1501 };
1502
__cpu_down_maps_locked(void * arg)1503 static long __cpu_down_maps_locked(void *arg)
1504 {
1505 struct cpu_down_work *work = arg;
1506
1507 return _cpu_down(work->cpu, 0, work->target);
1508 }
1509
cpu_down_maps_locked(unsigned int cpu,enum cpuhp_state target)1510 static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target)
1511 {
1512 struct cpu_down_work work = { .cpu = cpu, .target = target, };
1513
1514 /*
1515 * If the platform does not support hotplug, report it explicitly to
1516 * differentiate it from a transient offlining failure.
1517 */
1518 if (cc_platform_has(CC_ATTR_HOTPLUG_DISABLED))
1519 return -EOPNOTSUPP;
1520 if (cpu_hotplug_disabled)
1521 return -EBUSY;
1522
1523 /*
1524 * Ensure that the control task does not run on the to be offlined
1525 * CPU to prevent a deadlock against cfs_b->period_timer.
1526 * Also keep at least one housekeeping cpu onlined to avoid generating
1527 * an empty sched_domain span.
1528 */
1529 for_each_cpu_and(cpu, cpu_online_mask, housekeeping_cpumask(HK_TYPE_DOMAIN)) {
1530 if (cpu != work.cpu)
1531 return work_on_cpu(cpu, __cpu_down_maps_locked, &work);
1532 }
1533 return -EBUSY;
1534 }
1535
cpu_down(unsigned int cpu,enum cpuhp_state target)1536 static int cpu_down(unsigned int cpu, enum cpuhp_state target)
1537 {
1538 int err;
1539
1540 cpu_maps_update_begin();
1541 err = cpu_down_maps_locked(cpu, target);
1542 cpu_maps_update_done();
1543 return err;
1544 }
1545
1546 /**
1547 * cpu_device_down - Bring down a cpu device
1548 * @dev: Pointer to the cpu device to offline
1549 *
1550 * This function is meant to be used by device core cpu subsystem only.
1551 *
1552 * Other subsystems should use remove_cpu() instead.
1553 *
1554 * Return: %0 on success or a negative errno code
1555 */
cpu_device_down(struct device * dev)1556 int cpu_device_down(struct device *dev)
1557 {
1558 return cpu_down(dev->id, CPUHP_OFFLINE);
1559 }
1560
remove_cpu(unsigned int cpu)1561 int remove_cpu(unsigned int cpu)
1562 {
1563 int ret;
1564
1565 lock_device_hotplug();
1566 ret = device_offline(get_cpu_device(cpu));
1567 unlock_device_hotplug();
1568
1569 return ret;
1570 }
1571 EXPORT_SYMBOL_GPL(remove_cpu);
1572
smp_shutdown_nonboot_cpus(unsigned int primary_cpu)1573 void smp_shutdown_nonboot_cpus(unsigned int primary_cpu)
1574 {
1575 unsigned int cpu;
1576 int error;
1577
1578 cpu_maps_update_begin();
1579
1580 /*
1581 * Make certain the cpu I'm about to reboot on is online.
1582 *
1583 * This is inline to what migrate_to_reboot_cpu() already do.
1584 */
1585 if (!cpu_online(primary_cpu))
1586 primary_cpu = cpumask_first(cpu_online_mask);
1587
1588 for_each_online_cpu(cpu) {
1589 if (cpu == primary_cpu)
1590 continue;
1591
1592 error = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
1593 if (error) {
1594 pr_err("Failed to offline CPU%d - error=%d",
1595 cpu, error);
1596 break;
1597 }
1598 }
1599
1600 /*
1601 * Ensure all but the reboot CPU are offline.
1602 */
1603 BUG_ON(num_online_cpus() > 1);
1604
1605 /*
1606 * Make sure the CPUs won't be enabled by someone else after this
1607 * point. Kexec will reboot to a new kernel shortly resetting
1608 * everything along the way.
1609 */
1610 cpu_hotplug_disabled++;
1611
1612 cpu_maps_update_done();
1613 }
1614
1615 #else
1616 #define takedown_cpu NULL
1617 #endif /*CONFIG_HOTPLUG_CPU*/
1618
1619 /**
1620 * notify_cpu_starting(cpu) - Invoke the callbacks on the starting CPU
1621 * @cpu: cpu that just started
1622 *
1623 * It must be called by the arch code on the new cpu, before the new cpu
1624 * enables interrupts and before the "boot" cpu returns from __cpu_up().
1625 */
notify_cpu_starting(unsigned int cpu)1626 void notify_cpu_starting(unsigned int cpu)
1627 {
1628 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1629 enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
1630
1631 rcu_cpu_starting(cpu); /* Enables RCU usage on this CPU. */
1632 cpumask_set_cpu(cpu, &cpus_booted_once_mask);
1633
1634 /*
1635 * STARTING must not fail!
1636 */
1637 cpuhp_invoke_callback_range_nofail(true, cpu, st, target);
1638 }
1639
1640 /*
1641 * Called from the idle task. Wake up the controlling task which brings the
1642 * hotplug thread of the upcoming CPU up and then delegates the rest of the
1643 * online bringup to the hotplug thread.
1644 */
cpuhp_online_idle(enum cpuhp_state state)1645 void cpuhp_online_idle(enum cpuhp_state state)
1646 {
1647 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1648
1649 /* Happens for the boot cpu */
1650 if (state != CPUHP_AP_ONLINE_IDLE)
1651 return;
1652
1653 cpuhp_ap_update_sync_state(SYNC_STATE_ONLINE);
1654
1655 /*
1656 * Unpark the stopper thread before we start the idle loop (and start
1657 * scheduling); this ensures the stopper task is always available.
1658 */
1659 stop_machine_unpark(smp_processor_id());
1660
1661 st->state = CPUHP_AP_ONLINE_IDLE;
1662 complete_ap_thread(st, true);
1663 }
1664
1665 /* Requires cpu_add_remove_lock to be held */
_cpu_up(unsigned int cpu,int tasks_frozen,enum cpuhp_state target)1666 static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
1667 {
1668 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1669 struct task_struct *idle;
1670 int ret = 0;
1671
1672 cpus_write_lock();
1673
1674 if (!cpu_present(cpu)) {
1675 ret = -EINVAL;
1676 goto out;
1677 }
1678
1679 /*
1680 * The caller of cpu_up() might have raced with another
1681 * caller. Nothing to do.
1682 */
1683 if (st->state >= target)
1684 goto out;
1685
1686 if (st->state == CPUHP_OFFLINE) {
1687 /* Let it fail before we try to bring the cpu up */
1688 idle = idle_thread_get(cpu);
1689 if (IS_ERR(idle)) {
1690 ret = PTR_ERR(idle);
1691 goto out;
1692 }
1693
1694 /*
1695 * Reset stale stack state from the last time this CPU was online.
1696 */
1697 scs_task_reset(idle);
1698 kasan_unpoison_task_stack(idle);
1699 }
1700
1701 cpuhp_tasks_frozen = tasks_frozen;
1702
1703 cpuhp_set_state(cpu, st, target);
1704 /*
1705 * If the current CPU state is in the range of the AP hotplug thread,
1706 * then we need to kick the thread once more.
1707 */
1708 if (st->state > CPUHP_BRINGUP_CPU) {
1709 ret = cpuhp_kick_ap_work(cpu);
1710 /*
1711 * The AP side has done the error rollback already. Just
1712 * return the error code..
1713 */
1714 if (ret)
1715 goto out;
1716 }
1717
1718 /*
1719 * Try to reach the target state. We max out on the BP at
1720 * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
1721 * responsible for bringing it up to the target state.
1722 */
1723 target = min((int)target, CPUHP_BRINGUP_CPU);
1724 ret = cpuhp_up_callbacks(cpu, st, target);
1725 out:
1726 cpus_write_unlock();
1727 arch_smt_update();
1728 cpu_up_down_serialize_trainwrecks(tasks_frozen);
1729 return ret;
1730 }
1731
cpu_up(unsigned int cpu,enum cpuhp_state target)1732 static int cpu_up(unsigned int cpu, enum cpuhp_state target)
1733 {
1734 int err = 0;
1735
1736 if (!cpu_possible(cpu)) {
1737 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
1738 cpu);
1739 #if defined(CONFIG_IA64)
1740 pr_err("please check additional_cpus= boot parameter\n");
1741 #endif
1742 return -EINVAL;
1743 }
1744
1745 err = try_online_node(cpu_to_node(cpu));
1746 if (err)
1747 return err;
1748
1749 cpu_maps_update_begin();
1750
1751 if (cpu_hotplug_disabled) {
1752 err = -EBUSY;
1753 goto out;
1754 }
1755 if (!cpu_bootable(cpu)) {
1756 err = -EPERM;
1757 goto out;
1758 }
1759
1760 err = _cpu_up(cpu, 0, target);
1761 out:
1762 cpu_maps_update_done();
1763 return err;
1764 }
1765
1766 /**
1767 * cpu_device_up - Bring up a cpu device
1768 * @dev: Pointer to the cpu device to online
1769 *
1770 * This function is meant to be used by device core cpu subsystem only.
1771 *
1772 * Other subsystems should use add_cpu() instead.
1773 *
1774 * Return: %0 on success or a negative errno code
1775 */
cpu_device_up(struct device * dev)1776 int cpu_device_up(struct device *dev)
1777 {
1778 return cpu_up(dev->id, CPUHP_ONLINE);
1779 }
1780
add_cpu(unsigned int cpu)1781 int add_cpu(unsigned int cpu)
1782 {
1783 int ret;
1784
1785 lock_device_hotplug();
1786 ret = device_online(get_cpu_device(cpu));
1787 unlock_device_hotplug();
1788
1789 return ret;
1790 }
1791 EXPORT_SYMBOL_GPL(add_cpu);
1792
1793 /**
1794 * bringup_hibernate_cpu - Bring up the CPU that we hibernated on
1795 * @sleep_cpu: The cpu we hibernated on and should be brought up.
1796 *
1797 * On some architectures like arm64, we can hibernate on any CPU, but on
1798 * wake up the CPU we hibernated on might be offline as a side effect of
1799 * using maxcpus= for example.
1800 *
1801 * Return: %0 on success or a negative errno code
1802 */
bringup_hibernate_cpu(unsigned int sleep_cpu)1803 int bringup_hibernate_cpu(unsigned int sleep_cpu)
1804 {
1805 int ret;
1806
1807 if (!cpu_online(sleep_cpu)) {
1808 pr_info("Hibernated on a CPU that is offline! Bringing CPU up.\n");
1809 ret = cpu_up(sleep_cpu, CPUHP_ONLINE);
1810 if (ret) {
1811 pr_err("Failed to bring hibernate-CPU up!\n");
1812 return ret;
1813 }
1814 }
1815 return 0;
1816 }
1817
cpuhp_bringup_mask(const struct cpumask * mask,unsigned int ncpus,enum cpuhp_state target)1818 static void __init cpuhp_bringup_mask(const struct cpumask *mask, unsigned int ncpus,
1819 enum cpuhp_state target)
1820 {
1821 unsigned int cpu;
1822
1823 for_each_cpu(cpu, mask) {
1824 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1825
1826 if (cpu_up(cpu, target) && can_rollback_cpu(st)) {
1827 /*
1828 * If this failed then cpu_up() might have only
1829 * rolled back to CPUHP_BP_KICK_AP for the final
1830 * online. Clean it up. NOOP if already rolled back.
1831 */
1832 WARN_ON(cpuhp_invoke_callback_range(false, cpu, st, CPUHP_OFFLINE));
1833 }
1834
1835 if (!--ncpus)
1836 break;
1837 }
1838 }
1839
1840 #ifdef CONFIG_HOTPLUG_PARALLEL
1841 static bool __cpuhp_parallel_bringup __ro_after_init = true;
1842
parallel_bringup_parse_param(char * arg)1843 static int __init parallel_bringup_parse_param(char *arg)
1844 {
1845 return kstrtobool(arg, &__cpuhp_parallel_bringup);
1846 }
1847 early_param("cpuhp.parallel", parallel_bringup_parse_param);
1848
cpuhp_smt_aware(void)1849 static inline bool cpuhp_smt_aware(void)
1850 {
1851 return cpu_smt_max_threads > 1;
1852 }
1853
cpuhp_get_primary_thread_mask(void)1854 static inline const struct cpumask *cpuhp_get_primary_thread_mask(void)
1855 {
1856 return cpu_primary_thread_mask;
1857 }
1858
1859 /*
1860 * On architectures which have enabled parallel bringup this invokes all BP
1861 * prepare states for each of the to be onlined APs first. The last state
1862 * sends the startup IPI to the APs. The APs proceed through the low level
1863 * bringup code in parallel and then wait for the control CPU to release
1864 * them one by one for the final onlining procedure.
1865 *
1866 * This avoids waiting for each AP to respond to the startup IPI in
1867 * CPUHP_BRINGUP_CPU.
1868 */
cpuhp_bringup_cpus_parallel(unsigned int ncpus)1869 static bool __init cpuhp_bringup_cpus_parallel(unsigned int ncpus)
1870 {
1871 const struct cpumask *mask = cpu_present_mask;
1872
1873 if (__cpuhp_parallel_bringup)
1874 __cpuhp_parallel_bringup = arch_cpuhp_init_parallel_bringup();
1875 if (!__cpuhp_parallel_bringup)
1876 return false;
1877
1878 if (cpuhp_smt_aware()) {
1879 const struct cpumask *pmask = cpuhp_get_primary_thread_mask();
1880 static struct cpumask tmp_mask __initdata;
1881
1882 /*
1883 * X86 requires to prevent that SMT siblings stopped while
1884 * the primary thread does a microcode update for various
1885 * reasons. Bring the primary threads up first.
1886 */
1887 cpumask_and(&tmp_mask, mask, pmask);
1888 cpuhp_bringup_mask(&tmp_mask, ncpus, CPUHP_BP_KICK_AP);
1889 cpuhp_bringup_mask(&tmp_mask, ncpus, CPUHP_ONLINE);
1890 /* Account for the online CPUs */
1891 ncpus -= num_online_cpus();
1892 if (!ncpus)
1893 return true;
1894 /* Create the mask for secondary CPUs */
1895 cpumask_andnot(&tmp_mask, mask, pmask);
1896 mask = &tmp_mask;
1897 }
1898
1899 /* Bring the not-yet started CPUs up */
1900 cpuhp_bringup_mask(mask, ncpus, CPUHP_BP_KICK_AP);
1901 cpuhp_bringup_mask(mask, ncpus, CPUHP_ONLINE);
1902 return true;
1903 }
1904 #else
cpuhp_bringup_cpus_parallel(unsigned int ncpus)1905 static inline bool cpuhp_bringup_cpus_parallel(unsigned int ncpus) { return false; }
1906 #endif /* CONFIG_HOTPLUG_PARALLEL */
1907
bringup_nonboot_cpus(unsigned int setup_max_cpus)1908 void __init bringup_nonboot_cpus(unsigned int setup_max_cpus)
1909 {
1910 /* Try parallel bringup optimization if enabled */
1911 if (cpuhp_bringup_cpus_parallel(setup_max_cpus))
1912 return;
1913
1914 /* Full per CPU serialized bringup */
1915 cpuhp_bringup_mask(cpu_present_mask, setup_max_cpus, CPUHP_ONLINE);
1916 }
1917
1918 #ifdef CONFIG_PM_SLEEP_SMP
1919 static cpumask_var_t frozen_cpus;
1920
freeze_secondary_cpus(int primary)1921 int freeze_secondary_cpus(int primary)
1922 {
1923 int cpu, error = 0;
1924
1925 cpu_maps_update_begin();
1926 if (primary == -1) {
1927 primary = cpumask_first(cpu_online_mask);
1928 if (!housekeeping_cpu(primary, HK_TYPE_TIMER))
1929 primary = housekeeping_any_cpu(HK_TYPE_TIMER);
1930 } else {
1931 if (!cpu_online(primary))
1932 primary = cpumask_first(cpu_online_mask);
1933 }
1934
1935 /*
1936 * We take down all of the non-boot CPUs in one shot to avoid races
1937 * with the userspace trying to use the CPU hotplug at the same time
1938 */
1939 cpumask_clear(frozen_cpus);
1940
1941 pr_info("Disabling non-boot CPUs ...\n");
1942 for_each_online_cpu(cpu) {
1943 if (cpu == primary)
1944 continue;
1945
1946 if (pm_wakeup_pending()) {
1947 pr_info("Wakeup pending. Abort CPU freeze\n");
1948 error = -EBUSY;
1949 break;
1950 }
1951
1952 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
1953 error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
1954 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
1955 if (!error)
1956 cpumask_set_cpu(cpu, frozen_cpus);
1957 else {
1958 pr_err("Error taking CPU%d down: %d\n", cpu, error);
1959 break;
1960 }
1961 }
1962
1963 if (!error)
1964 BUG_ON(num_online_cpus() > 1);
1965 else
1966 pr_err("Non-boot CPUs are not disabled\n");
1967
1968 /*
1969 * Make sure the CPUs won't be enabled by someone else. We need to do
1970 * this even in case of failure as all freeze_secondary_cpus() users are
1971 * supposed to do thaw_secondary_cpus() on the failure path.
1972 */
1973 cpu_hotplug_disabled++;
1974
1975 cpu_maps_update_done();
1976 return error;
1977 }
1978
arch_thaw_secondary_cpus_begin(void)1979 void __weak arch_thaw_secondary_cpus_begin(void)
1980 {
1981 }
1982
arch_thaw_secondary_cpus_end(void)1983 void __weak arch_thaw_secondary_cpus_end(void)
1984 {
1985 }
1986
thaw_secondary_cpus(void)1987 void thaw_secondary_cpus(void)
1988 {
1989 int cpu, error;
1990
1991 /* Allow everyone to use the CPU hotplug again */
1992 cpu_maps_update_begin();
1993 __cpu_hotplug_enable();
1994 if (cpumask_empty(frozen_cpus))
1995 goto out;
1996
1997 pr_info("Enabling non-boot CPUs ...\n");
1998
1999 arch_thaw_secondary_cpus_begin();
2000
2001 for_each_cpu(cpu, frozen_cpus) {
2002 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
2003 error = _cpu_up(cpu, 1, CPUHP_ONLINE);
2004 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
2005 if (!error) {
2006 pr_info("CPU%d is up\n", cpu);
2007 continue;
2008 }
2009 pr_warn("Error taking CPU%d up: %d\n", cpu, error);
2010 }
2011
2012 arch_thaw_secondary_cpus_end();
2013
2014 cpumask_clear(frozen_cpus);
2015 out:
2016 cpu_maps_update_done();
2017 }
2018
alloc_frozen_cpus(void)2019 static int __init alloc_frozen_cpus(void)
2020 {
2021 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
2022 return -ENOMEM;
2023 return 0;
2024 }
2025 core_initcall(alloc_frozen_cpus);
2026
2027 /*
2028 * When callbacks for CPU hotplug notifications are being executed, we must
2029 * ensure that the state of the system with respect to the tasks being frozen
2030 * or not, as reported by the notification, remains unchanged *throughout the
2031 * duration* of the execution of the callbacks.
2032 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
2033 *
2034 * This synchronization is implemented by mutually excluding regular CPU
2035 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
2036 * Hibernate notifications.
2037 */
2038 static int
cpu_hotplug_pm_callback(struct notifier_block * nb,unsigned long action,void * ptr)2039 cpu_hotplug_pm_callback(struct notifier_block *nb,
2040 unsigned long action, void *ptr)
2041 {
2042 switch (action) {
2043
2044 case PM_SUSPEND_PREPARE:
2045 case PM_HIBERNATION_PREPARE:
2046 cpu_hotplug_disable();
2047 break;
2048
2049 case PM_POST_SUSPEND:
2050 case PM_POST_HIBERNATION:
2051 cpu_hotplug_enable();
2052 break;
2053
2054 default:
2055 return NOTIFY_DONE;
2056 }
2057
2058 return NOTIFY_OK;
2059 }
2060
2061
cpu_hotplug_pm_sync_init(void)2062 static int __init cpu_hotplug_pm_sync_init(void)
2063 {
2064 /*
2065 * cpu_hotplug_pm_callback has higher priority than x86
2066 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
2067 * to disable cpu hotplug to avoid cpu hotplug race.
2068 */
2069 pm_notifier(cpu_hotplug_pm_callback, 0);
2070 return 0;
2071 }
2072 core_initcall(cpu_hotplug_pm_sync_init);
2073
2074 #endif /* CONFIG_PM_SLEEP_SMP */
2075
2076 int __boot_cpu_id;
2077
2078 #endif /* CONFIG_SMP */
2079
2080 /* Boot processor state steps */
2081 static struct cpuhp_step cpuhp_hp_states[] = {
2082 [CPUHP_OFFLINE] = {
2083 .name = "offline",
2084 .startup.single = NULL,
2085 .teardown.single = NULL,
2086 },
2087 #ifdef CONFIG_SMP
2088 [CPUHP_CREATE_THREADS]= {
2089 .name = "threads:prepare",
2090 .startup.single = smpboot_create_threads,
2091 .teardown.single = NULL,
2092 .cant_stop = true,
2093 },
2094 [CPUHP_PERF_PREPARE] = {
2095 .name = "perf:prepare",
2096 .startup.single = perf_event_init_cpu,
2097 .teardown.single = perf_event_exit_cpu,
2098 },
2099 [CPUHP_RANDOM_PREPARE] = {
2100 .name = "random:prepare",
2101 .startup.single = random_prepare_cpu,
2102 .teardown.single = NULL,
2103 },
2104 [CPUHP_WORKQUEUE_PREP] = {
2105 .name = "workqueue:prepare",
2106 .startup.single = workqueue_prepare_cpu,
2107 .teardown.single = NULL,
2108 },
2109 [CPUHP_HRTIMERS_PREPARE] = {
2110 .name = "hrtimers:prepare",
2111 .startup.single = hrtimers_prepare_cpu,
2112 .teardown.single = NULL,
2113 },
2114 [CPUHP_SMPCFD_PREPARE] = {
2115 .name = "smpcfd:prepare",
2116 .startup.single = smpcfd_prepare_cpu,
2117 .teardown.single = smpcfd_dead_cpu,
2118 },
2119 [CPUHP_RELAY_PREPARE] = {
2120 .name = "relay:prepare",
2121 .startup.single = relay_prepare_cpu,
2122 .teardown.single = NULL,
2123 },
2124 [CPUHP_SLAB_PREPARE] = {
2125 .name = "slab:prepare",
2126 .startup.single = slab_prepare_cpu,
2127 .teardown.single = slab_dead_cpu,
2128 },
2129 [CPUHP_RCUTREE_PREP] = {
2130 .name = "RCU/tree:prepare",
2131 .startup.single = rcutree_prepare_cpu,
2132 .teardown.single = rcutree_dead_cpu,
2133 },
2134 /*
2135 * On the tear-down path, timers_dead_cpu() must be invoked
2136 * before blk_mq_queue_reinit_notify() from notify_dead(),
2137 * otherwise a RCU stall occurs.
2138 */
2139 [CPUHP_TIMERS_PREPARE] = {
2140 .name = "timers:prepare",
2141 .startup.single = timers_prepare_cpu,
2142 .teardown.single = timers_dead_cpu,
2143 },
2144
2145 #ifdef CONFIG_HOTPLUG_SPLIT_STARTUP
2146 /*
2147 * Kicks the AP alive. AP will wait in cpuhp_ap_sync_alive() until
2148 * the next step will release it.
2149 */
2150 [CPUHP_BP_KICK_AP] = {
2151 .name = "cpu:kick_ap",
2152 .startup.single = cpuhp_kick_ap_alive,
2153 },
2154
2155 /*
2156 * Waits for the AP to reach cpuhp_ap_sync_alive() and then
2157 * releases it for the complete bringup.
2158 */
2159 [CPUHP_BRINGUP_CPU] = {
2160 .name = "cpu:bringup",
2161 .startup.single = cpuhp_bringup_ap,
2162 .teardown.single = finish_cpu,
2163 .cant_stop = true,
2164 },
2165 #else
2166 /*
2167 * All-in-one CPU bringup state which includes the kick alive.
2168 */
2169 [CPUHP_BRINGUP_CPU] = {
2170 .name = "cpu:bringup",
2171 .startup.single = bringup_cpu,
2172 .teardown.single = finish_cpu,
2173 .cant_stop = true,
2174 },
2175 #endif
2176 /* Final state before CPU kills itself */
2177 [CPUHP_AP_IDLE_DEAD] = {
2178 .name = "idle:dead",
2179 },
2180 /*
2181 * Last state before CPU enters the idle loop to die. Transient state
2182 * for synchronization.
2183 */
2184 [CPUHP_AP_OFFLINE] = {
2185 .name = "ap:offline",
2186 .cant_stop = true,
2187 },
2188 /* First state is scheduler control. Interrupts are disabled */
2189 [CPUHP_AP_SCHED_STARTING] = {
2190 .name = "sched:starting",
2191 .startup.single = sched_cpu_starting,
2192 .teardown.single = sched_cpu_dying,
2193 },
2194 [CPUHP_AP_RCUTREE_DYING] = {
2195 .name = "RCU/tree:dying",
2196 .startup.single = NULL,
2197 .teardown.single = rcutree_dying_cpu,
2198 },
2199 [CPUHP_AP_SMPCFD_DYING] = {
2200 .name = "smpcfd:dying",
2201 .startup.single = NULL,
2202 .teardown.single = smpcfd_dying_cpu,
2203 },
2204 [CPUHP_AP_HRTIMERS_DYING] = {
2205 .name = "hrtimers:dying",
2206 .startup.single = NULL,
2207 .teardown.single = hrtimers_cpu_dying,
2208 },
2209
2210 /* Entry state on starting. Interrupts enabled from here on. Transient
2211 * state for synchronsization */
2212 [CPUHP_AP_ONLINE] = {
2213 .name = "ap:online",
2214 },
2215 /*
2216 * Handled on control processor until the plugged processor manages
2217 * this itself.
2218 */
2219 [CPUHP_TEARDOWN_CPU] = {
2220 .name = "cpu:teardown",
2221 .startup.single = NULL,
2222 .teardown.single = takedown_cpu,
2223 .cant_stop = true,
2224 },
2225
2226 [CPUHP_AP_SCHED_WAIT_EMPTY] = {
2227 .name = "sched:waitempty",
2228 .startup.single = NULL,
2229 .teardown.single = sched_cpu_wait_empty,
2230 },
2231
2232 /* Handle smpboot threads park/unpark */
2233 [CPUHP_AP_SMPBOOT_THREADS] = {
2234 .name = "smpboot/threads:online",
2235 .startup.single = smpboot_unpark_threads,
2236 .teardown.single = smpboot_park_threads,
2237 },
2238 [CPUHP_AP_IRQ_AFFINITY_ONLINE] = {
2239 .name = "irq/affinity:online",
2240 .startup.single = irq_affinity_online_cpu,
2241 .teardown.single = NULL,
2242 },
2243 [CPUHP_AP_PERF_ONLINE] = {
2244 .name = "perf:online",
2245 .startup.single = perf_event_init_cpu,
2246 .teardown.single = perf_event_exit_cpu,
2247 },
2248 [CPUHP_AP_WATCHDOG_ONLINE] = {
2249 .name = "lockup_detector:online",
2250 .startup.single = lockup_detector_online_cpu,
2251 .teardown.single = lockup_detector_offline_cpu,
2252 },
2253 [CPUHP_AP_WORKQUEUE_ONLINE] = {
2254 .name = "workqueue:online",
2255 .startup.single = workqueue_online_cpu,
2256 .teardown.single = workqueue_offline_cpu,
2257 },
2258 [CPUHP_AP_RANDOM_ONLINE] = {
2259 .name = "random:online",
2260 .startup.single = random_online_cpu,
2261 .teardown.single = NULL,
2262 },
2263 [CPUHP_AP_RCUTREE_ONLINE] = {
2264 .name = "RCU/tree:online",
2265 .startup.single = rcutree_online_cpu,
2266 .teardown.single = rcutree_offline_cpu,
2267 },
2268 #endif
2269 /*
2270 * The dynamically registered state space is here
2271 */
2272
2273 #ifdef CONFIG_SMP
2274 /* Last state is scheduler control setting the cpu active */
2275 [CPUHP_AP_ACTIVE] = {
2276 .name = "sched:active",
2277 .startup.single = sched_cpu_activate,
2278 .teardown.single = sched_cpu_deactivate,
2279 },
2280 #endif
2281
2282 /* CPU is fully up and running. */
2283 [CPUHP_ONLINE] = {
2284 .name = "online",
2285 .startup.single = NULL,
2286 .teardown.single = NULL,
2287 },
2288 };
2289
2290 /* Sanity check for callbacks */
cpuhp_cb_check(enum cpuhp_state state)2291 static int cpuhp_cb_check(enum cpuhp_state state)
2292 {
2293 if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
2294 return -EINVAL;
2295 return 0;
2296 }
2297
2298 /*
2299 * Returns a free for dynamic slot assignment of the Online state. The states
2300 * are protected by the cpuhp_slot_states mutex and an empty slot is identified
2301 * by having no name assigned.
2302 */
cpuhp_reserve_state(enum cpuhp_state state)2303 static int cpuhp_reserve_state(enum cpuhp_state state)
2304 {
2305 enum cpuhp_state i, end;
2306 struct cpuhp_step *step;
2307
2308 switch (state) {
2309 case CPUHP_AP_ONLINE_DYN:
2310 step = cpuhp_hp_states + CPUHP_AP_ONLINE_DYN;
2311 end = CPUHP_AP_ONLINE_DYN_END;
2312 break;
2313 case CPUHP_BP_PREPARE_DYN:
2314 step = cpuhp_hp_states + CPUHP_BP_PREPARE_DYN;
2315 end = CPUHP_BP_PREPARE_DYN_END;
2316 break;
2317 default:
2318 return -EINVAL;
2319 }
2320
2321 for (i = state; i <= end; i++, step++) {
2322 if (!step->name)
2323 return i;
2324 }
2325 WARN(1, "No more dynamic states available for CPU hotplug\n");
2326 return -ENOSPC;
2327 }
2328
cpuhp_store_callbacks(enum cpuhp_state state,const char * name,int (* startup)(unsigned int cpu),int (* teardown)(unsigned int cpu),bool multi_instance)2329 static int cpuhp_store_callbacks(enum cpuhp_state state, const char *name,
2330 int (*startup)(unsigned int cpu),
2331 int (*teardown)(unsigned int cpu),
2332 bool multi_instance)
2333 {
2334 /* (Un)Install the callbacks for further cpu hotplug operations */
2335 struct cpuhp_step *sp;
2336 int ret = 0;
2337
2338 /*
2339 * If name is NULL, then the state gets removed.
2340 *
2341 * CPUHP_AP_ONLINE_DYN and CPUHP_BP_PREPARE_DYN are handed out on
2342 * the first allocation from these dynamic ranges, so the removal
2343 * would trigger a new allocation and clear the wrong (already
2344 * empty) state, leaving the callbacks of the to be cleared state
2345 * dangling, which causes wreckage on the next hotplug operation.
2346 */
2347 if (name && (state == CPUHP_AP_ONLINE_DYN ||
2348 state == CPUHP_BP_PREPARE_DYN)) {
2349 ret = cpuhp_reserve_state(state);
2350 if (ret < 0)
2351 return ret;
2352 state = ret;
2353 }
2354 sp = cpuhp_get_step(state);
2355 if (name && sp->name)
2356 return -EBUSY;
2357
2358 sp->startup.single = startup;
2359 sp->teardown.single = teardown;
2360 sp->name = name;
2361 sp->multi_instance = multi_instance;
2362 INIT_HLIST_HEAD(&sp->list);
2363 return ret;
2364 }
2365
cpuhp_get_teardown_cb(enum cpuhp_state state)2366 static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
2367 {
2368 return cpuhp_get_step(state)->teardown.single;
2369 }
2370
2371 /*
2372 * Call the startup/teardown function for a step either on the AP or
2373 * on the current CPU.
2374 */
cpuhp_issue_call(int cpu,enum cpuhp_state state,bool bringup,struct hlist_node * node)2375 static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup,
2376 struct hlist_node *node)
2377 {
2378 struct cpuhp_step *sp = cpuhp_get_step(state);
2379 int ret;
2380
2381 /*
2382 * If there's nothing to do, we done.
2383 * Relies on the union for multi_instance.
2384 */
2385 if (cpuhp_step_empty(bringup, sp))
2386 return 0;
2387 /*
2388 * The non AP bound callbacks can fail on bringup. On teardown
2389 * e.g. module removal we crash for now.
2390 */
2391 #ifdef CONFIG_SMP
2392 if (cpuhp_is_ap_state(state))
2393 ret = cpuhp_invoke_ap_callback(cpu, state, bringup, node);
2394 else
2395 ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
2396 #else
2397 ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
2398 #endif
2399 BUG_ON(ret && !bringup);
2400 return ret;
2401 }
2402
2403 /*
2404 * Called from __cpuhp_setup_state on a recoverable failure.
2405 *
2406 * Note: The teardown callbacks for rollback are not allowed to fail!
2407 */
cpuhp_rollback_install(int failedcpu,enum cpuhp_state state,struct hlist_node * node)2408 static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
2409 struct hlist_node *node)
2410 {
2411 int cpu;
2412
2413 /* Roll back the already executed steps on the other cpus */
2414 for_each_present_cpu(cpu) {
2415 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2416 int cpustate = st->state;
2417
2418 if (cpu >= failedcpu)
2419 break;
2420
2421 /* Did we invoke the startup call on that cpu ? */
2422 if (cpustate >= state)
2423 cpuhp_issue_call(cpu, state, false, node);
2424 }
2425 }
2426
__cpuhp_state_add_instance_cpuslocked(enum cpuhp_state state,struct hlist_node * node,bool invoke)2427 int __cpuhp_state_add_instance_cpuslocked(enum cpuhp_state state,
2428 struct hlist_node *node,
2429 bool invoke)
2430 {
2431 struct cpuhp_step *sp;
2432 int cpu;
2433 int ret;
2434
2435 lockdep_assert_cpus_held();
2436
2437 sp = cpuhp_get_step(state);
2438 if (sp->multi_instance == false)
2439 return -EINVAL;
2440
2441 mutex_lock(&cpuhp_state_mutex);
2442
2443 if (!invoke || !sp->startup.multi)
2444 goto add_node;
2445
2446 /*
2447 * Try to call the startup callback for each present cpu
2448 * depending on the hotplug state of the cpu.
2449 */
2450 for_each_present_cpu(cpu) {
2451 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2452 int cpustate = st->state;
2453
2454 if (cpustate < state)
2455 continue;
2456
2457 ret = cpuhp_issue_call(cpu, state, true, node);
2458 if (ret) {
2459 if (sp->teardown.multi)
2460 cpuhp_rollback_install(cpu, state, node);
2461 goto unlock;
2462 }
2463 }
2464 add_node:
2465 ret = 0;
2466 hlist_add_head(node, &sp->list);
2467 unlock:
2468 mutex_unlock(&cpuhp_state_mutex);
2469 return ret;
2470 }
2471
__cpuhp_state_add_instance(enum cpuhp_state state,struct hlist_node * node,bool invoke)2472 int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
2473 bool invoke)
2474 {
2475 int ret;
2476
2477 cpus_read_lock();
2478 ret = __cpuhp_state_add_instance_cpuslocked(state, node, invoke);
2479 cpus_read_unlock();
2480 return ret;
2481 }
2482 EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);
2483
2484 /**
2485 * __cpuhp_setup_state_cpuslocked - Setup the callbacks for an hotplug machine state
2486 * @state: The state to setup
2487 * @name: Name of the step
2488 * @invoke: If true, the startup function is invoked for cpus where
2489 * cpu state >= @state
2490 * @startup: startup callback function
2491 * @teardown: teardown callback function
2492 * @multi_instance: State is set up for multiple instances which get
2493 * added afterwards.
2494 *
2495 * The caller needs to hold cpus read locked while calling this function.
2496 * Return:
2497 * On success:
2498 * Positive state number if @state is CPUHP_AP_ONLINE_DYN;
2499 * 0 for all other states
2500 * On failure: proper (negative) error code
2501 */
__cpuhp_setup_state_cpuslocked(enum cpuhp_state state,const char * name,bool invoke,int (* startup)(unsigned int cpu),int (* teardown)(unsigned int cpu),bool multi_instance)2502 int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state,
2503 const char *name, bool invoke,
2504 int (*startup)(unsigned int cpu),
2505 int (*teardown)(unsigned int cpu),
2506 bool multi_instance)
2507 {
2508 int cpu, ret = 0;
2509 bool dynstate;
2510
2511 lockdep_assert_cpus_held();
2512
2513 if (cpuhp_cb_check(state) || !name)
2514 return -EINVAL;
2515
2516 mutex_lock(&cpuhp_state_mutex);
2517
2518 ret = cpuhp_store_callbacks(state, name, startup, teardown,
2519 multi_instance);
2520
2521 dynstate = state == CPUHP_AP_ONLINE_DYN;
2522 if (ret > 0 && dynstate) {
2523 state = ret;
2524 ret = 0;
2525 }
2526
2527 if (ret || !invoke || !startup)
2528 goto out;
2529
2530 /*
2531 * Try to call the startup callback for each present cpu
2532 * depending on the hotplug state of the cpu.
2533 */
2534 for_each_present_cpu(cpu) {
2535 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2536 int cpustate = st->state;
2537
2538 if (cpustate < state)
2539 continue;
2540
2541 ret = cpuhp_issue_call(cpu, state, true, NULL);
2542 if (ret) {
2543 if (teardown)
2544 cpuhp_rollback_install(cpu, state, NULL);
2545 cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
2546 goto out;
2547 }
2548 }
2549 out:
2550 mutex_unlock(&cpuhp_state_mutex);
2551 /*
2552 * If the requested state is CPUHP_AP_ONLINE_DYN, return the
2553 * dynamically allocated state in case of success.
2554 */
2555 if (!ret && dynstate)
2556 return state;
2557 return ret;
2558 }
2559 EXPORT_SYMBOL(__cpuhp_setup_state_cpuslocked);
2560
__cpuhp_setup_state(enum cpuhp_state state,const char * name,bool invoke,int (* startup)(unsigned int cpu),int (* teardown)(unsigned int cpu),bool multi_instance)2561 int __cpuhp_setup_state(enum cpuhp_state state,
2562 const char *name, bool invoke,
2563 int (*startup)(unsigned int cpu),
2564 int (*teardown)(unsigned int cpu),
2565 bool multi_instance)
2566 {
2567 int ret;
2568
2569 cpus_read_lock();
2570 ret = __cpuhp_setup_state_cpuslocked(state, name, invoke, startup,
2571 teardown, multi_instance);
2572 cpus_read_unlock();
2573 return ret;
2574 }
2575 EXPORT_SYMBOL(__cpuhp_setup_state);
2576
__cpuhp_state_remove_instance(enum cpuhp_state state,struct hlist_node * node,bool invoke)2577 int __cpuhp_state_remove_instance(enum cpuhp_state state,
2578 struct hlist_node *node, bool invoke)
2579 {
2580 struct cpuhp_step *sp = cpuhp_get_step(state);
2581 int cpu;
2582
2583 BUG_ON(cpuhp_cb_check(state));
2584
2585 if (!sp->multi_instance)
2586 return -EINVAL;
2587
2588 cpus_read_lock();
2589 mutex_lock(&cpuhp_state_mutex);
2590
2591 if (!invoke || !cpuhp_get_teardown_cb(state))
2592 goto remove;
2593 /*
2594 * Call the teardown callback for each present cpu depending
2595 * on the hotplug state of the cpu. This function is not
2596 * allowed to fail currently!
2597 */
2598 for_each_present_cpu(cpu) {
2599 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2600 int cpustate = st->state;
2601
2602 if (cpustate >= state)
2603 cpuhp_issue_call(cpu, state, false, node);
2604 }
2605
2606 remove:
2607 hlist_del(node);
2608 mutex_unlock(&cpuhp_state_mutex);
2609 cpus_read_unlock();
2610
2611 return 0;
2612 }
2613 EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance);
2614
2615 /**
2616 * __cpuhp_remove_state_cpuslocked - Remove the callbacks for an hotplug machine state
2617 * @state: The state to remove
2618 * @invoke: If true, the teardown function is invoked for cpus where
2619 * cpu state >= @state
2620 *
2621 * The caller needs to hold cpus read locked while calling this function.
2622 * The teardown callback is currently not allowed to fail. Think
2623 * about module removal!
2624 */
__cpuhp_remove_state_cpuslocked(enum cpuhp_state state,bool invoke)2625 void __cpuhp_remove_state_cpuslocked(enum cpuhp_state state, bool invoke)
2626 {
2627 struct cpuhp_step *sp = cpuhp_get_step(state);
2628 int cpu;
2629
2630 BUG_ON(cpuhp_cb_check(state));
2631
2632 lockdep_assert_cpus_held();
2633
2634 mutex_lock(&cpuhp_state_mutex);
2635 if (sp->multi_instance) {
2636 WARN(!hlist_empty(&sp->list),
2637 "Error: Removing state %d which has instances left.\n",
2638 state);
2639 goto remove;
2640 }
2641
2642 if (!invoke || !cpuhp_get_teardown_cb(state))
2643 goto remove;
2644
2645 /*
2646 * Call the teardown callback for each present cpu depending
2647 * on the hotplug state of the cpu. This function is not
2648 * allowed to fail currently!
2649 */
2650 for_each_present_cpu(cpu) {
2651 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2652 int cpustate = st->state;
2653
2654 if (cpustate >= state)
2655 cpuhp_issue_call(cpu, state, false, NULL);
2656 }
2657 remove:
2658 cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
2659 mutex_unlock(&cpuhp_state_mutex);
2660 }
2661 EXPORT_SYMBOL(__cpuhp_remove_state_cpuslocked);
2662
__cpuhp_remove_state(enum cpuhp_state state,bool invoke)2663 void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
2664 {
2665 cpus_read_lock();
2666 __cpuhp_remove_state_cpuslocked(state, invoke);
2667 cpus_read_unlock();
2668 }
2669 EXPORT_SYMBOL(__cpuhp_remove_state);
2670
2671 #ifdef CONFIG_HOTPLUG_SMT
cpuhp_offline_cpu_device(unsigned int cpu)2672 static void cpuhp_offline_cpu_device(unsigned int cpu)
2673 {
2674 struct device *dev = get_cpu_device(cpu);
2675
2676 dev->offline = true;
2677 /* Tell user space about the state change */
2678 kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
2679 }
2680
cpuhp_online_cpu_device(unsigned int cpu)2681 static void cpuhp_online_cpu_device(unsigned int cpu)
2682 {
2683 struct device *dev = get_cpu_device(cpu);
2684
2685 dev->offline = false;
2686 /* Tell user space about the state change */
2687 kobject_uevent(&dev->kobj, KOBJ_ONLINE);
2688 }
2689
cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)2690 int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
2691 {
2692 int cpu, ret = 0;
2693
2694 cpu_maps_update_begin();
2695 for_each_online_cpu(cpu) {
2696 if (topology_is_primary_thread(cpu))
2697 continue;
2698 /*
2699 * Disable can be called with CPU_SMT_ENABLED when changing
2700 * from a higher to lower number of SMT threads per core.
2701 */
2702 if (ctrlval == CPU_SMT_ENABLED && cpu_smt_thread_allowed(cpu))
2703 continue;
2704 ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
2705 if (ret)
2706 break;
2707 /*
2708 * As this needs to hold the cpu maps lock it's impossible
2709 * to call device_offline() because that ends up calling
2710 * cpu_down() which takes cpu maps lock. cpu maps lock
2711 * needs to be held as this might race against in kernel
2712 * abusers of the hotplug machinery (thermal management).
2713 *
2714 * So nothing would update device:offline state. That would
2715 * leave the sysfs entry stale and prevent onlining after
2716 * smt control has been changed to 'off' again. This is
2717 * called under the sysfs hotplug lock, so it is properly
2718 * serialized against the regular offline usage.
2719 */
2720 cpuhp_offline_cpu_device(cpu);
2721 }
2722 if (!ret)
2723 cpu_smt_control = ctrlval;
2724 cpu_maps_update_done();
2725 return ret;
2726 }
2727
cpuhp_smt_enable(void)2728 int cpuhp_smt_enable(void)
2729 {
2730 int cpu, ret = 0;
2731
2732 cpu_maps_update_begin();
2733 cpu_smt_control = CPU_SMT_ENABLED;
2734 for_each_present_cpu(cpu) {
2735 /* Skip online CPUs and CPUs on offline nodes */
2736 if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))
2737 continue;
2738 if (!cpu_smt_thread_allowed(cpu))
2739 continue;
2740 ret = _cpu_up(cpu, 0, CPUHP_ONLINE);
2741 if (ret)
2742 break;
2743 /* See comment in cpuhp_smt_disable() */
2744 cpuhp_online_cpu_device(cpu);
2745 }
2746 cpu_maps_update_done();
2747 return ret;
2748 }
2749 #endif
2750
2751 #if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
state_show(struct device * dev,struct device_attribute * attr,char * buf)2752 static ssize_t state_show(struct device *dev,
2753 struct device_attribute *attr, char *buf)
2754 {
2755 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2756
2757 return sprintf(buf, "%d\n", st->state);
2758 }
2759 static DEVICE_ATTR_RO(state);
2760
target_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)2761 static ssize_t target_store(struct device *dev, struct device_attribute *attr,
2762 const char *buf, size_t count)
2763 {
2764 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2765 struct cpuhp_step *sp;
2766 int target, ret;
2767
2768 ret = kstrtoint(buf, 10, &target);
2769 if (ret)
2770 return ret;
2771
2772 #ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
2773 if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
2774 return -EINVAL;
2775 #else
2776 if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
2777 return -EINVAL;
2778 #endif
2779
2780 ret = lock_device_hotplug_sysfs();
2781 if (ret)
2782 return ret;
2783
2784 mutex_lock(&cpuhp_state_mutex);
2785 sp = cpuhp_get_step(target);
2786 ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
2787 mutex_unlock(&cpuhp_state_mutex);
2788 if (ret)
2789 goto out;
2790
2791 if (st->state < target)
2792 ret = cpu_up(dev->id, target);
2793 else if (st->state > target)
2794 ret = cpu_down(dev->id, target);
2795 else if (WARN_ON(st->target != target))
2796 st->target = target;
2797 out:
2798 unlock_device_hotplug();
2799 return ret ? ret : count;
2800 }
2801
target_show(struct device * dev,struct device_attribute * attr,char * buf)2802 static ssize_t target_show(struct device *dev,
2803 struct device_attribute *attr, char *buf)
2804 {
2805 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2806
2807 return sprintf(buf, "%d\n", st->target);
2808 }
2809 static DEVICE_ATTR_RW(target);
2810
fail_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)2811 static ssize_t fail_store(struct device *dev, struct device_attribute *attr,
2812 const char *buf, size_t count)
2813 {
2814 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2815 struct cpuhp_step *sp;
2816 int fail, ret;
2817
2818 ret = kstrtoint(buf, 10, &fail);
2819 if (ret)
2820 return ret;
2821
2822 if (fail == CPUHP_INVALID) {
2823 st->fail = fail;
2824 return count;
2825 }
2826
2827 if (fail < CPUHP_OFFLINE || fail > CPUHP_ONLINE)
2828 return -EINVAL;
2829
2830 /*
2831 * Cannot fail STARTING/DYING callbacks.
2832 */
2833 if (cpuhp_is_atomic_state(fail))
2834 return -EINVAL;
2835
2836 /*
2837 * DEAD callbacks cannot fail...
2838 * ... neither can CPUHP_BRINGUP_CPU during hotunplug. The latter
2839 * triggering STARTING callbacks, a failure in this state would
2840 * hinder rollback.
2841 */
2842 if (fail <= CPUHP_BRINGUP_CPU && st->state > CPUHP_BRINGUP_CPU)
2843 return -EINVAL;
2844
2845 /*
2846 * Cannot fail anything that doesn't have callbacks.
2847 */
2848 mutex_lock(&cpuhp_state_mutex);
2849 sp = cpuhp_get_step(fail);
2850 if (!sp->startup.single && !sp->teardown.single)
2851 ret = -EINVAL;
2852 mutex_unlock(&cpuhp_state_mutex);
2853 if (ret)
2854 return ret;
2855
2856 st->fail = fail;
2857
2858 return count;
2859 }
2860
fail_show(struct device * dev,struct device_attribute * attr,char * buf)2861 static ssize_t fail_show(struct device *dev,
2862 struct device_attribute *attr, char *buf)
2863 {
2864 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2865
2866 return sprintf(buf, "%d\n", st->fail);
2867 }
2868
2869 static DEVICE_ATTR_RW(fail);
2870
2871 static struct attribute *cpuhp_cpu_attrs[] = {
2872 &dev_attr_state.attr,
2873 &dev_attr_target.attr,
2874 &dev_attr_fail.attr,
2875 NULL
2876 };
2877
2878 static const struct attribute_group cpuhp_cpu_attr_group = {
2879 .attrs = cpuhp_cpu_attrs,
2880 .name = "hotplug",
2881 NULL
2882 };
2883
states_show(struct device * dev,struct device_attribute * attr,char * buf)2884 static ssize_t states_show(struct device *dev,
2885 struct device_attribute *attr, char *buf)
2886 {
2887 ssize_t cur, res = 0;
2888 int i;
2889
2890 mutex_lock(&cpuhp_state_mutex);
2891 for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
2892 struct cpuhp_step *sp = cpuhp_get_step(i);
2893
2894 if (sp->name) {
2895 cur = sprintf(buf, "%3d: %s\n", i, sp->name);
2896 buf += cur;
2897 res += cur;
2898 }
2899 }
2900 mutex_unlock(&cpuhp_state_mutex);
2901 return res;
2902 }
2903 static DEVICE_ATTR_RO(states);
2904
2905 static struct attribute *cpuhp_cpu_root_attrs[] = {
2906 &dev_attr_states.attr,
2907 NULL
2908 };
2909
2910 static const struct attribute_group cpuhp_cpu_root_attr_group = {
2911 .attrs = cpuhp_cpu_root_attrs,
2912 .name = "hotplug",
2913 NULL
2914 };
2915
2916 #ifdef CONFIG_HOTPLUG_SMT
2917
cpu_smt_num_threads_valid(unsigned int threads)2918 static bool cpu_smt_num_threads_valid(unsigned int threads)
2919 {
2920 if (IS_ENABLED(CONFIG_SMT_NUM_THREADS_DYNAMIC))
2921 return threads >= 1 && threads <= cpu_smt_max_threads;
2922 return threads == 1 || threads == cpu_smt_max_threads;
2923 }
2924
2925 static ssize_t
__store_smt_control(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)2926 __store_smt_control(struct device *dev, struct device_attribute *attr,
2927 const char *buf, size_t count)
2928 {
2929 int ctrlval, ret, num_threads, orig_threads;
2930 bool force_off;
2931
2932 if (cpu_smt_control == CPU_SMT_FORCE_DISABLED)
2933 return -EPERM;
2934
2935 if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
2936 return -ENODEV;
2937
2938 if (sysfs_streq(buf, "on")) {
2939 ctrlval = CPU_SMT_ENABLED;
2940 num_threads = cpu_smt_max_threads;
2941 } else if (sysfs_streq(buf, "off")) {
2942 ctrlval = CPU_SMT_DISABLED;
2943 num_threads = 1;
2944 } else if (sysfs_streq(buf, "forceoff")) {
2945 ctrlval = CPU_SMT_FORCE_DISABLED;
2946 num_threads = 1;
2947 } else if (kstrtoint(buf, 10, &num_threads) == 0) {
2948 if (num_threads == 1)
2949 ctrlval = CPU_SMT_DISABLED;
2950 else if (cpu_smt_num_threads_valid(num_threads))
2951 ctrlval = CPU_SMT_ENABLED;
2952 else
2953 return -EINVAL;
2954 } else {
2955 return -EINVAL;
2956 }
2957
2958 ret = lock_device_hotplug_sysfs();
2959 if (ret)
2960 return ret;
2961
2962 orig_threads = cpu_smt_num_threads;
2963 cpu_smt_num_threads = num_threads;
2964
2965 force_off = ctrlval != cpu_smt_control && ctrlval == CPU_SMT_FORCE_DISABLED;
2966
2967 if (num_threads > orig_threads)
2968 ret = cpuhp_smt_enable();
2969 else if (num_threads < orig_threads || force_off)
2970 ret = cpuhp_smt_disable(ctrlval);
2971
2972 unlock_device_hotplug();
2973 return ret ? ret : count;
2974 }
2975
2976 #else /* !CONFIG_HOTPLUG_SMT */
2977 static ssize_t
__store_smt_control(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)2978 __store_smt_control(struct device *dev, struct device_attribute *attr,
2979 const char *buf, size_t count)
2980 {
2981 return -ENODEV;
2982 }
2983 #endif /* CONFIG_HOTPLUG_SMT */
2984
2985 static const char *smt_states[] = {
2986 [CPU_SMT_ENABLED] = "on",
2987 [CPU_SMT_DISABLED] = "off",
2988 [CPU_SMT_FORCE_DISABLED] = "forceoff",
2989 [CPU_SMT_NOT_SUPPORTED] = "notsupported",
2990 [CPU_SMT_NOT_IMPLEMENTED] = "notimplemented",
2991 };
2992
control_show(struct device * dev,struct device_attribute * attr,char * buf)2993 static ssize_t control_show(struct device *dev,
2994 struct device_attribute *attr, char *buf)
2995 {
2996 const char *state = smt_states[cpu_smt_control];
2997
2998 #ifdef CONFIG_HOTPLUG_SMT
2999 /*
3000 * If SMT is enabled but not all threads are enabled then show the
3001 * number of threads. If all threads are enabled show "on". Otherwise
3002 * show the state name.
3003 */
3004 if (cpu_smt_control == CPU_SMT_ENABLED &&
3005 cpu_smt_num_threads != cpu_smt_max_threads)
3006 return sysfs_emit(buf, "%d\n", cpu_smt_num_threads);
3007 #endif
3008
3009 return snprintf(buf, PAGE_SIZE - 2, "%s\n", state);
3010 }
3011
control_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)3012 static ssize_t control_store(struct device *dev, struct device_attribute *attr,
3013 const char *buf, size_t count)
3014 {
3015 return __store_smt_control(dev, attr, buf, count);
3016 }
3017 static DEVICE_ATTR_RW(control);
3018
active_show(struct device * dev,struct device_attribute * attr,char * buf)3019 static ssize_t active_show(struct device *dev,
3020 struct device_attribute *attr, char *buf)
3021 {
3022 return snprintf(buf, PAGE_SIZE - 2, "%d\n", sched_smt_active());
3023 }
3024 static DEVICE_ATTR_RO(active);
3025
3026 static struct attribute *cpuhp_smt_attrs[] = {
3027 &dev_attr_control.attr,
3028 &dev_attr_active.attr,
3029 NULL
3030 };
3031
3032 static const struct attribute_group cpuhp_smt_attr_group = {
3033 .attrs = cpuhp_smt_attrs,
3034 .name = "smt",
3035 NULL
3036 };
3037
cpu_smt_sysfs_init(void)3038 static int __init cpu_smt_sysfs_init(void)
3039 {
3040 struct device *dev_root;
3041 int ret = -ENODEV;
3042
3043 dev_root = bus_get_dev_root(&cpu_subsys);
3044 if (dev_root) {
3045 ret = sysfs_create_group(&dev_root->kobj, &cpuhp_smt_attr_group);
3046 put_device(dev_root);
3047 }
3048 return ret;
3049 }
3050
cpuhp_sysfs_init(void)3051 static int __init cpuhp_sysfs_init(void)
3052 {
3053 struct device *dev_root;
3054 int cpu, ret;
3055
3056 ret = cpu_smt_sysfs_init();
3057 if (ret)
3058 return ret;
3059
3060 dev_root = bus_get_dev_root(&cpu_subsys);
3061 if (dev_root) {
3062 ret = sysfs_create_group(&dev_root->kobj, &cpuhp_cpu_root_attr_group);
3063 put_device(dev_root);
3064 if (ret)
3065 return ret;
3066 }
3067
3068 for_each_possible_cpu(cpu) {
3069 struct device *dev = get_cpu_device(cpu);
3070
3071 if (!dev)
3072 continue;
3073 ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
3074 if (ret)
3075 return ret;
3076 }
3077 return 0;
3078 }
3079 device_initcall(cpuhp_sysfs_init);
3080 #endif /* CONFIG_SYSFS && CONFIG_HOTPLUG_CPU */
3081
3082 /*
3083 * cpu_bit_bitmap[] is a special, "compressed" data structure that
3084 * represents all NR_CPUS bits binary values of 1<<nr.
3085 *
3086 * It is used by cpumask_of() to get a constant address to a CPU
3087 * mask value that has a single bit set only.
3088 */
3089
3090 /* cpu_bit_bitmap[0] is empty - so we can back into it */
3091 #define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
3092 #define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
3093 #define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
3094 #define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
3095
3096 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
3097
3098 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
3099 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
3100 #if BITS_PER_LONG > 32
3101 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
3102 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
3103 #endif
3104 };
3105 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
3106
3107 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
3108 EXPORT_SYMBOL(cpu_all_bits);
3109
3110 #ifdef CONFIG_INIT_ALL_POSSIBLE
3111 struct cpumask __cpu_possible_mask __read_mostly
3112 = {CPU_BITS_ALL};
3113 #else
3114 struct cpumask __cpu_possible_mask __read_mostly;
3115 #endif
3116 EXPORT_SYMBOL(__cpu_possible_mask);
3117
3118 struct cpumask __cpu_online_mask __read_mostly;
3119 EXPORT_SYMBOL(__cpu_online_mask);
3120
3121 struct cpumask __cpu_present_mask __read_mostly;
3122 EXPORT_SYMBOL(__cpu_present_mask);
3123
3124 struct cpumask __cpu_active_mask __read_mostly;
3125 EXPORT_SYMBOL(__cpu_active_mask);
3126
3127 struct cpumask __cpu_dying_mask __read_mostly;
3128 EXPORT_SYMBOL(__cpu_dying_mask);
3129
3130 atomic_t __num_online_cpus __read_mostly;
3131 EXPORT_SYMBOL(__num_online_cpus);
3132
init_cpu_present(const struct cpumask * src)3133 void init_cpu_present(const struct cpumask *src)
3134 {
3135 cpumask_copy(&__cpu_present_mask, src);
3136 }
3137
init_cpu_possible(const struct cpumask * src)3138 void init_cpu_possible(const struct cpumask *src)
3139 {
3140 cpumask_copy(&__cpu_possible_mask, src);
3141 }
3142
init_cpu_online(const struct cpumask * src)3143 void init_cpu_online(const struct cpumask *src)
3144 {
3145 cpumask_copy(&__cpu_online_mask, src);
3146 }
3147
set_cpu_online(unsigned int cpu,bool online)3148 void set_cpu_online(unsigned int cpu, bool online)
3149 {
3150 /*
3151 * atomic_inc/dec() is required to handle the horrid abuse of this
3152 * function by the reboot and kexec code which invoke it from
3153 * IPI/NMI broadcasts when shutting down CPUs. Invocation from
3154 * regular CPU hotplug is properly serialized.
3155 *
3156 * Note, that the fact that __num_online_cpus is of type atomic_t
3157 * does not protect readers which are not serialized against
3158 * concurrent hotplug operations.
3159 */
3160 if (online) {
3161 if (!cpumask_test_and_set_cpu(cpu, &__cpu_online_mask))
3162 atomic_inc(&__num_online_cpus);
3163 } else {
3164 if (cpumask_test_and_clear_cpu(cpu, &__cpu_online_mask))
3165 atomic_dec(&__num_online_cpus);
3166 }
3167 }
3168
3169 /*
3170 * Activate the first processor.
3171 */
boot_cpu_init(void)3172 void __init boot_cpu_init(void)
3173 {
3174 int cpu = smp_processor_id();
3175
3176 /* Mark the boot cpu "present", "online" etc for SMP and UP case */
3177 set_cpu_online(cpu, true);
3178 set_cpu_active(cpu, true);
3179 set_cpu_present(cpu, true);
3180 set_cpu_possible(cpu, true);
3181
3182 #ifdef CONFIG_SMP
3183 __boot_cpu_id = cpu;
3184 #endif
3185 }
3186
3187 /*
3188 * Must be called _AFTER_ setting up the per_cpu areas
3189 */
boot_cpu_hotplug_init(void)3190 void __init boot_cpu_hotplug_init(void)
3191 {
3192 #ifdef CONFIG_SMP
3193 cpumask_set_cpu(smp_processor_id(), &cpus_booted_once_mask);
3194 atomic_set(this_cpu_ptr(&cpuhp_state.ap_sync_state), SYNC_STATE_ONLINE);
3195 #endif
3196 this_cpu_write(cpuhp_state.state, CPUHP_ONLINE);
3197 this_cpu_write(cpuhp_state.target, CPUHP_ONLINE);
3198 }
3199
3200 /*
3201 * These are used for a global "mitigations=" cmdline option for toggling
3202 * optional CPU mitigations.
3203 */
3204 enum cpu_mitigations {
3205 CPU_MITIGATIONS_OFF,
3206 CPU_MITIGATIONS_AUTO,
3207 CPU_MITIGATIONS_AUTO_NOSMT,
3208 };
3209
3210 static enum cpu_mitigations cpu_mitigations __ro_after_init =
3211 CPU_MITIGATIONS_AUTO;
3212
mitigations_parse_cmdline(char * arg)3213 static int __init mitigations_parse_cmdline(char *arg)
3214 {
3215 if (!strcmp(arg, "off"))
3216 cpu_mitigations = CPU_MITIGATIONS_OFF;
3217 else if (!strcmp(arg, "auto"))
3218 cpu_mitigations = CPU_MITIGATIONS_AUTO;
3219 else if (!strcmp(arg, "auto,nosmt"))
3220 cpu_mitigations = CPU_MITIGATIONS_AUTO_NOSMT;
3221 else
3222 pr_crit("Unsupported mitigations=%s, system may still be vulnerable\n",
3223 arg);
3224
3225 return 0;
3226 }
3227 early_param("mitigations", mitigations_parse_cmdline);
3228
3229 /* mitigations=off */
cpu_mitigations_off(void)3230 bool cpu_mitigations_off(void)
3231 {
3232 return cpu_mitigations == CPU_MITIGATIONS_OFF;
3233 }
3234 EXPORT_SYMBOL_GPL(cpu_mitigations_off);
3235
3236 /* mitigations=auto,nosmt */
cpu_mitigations_auto_nosmt(void)3237 bool cpu_mitigations_auto_nosmt(void)
3238 {
3239 return cpu_mitigations == CPU_MITIGATIONS_AUTO_NOSMT;
3240 }
3241 EXPORT_SYMBOL_GPL(cpu_mitigations_auto_nosmt);
3242