Merge branch 'for-4.7-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj...
[deliverable/linux.git] / arch / x86 / kernel / kvm.c
1 /*
2 * KVM paravirt_ops implementation
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
17 *
18 * Copyright (C) 2007, Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
19 * Copyright IBM Corporation, 2007
20 * Authors: Anthony Liguori <aliguori@us.ibm.com>
21 */
22
23 #include <linux/context_tracking.h>
24 #include <linux/module.h>
25 #include <linux/kernel.h>
26 #include <linux/kvm_para.h>
27 #include <linux/cpu.h>
28 #include <linux/mm.h>
29 #include <linux/highmem.h>
30 #include <linux/hardirq.h>
31 #include <linux/notifier.h>
32 #include <linux/reboot.h>
33 #include <linux/hash.h>
34 #include <linux/sched.h>
35 #include <linux/slab.h>
36 #include <linux/kprobes.h>
37 #include <linux/debugfs.h>
38 #include <linux/nmi.h>
39 #include <linux/swait.h>
40 #include <asm/timer.h>
41 #include <asm/cpu.h>
42 #include <asm/traps.h>
43 #include <asm/desc.h>
44 #include <asm/tlbflush.h>
45 #include <asm/idle.h>
46 #include <asm/apic.h>
47 #include <asm/apicdef.h>
48 #include <asm/hypervisor.h>
49 #include <asm/kvm_guest.h>
50
51 static int kvmapf = 1;
52
53 static int parse_no_kvmapf(char *arg)
54 {
55 kvmapf = 0;
56 return 0;
57 }
58
59 early_param("no-kvmapf", parse_no_kvmapf);
60
61 static int steal_acc = 1;
62 static int parse_no_stealacc(char *arg)
63 {
64 steal_acc = 0;
65 return 0;
66 }
67
68 early_param("no-steal-acc", parse_no_stealacc);
69
70 static int kvmclock_vsyscall = 1;
71 static int parse_no_kvmclock_vsyscall(char *arg)
72 {
73 kvmclock_vsyscall = 0;
74 return 0;
75 }
76
77 early_param("no-kvmclock-vsyscall", parse_no_kvmclock_vsyscall);
78
79 static DEFINE_PER_CPU(struct kvm_vcpu_pv_apf_data, apf_reason) __aligned(64);
80 static DEFINE_PER_CPU(struct kvm_steal_time, steal_time) __aligned(64);
81 static int has_steal_clock = 0;
82
83 /*
84 * No need for any "IO delay" on KVM
85 */
86 static void kvm_io_delay(void)
87 {
88 }
89
90 #define KVM_TASK_SLEEP_HASHBITS 8
91 #define KVM_TASK_SLEEP_HASHSIZE (1<<KVM_TASK_SLEEP_HASHBITS)
92
93 struct kvm_task_sleep_node {
94 struct hlist_node link;
95 struct swait_queue_head wq;
96 u32 token;
97 int cpu;
98 bool halted;
99 };
100
101 static struct kvm_task_sleep_head {
102 raw_spinlock_t lock;
103 struct hlist_head list;
104 } async_pf_sleepers[KVM_TASK_SLEEP_HASHSIZE];
105
106 static struct kvm_task_sleep_node *_find_apf_task(struct kvm_task_sleep_head *b,
107 u32 token)
108 {
109 struct hlist_node *p;
110
111 hlist_for_each(p, &b->list) {
112 struct kvm_task_sleep_node *n =
113 hlist_entry(p, typeof(*n), link);
114 if (n->token == token)
115 return n;
116 }
117
118 return NULL;
119 }
120
121 void kvm_async_pf_task_wait(u32 token)
122 {
123 u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS);
124 struct kvm_task_sleep_head *b = &async_pf_sleepers[key];
125 struct kvm_task_sleep_node n, *e;
126 DECLARE_SWAITQUEUE(wait);
127
128 rcu_irq_enter();
129
130 raw_spin_lock(&b->lock);
131 e = _find_apf_task(b, token);
132 if (e) {
133 /* dummy entry exist -> wake up was delivered ahead of PF */
134 hlist_del(&e->link);
135 kfree(e);
136 raw_spin_unlock(&b->lock);
137
138 rcu_irq_exit();
139 return;
140 }
141
142 n.token = token;
143 n.cpu = smp_processor_id();
144 n.halted = is_idle_task(current) || preempt_count() > 1;
145 init_swait_queue_head(&n.wq);
146 hlist_add_head(&n.link, &b->list);
147 raw_spin_unlock(&b->lock);
148
149 for (;;) {
150 if (!n.halted)
151 prepare_to_swait(&n.wq, &wait, TASK_UNINTERRUPTIBLE);
152 if (hlist_unhashed(&n.link))
153 break;
154
155 if (!n.halted) {
156 local_irq_enable();
157 schedule();
158 local_irq_disable();
159 } else {
160 /*
161 * We cannot reschedule. So halt.
162 */
163 rcu_irq_exit();
164 native_safe_halt();
165 rcu_irq_enter();
166 local_irq_disable();
167 }
168 }
169 if (!n.halted)
170 finish_swait(&n.wq, &wait);
171
172 rcu_irq_exit();
173 return;
174 }
175 EXPORT_SYMBOL_GPL(kvm_async_pf_task_wait);
176
177 static void apf_task_wake_one(struct kvm_task_sleep_node *n)
178 {
179 hlist_del_init(&n->link);
180 if (n->halted)
181 smp_send_reschedule(n->cpu);
182 else if (swait_active(&n->wq))
183 swake_up(&n->wq);
184 }
185
186 static void apf_task_wake_all(void)
187 {
188 int i;
189
190 for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++) {
191 struct hlist_node *p, *next;
192 struct kvm_task_sleep_head *b = &async_pf_sleepers[i];
193 raw_spin_lock(&b->lock);
194 hlist_for_each_safe(p, next, &b->list) {
195 struct kvm_task_sleep_node *n =
196 hlist_entry(p, typeof(*n), link);
197 if (n->cpu == smp_processor_id())
198 apf_task_wake_one(n);
199 }
200 raw_spin_unlock(&b->lock);
201 }
202 }
203
204 void kvm_async_pf_task_wake(u32 token)
205 {
206 u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS);
207 struct kvm_task_sleep_head *b = &async_pf_sleepers[key];
208 struct kvm_task_sleep_node *n;
209
210 if (token == ~0) {
211 apf_task_wake_all();
212 return;
213 }
214
215 again:
216 raw_spin_lock(&b->lock);
217 n = _find_apf_task(b, token);
218 if (!n) {
219 /*
220 * async PF was not yet handled.
221 * Add dummy entry for the token.
222 */
223 n = kzalloc(sizeof(*n), GFP_ATOMIC);
224 if (!n) {
225 /*
226 * Allocation failed! Busy wait while other cpu
227 * handles async PF.
228 */
229 raw_spin_unlock(&b->lock);
230 cpu_relax();
231 goto again;
232 }
233 n->token = token;
234 n->cpu = smp_processor_id();
235 init_swait_queue_head(&n->wq);
236 hlist_add_head(&n->link, &b->list);
237 } else
238 apf_task_wake_one(n);
239 raw_spin_unlock(&b->lock);
240 return;
241 }
242 EXPORT_SYMBOL_GPL(kvm_async_pf_task_wake);
243
244 u32 kvm_read_and_reset_pf_reason(void)
245 {
246 u32 reason = 0;
247
248 if (__this_cpu_read(apf_reason.enabled)) {
249 reason = __this_cpu_read(apf_reason.reason);
250 __this_cpu_write(apf_reason.reason, 0);
251 }
252
253 return reason;
254 }
255 EXPORT_SYMBOL_GPL(kvm_read_and_reset_pf_reason);
256 NOKPROBE_SYMBOL(kvm_read_and_reset_pf_reason);
257
258 dotraplinkage void
259 do_async_page_fault(struct pt_regs *regs, unsigned long error_code)
260 {
261 enum ctx_state prev_state;
262
263 switch (kvm_read_and_reset_pf_reason()) {
264 default:
265 trace_do_page_fault(regs, error_code);
266 break;
267 case KVM_PV_REASON_PAGE_NOT_PRESENT:
268 /* page is swapped out by the host. */
269 prev_state = exception_enter();
270 exit_idle();
271 kvm_async_pf_task_wait((u32)read_cr2());
272 exception_exit(prev_state);
273 break;
274 case KVM_PV_REASON_PAGE_READY:
275 rcu_irq_enter();
276 exit_idle();
277 kvm_async_pf_task_wake((u32)read_cr2());
278 rcu_irq_exit();
279 break;
280 }
281 }
282 NOKPROBE_SYMBOL(do_async_page_fault);
283
284 static void __init paravirt_ops_setup(void)
285 {
286 pv_info.name = "KVM";
287
288 if (kvm_para_has_feature(KVM_FEATURE_NOP_IO_DELAY))
289 pv_cpu_ops.io_delay = kvm_io_delay;
290
291 #ifdef CONFIG_X86_IO_APIC
292 no_timer_check = 1;
293 #endif
294 }
295
296 static void kvm_register_steal_time(void)
297 {
298 int cpu = smp_processor_id();
299 struct kvm_steal_time *st = &per_cpu(steal_time, cpu);
300
301 if (!has_steal_clock)
302 return;
303
304 wrmsrl(MSR_KVM_STEAL_TIME, (slow_virt_to_phys(st) | KVM_MSR_ENABLED));
305 pr_info("kvm-stealtime: cpu %d, msr %llx\n",
306 cpu, (unsigned long long) slow_virt_to_phys(st));
307 }
308
309 static DEFINE_PER_CPU(unsigned long, kvm_apic_eoi) = KVM_PV_EOI_DISABLED;
310
311 static void kvm_guest_apic_eoi_write(u32 reg, u32 val)
312 {
313 /**
314 * This relies on __test_and_clear_bit to modify the memory
315 * in a way that is atomic with respect to the local CPU.
316 * The hypervisor only accesses this memory from the local CPU so
317 * there's no need for lock or memory barriers.
318 * An optimization barrier is implied in apic write.
319 */
320 if (__test_and_clear_bit(KVM_PV_EOI_BIT, this_cpu_ptr(&kvm_apic_eoi)))
321 return;
322 apic_write(APIC_EOI, APIC_EOI_ACK);
323 }
324
325 static void kvm_guest_cpu_init(void)
326 {
327 if (!kvm_para_available())
328 return;
329
330 if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF) && kvmapf) {
331 u64 pa = slow_virt_to_phys(this_cpu_ptr(&apf_reason));
332
333 #ifdef CONFIG_PREEMPT
334 pa |= KVM_ASYNC_PF_SEND_ALWAYS;
335 #endif
336 wrmsrl(MSR_KVM_ASYNC_PF_EN, pa | KVM_ASYNC_PF_ENABLED);
337 __this_cpu_write(apf_reason.enabled, 1);
338 printk(KERN_INFO"KVM setup async PF for cpu %d\n",
339 smp_processor_id());
340 }
341
342 if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) {
343 unsigned long pa;
344 /* Size alignment is implied but just to make it explicit. */
345 BUILD_BUG_ON(__alignof__(kvm_apic_eoi) < 4);
346 __this_cpu_write(kvm_apic_eoi, 0);
347 pa = slow_virt_to_phys(this_cpu_ptr(&kvm_apic_eoi))
348 | KVM_MSR_ENABLED;
349 wrmsrl(MSR_KVM_PV_EOI_EN, pa);
350 }
351
352 if (has_steal_clock)
353 kvm_register_steal_time();
354 }
355
356 static void kvm_pv_disable_apf(void)
357 {
358 if (!__this_cpu_read(apf_reason.enabled))
359 return;
360
361 wrmsrl(MSR_KVM_ASYNC_PF_EN, 0);
362 __this_cpu_write(apf_reason.enabled, 0);
363
364 printk(KERN_INFO"Unregister pv shared memory for cpu %d\n",
365 smp_processor_id());
366 }
367
368 static void kvm_pv_guest_cpu_reboot(void *unused)
369 {
370 /*
371 * We disable PV EOI before we load a new kernel by kexec,
372 * since MSR_KVM_PV_EOI_EN stores a pointer into old kernel's memory.
373 * New kernel can re-enable when it boots.
374 */
375 if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
376 wrmsrl(MSR_KVM_PV_EOI_EN, 0);
377 kvm_pv_disable_apf();
378 kvm_disable_steal_time();
379 }
380
381 static int kvm_pv_reboot_notify(struct notifier_block *nb,
382 unsigned long code, void *unused)
383 {
384 if (code == SYS_RESTART)
385 on_each_cpu(kvm_pv_guest_cpu_reboot, NULL, 1);
386 return NOTIFY_DONE;
387 }
388
389 static struct notifier_block kvm_pv_reboot_nb = {
390 .notifier_call = kvm_pv_reboot_notify,
391 };
392
393 static u64 kvm_steal_clock(int cpu)
394 {
395 u64 steal;
396 struct kvm_steal_time *src;
397 int version;
398
399 src = &per_cpu(steal_time, cpu);
400 do {
401 version = src->version;
402 rmb();
403 steal = src->steal;
404 rmb();
405 } while ((version & 1) || (version != src->version));
406
407 return steal;
408 }
409
410 void kvm_disable_steal_time(void)
411 {
412 if (!has_steal_clock)
413 return;
414
415 wrmsr(MSR_KVM_STEAL_TIME, 0, 0);
416 }
417
418 #ifdef CONFIG_SMP
419 static void __init kvm_smp_prepare_boot_cpu(void)
420 {
421 kvm_guest_cpu_init();
422 native_smp_prepare_boot_cpu();
423 kvm_spinlock_init();
424 }
425
426 static void kvm_guest_cpu_online(void *dummy)
427 {
428 kvm_guest_cpu_init();
429 }
430
431 static void kvm_guest_cpu_offline(void *dummy)
432 {
433 kvm_disable_steal_time();
434 if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
435 wrmsrl(MSR_KVM_PV_EOI_EN, 0);
436 kvm_pv_disable_apf();
437 apf_task_wake_all();
438 }
439
440 static int kvm_cpu_notify(struct notifier_block *self, unsigned long action,
441 void *hcpu)
442 {
443 int cpu = (unsigned long)hcpu;
444 switch (action) {
445 case CPU_ONLINE:
446 case CPU_DOWN_FAILED:
447 case CPU_ONLINE_FROZEN:
448 smp_call_function_single(cpu, kvm_guest_cpu_online, NULL, 0);
449 break;
450 case CPU_DOWN_PREPARE:
451 case CPU_DOWN_PREPARE_FROZEN:
452 smp_call_function_single(cpu, kvm_guest_cpu_offline, NULL, 1);
453 break;
454 default:
455 break;
456 }
457 return NOTIFY_OK;
458 }
459
460 static struct notifier_block kvm_cpu_notifier = {
461 .notifier_call = kvm_cpu_notify,
462 };
463 #endif
464
465 static void __init kvm_apf_trap_init(void)
466 {
467 set_intr_gate(14, async_page_fault);
468 }
469
470 void __init kvm_guest_init(void)
471 {
472 int i;
473
474 if (!kvm_para_available())
475 return;
476
477 paravirt_ops_setup();
478 register_reboot_notifier(&kvm_pv_reboot_nb);
479 for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++)
480 raw_spin_lock_init(&async_pf_sleepers[i].lock);
481 if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF))
482 x86_init.irqs.trap_init = kvm_apf_trap_init;
483
484 if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
485 has_steal_clock = 1;
486 pv_time_ops.steal_clock = kvm_steal_clock;
487 }
488
489 if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
490 apic_set_eoi_write(kvm_guest_apic_eoi_write);
491
492 if (kvmclock_vsyscall)
493 kvm_setup_vsyscall_timeinfo();
494
495 #ifdef CONFIG_SMP
496 smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
497 register_cpu_notifier(&kvm_cpu_notifier);
498 #else
499 kvm_guest_cpu_init();
500 #endif
501
502 /*
503 * Hard lockup detection is enabled by default. Disable it, as guests
504 * can get false positives too easily, for example if the host is
505 * overcommitted.
506 */
507 hardlockup_detector_disable();
508 }
509
510 static noinline uint32_t __kvm_cpuid_base(void)
511 {
512 if (boot_cpu_data.cpuid_level < 0)
513 return 0; /* So we don't blow up on old processors */
514
515 if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
516 return hypervisor_cpuid_base("KVMKVMKVM\0\0\0", 0);
517
518 return 0;
519 }
520
521 static inline uint32_t kvm_cpuid_base(void)
522 {
523 static int kvm_cpuid_base = -1;
524
525 if (kvm_cpuid_base == -1)
526 kvm_cpuid_base = __kvm_cpuid_base();
527
528 return kvm_cpuid_base;
529 }
530
531 bool kvm_para_available(void)
532 {
533 return kvm_cpuid_base() != 0;
534 }
535 EXPORT_SYMBOL_GPL(kvm_para_available);
536
537 unsigned int kvm_arch_para_features(void)
538 {
539 return cpuid_eax(kvm_cpuid_base() | KVM_CPUID_FEATURES);
540 }
541
542 static uint32_t __init kvm_detect(void)
543 {
544 return kvm_cpuid_base();
545 }
546
547 const struct hypervisor_x86 x86_hyper_kvm __refconst = {
548 .name = "KVM",
549 .detect = kvm_detect,
550 .x2apic_available = kvm_para_available,
551 };
552 EXPORT_SYMBOL_GPL(x86_hyper_kvm);
553
554 static __init int activate_jump_labels(void)
555 {
556 if (has_steal_clock) {
557 static_key_slow_inc(&paravirt_steal_enabled);
558 if (steal_acc)
559 static_key_slow_inc(&paravirt_steal_rq_enabled);
560 }
561
562 return 0;
563 }
564 arch_initcall(activate_jump_labels);
565
566 #ifdef CONFIG_PARAVIRT_SPINLOCKS
567
568 /* Kick a cpu by its apicid. Used to wake up a halted vcpu */
569 static void kvm_kick_cpu(int cpu)
570 {
571 int apicid;
572 unsigned long flags = 0;
573
574 apicid = per_cpu(x86_cpu_to_apicid, cpu);
575 kvm_hypercall2(KVM_HC_KICK_CPU, flags, apicid);
576 }
577
578
579 #ifdef CONFIG_QUEUED_SPINLOCKS
580
581 #include <asm/qspinlock.h>
582
583 static void kvm_wait(u8 *ptr, u8 val)
584 {
585 unsigned long flags;
586
587 if (in_nmi())
588 return;
589
590 local_irq_save(flags);
591
592 if (READ_ONCE(*ptr) != val)
593 goto out;
594
595 /*
596 * halt until it's our turn and kicked. Note that we do safe halt
597 * for irq enabled case to avoid hang when lock info is overwritten
598 * in irq spinlock slowpath and no spurious interrupt occur to save us.
599 */
600 if (arch_irqs_disabled_flags(flags))
601 halt();
602 else
603 safe_halt();
604
605 out:
606 local_irq_restore(flags);
607 }
608
609 #else /* !CONFIG_QUEUED_SPINLOCKS */
610
611 enum kvm_contention_stat {
612 TAKEN_SLOW,
613 TAKEN_SLOW_PICKUP,
614 RELEASED_SLOW,
615 RELEASED_SLOW_KICKED,
616 NR_CONTENTION_STATS
617 };
618
619 #ifdef CONFIG_KVM_DEBUG_FS
620 #define HISTO_BUCKETS 30
621
622 static struct kvm_spinlock_stats
623 {
624 u32 contention_stats[NR_CONTENTION_STATS];
625 u32 histo_spin_blocked[HISTO_BUCKETS+1];
626 u64 time_blocked;
627 } spinlock_stats;
628
629 static u8 zero_stats;
630
631 static inline void check_zero(void)
632 {
633 u8 ret;
634 u8 old;
635
636 old = READ_ONCE(zero_stats);
637 if (unlikely(old)) {
638 ret = cmpxchg(&zero_stats, old, 0);
639 /* This ensures only one fellow resets the stat */
640 if (ret == old)
641 memset(&spinlock_stats, 0, sizeof(spinlock_stats));
642 }
643 }
644
645 static inline void add_stats(enum kvm_contention_stat var, u32 val)
646 {
647 check_zero();
648 spinlock_stats.contention_stats[var] += val;
649 }
650
651
652 static inline u64 spin_time_start(void)
653 {
654 return sched_clock();
655 }
656
657 static void __spin_time_accum(u64 delta, u32 *array)
658 {
659 unsigned index;
660
661 index = ilog2(delta);
662 check_zero();
663
664 if (index < HISTO_BUCKETS)
665 array[index]++;
666 else
667 array[HISTO_BUCKETS]++;
668 }
669
670 static inline void spin_time_accum_blocked(u64 start)
671 {
672 u32 delta;
673
674 delta = sched_clock() - start;
675 __spin_time_accum(delta, spinlock_stats.histo_spin_blocked);
676 spinlock_stats.time_blocked += delta;
677 }
678
679 static struct dentry *d_spin_debug;
680 static struct dentry *d_kvm_debug;
681
682 static struct dentry *kvm_init_debugfs(void)
683 {
684 d_kvm_debug = debugfs_create_dir("kvm-guest", NULL);
685 if (!d_kvm_debug)
686 printk(KERN_WARNING "Could not create 'kvm' debugfs directory\n");
687
688 return d_kvm_debug;
689 }
690
691 static int __init kvm_spinlock_debugfs(void)
692 {
693 struct dentry *d_kvm;
694
695 d_kvm = kvm_init_debugfs();
696 if (d_kvm == NULL)
697 return -ENOMEM;
698
699 d_spin_debug = debugfs_create_dir("spinlocks", d_kvm);
700
701 debugfs_create_u8("zero_stats", 0644, d_spin_debug, &zero_stats);
702
703 debugfs_create_u32("taken_slow", 0444, d_spin_debug,
704 &spinlock_stats.contention_stats[TAKEN_SLOW]);
705 debugfs_create_u32("taken_slow_pickup", 0444, d_spin_debug,
706 &spinlock_stats.contention_stats[TAKEN_SLOW_PICKUP]);
707
708 debugfs_create_u32("released_slow", 0444, d_spin_debug,
709 &spinlock_stats.contention_stats[RELEASED_SLOW]);
710 debugfs_create_u32("released_slow_kicked", 0444, d_spin_debug,
711 &spinlock_stats.contention_stats[RELEASED_SLOW_KICKED]);
712
713 debugfs_create_u64("time_blocked", 0444, d_spin_debug,
714 &spinlock_stats.time_blocked);
715
716 debugfs_create_u32_array("histo_blocked", 0444, d_spin_debug,
717 spinlock_stats.histo_spin_blocked, HISTO_BUCKETS + 1);
718
719 return 0;
720 }
721 fs_initcall(kvm_spinlock_debugfs);
722 #else /* !CONFIG_KVM_DEBUG_FS */
723 static inline void add_stats(enum kvm_contention_stat var, u32 val)
724 {
725 }
726
727 static inline u64 spin_time_start(void)
728 {
729 return 0;
730 }
731
732 static inline void spin_time_accum_blocked(u64 start)
733 {
734 }
735 #endif /* CONFIG_KVM_DEBUG_FS */
736
737 struct kvm_lock_waiting {
738 struct arch_spinlock *lock;
739 __ticket_t want;
740 };
741
742 /* cpus 'waiting' on a spinlock to become available */
743 static cpumask_t waiting_cpus;
744
745 /* Track spinlock on which a cpu is waiting */
746 static DEFINE_PER_CPU(struct kvm_lock_waiting, klock_waiting);
747
748 __visible void kvm_lock_spinning(struct arch_spinlock *lock, __ticket_t want)
749 {
750 struct kvm_lock_waiting *w;
751 int cpu;
752 u64 start;
753 unsigned long flags;
754 __ticket_t head;
755
756 if (in_nmi())
757 return;
758
759 w = this_cpu_ptr(&klock_waiting);
760 cpu = smp_processor_id();
761 start = spin_time_start();
762
763 /*
764 * Make sure an interrupt handler can't upset things in a
765 * partially setup state.
766 */
767 local_irq_save(flags);
768
769 /*
770 * The ordering protocol on this is that the "lock" pointer
771 * may only be set non-NULL if the "want" ticket is correct.
772 * If we're updating "want", we must first clear "lock".
773 */
774 w->lock = NULL;
775 smp_wmb();
776 w->want = want;
777 smp_wmb();
778 w->lock = lock;
779
780 add_stats(TAKEN_SLOW, 1);
781
782 /*
783 * This uses set_bit, which is atomic but we should not rely on its
784 * reordering gurantees. So barrier is needed after this call.
785 */
786 cpumask_set_cpu(cpu, &waiting_cpus);
787
788 barrier();
789
790 /*
791 * Mark entry to slowpath before doing the pickup test to make
792 * sure we don't deadlock with an unlocker.
793 */
794 __ticket_enter_slowpath(lock);
795
796 /* make sure enter_slowpath, which is atomic does not cross the read */
797 smp_mb__after_atomic();
798
799 /*
800 * check again make sure it didn't become free while
801 * we weren't looking.
802 */
803 head = READ_ONCE(lock->tickets.head);
804 if (__tickets_equal(head, want)) {
805 add_stats(TAKEN_SLOW_PICKUP, 1);
806 goto out;
807 }
808
809 /*
810 * halt until it's our turn and kicked. Note that we do safe halt
811 * for irq enabled case to avoid hang when lock info is overwritten
812 * in irq spinlock slowpath and no spurious interrupt occur to save us.
813 */
814 if (arch_irqs_disabled_flags(flags))
815 halt();
816 else
817 safe_halt();
818
819 out:
820 cpumask_clear_cpu(cpu, &waiting_cpus);
821 w->lock = NULL;
822 local_irq_restore(flags);
823 spin_time_accum_blocked(start);
824 }
825 PV_CALLEE_SAVE_REGS_THUNK(kvm_lock_spinning);
826
827 /* Kick vcpu waiting on @lock->head to reach value @ticket */
828 static void kvm_unlock_kick(struct arch_spinlock *lock, __ticket_t ticket)
829 {
830 int cpu;
831
832 add_stats(RELEASED_SLOW, 1);
833 for_each_cpu(cpu, &waiting_cpus) {
834 const struct kvm_lock_waiting *w = &per_cpu(klock_waiting, cpu);
835 if (READ_ONCE(w->lock) == lock &&
836 READ_ONCE(w->want) == ticket) {
837 add_stats(RELEASED_SLOW_KICKED, 1);
838 kvm_kick_cpu(cpu);
839 break;
840 }
841 }
842 }
843
844 #endif /* !CONFIG_QUEUED_SPINLOCKS */
845
846 /*
847 * Setup pv_lock_ops to exploit KVM_FEATURE_PV_UNHALT if present.
848 */
849 void __init kvm_spinlock_init(void)
850 {
851 if (!kvm_para_available())
852 return;
853 /* Does host kernel support KVM_FEATURE_PV_UNHALT? */
854 if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
855 return;
856
857 #ifdef CONFIG_QUEUED_SPINLOCKS
858 __pv_init_lock_hash();
859 pv_lock_ops.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
860 pv_lock_ops.queued_spin_unlock = PV_CALLEE_SAVE(__pv_queued_spin_unlock);
861 pv_lock_ops.wait = kvm_wait;
862 pv_lock_ops.kick = kvm_kick_cpu;
863 #else /* !CONFIG_QUEUED_SPINLOCKS */
864 pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(kvm_lock_spinning);
865 pv_lock_ops.unlock_kick = kvm_unlock_kick;
866 #endif
867 }
868
869 static __init int kvm_spinlock_init_jump(void)
870 {
871 if (!kvm_para_available())
872 return 0;
873 if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
874 return 0;
875
876 static_key_slow_inc(&paravirt_ticketlocks_enabled);
877 printk(KERN_INFO "KVM setup paravirtual spinlock\n");
878
879 return 0;
880 }
881 early_initcall(kvm_spinlock_init_jump);
882
883 #endif /* CONFIG_PARAVIRT_SPINLOCKS */
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