x86/virt: Add enum for hypervisors to replace x86_hyper
[muen/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/init.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/apic.h>
46 #include <asm/apicdef.h>
47 #include <asm/hypervisor.h>
48 #include <asm/kvm_guest.h>
49
50 static int kvmapf = 1;
51
52 static int parse_no_kvmapf(char *arg)
53 {
54         kvmapf = 0;
55         return 0;
56 }
57
58 early_param("no-kvmapf", parse_no_kvmapf);
59
60 static int steal_acc = 1;
61 static int parse_no_stealacc(char *arg)
62 {
63         steal_acc = 0;
64         return 0;
65 }
66
67 early_param("no-steal-acc", parse_no_stealacc);
68
69 static int kvmclock_vsyscall = 1;
70 static int parse_no_kvmclock_vsyscall(char *arg)
71 {
72         kvmclock_vsyscall = 0;
73         return 0;
74 }
75
76 early_param("no-kvmclock-vsyscall", parse_no_kvmclock_vsyscall);
77
78 static DEFINE_PER_CPU(struct kvm_vcpu_pv_apf_data, apf_reason) __aligned(64);
79 static DEFINE_PER_CPU(struct kvm_steal_time, steal_time) __aligned(64);
80 static int has_steal_clock = 0;
81
82 /*
83  * No need for any "IO delay" on KVM
84  */
85 static void kvm_io_delay(void)
86 {
87 }
88
89 #define KVM_TASK_SLEEP_HASHBITS 8
90 #define KVM_TASK_SLEEP_HASHSIZE (1<<KVM_TASK_SLEEP_HASHBITS)
91
92 struct kvm_task_sleep_node {
93         struct hlist_node link;
94         struct swait_queue_head wq;
95         u32 token;
96         int cpu;
97         bool halted;
98 };
99
100 static struct kvm_task_sleep_head {
101         raw_spinlock_t lock;
102         struct hlist_head list;
103 } async_pf_sleepers[KVM_TASK_SLEEP_HASHSIZE];
104
105 static struct kvm_task_sleep_node *_find_apf_task(struct kvm_task_sleep_head *b,
106                                                   u32 token)
107 {
108         struct hlist_node *p;
109
110         hlist_for_each(p, &b->list) {
111                 struct kvm_task_sleep_node *n =
112                         hlist_entry(p, typeof(*n), link);
113                 if (n->token == token)
114                         return n;
115         }
116
117         return NULL;
118 }
119
120 /*
121  * @interrupt_kernel: Is this called from a routine which interrupts the kernel
122  *                    (other than user space)?
123  */
124 void kvm_async_pf_task_wait(u32 token, int interrupt_kernel)
125 {
126         u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS);
127         struct kvm_task_sleep_head *b = &async_pf_sleepers[key];
128         struct kvm_task_sleep_node n, *e;
129         DECLARE_SWAITQUEUE(wait);
130
131         rcu_irq_enter();
132
133         raw_spin_lock(&b->lock);
134         e = _find_apf_task(b, token);
135         if (e) {
136                 /* dummy entry exist -> wake up was delivered ahead of PF */
137                 hlist_del(&e->link);
138                 kfree(e);
139                 raw_spin_unlock(&b->lock);
140
141                 rcu_irq_exit();
142                 return;
143         }
144
145         n.token = token;
146         n.cpu = smp_processor_id();
147         n.halted = is_idle_task(current) ||
148                    (IS_ENABLED(CONFIG_PREEMPT_COUNT)
149                     ? preempt_count() > 1 || rcu_preempt_depth()
150                     : interrupt_kernel);
151         init_swait_queue_head(&n.wq);
152         hlist_add_head(&n.link, &b->list);
153         raw_spin_unlock(&b->lock);
154
155         for (;;) {
156                 if (!n.halted)
157                         prepare_to_swait(&n.wq, &wait, TASK_UNINTERRUPTIBLE);
158                 if (hlist_unhashed(&n.link))
159                         break;
160
161                 rcu_irq_exit();
162
163                 if (!n.halted) {
164                         local_irq_enable();
165                         schedule();
166                         local_irq_disable();
167                 } else {
168                         /*
169                          * We cannot reschedule. So halt.
170                          */
171                         native_safe_halt();
172                         local_irq_disable();
173                 }
174
175                 rcu_irq_enter();
176         }
177         if (!n.halted)
178                 finish_swait(&n.wq, &wait);
179
180         rcu_irq_exit();
181         return;
182 }
183 EXPORT_SYMBOL_GPL(kvm_async_pf_task_wait);
184
185 static void apf_task_wake_one(struct kvm_task_sleep_node *n)
186 {
187         hlist_del_init(&n->link);
188         if (n->halted)
189                 smp_send_reschedule(n->cpu);
190         else if (swq_has_sleeper(&n->wq))
191                 swake_up(&n->wq);
192 }
193
194 static void apf_task_wake_all(void)
195 {
196         int i;
197
198         for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++) {
199                 struct hlist_node *p, *next;
200                 struct kvm_task_sleep_head *b = &async_pf_sleepers[i];
201                 raw_spin_lock(&b->lock);
202                 hlist_for_each_safe(p, next, &b->list) {
203                         struct kvm_task_sleep_node *n =
204                                 hlist_entry(p, typeof(*n), link);
205                         if (n->cpu == smp_processor_id())
206                                 apf_task_wake_one(n);
207                 }
208                 raw_spin_unlock(&b->lock);
209         }
210 }
211
212 void kvm_async_pf_task_wake(u32 token)
213 {
214         u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS);
215         struct kvm_task_sleep_head *b = &async_pf_sleepers[key];
216         struct kvm_task_sleep_node *n;
217
218         if (token == ~0) {
219                 apf_task_wake_all();
220                 return;
221         }
222
223 again:
224         raw_spin_lock(&b->lock);
225         n = _find_apf_task(b, token);
226         if (!n) {
227                 /*
228                  * async PF was not yet handled.
229                  * Add dummy entry for the token.
230                  */
231                 n = kzalloc(sizeof(*n), GFP_ATOMIC);
232                 if (!n) {
233                         /*
234                          * Allocation failed! Busy wait while other cpu
235                          * handles async PF.
236                          */
237                         raw_spin_unlock(&b->lock);
238                         cpu_relax();
239                         goto again;
240                 }
241                 n->token = token;
242                 n->cpu = smp_processor_id();
243                 init_swait_queue_head(&n->wq);
244                 hlist_add_head(&n->link, &b->list);
245         } else
246                 apf_task_wake_one(n);
247         raw_spin_unlock(&b->lock);
248         return;
249 }
250 EXPORT_SYMBOL_GPL(kvm_async_pf_task_wake);
251
252 u32 kvm_read_and_reset_pf_reason(void)
253 {
254         u32 reason = 0;
255
256         if (__this_cpu_read(apf_reason.enabled)) {
257                 reason = __this_cpu_read(apf_reason.reason);
258                 __this_cpu_write(apf_reason.reason, 0);
259         }
260
261         return reason;
262 }
263 EXPORT_SYMBOL_GPL(kvm_read_and_reset_pf_reason);
264 NOKPROBE_SYMBOL(kvm_read_and_reset_pf_reason);
265
266 dotraplinkage void
267 do_async_page_fault(struct pt_regs *regs, unsigned long error_code)
268 {
269         enum ctx_state prev_state;
270
271         switch (kvm_read_and_reset_pf_reason()) {
272         default:
273                 do_page_fault(regs, error_code);
274                 break;
275         case KVM_PV_REASON_PAGE_NOT_PRESENT:
276                 /* page is swapped out by the host. */
277                 prev_state = exception_enter();
278                 kvm_async_pf_task_wait((u32)read_cr2(), !user_mode(regs));
279                 exception_exit(prev_state);
280                 break;
281         case KVM_PV_REASON_PAGE_READY:
282                 rcu_irq_enter();
283                 kvm_async_pf_task_wake((u32)read_cr2());
284                 rcu_irq_exit();
285                 break;
286         }
287 }
288 NOKPROBE_SYMBOL(do_async_page_fault);
289
290 static void __init paravirt_ops_setup(void)
291 {
292         pv_info.name = "KVM";
293
294         if (kvm_para_has_feature(KVM_FEATURE_NOP_IO_DELAY))
295                 pv_cpu_ops.io_delay = kvm_io_delay;
296
297 #ifdef CONFIG_X86_IO_APIC
298         no_timer_check = 1;
299 #endif
300 }
301
302 static void kvm_register_steal_time(void)
303 {
304         int cpu = smp_processor_id();
305         struct kvm_steal_time *st = &per_cpu(steal_time, cpu);
306
307         if (!has_steal_clock)
308                 return;
309
310         wrmsrl(MSR_KVM_STEAL_TIME, (slow_virt_to_phys(st) | KVM_MSR_ENABLED));
311         pr_info("kvm-stealtime: cpu %d, msr %llx\n",
312                 cpu, (unsigned long long) slow_virt_to_phys(st));
313 }
314
315 static DEFINE_PER_CPU(unsigned long, kvm_apic_eoi) = KVM_PV_EOI_DISABLED;
316
317 static notrace void kvm_guest_apic_eoi_write(u32 reg, u32 val)
318 {
319         /**
320          * This relies on __test_and_clear_bit to modify the memory
321          * in a way that is atomic with respect to the local CPU.
322          * The hypervisor only accesses this memory from the local CPU so
323          * there's no need for lock or memory barriers.
324          * An optimization barrier is implied in apic write.
325          */
326         if (__test_and_clear_bit(KVM_PV_EOI_BIT, this_cpu_ptr(&kvm_apic_eoi)))
327                 return;
328         apic->native_eoi_write(APIC_EOI, APIC_EOI_ACK);
329 }
330
331 static void kvm_guest_cpu_init(void)
332 {
333         if (!kvm_para_available())
334                 return;
335
336         if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF) && kvmapf) {
337                 u64 pa = slow_virt_to_phys(this_cpu_ptr(&apf_reason));
338
339 #ifdef CONFIG_PREEMPT
340                 pa |= KVM_ASYNC_PF_SEND_ALWAYS;
341 #endif
342                 pa |= KVM_ASYNC_PF_ENABLED;
343
344                 /* Async page fault support for L1 hypervisor is optional */
345                 if (wrmsr_safe(MSR_KVM_ASYNC_PF_EN,
346                         (pa | KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT) & 0xffffffff, pa >> 32) < 0)
347                         wrmsrl(MSR_KVM_ASYNC_PF_EN, pa);
348                 __this_cpu_write(apf_reason.enabled, 1);
349                 printk(KERN_INFO"KVM setup async PF for cpu %d\n",
350                        smp_processor_id());
351         }
352
353         if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) {
354                 unsigned long pa;
355                 /* Size alignment is implied but just to make it explicit. */
356                 BUILD_BUG_ON(__alignof__(kvm_apic_eoi) < 4);
357                 __this_cpu_write(kvm_apic_eoi, 0);
358                 pa = slow_virt_to_phys(this_cpu_ptr(&kvm_apic_eoi))
359                         | KVM_MSR_ENABLED;
360                 wrmsrl(MSR_KVM_PV_EOI_EN, pa);
361         }
362
363         if (has_steal_clock)
364                 kvm_register_steal_time();
365 }
366
367 static void kvm_pv_disable_apf(void)
368 {
369         if (!__this_cpu_read(apf_reason.enabled))
370                 return;
371
372         wrmsrl(MSR_KVM_ASYNC_PF_EN, 0);
373         __this_cpu_write(apf_reason.enabled, 0);
374
375         printk(KERN_INFO"Unregister pv shared memory for cpu %d\n",
376                smp_processor_id());
377 }
378
379 static void kvm_pv_guest_cpu_reboot(void *unused)
380 {
381         /*
382          * We disable PV EOI before we load a new kernel by kexec,
383          * since MSR_KVM_PV_EOI_EN stores a pointer into old kernel's memory.
384          * New kernel can re-enable when it boots.
385          */
386         if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
387                 wrmsrl(MSR_KVM_PV_EOI_EN, 0);
388         kvm_pv_disable_apf();
389         kvm_disable_steal_time();
390 }
391
392 static int kvm_pv_reboot_notify(struct notifier_block *nb,
393                                 unsigned long code, void *unused)
394 {
395         if (code == SYS_RESTART)
396                 on_each_cpu(kvm_pv_guest_cpu_reboot, NULL, 1);
397         return NOTIFY_DONE;
398 }
399
400 static struct notifier_block kvm_pv_reboot_nb = {
401         .notifier_call = kvm_pv_reboot_notify,
402 };
403
404 static u64 kvm_steal_clock(int cpu)
405 {
406         u64 steal;
407         struct kvm_steal_time *src;
408         int version;
409
410         src = &per_cpu(steal_time, cpu);
411         do {
412                 version = src->version;
413                 virt_rmb();
414                 steal = src->steal;
415                 virt_rmb();
416         } while ((version & 1) || (version != src->version));
417
418         return steal;
419 }
420
421 void kvm_disable_steal_time(void)
422 {
423         if (!has_steal_clock)
424                 return;
425
426         wrmsr(MSR_KVM_STEAL_TIME, 0, 0);
427 }
428
429 #ifdef CONFIG_SMP
430 static void __init kvm_smp_prepare_boot_cpu(void)
431 {
432         kvm_guest_cpu_init();
433         native_smp_prepare_boot_cpu();
434         kvm_spinlock_init();
435 }
436
437 static void kvm_guest_cpu_offline(void)
438 {
439         kvm_disable_steal_time();
440         if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
441                 wrmsrl(MSR_KVM_PV_EOI_EN, 0);
442         kvm_pv_disable_apf();
443         apf_task_wake_all();
444 }
445
446 static int kvm_cpu_online(unsigned int cpu)
447 {
448         local_irq_disable();
449         kvm_guest_cpu_init();
450         local_irq_enable();
451         return 0;
452 }
453
454 static int kvm_cpu_down_prepare(unsigned int cpu)
455 {
456         local_irq_disable();
457         kvm_guest_cpu_offline();
458         local_irq_enable();
459         return 0;
460 }
461 #endif
462
463 static void __init kvm_apf_trap_init(void)
464 {
465         update_intr_gate(X86_TRAP_PF, async_page_fault);
466 }
467
468 void __init kvm_guest_init(void)
469 {
470         int i;
471
472         if (!kvm_para_available())
473                 return;
474
475         paravirt_ops_setup();
476         register_reboot_notifier(&kvm_pv_reboot_nb);
477         for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++)
478                 raw_spin_lock_init(&async_pf_sleepers[i].lock);
479         if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF))
480                 x86_init.irqs.trap_init = kvm_apf_trap_init;
481
482         if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
483                 has_steal_clock = 1;
484                 pv_time_ops.steal_clock = kvm_steal_clock;
485         }
486
487         if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
488                 apic_set_eoi_write(kvm_guest_apic_eoi_write);
489
490         if (kvmclock_vsyscall)
491                 kvm_setup_vsyscall_timeinfo();
492
493 #ifdef CONFIG_SMP
494         smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
495         if (cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "x86/kvm:online",
496                                       kvm_cpu_online, kvm_cpu_down_prepare) < 0)
497                 pr_err("kvm_guest: Failed to install cpu hotplug callbacks\n");
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 __initconst struct hypervisor_x86 x86_hyper_kvm = {
548         .name                   = "KVM",
549         .detect                 = kvm_detect,
550         .type                   = X86_HYPER_KVM,
551         .init.x2apic_available  = kvm_para_available,
552 };
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 #include <asm/qspinlock.h>
579
580 static void kvm_wait(u8 *ptr, u8 val)
581 {
582         unsigned long flags;
583
584         if (in_nmi())
585                 return;
586
587         local_irq_save(flags);
588
589         if (READ_ONCE(*ptr) != val)
590                 goto out;
591
592         /*
593          * halt until it's our turn and kicked. Note that we do safe halt
594          * for irq enabled case to avoid hang when lock info is overwritten
595          * in irq spinlock slowpath and no spurious interrupt occur to save us.
596          */
597         if (arch_irqs_disabled_flags(flags))
598                 halt();
599         else
600                 safe_halt();
601
602 out:
603         local_irq_restore(flags);
604 }
605
606 #ifdef CONFIG_X86_32
607 __visible bool __kvm_vcpu_is_preempted(long cpu)
608 {
609         struct kvm_steal_time *src = &per_cpu(steal_time, cpu);
610
611         return !!src->preempted;
612 }
613 PV_CALLEE_SAVE_REGS_THUNK(__kvm_vcpu_is_preempted);
614
615 #else
616
617 #include <asm/asm-offsets.h>
618
619 extern bool __raw_callee_save___kvm_vcpu_is_preempted(long);
620
621 /*
622  * Hand-optimize version for x86-64 to avoid 8 64-bit register saving and
623  * restoring to/from the stack.
624  */
625 asm(
626 ".pushsection .text;"
627 ".global __raw_callee_save___kvm_vcpu_is_preempted;"
628 ".type __raw_callee_save___kvm_vcpu_is_preempted, @function;"
629 "__raw_callee_save___kvm_vcpu_is_preempted:"
630 "movq   __per_cpu_offset(,%rdi,8), %rax;"
631 "cmpb   $0, " __stringify(KVM_STEAL_TIME_preempted) "+steal_time(%rax);"
632 "setne  %al;"
633 "ret;"
634 ".popsection");
635
636 #endif
637
638 /*
639  * Setup pv_lock_ops to exploit KVM_FEATURE_PV_UNHALT if present.
640  */
641 void __init kvm_spinlock_init(void)
642 {
643         if (!kvm_para_available())
644                 return;
645         /* Does host kernel support KVM_FEATURE_PV_UNHALT? */
646         if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
647                 return;
648
649         __pv_init_lock_hash();
650         pv_lock_ops.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
651         pv_lock_ops.queued_spin_unlock = PV_CALLEE_SAVE(__pv_queued_spin_unlock);
652         pv_lock_ops.wait = kvm_wait;
653         pv_lock_ops.kick = kvm_kick_cpu;
654
655         if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
656                 pv_lock_ops.vcpu_is_preempted =
657                         PV_CALLEE_SAVE(__kvm_vcpu_is_preempted);
658         }
659 }
660
661 #endif  /* CONFIG_PARAVIRT_SPINLOCKS */