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 <asm/timer.h>
  40 #include <asm/cpu.h>
  41 #include <asm/traps.h>
  42 #include <asm/desc.h>
  43 #include <asm/tlbflush.h>
  44 #include <asm/idle.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         wait_queue_head_t wq;
  95         u32 token;
  96         int cpu;
  97         bool halted;
  98 };
  99
 100 static struct kvm_task_sleep_head {
 101         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 void kvm_async_pf_task_wait(u32 token)
 121 {
 122         u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS);
 123         struct kvm_task_sleep_head *b = &async_pf_sleepers[key];
 124         struct kvm_task_sleep_node n, *e;
 125         DEFINE_WAIT(wait);
 126
 127         rcu_irq_enter();
 128
 129         spin_lock(&b->lock);
 130         e = _find_apf_task(b, token);
 131         if (e) {
 132                 /* dummy entry exist -> wake up was delivered ahead of PF */
 133                 hlist_del(&e->link);
 134                 kfree(e);
 135                 spin_unlock(&b->lock);
 136
 137                 rcu_irq_exit();
 138                 return;
 139         }
 140
 141         n.token = token;
 142         n.cpu = smp_processor_id();
 143         n.halted = is_idle_task(current) || preempt_count() > 1;
 144         init_waitqueue_head(&n.wq);
 145         hlist_add_head(&n.link, &b->list);
 146         spin_unlock(&b->lock);
 147
 148         for (;;) {
 149                 if (!n.halted)
 150                         prepare_to_wait(&n.wq, &wait, TASK_UNINTERRUPTIBLE);
 151                 if (hlist_unhashed(&n.link))
 152                         break;
 153
 154                 rcu_irq_exit();
 155
 156                 if (!n.halted) {
 157                         local_irq_enable();
 158                         schedule();
 159                         local_irq_disable();
 160                 } else {
 161                         /*
 162                          * We cannot reschedule. So halt.
 163                          */
 164                         native_safe_halt();
 165                         local_irq_disable();
 166                 }
 167
 168                 rcu_irq_enter();
 169         }
 170         if (!n.halted)
 171                 finish_wait(&n.wq, &wait);
 172
 173         rcu_irq_exit();
 174         return;
 175 }
 176 EXPORT_SYMBOL_GPL(kvm_async_pf_task_wait);
 177
 178 static void apf_task_wake_one(struct kvm_task_sleep_node *n)
 179 {
 180         hlist_del_init(&n->link);
 181         if (n->halted)
 182                 smp_send_reschedule(n->cpu);
 183         else if (waitqueue_active(&n->wq))
 184                 wake_up(&n->wq);
 185 }
 186
 187 static void apf_task_wake_all(void)
 188 {
 189         int i;
 190
 191         for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++) {
 192                 struct hlist_node *p, *next;
 193                 struct kvm_task_sleep_head *b = &async_pf_sleepers[i];
 194                 spin_lock(&b->lock);
 195                 hlist_for_each_safe(p, next, &b->list) {
 196                         struct kvm_task_sleep_node *n =
 197                                 hlist_entry(p, typeof(*n), link);
 198                         if (n->cpu == smp_processor_id())
 199                                 apf_task_wake_one(n);
 200                 }
 201                 spin_unlock(&b->lock);
 202         }
 203 }
 204
 205 void kvm_async_pf_task_wake(u32 token)
 206 {
 207         u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS);
 208         struct kvm_task_sleep_head *b = &async_pf_sleepers[key];
 209         struct kvm_task_sleep_node *n;
 210
 211         if (token == ~0) {
 212                 apf_task_wake_all();
 213                 return;
 214         }
 215
 216 again:
 217         spin_lock(&b->lock);
 218         n = _find_apf_task(b, token);
 219         if (!n) {
 220                 /*
 221                  * async PF was not yet handled.
 222                  * Add dummy entry for the token.
 223                  */
 224                 n = kzalloc(sizeof(*n), GFP_ATOMIC);
 225                 if (!n) {
 226                         /*
 227                          * Allocation failed! Busy wait while other cpu
 228                          * handles async PF.
 229                          */
 230                         spin_unlock(&b->lock);
 231                         cpu_relax();
 232                         goto again;
 233                 }
 234                 n->token = token;
 235                 n->cpu = smp_processor_id();
 236                 init_waitqueue_head(&n->wq);
 237                 hlist_add_head(&n->link, &b->list);
 238         } else
 239                 apf_task_wake_one(n);
 240         spin_unlock(&b->lock);
 241         return;
 242 }
 243 EXPORT_SYMBOL_GPL(kvm_async_pf_task_wake);
 244
 245 u32 kvm_read_and_reset_pf_reason(void)
 246 {
 247         u32 reason = 0;
 248
 249         if (__this_cpu_read(apf_reason.enabled)) {
 250                 reason = __this_cpu_read(apf_reason.reason);
 251                 __this_cpu_write(apf_reason.reason, 0);
 252         }
 253
 254         return reason;
 255 }
 256 EXPORT_SYMBOL_GPL(kvm_read_and_reset_pf_reason);
 257 NOKPROBE_SYMBOL(kvm_read_and_reset_pf_reason);
 258
 259 dotraplinkage void
 260 do_async_page_fault(struct pt_regs *regs, unsigned long error_code)
 261 {
 262         enum ctx_state prev_state;
 263
 264         switch (kvm_read_and_reset_pf_reason()) {
 265         default:
 266                 trace_do_page_fault(regs, error_code);
 267                 break;
 268         case KVM_PV_REASON_PAGE_NOT_PRESENT:
 269                 /* page is swapped out by the host. */
 270                 prev_state = exception_enter();
 271                 exit_idle();
 272                 kvm_async_pf_task_wait((u32)read_cr2());
 273                 exception_exit(prev_state);
 274                 break;
 275         case KVM_PV_REASON_PAGE_READY:
 276                 rcu_irq_enter();
 277                 exit_idle();
 278                 kvm_async_pf_task_wake((u32)read_cr2());
 279                 rcu_irq_exit();
 280                 break;
 281         }
 282 }
 283 NOKPROBE_SYMBOL(do_async_page_fault);
 284
 285 static void __init paravirt_ops_setup(void)
 286 {
 287         pv_info.name = "KVM";
 288
 289         /*
 290          * KVM isn't paravirt in the sense of paravirt_enabled.  A KVM
 291          * guest kernel works like a bare metal kernel with additional
 292          * features, and paravirt_enabled is about features that are
 293          * missing.
 294          */
 295         pv_info.paravirt_enabled = 0;
 296
 297         if (kvm_para_has_feature(KVM_FEATURE_NOP_IO_DELAY))
 298                 pv_cpu_ops.io_delay = kvm_io_delay;
 299
 300 #ifdef CONFIG_X86_IO_APIC
 301         no_timer_check = 1;
 302 #endif
 303 }
 304
 305 static void kvm_register_steal_time(void)
 306 {
 307         int cpu = smp_processor_id();
 308         struct kvm_steal_time *st = &per_cpu(steal_time, cpu);
 309
 310         if (!has_steal_clock)
 311                 return;
 312
 313         memset(st, 0, sizeof(*st));
 314
 315         wrmsrl(MSR_KVM_STEAL_TIME, (slow_virt_to_phys(st) | KVM_MSR_ENABLED));
 316         pr_info("kvm-stealtime: cpu %d, msr %llx\n",
 317                 cpu, (unsigned long long) slow_virt_to_phys(st));
 318 }
 319
 320 static DEFINE_PER_CPU(unsigned long, kvm_apic_eoi) = KVM_PV_EOI_DISABLED;
 321
 322 static void kvm_guest_apic_eoi_write(u32 reg, u32 val)
 323 {
 324         /**
 325          * This relies on __test_and_clear_bit to modify the memory
 326          * in a way that is atomic with respect to the local CPU.
 327          * The hypervisor only accesses this memory from the local CPU so
 328          * there's no need for lock or memory barriers.
 329          * An optimization barrier is implied in apic write.
 330          */
 331         if (__test_and_clear_bit(KVM_PV_EOI_BIT, this_cpu_ptr(&kvm_apic_eoi)))
 332                 return;
 333         apic_write(APIC_EOI, APIC_EOI_ACK);
 334 }
 335
 336 static void kvm_guest_cpu_init(void)
 337 {
 338         if (!kvm_para_available())
 339                 return;
 340
 341         if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF) && kvmapf) {
 342                 u64 pa = slow_virt_to_phys(this_cpu_ptr(&apf_reason));
 343
 344 #ifdef CONFIG_PREEMPT
 345                 pa |= KVM_ASYNC_PF_SEND_ALWAYS;
 346 #endif
 347                 wrmsrl(MSR_KVM_ASYNC_PF_EN, pa | KVM_ASYNC_PF_ENABLED);
 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                 rmb();
 414                 steal = src->steal;
 415                 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_online(void *dummy)
 438 {
 439         kvm_guest_cpu_init();
 440 }
 441
 442 static void kvm_guest_cpu_offline(void *dummy)
 443 {
 444         kvm_disable_steal_time();
 445         if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
 446                 wrmsrl(MSR_KVM_PV_EOI_EN, 0);
 447         kvm_pv_disable_apf();
 448         apf_task_wake_all();
 449 }
 450
 451 static int kvm_cpu_notify(struct notifier_block *self, unsigned long action,
 452                           void *hcpu)
 453 {
 454         int cpu = (unsigned long)hcpu;
 455         switch (action) {
 456         case CPU_ONLINE:
 457         case CPU_DOWN_FAILED:
 458         case CPU_ONLINE_FROZEN:
 459                 smp_call_function_single(cpu, kvm_guest_cpu_online, NULL, 0);
 460                 break;
 461         case CPU_DOWN_PREPARE:
 462         case CPU_DOWN_PREPARE_FROZEN:
 463                 smp_call_function_single(cpu, kvm_guest_cpu_offline, NULL, 1);
 464                 break;
 465         default:
 466                 break;
 467         }
 468         return NOTIFY_OK;
 469 }
 470
 471 static struct notifier_block kvm_cpu_notifier = {
 472         .notifier_call  = kvm_cpu_notify,
 473 };
 474 #endif
 475
 476 static void __init kvm_apf_trap_init(void)
 477 {
 478         set_intr_gate(14, async_page_fault);
 479 }
 480
 481 void __init kvm_guest_init(void)
 482 {
 483         int i;
 484
 485         if (!kvm_para_available())
 486                 return;
 487
 488         paravirt_ops_setup();
 489         register_reboot_notifier(&kvm_pv_reboot_nb);
 490         for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++)
 491                 spin_lock_init(&async_pf_sleepers[i].lock);
 492         if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF))
 493                 x86_init.irqs.trap_init = kvm_apf_trap_init;
 494
 495         if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
 496                 has_steal_clock = 1;
 497                 pv_time_ops.steal_clock = kvm_steal_clock;
 498         }
 499
 500         if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
 501                 apic_set_eoi_write(kvm_guest_apic_eoi_write);
 502
 503         if (kvmclock_vsyscall)
 504                 kvm_setup_vsyscall_timeinfo();
 505
 506 #ifdef CONFIG_SMP
 507         smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
 508         register_cpu_notifier(&kvm_cpu_notifier);
 509 #else
 510         kvm_guest_cpu_init();
 511 #endif
 512
 513         /*
 514          * Hard lockup detection is enabled by default. Disable it, as guests
 515          * can get false positives too easily, for example if the host is
 516          * overcommitted.
 517          */
 518         hardlockup_detector_disable();
 519 }
 520
 521 static noinline uint32_t __kvm_cpuid_base(void)
 522 {
 523         if (boot_cpu_data.cpuid_level < 0)
 524                 return 0;       /* So we don't blow up on old processors */
 525
 526         if (cpu_has_hypervisor)
 527                 return hypervisor_cpuid_base("KVMKVMKVM\0\0\0", 0);
 528
 529         return 0;
 530 }
 531
 532 static inline uint32_t kvm_cpuid_base(void)
 533 {
 534         static int kvm_cpuid_base = -1;
 535
 536         if (kvm_cpuid_base == -1)
 537                 kvm_cpuid_base = __kvm_cpuid_base();
 538
 539         return kvm_cpuid_base;
 540 }
 541
 542 bool kvm_para_available(void)
 543 {
 544         return kvm_cpuid_base() != 0;
 545 }
 546 EXPORT_SYMBOL_GPL(kvm_para_available);
 547
 548 unsigned int kvm_arch_para_features(void)
 549 {
 550         return cpuid_eax(kvm_cpuid_base() | KVM_CPUID_FEATURES);
 551 }
 552
 553 static uint32_t __init kvm_detect(void)
 554 {
 555         return kvm_cpuid_base();
 556 }
 557
 558 const struct hypervisor_x86 x86_hyper_kvm __refconst = {
 559         .name                   = "KVM",
 560         .detect                 = kvm_detect,
 561         .x2apic_available       = kvm_para_available,
 562 };
 563 EXPORT_SYMBOL_GPL(x86_hyper_kvm);
 564
 565 static __init int activate_jump_labels(void)
 566 {
 567         if (has_steal_clock) {
 568                 static_key_slow_inc(&paravirt_steal_enabled);
 569                 if (steal_acc)
 570                         static_key_slow_inc(&paravirt_steal_rq_enabled);
 571         }
 572
 573         return 0;
 574 }
 575 arch_initcall(activate_jump_labels);
 576
 577 #ifdef CONFIG_PARAVIRT_SPINLOCKS
 578
 579 /* Kick a cpu by its apicid. Used to wake up a halted vcpu */
 580 static void kvm_kick_cpu(int cpu)
 581 {
 582         int apicid;
 583         unsigned long flags = 0;
 584
 585         apicid = per_cpu(x86_cpu_to_apicid, cpu);
 586         kvm_hypercall2(KVM_HC_KICK_CPU, flags, apicid);
 587 }
 588
 589
 590 #ifdef CONFIG_QUEUED_SPINLOCKS
 591
 592 #include <asm/qspinlock.h>
 593
 594 static void kvm_wait(u8 *ptr, u8 val)
 595 {
 596         unsigned long flags;
 597
 598         if (in_nmi())
 599                 return;
 600
 601         local_irq_save(flags);
 602
 603         if (READ_ONCE(*ptr) != val)
 604                 goto out;
 605
 606         /*
 607          * halt until it's our turn and kicked. Note that we do safe halt
 608          * for irq enabled case to avoid hang when lock info is overwritten
 609          * in irq spinlock slowpath and no spurious interrupt occur to save us.
 610          */
 611         if (arch_irqs_disabled_flags(flags))
 612                 halt();
 613         else
 614                 safe_halt();
 615
 616 out:
 617         local_irq_restore(flags);
 618 }
 619
 620 #else /* !CONFIG_QUEUED_SPINLOCKS */
 621
 622 enum kvm_contention_stat {
 623         TAKEN_SLOW,
 624         TAKEN_SLOW_PICKUP,
 625         RELEASED_SLOW,
 626         RELEASED_SLOW_KICKED,
 627         NR_CONTENTION_STATS
 628 };
 629
 630 #ifdef CONFIG_KVM_DEBUG_FS
 631 #define HISTO_BUCKETS   30
 632
 633 static struct kvm_spinlock_stats
 634 {
 635         u32 contention_stats[NR_CONTENTION_STATS];
 636         u32 histo_spin_blocked[HISTO_BUCKETS+1];
 637         u64 time_blocked;
 638 } spinlock_stats;
 639
 640 static u8 zero_stats;
 641
 642 static inline void check_zero(void)
 643 {
 644         u8 ret;
 645         u8 old;
 646
 647         old = READ_ONCE(zero_stats);
 648         if (unlikely(old)) {
 649                 ret = cmpxchg(&zero_stats, old, 0);
 650                 /* This ensures only one fellow resets the stat */
 651                 if (ret == old)
 652                         memset(&spinlock_stats, 0, sizeof(spinlock_stats));
 653         }
 654 }
 655
 656 static inline void add_stats(enum kvm_contention_stat var, u32 val)
 657 {
 658         check_zero();
 659         spinlock_stats.contention_stats[var] += val;
 660 }
 661
 662
 663 static inline u64 spin_time_start(void)
 664 {
 665         return sched_clock();
 666 }
 667
 668 static void __spin_time_accum(u64 delta, u32 *array)
 669 {
 670         unsigned index;
 671
 672         index = ilog2(delta);
 673         check_zero();
 674
 675         if (index < HISTO_BUCKETS)
 676                 array[index]++;
 677         else
 678                 array[HISTO_BUCKETS]++;
 679 }
 680
 681 static inline void spin_time_accum_blocked(u64 start)
 682 {
 683         u32 delta;
 684
 685         delta = sched_clock() - start;
 686         __spin_time_accum(delta, spinlock_stats.histo_spin_blocked);
 687         spinlock_stats.time_blocked += delta;
 688 }
 689
 690 static struct dentry *d_spin_debug;
 691 static struct dentry *d_kvm_debug;
 692
 693 static struct dentry *kvm_init_debugfs(void)
 694 {
 695         d_kvm_debug = debugfs_create_dir("kvm-guest", NULL);
 696         if (!d_kvm_debug)
 697                 printk(KERN_WARNING "Could not create 'kvm' debugfs directory\n");
 698
 699         return d_kvm_debug;
 700 }
 701
 702 static int __init kvm_spinlock_debugfs(void)
 703 {
 704         struct dentry *d_kvm;
 705
 706         d_kvm = kvm_init_debugfs();
 707         if (d_kvm == NULL)
 708                 return -ENOMEM;
 709
 710         d_spin_debug = debugfs_create_dir("spinlocks", d_kvm);
 711
 712         debugfs_create_u8("zero_stats", 0644, d_spin_debug, &zero_stats);
 713
 714         debugfs_create_u32("taken_slow", 0444, d_spin_debug,
 715                    &spinlock_stats.contention_stats[TAKEN_SLOW]);
 716         debugfs_create_u32("taken_slow_pickup", 0444, d_spin_debug,
 717                    &spinlock_stats.contention_stats[TAKEN_SLOW_PICKUP]);
 718
 719         debugfs_create_u32("released_slow", 0444, d_spin_debug,
 720                    &spinlock_stats.contention_stats[RELEASED_SLOW]);
 721         debugfs_create_u32("released_slow_kicked", 0444, d_spin_debug,
 722                    &spinlock_stats.contention_stats[RELEASED_SLOW_KICKED]);
 723
 724         debugfs_create_u64("time_blocked", 0444, d_spin_debug,
 725                            &spinlock_stats.time_blocked);
 726
 727         debugfs_create_u32_array("histo_blocked", 0444, d_spin_debug,
 728                      spinlock_stats.histo_spin_blocked, HISTO_BUCKETS + 1);
 729
 730         return 0;
 731 }
 732 fs_initcall(kvm_spinlock_debugfs);
 733 #else  /* !CONFIG_KVM_DEBUG_FS */
 734 static inline void add_stats(enum kvm_contention_stat var, u32 val)
 735 {
 736 }
 737
 738 static inline u64 spin_time_start(void)
 739 {
 740         return 0;
 741 }
 742
 743 static inline void spin_time_accum_blocked(u64 start)
 744 {
 745 }
 746 #endif  /* CONFIG_KVM_DEBUG_FS */
 747
 748 struct kvm_lock_waiting {
 749         struct arch_spinlock *lock;
 750         __ticket_t want;
 751 };
 752
 753 /* cpus 'waiting' on a spinlock to become available */
 754 static cpumask_t waiting_cpus;
 755
 756 /* Track spinlock on which a cpu is waiting */
 757 static DEFINE_PER_CPU(struct kvm_lock_waiting, klock_waiting);
 758
 759 __visible void kvm_lock_spinning(struct arch_spinlock *lock, __ticket_t want)
 760 {
 761         struct kvm_lock_waiting *w;
 762         int cpu;
 763         u64 start;
 764         unsigned long flags;
 765         __ticket_t head;
 766
 767         if (in_nmi())
 768                 return;
 769
 770         w = this_cpu_ptr(&klock_waiting);
 771         cpu = smp_processor_id();
 772         start = spin_time_start();
 773
 774         /*
 775          * Make sure an interrupt handler can't upset things in a
 776          * partially setup state.
 777          */
 778         local_irq_save(flags);
 779
 780         /*
 781          * The ordering protocol on this is that the "lock" pointer
 782          * may only be set non-NULL if the "want" ticket is correct.
 783          * If we're updating "want", we must first clear "lock".
 784          */
 785         w->lock = NULL;
 786         smp_wmb();
 787         w->want = want;
 788         smp_wmb();
 789         w->lock = lock;
 790
 791         add_stats(TAKEN_SLOW, 1);
 792
 793         /*
 794          * This uses set_bit, which is atomic but we should not rely on its
 795          * reordering gurantees. So barrier is needed after this call.
 796          */
 797         cpumask_set_cpu(cpu, &waiting_cpus);
 798
 799         barrier();
 800
 801         /*
 802          * Mark entry to slowpath before doing the pickup test to make
 803          * sure we don't deadlock with an unlocker.
 804          */
 805         __ticket_enter_slowpath(lock);
 806
 807         /* make sure enter_slowpath, which is atomic does not cross the read */
 808         smp_mb__after_atomic();
 809
 810         /*
 811          * check again make sure it didn't become free while
 812          * we weren't looking.
 813          */
 814         head = READ_ONCE(lock->tickets.head);
 815         if (__tickets_equal(head, want)) {
 816                 add_stats(TAKEN_SLOW_PICKUP, 1);
 817                 goto out;
 818         }
 819
 820         /*
 821          * halt until it's our turn and kicked. Note that we do safe halt
 822          * for irq enabled case to avoid hang when lock info is overwritten
 823          * in irq spinlock slowpath and no spurious interrupt occur to save us.
 824          */
 825         if (arch_irqs_disabled_flags(flags))
 826                 halt();
 827         else
 828                 safe_halt();
 829
 830 out:
 831         cpumask_clear_cpu(cpu, &waiting_cpus);
 832         w->lock = NULL;
 833         local_irq_restore(flags);
 834         spin_time_accum_blocked(start);
 835 }
 836 PV_CALLEE_SAVE_REGS_THUNK(kvm_lock_spinning);
 837
 838 /* Kick vcpu waiting on @lock->head to reach value @ticket */
 839 static void kvm_unlock_kick(struct arch_spinlock *lock, __ticket_t ticket)
 840 {
 841         int cpu;
 842
 843         add_stats(RELEASED_SLOW, 1);
 844         for_each_cpu(cpu, &waiting_cpus) {
 845                 const struct kvm_lock_waiting *w = &per_cpu(klock_waiting, cpu);
 846                 if (READ_ONCE(w->lock) == lock &&
 847                     READ_ONCE(w->want) == ticket) {
 848                         add_stats(RELEASED_SLOW_KICKED, 1);
 849                         kvm_kick_cpu(cpu);
 850                         break;
 851                 }
 852         }
 853 }
 854
 855 #endif /* !CONFIG_QUEUED_SPINLOCKS */
 856
 857 /*
 858  * Setup pv_lock_ops to exploit KVM_FEATURE_PV_UNHALT if present.
 859  */
 860 void __init kvm_spinlock_init(void)
 861 {
 862         if (!kvm_para_available())
 863                 return;
 864         /* Does host kernel support KVM_FEATURE_PV_UNHALT? */
 865         if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
 866                 return;
 867
 868 #ifdef CONFIG_QUEUED_SPINLOCKS
 869         __pv_init_lock_hash();
 870         pv_lock_ops.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
 871         pv_lock_ops.queued_spin_unlock = PV_CALLEE_SAVE(__pv_queued_spin_unlock);
 872         pv_lock_ops.wait = kvm_wait;
 873         pv_lock_ops.kick = kvm_kick_cpu;
 874 #else /* !CONFIG_QUEUED_SPINLOCKS */
 875         pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(kvm_lock_spinning);
 876         pv_lock_ops.unlock_kick = kvm_unlock_kick;
 877 #endif
 878 }
 879
 880 static __init int kvm_spinlock_init_jump(void)
 881 {
 882         if (!kvm_para_available())
 883                 return 0;
 884         if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
 885                 return 0;
 886
 887         static_key_slow_inc(&paravirt_ticketlocks_enabled);
 888         printk(KERN_INFO "KVM setup paravirtual spinlock\n");
 889
 890         return 0;
 891 }
 892 early_initcall(kvm_spinlock_init_jump);
 893
 894 #endif  /* CONFIG_PARAVIRT_SPINLOCKS */