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         memset(st, 0, sizeof(*st));
 305
 306         wrmsrl(MSR_KVM_STEAL_TIME, (slow_virt_to_phys(st) | KVM_MSR_ENABLED));
 307         pr_info("kvm-stealtime: cpu %d, msr %llx\n",
 308                 cpu, (unsigned long long) slow_virt_to_phys(st));
 309 }
 310
 311 static DEFINE_PER_CPU(unsigned long, kvm_apic_eoi) = KVM_PV_EOI_DISABLED;
 312
 313 static void kvm_guest_apic_eoi_write(u32 reg, u32 val)
 314 {
 315         /**
 316          * This relies on __test_and_clear_bit to modify the memory
 317          * in a way that is atomic with respect to the local CPU.
 318          * The hypervisor only accesses this memory from the local CPU so
 319          * there's no need for lock or memory barriers.
 320          * An optimization barrier is implied in apic write.
 321          */
 322         if (__test_and_clear_bit(KVM_PV_EOI_BIT, this_cpu_ptr(&kvm_apic_eoi)))
 323                 return;
 324         apic_write(APIC_EOI, APIC_EOI_ACK);
 325 }
 326
 327 static void kvm_guest_cpu_init(void)
 328 {
 329         if (!kvm_para_available())
 330                 return;
 331
 332         if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF) && kvmapf) {
 333                 u64 pa = slow_virt_to_phys(this_cpu_ptr(&apf_reason));
 334
 335 #ifdef CONFIG_PREEMPT
 336                 pa |= KVM_ASYNC_PF_SEND_ALWAYS;
 337 #endif
 338                 wrmsrl(MSR_KVM_ASYNC_PF_EN, pa | KVM_ASYNC_PF_ENABLED);
 339                 __this_cpu_write(apf_reason.enabled, 1);
 340                 printk(KERN_INFO"KVM setup async PF for cpu %d\n",
 341                        smp_processor_id());
 342         }
 343
 344         if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) {
 345                 unsigned long pa;
 346                 /* Size alignment is implied but just to make it explicit. */
 347                 BUILD_BUG_ON(__alignof__(kvm_apic_eoi) < 4);
 348                 __this_cpu_write(kvm_apic_eoi, 0);
 349                 pa = slow_virt_to_phys(this_cpu_ptr(&kvm_apic_eoi))
 350                         | KVM_MSR_ENABLED;
 351                 wrmsrl(MSR_KVM_PV_EOI_EN, pa);
 352         }
 353
 354         if (has_steal_clock)
 355                 kvm_register_steal_time();
 356 }
 357
 358 static void kvm_pv_disable_apf(void)
 359 {
 360         if (!__this_cpu_read(apf_reason.enabled))
 361                 return;
 362
 363         wrmsrl(MSR_KVM_ASYNC_PF_EN, 0);
 364         __this_cpu_write(apf_reason.enabled, 0);
 365
 366         printk(KERN_INFO"Unregister pv shared memory for cpu %d\n",
 367                smp_processor_id());
 368 }
 369
 370 static void kvm_pv_guest_cpu_reboot(void *unused)
 371 {
 372         /*
 373          * We disable PV EOI before we load a new kernel by kexec,
 374          * since MSR_KVM_PV_EOI_EN stores a pointer into old kernel's memory.
 375          * New kernel can re-enable when it boots.
 376          */
 377         if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
 378                 wrmsrl(MSR_KVM_PV_EOI_EN, 0);
 379         kvm_pv_disable_apf();
 380         kvm_disable_steal_time();
 381 }
 382
 383 static int kvm_pv_reboot_notify(struct notifier_block *nb,
 384                                 unsigned long code, void *unused)
 385 {
 386         if (code == SYS_RESTART)
 387                 on_each_cpu(kvm_pv_guest_cpu_reboot, NULL, 1);
 388         return NOTIFY_DONE;
 389 }
 390
 391 static struct notifier_block kvm_pv_reboot_nb = {
 392         .notifier_call = kvm_pv_reboot_notify,
 393 };
 394
 395 static u64 kvm_steal_clock(int cpu)
 396 {
 397         u64 steal;
 398         struct kvm_steal_time *src;
 399         int version;
 400
 401         src = &per_cpu(steal_time, cpu);
 402         do {
 403                 version = src->version;
 404                 rmb();
 405                 steal = src->steal;
 406                 rmb();
 407         } while ((version & 1) || (version != src->version));
 408
 409         return steal;
 410 }
 411
 412 void kvm_disable_steal_time(void)
 413 {
 414         if (!has_steal_clock)
 415                 return;
 416
 417         wrmsr(MSR_KVM_STEAL_TIME, 0, 0);
 418 }
 419
 420 #ifdef CONFIG_SMP
 421 static void __init kvm_smp_prepare_boot_cpu(void)
 422 {
 423         kvm_guest_cpu_init();
 424         native_smp_prepare_boot_cpu();
 425         kvm_spinlock_init();
 426 }
 427
 428 static void kvm_guest_cpu_online(void *dummy)
 429 {
 430         kvm_guest_cpu_init();
 431 }
 432
 433 static void kvm_guest_cpu_offline(void *dummy)
 434 {
 435         kvm_disable_steal_time();
 436         if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
 437                 wrmsrl(MSR_KVM_PV_EOI_EN, 0);
 438         kvm_pv_disable_apf();
 439         apf_task_wake_all();
 440 }
 441
 442 static int kvm_cpu_notify(struct notifier_block *self, unsigned long action,
 443                           void *hcpu)
 444 {
 445         int cpu = (unsigned long)hcpu;
 446         switch (action) {
 447         case CPU_ONLINE:
 448         case CPU_DOWN_FAILED:
 449         case CPU_ONLINE_FROZEN:
 450                 smp_call_function_single(cpu, kvm_guest_cpu_online, NULL, 0);
 451                 break;
 452         case CPU_DOWN_PREPARE:
 453         case CPU_DOWN_PREPARE_FROZEN:
 454                 smp_call_function_single(cpu, kvm_guest_cpu_offline, NULL, 1);
 455                 break;
 456         default:
 457                 break;
 458         }
 459         return NOTIFY_OK;
 460 }
 461
 462 static struct notifier_block kvm_cpu_notifier = {
 463         .notifier_call  = kvm_cpu_notify,
 464 };
 465 #endif
 466
 467 static void __init kvm_apf_trap_init(void)
 468 {
 469         set_intr_gate(14, async_page_fault);
 470 }
 471
 472 void __init kvm_guest_init(void)
 473 {
 474         int i;
 475
 476         if (!kvm_para_available())
 477                 return;
 478
 479         paravirt_ops_setup();
 480         register_reboot_notifier(&kvm_pv_reboot_nb);
 481         for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++)
 482                 raw_spin_lock_init(&async_pf_sleepers[i].lock);
 483         if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF))
 484                 x86_init.irqs.trap_init = kvm_apf_trap_init;
 485
 486         if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
 487                 has_steal_clock = 1;
 488                 pv_time_ops.steal_clock = kvm_steal_clock;
 489         }
 490
 491         if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
 492                 apic_set_eoi_write(kvm_guest_apic_eoi_write);
 493
 494         if (kvmclock_vsyscall)
 495                 kvm_setup_vsyscall_timeinfo();
 496
 497 #ifdef CONFIG_SMP
 498         smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
 499         register_cpu_notifier(&kvm_cpu_notifier);
 500 #else
 501         kvm_guest_cpu_init();
 502 #endif
 503
 504         /*
 505          * Hard lockup detection is enabled by default. Disable it, as guests
 506          * can get false positives too easily, for example if the host is
 507          * overcommitted.
 508          */
 509         hardlockup_detector_disable();
 510 }
 511
 512 static noinline uint32_t __kvm_cpuid_base(void)
 513 {
 514         if (boot_cpu_data.cpuid_level < 0)
 515                 return 0;       /* So we don't blow up on old processors */
 516
 517         if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
 518                 return hypervisor_cpuid_base("KVMKVMKVM\0\0\0", 0);
 519
 520         return 0;
 521 }
 522
 523 static inline uint32_t kvm_cpuid_base(void)
 524 {
 525         static int kvm_cpuid_base = -1;
 526
 527         if (kvm_cpuid_base == -1)
 528                 kvm_cpuid_base = __kvm_cpuid_base();
 529
 530         return kvm_cpuid_base;
 531 }
 532
 533 bool kvm_para_available(void)
 534 {
 535         return kvm_cpuid_base() != 0;
 536 }
 537 EXPORT_SYMBOL_GPL(kvm_para_available);
 538
 539 unsigned int kvm_arch_para_features(void)
 540 {
 541         return cpuid_eax(kvm_cpuid_base() | KVM_CPUID_FEATURES);
 542 }
 543
 544 static uint32_t __init kvm_detect(void)
 545 {
 546         return kvm_cpuid_base();
 547 }
 548
 549 const struct hypervisor_x86 x86_hyper_kvm __refconst = {
 550         .name                   = "KVM",
 551         .detect                 = kvm_detect,
 552         .x2apic_available       = kvm_para_available,
 553 };
 554 EXPORT_SYMBOL_GPL(x86_hyper_kvm);
 555
 556 static __init int activate_jump_labels(void)
 557 {
 558         if (has_steal_clock) {
 559                 static_key_slow_inc(&paravirt_steal_enabled);
 560                 if (steal_acc)
 561                         static_key_slow_inc(&paravirt_steal_rq_enabled);
 562         }
 563
 564         return 0;
 565 }
 566 arch_initcall(activate_jump_labels);
 567
 568 #ifdef CONFIG_PARAVIRT_SPINLOCKS
 569
 570 /* Kick a cpu by its apicid. Used to wake up a halted vcpu */
 571 static void kvm_kick_cpu(int cpu)
 572 {
 573         int apicid;
 574         unsigned long flags = 0;
 575
 576         apicid = per_cpu(x86_cpu_to_apicid, cpu);
 577         kvm_hypercall2(KVM_HC_KICK_CPU, flags, apicid);
 578 }
 579
 580
 581 #ifdef CONFIG_QUEUED_SPINLOCKS
 582
 583 #include <asm/qspinlock.h>
 584
 585 static void kvm_wait(u8 *ptr, u8 val)
 586 {
 587         unsigned long flags;
 588
 589         if (in_nmi())
 590                 return;
 591
 592         local_irq_save(flags);
 593
 594         if (READ_ONCE(*ptr) != val)
 595                 goto out;
 596
 597         /*
 598          * halt until it's our turn and kicked. Note that we do safe halt
 599          * for irq enabled case to avoid hang when lock info is overwritten
 600          * in irq spinlock slowpath and no spurious interrupt occur to save us.
 601          */
 602         if (arch_irqs_disabled_flags(flags))
 603                 halt();
 604         else
 605                 safe_halt();
 606
 607 out:
 608         local_irq_restore(flags);
 609 }
 610
 611 #else /* !CONFIG_QUEUED_SPINLOCKS */
 612
 613 enum kvm_contention_stat {
 614         TAKEN_SLOW,
 615         TAKEN_SLOW_PICKUP,
 616         RELEASED_SLOW,
 617         RELEASED_SLOW_KICKED,
 618         NR_CONTENTION_STATS
 619 };
 620
 621 #ifdef CONFIG_KVM_DEBUG_FS
 622 #define HISTO_BUCKETS   30
 623
 624 static struct kvm_spinlock_stats
 625 {
 626         u32 contention_stats[NR_CONTENTION_STATS];
 627         u32 histo_spin_blocked[HISTO_BUCKETS+1];
 628         u64 time_blocked;
 629 } spinlock_stats;
 630
 631 static u8 zero_stats;
 632
 633 static inline void check_zero(void)
 634 {
 635         u8 ret;
 636         u8 old;
 637
 638         old = READ_ONCE(zero_stats);
 639         if (unlikely(old)) {
 640                 ret = cmpxchg(&zero_stats, old, 0);
 641                 /* This ensures only one fellow resets the stat */
 642                 if (ret == old)
 643                         memset(&spinlock_stats, 0, sizeof(spinlock_stats));
 644         }
 645 }
 646
 647 static inline void add_stats(enum kvm_contention_stat var, u32 val)
 648 {
 649         check_zero();
 650         spinlock_stats.contention_stats[var] += val;
 651 }
 652
 653
 654 static inline u64 spin_time_start(void)
 655 {
 656         return sched_clock();
 657 }
 658
 659 static void __spin_time_accum(u64 delta, u32 *array)
 660 {
 661         unsigned index;
 662
 663         index = ilog2(delta);
 664         check_zero();
 665
 666         if (index < HISTO_BUCKETS)
 667                 array[index]++;
 668         else
 669                 array[HISTO_BUCKETS]++;
 670 }
 671
 672 static inline void spin_time_accum_blocked(u64 start)
 673 {
 674         u32 delta;
 675
 676         delta = sched_clock() - start;
 677         __spin_time_accum(delta, spinlock_stats.histo_spin_blocked);
 678         spinlock_stats.time_blocked += delta;
 679 }
 680
 681 static struct dentry *d_spin_debug;
 682 static struct dentry *d_kvm_debug;
 683
 684 static struct dentry *kvm_init_debugfs(void)
 685 {
 686         d_kvm_debug = debugfs_create_dir("kvm-guest", NULL);
 687         if (!d_kvm_debug)
 688                 printk(KERN_WARNING "Could not create 'kvm' debugfs directory\n");
 689
 690         return d_kvm_debug;
 691 }
 692
 693 static int __init kvm_spinlock_debugfs(void)
 694 {
 695         struct dentry *d_kvm;
 696
 697         d_kvm = kvm_init_debugfs();
 698         if (d_kvm == NULL)
 699                 return -ENOMEM;
 700
 701         d_spin_debug = debugfs_create_dir("spinlocks", d_kvm);
 702
 703         debugfs_create_u8("zero_stats", 0644, d_spin_debug, &zero_stats);
 704
 705         debugfs_create_u32("taken_slow", 0444, d_spin_debug,
 706                    &spinlock_stats.contention_stats[TAKEN_SLOW]);
 707         debugfs_create_u32("taken_slow_pickup", 0444, d_spin_debug,
 708                    &spinlock_stats.contention_stats[TAKEN_SLOW_PICKUP]);
 709
 710         debugfs_create_u32("released_slow", 0444, d_spin_debug,
 711                    &spinlock_stats.contention_stats[RELEASED_SLOW]);
 712         debugfs_create_u32("released_slow_kicked", 0444, d_spin_debug,
 713                    &spinlock_stats.contention_stats[RELEASED_SLOW_KICKED]);
 714
 715         debugfs_create_u64("time_blocked", 0444, d_spin_debug,
 716                            &spinlock_stats.time_blocked);
 717
 718         debugfs_create_u32_array("histo_blocked", 0444, d_spin_debug,
 719                      spinlock_stats.histo_spin_blocked, HISTO_BUCKETS + 1);
 720
 721         return 0;
 722 }
 723 fs_initcall(kvm_spinlock_debugfs);
 724 #else  /* !CONFIG_KVM_DEBUG_FS */
 725 static inline void add_stats(enum kvm_contention_stat var, u32 val)
 726 {
 727 }
 728
 729 static inline u64 spin_time_start(void)
 730 {
 731         return 0;
 732 }
 733
 734 static inline void spin_time_accum_blocked(u64 start)
 735 {
 736 }
 737 #endif  /* CONFIG_KVM_DEBUG_FS */
 738
 739 struct kvm_lock_waiting {
 740         struct arch_spinlock *lock;
 741         __ticket_t want;
 742 };
 743
 744 /* cpus 'waiting' on a spinlock to become available */
 745 static cpumask_t waiting_cpus;
 746
 747 /* Track spinlock on which a cpu is waiting */
 748 static DEFINE_PER_CPU(struct kvm_lock_waiting, klock_waiting);
 749
 750 __visible void kvm_lock_spinning(struct arch_spinlock *lock, __ticket_t want)
 751 {
 752         struct kvm_lock_waiting *w;
 753         int cpu;
 754         u64 start;
 755         unsigned long flags;
 756         __ticket_t head;
 757
 758         if (in_nmi())
 759                 return;
 760
 761         w = this_cpu_ptr(&klock_waiting);
 762         cpu = smp_processor_id();
 763         start = spin_time_start();
 764
 765         /*
 766          * Make sure an interrupt handler can't upset things in a
 767          * partially setup state.
 768          */
 769         local_irq_save(flags);
 770
 771         /*
 772          * The ordering protocol on this is that the "lock" pointer
 773          * may only be set non-NULL if the "want" ticket is correct.
 774          * If we're updating "want", we must first clear "lock".
 775          */
 776         w->lock = NULL;
 777         smp_wmb();
 778         w->want = want;
 779         smp_wmb();
 780         w->lock = lock;
 781
 782         add_stats(TAKEN_SLOW, 1);
 783
 784         /*
 785          * This uses set_bit, which is atomic but we should not rely on its
 786          * reordering gurantees. So barrier is needed after this call.
 787          */
 788         cpumask_set_cpu(cpu, &waiting_cpus);
 789
 790         barrier();
 791
 792         /*
 793          * Mark entry to slowpath before doing the pickup test to make
 794          * sure we don't deadlock with an unlocker.
 795          */
 796         __ticket_enter_slowpath(lock);
 797
 798         /* make sure enter_slowpath, which is atomic does not cross the read */
 799         smp_mb__after_atomic();
 800
 801         /*
 802          * check again make sure it didn't become free while
 803          * we weren't looking.
 804          */
 805         head = READ_ONCE(lock->tickets.head);
 806         if (__tickets_equal(head, want)) {
 807                 add_stats(TAKEN_SLOW_PICKUP, 1);
 808                 goto out;
 809         }
 810
 811         /*
 812          * halt until it's our turn and kicked. Note that we do safe halt
 813          * for irq enabled case to avoid hang when lock info is overwritten
 814          * in irq spinlock slowpath and no spurious interrupt occur to save us.
 815          */
 816         if (arch_irqs_disabled_flags(flags))
 817                 halt();
 818         else
 819                 safe_halt();
 820
 821 out:
 822         cpumask_clear_cpu(cpu, &waiting_cpus);
 823         w->lock = NULL;
 824         local_irq_restore(flags);
 825         spin_time_accum_blocked(start);
 826 }
 827 PV_CALLEE_SAVE_REGS_THUNK(kvm_lock_spinning);
 828
 829 /* Kick vcpu waiting on @lock->head to reach value @ticket */
 830 static void kvm_unlock_kick(struct arch_spinlock *lock, __ticket_t ticket)
 831 {
 832         int cpu;
 833
 834         add_stats(RELEASED_SLOW, 1);
 835         for_each_cpu(cpu, &waiting_cpus) {
 836                 const struct kvm_lock_waiting *w = &per_cpu(klock_waiting, cpu);
 837                 if (READ_ONCE(w->lock) == lock &&
 838                     READ_ONCE(w->want) == ticket) {
 839                         add_stats(RELEASED_SLOW_KICKED, 1);
 840                         kvm_kick_cpu(cpu);
 841                         break;
 842                 }
 843         }
 844 }
 845
 846 #endif /* !CONFIG_QUEUED_SPINLOCKS */
 847
 848 /*
 849  * Setup pv_lock_ops to exploit KVM_FEATURE_PV_UNHALT if present.
 850  */
 851 void __init kvm_spinlock_init(void)
 852 {
 853         if (!kvm_para_available())
 854                 return;
 855         /* Does host kernel support KVM_FEATURE_PV_UNHALT? */
 856         if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
 857                 return;
 858
 859 #ifdef CONFIG_QUEUED_SPINLOCKS
 860         __pv_init_lock_hash();
 861         pv_lock_ops.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
 862         pv_lock_ops.queued_spin_unlock = PV_CALLEE_SAVE(__pv_queued_spin_unlock);
 863         pv_lock_ops.wait = kvm_wait;
 864         pv_lock_ops.kick = kvm_kick_cpu;
 865 #else /* !CONFIG_QUEUED_SPINLOCKS */
 866         pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(kvm_lock_spinning);
 867         pv_lock_ops.unlock_kick = kvm_unlock_kick;
 868 #endif
 869 }
 870
 871 static __init int kvm_spinlock_init_jump(void)
 872 {
 873         if (!kvm_para_available())
 874                 return 0;
 875         if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
 876                 return 0;
 877
 878         static_key_slow_inc(&paravirt_ticketlocks_enabled);
 879         printk(KERN_INFO "KVM setup paravirtual spinlock\n");
 880
 881         return 0;
 882 }
 883 early_initcall(kvm_spinlock_init_jump);
 884
 885 #endif  /* CONFIG_PARAVIRT_SPINLOCKS */