kernel/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         /*
 289          * KVM isn't paravirt in the sense of paravirt_enabled.  A KVM
 290          * guest kernel works like a bare metal kernel with additional
 291          * features, and paravirt_enabled is about features that are
 292          * missing.
 293          */
 294         pv_info.paravirt_enabled = 0;
 295
 296         if (kvm_para_has_feature(KVM_FEATURE_NOP_IO_DELAY))
 297                 pv_cpu_ops.io_delay = kvm_io_delay;
 298
 299 #ifdef CONFIG_X86_IO_APIC
 300         no_timer_check = 1;
 301 #endif
 302 }
 303
 304 static void kvm_register_steal_time(void)
 305 {
 306         int cpu = smp_processor_id();
 307         struct kvm_steal_time *st = &per_cpu(steal_time, cpu);
 308
 309         if (!has_steal_clock)
 310                 return;
 311
 312         memset(st, 0, sizeof(*st));
 313
 314         wrmsrl(MSR_KVM_STEAL_TIME, (slow_virt_to_phys(st) | KVM_MSR_ENABLED));
 315         pr_info("kvm-stealtime: cpu %d, msr %llx\n",
 316                 cpu, (unsigned long long) slow_virt_to_phys(st));
 317 }
 318
 319 static DEFINE_PER_CPU(unsigned long, kvm_apic_eoi) = KVM_PV_EOI_DISABLED;
 320
 321 static void kvm_guest_apic_eoi_write(u32 reg, u32 val)
 322 {
 323         /**
 324          * This relies on __test_and_clear_bit to modify the memory
 325          * in a way that is atomic with respect to the local CPU.
 326          * The hypervisor only accesses this memory from the local CPU so
 327          * there's no need for lock or memory barriers.
 328          * An optimization barrier is implied in apic write.
 329          */
 330         if (__test_and_clear_bit(KVM_PV_EOI_BIT, this_cpu_ptr(&kvm_apic_eoi)))
 331                 return;
 332         apic_write(APIC_EOI, APIC_EOI_ACK);
 333 }
 334
 335 static void kvm_guest_cpu_init(void)
 336 {
 337         if (!kvm_para_available())
 338                 return;
 339
 340         if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF) && kvmapf) {
 341                 u64 pa = slow_virt_to_phys(this_cpu_ptr(&apf_reason));
 342
 343 #ifdef CONFIG_PREEMPT
 344                 pa |= KVM_ASYNC_PF_SEND_ALWAYS;
 345 #endif
 346                 wrmsrl(MSR_KVM_ASYNC_PF_EN, pa | KVM_ASYNC_PF_ENABLED);
 347                 __this_cpu_write(apf_reason.enabled, 1);
 348                 printk(KERN_INFO"KVM setup async PF for cpu %d\n",
 349                        smp_processor_id());
 350         }
 351
 352         if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) {
 353                 unsigned long pa;
 354                 /* Size alignment is implied but just to make it explicit. */
 355                 BUILD_BUG_ON(__alignof__(kvm_apic_eoi) < 4);
 356                 __this_cpu_write(kvm_apic_eoi, 0);
 357                 pa = slow_virt_to_phys(this_cpu_ptr(&kvm_apic_eoi))
 358                         | KVM_MSR_ENABLED;
 359                 wrmsrl(MSR_KVM_PV_EOI_EN, pa);
 360         }
 361
 362         if (has_steal_clock)
 363                 kvm_register_steal_time();
 364 }
 365
 366 static void kvm_pv_disable_apf(void)
 367 {
 368         if (!__this_cpu_read(apf_reason.enabled))
 369                 return;
 370
 371         wrmsrl(MSR_KVM_ASYNC_PF_EN, 0);
 372         __this_cpu_write(apf_reason.enabled, 0);
 373
 374         printk(KERN_INFO"Unregister pv shared memory for cpu %d\n",
 375                smp_processor_id());
 376 }
 377
 378 static void kvm_pv_guest_cpu_reboot(void *unused)
 379 {
 380         /*
 381          * We disable PV EOI before we load a new kernel by kexec,
 382          * since MSR_KVM_PV_EOI_EN stores a pointer into old kernel's memory.
 383          * New kernel can re-enable when it boots.
 384          */
 385         if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
 386                 wrmsrl(MSR_KVM_PV_EOI_EN, 0);
 387         kvm_pv_disable_apf();
 388         kvm_disable_steal_time();
 389 }
 390
 391 static int kvm_pv_reboot_notify(struct notifier_block *nb,
 392                                 unsigned long code, void *unused)
 393 {
 394         if (code == SYS_RESTART)
 395                 on_each_cpu(kvm_pv_guest_cpu_reboot, NULL, 1);
 396         return NOTIFY_DONE;
 397 }
 398
 399 static struct notifier_block kvm_pv_reboot_nb = {
 400         .notifier_call = kvm_pv_reboot_notify,
 401 };
 402
 403 static u64 kvm_steal_clock(int cpu)
 404 {
 405         u64 steal;
 406         struct kvm_steal_time *src;
 407         int version;
 408
 409         src = &per_cpu(steal_time, cpu);
 410         do {
 411                 version = src->version;
 412                 rmb();
 413                 steal = src->steal;
 414                 rmb();
 415         } while ((version & 1) || (version != src->version));
 416
 417         return steal;
 418 }
 419
 420 void kvm_disable_steal_time(void)
 421 {
 422         if (!has_steal_clock)
 423                 return;
 424
 425         wrmsr(MSR_KVM_STEAL_TIME, 0, 0);
 426 }
 427
 428 #ifdef CONFIG_SMP
 429 static void __init kvm_smp_prepare_boot_cpu(void)
 430 {
 431         kvm_guest_cpu_init();
 432         native_smp_prepare_boot_cpu();
 433         kvm_spinlock_init();
 434 }
 435
 436 static void kvm_guest_cpu_online(void *dummy)
 437 {
 438         kvm_guest_cpu_init();
 439 }
 440
 441 static void kvm_guest_cpu_offline(void *dummy)
 442 {
 443         kvm_disable_steal_time();
 444         if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
 445                 wrmsrl(MSR_KVM_PV_EOI_EN, 0);
 446         kvm_pv_disable_apf();
 447         apf_task_wake_all();
 448 }
 449
 450 static int kvm_cpu_notify(struct notifier_block *self, unsigned long action,
 451                           void *hcpu)
 452 {
 453         int cpu = (unsigned long)hcpu;
 454         switch (action) {
 455         case CPU_ONLINE:
 456         case CPU_DOWN_FAILED:
 457         case CPU_ONLINE_FROZEN:
 458                 smp_call_function_single(cpu, kvm_guest_cpu_online, NULL, 0);
 459                 break;
 460         case CPU_DOWN_PREPARE:
 461         case CPU_DOWN_PREPARE_FROZEN:
 462                 smp_call_function_single(cpu, kvm_guest_cpu_offline, NULL, 1);
 463                 break;
 464         default:
 465                 break;
 466         }
 467         return NOTIFY_OK;
 468 }
 469
 470 static struct notifier_block kvm_cpu_notifier = {
 471         .notifier_call  = kvm_cpu_notify,
 472 };
 473 #endif
 474
 475 static void __init kvm_apf_trap_init(void)
 476 {
 477         set_intr_gate(14, async_page_fault);
 478 }
 479
 480 void __init kvm_guest_init(void)
 481 {
 482         int i;
 483
 484         if (!kvm_para_available())
 485                 return;
 486
 487         paravirt_ops_setup();
 488         register_reboot_notifier(&kvm_pv_reboot_nb);
 489         for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++)
 490                 raw_spin_lock_init(&async_pf_sleepers[i].lock);
 491         if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF))
 492                 x86_init.irqs.trap_init = kvm_apf_trap_init;
 493
 494         if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
 495                 has_steal_clock = 1;
 496                 pv_time_ops.steal_clock = kvm_steal_clock;
 497         }
 498
 499         if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
 500                 apic_set_eoi_write(kvm_guest_apic_eoi_write);
 501
 502         if (kvmclock_vsyscall)
 503                 kvm_setup_vsyscall_timeinfo();
 504
 505 #ifdef CONFIG_SMP
 506         smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
 507         register_cpu_notifier(&kvm_cpu_notifier);
 508 #else
 509         kvm_guest_cpu_init();
 510 #endif
 511
 512         /*
 513          * Hard lockup detection is enabled by default. Disable it, as guests
 514          * can get false positives too easily, for example if the host is
 515          * overcommitted.
 516          */
 517         hardlockup_detector_disable();
 518 }
 519
 520 static noinline uint32_t __kvm_cpuid_base(void)
 521 {
 522         if (boot_cpu_data.cpuid_level < 0)
 523                 return 0;       /* So we don't blow up on old processors */
 524
 525         if (cpu_has_hypervisor)
 526                 return hypervisor_cpuid_base("KVMKVMKVM\0\0\0", 0);
 527
 528         return 0;
 529 }
 530
 531 static inline uint32_t kvm_cpuid_base(void)
 532 {
 533         static int kvm_cpuid_base = -1;
 534
 535         if (kvm_cpuid_base == -1)
 536                 kvm_cpuid_base = __kvm_cpuid_base();
 537
 538         return kvm_cpuid_base;
 539 }
 540
 541 bool kvm_para_available(void)
 542 {
 543         return kvm_cpuid_base() != 0;
 544 }
 545 EXPORT_SYMBOL_GPL(kvm_para_available);
 546
 547 unsigned int kvm_arch_para_features(void)
 548 {
 549         return cpuid_eax(kvm_cpuid_base() | KVM_CPUID_FEATURES);
 550 }
 551
 552 static uint32_t __init kvm_detect(void)
 553 {
 554         return kvm_cpuid_base();
 555 }
 556
 557 const struct hypervisor_x86 x86_hyper_kvm __refconst = {
 558         .name                   = "KVM",
 559         .detect                 = kvm_detect,
 560         .x2apic_available       = kvm_para_available,
 561 };
 562 EXPORT_SYMBOL_GPL(x86_hyper_kvm);
 563
 564 static __init int activate_jump_labels(void)
 565 {
 566         if (has_steal_clock) {
 567                 static_key_slow_inc(&paravirt_steal_enabled);
 568                 if (steal_acc)
 569                         static_key_slow_inc(&paravirt_steal_rq_enabled);
 570         }
 571
 572         return 0;
 573 }
 574 arch_initcall(activate_jump_labels);
 575
 576 #ifdef CONFIG_PARAVIRT_SPINLOCKS
 577
 578 /* Kick a cpu by its apicid. Used to wake up a halted vcpu */
 579 static void kvm_kick_cpu(int cpu)
 580 {
 581         int apicid;
 582         unsigned long flags = 0;
 583
 584         apicid = per_cpu(x86_cpu_to_apicid, cpu);
 585         kvm_hypercall2(KVM_HC_KICK_CPU, flags, apicid);
 586 }
 587
 588
 589 #ifdef CONFIG_QUEUED_SPINLOCKS
 590
 591 #include <asm/qspinlock.h>
 592
 593 static void kvm_wait(u8 *ptr, u8 val)
 594 {
 595         unsigned long flags;
 596
 597         if (in_nmi())
 598                 return;
 599
 600         local_irq_save(flags);
 601
 602         if (READ_ONCE(*ptr) != val)
 603                 goto out;
 604
 605         /*
 606          * halt until it's our turn and kicked. Note that we do safe halt
 607          * for irq enabled case to avoid hang when lock info is overwritten
 608          * in irq spinlock slowpath and no spurious interrupt occur to save us.
 609          */
 610         if (arch_irqs_disabled_flags(flags))
 611                 halt();
 612         else
 613                 safe_halt();
 614
 615 out:
 616         local_irq_restore(flags);
 617 }
 618
 619 #else /* !CONFIG_QUEUED_SPINLOCKS */
 620
 621 enum kvm_contention_stat {
 622         TAKEN_SLOW,
 623         TAKEN_SLOW_PICKUP,
 624         RELEASED_SLOW,
 625         RELEASED_SLOW_KICKED,
 626         NR_CONTENTION_STATS
 627 };
 628
 629 #ifdef CONFIG_KVM_DEBUG_FS
 630 #define HISTO_BUCKETS   30
 631
 632 static struct kvm_spinlock_stats
 633 {
 634         u32 contention_stats[NR_CONTENTION_STATS];
 635         u32 histo_spin_blocked[HISTO_BUCKETS+1];
 636         u64 time_blocked;
 637 } spinlock_stats;
 638
 639 static u8 zero_stats;
 640
 641 static inline void check_zero(void)
 642 {
 643         u8 ret;
 644         u8 old;
 645
 646         old = READ_ONCE(zero_stats);
 647         if (unlikely(old)) {
 648                 ret = cmpxchg(&zero_stats, old, 0);
 649                 /* This ensures only one fellow resets the stat */
 650                 if (ret == old)
 651                         memset(&spinlock_stats, 0, sizeof(spinlock_stats));
 652         }
 653 }
 654
 655 static inline void add_stats(enum kvm_contention_stat var, u32 val)
 656 {
 657         check_zero();
 658         spinlock_stats.contention_stats[var] += val;
 659 }
 660
 661
 662 static inline u64 spin_time_start(void)
 663 {
 664         return sched_clock();
 665 }
 666
 667 static void __spin_time_accum(u64 delta, u32 *array)
 668 {
 669         unsigned index;
 670
 671         index = ilog2(delta);
 672         check_zero();
 673
 674         if (index < HISTO_BUCKETS)
 675                 array[index]++;
 676         else
 677                 array[HISTO_BUCKETS]++;
 678 }
 679
 680 static inline void spin_time_accum_blocked(u64 start)
 681 {
 682         u32 delta;
 683
 684         delta = sched_clock() - start;
 685         __spin_time_accum(delta, spinlock_stats.histo_spin_blocked);
 686         spinlock_stats.time_blocked += delta;
 687 }
 688
 689 static struct dentry *d_spin_debug;
 690 static struct dentry *d_kvm_debug;
 691
 692 static struct dentry *kvm_init_debugfs(void)
 693 {
 694         d_kvm_debug = debugfs_create_dir("kvm-guest", NULL);
 695         if (!d_kvm_debug)
 696                 printk(KERN_WARNING "Could not create 'kvm' debugfs directory\n");
 697
 698         return d_kvm_debug;
 699 }
 700
 701 static int __init kvm_spinlock_debugfs(void)
 702 {
 703         struct dentry *d_kvm;
 704
 705         d_kvm = kvm_init_debugfs();
 706         if (d_kvm == NULL)
 707                 return -ENOMEM;
 708
 709         d_spin_debug = debugfs_create_dir("spinlocks", d_kvm);
 710
 711         debugfs_create_u8("zero_stats", 0644, d_spin_debug, &zero_stats);
 712
 713         debugfs_create_u32("taken_slow", 0444, d_spin_debug,
 714                    &spinlock_stats.contention_stats[TAKEN_SLOW]);
 715         debugfs_create_u32("taken_slow_pickup", 0444, d_spin_debug,
 716                    &spinlock_stats.contention_stats[TAKEN_SLOW_PICKUP]);
 717
 718         debugfs_create_u32("released_slow", 0444, d_spin_debug,
 719                    &spinlock_stats.contention_stats[RELEASED_SLOW]);
 720         debugfs_create_u32("released_slow_kicked", 0444, d_spin_debug,
 721                    &spinlock_stats.contention_stats[RELEASED_SLOW_KICKED]);
 722
 723         debugfs_create_u64("time_blocked", 0444, d_spin_debug,
 724                            &spinlock_stats.time_blocked);
 725
 726         debugfs_create_u32_array("histo_blocked", 0444, d_spin_debug,
 727                      spinlock_stats.histo_spin_blocked, HISTO_BUCKETS + 1);
 728
 729         return 0;
 730 }
 731 fs_initcall(kvm_spinlock_debugfs);
 732 #else  /* !CONFIG_KVM_DEBUG_FS */
 733 static inline void add_stats(enum kvm_contention_stat var, u32 val)
 734 {
 735 }
 736
 737 static inline u64 spin_time_start(void)
 738 {
 739         return 0;
 740 }
 741
 742 static inline void spin_time_accum_blocked(u64 start)
 743 {
 744 }
 745 #endif  /* CONFIG_KVM_DEBUG_FS */
 746
 747 struct kvm_lock_waiting {
 748         struct arch_spinlock *lock;
 749         __ticket_t want;
 750 };
 751
 752 /* cpus 'waiting' on a spinlock to become available */
 753 static cpumask_t waiting_cpus;
 754
 755 /* Track spinlock on which a cpu is waiting */
 756 static DEFINE_PER_CPU(struct kvm_lock_waiting, klock_waiting);
 757
 758 __visible void kvm_lock_spinning(struct arch_spinlock *lock, __ticket_t want)
 759 {
 760         struct kvm_lock_waiting *w;
 761         int cpu;
 762         u64 start;
 763         unsigned long flags;
 764         __ticket_t head;
 765
 766         if (in_nmi())
 767                 return;
 768
 769         w = this_cpu_ptr(&klock_waiting);
 770         cpu = smp_processor_id();
 771         start = spin_time_start();
 772
 773         /*
 774          * Make sure an interrupt handler can't upset things in a
 775          * partially setup state.
 776          */
 777         local_irq_save(flags);
 778
 779         /*
 780          * The ordering protocol on this is that the "lock" pointer
 781          * may only be set non-NULL if the "want" ticket is correct.
 782          * If we're updating "want", we must first clear "lock".
 783          */
 784         w->lock = NULL;
 785         smp_wmb();
 786         w->want = want;
 787         smp_wmb();
 788         w->lock = lock;
 789
 790         add_stats(TAKEN_SLOW, 1);
 791
 792         /*
 793          * This uses set_bit, which is atomic but we should not rely on its
 794          * reordering gurantees. So barrier is needed after this call.
 795          */
 796         cpumask_set_cpu(cpu, &waiting_cpus);
 797
 798         barrier();
 799
 800         /*
 801          * Mark entry to slowpath before doing the pickup test to make
 802          * sure we don't deadlock with an unlocker.
 803          */
 804         __ticket_enter_slowpath(lock);
 805
 806         /* make sure enter_slowpath, which is atomic does not cross the read */
 807         smp_mb__after_atomic();
 808
 809         /*
 810          * check again make sure it didn't become free while
 811          * we weren't looking.
 812          */
 813         head = READ_ONCE(lock->tickets.head);
 814         if (__tickets_equal(head, want)) {
 815                 add_stats(TAKEN_SLOW_PICKUP, 1);
 816                 goto out;
 817         }
 818
 819         /*
 820          * halt until it's our turn and kicked. Note that we do safe halt
 821          * for irq enabled case to avoid hang when lock info is overwritten
 822          * in irq spinlock slowpath and no spurious interrupt occur to save us.
 823          */
 824         if (arch_irqs_disabled_flags(flags))
 825                 halt();
 826         else
 827                 safe_halt();
 828
 829 out:
 830         cpumask_clear_cpu(cpu, &waiting_cpus);
 831         w->lock = NULL;
 832         local_irq_restore(flags);
 833         spin_time_accum_blocked(start);
 834 }
 835 PV_CALLEE_SAVE_REGS_THUNK(kvm_lock_spinning);
 836
 837 /* Kick vcpu waiting on @lock->head to reach value @ticket */
 838 static void kvm_unlock_kick(struct arch_spinlock *lock, __ticket_t ticket)
 839 {
 840         int cpu;
 841
 842         add_stats(RELEASED_SLOW, 1);
 843         for_each_cpu(cpu, &waiting_cpus) {
 844                 const struct kvm_lock_waiting *w = &per_cpu(klock_waiting, cpu);
 845                 if (READ_ONCE(w->lock) == lock &&
 846                     READ_ONCE(w->want) == ticket) {
 847                         add_stats(RELEASED_SLOW_KICKED, 1);
 848                         kvm_kick_cpu(cpu);
 849                         break;
 850                 }
 851         }
 852 }
 853
 854 #endif /* !CONFIG_QUEUED_SPINLOCKS */
 855
 856 /*
 857  * Setup pv_lock_ops to exploit KVM_FEATURE_PV_UNHALT if present.
 858  */
 859 void __init kvm_spinlock_init(void)
 860 {
 861         if (!kvm_para_available())
 862                 return;
 863         /* Does host kernel support KVM_FEATURE_PV_UNHALT? */
 864         if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
 865                 return;
 866
 867 #ifdef CONFIG_QUEUED_SPINLOCKS
 868         __pv_init_lock_hash();
 869         pv_lock_ops.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
 870         pv_lock_ops.queued_spin_unlock = PV_CALLEE_SAVE(__pv_queued_spin_unlock);
 871         pv_lock_ops.wait = kvm_wait;
 872         pv_lock_ops.kick = kvm_kick_cpu;
 873 #else /* !CONFIG_QUEUED_SPINLOCKS */
 874         pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(kvm_lock_spinning);
 875         pv_lock_ops.unlock_kick = kvm_unlock_kick;
 876 #endif
 877 }
 878
 879 static __init int kvm_spinlock_init_jump(void)
 880 {
 881         if (!kvm_para_available())
 882                 return 0;
 883         if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
 884                 return 0;
 885
 886         static_key_slow_inc(&paravirt_ticketlocks_enabled);
 887         printk(KERN_INFO "KVM setup paravirtual spinlock\n");
 888
 889         return 0;
 890 }
 891 early_initcall(kvm_spinlock_init_jump);
 892
 893 #endif  /* CONFIG_PARAVIRT_SPINLOCKS */