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 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         DECLARE_SWAITQUEUE(wait);
 126
 127         rcu_irq_enter();
 128
 129         raw_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                 raw_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_swait_queue_head(&n.wq);
 145         hlist_add_head(&n.link, &b->list);
 146         raw_spin_unlock(&b->lock);
 147
 148         for (;;) {
 149                 if (!n.halted)
 150                         prepare_to_swait(&n.wq, &wait, TASK_UNINTERRUPTIBLE);
 151                 if (hlist_unhashed(&n.link))
 152                         break;
 153
 154                 if (!n.halted) {
 155                         local_irq_enable();
 156                         schedule();
 157                         local_irq_disable();
 158                 } else {
 159                         /*
 160                          * We cannot reschedule. So halt.
 161                          */
 162                         rcu_irq_exit();
 163                         native_safe_halt();
 164                         local_irq_disable();
 165                         rcu_irq_enter();
 166                 }
 167         }
 168         if (!n.halted)
 169                 finish_swait(&n.wq, &wait);
 170
 171         rcu_irq_exit();
 172         return;
 173 }
 174 EXPORT_SYMBOL_GPL(kvm_async_pf_task_wait);
 175
 176 static void apf_task_wake_one(struct kvm_task_sleep_node *n)
 177 {
 178         hlist_del_init(&n->link);
 179         if (n->halted)
 180                 smp_send_reschedule(n->cpu);
 181         else if (swait_active(&n->wq))
 182                 swake_up(&n->wq);
 183 }
 184
 185 static void apf_task_wake_all(void)
 186 {
 187         int i;
 188
 189         for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++) {
 190                 struct hlist_node *p, *next;
 191                 struct kvm_task_sleep_head *b = &async_pf_sleepers[i];
 192                 raw_spin_lock(&b->lock);
 193                 hlist_for_each_safe(p, next, &b->list) {
 194                         struct kvm_task_sleep_node *n =
 195                                 hlist_entry(p, typeof(*n), link);
 196                         if (n->cpu == smp_processor_id())
 197                                 apf_task_wake_one(n);
 198                 }
 199                 raw_spin_unlock(&b->lock);
 200         }
 201 }
 202
 203 void kvm_async_pf_task_wake(u32 token)
 204 {
 205         u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS);
 206         struct kvm_task_sleep_head *b = &async_pf_sleepers[key];
 207         struct kvm_task_sleep_node *n;
 208
 209         if (token == ~0) {
 210                 apf_task_wake_all();
 211                 return;
 212         }
 213
 214 again:
 215         raw_spin_lock(&b->lock);
 216         n = _find_apf_task(b, token);
 217         if (!n) {
 218                 /*
 219                  * async PF was not yet handled.
 220                  * Add dummy entry for the token.
 221                  */
 222                 n = kzalloc(sizeof(*n), GFP_ATOMIC);
 223                 if (!n) {
 224                         /*
 225                          * Allocation failed! Busy wait while other cpu
 226                          * handles async PF.
 227                          */
 228                         raw_spin_unlock(&b->lock);
 229                         cpu_relax();
 230                         goto again;
 231                 }
 232                 n->token = token;
 233                 n->cpu = smp_processor_id();
 234                 init_swait_queue_head(&n->wq);
 235                 hlist_add_head(&n->link, &b->list);
 236         } else
 237                 apf_task_wake_one(n);
 238         raw_spin_unlock(&b->lock);
 239         return;
 240 }
 241 EXPORT_SYMBOL_GPL(kvm_async_pf_task_wake);
 242
 243 u32 kvm_read_and_reset_pf_reason(void)
 244 {
 245         u32 reason = 0;
 246
 247         if (__this_cpu_read(apf_reason.enabled)) {
 248                 reason = __this_cpu_read(apf_reason.reason);
 249                 __this_cpu_write(apf_reason.reason, 0);
 250         }
 251
 252         return reason;
 253 }
 254 EXPORT_SYMBOL_GPL(kvm_read_and_reset_pf_reason);
 255 NOKPROBE_SYMBOL(kvm_read_and_reset_pf_reason);
 256
 257 dotraplinkage void
 258 do_async_page_fault(struct pt_regs *regs, unsigned long error_code)
 259 {
 260         enum ctx_state prev_state;
 261
 262         switch (kvm_read_and_reset_pf_reason()) {
 263         default:
 264                 trace_do_page_fault(regs, error_code);
 265                 break;
 266         case KVM_PV_REASON_PAGE_NOT_PRESENT:
 267                 /* page is swapped out by the host. */
 268                 prev_state = exception_enter();
 269                 kvm_async_pf_task_wait((u32)read_cr2());
 270                 exception_exit(prev_state);
 271                 break;
 272         case KVM_PV_REASON_PAGE_READY:
 273                 rcu_irq_enter();
 274                 kvm_async_pf_task_wake((u32)read_cr2());
 275                 rcu_irq_exit();
 276                 break;
 277         }
 278 }
 279 NOKPROBE_SYMBOL(do_async_page_fault);
 280
 281 static void __init paravirt_ops_setup(void)
 282 {
 283         pv_info.name = "KVM";
 284
 285         if (kvm_para_has_feature(KVM_FEATURE_NOP_IO_DELAY))
 286                 pv_cpu_ops.io_delay = kvm_io_delay;
 287
 288 #ifdef CONFIG_X86_IO_APIC
 289         no_timer_check = 1;
 290 #endif
 291 }
 292
 293 static void kvm_register_steal_time(void)
 294 {
 295         int cpu = smp_processor_id();
 296         struct kvm_steal_time *st = &per_cpu(steal_time, cpu);
 297
 298         if (!has_steal_clock)
 299                 return;
 300
 301         wrmsrl(MSR_KVM_STEAL_TIME, (slow_virt_to_phys(st) | KVM_MSR_ENABLED));
 302         pr_info("kvm-stealtime: cpu %d, msr %llx\n",
 303                 cpu, (unsigned long long) slow_virt_to_phys(st));
 304 }
 305
 306 static DEFINE_PER_CPU(unsigned long, kvm_apic_eoi) = KVM_PV_EOI_DISABLED;
 307
 308 static notrace void kvm_guest_apic_eoi_write(u32 reg, u32 val)
 309 {
 310         /**
 311          * This relies on __test_and_clear_bit to modify the memory
 312          * in a way that is atomic with respect to the local CPU.
 313          * The hypervisor only accesses this memory from the local CPU so
 314          * there's no need for lock or memory barriers.
 315          * An optimization barrier is implied in apic write.
 316          */
 317         if (__test_and_clear_bit(KVM_PV_EOI_BIT, this_cpu_ptr(&kvm_apic_eoi)))
 318                 return;
 319         apic->native_eoi_write(APIC_EOI, APIC_EOI_ACK);
 320 }
 321
 322 static void kvm_guest_cpu_init(void)
 323 {
 324         if (!kvm_para_available())
 325                 return;
 326
 327         if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF) && kvmapf) {
 328                 u64 pa = slow_virt_to_phys(this_cpu_ptr(&apf_reason));
 329
 330 #ifdef CONFIG_PREEMPT
 331                 pa |= KVM_ASYNC_PF_SEND_ALWAYS;
 332 #endif
 333                 wrmsrl(MSR_KVM_ASYNC_PF_EN, pa | KVM_ASYNC_PF_ENABLED);
 334                 __this_cpu_write(apf_reason.enabled, 1);
 335                 printk(KERN_INFO"KVM setup async PF for cpu %d\n",
 336                        smp_processor_id());
 337         }
 338
 339         if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) {
 340                 unsigned long pa;
 341                 /* Size alignment is implied but just to make it explicit. */
 342                 BUILD_BUG_ON(__alignof__(kvm_apic_eoi) < 4);
 343                 __this_cpu_write(kvm_apic_eoi, 0);
 344                 pa = slow_virt_to_phys(this_cpu_ptr(&kvm_apic_eoi))
 345                         | KVM_MSR_ENABLED;
 346                 wrmsrl(MSR_KVM_PV_EOI_EN, pa);
 347         }
 348
 349         if (has_steal_clock)
 350                 kvm_register_steal_time();
 351 }
 352
 353 static void kvm_pv_disable_apf(void)
 354 {
 355         if (!__this_cpu_read(apf_reason.enabled))
 356                 return;
 357
 358         wrmsrl(MSR_KVM_ASYNC_PF_EN, 0);
 359         __this_cpu_write(apf_reason.enabled, 0);
 360
 361         printk(KERN_INFO"Unregister pv shared memory for cpu %d\n",
 362                smp_processor_id());
 363 }
 364
 365 static void kvm_pv_guest_cpu_reboot(void *unused)
 366 {
 367         /*
 368          * We disable PV EOI before we load a new kernel by kexec,
 369          * since MSR_KVM_PV_EOI_EN stores a pointer into old kernel's memory.
 370          * New kernel can re-enable when it boots.
 371          */
 372         if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
 373                 wrmsrl(MSR_KVM_PV_EOI_EN, 0);
 374         kvm_pv_disable_apf();
 375         kvm_disable_steal_time();
 376 }
 377
 378 static int kvm_pv_reboot_notify(struct notifier_block *nb,
 379                                 unsigned long code, void *unused)
 380 {
 381         if (code == SYS_RESTART)
 382                 on_each_cpu(kvm_pv_guest_cpu_reboot, NULL, 1);
 383         return NOTIFY_DONE;
 384 }
 385
 386 static struct notifier_block kvm_pv_reboot_nb = {
 387         .notifier_call = kvm_pv_reboot_notify,
 388 };
 389
 390 static u64 kvm_steal_clock(int cpu)
 391 {
 392         u64 steal;
 393         struct kvm_steal_time *src;
 394         int version;
 395
 396         src = &per_cpu(steal_time, cpu);
 397         do {
 398                 version = src->version;
 399                 virt_rmb();
 400                 steal = src->steal;
 401                 virt_rmb();
 402         } while ((version & 1) || (version != src->version));
 403
 404         return steal;
 405 }
 406
 407 void kvm_disable_steal_time(void)
 408 {
 409         if (!has_steal_clock)
 410                 return;
 411
 412         wrmsr(MSR_KVM_STEAL_TIME, 0, 0);
 413 }
 414
 415 #ifdef CONFIG_SMP
 416 static void __init kvm_smp_prepare_boot_cpu(void)
 417 {
 418         kvm_guest_cpu_init();
 419         native_smp_prepare_boot_cpu();
 420         kvm_spinlock_init();
 421 }
 422
 423 static void kvm_guest_cpu_offline(void)
 424 {
 425         kvm_disable_steal_time();
 426         if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
 427                 wrmsrl(MSR_KVM_PV_EOI_EN, 0);
 428         kvm_pv_disable_apf();
 429         apf_task_wake_all();
 430 }
 431
 432 static int kvm_cpu_online(unsigned int cpu)
 433 {
 434         local_irq_disable();
 435         kvm_guest_cpu_init();
 436         local_irq_enable();
 437         return 0;
 438 }
 439
 440 static int kvm_cpu_down_prepare(unsigned int cpu)
 441 {
 442         local_irq_disable();
 443         kvm_guest_cpu_offline();
 444         local_irq_enable();
 445         return 0;
 446 }
 447 #endif
 448
 449 static void __init kvm_apf_trap_init(void)
 450 {
 451         set_intr_gate(14, async_page_fault);
 452 }
 453
 454 void __init kvm_guest_init(void)
 455 {
 456         int i;
 457
 458         if (!kvm_para_available())
 459                 return;
 460
 461         paravirt_ops_setup();
 462         register_reboot_notifier(&kvm_pv_reboot_nb);
 463         for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++)
 464                 raw_spin_lock_init(&async_pf_sleepers[i].lock);
 465         if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF))
 466                 x86_init.irqs.trap_init = kvm_apf_trap_init;
 467
 468         if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
 469                 has_steal_clock = 1;
 470                 pv_time_ops.steal_clock = kvm_steal_clock;
 471         }
 472
 473         if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
 474                 apic_set_eoi_write(kvm_guest_apic_eoi_write);
 475
 476         if (kvmclock_vsyscall)
 477                 kvm_setup_vsyscall_timeinfo();
 478
 479 #ifdef CONFIG_SMP
 480         smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
 481         if (cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "x86/kvm:online",
 482                                       kvm_cpu_online, kvm_cpu_down_prepare) < 0)
 483                 pr_err("kvm_guest: Failed to install cpu hotplug callbacks\n");
 484 #else
 485         kvm_guest_cpu_init();
 486 #endif
 487
 488         /*
 489          * Hard lockup detection is enabled by default. Disable it, as guests
 490          * can get false positives too easily, for example if the host is
 491          * overcommitted.
 492          */
 493         hardlockup_detector_disable();
 494 }
 495
 496 static noinline uint32_t __kvm_cpuid_base(void)
 497 {
 498         if (boot_cpu_data.cpuid_level < 0)
 499                 return 0;       /* So we don't blow up on old processors */
 500
 501         if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
 502                 return hypervisor_cpuid_base("KVMKVMKVM\0\0\0", 0);
 503
 504         return 0;
 505 }
 506
 507 static inline uint32_t kvm_cpuid_base(void)
 508 {
 509         static int kvm_cpuid_base = -1;
 510
 511         if (kvm_cpuid_base == -1)
 512                 kvm_cpuid_base = __kvm_cpuid_base();
 513
 514         return kvm_cpuid_base;
 515 }
 516
 517 bool kvm_para_available(void)
 518 {
 519         return kvm_cpuid_base() != 0;
 520 }
 521 EXPORT_SYMBOL_GPL(kvm_para_available);
 522
 523 unsigned int kvm_arch_para_features(void)
 524 {
 525         return cpuid_eax(kvm_cpuid_base() | KVM_CPUID_FEATURES);
 526 }
 527
 528 static uint32_t __init kvm_detect(void)
 529 {
 530         return kvm_cpuid_base();
 531 }
 532
 533 const struct hypervisor_x86 x86_hyper_kvm __refconst = {
 534         .name                   = "KVM",
 535         .detect                 = kvm_detect,
 536         .x2apic_available       = kvm_para_available,
 537 };
 538 EXPORT_SYMBOL_GPL(x86_hyper_kvm);
 539
 540 static __init int activate_jump_labels(void)
 541 {
 542         if (has_steal_clock) {
 543                 static_key_slow_inc(&paravirt_steal_enabled);
 544                 if (steal_acc)
 545                         static_key_slow_inc(&paravirt_steal_rq_enabled);
 546         }
 547
 548         return 0;
 549 }
 550 arch_initcall(activate_jump_labels);
 551
 552 #ifdef CONFIG_PARAVIRT_SPINLOCKS
 553
 554 /* Kick a cpu by its apicid. Used to wake up a halted vcpu */
 555 static void kvm_kick_cpu(int cpu)
 556 {
 557         int apicid;
 558         unsigned long flags = 0;
 559
 560         apicid = per_cpu(x86_cpu_to_apicid, cpu);
 561         kvm_hypercall2(KVM_HC_KICK_CPU, flags, apicid);
 562 }
 563
 564 #include <asm/qspinlock.h>
 565
 566 static void kvm_wait(u8 *ptr, u8 val)
 567 {
 568         unsigned long flags;
 569
 570         if (in_nmi())
 571                 return;
 572
 573         local_irq_save(flags);
 574
 575         if (READ_ONCE(*ptr) != val)
 576                 goto out;
 577
 578         /*
 579          * halt until it's our turn and kicked. Note that we do safe halt
 580          * for irq enabled case to avoid hang when lock info is overwritten
 581          * in irq spinlock slowpath and no spurious interrupt occur to save us.
 582          */
 583         if (arch_irqs_disabled_flags(flags))
 584                 halt();
 585         else
 586                 safe_halt();
 587
 588 out:
 589         local_irq_restore(flags);
 590 }
 591
 592 #ifdef CONFIG_X86_32
 593 __visible bool __kvm_vcpu_is_preempted(long cpu)
 594 {
 595         struct kvm_steal_time *src = &per_cpu(steal_time, cpu);
 596
 597         return !!src->preempted;
 598 }
 599 PV_CALLEE_SAVE_REGS_THUNK(__kvm_vcpu_is_preempted);
 600
 601 #else
 602
 603 #include <asm/asm-offsets.h>
 604
 605 extern bool __raw_callee_save___kvm_vcpu_is_preempted(long);
 606
 607 /*
 608  * Hand-optimize version for x86-64 to avoid 8 64-bit register saving and
 609  * restoring to/from the stack.
 610  */
 611 asm(
 612 ".pushsection .text;"
 613 ".global __raw_callee_save___kvm_vcpu_is_preempted;"
 614 ".type __raw_callee_save___kvm_vcpu_is_preempted, @function;"
 615 "__raw_callee_save___kvm_vcpu_is_preempted:"
 616 "movq   __per_cpu_offset(,%rdi,8), %rax;"
 617 "cmpb   $0, " __stringify(KVM_STEAL_TIME_preempted) "+steal_time(%rax);"
 618 "setne  %al;"
 619 "ret;"
 620 ".popsection");
 621
 622 #endif
 623
 624 /*
 625  * Setup pv_lock_ops to exploit KVM_FEATURE_PV_UNHALT if present.
 626  */
 627 void __init kvm_spinlock_init(void)
 628 {
 629         if (!kvm_para_available())
 630                 return;
 631         /* Does host kernel support KVM_FEATURE_PV_UNHALT? */
 632         if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
 633                 return;
 634
 635         __pv_init_lock_hash();
 636         pv_lock_ops.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
 637         pv_lock_ops.queued_spin_unlock = PV_CALLEE_SAVE(__pv_queued_spin_unlock);
 638         pv_lock_ops.wait = kvm_wait;
 639         pv_lock_ops.kick = kvm_kick_cpu;
 640
 641         if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
 642                 pv_lock_ops.vcpu_is_preempted =
 643                         PV_CALLEE_SAVE(__kvm_vcpu_is_preempted);
 644         }
 645 }
 646
 647 #endif  /* CONFIG_PARAVIRT_SPINLOCKS */