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/module.h>
  24 #include <linux/kernel.h>
  25 #include <linux/kvm_para.h>
  26 #include <linux/cpu.h>
  27 #include <linux/mm.h>
  28 #include <linux/highmem.h>
  29 #include <linux/hardirq.h>
  30 #include <linux/notifier.h>
  31 #include <linux/reboot.h>
  32 #include <linux/hash.h>
  33 #include <linux/sched.h>
  34 #include <linux/slab.h>
  35 #include <linux/kprobes.h>
  36 #include <asm/timer.h>
  37 #include <asm/cpu.h>
  38 #include <asm/traps.h>
  39 #include <asm/desc.h>
  40 #include <asm/tlbflush.h>
  41 #include <asm/idle.h>
  42 #include <asm/apic.h>
  43 #include <asm/apicdef.h>
  44 #include <asm/hypervisor.h>
  45 #include <asm/kvm_guest.h>
  46
  47 static int kvmapf = 1;
  48
  49 static int parse_no_kvmapf(char *arg)
  50 {
  51         kvmapf = 0;
  52         return 0;
  53 }
  54
  55 early_param("no-kvmapf", parse_no_kvmapf);
  56
  57 static int steal_acc = 1;
  58 static int parse_no_stealacc(char *arg)
  59 {
  60         steal_acc = 0;
  61         return 0;
  62 }
  63
  64 early_param("no-steal-acc", parse_no_stealacc);
  65
  66 static int kvmclock_vsyscall = 1;
  67 static int parse_no_kvmclock_vsyscall(char *arg)
  68 {
  69         kvmclock_vsyscall = 0;
  70         return 0;
  71 }
  72
  73 early_param("no-kvmclock-vsyscall", parse_no_kvmclock_vsyscall);
  74
  75 static DEFINE_PER_CPU(struct kvm_vcpu_pv_apf_data, apf_reason) __aligned(64);
  76 static DEFINE_PER_CPU(struct kvm_steal_time, steal_time) __aligned(64);
  77 static int has_steal_clock = 0;
  78
  79 /*
  80  * No need for any "IO delay" on KVM
  81  */
  82 static void kvm_io_delay(void)
  83 {
  84 }
  85
  86 #define KVM_TASK_SLEEP_HASHBITS 8
  87 #define KVM_TASK_SLEEP_HASHSIZE (1<<KVM_TASK_SLEEP_HASHBITS)
  88
  89 struct kvm_task_sleep_node {
  90         struct hlist_node link;
  91         wait_queue_head_t wq;
  92         u32 token;
  93         int cpu;
  94         bool halted;
  95 };
  96
  97 static struct kvm_task_sleep_head {
  98         spinlock_t lock;
  99         struct hlist_head list;
 100 } async_pf_sleepers[KVM_TASK_SLEEP_HASHSIZE];
 101
 102 static struct kvm_task_sleep_node *_find_apf_task(struct kvm_task_sleep_head *b,
 103                                                   u32 token)
 104 {
 105         struct hlist_node *p;
 106
 107         hlist_for_each(p, &b->list) {
 108                 struct kvm_task_sleep_node *n =
 109                         hlist_entry(p, typeof(*n), link);
 110                 if (n->token == token)
 111                         return n;
 112         }
 113
 114         return NULL;
 115 }
 116
 117 void kvm_async_pf_task_wait(u32 token)
 118 {
 119         u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS);
 120         struct kvm_task_sleep_head *b = &async_pf_sleepers[key];
 121         struct kvm_task_sleep_node n, *e;
 122         DEFINE_WAIT(wait);
 123
 124         spin_lock(&b->lock);
 125         e = _find_apf_task(b, token);
 126         if (e) {
 127                 /* dummy entry exist -> wake up was delivered ahead of PF */
 128                 hlist_del(&e->link);
 129                 kfree(e);
 130                 spin_unlock(&b->lock);
 131                 return;
 132         }
 133
 134         n.token = token;
 135         n.cpu = smp_processor_id();
 136         n.halted = is_idle_task(current) || preempt_count() > 1;
 137         init_waitqueue_head(&n.wq);
 138         hlist_add_head(&n.link, &b->list);
 139         spin_unlock(&b->lock);
 140
 141         for (;;) {
 142                 if (!n.halted)
 143                         prepare_to_wait(&n.wq, &wait, TASK_UNINTERRUPTIBLE);
 144                 if (hlist_unhashed(&n.link))
 145                         break;
 146
 147                 if (!n.halted) {
 148                         local_irq_enable();
 149                         schedule();
 150                         local_irq_disable();
 151                 } else {
 152                         /*
 153                          * We cannot reschedule. So halt.
 154                          */
 155                         native_safe_halt();
 156                         local_irq_disable();
 157                 }
 158         }
 159         if (!n.halted)
 160                 finish_wait(&n.wq, &wait);
 161
 162         return;
 163 }
 164 EXPORT_SYMBOL_GPL(kvm_async_pf_task_wait);
 165
 166 static void apf_task_wake_one(struct kvm_task_sleep_node *n)
 167 {
 168         hlist_del_init(&n->link);
 169         if (n->halted)
 170                 smp_send_reschedule(n->cpu);
 171         else if (waitqueue_active(&n->wq))
 172                 wake_up(&n->wq);
 173 }
 174
 175 static void apf_task_wake_all(void)
 176 {
 177         int i;
 178
 179         for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++) {
 180                 struct hlist_node *p, *next;
 181                 struct kvm_task_sleep_head *b = &async_pf_sleepers[i];
 182                 spin_lock(&b->lock);
 183                 hlist_for_each_safe(p, next, &b->list) {
 184                         struct kvm_task_sleep_node *n =
 185                                 hlist_entry(p, typeof(*n), link);
 186                         if (n->cpu == smp_processor_id())
 187                                 apf_task_wake_one(n);
 188                 }
 189                 spin_unlock(&b->lock);
 190         }
 191 }
 192
 193 void kvm_async_pf_task_wake(u32 token)
 194 {
 195         u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS);
 196         struct kvm_task_sleep_head *b = &async_pf_sleepers[key];
 197         struct kvm_task_sleep_node *n;
 198
 199         if (token == ~0) {
 200                 apf_task_wake_all();
 201                 return;
 202         }
 203
 204 again:
 205         spin_lock(&b->lock);
 206         n = _find_apf_task(b, token);
 207         if (!n) {
 208                 /*
 209                  * async PF was not yet handled.
 210                  * Add dummy entry for the token.
 211                  */
 212                 n = kzalloc(sizeof(*n), GFP_ATOMIC);
 213                 if (!n) {
 214                         /*
 215                          * Allocation failed! Busy wait while other cpu
 216                          * handles async PF.
 217                          */
 218                         spin_unlock(&b->lock);
 219                         cpu_relax();
 220                         goto again;
 221                 }
 222                 n->token = token;
 223                 n->cpu = smp_processor_id();
 224                 init_waitqueue_head(&n->wq);
 225                 hlist_add_head(&n->link, &b->list);
 226         } else
 227                 apf_task_wake_one(n);
 228         spin_unlock(&b->lock);
 229         return;
 230 }
 231 EXPORT_SYMBOL_GPL(kvm_async_pf_task_wake);
 232
 233 u32 kvm_read_and_reset_pf_reason(void)
 234 {
 235         u32 reason = 0;
 236
 237         if (__get_cpu_var(apf_reason).enabled) {
 238                 reason = __get_cpu_var(apf_reason).reason;
 239                 __get_cpu_var(apf_reason).reason = 0;
 240         }
 241
 242         return reason;
 243 }
 244 EXPORT_SYMBOL_GPL(kvm_read_and_reset_pf_reason);
 245
 246 dotraplinkage void __kprobes
 247 do_async_page_fault(struct pt_regs *regs, unsigned long error_code)
 248 {
 249         switch (kvm_read_and_reset_pf_reason()) {
 250         default:
 251                 do_page_fault(regs, error_code);
 252                 break;
 253         case KVM_PV_REASON_PAGE_NOT_PRESENT:
 254                 /* page is swapped out by the host. */
 255                 rcu_irq_enter();
 256                 exit_idle();
 257                 kvm_async_pf_task_wait((u32)read_cr2());
 258                 rcu_irq_exit();
 259                 break;
 260         case KVM_PV_REASON_PAGE_READY:
 261                 rcu_irq_enter();
 262                 exit_idle();
 263                 kvm_async_pf_task_wake((u32)read_cr2());
 264                 rcu_irq_exit();
 265                 break;
 266         }
 267 }
 268
 269 static void __init paravirt_ops_setup(void)
 270 {
 271         pv_info.name = "KVM";
 272         pv_info.paravirt_enabled = 1;
 273
 274         if (kvm_para_has_feature(KVM_FEATURE_NOP_IO_DELAY))
 275                 pv_cpu_ops.io_delay = kvm_io_delay;
 276
 277 #ifdef CONFIG_X86_IO_APIC
 278         no_timer_check = 1;
 279 #endif
 280 }
 281
 282 static void kvm_register_steal_time(void)
 283 {
 284         int cpu = smp_processor_id();
 285         struct kvm_steal_time *st = &per_cpu(steal_time, cpu);
 286
 287         if (!has_steal_clock)
 288                 return;
 289
 290         memset(st, 0, sizeof(*st));
 291
 292         wrmsrl(MSR_KVM_STEAL_TIME, (__pa(st) | KVM_MSR_ENABLED));
 293         printk(KERN_INFO "kvm-stealtime: cpu %d, msr %lx\n",
 294                 cpu, __pa(st));
 295 }
 296
 297 static DEFINE_PER_CPU(unsigned long, kvm_apic_eoi) = KVM_PV_EOI_DISABLED;
 298
 299 static void kvm_guest_apic_eoi_write(u32 reg, u32 val)
 300 {
 301         /**
 302          * This relies on __test_and_clear_bit to modify the memory
 303          * in a way that is atomic with respect to the local CPU.
 304          * The hypervisor only accesses this memory from the local CPU so
 305          * there's no need for lock or memory barriers.
 306          * An optimization barrier is implied in apic write.
 307          */
 308         if (__test_and_clear_bit(KVM_PV_EOI_BIT, &__get_cpu_var(kvm_apic_eoi)))
 309                 return;
 310         apic_write(APIC_EOI, APIC_EOI_ACK);
 311 }
 312
 313 void __cpuinit kvm_guest_cpu_init(void)
 314 {
 315         if (!kvm_para_available())
 316                 return;
 317
 318         if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF) && kvmapf) {
 319                 u64 pa = __pa(&__get_cpu_var(apf_reason));
 320
 321 #ifdef CONFIG_PREEMPT
 322                 pa |= KVM_ASYNC_PF_SEND_ALWAYS;
 323 #endif
 324                 wrmsrl(MSR_KVM_ASYNC_PF_EN, pa | KVM_ASYNC_PF_ENABLED);
 325                 __get_cpu_var(apf_reason).enabled = 1;
 326                 printk(KERN_INFO"KVM setup async PF for cpu %d\n",
 327                        smp_processor_id());
 328         }
 329
 330         if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) {
 331                 unsigned long pa;
 332                 /* Size alignment is implied but just to make it explicit. */
 333                 BUILD_BUG_ON(__alignof__(kvm_apic_eoi) < 4);
 334                 __get_cpu_var(kvm_apic_eoi) = 0;
 335                 pa = __pa(&__get_cpu_var(kvm_apic_eoi)) | KVM_MSR_ENABLED;
 336                 wrmsrl(MSR_KVM_PV_EOI_EN, pa);
 337         }
 338
 339         if (has_steal_clock)
 340                 kvm_register_steal_time();
 341 }
 342
 343 static void kvm_pv_disable_apf(void)
 344 {
 345         if (!__get_cpu_var(apf_reason).enabled)
 346                 return;
 347
 348         wrmsrl(MSR_KVM_ASYNC_PF_EN, 0);
 349         __get_cpu_var(apf_reason).enabled = 0;
 350
 351         printk(KERN_INFO"Unregister pv shared memory for cpu %d\n",
 352                smp_processor_id());
 353 }
 354
 355 static void kvm_pv_guest_cpu_reboot(void *unused)
 356 {
 357         /*
 358          * We disable PV EOI before we load a new kernel by kexec,
 359          * since MSR_KVM_PV_EOI_EN stores a pointer into old kernel's memory.
 360          * New kernel can re-enable when it boots.
 361          */
 362         if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
 363                 wrmsrl(MSR_KVM_PV_EOI_EN, 0);
 364         kvm_pv_disable_apf();
 365         kvm_disable_steal_time();
 366 }
 367
 368 static int kvm_pv_reboot_notify(struct notifier_block *nb,
 369                                 unsigned long code, void *unused)
 370 {
 371         if (code == SYS_RESTART)
 372                 on_each_cpu(kvm_pv_guest_cpu_reboot, NULL, 1);
 373         return NOTIFY_DONE;
 374 }
 375
 376 static struct notifier_block kvm_pv_reboot_nb = {
 377         .notifier_call = kvm_pv_reboot_notify,
 378 };
 379
 380 static u64 kvm_steal_clock(int cpu)
 381 {
 382         u64 steal;
 383         struct kvm_steal_time *src;
 384         int version;
 385
 386         src = &per_cpu(steal_time, cpu);
 387         do {
 388                 version = src->version;
 389                 rmb();
 390                 steal = src->steal;
 391                 rmb();
 392         } while ((version & 1) || (version != src->version));
 393
 394         return steal;
 395 }
 396
 397 void kvm_disable_steal_time(void)
 398 {
 399         if (!has_steal_clock)
 400                 return;
 401
 402         wrmsr(MSR_KVM_STEAL_TIME, 0, 0);
 403 }
 404
 405 #ifdef CONFIG_SMP
 406 static void __init kvm_smp_prepare_boot_cpu(void)
 407 {
 408         WARN_ON(kvm_register_clock("primary cpu clock"));
 409         kvm_guest_cpu_init();
 410         native_smp_prepare_boot_cpu();
 411 }
 412
 413 static void __cpuinit kvm_guest_cpu_online(void *dummy)
 414 {
 415         kvm_guest_cpu_init();
 416 }
 417
 418 static void kvm_guest_cpu_offline(void *dummy)
 419 {
 420         kvm_disable_steal_time();
 421         if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
 422                 wrmsrl(MSR_KVM_PV_EOI_EN, 0);
 423         kvm_pv_disable_apf();
 424         apf_task_wake_all();
 425 }
 426
 427 static int __cpuinit kvm_cpu_notify(struct notifier_block *self,
 428                                     unsigned long action, void *hcpu)
 429 {
 430         int cpu = (unsigned long)hcpu;
 431         switch (action) {
 432         case CPU_ONLINE:
 433         case CPU_DOWN_FAILED:
 434         case CPU_ONLINE_FROZEN:
 435                 smp_call_function_single(cpu, kvm_guest_cpu_online, NULL, 0);
 436                 break;
 437         case CPU_DOWN_PREPARE:
 438         case CPU_DOWN_PREPARE_FROZEN:
 439                 smp_call_function_single(cpu, kvm_guest_cpu_offline, NULL, 1);
 440                 break;
 441         default:
 442                 break;
 443         }
 444         return NOTIFY_OK;
 445 }
 446
 447 static struct notifier_block __cpuinitdata kvm_cpu_notifier = {
 448         .notifier_call  = kvm_cpu_notify,
 449 };
 450 #endif
 451
 452 static void __init kvm_apf_trap_init(void)
 453 {
 454         set_intr_gate(14, &async_page_fault);
 455 }
 456
 457 void __init kvm_guest_init(void)
 458 {
 459         int i;
 460
 461         if (!kvm_para_available())
 462                 return;
 463
 464         paravirt_ops_setup();
 465         register_reboot_notifier(&kvm_pv_reboot_nb);
 466         for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++)
 467                 spin_lock_init(&async_pf_sleepers[i].lock);
 468         if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF))
 469                 x86_init.irqs.trap_init = kvm_apf_trap_init;
 470
 471         if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
 472                 has_steal_clock = 1;
 473                 pv_time_ops.steal_clock = kvm_steal_clock;
 474         }
 475
 476         if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
 477                 apic_set_eoi_write(kvm_guest_apic_eoi_write);
 478
 479         if (kvmclock_vsyscall)
 480                 kvm_setup_vsyscall_timeinfo();
 481
 482 #ifdef CONFIG_SMP
 483         smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
 484         register_cpu_notifier(&kvm_cpu_notifier);
 485 #else
 486         kvm_guest_cpu_init();
 487 #endif
 488 }
 489
 490 static bool __init kvm_detect(void)
 491 {
 492         if (!kvm_para_available())
 493                 return false;
 494         return true;
 495 }
 496
 497 const struct hypervisor_x86 x86_hyper_kvm __refconst = {
 498         .name                   = "KVM",
 499         .detect                 = kvm_detect,
 500 };
 501 EXPORT_SYMBOL_GPL(x86_hyper_kvm);
 502
 503 static __init int activate_jump_labels(void)
 504 {
 505         if (has_steal_clock) {
 506                 static_key_slow_inc(&paravirt_steal_enabled);
 507                 if (steal_acc)
 508                         static_key_slow_inc(&paravirt_steal_rq_enabled);
 509         }
 510
 511         return 0;
 512 }
 513 arch_initcall(activate_jump_labels);