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         int cpu, idle;
 124
 125         cpu = get_cpu();
 126         idle = idle_cpu(cpu);
 127         put_cpu();
 128
 129         spin_lock(&b->lock);
 130         e = _find_apf_task(b, token);
 131         if (e) {
 132                 /* dummy entry exist -> wake up was delivered ahead of PF */
 133                 hlist_del(&e->link);
 134                 kfree(e);
 135                 spin_unlock(&b->lock);
 136                 return;
 137         }
 138
 139         n.token = token;
 140         n.cpu = smp_processor_id();
 141         n.halted = idle || preempt_count() > 1;
 142         init_waitqueue_head(&n.wq);
 143         hlist_add_head(&n.link, &b->list);
 144         spin_unlock(&b->lock);
 145
 146         for (;;) {
 147                 if (!n.halted)
 148                         prepare_to_wait(&n.wq, &wait, TASK_UNINTERRUPTIBLE);
 149                 if (hlist_unhashed(&n.link))
 150                         break;
 151
 152                 if (!n.halted) {
 153                         local_irq_enable();
 154                         schedule();
 155                         local_irq_disable();
 156                 } else {
 157                         /*
 158                          * We cannot reschedule. So halt.
 159                          */
 160                         native_safe_halt();
 161                         local_irq_disable();
 162                 }
 163         }
 164         if (!n.halted)
 165                 finish_wait(&n.wq, &wait);
 166
 167         return;
 168 }
 169 EXPORT_SYMBOL_GPL(kvm_async_pf_task_wait);
 170
 171 static void apf_task_wake_one(struct kvm_task_sleep_node *n)
 172 {
 173         hlist_del_init(&n->link);
 174         if (n->halted)
 175                 smp_send_reschedule(n->cpu);
 176         else if (waitqueue_active(&n->wq))
 177                 wake_up(&n->wq);
 178 }
 179
 180 static void apf_task_wake_all(void)
 181 {
 182         int i;
 183
 184         for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++) {
 185                 struct hlist_node *p, *next;
 186                 struct kvm_task_sleep_head *b = &async_pf_sleepers[i];
 187                 spin_lock(&b->lock);
 188                 hlist_for_each_safe(p, next, &b->list) {
 189                         struct kvm_task_sleep_node *n =
 190                                 hlist_entry(p, typeof(*n), link);
 191                         if (n->cpu == smp_processor_id())
 192                                 apf_task_wake_one(n);
 193                 }
 194                 spin_unlock(&b->lock);
 195         }
 196 }
 197
 198 void kvm_async_pf_task_wake(u32 token)
 199 {
 200         u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS);
 201         struct kvm_task_sleep_head *b = &async_pf_sleepers[key];
 202         struct kvm_task_sleep_node *n;
 203
 204         if (token == ~0) {
 205                 apf_task_wake_all();
 206                 return;
 207         }
 208
 209 again:
 210         spin_lock(&b->lock);
 211         n = _find_apf_task(b, token);
 212         if (!n) {
 213                 /*
 214                  * async PF was not yet handled.
 215                  * Add dummy entry for the token.
 216                  */
 217                 n = kzalloc(sizeof(*n), GFP_ATOMIC);
 218                 if (!n) {
 219                         /*
 220                          * Allocation failed! Busy wait while other cpu
 221                          * handles async PF.
 222                          */
 223                         spin_unlock(&b->lock);
 224                         cpu_relax();
 225                         goto again;
 226                 }
 227                 n->token = token;
 228                 n->cpu = smp_processor_id();
 229                 init_waitqueue_head(&n->wq);
 230                 hlist_add_head(&n->link, &b->list);
 231         } else
 232                 apf_task_wake_one(n);
 233         spin_unlock(&b->lock);
 234         return;
 235 }
 236 EXPORT_SYMBOL_GPL(kvm_async_pf_task_wake);
 237
 238 u32 kvm_read_and_reset_pf_reason(void)
 239 {
 240         u32 reason = 0;
 241
 242         if (__get_cpu_var(apf_reason).enabled) {
 243                 reason = __get_cpu_var(apf_reason).reason;
 244                 __get_cpu_var(apf_reason).reason = 0;
 245         }
 246
 247         return reason;
 248 }
 249 EXPORT_SYMBOL_GPL(kvm_read_and_reset_pf_reason);
 250
 251 dotraplinkage void __kprobes
 252 do_async_page_fault(struct pt_regs *regs, unsigned long error_code)
 253 {
 254         switch (kvm_read_and_reset_pf_reason()) {
 255         default:
 256                 do_page_fault(regs, error_code);
 257                 break;
 258         case KVM_PV_REASON_PAGE_NOT_PRESENT:
 259                 /* page is swapped out by the host. */
 260                 rcu_irq_enter();
 261                 exit_idle();
 262                 kvm_async_pf_task_wait((u32)read_cr2());
 263                 rcu_irq_exit();
 264                 break;
 265         case KVM_PV_REASON_PAGE_READY:
 266                 rcu_irq_enter();
 267                 exit_idle();
 268                 kvm_async_pf_task_wake((u32)read_cr2());
 269                 rcu_irq_exit();
 270                 break;
 271         }
 272 }
 273
 274 static void __init paravirt_ops_setup(void)
 275 {
 276         pv_info.name = "KVM";
 277         pv_info.paravirt_enabled = 1;
 278
 279         if (kvm_para_has_feature(KVM_FEATURE_NOP_IO_DELAY))
 280                 pv_cpu_ops.io_delay = kvm_io_delay;
 281
 282 #ifdef CONFIG_X86_IO_APIC
 283         no_timer_check = 1;
 284 #endif
 285 }
 286
 287 static void kvm_register_steal_time(void)
 288 {
 289         int cpu = smp_processor_id();
 290         struct kvm_steal_time *st = &per_cpu(steal_time, cpu);
 291
 292         if (!has_steal_clock)
 293                 return;
 294
 295         memset(st, 0, sizeof(*st));
 296
 297         wrmsrl(MSR_KVM_STEAL_TIME, (__pa(st) | KVM_MSR_ENABLED));
 298         printk(KERN_INFO "kvm-stealtime: cpu %d, msr %lx\n",
 299                 cpu, __pa(st));
 300 }
 301
 302 static DEFINE_PER_CPU(unsigned long, kvm_apic_eoi) = KVM_PV_EOI_DISABLED;
 303
 304 static void kvm_guest_apic_eoi_write(u32 reg, u32 val)
 305 {
 306         /**
 307          * This relies on __test_and_clear_bit to modify the memory
 308          * in a way that is atomic with respect to the local CPU.
 309          * The hypervisor only accesses this memory from the local CPU so
 310          * there's no need for lock or memory barriers.
 311          * An optimization barrier is implied in apic write.
 312          */
 313         if (__test_and_clear_bit(KVM_PV_EOI_BIT, &__get_cpu_var(kvm_apic_eoi)))
 314                 return;
 315         apic_write(APIC_EOI, APIC_EOI_ACK);
 316 }
 317
 318 void __cpuinit kvm_guest_cpu_init(void)
 319 {
 320         if (!kvm_para_available())
 321                 return;
 322
 323         if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF) && kvmapf) {
 324                 u64 pa = __pa(&__get_cpu_var(apf_reason));
 325
 326 #ifdef CONFIG_PREEMPT
 327                 pa |= KVM_ASYNC_PF_SEND_ALWAYS;
 328 #endif
 329                 wrmsrl(MSR_KVM_ASYNC_PF_EN, pa | KVM_ASYNC_PF_ENABLED);
 330                 __get_cpu_var(apf_reason).enabled = 1;
 331                 printk(KERN_INFO"KVM setup async PF for cpu %d\n",
 332                        smp_processor_id());
 333         }
 334
 335         if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) {
 336                 unsigned long pa;
 337                 /* Size alignment is implied but just to make it explicit. */
 338                 BUILD_BUG_ON(__alignof__(kvm_apic_eoi) < 4);
 339                 __get_cpu_var(kvm_apic_eoi) = 0;
 340                 pa = __pa(&__get_cpu_var(kvm_apic_eoi)) | KVM_MSR_ENABLED;
 341                 wrmsrl(MSR_KVM_PV_EOI_EN, pa);
 342         }
 343
 344         if (has_steal_clock)
 345                 kvm_register_steal_time();
 346 }
 347
 348 static void kvm_pv_disable_apf(void)
 349 {
 350         if (!__get_cpu_var(apf_reason).enabled)
 351                 return;
 352
 353         wrmsrl(MSR_KVM_ASYNC_PF_EN, 0);
 354         __get_cpu_var(apf_reason).enabled = 0;
 355
 356         printk(KERN_INFO"Unregister pv shared memory for cpu %d\n",
 357                smp_processor_id());
 358 }
 359
 360 static void kvm_pv_guest_cpu_reboot(void *unused)
 361 {
 362         /*
 363          * We disable PV EOI before we load a new kernel by kexec,
 364          * since MSR_KVM_PV_EOI_EN stores a pointer into old kernel's memory.
 365          * New kernel can re-enable when it boots.
 366          */
 367         if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
 368                 wrmsrl(MSR_KVM_PV_EOI_EN, 0);
 369         kvm_pv_disable_apf();
 370         kvm_disable_steal_time();
 371 }
 372
 373 static int kvm_pv_reboot_notify(struct notifier_block *nb,
 374                                 unsigned long code, void *unused)
 375 {
 376         if (code == SYS_RESTART)
 377                 on_each_cpu(kvm_pv_guest_cpu_reboot, NULL, 1);
 378         return NOTIFY_DONE;
 379 }
 380
 381 static struct notifier_block kvm_pv_reboot_nb = {
 382         .notifier_call = kvm_pv_reboot_notify,
 383 };
 384
 385 static u64 kvm_steal_clock(int cpu)
 386 {
 387         u64 steal;
 388         struct kvm_steal_time *src;
 389         int version;
 390
 391         src = &per_cpu(steal_time, cpu);
 392         do {
 393                 version = src->version;
 394                 rmb();
 395                 steal = src->steal;
 396                 rmb();
 397         } while ((version & 1) || (version != src->version));
 398
 399         return steal;
 400 }
 401
 402 void kvm_disable_steal_time(void)
 403 {
 404         if (!has_steal_clock)
 405                 return;
 406
 407         wrmsr(MSR_KVM_STEAL_TIME, 0, 0);
 408 }
 409
 410 #ifdef CONFIG_SMP
 411 static void __init kvm_smp_prepare_boot_cpu(void)
 412 {
 413         WARN_ON(kvm_register_clock("primary cpu clock"));
 414         kvm_guest_cpu_init();
 415         native_smp_prepare_boot_cpu();
 416 }
 417
 418 static void __cpuinit kvm_guest_cpu_online(void *dummy)
 419 {
 420         kvm_guest_cpu_init();
 421 }
 422
 423 static void kvm_guest_cpu_offline(void *dummy)
 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 __cpuinit kvm_cpu_notify(struct notifier_block *self,
 433                                     unsigned long action, void *hcpu)
 434 {
 435         int cpu = (unsigned long)hcpu;
 436         switch (action) {
 437         case CPU_ONLINE:
 438         case CPU_DOWN_FAILED:
 439         case CPU_ONLINE_FROZEN:
 440                 smp_call_function_single(cpu, kvm_guest_cpu_online, NULL, 0);
 441                 break;
 442         case CPU_DOWN_PREPARE:
 443         case CPU_DOWN_PREPARE_FROZEN:
 444                 smp_call_function_single(cpu, kvm_guest_cpu_offline, NULL, 1);
 445                 break;
 446         default:
 447                 break;
 448         }
 449         return NOTIFY_OK;
 450 }
 451
 452 static struct notifier_block __cpuinitdata kvm_cpu_notifier = {
 453         .notifier_call  = kvm_cpu_notify,
 454 };
 455 #endif
 456
 457 static void __init kvm_apf_trap_init(void)
 458 {
 459         set_intr_gate(14, &async_page_fault);
 460 }
 461
 462 void __init kvm_guest_init(void)
 463 {
 464         int i;
 465
 466         if (!kvm_para_available())
 467                 return;
 468
 469         paravirt_ops_setup();
 470         register_reboot_notifier(&kvm_pv_reboot_nb);
 471         for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++)
 472                 spin_lock_init(&async_pf_sleepers[i].lock);
 473         if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF))
 474                 x86_init.irqs.trap_init = kvm_apf_trap_init;
 475
 476         if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
 477                 has_steal_clock = 1;
 478                 pv_time_ops.steal_clock = kvm_steal_clock;
 479         }
 480
 481         if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
 482                 apic_set_eoi_write(kvm_guest_apic_eoi_write);
 483
 484         if (kvmclock_vsyscall)
 485                 kvm_setup_vsyscall_timeinfo();
 486
 487 #ifdef CONFIG_SMP
 488         smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
 489         register_cpu_notifier(&kvm_cpu_notifier);
 490 #else
 491         kvm_guest_cpu_init();
 492 #endif
 493 }
 494
 495 static bool __init kvm_detect(void)
 496 {
 497         if (!kvm_para_available())
 498                 return false;
 499         return true;
 500 }
 501
 502 const struct hypervisor_x86 x86_hyper_kvm __refconst = {
 503         .name                   = "KVM",
 504         .detect                 = kvm_detect,
 505 };
 506 EXPORT_SYMBOL_GPL(x86_hyper_kvm);
 507
 508 static __init int activate_jump_labels(void)
 509 {
 510         if (has_steal_clock) {
 511                 static_key_slow_inc(&paravirt_steal_enabled);
 512                 if (steal_acc)
 513                         static_key_slow_inc(&paravirt_steal_rq_enabled);
 514         }
 515
 516         return 0;
 517 }
 518 arch_initcall(activate_jump_labels);