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