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
  42 #define MMU_QUEUE_SIZE 1024
  43
  44 static int kvmapf = 1;
  45
  46 static int parse_no_kvmapf(char *arg)
  47 {
  48         kvmapf = 0;
  49         return 0;
  50 }
  51
  52 early_param("no-kvmapf", parse_no_kvmapf);
  53
  54 struct kvm_para_state {
  55         u8 mmu_queue[MMU_QUEUE_SIZE];
  56         int mmu_queue_len;
  57 };
  58
  59 static DEFINE_PER_CPU(struct kvm_para_state, para_state);
  60 static DEFINE_PER_CPU(struct kvm_vcpu_pv_apf_data, apf_reason) __aligned(64);
  61
  62 static struct kvm_para_state *kvm_para_state(void)
  63 {
  64         return &per_cpu(para_state, raw_smp_processor_id());
  65 }
  66
  67 /*
  68  * No need for any "IO delay" on KVM
  69  */
  70 static void kvm_io_delay(void)
  71 {
  72 }
  73
  74 #define KVM_TASK_SLEEP_HASHBITS 8
  75 #define KVM_TASK_SLEEP_HASHSIZE (1<<KVM_TASK_SLEEP_HASHBITS)
  76
  77 struct kvm_task_sleep_node {
  78         struct hlist_node link;
  79         wait_queue_head_t wq;
  80         u32 token;
  81         int cpu;
  82         bool halted;
  83         struct mm_struct *mm;
  84 };
  85
  86 static struct kvm_task_sleep_head {
  87         spinlock_t lock;
  88         struct hlist_head list;
  89 } async_pf_sleepers[KVM_TASK_SLEEP_HASHSIZE];
  90
  91 static struct kvm_task_sleep_node *_find_apf_task(struct kvm_task_sleep_head *b,
  92                                                   u32 token)
  93 {
  94         struct hlist_node *p;
  95
  96         hlist_for_each(p, &b->list) {
  97                 struct kvm_task_sleep_node *n =
  98                         hlist_entry(p, typeof(*n), link);
  99                 if (n->token == token)
 100                         return n;
 101         }
 102
 103         return NULL;
 104 }
 105
 106 void kvm_async_pf_task_wait(u32 token)
 107 {
 108         u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS);
 109         struct kvm_task_sleep_head *b = &async_pf_sleepers[key];
 110         struct kvm_task_sleep_node n, *e;
 111         DEFINE_WAIT(wait);
 112         int cpu, idle;
 113
 114         cpu = get_cpu();
 115         idle = idle_cpu(cpu);
 116         put_cpu();
 117
 118         spin_lock(&b->lock);
 119         e = _find_apf_task(b, token);
 120         if (e) {
 121                 /* dummy entry exist -> wake up was delivered ahead of PF */
 122                 hlist_del(&e->link);
 123                 kfree(e);
 124                 spin_unlock(&b->lock);
 125                 return;
 126         }
 127
 128         n.token = token;
 129         n.cpu = smp_processor_id();
 130         n.mm = current->active_mm;
 131         n.halted = idle || preempt_count() > 1;
 132         atomic_inc(&n.mm->mm_count);
 133         init_waitqueue_head(&n.wq);
 134         hlist_add_head(&n.link, &b->list);
 135         spin_unlock(&b->lock);
 136
 137         for (;;) {
 138                 if (!n.halted)
 139                         prepare_to_wait(&n.wq, &wait, TASK_UNINTERRUPTIBLE);
 140                 if (hlist_unhashed(&n.link))
 141                         break;
 142
 143                 if (!n.halted) {
 144                         local_irq_enable();
 145                         schedule();
 146                         local_irq_disable();
 147                 } else {
 148                         /*
 149                          * We cannot reschedule. So halt.
 150                          */
 151                         native_safe_halt();
 152                         local_irq_disable();
 153                 }
 154         }
 155         if (!n.halted)
 156                 finish_wait(&n.wq, &wait);
 157
 158         return;
 159 }
 160 EXPORT_SYMBOL_GPL(kvm_async_pf_task_wait);
 161
 162 static void apf_task_wake_one(struct kvm_task_sleep_node *n)
 163 {
 164         hlist_del_init(&n->link);
 165         if (!n->mm)
 166                 return;
 167         mmdrop(n->mm);
 168         if (n->halted)
 169                 smp_send_reschedule(n->cpu);
 170         else if (waitqueue_active(&n->wq))
 171                 wake_up(&n->wq);
 172 }
 173
 174 static void apf_task_wake_all(void)
 175 {
 176         int i;
 177
 178         for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++) {
 179                 struct hlist_node *p, *next;
 180                 struct kvm_task_sleep_head *b = &async_pf_sleepers[i];
 181                 spin_lock(&b->lock);
 182                 hlist_for_each_safe(p, next, &b->list) {
 183                         struct kvm_task_sleep_node *n =
 184                                 hlist_entry(p, typeof(*n), link);
 185                         if (n->cpu == smp_processor_id())
 186                                 apf_task_wake_one(n);
 187                 }
 188                 spin_unlock(&b->lock);
 189         }
 190 }
 191
 192 void kvm_async_pf_task_wake(u32 token)
 193 {
 194         u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS);
 195         struct kvm_task_sleep_head *b = &async_pf_sleepers[key];
 196         struct kvm_task_sleep_node *n;
 197
 198         if (token == ~0) {
 199                 apf_task_wake_all();
 200                 return;
 201         }
 202
 203 again:
 204         spin_lock(&b->lock);
 205         n = _find_apf_task(b, token);
 206         if (!n) {
 207                 /*
 208                  * async PF was not yet handled.
 209                  * Add dummy entry for the token.
 210                  */
 211                 n = kmalloc(sizeof(*n), GFP_ATOMIC);
 212                 if (!n) {
 213                         /*
 214                          * Allocation failed! Busy wait while other cpu
 215                          * handles async PF.
 216                          */
 217                         spin_unlock(&b->lock);
 218                         cpu_relax();
 219                         goto again;
 220                 }
 221                 n->token = token;
 222                 n->cpu = smp_processor_id();
 223                 n->mm = NULL;
 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                 kvm_async_pf_task_wait((u32)read_cr2());
 256                 break;
 257         case KVM_PV_REASON_PAGE_READY:
 258                 kvm_async_pf_task_wake((u32)read_cr2());
 259                 break;
 260         }
 261 }
 262
 263 static void kvm_mmu_op(void *buffer, unsigned len)
 264 {
 265         int r;
 266         unsigned long a1, a2;
 267
 268         do {
 269                 a1 = __pa(buffer);
 270                 a2 = 0;   /* on i386 __pa() always returns <4G */
 271                 r = kvm_hypercall3(KVM_HC_MMU_OP, len, a1, a2);
 272                 buffer += r;
 273                 len -= r;
 274         } while (len);
 275 }
 276
 277 static void mmu_queue_flush(struct kvm_para_state *state)
 278 {
 279         if (state->mmu_queue_len) {
 280                 kvm_mmu_op(state->mmu_queue, state->mmu_queue_len);
 281                 state->mmu_queue_len = 0;
 282         }
 283 }
 284
 285 static void kvm_deferred_mmu_op(void *buffer, int len)
 286 {
 287         struct kvm_para_state *state = kvm_para_state();
 288
 289         if (paravirt_get_lazy_mode() != PARAVIRT_LAZY_MMU) {
 290                 kvm_mmu_op(buffer, len);
 291                 return;
 292         }
 293         if (state->mmu_queue_len + len > sizeof state->mmu_queue)
 294                 mmu_queue_flush(state);
 295         memcpy(state->mmu_queue + state->mmu_queue_len, buffer, len);
 296         state->mmu_queue_len += len;
 297 }
 298
 299 static void kvm_mmu_write(void *dest, u64 val)
 300 {
 301         __u64 pte_phys;
 302         struct kvm_mmu_op_write_pte wpte;
 303
 304 #ifdef CONFIG_HIGHPTE
 305         struct page *page;
 306         unsigned long dst = (unsigned long) dest;
 307
 308         page = kmap_atomic_to_page(dest);
 309         pte_phys = page_to_pfn(page);
 310         pte_phys <<= PAGE_SHIFT;
 311         pte_phys += (dst & ~(PAGE_MASK));
 312 #else
 313         pte_phys = (unsigned long)__pa(dest);
 314 #endif
 315         wpte.header.op = KVM_MMU_OP_WRITE_PTE;
 316         wpte.pte_val = val;
 317         wpte.pte_phys = pte_phys;
 318
 319         kvm_deferred_mmu_op(&wpte, sizeof wpte);
 320 }
 321
 322 /*
 323  * We only need to hook operations that are MMU writes.  We hook these so that
 324  * we can use lazy MMU mode to batch these operations.  We could probably
 325  * improve the performance of the host code if we used some of the information
 326  * here to simplify processing of batched writes.
 327  */
 328 static void kvm_set_pte(pte_t *ptep, pte_t pte)
 329 {
 330         kvm_mmu_write(ptep, pte_val(pte));
 331 }
 332
 333 static void kvm_set_pte_at(struct mm_struct *mm, unsigned long addr,
 334                            pte_t *ptep, pte_t pte)
 335 {
 336         kvm_mmu_write(ptep, pte_val(pte));
 337 }
 338
 339 static void kvm_set_pmd(pmd_t *pmdp, pmd_t pmd)
 340 {
 341         kvm_mmu_write(pmdp, pmd_val(pmd));
 342 }
 343
 344 #if PAGETABLE_LEVELS >= 3
 345 #ifdef CONFIG_X86_PAE
 346 static void kvm_set_pte_atomic(pte_t *ptep, pte_t pte)
 347 {
 348         kvm_mmu_write(ptep, pte_val(pte));
 349 }
 350
 351 static void kvm_pte_clear(struct mm_struct *mm,
 352                           unsigned long addr, pte_t *ptep)
 353 {
 354         kvm_mmu_write(ptep, 0);
 355 }
 356
 357 static void kvm_pmd_clear(pmd_t *pmdp)
 358 {
 359         kvm_mmu_write(pmdp, 0);
 360 }
 361 #endif
 362
 363 static void kvm_set_pud(pud_t *pudp, pud_t pud)
 364 {
 365         kvm_mmu_write(pudp, pud_val(pud));
 366 }
 367
 368 #if PAGETABLE_LEVELS == 4
 369 static void kvm_set_pgd(pgd_t *pgdp, pgd_t pgd)
 370 {
 371         kvm_mmu_write(pgdp, pgd_val(pgd));
 372 }
 373 #endif
 374 #endif /* PAGETABLE_LEVELS >= 3 */
 375
 376 static void kvm_flush_tlb(void)
 377 {
 378         struct kvm_mmu_op_flush_tlb ftlb = {
 379                 .header.op = KVM_MMU_OP_FLUSH_TLB,
 380         };
 381
 382         kvm_deferred_mmu_op(&ftlb, sizeof ftlb);
 383 }
 384
 385 static void kvm_release_pt(unsigned long pfn)
 386 {
 387         struct kvm_mmu_op_release_pt rpt = {
 388                 .header.op = KVM_MMU_OP_RELEASE_PT,
 389                 .pt_phys = (u64)pfn << PAGE_SHIFT,
 390         };
 391
 392         kvm_mmu_op(&rpt, sizeof rpt);
 393 }
 394
 395 static void kvm_enter_lazy_mmu(void)
 396 {
 397         paravirt_enter_lazy_mmu();
 398 }
 399
 400 static void kvm_leave_lazy_mmu(void)
 401 {
 402         struct kvm_para_state *state = kvm_para_state();
 403
 404         mmu_queue_flush(state);
 405         paravirt_leave_lazy_mmu();
 406 }
 407
 408 static void __init paravirt_ops_setup(void)
 409 {
 410         pv_info.name = "KVM";
 411         pv_info.paravirt_enabled = 1;
 412
 413         if (kvm_para_has_feature(KVM_FEATURE_NOP_IO_DELAY))
 414                 pv_cpu_ops.io_delay = kvm_io_delay;
 415
 416         if (kvm_para_has_feature(KVM_FEATURE_MMU_OP)) {
 417                 pv_mmu_ops.set_pte = kvm_set_pte;
 418                 pv_mmu_ops.set_pte_at = kvm_set_pte_at;
 419                 pv_mmu_ops.set_pmd = kvm_set_pmd;
 420 #if PAGETABLE_LEVELS >= 3
 421 #ifdef CONFIG_X86_PAE
 422                 pv_mmu_ops.set_pte_atomic = kvm_set_pte_atomic;
 423                 pv_mmu_ops.pte_clear = kvm_pte_clear;
 424                 pv_mmu_ops.pmd_clear = kvm_pmd_clear;
 425 #endif
 426                 pv_mmu_ops.set_pud = kvm_set_pud;
 427 #if PAGETABLE_LEVELS == 4
 428                 pv_mmu_ops.set_pgd = kvm_set_pgd;
 429 #endif
 430 #endif
 431                 pv_mmu_ops.flush_tlb_user = kvm_flush_tlb;
 432                 pv_mmu_ops.release_pte = kvm_release_pt;
 433                 pv_mmu_ops.release_pmd = kvm_release_pt;
 434                 pv_mmu_ops.release_pud = kvm_release_pt;
 435
 436                 pv_mmu_ops.lazy_mode.enter = kvm_enter_lazy_mmu;
 437                 pv_mmu_ops.lazy_mode.leave = kvm_leave_lazy_mmu;
 438         }
 439 #ifdef CONFIG_X86_IO_APIC
 440         no_timer_check = 1;
 441 #endif
 442 }
 443
 444 void __cpuinit kvm_guest_cpu_init(void)
 445 {
 446         if (!kvm_para_available())
 447                 return;
 448
 449         if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF) && kvmapf) {
 450                 u64 pa = __pa(&__get_cpu_var(apf_reason));
 451
 452 #ifdef CONFIG_PREEMPT
 453                 pa |= KVM_ASYNC_PF_SEND_ALWAYS;
 454 #endif
 455                 wrmsrl(MSR_KVM_ASYNC_PF_EN, pa | KVM_ASYNC_PF_ENABLED);
 456                 __get_cpu_var(apf_reason).enabled = 1;
 457                 printk(KERN_INFO"KVM setup async PF for cpu %d\n",
 458                        smp_processor_id());
 459         }
 460 }
 461
 462 static void kvm_pv_disable_apf(void *unused)
 463 {
 464         if (!__get_cpu_var(apf_reason).enabled)
 465                 return;
 466
 467         wrmsrl(MSR_KVM_ASYNC_PF_EN, 0);
 468         __get_cpu_var(apf_reason).enabled = 0;
 469
 470         printk(KERN_INFO"Unregister pv shared memory for cpu %d\n",
 471                smp_processor_id());
 472 }
 473
 474 static int kvm_pv_reboot_notify(struct notifier_block *nb,
 475                                 unsigned long code, void *unused)
 476 {
 477         if (code == SYS_RESTART)
 478                 on_each_cpu(kvm_pv_disable_apf, NULL, 1);
 479         return NOTIFY_DONE;
 480 }
 481
 482 static struct notifier_block kvm_pv_reboot_nb = {
 483         .notifier_call = kvm_pv_reboot_notify,
 484 };
 485
 486 #ifdef CONFIG_SMP
 487 static void __init kvm_smp_prepare_boot_cpu(void)
 488 {
 489 #ifdef CONFIG_KVM_CLOCK
 490         WARN_ON(kvm_register_clock("primary cpu clock"));
 491 #endif
 492         kvm_guest_cpu_init();
 493         native_smp_prepare_boot_cpu();
 494 }
 495
 496 static void kvm_guest_cpu_online(void *dummy)
 497 {
 498         kvm_guest_cpu_init();
 499 }
 500
 501 static void kvm_guest_cpu_offline(void *dummy)
 502 {
 503         kvm_pv_disable_apf(NULL);
 504         apf_task_wake_all();
 505 }
 506
 507 static int __cpuinit kvm_cpu_notify(struct notifier_block *self,
 508                                     unsigned long action, void *hcpu)
 509 {
 510         int cpu = (unsigned long)hcpu;
 511         switch (action) {
 512         case CPU_ONLINE:
 513         case CPU_DOWN_FAILED:
 514         case CPU_ONLINE_FROZEN:
 515                 smp_call_function_single(cpu, kvm_guest_cpu_online, NULL, 0);
 516                 break;
 517         case CPU_DOWN_PREPARE:
 518         case CPU_DOWN_PREPARE_FROZEN:
 519                 smp_call_function_single(cpu, kvm_guest_cpu_offline, NULL, 1);
 520                 break;
 521         default:
 522                 break;
 523         }
 524         return NOTIFY_OK;
 525 }
 526
 527 static struct notifier_block __cpuinitdata kvm_cpu_notifier = {
 528         .notifier_call  = kvm_cpu_notify,
 529 };
 530 #endif
 531
 532 static void __init kvm_apf_trap_init(void)
 533 {
 534         set_intr_gate(14, &async_page_fault);
 535 }
 536
 537 void __init kvm_guest_init(void)
 538 {
 539         int i;
 540
 541         if (!kvm_para_available())
 542                 return;
 543
 544         paravirt_ops_setup();
 545         register_reboot_notifier(&kvm_pv_reboot_nb);
 546         for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++)
 547                 spin_lock_init(&async_pf_sleepers[i].lock);
 548         if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF))
 549                 x86_init.irqs.trap_init = kvm_apf_trap_init;
 550
 551 #ifdef CONFIG_SMP
 552         smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
 553         register_cpu_notifier(&kvm_cpu_notifier);
 554 #else
 555         kvm_guest_cpu_init();
 556 #endif
 557 }