virt/kvm/eventfd.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * kvm eventfd support - use eventfd objects to signal various KVM events
   4  *
   5  * Copyright 2009 Novell.  All Rights Reserved.
   6  * Copyright 2010 Red Hat, Inc. and/or its affiliates.
   7  *
   8  * Author:
   9  *      Gregory Haskins <ghaskins@novell.com>
  10  */
  11
  12 #include <linux/kvm_host.h>
  13 #include <linux/kvm.h>
  14 #include <linux/kvm_irqfd.h>
  15 #include <linux/workqueue.h>
  16 #include <linux/syscalls.h>
  17 #include <linux/wait.h>
  18 #include <linux/poll.h>
  19 #include <linux/file.h>
  20 #include <linux/list.h>
  21 #include <linux/eventfd.h>
  22 #include <linux/kernel.h>
  23 #include <linux/srcu.h>
  24 #include <linux/slab.h>
  25 #include <linux/seqlock.h>
  26 #include <linux/irqbypass.h>
  27 #include <trace/events/kvm.h>
  28
  29 #include <kvm/iodev.h>
  30
  31 #ifdef CONFIG_HAVE_KVM_IRQFD
  32
  33 static struct workqueue_struct *irqfd_cleanup_wq;
  34
  35 bool __attribute__((weak))
  36 kvm_arch_irqfd_allowed(struct kvm *kvm, struct kvm_irqfd *args)
  37 {
  38         return true;
  39 }
  40
  41 static void
  42 irqfd_inject(struct work_struct *work)
  43 {
  44         struct kvm_kernel_irqfd *irqfd =
  45                 container_of(work, struct kvm_kernel_irqfd, inject);
  46         struct kvm *kvm = irqfd->kvm;
  47
  48         if (!irqfd->resampler) {
  49                 kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 1,
  50                                 false);
  51                 kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 0,
  52                                 false);
  53         } else
  54                 kvm_set_irq(kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
  55                             irqfd->gsi, 1, false);
  56 }
  57
  58 /*
  59  * Since resampler irqfds share an IRQ source ID, we de-assert once
  60  * then notify all of the resampler irqfds using this GSI.  We can't
  61  * do multiple de-asserts or we risk racing with incoming re-asserts.
  62  */
  63 static void
  64 irqfd_resampler_ack(struct kvm_irq_ack_notifier *kian)
  65 {
  66         struct kvm_kernel_irqfd_resampler *resampler;
  67         struct kvm *kvm;
  68         struct kvm_kernel_irqfd *irqfd;
  69         int idx;
  70
  71         resampler = container_of(kian,
  72                         struct kvm_kernel_irqfd_resampler, notifier);
  73         kvm = resampler->kvm;
  74
  75         kvm_set_irq(kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
  76                     resampler->notifier.gsi, 0, false);
  77
  78         idx = srcu_read_lock(&kvm->irq_srcu);
  79
  80         list_for_each_entry_rcu(irqfd, &resampler->list, resampler_link)
  81                 eventfd_signal(irqfd->resamplefd, 1);
  82
  83         srcu_read_unlock(&kvm->irq_srcu, idx);
  84 }
  85
  86 static void
  87 irqfd_resampler_shutdown(struct kvm_kernel_irqfd *irqfd)
  88 {
  89         struct kvm_kernel_irqfd_resampler *resampler = irqfd->resampler;
  90         struct kvm *kvm = resampler->kvm;
  91
  92         mutex_lock(&kvm->irqfds.resampler_lock);
  93
  94         list_del_rcu(&irqfd->resampler_link);
  95         synchronize_srcu(&kvm->irq_srcu);
  96
  97         if (list_empty(&resampler->list)) {
  98                 list_del(&resampler->link);
  99                 kvm_unregister_irq_ack_notifier(kvm, &resampler->notifier);
 100                 kvm_set_irq(kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
 101                             resampler->notifier.gsi, 0, false);
 102                 kfree(resampler);
 103         }
 104
 105         mutex_unlock(&kvm->irqfds.resampler_lock);
 106 }
 107
 108 /*
 109  * Race-free decouple logic (ordering is critical)
 110  */
 111 static void
 112 irqfd_shutdown(struct work_struct *work)
 113 {
 114         struct kvm_kernel_irqfd *irqfd =
 115                 container_of(work, struct kvm_kernel_irqfd, shutdown);
 116         struct kvm *kvm = irqfd->kvm;
 117         u64 cnt;
 118
 119         /* Make sure irqfd has been initialized in assign path. */
 120         synchronize_srcu(&kvm->irq_srcu);
 121
 122         /*
 123          * Synchronize with the wait-queue and unhook ourselves to prevent
 124          * further events.
 125          */
 126         eventfd_ctx_remove_wait_queue(irqfd->eventfd, &irqfd->wait, &cnt);
 127
 128         /*
 129          * We know no new events will be scheduled at this point, so block
 130          * until all previously outstanding events have completed
 131          */
 132         flush_work(&irqfd->inject);
 133
 134         if (irqfd->resampler) {
 135                 irqfd_resampler_shutdown(irqfd);
 136                 eventfd_ctx_put(irqfd->resamplefd);
 137         }
 138
 139         /*
 140          * It is now safe to release the object's resources
 141          */
 142 #ifdef CONFIG_HAVE_KVM_IRQ_BYPASS
 143         irq_bypass_unregister_consumer(&irqfd->consumer);
 144 #endif
 145         eventfd_ctx_put(irqfd->eventfd);
 146         kfree(irqfd);
 147 }
 148
 149
 150 /* assumes kvm->irqfds.lock is held */
 151 static bool
 152 irqfd_is_active(struct kvm_kernel_irqfd *irqfd)
 153 {
 154         return list_empty(&irqfd->list) ? false : true;
 155 }
 156
 157 /*
 158  * Mark the irqfd as inactive and schedule it for removal
 159  *
 160  * assumes kvm->irqfds.lock is held
 161  */
 162 static void
 163 irqfd_deactivate(struct kvm_kernel_irqfd *irqfd)
 164 {
 165         BUG_ON(!irqfd_is_active(irqfd));
 166
 167         list_del_init(&irqfd->list);
 168
 169         queue_work(irqfd_cleanup_wq, &irqfd->shutdown);
 170 }
 171
 172 int __attribute__((weak)) kvm_arch_set_irq_inatomic(
 173                                 struct kvm_kernel_irq_routing_entry *irq,
 174                                 struct kvm *kvm, int irq_source_id,
 175                                 int level,
 176                                 bool line_status)
 177 {
 178         return -EWOULDBLOCK;
 179 }
 180
 181 /*
 182  * Called with wqh->lock held and interrupts disabled
 183  */
 184 static int
 185 irqfd_wakeup(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
 186 {
 187         struct kvm_kernel_irqfd *irqfd =
 188                 container_of(wait, struct kvm_kernel_irqfd, wait);
 189         __poll_t flags = key_to_poll(key);
 190         struct kvm_kernel_irq_routing_entry irq;
 191         struct kvm *kvm = irqfd->kvm;
 192         unsigned seq;
 193         int idx;
 194
 195         if (flags & EPOLLIN) {
 196                 idx = srcu_read_lock(&kvm->irq_srcu);
 197                 do {
 198                         seq = read_seqcount_begin(&irqfd->irq_entry_sc);
 199                         irq = irqfd->irq_entry;
 200                 } while (read_seqcount_retry(&irqfd->irq_entry_sc, seq));
 201                 /* An event has been signaled, inject an interrupt */
 202                 if (kvm_arch_set_irq_inatomic(&irq, kvm,
 203                                               KVM_USERSPACE_IRQ_SOURCE_ID, 1,
 204                                               false) == -EWOULDBLOCK)
 205                         schedule_work(&irqfd->inject);
 206                 srcu_read_unlock(&kvm->irq_srcu, idx);
 207         }
 208
 209         if (flags & EPOLLHUP) {
 210                 /* The eventfd is closing, detach from KVM */
 211                 unsigned long iflags;
 212
 213                 spin_lock_irqsave(&kvm->irqfds.lock, iflags);
 214
 215                 /*
 216                  * We must check if someone deactivated the irqfd before
 217                  * we could acquire the irqfds.lock since the item is
 218                  * deactivated from the KVM side before it is unhooked from
 219                  * the wait-queue.  If it is already deactivated, we can
 220                  * simply return knowing the other side will cleanup for us.
 221                  * We cannot race against the irqfd going away since the
 222                  * other side is required to acquire wqh->lock, which we hold
 223                  */
 224                 if (irqfd_is_active(irqfd))
 225                         irqfd_deactivate(irqfd);
 226
 227                 spin_unlock_irqrestore(&kvm->irqfds.lock, iflags);
 228         }
 229
 230         return 0;
 231 }
 232
 233 static void
 234 irqfd_ptable_queue_proc(struct file *file, wait_queue_head_t *wqh,
 235                         poll_table *pt)
 236 {
 237         struct kvm_kernel_irqfd *irqfd =
 238                 container_of(pt, struct kvm_kernel_irqfd, pt);
 239         add_wait_queue(wqh, &irqfd->wait);
 240 }
 241
 242 /* Must be called under irqfds.lock */
 243 static void irqfd_update(struct kvm *kvm, struct kvm_kernel_irqfd *irqfd)
 244 {
 245         struct kvm_kernel_irq_routing_entry *e;
 246         struct kvm_kernel_irq_routing_entry entries[KVM_NR_IRQCHIPS];
 247         int n_entries;
 248
 249         n_entries = kvm_irq_map_gsi(kvm, entries, irqfd->gsi);
 250
 251         write_seqcount_begin(&irqfd->irq_entry_sc);
 252
 253         e = entries;
 254         if (n_entries == 1)
 255                 irqfd->irq_entry = *e;
 256         else
 257                 irqfd->irq_entry.type = 0;
 258
 259         write_seqcount_end(&irqfd->irq_entry_sc);
 260 }
 261
 262 #ifdef CONFIG_HAVE_KVM_IRQ_BYPASS
 263 void __attribute__((weak)) kvm_arch_irq_bypass_stop(
 264                                 struct irq_bypass_consumer *cons)
 265 {
 266 }
 267
 268 void __attribute__((weak)) kvm_arch_irq_bypass_start(
 269                                 struct irq_bypass_consumer *cons)
 270 {
 271 }
 272
 273 int  __attribute__((weak)) kvm_arch_update_irqfd_routing(
 274                                 struct kvm *kvm, unsigned int host_irq,
 275                                 uint32_t guest_irq, bool set)
 276 {
 277         return 0;
 278 }
 279 #endif
 280
 281 static int
 282 kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args)
 283 {
 284         struct kvm_kernel_irqfd *irqfd, *tmp;
 285         struct fd f;
 286         struct eventfd_ctx *eventfd = NULL, *resamplefd = NULL;
 287         int ret;
 288         __poll_t events;
 289         int idx;
 290
 291         if (!kvm_arch_intc_initialized(kvm))
 292                 return -EAGAIN;
 293
 294         if (!kvm_arch_irqfd_allowed(kvm, args))
 295                 return -EINVAL;
 296
 297         irqfd = kzalloc(sizeof(*irqfd), GFP_KERNEL_ACCOUNT);
 298         if (!irqfd)
 299                 return -ENOMEM;
 300
 301         irqfd->kvm = kvm;
 302         irqfd->gsi = args->gsi;
 303         INIT_LIST_HEAD(&irqfd->list);
 304         INIT_WORK(&irqfd->inject, irqfd_inject);
 305         INIT_WORK(&irqfd->shutdown, irqfd_shutdown);
 306         seqcount_spinlock_init(&irqfd->irq_entry_sc, &kvm->irqfds.lock);
 307
 308         f = fdget(args->fd);
 309         if (!f.file) {
 310                 ret = -EBADF;
 311                 goto out;
 312         }
 313
 314         eventfd = eventfd_ctx_fileget(f.file);
 315         if (IS_ERR(eventfd)) {
 316                 ret = PTR_ERR(eventfd);
 317                 goto fail;
 318         }
 319
 320         irqfd->eventfd = eventfd;
 321
 322         if (args->flags & KVM_IRQFD_FLAG_RESAMPLE) {
 323                 struct kvm_kernel_irqfd_resampler *resampler;
 324
 325                 resamplefd = eventfd_ctx_fdget(args->resamplefd);
 326                 if (IS_ERR(resamplefd)) {
 327                         ret = PTR_ERR(resamplefd);
 328                         goto fail;
 329                 }
 330
 331                 irqfd->resamplefd = resamplefd;
 332                 INIT_LIST_HEAD(&irqfd->resampler_link);
 333
 334                 mutex_lock(&kvm->irqfds.resampler_lock);
 335
 336                 list_for_each_entry(resampler,
 337                                     &kvm->irqfds.resampler_list, link) {
 338                         if (resampler->notifier.gsi == irqfd->gsi) {
 339                                 irqfd->resampler = resampler;
 340                                 break;
 341                         }
 342                 }
 343
 344                 if (!irqfd->resampler) {
 345                         resampler = kzalloc(sizeof(*resampler),
 346                                             GFP_KERNEL_ACCOUNT);
 347                         if (!resampler) {
 348                                 ret = -ENOMEM;
 349                                 mutex_unlock(&kvm->irqfds.resampler_lock);
 350                                 goto fail;
 351                         }
 352
 353                         resampler->kvm = kvm;
 354                         INIT_LIST_HEAD(&resampler->list);
 355                         resampler->notifier.gsi = irqfd->gsi;
 356                         resampler->notifier.irq_acked = irqfd_resampler_ack;
 357                         INIT_LIST_HEAD(&resampler->link);
 358
 359                         list_add(&resampler->link, &kvm->irqfds.resampler_list);
 360                         kvm_register_irq_ack_notifier(kvm,
 361                                                       &resampler->notifier);
 362                         irqfd->resampler = resampler;
 363                 }
 364
 365                 list_add_rcu(&irqfd->resampler_link, &irqfd->resampler->list);
 366                 synchronize_srcu(&kvm->irq_srcu);
 367
 368                 mutex_unlock(&kvm->irqfds.resampler_lock);
 369         }
 370
 371         /*
 372          * Install our own custom wake-up handling so we are notified via
 373          * a callback whenever someone signals the underlying eventfd
 374          */
 375         init_waitqueue_func_entry(&irqfd->wait, irqfd_wakeup);
 376         init_poll_funcptr(&irqfd->pt, irqfd_ptable_queue_proc);
 377
 378         spin_lock_irq(&kvm->irqfds.lock);
 379
 380         ret = 0;
 381         list_for_each_entry(tmp, &kvm->irqfds.items, list) {
 382                 if (irqfd->eventfd != tmp->eventfd)
 383                         continue;
 384                 /* This fd is used for another irq already. */
 385                 ret = -EBUSY;
 386                 spin_unlock_irq(&kvm->irqfds.lock);
 387                 goto fail;
 388         }
 389
 390         idx = srcu_read_lock(&kvm->irq_srcu);
 391         irqfd_update(kvm, irqfd);
 392
 393         list_add_tail(&irqfd->list, &kvm->irqfds.items);
 394
 395         spin_unlock_irq(&kvm->irqfds.lock);
 396
 397         /*
 398          * Check if there was an event already pending on the eventfd
 399          * before we registered, and trigger it as if we didn't miss it.
 400          */
 401         events = vfs_poll(f.file, &irqfd->pt);
 402
 403         if (events & EPOLLIN)
 404                 schedule_work(&irqfd->inject);
 405
 406 #ifdef CONFIG_HAVE_KVM_IRQ_BYPASS
 407         if (kvm_arch_has_irq_bypass()) {
 408                 irqfd->consumer.token = (void *)irqfd->eventfd;
 409                 irqfd->consumer.add_producer = kvm_arch_irq_bypass_add_producer;
 410                 irqfd->consumer.del_producer = kvm_arch_irq_bypass_del_producer;
 411                 irqfd->consumer.stop = kvm_arch_irq_bypass_stop;
 412                 irqfd->consumer.start = kvm_arch_irq_bypass_start;
 413                 ret = irq_bypass_register_consumer(&irqfd->consumer);
 414                 if (ret)
 415                         pr_info("irq bypass consumer (token %p) registration fails: %d\n",
 416                                 irqfd->consumer.token, ret);
 417         }
 418 #endif
 419
 420         srcu_read_unlock(&kvm->irq_srcu, idx);
 421
 422         /*
 423          * do not drop the file until the irqfd is fully initialized, otherwise
 424          * we might race against the EPOLLHUP
 425          */
 426         fdput(f);
 427         return 0;
 428
 429 fail:
 430         if (irqfd->resampler)
 431                 irqfd_resampler_shutdown(irqfd);
 432
 433         if (resamplefd && !IS_ERR(resamplefd))
 434                 eventfd_ctx_put(resamplefd);
 435
 436         if (eventfd && !IS_ERR(eventfd))
 437                 eventfd_ctx_put(eventfd);
 438
 439         fdput(f);
 440
 441 out:
 442         kfree(irqfd);
 443         return ret;
 444 }
 445
 446 bool kvm_irq_has_notifier(struct kvm *kvm, unsigned irqchip, unsigned pin)
 447 {
 448         struct kvm_irq_ack_notifier *kian;
 449         int gsi, idx;
 450
 451         idx = srcu_read_lock(&kvm->irq_srcu);
 452         gsi = kvm_irq_map_chip_pin(kvm, irqchip, pin);
 453         if (gsi != -1)
 454                 hlist_for_each_entry_rcu(kian, &kvm->irq_ack_notifier_list,
 455                                          link)
 456                         if (kian->gsi == gsi) {
 457                                 srcu_read_unlock(&kvm->irq_srcu, idx);
 458                                 return true;
 459                         }
 460
 461         srcu_read_unlock(&kvm->irq_srcu, idx);
 462
 463         return false;
 464 }
 465 EXPORT_SYMBOL_GPL(kvm_irq_has_notifier);
 466
 467 void kvm_notify_acked_gsi(struct kvm *kvm, int gsi)
 468 {
 469         struct kvm_irq_ack_notifier *kian;
 470
 471         hlist_for_each_entry_rcu(kian, &kvm->irq_ack_notifier_list,
 472                                  link)
 473                 if (kian->gsi == gsi)
 474                         kian->irq_acked(kian);
 475 }
 476
 477 void kvm_notify_acked_irq(struct kvm *kvm, unsigned irqchip, unsigned pin)
 478 {
 479         int gsi, idx;
 480
 481         trace_kvm_ack_irq(irqchip, pin);
 482
 483         idx = srcu_read_lock(&kvm->irq_srcu);
 484         gsi = kvm_irq_map_chip_pin(kvm, irqchip, pin);
 485         if (gsi != -1)
 486                 kvm_notify_acked_gsi(kvm, gsi);
 487         srcu_read_unlock(&kvm->irq_srcu, idx);
 488 }
 489
 490 void kvm_register_irq_ack_notifier(struct kvm *kvm,
 491                                    struct kvm_irq_ack_notifier *kian)
 492 {
 493         mutex_lock(&kvm->irq_lock);
 494         hlist_add_head_rcu(&kian->link, &kvm->irq_ack_notifier_list);
 495         mutex_unlock(&kvm->irq_lock);
 496         kvm_arch_post_irq_ack_notifier_list_update(kvm);
 497 }
 498
 499 void kvm_unregister_irq_ack_notifier(struct kvm *kvm,
 500                                     struct kvm_irq_ack_notifier *kian)
 501 {
 502         mutex_lock(&kvm->irq_lock);
 503         hlist_del_init_rcu(&kian->link);
 504         mutex_unlock(&kvm->irq_lock);
 505         synchronize_srcu(&kvm->irq_srcu);
 506         kvm_arch_post_irq_ack_notifier_list_update(kvm);
 507 }
 508 #endif
 509
 510 void
 511 kvm_eventfd_init(struct kvm *kvm)
 512 {
 513 #ifdef CONFIG_HAVE_KVM_IRQFD
 514         spin_lock_init(&kvm->irqfds.lock);
 515         INIT_LIST_HEAD(&kvm->irqfds.items);
 516         INIT_LIST_HEAD(&kvm->irqfds.resampler_list);
 517         mutex_init(&kvm->irqfds.resampler_lock);
 518 #endif
 519         INIT_LIST_HEAD(&kvm->ioeventfds);
 520 }
 521
 522 #ifdef CONFIG_HAVE_KVM_IRQFD
 523 /*
 524  * shutdown any irqfd's that match fd+gsi
 525  */
 526 static int
 527 kvm_irqfd_deassign(struct kvm *kvm, struct kvm_irqfd *args)
 528 {
 529         struct kvm_kernel_irqfd *irqfd, *tmp;
 530         struct eventfd_ctx *eventfd;
 531
 532         eventfd = eventfd_ctx_fdget(args->fd);
 533         if (IS_ERR(eventfd))
 534                 return PTR_ERR(eventfd);
 535
 536         spin_lock_irq(&kvm->irqfds.lock);
 537
 538         list_for_each_entry_safe(irqfd, tmp, &kvm->irqfds.items, list) {
 539                 if (irqfd->eventfd == eventfd && irqfd->gsi == args->gsi) {
 540                         /*
 541                          * This clearing of irq_entry.type is needed for when
 542                          * another thread calls kvm_irq_routing_update before
 543                          * we flush workqueue below (we synchronize with
 544                          * kvm_irq_routing_update using irqfds.lock).
 545                          */
 546                         write_seqcount_begin(&irqfd->irq_entry_sc);
 547                         irqfd->irq_entry.type = 0;
 548                         write_seqcount_end(&irqfd->irq_entry_sc);
 549                         irqfd_deactivate(irqfd);
 550                 }
 551         }
 552
 553         spin_unlock_irq(&kvm->irqfds.lock);
 554         eventfd_ctx_put(eventfd);
 555
 556         /*
 557          * Block until we know all outstanding shutdown jobs have completed
 558          * so that we guarantee there will not be any more interrupts on this
 559          * gsi once this deassign function returns.
 560          */
 561         flush_workqueue(irqfd_cleanup_wq);
 562
 563         return 0;
 564 }
 565
 566 int
 567 kvm_irqfd(struct kvm *kvm, struct kvm_irqfd *args)
 568 {
 569         if (args->flags & ~(KVM_IRQFD_FLAG_DEASSIGN | KVM_IRQFD_FLAG_RESAMPLE))
 570                 return -EINVAL;
 571
 572         if (args->flags & KVM_IRQFD_FLAG_DEASSIGN)
 573                 return kvm_irqfd_deassign(kvm, args);
 574
 575         return kvm_irqfd_assign(kvm, args);
 576 }
 577
 578 /*
 579  * This function is called as the kvm VM fd is being released. Shutdown all
 580  * irqfds that still remain open
 581  */
 582 void
 583 kvm_irqfd_release(struct kvm *kvm)
 584 {
 585         struct kvm_kernel_irqfd *irqfd, *tmp;
 586
 587         spin_lock_irq(&kvm->irqfds.lock);
 588
 589         list_for_each_entry_safe(irqfd, tmp, &kvm->irqfds.items, list)
 590                 irqfd_deactivate(irqfd);
 591
 592         spin_unlock_irq(&kvm->irqfds.lock);
 593
 594         /*
 595          * Block until we know all outstanding shutdown jobs have completed
 596          * since we do not take a kvm* reference.
 597          */
 598         flush_workqueue(irqfd_cleanup_wq);
 599
 600 }
 601
 602 /*
 603  * Take note of a change in irq routing.
 604  * Caller must invoke synchronize_srcu(&kvm->irq_srcu) afterwards.
 605  */
 606 void kvm_irq_routing_update(struct kvm *kvm)
 607 {
 608         struct kvm_kernel_irqfd *irqfd;
 609
 610         spin_lock_irq(&kvm->irqfds.lock);
 611
 612         list_for_each_entry(irqfd, &kvm->irqfds.items, list) {
 613                 irqfd_update(kvm, irqfd);
 614
 615 #ifdef CONFIG_HAVE_KVM_IRQ_BYPASS
 616                 if (irqfd->producer) {
 617                         int ret = kvm_arch_update_irqfd_routing(
 618                                         irqfd->kvm, irqfd->producer->irq,
 619                                         irqfd->gsi, 1);
 620                         WARN_ON(ret);
 621                 }
 622 #endif
 623         }
 624
 625         spin_unlock_irq(&kvm->irqfds.lock);
 626 }
 627
 628 /*
 629  * create a host-wide workqueue for issuing deferred shutdown requests
 630  * aggregated from all vm* instances. We need our own isolated
 631  * queue to ease flushing work items when a VM exits.
 632  */
 633 int kvm_irqfd_init(void)
 634 {
 635         irqfd_cleanup_wq = alloc_workqueue("kvm-irqfd-cleanup", 0, 0);
 636         if (!irqfd_cleanup_wq)
 637                 return -ENOMEM;
 638
 639         return 0;
 640 }
 641
 642 void kvm_irqfd_exit(void)
 643 {
 644         destroy_workqueue(irqfd_cleanup_wq);
 645 }
 646 #endif
 647
 648 /*
 649  * --------------------------------------------------------------------
 650  * ioeventfd: translate a PIO/MMIO memory write to an eventfd signal.
 651  *
 652  * userspace can register a PIO/MMIO address with an eventfd for receiving
 653  * notification when the memory has been touched.
 654  * --------------------------------------------------------------------
 655  */
 656
 657 struct _ioeventfd {
 658         struct list_head     list;
 659         u64                  addr;
 660         int                  length;
 661         struct eventfd_ctx  *eventfd;
 662         u64                  datamatch;
 663         struct kvm_io_device dev;
 664         u8                   bus_idx;
 665         bool                 wildcard;
 666 };
 667
 668 static inline struct _ioeventfd *
 669 to_ioeventfd(struct kvm_io_device *dev)
 670 {
 671         return container_of(dev, struct _ioeventfd, dev);
 672 }
 673
 674 static void
 675 ioeventfd_release(struct _ioeventfd *p)
 676 {
 677         eventfd_ctx_put(p->eventfd);
 678         list_del(&p->list);
 679         kfree(p);
 680 }
 681
 682 static bool
 683 ioeventfd_in_range(struct _ioeventfd *p, gpa_t addr, int len, const void *val)
 684 {
 685         u64 _val;
 686
 687         if (addr != p->addr)
 688                 /* address must be precise for a hit */
 689                 return false;
 690
 691         if (!p->length)
 692                 /* length = 0 means only look at the address, so always a hit */
 693                 return true;
 694
 695         if (len != p->length)
 696                 /* address-range must be precise for a hit */
 697                 return false;
 698
 699         if (p->wildcard)
 700                 /* all else equal, wildcard is always a hit */
 701                 return true;
 702
 703         /* otherwise, we have to actually compare the data */
 704
 705         BUG_ON(!IS_ALIGNED((unsigned long)val, len));
 706
 707         switch (len) {
 708         case 1:
 709                 _val = *(u8 *)val;
 710                 break;
 711         case 2:
 712                 _val = *(u16 *)val;
 713                 break;
 714         case 4:
 715                 _val = *(u32 *)val;
 716                 break;
 717         case 8:
 718                 _val = *(u64 *)val;
 719                 break;
 720         default:
 721                 return false;
 722         }
 723
 724         return _val == p->datamatch;
 725 }
 726
 727 /* MMIO/PIO writes trigger an event if the addr/val match */
 728 static int
 729 ioeventfd_write(struct kvm_vcpu *vcpu, struct kvm_io_device *this, gpa_t addr,
 730                 int len, const void *val)
 731 {
 732         struct _ioeventfd *p = to_ioeventfd(this);
 733
 734         if (!ioeventfd_in_range(p, addr, len, val))
 735                 return -EOPNOTSUPP;
 736
 737         eventfd_signal(p->eventfd, 1);
 738         return 0;
 739 }
 740
 741 /*
 742  * This function is called as KVM is completely shutting down.  We do not
 743  * need to worry about locking just nuke anything we have as quickly as possible
 744  */
 745 static void
 746 ioeventfd_destructor(struct kvm_io_device *this)
 747 {
 748         struct _ioeventfd *p = to_ioeventfd(this);
 749
 750         ioeventfd_release(p);
 751 }
 752
 753 static const struct kvm_io_device_ops ioeventfd_ops = {
 754         .write      = ioeventfd_write,
 755         .destructor = ioeventfd_destructor,
 756 };
 757
 758 /* assumes kvm->slots_lock held */
 759 static bool
 760 ioeventfd_check_collision(struct kvm *kvm, struct _ioeventfd *p)
 761 {
 762         struct _ioeventfd *_p;
 763
 764         list_for_each_entry(_p, &kvm->ioeventfds, list)
 765                 if (_p->bus_idx == p->bus_idx &&
 766                     _p->addr == p->addr &&
 767                     (!_p->length || !p->length ||
 768                      (_p->length == p->length &&
 769                       (_p->wildcard || p->wildcard ||
 770                        _p->datamatch == p->datamatch))))
 771                         return true;
 772
 773         return false;
 774 }
 775
 776 static enum kvm_bus ioeventfd_bus_from_flags(__u32 flags)
 777 {
 778         if (flags & KVM_IOEVENTFD_FLAG_PIO)
 779                 return KVM_PIO_BUS;
 780         if (flags & KVM_IOEVENTFD_FLAG_VIRTIO_CCW_NOTIFY)
 781                 return KVM_VIRTIO_CCW_NOTIFY_BUS;
 782         return KVM_MMIO_BUS;
 783 }
 784
 785 static int kvm_assign_ioeventfd_idx(struct kvm *kvm,
 786                                 enum kvm_bus bus_idx,
 787                                 struct kvm_ioeventfd *args)
 788 {
 789
 790         struct eventfd_ctx *eventfd;
 791         struct _ioeventfd *p;
 792         int ret;
 793
 794         eventfd = eventfd_ctx_fdget(args->fd);
 795         if (IS_ERR(eventfd))
 796                 return PTR_ERR(eventfd);
 797
 798         p = kzalloc(sizeof(*p), GFP_KERNEL_ACCOUNT);
 799         if (!p) {
 800                 ret = -ENOMEM;
 801                 goto fail;
 802         }
 803
 804         INIT_LIST_HEAD(&p->list);
 805         p->addr    = args->addr;
 806         p->bus_idx = bus_idx;
 807         p->length  = args->len;
 808         p->eventfd = eventfd;
 809
 810         /* The datamatch feature is optional, otherwise this is a wildcard */
 811         if (args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH)
 812                 p->datamatch = args->datamatch;
 813         else
 814                 p->wildcard = true;
 815
 816         mutex_lock(&kvm->slots_lock);
 817
 818         /* Verify that there isn't a match already */
 819         if (ioeventfd_check_collision(kvm, p)) {
 820                 ret = -EEXIST;
 821                 goto unlock_fail;
 822         }
 823
 824         kvm_iodevice_init(&p->dev, &ioeventfd_ops);
 825
 826         ret = kvm_io_bus_register_dev(kvm, bus_idx, p->addr, p->length,
 827                                       &p->dev);
 828         if (ret < 0)
 829                 goto unlock_fail;
 830
 831         kvm_get_bus(kvm, bus_idx)->ioeventfd_count++;
 832         list_add_tail(&p->list, &kvm->ioeventfds);
 833
 834         mutex_unlock(&kvm->slots_lock);
 835
 836         return 0;
 837
 838 unlock_fail:
 839         mutex_unlock(&kvm->slots_lock);
 840
 841 fail:
 842         kfree(p);
 843         eventfd_ctx_put(eventfd);
 844
 845         return ret;
 846 }
 847
 848 static int
 849 kvm_deassign_ioeventfd_idx(struct kvm *kvm, enum kvm_bus bus_idx,
 850                            struct kvm_ioeventfd *args)
 851 {
 852         struct _ioeventfd        *p, *tmp;
 853         struct eventfd_ctx       *eventfd;
 854         struct kvm_io_bus        *bus;
 855         int                       ret = -ENOENT;
 856         bool                      wildcard;
 857
 858         eventfd = eventfd_ctx_fdget(args->fd);
 859         if (IS_ERR(eventfd))
 860                 return PTR_ERR(eventfd);
 861
 862         wildcard = !(args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH);
 863
 864         mutex_lock(&kvm->slots_lock);
 865
 866         list_for_each_entry_safe(p, tmp, &kvm->ioeventfds, list) {
 867
 868                 if (p->bus_idx != bus_idx ||
 869                     p->eventfd != eventfd  ||
 870                     p->addr != args->addr  ||
 871                     p->length != args->len ||
 872                     p->wildcard != wildcard)
 873                         continue;
 874
 875                 if (!p->wildcard && p->datamatch != args->datamatch)
 876                         continue;
 877
 878                 kvm_io_bus_unregister_dev(kvm, bus_idx, &p->dev);
 879                 bus = kvm_get_bus(kvm, bus_idx);
 880                 if (bus)
 881                         bus->ioeventfd_count--;
 882                 ioeventfd_release(p);
 883                 ret = 0;
 884                 break;
 885         }
 886
 887         mutex_unlock(&kvm->slots_lock);
 888
 889         eventfd_ctx_put(eventfd);
 890
 891         return ret;
 892 }
 893
 894 static int kvm_deassign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
 895 {
 896         enum kvm_bus bus_idx = ioeventfd_bus_from_flags(args->flags);
 897         int ret = kvm_deassign_ioeventfd_idx(kvm, bus_idx, args);
 898
 899         if (!args->len && bus_idx == KVM_MMIO_BUS)
 900                 kvm_deassign_ioeventfd_idx(kvm, KVM_FAST_MMIO_BUS, args);
 901
 902         return ret;
 903 }
 904
 905 static int
 906 kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
 907 {
 908         enum kvm_bus              bus_idx;
 909         int ret;
 910
 911         bus_idx = ioeventfd_bus_from_flags(args->flags);
 912         /* must be natural-word sized, or 0 to ignore length */
 913         switch (args->len) {
 914         case 0:
 915         case 1:
 916         case 2:
 917         case 4:
 918         case 8:
 919                 break;
 920         default:
 921                 return -EINVAL;
 922         }
 923
 924         /* check for range overflow */
 925         if (args->addr + args->len < args->addr)
 926                 return -EINVAL;
 927
 928         /* check for extra flags that we don't understand */
 929         if (args->flags & ~KVM_IOEVENTFD_VALID_FLAG_MASK)
 930                 return -EINVAL;
 931
 932         /* ioeventfd with no length can't be combined with DATAMATCH */
 933         if (!args->len && (args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH))
 934                 return -EINVAL;
 935
 936         ret = kvm_assign_ioeventfd_idx(kvm, bus_idx, args);
 937         if (ret)
 938                 goto fail;
 939
 940         /* When length is ignored, MMIO is also put on a separate bus, for
 941          * faster lookups.
 942          */
 943         if (!args->len && bus_idx == KVM_MMIO_BUS) {
 944                 ret = kvm_assign_ioeventfd_idx(kvm, KVM_FAST_MMIO_BUS, args);
 945                 if (ret < 0)
 946                         goto fast_fail;
 947         }
 948
 949         return 0;
 950
 951 fast_fail:
 952         kvm_deassign_ioeventfd_idx(kvm, bus_idx, args);
 953 fail:
 954         return ret;
 955 }
 956
 957 int
 958 kvm_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
 959 {
 960         if (args->flags & KVM_IOEVENTFD_FLAG_DEASSIGN)
 961                 return kvm_deassign_ioeventfd(kvm, args);
 962
 963         return kvm_assign_ioeventfd(kvm, args);
 964 }