virt/kvm/eventfd.c

   1 /*
   2  * kvm eventfd support - use eventfd objects to signal various KVM events
   3  *
   4  * Copyright 2009 Novell.  All Rights Reserved.
   5  * Copyright 2010 Red Hat, Inc. and/or its affiliates.
   6  *
   7  * Author:
   8  *      Gregory Haskins <ghaskins@novell.com>
   9  *
  10  * This file is free software; you can redistribute it and/or modify
  11  * it under the terms of version 2 of the GNU General Public License
  12  * as published by the Free Software Foundation.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  * GNU General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU General Public License
  20  * along with this program; if not, write to the Free Software Foundation,
  21  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
  22  */
  23
  24 #include <linux/kvm_host.h>
  25 #include <linux/kvm.h>
  26 #include <linux/workqueue.h>
  27 #include <linux/syscalls.h>
  28 #include <linux/wait.h>
  29 #include <linux/poll.h>
  30 #include <linux/file.h>
  31 #include <linux/list.h>
  32 #include <linux/eventfd.h>
  33 #include <linux/kernel.h>
  34 #include <linux/slab.h>
  35
  36 #include "iodev.h"
  37
  38 /*
  39  * --------------------------------------------------------------------
  40  * irqfd: Allows an fd to be used to inject an interrupt to the guest
  41  *
  42  * Credit goes to Avi Kivity for the original idea.
  43  * --------------------------------------------------------------------
  44  */
  45
  46 /*
  47  * Resampling irqfds are a special variety of irqfds used to emulate
  48  * level triggered interrupts.  The interrupt is asserted on eventfd
  49  * trigger.  On acknowledgement through the irq ack notifier, the
  50  * interrupt is de-asserted and userspace is notified through the
  51  * resamplefd.  All resamplers on the same gsi are de-asserted
  52  * together, so we don't need to track the state of each individual
  53  * user.  We can also therefore share the same irq source ID.
  54  */
  55 struct _irqfd_resampler {
  56         struct kvm *kvm;
  57         /*
  58          * List of resampling struct _irqfd objects sharing this gsi.
  59          * RCU list modified under kvm->irqfds.resampler_lock
  60          */
  61         struct list_head list;
  62         struct kvm_irq_ack_notifier notifier;
  63         /*
  64          * Entry in list of kvm->irqfd.resampler_list.  Use for sharing
  65          * resamplers among irqfds on the same gsi.
  66          * Accessed and modified under kvm->irqfds.resampler_lock
  67          */
  68         struct list_head link;
  69 };
  70
  71 struct _irqfd {
  72         /* Used for MSI fast-path */
  73         struct kvm *kvm;
  74         wait_queue_t wait;
  75         /* Update side is protected by irqfds.lock */
  76         struct kvm_kernel_irq_routing_entry __rcu *irq_entry;
  77         /* Used for level IRQ fast-path */
  78         int gsi;
  79         struct work_struct inject;
  80         /* The resampler used by this irqfd (resampler-only) */
  81         struct _irqfd_resampler *resampler;
  82         /* Eventfd notified on resample (resampler-only) */
  83         struct eventfd_ctx *resamplefd;
  84         /* Entry in list of irqfds for a resampler (resampler-only) */
  85         struct list_head resampler_link;
  86         /* Used for setup/shutdown */
  87         struct eventfd_ctx *eventfd;
  88         struct list_head list;
  89         poll_table pt;
  90         struct work_struct shutdown;
  91 };
  92
  93 static struct workqueue_struct *irqfd_cleanup_wq;
  94
  95 static void
  96 irqfd_inject(struct work_struct *work)
  97 {
  98         struct _irqfd *irqfd = container_of(work, struct _irqfd, inject);
  99         struct kvm *kvm = irqfd->kvm;
 100
 101         if (!irqfd->resampler) {
 102                 kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 1);
 103                 kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 0);
 104         } else
 105                 kvm_set_irq(kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
 106                             irqfd->gsi, 1);
 107 }
 108
 109 /*
 110  * Since resampler irqfds share an IRQ source ID, we de-assert once
 111  * then notify all of the resampler irqfds using this GSI.  We can't
 112  * do multiple de-asserts or we risk racing with incoming re-asserts.
 113  */
 114 static void
 115 irqfd_resampler_ack(struct kvm_irq_ack_notifier *kian)
 116 {
 117         struct _irqfd_resampler *resampler;
 118         struct _irqfd *irqfd;
 119
 120         resampler = container_of(kian, struct _irqfd_resampler, notifier);
 121
 122         kvm_set_irq(resampler->kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
 123                     resampler->notifier.gsi, 0);
 124
 125         rcu_read_lock();
 126
 127         list_for_each_entry_rcu(irqfd, &resampler->list, resampler_link)
 128                 eventfd_signal(irqfd->resamplefd, 1);
 129
 130         rcu_read_unlock();
 131 }
 132
 133 static void
 134 irqfd_resampler_shutdown(struct _irqfd *irqfd)
 135 {
 136         struct _irqfd_resampler *resampler = irqfd->resampler;
 137         struct kvm *kvm = resampler->kvm;
 138
 139         mutex_lock(&kvm->irqfds.resampler_lock);
 140
 141         list_del_rcu(&irqfd->resampler_link);
 142         synchronize_rcu();
 143
 144         if (list_empty(&resampler->list)) {
 145                 list_del(&resampler->link);
 146                 kvm_unregister_irq_ack_notifier(kvm, &resampler->notifier);
 147                 kvm_set_irq(kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
 148                             resampler->notifier.gsi, 0);
 149                 kfree(resampler);
 150         }
 151
 152         mutex_unlock(&kvm->irqfds.resampler_lock);
 153 }
 154
 155 /*
 156  * Race-free decouple logic (ordering is critical)
 157  */
 158 static void
 159 irqfd_shutdown(struct work_struct *work)
 160 {
 161         struct _irqfd *irqfd = container_of(work, struct _irqfd, shutdown);
 162         u64 cnt;
 163
 164         /*
 165          * Synchronize with the wait-queue and unhook ourselves to prevent
 166          * further events.
 167          */
 168         eventfd_ctx_remove_wait_queue(irqfd->eventfd, &irqfd->wait, &cnt);
 169
 170         /*
 171          * We know no new events will be scheduled at this point, so block
 172          * until all previously outstanding events have completed
 173          */
 174         flush_work(&irqfd->inject);
 175
 176         if (irqfd->resampler) {
 177                 irqfd_resampler_shutdown(irqfd);
 178                 eventfd_ctx_put(irqfd->resamplefd);
 179         }
 180
 181         /*
 182          * It is now safe to release the object's resources
 183          */
 184         eventfd_ctx_put(irqfd->eventfd);
 185         kfree(irqfd);
 186 }
 187
 188
 189 /* assumes kvm->irqfds.lock is held */
 190 static bool
 191 irqfd_is_active(struct _irqfd *irqfd)
 192 {
 193         return list_empty(&irqfd->list) ? false : true;
 194 }
 195
 196 /*
 197  * Mark the irqfd as inactive and schedule it for removal
 198  *
 199  * assumes kvm->irqfds.lock is held
 200  */
 201 static void
 202 irqfd_deactivate(struct _irqfd *irqfd)
 203 {
 204         BUG_ON(!irqfd_is_active(irqfd));
 205
 206         list_del_init(&irqfd->list);
 207
 208         queue_work(irqfd_cleanup_wq, &irqfd->shutdown);
 209 }
 210
 211 /*
 212  * Called with wqh->lock held and interrupts disabled
 213  */
 214 static int
 215 irqfd_wakeup(wait_queue_t *wait, unsigned mode, int sync, void *key)
 216 {
 217         struct _irqfd *irqfd = container_of(wait, struct _irqfd, wait);
 218         unsigned long flags = (unsigned long)key;
 219         struct kvm_kernel_irq_routing_entry *irq;
 220         struct kvm *kvm = irqfd->kvm;
 221
 222         if (flags & POLLIN) {
 223                 rcu_read_lock();
 224                 irq = rcu_dereference(irqfd->irq_entry);
 225                 /* An event has been signaled, inject an interrupt */
 226                 if (irq)
 227                         kvm_set_msi(irq, kvm, KVM_USERSPACE_IRQ_SOURCE_ID, 1);
 228                 else
 229                         schedule_work(&irqfd->inject);
 230                 rcu_read_unlock();
 231         }
 232
 233         if (flags & POLLHUP) {
 234                 /* The eventfd is closing, detach from KVM */
 235                 unsigned long flags;
 236
 237                 spin_lock_irqsave(&kvm->irqfds.lock, flags);
 238
 239                 /*
 240                  * We must check if someone deactivated the irqfd before
 241                  * we could acquire the irqfds.lock since the item is
 242                  * deactivated from the KVM side before it is unhooked from
 243                  * the wait-queue.  If it is already deactivated, we can
 244                  * simply return knowing the other side will cleanup for us.
 245                  * We cannot race against the irqfd going away since the
 246                  * other side is required to acquire wqh->lock, which we hold
 247                  */
 248                 if (irqfd_is_active(irqfd))
 249                         irqfd_deactivate(irqfd);
 250
 251                 spin_unlock_irqrestore(&kvm->irqfds.lock, flags);
 252         }
 253
 254         return 0;
 255 }
 256
 257 static void
 258 irqfd_ptable_queue_proc(struct file *file, wait_queue_head_t *wqh,
 259                         poll_table *pt)
 260 {
 261         struct _irqfd *irqfd = container_of(pt, struct _irqfd, pt);
 262         add_wait_queue(wqh, &irqfd->wait);
 263 }
 264
 265 /* Must be called under irqfds.lock */
 266 static void irqfd_update(struct kvm *kvm, struct _irqfd *irqfd,
 267                          struct kvm_irq_routing_table *irq_rt)
 268 {
 269         struct kvm_kernel_irq_routing_entry *e;
 270         struct hlist_node *n;
 271
 272         if (irqfd->gsi >= irq_rt->nr_rt_entries) {
 273                 rcu_assign_pointer(irqfd->irq_entry, NULL);
 274                 return;
 275         }
 276
 277         hlist_for_each_entry(e, n, &irq_rt->map[irqfd->gsi], link) {
 278                 /* Only fast-path MSI. */
 279                 if (e->type == KVM_IRQ_ROUTING_MSI)
 280                         rcu_assign_pointer(irqfd->irq_entry, e);
 281                 else
 282                         rcu_assign_pointer(irqfd->irq_entry, NULL);
 283         }
 284 }
 285
 286 static int
 287 kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args)
 288 {
 289         struct kvm_irq_routing_table *irq_rt;
 290         struct _irqfd *irqfd, *tmp;
 291         struct file *file = NULL;
 292         struct eventfd_ctx *eventfd = NULL, *resamplefd = NULL;
 293         int ret;
 294         unsigned int events;
 295
 296         irqfd = kzalloc(sizeof(*irqfd), GFP_KERNEL);
 297         if (!irqfd)
 298                 return -ENOMEM;
 299
 300         irqfd->kvm = kvm;
 301         irqfd->gsi = args->gsi;
 302         INIT_LIST_HEAD(&irqfd->list);
 303         INIT_WORK(&irqfd->inject, irqfd_inject);
 304         INIT_WORK(&irqfd->shutdown, irqfd_shutdown);
 305
 306         file = eventfd_fget(args->fd);
 307         if (IS_ERR(file)) {
 308                 ret = PTR_ERR(file);
 309                 goto fail;
 310         }
 311
 312         eventfd = eventfd_ctx_fileget(file);
 313         if (IS_ERR(eventfd)) {
 314                 ret = PTR_ERR(eventfd);
 315                 goto fail;
 316         }
 317
 318         irqfd->eventfd = eventfd;
 319
 320         if (args->flags & KVM_IRQFD_FLAG_RESAMPLE) {
 321                 struct _irqfd_resampler *resampler;
 322
 323                 resamplefd = eventfd_ctx_fdget(args->resamplefd);
 324                 if (IS_ERR(resamplefd)) {
 325                         ret = PTR_ERR(resamplefd);
 326                         goto fail;
 327                 }
 328
 329                 irqfd->resamplefd = resamplefd;
 330                 INIT_LIST_HEAD(&irqfd->resampler_link);
 331
 332                 mutex_lock(&kvm->irqfds.resampler_lock);
 333
 334                 list_for_each_entry(resampler,
 335                                     &kvm->irqfds.resampler_list, list) {
 336                         if (resampler->notifier.gsi == irqfd->gsi) {
 337                                 irqfd->resampler = resampler;
 338                                 break;
 339                         }
 340                 }
 341
 342                 if (!irqfd->resampler) {
 343                         resampler = kzalloc(sizeof(*resampler), GFP_KERNEL);
 344                         if (!resampler) {
 345                                 ret = -ENOMEM;
 346                                 mutex_unlock(&kvm->irqfds.resampler_lock);
 347                                 goto fail;
 348                         }
 349
 350                         resampler->kvm = kvm;
 351                         INIT_LIST_HEAD(&resampler->list);
 352                         resampler->notifier.gsi = irqfd->gsi;
 353                         resampler->notifier.irq_acked = irqfd_resampler_ack;
 354                         INIT_LIST_HEAD(&resampler->link);
 355
 356                         list_add(&resampler->link, &kvm->irqfds.resampler_list);
 357                         kvm_register_irq_ack_notifier(kvm,
 358                                                       &resampler->notifier);
 359                         irqfd->resampler = resampler;
 360                 }
 361
 362                 list_add_rcu(&irqfd->resampler_link, &irqfd->resampler->list);
 363                 synchronize_rcu();
 364
 365                 mutex_unlock(&kvm->irqfds.resampler_lock);
 366         }
 367
 368         /*
 369          * Install our own custom wake-up handling so we are notified via
 370          * a callback whenever someone signals the underlying eventfd
 371          */
 372         init_waitqueue_func_entry(&irqfd->wait, irqfd_wakeup);
 373         init_poll_funcptr(&irqfd->pt, irqfd_ptable_queue_proc);
 374
 375         spin_lock_irq(&kvm->irqfds.lock);
 376
 377         ret = 0;
 378         list_for_each_entry(tmp, &kvm->irqfds.items, list) {
 379                 if (irqfd->eventfd != tmp->eventfd)
 380                         continue;
 381                 /* This fd is used for another irq already. */
 382                 ret = -EBUSY;
 383                 spin_unlock_irq(&kvm->irqfds.lock);
 384                 goto fail;
 385         }
 386
 387         irq_rt = rcu_dereference_protected(kvm->irq_routing,
 388                                            lockdep_is_held(&kvm->irqfds.lock));
 389         irqfd_update(kvm, irqfd, irq_rt);
 390
 391         events = file->f_op->poll(file, &irqfd->pt);
 392
 393         list_add_tail(&irqfd->list, &kvm->irqfds.items);
 394
 395         /*
 396          * Check if there was an event already pending on the eventfd
 397          * before we registered, and trigger it as if we didn't miss it.
 398          */
 399         if (events & POLLIN)
 400                 schedule_work(&irqfd->inject);
 401
 402         spin_unlock_irq(&kvm->irqfds.lock);
 403
 404         /*
 405          * do not drop the file until the irqfd is fully initialized, otherwise
 406          * we might race against the POLLHUP
 407          */
 408         fput(file);
 409
 410         return 0;
 411
 412 fail:
 413         if (irqfd->resampler)
 414                 irqfd_resampler_shutdown(irqfd);
 415
 416         if (resamplefd && !IS_ERR(resamplefd))
 417                 eventfd_ctx_put(resamplefd);
 418
 419         if (eventfd && !IS_ERR(eventfd))
 420                 eventfd_ctx_put(eventfd);
 421
 422         if (!IS_ERR(file))
 423                 fput(file);
 424
 425         kfree(irqfd);
 426         return ret;
 427 }
 428
 429 void
 430 kvm_eventfd_init(struct kvm *kvm)
 431 {
 432         spin_lock_init(&kvm->irqfds.lock);
 433         INIT_LIST_HEAD(&kvm->irqfds.items);
 434         INIT_LIST_HEAD(&kvm->irqfds.resampler_list);
 435         mutex_init(&kvm->irqfds.resampler_lock);
 436         INIT_LIST_HEAD(&kvm->ioeventfds);
 437 }
 438
 439 /*
 440  * shutdown any irqfd's that match fd+gsi
 441  */
 442 static int
 443 kvm_irqfd_deassign(struct kvm *kvm, struct kvm_irqfd *args)
 444 {
 445         struct _irqfd *irqfd, *tmp;
 446         struct eventfd_ctx *eventfd;
 447
 448         eventfd = eventfd_ctx_fdget(args->fd);
 449         if (IS_ERR(eventfd))
 450                 return PTR_ERR(eventfd);
 451
 452         spin_lock_irq(&kvm->irqfds.lock);
 453
 454         list_for_each_entry_safe(irqfd, tmp, &kvm->irqfds.items, list) {
 455                 if (irqfd->eventfd == eventfd && irqfd->gsi == args->gsi) {
 456                         /*
 457                          * This rcu_assign_pointer is needed for when
 458                          * another thread calls kvm_irq_routing_update before
 459                          * we flush workqueue below (we synchronize with
 460                          * kvm_irq_routing_update using irqfds.lock).
 461                          * It is paired with synchronize_rcu done by caller
 462                          * of that function.
 463                          */
 464                         rcu_assign_pointer(irqfd->irq_entry, NULL);
 465                         irqfd_deactivate(irqfd);
 466                 }
 467         }
 468
 469         spin_unlock_irq(&kvm->irqfds.lock);
 470         eventfd_ctx_put(eventfd);
 471
 472         /*
 473          * Block until we know all outstanding shutdown jobs have completed
 474          * so that we guarantee there will not be any more interrupts on this
 475          * gsi once this deassign function returns.
 476          */
 477         flush_workqueue(irqfd_cleanup_wq);
 478
 479         return 0;
 480 }
 481
 482 int
 483 kvm_irqfd(struct kvm *kvm, struct kvm_irqfd *args)
 484 {
 485         if (args->flags & ~(KVM_IRQFD_FLAG_DEASSIGN | KVM_IRQFD_FLAG_RESAMPLE))
 486                 return -EINVAL;
 487
 488         if (args->flags & KVM_IRQFD_FLAG_DEASSIGN)
 489                 return kvm_irqfd_deassign(kvm, args);
 490
 491         return kvm_irqfd_assign(kvm, args);
 492 }
 493
 494 /*
 495  * This function is called as the kvm VM fd is being released. Shutdown all
 496  * irqfds that still remain open
 497  */
 498 void
 499 kvm_irqfd_release(struct kvm *kvm)
 500 {
 501         struct _irqfd *irqfd, *tmp;
 502
 503         spin_lock_irq(&kvm->irqfds.lock);
 504
 505         list_for_each_entry_safe(irqfd, tmp, &kvm->irqfds.items, list)
 506                 irqfd_deactivate(irqfd);
 507
 508         spin_unlock_irq(&kvm->irqfds.lock);
 509
 510         /*
 511          * Block until we know all outstanding shutdown jobs have completed
 512          * since we do not take a kvm* reference.
 513          */
 514         flush_workqueue(irqfd_cleanup_wq);
 515
 516 }
 517
 518 /*
 519  * Change irq_routing and irqfd.
 520  * Caller must invoke synchronize_rcu afterwards.
 521  */
 522 void kvm_irq_routing_update(struct kvm *kvm,
 523                             struct kvm_irq_routing_table *irq_rt)
 524 {
 525         struct _irqfd *irqfd;
 526
 527         spin_lock_irq(&kvm->irqfds.lock);
 528
 529         rcu_assign_pointer(kvm->irq_routing, irq_rt);
 530
 531         list_for_each_entry(irqfd, &kvm->irqfds.items, list)
 532                 irqfd_update(kvm, irqfd, irq_rt);
 533
 534         spin_unlock_irq(&kvm->irqfds.lock);
 535 }
 536
 537 /*
 538  * create a host-wide workqueue for issuing deferred shutdown requests
 539  * aggregated from all vm* instances. We need our own isolated single-thread
 540  * queue to prevent deadlock against flushing the normal work-queue.
 541  */
 542 static int __init irqfd_module_init(void)
 543 {
 544         irqfd_cleanup_wq = create_singlethread_workqueue("kvm-irqfd-cleanup");
 545         if (!irqfd_cleanup_wq)
 546                 return -ENOMEM;
 547
 548         return 0;
 549 }
 550
 551 static void __exit irqfd_module_exit(void)
 552 {
 553         destroy_workqueue(irqfd_cleanup_wq);
 554 }
 555
 556 module_init(irqfd_module_init);
 557 module_exit(irqfd_module_exit);
 558
 559 /*
 560  * --------------------------------------------------------------------
 561  * ioeventfd: translate a PIO/MMIO memory write to an eventfd signal.
 562  *
 563  * userspace can register a PIO/MMIO address with an eventfd for receiving
 564  * notification when the memory has been touched.
 565  * --------------------------------------------------------------------
 566  */
 567
 568 struct _ioeventfd {
 569         struct list_head     list;
 570         u64                  addr;
 571         int                  length;
 572         struct eventfd_ctx  *eventfd;
 573         u64                  datamatch;
 574         struct kvm_io_device dev;
 575         bool                 wildcard;
 576 };
 577
 578 static inline struct _ioeventfd *
 579 to_ioeventfd(struct kvm_io_device *dev)
 580 {
 581         return container_of(dev, struct _ioeventfd, dev);
 582 }
 583
 584 static void
 585 ioeventfd_release(struct _ioeventfd *p)
 586 {
 587         eventfd_ctx_put(p->eventfd);
 588         list_del(&p->list);
 589         kfree(p);
 590 }
 591
 592 static bool
 593 ioeventfd_in_range(struct _ioeventfd *p, gpa_t addr, int len, const void *val)
 594 {
 595         u64 _val;
 596
 597         if (!(addr == p->addr && len == p->length))
 598                 /* address-range must be precise for a hit */
 599                 return false;
 600
 601         if (p->wildcard)
 602                 /* all else equal, wildcard is always a hit */
 603                 return true;
 604
 605         /* otherwise, we have to actually compare the data */
 606
 607         BUG_ON(!IS_ALIGNED((unsigned long)val, len));
 608
 609         switch (len) {
 610         case 1:
 611                 _val = *(u8 *)val;
 612                 break;
 613         case 2:
 614                 _val = *(u16 *)val;
 615                 break;
 616         case 4:
 617                 _val = *(u32 *)val;
 618                 break;
 619         case 8:
 620                 _val = *(u64 *)val;
 621                 break;
 622         default:
 623                 return false;
 624         }
 625
 626         return _val == p->datamatch ? true : false;
 627 }
 628
 629 /* MMIO/PIO writes trigger an event if the addr/val match */
 630 static int
 631 ioeventfd_write(struct kvm_io_device *this, gpa_t addr, int len,
 632                 const void *val)
 633 {
 634         struct _ioeventfd *p = to_ioeventfd(this);
 635
 636         if (!ioeventfd_in_range(p, addr, len, val))
 637                 return -EOPNOTSUPP;
 638
 639         eventfd_signal(p->eventfd, 1);
 640         return 0;
 641 }
 642
 643 /*
 644  * This function is called as KVM is completely shutting down.  We do not
 645  * need to worry about locking just nuke anything we have as quickly as possible
 646  */
 647 static void
 648 ioeventfd_destructor(struct kvm_io_device *this)
 649 {
 650         struct _ioeventfd *p = to_ioeventfd(this);
 651
 652         ioeventfd_release(p);
 653 }
 654
 655 static const struct kvm_io_device_ops ioeventfd_ops = {
 656         .write      = ioeventfd_write,
 657         .destructor = ioeventfd_destructor,
 658 };
 659
 660 /* assumes kvm->slots_lock held */
 661 static bool
 662 ioeventfd_check_collision(struct kvm *kvm, struct _ioeventfd *p)
 663 {
 664         struct _ioeventfd *_p;
 665
 666         list_for_each_entry(_p, &kvm->ioeventfds, list)
 667                 if (_p->addr == p->addr && _p->length == p->length &&
 668                     (_p->wildcard || p->wildcard ||
 669                      _p->datamatch == p->datamatch))
 670                         return true;
 671
 672         return false;
 673 }
 674
 675 static int
 676 kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
 677 {
 678         int                       pio = args->flags & KVM_IOEVENTFD_FLAG_PIO;
 679         enum kvm_bus              bus_idx = pio ? KVM_PIO_BUS : KVM_MMIO_BUS;
 680         struct _ioeventfd        *p;
 681         struct eventfd_ctx       *eventfd;
 682         int                       ret;
 683
 684         /* must be natural-word sized */
 685         switch (args->len) {
 686         case 1:
 687         case 2:
 688         case 4:
 689         case 8:
 690                 break;
 691         default:
 692                 return -EINVAL;
 693         }
 694
 695         /* check for range overflow */
 696         if (args->addr + args->len < args->addr)
 697                 return -EINVAL;
 698
 699         /* check for extra flags that we don't understand */
 700         if (args->flags & ~KVM_IOEVENTFD_VALID_FLAG_MASK)
 701                 return -EINVAL;
 702
 703         eventfd = eventfd_ctx_fdget(args->fd);
 704         if (IS_ERR(eventfd))
 705                 return PTR_ERR(eventfd);
 706
 707         p = kzalloc(sizeof(*p), GFP_KERNEL);
 708         if (!p) {
 709                 ret = -ENOMEM;
 710                 goto fail;
 711         }
 712
 713         INIT_LIST_HEAD(&p->list);
 714         p->addr    = args->addr;
 715         p->length  = args->len;
 716         p->eventfd = eventfd;
 717
 718         /* The datamatch feature is optional, otherwise this is a wildcard */
 719         if (args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH)
 720                 p->datamatch = args->datamatch;
 721         else
 722                 p->wildcard = true;
 723
 724         mutex_lock(&kvm->slots_lock);
 725
 726         /* Verify that there isn't a match already */
 727         if (ioeventfd_check_collision(kvm, p)) {
 728                 ret = -EEXIST;
 729                 goto unlock_fail;
 730         }
 731
 732         kvm_iodevice_init(&p->dev, &ioeventfd_ops);
 733
 734         ret = kvm_io_bus_register_dev(kvm, bus_idx, p->addr, p->length,
 735                                       &p->dev);
 736         if (ret < 0)
 737                 goto unlock_fail;
 738
 739         list_add_tail(&p->list, &kvm->ioeventfds);
 740
 741         mutex_unlock(&kvm->slots_lock);
 742
 743         return 0;
 744
 745 unlock_fail:
 746         mutex_unlock(&kvm->slots_lock);
 747
 748 fail:
 749         kfree(p);
 750         eventfd_ctx_put(eventfd);
 751
 752         return ret;
 753 }
 754
 755 static int
 756 kvm_deassign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
 757 {
 758         int                       pio = args->flags & KVM_IOEVENTFD_FLAG_PIO;
 759         enum kvm_bus              bus_idx = pio ? KVM_PIO_BUS : KVM_MMIO_BUS;
 760         struct _ioeventfd        *p, *tmp;
 761         struct eventfd_ctx       *eventfd;
 762         int                       ret = -ENOENT;
 763
 764         eventfd = eventfd_ctx_fdget(args->fd);
 765         if (IS_ERR(eventfd))
 766                 return PTR_ERR(eventfd);
 767
 768         mutex_lock(&kvm->slots_lock);
 769
 770         list_for_each_entry_safe(p, tmp, &kvm->ioeventfds, list) {
 771                 bool wildcard = !(args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH);
 772
 773                 if (p->eventfd != eventfd  ||
 774                     p->addr != args->addr  ||
 775                     p->length != args->len ||
 776                     p->wildcard != wildcard)
 777                         continue;
 778
 779                 if (!p->wildcard && p->datamatch != args->datamatch)
 780                         continue;
 781
 782                 kvm_io_bus_unregister_dev(kvm, bus_idx, &p->dev);
 783                 ioeventfd_release(p);
 784                 ret = 0;
 785                 break;
 786         }
 787
 788         mutex_unlock(&kvm->slots_lock);
 789
 790         eventfd_ctx_put(eventfd);
 791
 792         return ret;
 793 }
 794
 795 int
 796 kvm_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
 797 {
 798         if (args->flags & KVM_IOEVENTFD_FLAG_DEASSIGN)
 799                 return kvm_deassign_ioeventfd(kvm, args);
 800
 801         return kvm_assign_ioeventfd(kvm, args);
 802 }