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 #ifdef __KVM_HAVE_IOAPIC
  39 /*
  40  * --------------------------------------------------------------------
  41  * irqfd: Allows an fd to be used to inject an interrupt to the guest
  42  *
  43  * Credit goes to Avi Kivity for the original idea.
  44  * --------------------------------------------------------------------
  45  */
  46
  47 /*
  48  * Resampling irqfds are a special variety of irqfds used to emulate
  49  * level triggered interrupts.  The interrupt is asserted on eventfd
  50  * trigger.  On acknowledgement through the irq ack notifier, the
  51  * interrupt is de-asserted and userspace is notified through the
  52  * resamplefd.  All resamplers on the same gsi are de-asserted
  53  * together, so we don't need to track the state of each individual
  54  * user.  We can also therefore share the same irq source ID.
  55  */
  56 struct _irqfd_resampler {
  57         struct kvm *kvm;
  58         /*
  59          * List of resampling struct _irqfd objects sharing this gsi.
  60          * RCU list modified under kvm->irqfds.resampler_lock
  61          */
  62         struct list_head list;
  63         struct kvm_irq_ack_notifier notifier;
  64         /*
  65          * Entry in list of kvm->irqfd.resampler_list.  Use for sharing
  66          * resamplers among irqfds on the same gsi.
  67          * Accessed and modified under kvm->irqfds.resampler_lock
  68          */
  69         struct list_head link;
  70 };
  71
  72 struct _irqfd {
  73         /* Used for MSI fast-path */
  74         struct kvm *kvm;
  75         wait_queue_t wait;
  76         /* Update side is protected by irqfds.lock */
  77         struct kvm_kernel_irq_routing_entry __rcu *irq_entry;
  78         /* Used for level IRQ fast-path */
  79         int gsi;
  80         struct work_struct inject;
  81         /* The resampler used by this irqfd (resampler-only) */
  82         struct _irqfd_resampler *resampler;
  83         /* Eventfd notified on resample (resampler-only) */
  84         struct eventfd_ctx *resamplefd;
  85         /* Entry in list of irqfds for a resampler (resampler-only) */
  86         struct list_head resampler_link;
  87         /* Used for setup/shutdown */
  88         struct eventfd_ctx *eventfd;
  89         struct list_head list;
  90         poll_table pt;
  91         struct work_struct shutdown;
  92 };
  93
  94 static struct workqueue_struct *irqfd_cleanup_wq;
  95
  96 static void
  97 irqfd_inject(struct work_struct *work)
  98 {
  99         struct _irqfd *irqfd = container_of(work, struct _irqfd, inject);
 100         struct kvm *kvm = irqfd->kvm;
 101
 102         if (!irqfd->resampler) {
 103                 kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 1);
 104                 kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 0);
 105         } else
 106                 kvm_set_irq(kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
 107                             irqfd->gsi, 1);
 108 }
 109
 110 /*
 111  * Since resampler irqfds share an IRQ source ID, we de-assert once
 112  * then notify all of the resampler irqfds using this GSI.  We can't
 113  * do multiple de-asserts or we risk racing with incoming re-asserts.
 114  */
 115 static void
 116 irqfd_resampler_ack(struct kvm_irq_ack_notifier *kian)
 117 {
 118         struct _irqfd_resampler *resampler;
 119         struct _irqfd *irqfd;
 120
 121         resampler = container_of(kian, struct _irqfd_resampler, notifier);
 122
 123         kvm_set_irq(resampler->kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
 124                     resampler->notifier.gsi, 0);
 125
 126         rcu_read_lock();
 127
 128         list_for_each_entry_rcu(irqfd, &resampler->list, resampler_link)
 129                 eventfd_signal(irqfd->resamplefd, 1);
 130
 131         rcu_read_unlock();
 132 }
 133
 134 static void
 135 irqfd_resampler_shutdown(struct _irqfd *irqfd)
 136 {
 137         struct _irqfd_resampler *resampler = irqfd->resampler;
 138         struct kvm *kvm = resampler->kvm;
 139
 140         mutex_lock(&kvm->irqfds.resampler_lock);
 141
 142         list_del_rcu(&irqfd->resampler_link);
 143         synchronize_rcu();
 144
 145         if (list_empty(&resampler->list)) {
 146                 list_del(&resampler->link);
 147                 kvm_unregister_irq_ack_notifier(kvm, &resampler->notifier);
 148                 kvm_set_irq(kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
 149                             resampler->notifier.gsi, 0);
 150                 kfree(resampler);
 151         }
 152
 153         mutex_unlock(&kvm->irqfds.resampler_lock);
 154 }
 155
 156 /*
 157  * Race-free decouple logic (ordering is critical)
 158  */
 159 static void
 160 irqfd_shutdown(struct work_struct *work)
 161 {
 162         struct _irqfd *irqfd = container_of(work, struct _irqfd, shutdown);
 163         u64 cnt;
 164
 165         /*
 166          * Synchronize with the wait-queue and unhook ourselves to prevent
 167          * further events.
 168          */
 169         eventfd_ctx_remove_wait_queue(irqfd->eventfd, &irqfd->wait, &cnt);
 170
 171         /*
 172          * We know no new events will be scheduled at this point, so block
 173          * until all previously outstanding events have completed
 174          */
 175         flush_work(&irqfd->inject);
 176
 177         if (irqfd->resampler) {
 178                 irqfd_resampler_shutdown(irqfd);
 179                 eventfd_ctx_put(irqfd->resamplefd);
 180         }
 181
 182         /*
 183          * It is now safe to release the object's resources
 184          */
 185         eventfd_ctx_put(irqfd->eventfd);
 186         kfree(irqfd);
 187 }
 188
 189
 190 /* assumes kvm->irqfds.lock is held */
 191 static bool
 192 irqfd_is_active(struct _irqfd *irqfd)
 193 {
 194         return list_empty(&irqfd->list) ? false : true;
 195 }
 196
 197 /*
 198  * Mark the irqfd as inactive and schedule it for removal
 199  *
 200  * assumes kvm->irqfds.lock is held
 201  */
 202 static void
 203 irqfd_deactivate(struct _irqfd *irqfd)
 204 {
 205         BUG_ON(!irqfd_is_active(irqfd));
 206
 207         list_del_init(&irqfd->list);
 208
 209         queue_work(irqfd_cleanup_wq, &irqfd->shutdown);
 210 }
 211
 212 /*
 213  * Called with wqh->lock held and interrupts disabled
 214  */
 215 static int
 216 irqfd_wakeup(wait_queue_t *wait, unsigned mode, int sync, void *key)
 217 {
 218         struct _irqfd *irqfd = container_of(wait, struct _irqfd, wait);
 219         unsigned long flags = (unsigned long)key;
 220         struct kvm_kernel_irq_routing_entry *irq;
 221         struct kvm *kvm = irqfd->kvm;
 222
 223         if (flags & POLLIN) {
 224                 rcu_read_lock();
 225                 irq = rcu_dereference(irqfd->irq_entry);
 226                 /* An event has been signaled, inject an interrupt */
 227                 if (irq)
 228                         kvm_set_msi(irq, kvm, KVM_USERSPACE_IRQ_SOURCE_ID, 1);
 229                 else
 230                         schedule_work(&irqfd->inject);
 231                 rcu_read_unlock();
 232         }
 233
 234         if (flags & POLLHUP) {
 235                 /* The eventfd is closing, detach from KVM */
 236                 unsigned long flags;
 237
 238                 spin_lock_irqsave(&kvm->irqfds.lock, flags);
 239
 240                 /*
 241                  * We must check if someone deactivated the irqfd before
 242                  * we could acquire the irqfds.lock since the item is
 243                  * deactivated from the KVM side before it is unhooked from
 244                  * the wait-queue.  If it is already deactivated, we can
 245                  * simply return knowing the other side will cleanup for us.
 246                  * We cannot race against the irqfd going away since the
 247                  * other side is required to acquire wqh->lock, which we hold
 248                  */
 249                 if (irqfd_is_active(irqfd))
 250                         irqfd_deactivate(irqfd);
 251
 252                 spin_unlock_irqrestore(&kvm->irqfds.lock, flags);
 253         }
 254
 255         return 0;
 256 }
 257
 258 static void
 259 irqfd_ptable_queue_proc(struct file *file, wait_queue_head_t *wqh,
 260                         poll_table *pt)
 261 {
 262         struct _irqfd *irqfd = container_of(pt, struct _irqfd, pt);
 263         add_wait_queue(wqh, &irqfd->wait);
 264 }
 265
 266 /* Must be called under irqfds.lock */
 267 static void irqfd_update(struct kvm *kvm, struct _irqfd *irqfd,
 268                          struct kvm_irq_routing_table *irq_rt)
 269 {
 270         struct kvm_kernel_irq_routing_entry *e;
 271         struct hlist_node *n;
 272
 273         if (irqfd->gsi >= irq_rt->nr_rt_entries) {
 274                 rcu_assign_pointer(irqfd->irq_entry, NULL);
 275                 return;
 276         }
 277
 278         hlist_for_each_entry(e, n, &irq_rt->map[irqfd->gsi], link) {
 279                 /* Only fast-path MSI. */
 280                 if (e->type == KVM_IRQ_ROUTING_MSI)
 281                         rcu_assign_pointer(irqfd->irq_entry, e);
 282                 else
 283                         rcu_assign_pointer(irqfd->irq_entry, NULL);
 284         }
 285 }
 286
 287 static int
 288 kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args)
 289 {
 290         struct kvm_irq_routing_table *irq_rt;
 291         struct _irqfd *irqfd, *tmp;
 292         struct file *file = NULL;
 293         struct eventfd_ctx *eventfd = NULL, *resamplefd = NULL;
 294         int ret;
 295         unsigned int events;
 296
 297         irqfd = kzalloc(sizeof(*irqfd), GFP_KERNEL);
 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
 307         file = eventfd_fget(args->fd);
 308         if (IS_ERR(file)) {
 309                 ret = PTR_ERR(file);
 310                 goto fail;
 311         }
 312
 313         eventfd = eventfd_ctx_fileget(file);
 314         if (IS_ERR(eventfd)) {
 315                 ret = PTR_ERR(eventfd);
 316                 goto fail;
 317         }
 318
 319         irqfd->eventfd = eventfd;
 320
 321         if (args->flags & KVM_IRQFD_FLAG_RESAMPLE) {
 322                 struct _irqfd_resampler *resampler;
 323
 324                 resamplefd = eventfd_ctx_fdget(args->resamplefd);
 325                 if (IS_ERR(resamplefd)) {
 326                         ret = PTR_ERR(resamplefd);
 327                         goto fail;
 328                 }
 329
 330                 irqfd->resamplefd = resamplefd;
 331                 INIT_LIST_HEAD(&irqfd->resampler_link);
 332
 333                 mutex_lock(&kvm->irqfds.resampler_lock);
 334
 335                 list_for_each_entry(resampler,
 336                                     &kvm->irqfds.resampler_list, link) {
 337                         if (resampler->notifier.gsi == irqfd->gsi) {
 338                                 irqfd->resampler = resampler;
 339                                 break;
 340                         }
 341                 }
 342
 343                 if (!irqfd->resampler) {
 344                         resampler = kzalloc(sizeof(*resampler), GFP_KERNEL);
 345                         if (!resampler) {
 346                                 ret = -ENOMEM;
 347                                 mutex_unlock(&kvm->irqfds.resampler_lock);
 348                                 goto fail;
 349                         }
 350
 351                         resampler->kvm = kvm;
 352                         INIT_LIST_HEAD(&resampler->list);
 353                         resampler->notifier.gsi = irqfd->gsi;
 354                         resampler->notifier.irq_acked = irqfd_resampler_ack;
 355                         INIT_LIST_HEAD(&resampler->link);
 356
 357                         list_add(&resampler->link, &kvm->irqfds.resampler_list);
 358                         kvm_register_irq_ack_notifier(kvm,
 359                                                       &resampler->notifier);
 360                         irqfd->resampler = resampler;
 361                 }
 362
 363                 list_add_rcu(&irqfd->resampler_link, &irqfd->resampler->list);
 364                 synchronize_rcu();
 365
 366                 mutex_unlock(&kvm->irqfds.resampler_lock);
 367         }
 368
 369         /*
 370          * Install our own custom wake-up handling so we are notified via
 371          * a callback whenever someone signals the underlying eventfd
 372          */
 373         init_waitqueue_func_entry(&irqfd->wait, irqfd_wakeup);
 374         init_poll_funcptr(&irqfd->pt, irqfd_ptable_queue_proc);
 375
 376         spin_lock_irq(&kvm->irqfds.lock);
 377
 378         ret = 0;
 379         list_for_each_entry(tmp, &kvm->irqfds.items, list) {
 380                 if (irqfd->eventfd != tmp->eventfd)
 381                         continue;
 382                 /* This fd is used for another irq already. */
 383                 ret = -EBUSY;
 384                 spin_unlock_irq(&kvm->irqfds.lock);
 385                 goto fail;
 386         }
 387
 388         irq_rt = rcu_dereference_protected(kvm->irq_routing,
 389                                            lockdep_is_held(&kvm->irqfds.lock));
 390         irqfd_update(kvm, irqfd, irq_rt);
 391
 392         events = file->f_op->poll(file, &irqfd->pt);
 393
 394         list_add_tail(&irqfd->list, &kvm->irqfds.items);
 395
 396         /*
 397          * Check if there was an event already pending on the eventfd
 398          * before we registered, and trigger it as if we didn't miss it.
 399          */
 400         if (events & POLLIN)
 401                 schedule_work(&irqfd->inject);
 402
 403         spin_unlock_irq(&kvm->irqfds.lock);
 404
 405         /*
 406          * do not drop the file until the irqfd is fully initialized, otherwise
 407          * we might race against the POLLHUP
 408          */
 409         fput(file);
 410
 411         return 0;
 412
 413 fail:
 414         if (irqfd->resampler)
 415                 irqfd_resampler_shutdown(irqfd);
 416
 417         if (resamplefd && !IS_ERR(resamplefd))
 418                 eventfd_ctx_put(resamplefd);
 419
 420         if (eventfd && !IS_ERR(eventfd))
 421                 eventfd_ctx_put(eventfd);
 422
 423         if (!IS_ERR(file))
 424                 fput(file);
 425
 426         kfree(irqfd);
 427         return ret;
 428 }
 429 #endif
 430
 431 void
 432 kvm_eventfd_init(struct kvm *kvm)
 433 {
 434 #ifdef __KVM_HAVE_IOAPIC
 435         spin_lock_init(&kvm->irqfds.lock);
 436         INIT_LIST_HEAD(&kvm->irqfds.items);
 437         INIT_LIST_HEAD(&kvm->irqfds.resampler_list);
 438         mutex_init(&kvm->irqfds.resampler_lock);
 439 #endif
 440         INIT_LIST_HEAD(&kvm->ioeventfds);
 441 }
 442
 443 #ifdef __KVM_HAVE_IOAPIC
 444 /*
 445  * shutdown any irqfd's that match fd+gsi
 446  */
 447 static int
 448 kvm_irqfd_deassign(struct kvm *kvm, struct kvm_irqfd *args)
 449 {
 450         struct _irqfd *irqfd, *tmp;
 451         struct eventfd_ctx *eventfd;
 452
 453         eventfd = eventfd_ctx_fdget(args->fd);
 454         if (IS_ERR(eventfd))
 455                 return PTR_ERR(eventfd);
 456
 457         spin_lock_irq(&kvm->irqfds.lock);
 458
 459         list_for_each_entry_safe(irqfd, tmp, &kvm->irqfds.items, list) {
 460                 if (irqfd->eventfd == eventfd && irqfd->gsi == args->gsi) {
 461                         /*
 462                          * This rcu_assign_pointer is needed for when
 463                          * another thread calls kvm_irq_routing_update before
 464                          * we flush workqueue below (we synchronize with
 465                          * kvm_irq_routing_update using irqfds.lock).
 466                          * It is paired with synchronize_rcu done by caller
 467                          * of that function.
 468                          */
 469                         rcu_assign_pointer(irqfd->irq_entry, NULL);
 470                         irqfd_deactivate(irqfd);
 471                 }
 472         }
 473
 474         spin_unlock_irq(&kvm->irqfds.lock);
 475         eventfd_ctx_put(eventfd);
 476
 477         /*
 478          * Block until we know all outstanding shutdown jobs have completed
 479          * so that we guarantee there will not be any more interrupts on this
 480          * gsi once this deassign function returns.
 481          */
 482         flush_workqueue(irqfd_cleanup_wq);
 483
 484         return 0;
 485 }
 486
 487 int
 488 kvm_irqfd(struct kvm *kvm, struct kvm_irqfd *args)
 489 {
 490         if (args->flags & ~(KVM_IRQFD_FLAG_DEASSIGN | KVM_IRQFD_FLAG_RESAMPLE))
 491                 return -EINVAL;
 492
 493         if (args->flags & KVM_IRQFD_FLAG_DEASSIGN)
 494                 return kvm_irqfd_deassign(kvm, args);
 495
 496         return kvm_irqfd_assign(kvm, args);
 497 }
 498
 499 /*
 500  * This function is called as the kvm VM fd is being released. Shutdown all
 501  * irqfds that still remain open
 502  */
 503 void
 504 kvm_irqfd_release(struct kvm *kvm)
 505 {
 506         struct _irqfd *irqfd, *tmp;
 507
 508         spin_lock_irq(&kvm->irqfds.lock);
 509
 510         list_for_each_entry_safe(irqfd, tmp, &kvm->irqfds.items, list)
 511                 irqfd_deactivate(irqfd);
 512
 513         spin_unlock_irq(&kvm->irqfds.lock);
 514
 515         /*
 516          * Block until we know all outstanding shutdown jobs have completed
 517          * since we do not take a kvm* reference.
 518          */
 519         flush_workqueue(irqfd_cleanup_wq);
 520
 521 }
 522
 523 /*
 524  * Change irq_routing and irqfd.
 525  * Caller must invoke synchronize_rcu afterwards.
 526  */
 527 void kvm_irq_routing_update(struct kvm *kvm,
 528                             struct kvm_irq_routing_table *irq_rt)
 529 {
 530         struct _irqfd *irqfd;
 531
 532         spin_lock_irq(&kvm->irqfds.lock);
 533
 534         rcu_assign_pointer(kvm->irq_routing, irq_rt);
 535
 536         list_for_each_entry(irqfd, &kvm->irqfds.items, list)
 537                 irqfd_update(kvm, irqfd, irq_rt);
 538
 539         spin_unlock_irq(&kvm->irqfds.lock);
 540 }
 541
 542 /*
 543  * create a host-wide workqueue for issuing deferred shutdown requests
 544  * aggregated from all vm* instances. We need our own isolated single-thread
 545  * queue to prevent deadlock against flushing the normal work-queue.
 546  */
 547 static int __init irqfd_module_init(void)
 548 {
 549         irqfd_cleanup_wq = create_singlethread_workqueue("kvm-irqfd-cleanup");
 550         if (!irqfd_cleanup_wq)
 551                 return -ENOMEM;
 552
 553         return 0;
 554 }
 555
 556 static void __exit irqfd_module_exit(void)
 557 {
 558         destroy_workqueue(irqfd_cleanup_wq);
 559 }
 560
 561 module_init(irqfd_module_init);
 562 module_exit(irqfd_module_exit);
 563 #endif
 564
 565 /*
 566  * --------------------------------------------------------------------
 567  * ioeventfd: translate a PIO/MMIO memory write to an eventfd signal.
 568  *
 569  * userspace can register a PIO/MMIO address with an eventfd for receiving
 570  * notification when the memory has been touched.
 571  * --------------------------------------------------------------------
 572  */
 573
 574 struct _ioeventfd {
 575         struct list_head     list;
 576         u64                  addr;
 577         int                  length;
 578         struct eventfd_ctx  *eventfd;
 579         u64                  datamatch;
 580         struct kvm_io_device dev;
 581         bool                 wildcard;
 582 };
 583
 584 static inline struct _ioeventfd *
 585 to_ioeventfd(struct kvm_io_device *dev)
 586 {
 587         return container_of(dev, struct _ioeventfd, dev);
 588 }
 589
 590 static void
 591 ioeventfd_release(struct _ioeventfd *p)
 592 {
 593         eventfd_ctx_put(p->eventfd);
 594         list_del(&p->list);
 595         kfree(p);
 596 }
 597
 598 static bool
 599 ioeventfd_in_range(struct _ioeventfd *p, gpa_t addr, int len, const void *val)
 600 {
 601         u64 _val;
 602
 603         if (!(addr == p->addr && len == p->length))
 604                 /* address-range must be precise for a hit */
 605                 return false;
 606
 607         if (p->wildcard)
 608                 /* all else equal, wildcard is always a hit */
 609                 return true;
 610
 611         /* otherwise, we have to actually compare the data */
 612
 613         BUG_ON(!IS_ALIGNED((unsigned long)val, len));
 614
 615         switch (len) {
 616         case 1:
 617                 _val = *(u8 *)val;
 618                 break;
 619         case 2:
 620                 _val = *(u16 *)val;
 621                 break;
 622         case 4:
 623                 _val = *(u32 *)val;
 624                 break;
 625         case 8:
 626                 _val = *(u64 *)val;
 627                 break;
 628         default:
 629                 return false;
 630         }
 631
 632         return _val == p->datamatch ? true : false;
 633 }
 634
 635 /* MMIO/PIO writes trigger an event if the addr/val match */
 636 static int
 637 ioeventfd_write(struct kvm_io_device *this, gpa_t addr, int len,
 638                 const void *val)
 639 {
 640         struct _ioeventfd *p = to_ioeventfd(this);
 641
 642         if (!ioeventfd_in_range(p, addr, len, val))
 643                 return -EOPNOTSUPP;
 644
 645         eventfd_signal(p->eventfd, 1);
 646         return 0;
 647 }
 648
 649 /*
 650  * This function is called as KVM is completely shutting down.  We do not
 651  * need to worry about locking just nuke anything we have as quickly as possible
 652  */
 653 static void
 654 ioeventfd_destructor(struct kvm_io_device *this)
 655 {
 656         struct _ioeventfd *p = to_ioeventfd(this);
 657
 658         ioeventfd_release(p);
 659 }
 660
 661 static const struct kvm_io_device_ops ioeventfd_ops = {
 662         .write      = ioeventfd_write,
 663         .destructor = ioeventfd_destructor,
 664 };
 665
 666 /* assumes kvm->slots_lock held */
 667 static bool
 668 ioeventfd_check_collision(struct kvm *kvm, struct _ioeventfd *p)
 669 {
 670         struct _ioeventfd *_p;
 671
 672         list_for_each_entry(_p, &kvm->ioeventfds, list)
 673                 if (_p->addr == p->addr && _p->length == p->length &&
 674                     (_p->wildcard || p->wildcard ||
 675                      _p->datamatch == p->datamatch))
 676                         return true;
 677
 678         return false;
 679 }
 680
 681 static int
 682 kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
 683 {
 684         int                       pio = args->flags & KVM_IOEVENTFD_FLAG_PIO;
 685         enum kvm_bus              bus_idx = pio ? KVM_PIO_BUS : KVM_MMIO_BUS;
 686         struct _ioeventfd        *p;
 687         struct eventfd_ctx       *eventfd;
 688         int                       ret;
 689
 690         /* must be natural-word sized */
 691         switch (args->len) {
 692         case 1:
 693         case 2:
 694         case 4:
 695         case 8:
 696                 break;
 697         default:
 698                 return -EINVAL;
 699         }
 700
 701         /* check for range overflow */
 702         if (args->addr + args->len < args->addr)
 703                 return -EINVAL;
 704
 705         /* check for extra flags that we don't understand */
 706         if (args->flags & ~KVM_IOEVENTFD_VALID_FLAG_MASK)
 707                 return -EINVAL;
 708
 709         eventfd = eventfd_ctx_fdget(args->fd);
 710         if (IS_ERR(eventfd))
 711                 return PTR_ERR(eventfd);
 712
 713         p = kzalloc(sizeof(*p), GFP_KERNEL);
 714         if (!p) {
 715                 ret = -ENOMEM;
 716                 goto fail;
 717         }
 718
 719         INIT_LIST_HEAD(&p->list);
 720         p->addr    = args->addr;
 721         p->length  = args->len;
 722         p->eventfd = eventfd;
 723
 724         /* The datamatch feature is optional, otherwise this is a wildcard */
 725         if (args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH)
 726                 p->datamatch = args->datamatch;
 727         else
 728                 p->wildcard = true;
 729
 730         mutex_lock(&kvm->slots_lock);
 731
 732         /* Verify that there isn't a match already */
 733         if (ioeventfd_check_collision(kvm, p)) {
 734                 ret = -EEXIST;
 735                 goto unlock_fail;
 736         }
 737
 738         kvm_iodevice_init(&p->dev, &ioeventfd_ops);
 739
 740         ret = kvm_io_bus_register_dev(kvm, bus_idx, p->addr, p->length,
 741                                       &p->dev);
 742         if (ret < 0)
 743                 goto unlock_fail;
 744
 745         list_add_tail(&p->list, &kvm->ioeventfds);
 746
 747         mutex_unlock(&kvm->slots_lock);
 748
 749         return 0;
 750
 751 unlock_fail:
 752         mutex_unlock(&kvm->slots_lock);
 753
 754 fail:
 755         kfree(p);
 756         eventfd_ctx_put(eventfd);
 757
 758         return ret;
 759 }
 760
 761 static int
 762 kvm_deassign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
 763 {
 764         int                       pio = args->flags & KVM_IOEVENTFD_FLAG_PIO;
 765         enum kvm_bus              bus_idx = pio ? KVM_PIO_BUS : KVM_MMIO_BUS;
 766         struct _ioeventfd        *p, *tmp;
 767         struct eventfd_ctx       *eventfd;
 768         int                       ret = -ENOENT;
 769
 770         eventfd = eventfd_ctx_fdget(args->fd);
 771         if (IS_ERR(eventfd))
 772                 return PTR_ERR(eventfd);
 773
 774         mutex_lock(&kvm->slots_lock);
 775
 776         list_for_each_entry_safe(p, tmp, &kvm->ioeventfds, list) {
 777                 bool wildcard = !(args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH);
 778
 779                 if (p->eventfd != eventfd  ||
 780                     p->addr != args->addr  ||
 781                     p->length != args->len ||
 782                     p->wildcard != wildcard)
 783                         continue;
 784
 785                 if (!p->wildcard && p->datamatch != args->datamatch)
 786                         continue;
 787
 788                 kvm_io_bus_unregister_dev(kvm, bus_idx, &p->dev);
 789                 ioeventfd_release(p);
 790                 ret = 0;
 791                 break;
 792         }
 793
 794         mutex_unlock(&kvm->slots_lock);
 795
 796         eventfd_ctx_put(eventfd);
 797
 798         return ret;
 799 }
 800
 801 int
 802 kvm_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
 803 {
 804         if (args->flags & KVM_IOEVENTFD_FLAG_DEASSIGN)
 805                 return kvm_deassign_ioeventfd(kvm, args);
 806
 807         return kvm_assign_ioeventfd(kvm, args);
 808 }