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 CONFIG_HAVE_KVM_IRQ_ROUTING
  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                                 false);
 105                 kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 0,
 106                                 false);
 107         } else
 108                 kvm_set_irq(kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
 109                             irqfd->gsi, 1, false);
 110 }
 111
 112 /*
 113  * Since resampler irqfds share an IRQ source ID, we de-assert once
 114  * then notify all of the resampler irqfds using this GSI.  We can't
 115  * do multiple de-asserts or we risk racing with incoming re-asserts.
 116  */
 117 static void
 118 irqfd_resampler_ack(struct kvm_irq_ack_notifier *kian)
 119 {
 120         struct _irqfd_resampler *resampler;
 121         struct _irqfd *irqfd;
 122
 123         resampler = container_of(kian, struct _irqfd_resampler, notifier);
 124
 125         kvm_set_irq(resampler->kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
 126                     resampler->notifier.gsi, 0, false);
 127
 128         rcu_read_lock();
 129
 130         list_for_each_entry_rcu(irqfd, &resampler->list, resampler_link)
 131                 eventfd_signal(irqfd->resamplefd, 1);
 132
 133         rcu_read_unlock();
 134 }
 135
 136 static void
 137 irqfd_resampler_shutdown(struct _irqfd *irqfd)
 138 {
 139         struct _irqfd_resampler *resampler = irqfd->resampler;
 140         struct kvm *kvm = resampler->kvm;
 141
 142         mutex_lock(&kvm->irqfds.resampler_lock);
 143
 144         list_del_rcu(&irqfd->resampler_link);
 145         synchronize_rcu();
 146
 147         if (list_empty(&resampler->list)) {
 148                 list_del(&resampler->link);
 149                 kvm_unregister_irq_ack_notifier(kvm, &resampler->notifier);
 150                 kvm_set_irq(kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
 151                             resampler->notifier.gsi, 0, false);
 152                 kfree(resampler);
 153         }
 154
 155         mutex_unlock(&kvm->irqfds.resampler_lock);
 156 }
 157
 158 /*
 159  * Race-free decouple logic (ordering is critical)
 160  */
 161 static void
 162 irqfd_shutdown(struct work_struct *work)
 163 {
 164         struct _irqfd *irqfd = container_of(work, struct _irqfd, shutdown);
 165         u64 cnt;
 166
 167         /*
 168          * Synchronize with the wait-queue and unhook ourselves to prevent
 169          * further events.
 170          */
 171         eventfd_ctx_remove_wait_queue(irqfd->eventfd, &irqfd->wait, &cnt);
 172
 173         /*
 174          * We know no new events will be scheduled at this point, so block
 175          * until all previously outstanding events have completed
 176          */
 177         flush_work(&irqfd->inject);
 178
 179         if (irqfd->resampler) {
 180                 irqfd_resampler_shutdown(irqfd);
 181                 eventfd_ctx_put(irqfd->resamplefd);
 182         }
 183
 184         /*
 185          * It is now safe to release the object's resources
 186          */
 187         eventfd_ctx_put(irqfd->eventfd);
 188         kfree(irqfd);
 189 }
 190
 191
 192 /* assumes kvm->irqfds.lock is held */
 193 static bool
 194 irqfd_is_active(struct _irqfd *irqfd)
 195 {
 196         return list_empty(&irqfd->list) ? false : true;
 197 }
 198
 199 /*
 200  * Mark the irqfd as inactive and schedule it for removal
 201  *
 202  * assumes kvm->irqfds.lock is held
 203  */
 204 static void
 205 irqfd_deactivate(struct _irqfd *irqfd)
 206 {
 207         BUG_ON(!irqfd_is_active(irqfd));
 208
 209         list_del_init(&irqfd->list);
 210
 211         queue_work(irqfd_cleanup_wq, &irqfd->shutdown);
 212 }
 213
 214 /*
 215  * Called with wqh->lock held and interrupts disabled
 216  */
 217 static int
 218 irqfd_wakeup(wait_queue_t *wait, unsigned mode, int sync, void *key)
 219 {
 220         struct _irqfd *irqfd = container_of(wait, struct _irqfd, wait);
 221         unsigned long flags = (unsigned long)key;
 222         struct kvm_kernel_irq_routing_entry *irq;
 223         struct kvm *kvm = irqfd->kvm;
 224
 225         if (flags & POLLIN) {
 226                 rcu_read_lock();
 227                 irq = rcu_dereference(irqfd->irq_entry);
 228                 /* An event has been signaled, inject an interrupt */
 229                 if (irq)
 230                         kvm_set_msi(irq, kvm, KVM_USERSPACE_IRQ_SOURCE_ID, 1,
 231                                         false);
 232                 else
 233                         schedule_work(&irqfd->inject);
 234                 rcu_read_unlock();
 235         }
 236
 237         if (flags & POLLHUP) {
 238                 /* The eventfd is closing, detach from KVM */
 239                 unsigned long flags;
 240
 241                 spin_lock_irqsave(&kvm->irqfds.lock, flags);
 242
 243                 /*
 244                  * We must check if someone deactivated the irqfd before
 245                  * we could acquire the irqfds.lock since the item is
 246                  * deactivated from the KVM side before it is unhooked from
 247                  * the wait-queue.  If it is already deactivated, we can
 248                  * simply return knowing the other side will cleanup for us.
 249                  * We cannot race against the irqfd going away since the
 250                  * other side is required to acquire wqh->lock, which we hold
 251                  */
 252                 if (irqfd_is_active(irqfd))
 253                         irqfd_deactivate(irqfd);
 254
 255                 spin_unlock_irqrestore(&kvm->irqfds.lock, flags);
 256         }
 257
 258         return 0;
 259 }
 260
 261 static void
 262 irqfd_ptable_queue_proc(struct file *file, wait_queue_head_t *wqh,
 263                         poll_table *pt)
 264 {
 265         struct _irqfd *irqfd = container_of(pt, struct _irqfd, pt);
 266         add_wait_queue(wqh, &irqfd->wait);
 267 }
 268
 269 /* Must be called under irqfds.lock */
 270 static void irqfd_update(struct kvm *kvm, struct _irqfd *irqfd,
 271                          struct kvm_irq_routing_table *irq_rt)
 272 {
 273         struct kvm_kernel_irq_routing_entry *e;
 274
 275         if (irqfd->gsi >= irq_rt->nr_rt_entries) {
 276                 rcu_assign_pointer(irqfd->irq_entry, NULL);
 277                 return;
 278         }
 279
 280         hlist_for_each_entry(e, &irq_rt->map[irqfd->gsi], link) {
 281                 /* Only fast-path MSI. */
 282                 if (e->type == KVM_IRQ_ROUTING_MSI)
 283                         rcu_assign_pointer(irqfd->irq_entry, e);
 284                 else
 285                         rcu_assign_pointer(irqfd->irq_entry, NULL);
 286         }
 287 }
 288
 289 static int
 290 kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args)
 291 {
 292         struct kvm_irq_routing_table *irq_rt;
 293         struct _irqfd *irqfd, *tmp;
 294         struct fd f;
 295         struct eventfd_ctx *eventfd = NULL, *resamplefd = NULL;
 296         int ret;
 297         unsigned int events;
 298
 299         irqfd = kzalloc(sizeof(*irqfd), GFP_KERNEL);
 300         if (!irqfd)
 301                 return -ENOMEM;
 302
 303         irqfd->kvm = kvm;
 304         irqfd->gsi = args->gsi;
 305         INIT_LIST_HEAD(&irqfd->list);
 306         INIT_WORK(&irqfd->inject, irqfd_inject);
 307         INIT_WORK(&irqfd->shutdown, irqfd_shutdown);
 308
 309         f = fdget(args->fd);
 310         if (!f.file) {
 311                 ret = -EBADF;
 312                 goto out;
 313         }
 314
 315         eventfd = eventfd_ctx_fileget(f.file);
 316         if (IS_ERR(eventfd)) {
 317                 ret = PTR_ERR(eventfd);
 318                 goto fail;
 319         }
 320
 321         irqfd->eventfd = eventfd;
 322
 323         if (args->flags & KVM_IRQFD_FLAG_RESAMPLE) {
 324                 struct _irqfd_resampler *resampler;
 325
 326                 resamplefd = eventfd_ctx_fdget(args->resamplefd);
 327                 if (IS_ERR(resamplefd)) {
 328                         ret = PTR_ERR(resamplefd);
 329                         goto fail;
 330                 }
 331
 332                 irqfd->resamplefd = resamplefd;
 333                 INIT_LIST_HEAD(&irqfd->resampler_link);
 334
 335                 mutex_lock(&kvm->irqfds.resampler_lock);
 336
 337                 list_for_each_entry(resampler,
 338                                     &kvm->irqfds.resampler_list, link) {
 339                         if (resampler->notifier.gsi == irqfd->gsi) {
 340                                 irqfd->resampler = resampler;
 341                                 break;
 342                         }
 343                 }
 344
 345                 if (!irqfd->resampler) {
 346                         resampler = kzalloc(sizeof(*resampler), GFP_KERNEL);
 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_rcu();
 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         irq_rt = rcu_dereference_protected(kvm->irq_routing,
 391                                            lockdep_is_held(&kvm->irqfds.lock));
 392         irqfd_update(kvm, irqfd, irq_rt);
 393
 394         list_add_tail(&irqfd->list, &kvm->irqfds.items);
 395
 396         spin_unlock_irq(&kvm->irqfds.lock);
 397
 398         /*
 399          * Check if there was an event already pending on the eventfd
 400          * before we registered, and trigger it as if we didn't miss it.
 401          */
 402         events = f.file->f_op->poll(f.file, &irqfd->pt);
 403
 404         if (events & POLLIN)
 405                 schedule_work(&irqfd->inject);
 406
 407         /*
 408          * do not drop the file until the irqfd is fully initialized, otherwise
 409          * we might race against the POLLHUP
 410          */
 411         fdput(f);
 412
 413         return 0;
 414
 415 fail:
 416         if (irqfd->resampler)
 417                 irqfd_resampler_shutdown(irqfd);
 418
 419         if (resamplefd && !IS_ERR(resamplefd))
 420                 eventfd_ctx_put(resamplefd);
 421
 422         if (eventfd && !IS_ERR(eventfd))
 423                 eventfd_ctx_put(eventfd);
 424
 425         fdput(f);
 426
 427 out:
 428         kfree(irqfd);
 429         return ret;
 430 }
 431 #endif
 432
 433 void
 434 kvm_eventfd_init(struct kvm *kvm)
 435 {
 436 #ifdef CONFIG_HAVE_KVM_IRQ_ROUTING
 437         spin_lock_init(&kvm->irqfds.lock);
 438         INIT_LIST_HEAD(&kvm->irqfds.items);
 439         INIT_LIST_HEAD(&kvm->irqfds.resampler_list);
 440         mutex_init(&kvm->irqfds.resampler_lock);
 441 #endif
 442         INIT_LIST_HEAD(&kvm->ioeventfds);
 443 }
 444
 445 #ifdef CONFIG_HAVE_KVM_IRQ_ROUTING
 446 /*
 447  * shutdown any irqfd's that match fd+gsi
 448  */
 449 static int
 450 kvm_irqfd_deassign(struct kvm *kvm, struct kvm_irqfd *args)
 451 {
 452         struct _irqfd *irqfd, *tmp;
 453         struct eventfd_ctx *eventfd;
 454
 455         eventfd = eventfd_ctx_fdget(args->fd);
 456         if (IS_ERR(eventfd))
 457                 return PTR_ERR(eventfd);
 458
 459         spin_lock_irq(&kvm->irqfds.lock);
 460
 461         list_for_each_entry_safe(irqfd, tmp, &kvm->irqfds.items, list) {
 462                 if (irqfd->eventfd == eventfd && irqfd->gsi == args->gsi) {
 463                         /*
 464                          * This rcu_assign_pointer is needed for when
 465                          * another thread calls kvm_irq_routing_update before
 466                          * we flush workqueue below (we synchronize with
 467                          * kvm_irq_routing_update using irqfds.lock).
 468                          * It is paired with synchronize_rcu done by caller
 469                          * of that function.
 470                          */
 471                         rcu_assign_pointer(irqfd->irq_entry, NULL);
 472                         irqfd_deactivate(irqfd);
 473                 }
 474         }
 475
 476         spin_unlock_irq(&kvm->irqfds.lock);
 477         eventfd_ctx_put(eventfd);
 478
 479         /*
 480          * Block until we know all outstanding shutdown jobs have completed
 481          * so that we guarantee there will not be any more interrupts on this
 482          * gsi once this deassign function returns.
 483          */
 484         flush_workqueue(irqfd_cleanup_wq);
 485
 486         return 0;
 487 }
 488
 489 int
 490 kvm_irqfd(struct kvm *kvm, struct kvm_irqfd *args)
 491 {
 492         if (args->flags & ~(KVM_IRQFD_FLAG_DEASSIGN | KVM_IRQFD_FLAG_RESAMPLE))
 493                 return -EINVAL;
 494
 495         if (args->flags & KVM_IRQFD_FLAG_DEASSIGN)
 496                 return kvm_irqfd_deassign(kvm, args);
 497
 498         return kvm_irqfd_assign(kvm, args);
 499 }
 500
 501 /*
 502  * This function is called as the kvm VM fd is being released. Shutdown all
 503  * irqfds that still remain open
 504  */
 505 void
 506 kvm_irqfd_release(struct kvm *kvm)
 507 {
 508         struct _irqfd *irqfd, *tmp;
 509
 510         spin_lock_irq(&kvm->irqfds.lock);
 511
 512         list_for_each_entry_safe(irqfd, tmp, &kvm->irqfds.items, list)
 513                 irqfd_deactivate(irqfd);
 514
 515         spin_unlock_irq(&kvm->irqfds.lock);
 516
 517         /*
 518          * Block until we know all outstanding shutdown jobs have completed
 519          * since we do not take a kvm* reference.
 520          */
 521         flush_workqueue(irqfd_cleanup_wq);
 522
 523 }
 524
 525 /*
 526  * Change irq_routing and irqfd.
 527  * Caller must invoke synchronize_rcu afterwards.
 528  */
 529 void kvm_irq_routing_update(struct kvm *kvm,
 530                             struct kvm_irq_routing_table *irq_rt)
 531 {
 532         struct _irqfd *irqfd;
 533
 534         spin_lock_irq(&kvm->irqfds.lock);
 535
 536         rcu_assign_pointer(kvm->irq_routing, irq_rt);
 537
 538         list_for_each_entry(irqfd, &kvm->irqfds.items, list)
 539                 irqfd_update(kvm, irqfd, irq_rt);
 540
 541         spin_unlock_irq(&kvm->irqfds.lock);
 542 }
 543
 544 /*
 545  * create a host-wide workqueue for issuing deferred shutdown requests
 546  * aggregated from all vm* instances. We need our own isolated single-thread
 547  * queue to prevent deadlock against flushing the normal work-queue.
 548  */
 549 int kvm_irqfd_init(void)
 550 {
 551         irqfd_cleanup_wq = create_singlethread_workqueue("kvm-irqfd-cleanup");
 552         if (!irqfd_cleanup_wq)
 553                 return -ENOMEM;
 554
 555         return 0;
 556 }
 557
 558 void kvm_irqfd_exit(void)
 559 {
 560         destroy_workqueue(irqfd_cleanup_wq);
 561 }
 562 #endif
 563
 564 /*
 565  * --------------------------------------------------------------------
 566  * ioeventfd: translate a PIO/MMIO memory write to an eventfd signal.
 567  *
 568  * userspace can register a PIO/MMIO address with an eventfd for receiving
 569  * notification when the memory has been touched.
 570  * --------------------------------------------------------------------
 571  */
 572
 573 struct _ioeventfd {
 574         struct list_head     list;
 575         u64                  addr;
 576         int                  length;
 577         struct eventfd_ctx  *eventfd;
 578         u64                  datamatch;
 579         struct kvm_io_device dev;
 580         u8                   bus_idx;
 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->bus_idx == p->bus_idx &&
 674                     _p->addr == p->addr && _p->length == p->length &&
 675                     (_p->wildcard || p->wildcard ||
 676                      _p->datamatch == p->datamatch))
 677                         return true;
 678
 679         return false;
 680 }
 681
 682 static enum kvm_bus ioeventfd_bus_from_flags(__u32 flags)
 683 {
 684         if (flags & KVM_IOEVENTFD_FLAG_PIO)
 685                 return KVM_PIO_BUS;
 686         if (flags & KVM_IOEVENTFD_FLAG_VIRTIO_CCW_NOTIFY)
 687                 return KVM_VIRTIO_CCW_NOTIFY_BUS;
 688         return KVM_MMIO_BUS;
 689 }
 690
 691 static int
 692 kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
 693 {
 694         enum kvm_bus              bus_idx;
 695         struct _ioeventfd        *p;
 696         struct eventfd_ctx       *eventfd;
 697         int                       ret;
 698
 699         bus_idx = ioeventfd_bus_from_flags(args->flags);
 700         /* must be natural-word sized */
 701         switch (args->len) {
 702         case 1:
 703         case 2:
 704         case 4:
 705         case 8:
 706                 break;
 707         default:
 708                 return -EINVAL;
 709         }
 710
 711         /* check for range overflow */
 712         if (args->addr + args->len < args->addr)
 713                 return -EINVAL;
 714
 715         /* check for extra flags that we don't understand */
 716         if (args->flags & ~KVM_IOEVENTFD_VALID_FLAG_MASK)
 717                 return -EINVAL;
 718
 719         eventfd = eventfd_ctx_fdget(args->fd);
 720         if (IS_ERR(eventfd))
 721                 return PTR_ERR(eventfd);
 722
 723         p = kzalloc(sizeof(*p), GFP_KERNEL);
 724         if (!p) {
 725                 ret = -ENOMEM;
 726                 goto fail;
 727         }
 728
 729         INIT_LIST_HEAD(&p->list);
 730         p->addr    = args->addr;
 731         p->bus_idx = bus_idx;
 732         p->length  = args->len;
 733         p->eventfd = eventfd;
 734
 735         /* The datamatch feature is optional, otherwise this is a wildcard */
 736         if (args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH)
 737                 p->datamatch = args->datamatch;
 738         else
 739                 p->wildcard = true;
 740
 741         mutex_lock(&kvm->slots_lock);
 742
 743         /* Verify that there isn't a match already */
 744         if (ioeventfd_check_collision(kvm, p)) {
 745                 ret = -EEXIST;
 746                 goto unlock_fail;
 747         }
 748
 749         kvm_iodevice_init(&p->dev, &ioeventfd_ops);
 750
 751         ret = kvm_io_bus_register_dev(kvm, bus_idx, p->addr, p->length,
 752                                       &p->dev);
 753         if (ret < 0)
 754                 goto unlock_fail;
 755
 756         kvm->buses[bus_idx]->ioeventfd_count++;
 757         list_add_tail(&p->list, &kvm->ioeventfds);
 758
 759         mutex_unlock(&kvm->slots_lock);
 760
 761         return 0;
 762
 763 unlock_fail:
 764         mutex_unlock(&kvm->slots_lock);
 765
 766 fail:
 767         kfree(p);
 768         eventfd_ctx_put(eventfd);
 769
 770         return ret;
 771 }
 772
 773 static int
 774 kvm_deassign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
 775 {
 776         enum kvm_bus              bus_idx;
 777         struct _ioeventfd        *p, *tmp;
 778         struct eventfd_ctx       *eventfd;
 779         int                       ret = -ENOENT;
 780
 781         bus_idx = ioeventfd_bus_from_flags(args->flags);
 782         eventfd = eventfd_ctx_fdget(args->fd);
 783         if (IS_ERR(eventfd))
 784                 return PTR_ERR(eventfd);
 785
 786         mutex_lock(&kvm->slots_lock);
 787
 788         list_for_each_entry_safe(p, tmp, &kvm->ioeventfds, list) {
 789                 bool wildcard = !(args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH);
 790
 791                 if (p->bus_idx != bus_idx ||
 792                     p->eventfd != eventfd  ||
 793                     p->addr != args->addr  ||
 794                     p->length != args->len ||
 795                     p->wildcard != wildcard)
 796                         continue;
 797
 798                 if (!p->wildcard && p->datamatch != args->datamatch)
 799                         continue;
 800
 801                 kvm_io_bus_unregister_dev(kvm, bus_idx, &p->dev);
 802                 kvm->buses[bus_idx]->ioeventfd_count--;
 803                 ioeventfd_release(p);
 804                 ret = 0;
 805                 break;
 806         }
 807
 808         mutex_unlock(&kvm->slots_lock);
 809
 810         eventfd_ctx_put(eventfd);
 811
 812         return ret;
 813 }
 814
 815 int
 816 kvm_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
 817 {
 818         if (args->flags & KVM_IOEVENTFD_FLAG_DEASSIGN)
 819                 return kvm_deassign_ioeventfd(kvm, args);
 820
 821         return kvm_assign_ioeventfd(kvm, args);
 822 }