9718e98d6d2a84956d113bd43f55d804bd30d049
[linux-3.10.git] / 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 }