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Merge tag 'drivers-3.15' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc
[karo-tx-linux.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 #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 }