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TOMOYO Linux Cross Reference
Linux/virt/kvm/eventfd.c

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  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/srcu.h>
 35 #include <linux/slab.h>
 36 #include <linux/seqlock.h>
 37 #include <trace/events/kvm.h>
 38 
 39 #include <kvm/iodev.h>
 40 
 41 #ifdef CONFIG_HAVE_KVM_IRQFD
 42 /*
 43  * --------------------------------------------------------------------
 44  * irqfd: Allows an fd to be used to inject an interrupt to the guest
 45  *
 46  * Credit goes to Avi Kivity for the original idea.
 47  * --------------------------------------------------------------------
 48  */
 49 
 50 /*
 51  * Resampling irqfds are a special variety of irqfds used to emulate
 52  * level triggered interrupts.  The interrupt is asserted on eventfd
 53  * trigger.  On acknowledgement through the irq ack notifier, the
 54  * interrupt is de-asserted and userspace is notified through the
 55  * resamplefd.  All resamplers on the same gsi are de-asserted
 56  * together, so we don't need to track the state of each individual
 57  * user.  We can also therefore share the same irq source ID.
 58  */
 59 struct _irqfd_resampler {
 60         struct kvm *kvm;
 61         /*
 62          * List of resampling struct _irqfd objects sharing this gsi.
 63          * RCU list modified under kvm->irqfds.resampler_lock
 64          */
 65         struct list_head list;
 66         struct kvm_irq_ack_notifier notifier;
 67         /*
 68          * Entry in list of kvm->irqfd.resampler_list.  Use for sharing
 69          * resamplers among irqfds on the same gsi.
 70          * Accessed and modified under kvm->irqfds.resampler_lock
 71          */
 72         struct list_head link;
 73 };
 74 
 75 struct _irqfd {
 76         /* Used for MSI fast-path */
 77         struct kvm *kvm;
 78         wait_queue_t wait;
 79         /* Update side is protected by irqfds.lock */
 80         struct kvm_kernel_irq_routing_entry irq_entry;
 81         seqcount_t irq_entry_sc;
 82         /* Used for level IRQ fast-path */
 83         int gsi;
 84         struct work_struct inject;
 85         /* The resampler used by this irqfd (resampler-only) */
 86         struct _irqfd_resampler *resampler;
 87         /* Eventfd notified on resample (resampler-only) */
 88         struct eventfd_ctx *resamplefd;
 89         /* Entry in list of irqfds for a resampler (resampler-only) */
 90         struct list_head resampler_link;
 91         /* Used for setup/shutdown */
 92         struct eventfd_ctx *eventfd;
 93         struct list_head list;
 94         poll_table pt;
 95         struct work_struct shutdown;
 96 };
 97 
 98 static struct workqueue_struct *irqfd_cleanup_wq;
 99 
100 static void
101 irqfd_inject(struct work_struct *work)
102 {
103         struct _irqfd *irqfd = container_of(work, struct _irqfd, inject);
104         struct kvm *kvm = irqfd->kvm;
105 
106         if (!irqfd->resampler) {
107                 kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 1,
108                                 false);
109                 kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 0,
110                                 false);
111         } else
112                 kvm_set_irq(kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
113                             irqfd->gsi, 1, false);
114 }
115 
116 /*
117  * Since resampler irqfds share an IRQ source ID, we de-assert once
118  * then notify all of the resampler irqfds using this GSI.  We can't
119  * do multiple de-asserts or we risk racing with incoming re-asserts.
120  */
121 static void
122 irqfd_resampler_ack(struct kvm_irq_ack_notifier *kian)
123 {
124         struct _irqfd_resampler *resampler;
125         struct kvm *kvm;
126         struct _irqfd *irqfd;
127         int idx;
128 
129         resampler = container_of(kian, struct _irqfd_resampler, notifier);
130         kvm = resampler->kvm;
131 
132         kvm_set_irq(kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
133                     resampler->notifier.gsi, 0, false);
134 
135         idx = srcu_read_lock(&kvm->irq_srcu);
136 
137         list_for_each_entry_rcu(irqfd, &resampler->list, resampler_link)
138                 eventfd_signal(irqfd->resamplefd, 1);
139 
140         srcu_read_unlock(&kvm->irq_srcu, idx);
141 }
142 
143 static void
144 irqfd_resampler_shutdown(struct _irqfd *irqfd)
145 {
146         struct _irqfd_resampler *resampler = irqfd->resampler;
147         struct kvm *kvm = resampler->kvm;
148 
149         mutex_lock(&kvm->irqfds.resampler_lock);
150 
151         list_del_rcu(&irqfd->resampler_link);
152         synchronize_srcu(&kvm->irq_srcu);
153 
154         if (list_empty(&resampler->list)) {
155                 list_del(&resampler->link);
156                 kvm_unregister_irq_ack_notifier(kvm, &resampler->notifier);
157                 kvm_set_irq(kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
158                             resampler->notifier.gsi, 0, false);
159                 kfree(resampler);
160         }
161 
162         mutex_unlock(&kvm->irqfds.resampler_lock);
163 }
164 
165 /*
166  * Race-free decouple logic (ordering is critical)
167  */
168 static void
169 irqfd_shutdown(struct work_struct *work)
170 {
171         struct _irqfd *irqfd = container_of(work, struct _irqfd, shutdown);
172         u64 cnt;
173 
174         /*
175          * Synchronize with the wait-queue and unhook ourselves to prevent
176          * further events.
177          */
178         eventfd_ctx_remove_wait_queue(irqfd->eventfd, &irqfd->wait, &cnt);
179 
180         /*
181          * We know no new events will be scheduled at this point, so block
182          * until all previously outstanding events have completed
183          */
184         flush_work(&irqfd->inject);
185 
186         if (irqfd->resampler) {
187                 irqfd_resampler_shutdown(irqfd);
188                 eventfd_ctx_put(irqfd->resamplefd);
189         }
190 
191         /*
192          * It is now safe to release the object's resources
193          */
194         eventfd_ctx_put(irqfd->eventfd);
195         kfree(irqfd);
196 }
197 
198 
199 /* assumes kvm->irqfds.lock is held */
200 static bool
201 irqfd_is_active(struct _irqfd *irqfd)
202 {
203         return list_empty(&irqfd->list) ? false : true;
204 }
205 
206 /*
207  * Mark the irqfd as inactive and schedule it for removal
208  *
209  * assumes kvm->irqfds.lock is held
210  */
211 static void
212 irqfd_deactivate(struct _irqfd *irqfd)
213 {
214         BUG_ON(!irqfd_is_active(irqfd));
215 
216         list_del_init(&irqfd->list);
217 
218         queue_work(irqfd_cleanup_wq, &irqfd->shutdown);
219 }
220 
221 /*
222  * Called with wqh->lock held and interrupts disabled
223  */
224 static int
225 irqfd_wakeup(wait_queue_t *wait, unsigned mode, int sync, void *key)
226 {
227         struct _irqfd *irqfd = container_of(wait, struct _irqfd, wait);
228         unsigned long flags = (unsigned long)key;
229         struct kvm_kernel_irq_routing_entry irq;
230         struct kvm *kvm = irqfd->kvm;
231         unsigned seq;
232         int idx;
233 
234         if (flags & POLLIN) {
235                 idx = srcu_read_lock(&kvm->irq_srcu);
236                 do {
237                         seq = read_seqcount_begin(&irqfd->irq_entry_sc);
238                         irq = irqfd->irq_entry;
239                 } while (read_seqcount_retry(&irqfd->irq_entry_sc, seq));
240                 /* An event has been signaled, inject an interrupt */
241                 if (irq.type == KVM_IRQ_ROUTING_MSI)
242                         kvm_set_msi(&irq, kvm, KVM_USERSPACE_IRQ_SOURCE_ID, 1,
243                                         false);
244                 else
245                         schedule_work(&irqfd->inject);
246                 srcu_read_unlock(&kvm->irq_srcu, idx);
247         }
248 
249         if (flags & POLLHUP) {
250                 /* The eventfd is closing, detach from KVM */
251                 unsigned long flags;
252 
253                 spin_lock_irqsave(&kvm->irqfds.lock, flags);
254 
255                 /*
256                  * We must check if someone deactivated the irqfd before
257                  * we could acquire the irqfds.lock since the item is
258                  * deactivated from the KVM side before it is unhooked from
259                  * the wait-queue.  If it is already deactivated, we can
260                  * simply return knowing the other side will cleanup for us.
261                  * We cannot race against the irqfd going away since the
262                  * other side is required to acquire wqh->lock, which we hold
263                  */
264                 if (irqfd_is_active(irqfd))
265                         irqfd_deactivate(irqfd);
266 
267                 spin_unlock_irqrestore(&kvm->irqfds.lock, flags);
268         }
269 
270         return 0;
271 }
272 
273 static void
274 irqfd_ptable_queue_proc(struct file *file, wait_queue_head_t *wqh,
275                         poll_table *pt)
276 {
277         struct _irqfd *irqfd = container_of(pt, struct _irqfd, pt);
278         add_wait_queue(wqh, &irqfd->wait);
279 }
280 
281 /* Must be called under irqfds.lock */
282 static void irqfd_update(struct kvm *kvm, struct _irqfd *irqfd)
283 {
284         struct kvm_kernel_irq_routing_entry *e;
285         struct kvm_kernel_irq_routing_entry entries[KVM_NR_IRQCHIPS];
286         int i, n_entries;
287 
288         n_entries = kvm_irq_map_gsi(kvm, entries, irqfd->gsi);
289 
290         write_seqcount_begin(&irqfd->irq_entry_sc);
291 
292         irqfd->irq_entry.type = 0;
293 
294         e = entries;
295         for (i = 0; i < n_entries; ++i, ++e) {
296                 /* Only fast-path MSI. */
297                 if (e->type == KVM_IRQ_ROUTING_MSI)
298                         irqfd->irq_entry = *e;
299         }
300 
301         write_seqcount_end(&irqfd->irq_entry_sc);
302 }
303 
304 static int
305 kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args)
306 {
307         struct _irqfd *irqfd, *tmp;
308         struct fd f;
309         struct eventfd_ctx *eventfd = NULL, *resamplefd = NULL;
310         int ret;
311         unsigned int events;
312         int idx;
313 
314         if (!kvm_arch_intc_initialized(kvm))
315                 return -EAGAIN;
316 
317         irqfd = kzalloc(sizeof(*irqfd), GFP_KERNEL);
318         if (!irqfd)
319                 return -ENOMEM;
320 
321         irqfd->kvm = kvm;
322         irqfd->gsi = args->gsi;
323         INIT_LIST_HEAD(&irqfd->list);
324         INIT_WORK(&irqfd->inject, irqfd_inject);
325         INIT_WORK(&irqfd->shutdown, irqfd_shutdown);
326         seqcount_init(&irqfd->irq_entry_sc);
327 
328         f = fdget(args->fd);
329         if (!f.file) {
330                 ret = -EBADF;
331                 goto out;
332         }
333 
334         eventfd = eventfd_ctx_fileget(f.file);
335         if (IS_ERR(eventfd)) {
336                 ret = PTR_ERR(eventfd);
337                 goto fail;
338         }
339 
340         irqfd->eventfd = eventfd;
341 
342         if (args->flags & KVM_IRQFD_FLAG_RESAMPLE) {
343                 struct _irqfd_resampler *resampler;
344 
345                 resamplefd = eventfd_ctx_fdget(args->resamplefd);
346                 if (IS_ERR(resamplefd)) {
347                         ret = PTR_ERR(resamplefd);
348                         goto fail;
349                 }
350 
351                 irqfd->resamplefd = resamplefd;
352                 INIT_LIST_HEAD(&irqfd->resampler_link);
353 
354                 mutex_lock(&kvm->irqfds.resampler_lock);
355 
356                 list_for_each_entry(resampler,
357                                     &kvm->irqfds.resampler_list, link) {
358                         if (resampler->notifier.gsi == irqfd->gsi) {
359                                 irqfd->resampler = resampler;
360                                 break;
361                         }
362                 }
363 
364                 if (!irqfd->resampler) {
365                         resampler = kzalloc(sizeof(*resampler), GFP_KERNEL);
366                         if (!resampler) {
367                                 ret = -ENOMEM;
368                                 mutex_unlock(&kvm->irqfds.resampler_lock);
369                                 goto fail;
370                         }
371 
372                         resampler->kvm = kvm;
373                         INIT_LIST_HEAD(&resampler->list);
374                         resampler->notifier.gsi = irqfd->gsi;
375                         resampler->notifier.irq_acked = irqfd_resampler_ack;
376                         INIT_LIST_HEAD(&resampler->link);
377 
378                         list_add(&resampler->link, &kvm->irqfds.resampler_list);
379                         kvm_register_irq_ack_notifier(kvm,
380                                                       &resampler->notifier);
381                         irqfd->resampler = resampler;
382                 }
383 
384                 list_add_rcu(&irqfd->resampler_link, &irqfd->resampler->list);
385                 synchronize_srcu(&kvm->irq_srcu);
386 
387                 mutex_unlock(&kvm->irqfds.resampler_lock);
388         }
389 
390         /*
391          * Install our own custom wake-up handling so we are notified via
392          * a callback whenever someone signals the underlying eventfd
393          */
394         init_waitqueue_func_entry(&irqfd->wait, irqfd_wakeup);
395         init_poll_funcptr(&irqfd->pt, irqfd_ptable_queue_proc);
396 
397         spin_lock_irq(&kvm->irqfds.lock);
398 
399         ret = 0;
400         list_for_each_entry(tmp, &kvm->irqfds.items, list) {
401                 if (irqfd->eventfd != tmp->eventfd)
402                         continue;
403                 /* This fd is used for another irq already. */
404                 ret = -EBUSY;
405                 spin_unlock_irq(&kvm->irqfds.lock);
406                 goto fail;
407         }
408 
409         idx = srcu_read_lock(&kvm->irq_srcu);
410         irqfd_update(kvm, irqfd);
411         srcu_read_unlock(&kvm->irq_srcu, idx);
412 
413         list_add_tail(&irqfd->list, &kvm->irqfds.items);
414 
415         spin_unlock_irq(&kvm->irqfds.lock);
416 
417         /*
418          * Check if there was an event already pending on the eventfd
419          * before we registered, and trigger it as if we didn't miss it.
420          */
421         events = f.file->f_op->poll(f.file, &irqfd->pt);
422 
423         if (events & POLLIN)
424                 schedule_work(&irqfd->inject);
425 
426         /*
427          * do not drop the file until the irqfd is fully initialized, otherwise
428          * we might race against the POLLHUP
429          */
430         fdput(f);
431 
432         return 0;
433 
434 fail:
435         if (irqfd->resampler)
436                 irqfd_resampler_shutdown(irqfd);
437 
438         if (resamplefd && !IS_ERR(resamplefd))
439                 eventfd_ctx_put(resamplefd);
440 
441         if (eventfd && !IS_ERR(eventfd))
442                 eventfd_ctx_put(eventfd);
443 
444         fdput(f);
445 
446 out:
447         kfree(irqfd);
448         return ret;
449 }
450 
451 bool kvm_irq_has_notifier(struct kvm *kvm, unsigned irqchip, unsigned pin)
452 {
453         struct kvm_irq_ack_notifier *kian;
454         int gsi, idx;
455 
456         idx = srcu_read_lock(&kvm->irq_srcu);
457         gsi = kvm_irq_map_chip_pin(kvm, irqchip, pin);
458         if (gsi != -1)
459                 hlist_for_each_entry_rcu(kian, &kvm->irq_ack_notifier_list,
460                                          link)
461                         if (kian->gsi == gsi) {
462                                 srcu_read_unlock(&kvm->irq_srcu, idx);
463                                 return true;
464                         }
465 
466         srcu_read_unlock(&kvm->irq_srcu, idx);
467 
468         return false;
469 }
470 EXPORT_SYMBOL_GPL(kvm_irq_has_notifier);
471 
472 void kvm_notify_acked_irq(struct kvm *kvm, unsigned irqchip, unsigned pin)
473 {
474         struct kvm_irq_ack_notifier *kian;
475         int gsi, idx;
476 
477         trace_kvm_ack_irq(irqchip, pin);
478 
479         idx = srcu_read_lock(&kvm->irq_srcu);
480         gsi = kvm_irq_map_chip_pin(kvm, irqchip, pin);
481         if (gsi != -1)
482                 hlist_for_each_entry_rcu(kian, &kvm->irq_ack_notifier_list,
483                                          link)
484                         if (kian->gsi == gsi)
485                                 kian->irq_acked(kian);
486         srcu_read_unlock(&kvm->irq_srcu, idx);
487 }
488 
489 void kvm_register_irq_ack_notifier(struct kvm *kvm,
490                                    struct kvm_irq_ack_notifier *kian)
491 {
492         mutex_lock(&kvm->irq_lock);
493         hlist_add_head_rcu(&kian->link, &kvm->irq_ack_notifier_list);
494         mutex_unlock(&kvm->irq_lock);
495         kvm_vcpu_request_scan_ioapic(kvm);
496 }
497 
498 void kvm_unregister_irq_ack_notifier(struct kvm *kvm,
499                                     struct kvm_irq_ack_notifier *kian)
500 {
501         mutex_lock(&kvm->irq_lock);
502         hlist_del_init_rcu(&kian->link);
503         mutex_unlock(&kvm->irq_lock);
504         synchronize_srcu(&kvm->irq_srcu);
505         kvm_vcpu_request_scan_ioapic(kvm);
506 }
507 #endif
508 
509 void
510 kvm_eventfd_init(struct kvm *kvm)
511 {
512 #ifdef CONFIG_HAVE_KVM_IRQFD
513         spin_lock_init(&kvm->irqfds.lock);
514         INIT_LIST_HEAD(&kvm->irqfds.items);
515         INIT_LIST_HEAD(&kvm->irqfds.resampler_list);
516         mutex_init(&kvm->irqfds.resampler_lock);
517 #endif
518         INIT_LIST_HEAD(&kvm->ioeventfds);
519 }
520 
521 #ifdef CONFIG_HAVE_KVM_IRQFD
522 /*
523  * shutdown any irqfd's that match fd+gsi
524  */
525 static int
526 kvm_irqfd_deassign(struct kvm *kvm, struct kvm_irqfd *args)
527 {
528         struct _irqfd *irqfd, *tmp;
529         struct eventfd_ctx *eventfd;
530 
531         eventfd = eventfd_ctx_fdget(args->fd);
532         if (IS_ERR(eventfd))
533                 return PTR_ERR(eventfd);
534 
535         spin_lock_irq(&kvm->irqfds.lock);
536 
537         list_for_each_entry_safe(irqfd, tmp, &kvm->irqfds.items, list) {
538                 if (irqfd->eventfd == eventfd && irqfd->gsi == args->gsi) {
539                         /*
540                          * This clearing of irq_entry.type is needed for when
541                          * another thread calls kvm_irq_routing_update before
542                          * we flush workqueue below (we synchronize with
543                          * kvm_irq_routing_update using irqfds.lock).
544                          */
545                         write_seqcount_begin(&irqfd->irq_entry_sc);
546                         irqfd->irq_entry.type = 0;
547                         write_seqcount_end(&irqfd->irq_entry_sc);
548                         irqfd_deactivate(irqfd);
549                 }
550         }
551 
552         spin_unlock_irq(&kvm->irqfds.lock);
553         eventfd_ctx_put(eventfd);
554 
555         /*
556          * Block until we know all outstanding shutdown jobs have completed
557          * so that we guarantee there will not be any more interrupts on this
558          * gsi once this deassign function returns.
559          */
560         flush_workqueue(irqfd_cleanup_wq);
561 
562         return 0;
563 }
564 
565 int
566 kvm_irqfd(struct kvm *kvm, struct kvm_irqfd *args)
567 {
568         if (args->flags & ~(KVM_IRQFD_FLAG_DEASSIGN | KVM_IRQFD_FLAG_RESAMPLE))
569                 return -EINVAL;
570 
571         if (args->flags & KVM_IRQFD_FLAG_DEASSIGN)
572                 return kvm_irqfd_deassign(kvm, args);
573 
574         return kvm_irqfd_assign(kvm, args);
575 }
576 
577 /*
578  * This function is called as the kvm VM fd is being released. Shutdown all
579  * irqfds that still remain open
580  */
581 void
582 kvm_irqfd_release(struct kvm *kvm)
583 {
584         struct _irqfd *irqfd, *tmp;
585 
586         spin_lock_irq(&kvm->irqfds.lock);
587 
588         list_for_each_entry_safe(irqfd, tmp, &kvm->irqfds.items, list)
589                 irqfd_deactivate(irqfd);
590 
591         spin_unlock_irq(&kvm->irqfds.lock);
592 
593         /*
594          * Block until we know all outstanding shutdown jobs have completed
595          * since we do not take a kvm* reference.
596          */
597         flush_workqueue(irqfd_cleanup_wq);
598 
599 }
600 
601 /*
602  * Take note of a change in irq routing.
603  * Caller must invoke synchronize_srcu(&kvm->irq_srcu) afterwards.
604  */
605 void kvm_irq_routing_update(struct kvm *kvm)
606 {
607         struct _irqfd *irqfd;
608 
609         spin_lock_irq(&kvm->irqfds.lock);
610 
611         list_for_each_entry(irqfd, &kvm->irqfds.items, list)
612                 irqfd_update(kvm, irqfd);
613 
614         spin_unlock_irq(&kvm->irqfds.lock);
615 }
616 
617 /*
618  * create a host-wide workqueue for issuing deferred shutdown requests
619  * aggregated from all vm* instances. We need our own isolated single-thread
620  * queue to prevent deadlock against flushing the normal work-queue.
621  */
622 int kvm_irqfd_init(void)
623 {
624         irqfd_cleanup_wq = create_singlethread_workqueue("kvm-irqfd-cleanup");
625         if (!irqfd_cleanup_wq)
626                 return -ENOMEM;
627 
628         return 0;
629 }
630 
631 void kvm_irqfd_exit(void)
632 {
633         destroy_workqueue(irqfd_cleanup_wq);
634 }
635 #endif
636 
637 /*
638  * --------------------------------------------------------------------
639  * ioeventfd: translate a PIO/MMIO memory write to an eventfd signal.
640  *
641  * userspace can register a PIO/MMIO address with an eventfd for receiving
642  * notification when the memory has been touched.
643  * --------------------------------------------------------------------
644  */
645 
646 struct _ioeventfd {
647         struct list_head     list;
648         u64                  addr;
649         int                  length;
650         struct eventfd_ctx  *eventfd;
651         u64                  datamatch;
652         struct kvm_io_device dev;
653         u8                   bus_idx;
654         bool                 wildcard;
655 };
656 
657 static inline struct _ioeventfd *
658 to_ioeventfd(struct kvm_io_device *dev)
659 {
660         return container_of(dev, struct _ioeventfd, dev);
661 }
662 
663 static void
664 ioeventfd_release(struct _ioeventfd *p)
665 {
666         eventfd_ctx_put(p->eventfd);
667         list_del(&p->list);
668         kfree(p);
669 }
670 
671 static bool
672 ioeventfd_in_range(struct _ioeventfd *p, gpa_t addr, int len, const void *val)
673 {
674         u64 _val;
675 
676         if (addr != p->addr)
677                 /* address must be precise for a hit */
678                 return false;
679 
680         if (!p->length)
681                 /* length = 0 means only look at the address, so always a hit */
682                 return true;
683 
684         if (len != p->length)
685                 /* address-range must be precise for a hit */
686                 return false;
687 
688         if (p->wildcard)
689                 /* all else equal, wildcard is always a hit */
690                 return true;
691 
692         /* otherwise, we have to actually compare the data */
693 
694         BUG_ON(!IS_ALIGNED((unsigned long)val, len));
695 
696         switch (len) {
697         case 1:
698                 _val = *(u8 *)val;
699                 break;
700         case 2:
701                 _val = *(u16 *)val;
702                 break;
703         case 4:
704                 _val = *(u32 *)val;
705                 break;
706         case 8:
707                 _val = *(u64 *)val;
708                 break;
709         default:
710                 return false;
711         }
712 
713         return _val == p->datamatch ? true : false;
714 }
715 
716 /* MMIO/PIO writes trigger an event if the addr/val match */
717 static int
718 ioeventfd_write(struct kvm_vcpu *vcpu, struct kvm_io_device *this, gpa_t addr,
719                 int len, const void *val)
720 {
721         struct _ioeventfd *p = to_ioeventfd(this);
722 
723         if (!ioeventfd_in_range(p, addr, len, val))
724                 return -EOPNOTSUPP;
725 
726         eventfd_signal(p->eventfd, 1);
727         return 0;
728 }
729 
730 /*
731  * This function is called as KVM is completely shutting down.  We do not
732  * need to worry about locking just nuke anything we have as quickly as possible
733  */
734 static void
735 ioeventfd_destructor(struct kvm_io_device *this)
736 {
737         struct _ioeventfd *p = to_ioeventfd(this);
738 
739         ioeventfd_release(p);
740 }
741 
742 static const struct kvm_io_device_ops ioeventfd_ops = {
743         .write      = ioeventfd_write,
744         .destructor = ioeventfd_destructor,
745 };
746 
747 /* assumes kvm->slots_lock held */
748 static bool
749 ioeventfd_check_collision(struct kvm *kvm, struct _ioeventfd *p)
750 {
751         struct _ioeventfd *_p;
752 
753         list_for_each_entry(_p, &kvm->ioeventfds, list)
754                 if (_p->bus_idx == p->bus_idx &&
755                     _p->addr == p->addr &&
756                     (!_p->length || !p->length ||
757                      (_p->length == p->length &&
758                       (_p->wildcard || p->wildcard ||
759                        _p->datamatch == p->datamatch))))
760                         return true;
761 
762         return false;
763 }
764 
765 static enum kvm_bus ioeventfd_bus_from_flags(__u32 flags)
766 {
767         if (flags & KVM_IOEVENTFD_FLAG_PIO)
768                 return KVM_PIO_BUS;
769         if (flags & KVM_IOEVENTFD_FLAG_VIRTIO_CCW_NOTIFY)
770                 return KVM_VIRTIO_CCW_NOTIFY_BUS;
771         return KVM_MMIO_BUS;
772 }
773 
774 static int kvm_assign_ioeventfd_idx(struct kvm *kvm,
775                                 enum kvm_bus bus_idx,
776                                 struct kvm_ioeventfd *args)
777 {
778 
779         struct eventfd_ctx *eventfd;
780         struct _ioeventfd *p;
781         int ret;
782 
783         eventfd = eventfd_ctx_fdget(args->fd);
784         if (IS_ERR(eventfd))
785                 return PTR_ERR(eventfd);
786 
787         p = kzalloc(sizeof(*p), GFP_KERNEL);
788         if (!p) {
789                 ret = -ENOMEM;
790                 goto fail;
791         }
792 
793         INIT_LIST_HEAD(&p->list);
794         p->addr    = args->addr;
795         p->bus_idx = bus_idx;
796         p->length  = args->len;
797         p->eventfd = eventfd;
798 
799         /* The datamatch feature is optional, otherwise this is a wildcard */
800         if (args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH)
801                 p->datamatch = args->datamatch;
802         else
803                 p->wildcard = true;
804 
805         mutex_lock(&kvm->slots_lock);
806 
807         /* Verify that there isn't a match already */
808         if (ioeventfd_check_collision(kvm, p)) {
809                 ret = -EEXIST;
810                 goto unlock_fail;
811         }
812 
813         kvm_iodevice_init(&p->dev, &ioeventfd_ops);
814 
815         ret = kvm_io_bus_register_dev(kvm, bus_idx, p->addr, p->length,
816                                       &p->dev);
817         if (ret < 0)
818                 goto unlock_fail;
819 
820         kvm->buses[bus_idx]->ioeventfd_count++;
821         list_add_tail(&p->list, &kvm->ioeventfds);
822 
823         mutex_unlock(&kvm->slots_lock);
824 
825         return 0;
826 
827 unlock_fail:
828         mutex_unlock(&kvm->slots_lock);
829 
830 fail:
831         kfree(p);
832         eventfd_ctx_put(eventfd);
833 
834         return ret;
835 }
836 
837 static int
838 kvm_deassign_ioeventfd_idx(struct kvm *kvm, enum kvm_bus bus_idx,
839                            struct kvm_ioeventfd *args)
840 {
841         struct _ioeventfd        *p, *tmp;
842         struct eventfd_ctx       *eventfd;
843         int                       ret = -ENOENT;
844 
845         eventfd = eventfd_ctx_fdget(args->fd);
846         if (IS_ERR(eventfd))
847                 return PTR_ERR(eventfd);
848 
849         mutex_lock(&kvm->slots_lock);
850 
851         list_for_each_entry_safe(p, tmp, &kvm->ioeventfds, list) {
852                 bool wildcard = !(args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH);
853 
854                 if (p->bus_idx != bus_idx ||
855                     p->eventfd != eventfd  ||
856                     p->addr != args->addr  ||
857                     p->length != args->len ||
858                     p->wildcard != wildcard)
859                         continue;
860 
861                 if (!p->wildcard && p->datamatch != args->datamatch)
862                         continue;
863 
864                 kvm_io_bus_unregister_dev(kvm, bus_idx, &p->dev);
865                 kvm->buses[bus_idx]->ioeventfd_count--;
866                 ioeventfd_release(p);
867                 ret = 0;
868                 break;
869         }
870 
871         mutex_unlock(&kvm->slots_lock);
872 
873         eventfd_ctx_put(eventfd);
874 
875         return ret;
876 }
877 
878 static int kvm_deassign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
879 {
880         enum kvm_bus bus_idx = ioeventfd_bus_from_flags(args->flags);
881         int ret = kvm_deassign_ioeventfd_idx(kvm, bus_idx, args);
882 
883         if (!args->len && bus_idx == KVM_MMIO_BUS)
884                 kvm_deassign_ioeventfd_idx(kvm, KVM_FAST_MMIO_BUS, args);
885 
886         return ret;
887 }
888 
889 static int
890 kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
891 {
892         enum kvm_bus              bus_idx;
893         int ret;
894 
895         bus_idx = ioeventfd_bus_from_flags(args->flags);
896         /* must be natural-word sized, or 0 to ignore length */
897         switch (args->len) {
898         case 0:
899         case 1:
900         case 2:
901         case 4:
902         case 8:
903                 break;
904         default:
905                 return -EINVAL;
906         }
907 
908         /* check for range overflow */
909         if (args->addr + args->len < args->addr)
910                 return -EINVAL;
911 
912         /* check for extra flags that we don't understand */
913         if (args->flags & ~KVM_IOEVENTFD_VALID_FLAG_MASK)
914                 return -EINVAL;
915 
916         /* ioeventfd with no length can't be combined with DATAMATCH */
917         if (!args->len &&
918             args->flags & (KVM_IOEVENTFD_FLAG_PIO |
919                            KVM_IOEVENTFD_FLAG_DATAMATCH))
920                 return -EINVAL;
921 
922         ret = kvm_assign_ioeventfd_idx(kvm, bus_idx, args);
923         if (ret)
924                 goto fail;
925 
926         /* When length is ignored, MMIO is also put on a separate bus, for
927          * faster lookups.
928          */
929         if (!args->len && bus_idx == KVM_MMIO_BUS) {
930                 ret = kvm_assign_ioeventfd_idx(kvm, KVM_FAST_MMIO_BUS, args);
931                 if (ret < 0)
932                         goto fast_fail;
933         }
934 
935         return 0;
936 
937 fast_fail:
938         kvm_deassign_ioeventfd_idx(kvm, bus_idx, args);
939 fail:
940         return ret;
941 }
942 
943 int
944 kvm_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
945 {
946         if (args->flags & KVM_IOEVENTFD_FLAG_DEASSIGN)
947                 return kvm_deassign_ioeventfd(kvm, args);
948 
949         return kvm_assign_ioeventfd(kvm, args);
950 }
951 

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