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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/kvm_irqfd.h>
 27 #include <linux/workqueue.h>
 28 #include <linux/syscalls.h>
 29 #include <linux/wait.h>
 30 #include <linux/poll.h>
 31 #include <linux/file.h>
 32 #include <linux/list.h>
 33 #include <linux/eventfd.h>
 34 #include <linux/kernel.h>
 35 #include <linux/srcu.h>
 36 #include <linux/slab.h>
 37 #include <linux/seqlock.h>
 38 #include <linux/irqbypass.h>
 39 #include <trace/events/kvm.h>
 40 
 41 #include <kvm/iodev.h>
 42 
 43 #ifdef CONFIG_HAVE_KVM_IRQFD
 44 
 45 static struct workqueue_struct *irqfd_cleanup_wq;
 46 
 47 static void
 48 irqfd_inject(struct work_struct *work)
 49 {
 50         struct kvm_kernel_irqfd *irqfd =
 51                 container_of(work, struct kvm_kernel_irqfd, inject);
 52         struct kvm *kvm = irqfd->kvm;
 53 
 54         if (!irqfd->resampler) {
 55                 kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 1,
 56                                 false);
 57                 kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 0,
 58                                 false);
 59         } else
 60                 kvm_set_irq(kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
 61                             irqfd->gsi, 1, false);
 62 }
 63 
 64 /*
 65  * Since resampler irqfds share an IRQ source ID, we de-assert once
 66  * then notify all of the resampler irqfds using this GSI.  We can't
 67  * do multiple de-asserts or we risk racing with incoming re-asserts.
 68  */
 69 static void
 70 irqfd_resampler_ack(struct kvm_irq_ack_notifier *kian)
 71 {
 72         struct kvm_kernel_irqfd_resampler *resampler;
 73         struct kvm *kvm;
 74         struct kvm_kernel_irqfd *irqfd;
 75         int idx;
 76 
 77         resampler = container_of(kian,
 78                         struct kvm_kernel_irqfd_resampler, notifier);
 79         kvm = resampler->kvm;
 80 
 81         kvm_set_irq(kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
 82                     resampler->notifier.gsi, 0, false);
 83 
 84         idx = srcu_read_lock(&kvm->irq_srcu);
 85 
 86         list_for_each_entry_rcu(irqfd, &resampler->list, resampler_link)
 87                 eventfd_signal(irqfd->resamplefd, 1);
 88 
 89         srcu_read_unlock(&kvm->irq_srcu, idx);
 90 }
 91 
 92 static void
 93 irqfd_resampler_shutdown(struct kvm_kernel_irqfd *irqfd)
 94 {
 95         struct kvm_kernel_irqfd_resampler *resampler = irqfd->resampler;
 96         struct kvm *kvm = resampler->kvm;
 97 
 98         mutex_lock(&kvm->irqfds.resampler_lock);
 99 
100         list_del_rcu(&irqfd->resampler_link);
101         synchronize_srcu(&kvm->irq_srcu);
102 
103         if (list_empty(&resampler->list)) {
104                 list_del(&resampler->link);
105                 kvm_unregister_irq_ack_notifier(kvm, &resampler->notifier);
106                 kvm_set_irq(kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
107                             resampler->notifier.gsi, 0, false);
108                 kfree(resampler);
109         }
110 
111         mutex_unlock(&kvm->irqfds.resampler_lock);
112 }
113 
114 /*
115  * Race-free decouple logic (ordering is critical)
116  */
117 static void
118 irqfd_shutdown(struct work_struct *work)
119 {
120         struct kvm_kernel_irqfd *irqfd =
121                 container_of(work, struct kvm_kernel_irqfd, shutdown);
122         struct kvm *kvm = irqfd->kvm;
123         u64 cnt;
124 
125         /* Make sure irqfd has been initalized in assign path. */
126         synchronize_srcu(&kvm->irq_srcu);
127 
128         /*
129          * Synchronize with the wait-queue and unhook ourselves to prevent
130          * further events.
131          */
132         eventfd_ctx_remove_wait_queue(irqfd->eventfd, &irqfd->wait, &cnt);
133 
134         /*
135          * We know no new events will be scheduled at this point, so block
136          * until all previously outstanding events have completed
137          */
138         flush_work(&irqfd->inject);
139 
140         if (irqfd->resampler) {
141                 irqfd_resampler_shutdown(irqfd);
142                 eventfd_ctx_put(irqfd->resamplefd);
143         }
144 
145         /*
146          * It is now safe to release the object's resources
147          */
148 #ifdef CONFIG_HAVE_KVM_IRQ_BYPASS
149         irq_bypass_unregister_consumer(&irqfd->consumer);
150 #endif
151         eventfd_ctx_put(irqfd->eventfd);
152         kfree(irqfd);
153 }
154 
155 
156 /* assumes kvm->irqfds.lock is held */
157 static bool
158 irqfd_is_active(struct kvm_kernel_irqfd *irqfd)
159 {
160         return list_empty(&irqfd->list) ? false : true;
161 }
162 
163 /*
164  * Mark the irqfd as inactive and schedule it for removal
165  *
166  * assumes kvm->irqfds.lock is held
167  */
168 static void
169 irqfd_deactivate(struct kvm_kernel_irqfd *irqfd)
170 {
171         BUG_ON(!irqfd_is_active(irqfd));
172 
173         list_del_init(&irqfd->list);
174 
175         queue_work(irqfd_cleanup_wq, &irqfd->shutdown);
176 }
177 
178 int __attribute__((weak)) kvm_arch_set_irq_inatomic(
179                                 struct kvm_kernel_irq_routing_entry *irq,
180                                 struct kvm *kvm, int irq_source_id,
181                                 int level,
182                                 bool line_status)
183 {
184         return -EWOULDBLOCK;
185 }
186 
187 /*
188  * Called with wqh->lock held and interrupts disabled
189  */
190 static int
191 irqfd_wakeup(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
192 {
193         struct kvm_kernel_irqfd *irqfd =
194                 container_of(wait, struct kvm_kernel_irqfd, wait);
195         __poll_t flags = key_to_poll(key);
196         struct kvm_kernel_irq_routing_entry irq;
197         struct kvm *kvm = irqfd->kvm;
198         unsigned seq;
199         int idx;
200 
201         if (flags & EPOLLIN) {
202                 idx = srcu_read_lock(&kvm->irq_srcu);
203                 do {
204                         seq = read_seqcount_begin(&irqfd->irq_entry_sc);
205                         irq = irqfd->irq_entry;
206                 } while (read_seqcount_retry(&irqfd->irq_entry_sc, seq));
207                 /* An event has been signaled, inject an interrupt */
208                 if (kvm_arch_set_irq_inatomic(&irq, kvm,
209                                               KVM_USERSPACE_IRQ_SOURCE_ID, 1,
210                                               false) == -EWOULDBLOCK)
211                         schedule_work(&irqfd->inject);
212                 srcu_read_unlock(&kvm->irq_srcu, idx);
213         }
214 
215         if (flags & EPOLLHUP) {
216                 /* The eventfd is closing, detach from KVM */
217                 unsigned long flags;
218 
219                 spin_lock_irqsave(&kvm->irqfds.lock, flags);
220 
221                 /*
222                  * We must check if someone deactivated the irqfd before
223                  * we could acquire the irqfds.lock since the item is
224                  * deactivated from the KVM side before it is unhooked from
225                  * the wait-queue.  If it is already deactivated, we can
226                  * simply return knowing the other side will cleanup for us.
227                  * We cannot race against the irqfd going away since the
228                  * other side is required to acquire wqh->lock, which we hold
229                  */
230                 if (irqfd_is_active(irqfd))
231                         irqfd_deactivate(irqfd);
232 
233                 spin_unlock_irqrestore(&kvm->irqfds.lock, flags);
234         }
235 
236         return 0;
237 }
238 
239 static void
240 irqfd_ptable_queue_proc(struct file *file, wait_queue_head_t *wqh,
241                         poll_table *pt)
242 {
243         struct kvm_kernel_irqfd *irqfd =
244                 container_of(pt, struct kvm_kernel_irqfd, pt);
245         add_wait_queue(wqh, &irqfd->wait);
246 }
247 
248 /* Must be called under irqfds.lock */
249 static void irqfd_update(struct kvm *kvm, struct kvm_kernel_irqfd *irqfd)
250 {
251         struct kvm_kernel_irq_routing_entry *e;
252         struct kvm_kernel_irq_routing_entry entries[KVM_NR_IRQCHIPS];
253         int n_entries;
254 
255         n_entries = kvm_irq_map_gsi(kvm, entries, irqfd->gsi);
256 
257         write_seqcount_begin(&irqfd->irq_entry_sc);
258 
259         e = entries;
260         if (n_entries == 1)
261                 irqfd->irq_entry = *e;
262         else
263                 irqfd->irq_entry.type = 0;
264 
265         write_seqcount_end(&irqfd->irq_entry_sc);
266 }
267 
268 #ifdef CONFIG_HAVE_KVM_IRQ_BYPASS
269 void __attribute__((weak)) kvm_arch_irq_bypass_stop(
270                                 struct irq_bypass_consumer *cons)
271 {
272 }
273 
274 void __attribute__((weak)) kvm_arch_irq_bypass_start(
275                                 struct irq_bypass_consumer *cons)
276 {
277 }
278 
279 int  __attribute__((weak)) kvm_arch_update_irqfd_routing(
280                                 struct kvm *kvm, unsigned int host_irq,
281                                 uint32_t guest_irq, bool set)
282 {
283         return 0;
284 }
285 #endif
286 
287 static int
288 kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args)
289 {
290         struct kvm_kernel_irqfd *irqfd, *tmp;
291         struct fd f;
292         struct eventfd_ctx *eventfd = NULL, *resamplefd = NULL;
293         int ret;
294         __poll_t events;
295         int idx;
296 
297         if (!kvm_arch_intc_initialized(kvm))
298                 return -EAGAIN;
299 
300         irqfd = kzalloc(sizeof(*irqfd), GFP_KERNEL);
301         if (!irqfd)
302                 return -ENOMEM;
303 
304         irqfd->kvm = kvm;
305         irqfd->gsi = args->gsi;
306         INIT_LIST_HEAD(&irqfd->list);
307         INIT_WORK(&irqfd->inject, irqfd_inject);
308         INIT_WORK(&irqfd->shutdown, irqfd_shutdown);
309         seqcount_init(&irqfd->irq_entry_sc);
310 
311         f = fdget(args->fd);
312         if (!f.file) {
313                 ret = -EBADF;
314                 goto out;
315         }
316 
317         eventfd = eventfd_ctx_fileget(f.file);
318         if (IS_ERR(eventfd)) {
319                 ret = PTR_ERR(eventfd);
320                 goto fail;
321         }
322 
323         irqfd->eventfd = eventfd;
324 
325         if (args->flags & KVM_IRQFD_FLAG_RESAMPLE) {
326                 struct kvm_kernel_irqfd_resampler *resampler;
327 
328                 resamplefd = eventfd_ctx_fdget(args->resamplefd);
329                 if (IS_ERR(resamplefd)) {
330                         ret = PTR_ERR(resamplefd);
331                         goto fail;
332                 }
333 
334                 irqfd->resamplefd = resamplefd;
335                 INIT_LIST_HEAD(&irqfd->resampler_link);
336 
337                 mutex_lock(&kvm->irqfds.resampler_lock);
338 
339                 list_for_each_entry(resampler,
340                                     &kvm->irqfds.resampler_list, link) {
341                         if (resampler->notifier.gsi == irqfd->gsi) {
342                                 irqfd->resampler = resampler;
343                                 break;
344                         }
345                 }
346 
347                 if (!irqfd->resampler) {
348                         resampler = kzalloc(sizeof(*resampler), GFP_KERNEL);
349                         if (!resampler) {
350                                 ret = -ENOMEM;
351                                 mutex_unlock(&kvm->irqfds.resampler_lock);
352                                 goto fail;
353                         }
354 
355                         resampler->kvm = kvm;
356                         INIT_LIST_HEAD(&resampler->list);
357                         resampler->notifier.gsi = irqfd->gsi;
358                         resampler->notifier.irq_acked = irqfd_resampler_ack;
359                         INIT_LIST_HEAD(&resampler->link);
360 
361                         list_add(&resampler->link, &kvm->irqfds.resampler_list);
362                         kvm_register_irq_ack_notifier(kvm,
363                                                       &resampler->notifier);
364                         irqfd->resampler = resampler;
365                 }
366 
367                 list_add_rcu(&irqfd->resampler_link, &irqfd->resampler->list);
368                 synchronize_srcu(&kvm->irq_srcu);
369 
370                 mutex_unlock(&kvm->irqfds.resampler_lock);
371         }
372 
373         /*
374          * Install our own custom wake-up handling so we are notified via
375          * a callback whenever someone signals the underlying eventfd
376          */
377         init_waitqueue_func_entry(&irqfd->wait, irqfd_wakeup);
378         init_poll_funcptr(&irqfd->pt, irqfd_ptable_queue_proc);
379 
380         spin_lock_irq(&kvm->irqfds.lock);
381 
382         ret = 0;
383         list_for_each_entry(tmp, &kvm->irqfds.items, list) {
384                 if (irqfd->eventfd != tmp->eventfd)
385                         continue;
386                 /* This fd is used for another irq already. */
387                 ret = -EBUSY;
388                 spin_unlock_irq(&kvm->irqfds.lock);
389                 goto fail;
390         }
391 
392         idx = srcu_read_lock(&kvm->irq_srcu);
393         irqfd_update(kvm, irqfd);
394 
395         list_add_tail(&irqfd->list, &kvm->irqfds.items);
396 
397         spin_unlock_irq(&kvm->irqfds.lock);
398 
399         /*
400          * Check if there was an event already pending on the eventfd
401          * before we registered, and trigger it as if we didn't miss it.
402          */
403         events = vfs_poll(f.file, &irqfd->pt);
404 
405         if (events & EPOLLIN)
406                 schedule_work(&irqfd->inject);
407 
408 #ifdef CONFIG_HAVE_KVM_IRQ_BYPASS
409         if (kvm_arch_has_irq_bypass()) {
410                 irqfd->consumer.token = (void *)irqfd->eventfd;
411                 irqfd->consumer.add_producer = kvm_arch_irq_bypass_add_producer;
412                 irqfd->consumer.del_producer = kvm_arch_irq_bypass_del_producer;
413                 irqfd->consumer.stop = kvm_arch_irq_bypass_stop;
414                 irqfd->consumer.start = kvm_arch_irq_bypass_start;
415                 ret = irq_bypass_register_consumer(&irqfd->consumer);
416                 if (ret)
417                         pr_info("irq bypass consumer (token %p) registration fails: %d\n",
418                                 irqfd->consumer.token, ret);
419         }
420 #endif
421 
422         srcu_read_unlock(&kvm->irq_srcu, idx);
423 
424         /*
425          * do not drop the file until the irqfd is fully initialized, otherwise
426          * we might race against the EPOLLHUP
427          */
428         fdput(f);
429         return 0;
430 
431 fail:
432         if (irqfd->resampler)
433                 irqfd_resampler_shutdown(irqfd);
434 
435         if (resamplefd && !IS_ERR(resamplefd))
436                 eventfd_ctx_put(resamplefd);
437 
438         if (eventfd && !IS_ERR(eventfd))
439                 eventfd_ctx_put(eventfd);
440 
441         fdput(f);
442 
443 out:
444         kfree(irqfd);
445         return ret;
446 }
447 
448 bool kvm_irq_has_notifier(struct kvm *kvm, unsigned irqchip, unsigned pin)
449 {
450         struct kvm_irq_ack_notifier *kian;
451         int gsi, idx;
452 
453         idx = srcu_read_lock(&kvm->irq_srcu);
454         gsi = kvm_irq_map_chip_pin(kvm, irqchip, pin);
455         if (gsi != -1)
456                 hlist_for_each_entry_rcu(kian, &kvm->irq_ack_notifier_list,
457                                          link)
458                         if (kian->gsi == gsi) {
459                                 srcu_read_unlock(&kvm->irq_srcu, idx);
460                                 return true;
461                         }
462 
463         srcu_read_unlock(&kvm->irq_srcu, idx);
464 
465         return false;
466 }
467 EXPORT_SYMBOL_GPL(kvm_irq_has_notifier);
468 
469 void kvm_notify_acked_gsi(struct kvm *kvm, int gsi)
470 {
471         struct kvm_irq_ack_notifier *kian;
472 
473         hlist_for_each_entry_rcu(kian, &kvm->irq_ack_notifier_list,
474                                  link)
475                 if (kian->gsi == gsi)
476                         kian->irq_acked(kian);
477 }
478 
479 void kvm_notify_acked_irq(struct kvm *kvm, unsigned irqchip, unsigned pin)
480 {
481         int gsi, idx;
482 
483         trace_kvm_ack_irq(irqchip, pin);
484 
485         idx = srcu_read_lock(&kvm->irq_srcu);
486         gsi = kvm_irq_map_chip_pin(kvm, irqchip, pin);
487         if (gsi != -1)
488                 kvm_notify_acked_gsi(kvm, gsi);
489         srcu_read_unlock(&kvm->irq_srcu, idx);
490 }
491 
492 void kvm_register_irq_ack_notifier(struct kvm *kvm,
493                                    struct kvm_irq_ack_notifier *kian)
494 {
495         mutex_lock(&kvm->irq_lock);
496         hlist_add_head_rcu(&kian->link, &kvm->irq_ack_notifier_list);
497         mutex_unlock(&kvm->irq_lock);
498         kvm_arch_post_irq_ack_notifier_list_update(kvm);
499 }
500 
501 void kvm_unregister_irq_ack_notifier(struct kvm *kvm,
502                                     struct kvm_irq_ack_notifier *kian)
503 {
504         mutex_lock(&kvm->irq_lock);
505         hlist_del_init_rcu(&kian->link);
506         mutex_unlock(&kvm->irq_lock);
507         synchronize_srcu(&kvm->irq_srcu);
508         kvm_arch_post_irq_ack_notifier_list_update(kvm);
509 }
510 #endif
511 
512 void
513 kvm_eventfd_init(struct kvm *kvm)
514 {
515 #ifdef CONFIG_HAVE_KVM_IRQFD
516         spin_lock_init(&kvm->irqfds.lock);
517         INIT_LIST_HEAD(&kvm->irqfds.items);
518         INIT_LIST_HEAD(&kvm->irqfds.resampler_list);
519         mutex_init(&kvm->irqfds.resampler_lock);
520 #endif
521         INIT_LIST_HEAD(&kvm->ioeventfds);
522 }
523 
524 #ifdef CONFIG_HAVE_KVM_IRQFD
525 /*
526  * shutdown any irqfd's that match fd+gsi
527  */
528 static int
529 kvm_irqfd_deassign(struct kvm *kvm, struct kvm_irqfd *args)
530 {
531         struct kvm_kernel_irqfd *irqfd, *tmp;
532         struct eventfd_ctx *eventfd;
533 
534         eventfd = eventfd_ctx_fdget(args->fd);
535         if (IS_ERR(eventfd))
536                 return PTR_ERR(eventfd);
537 
538         spin_lock_irq(&kvm->irqfds.lock);
539 
540         list_for_each_entry_safe(irqfd, tmp, &kvm->irqfds.items, list) {
541                 if (irqfd->eventfd == eventfd && irqfd->gsi == args->gsi) {
542                         /*
543                          * This clearing of irq_entry.type is needed for when
544                          * another thread calls kvm_irq_routing_update before
545                          * we flush workqueue below (we synchronize with
546                          * kvm_irq_routing_update using irqfds.lock).
547                          */
548                         write_seqcount_begin(&irqfd->irq_entry_sc);
549                         irqfd->irq_entry.type = 0;
550                         write_seqcount_end(&irqfd->irq_entry_sc);
551                         irqfd_deactivate(irqfd);
552                 }
553         }
554 
555         spin_unlock_irq(&kvm->irqfds.lock);
556         eventfd_ctx_put(eventfd);
557 
558         /*
559          * Block until we know all outstanding shutdown jobs have completed
560          * so that we guarantee there will not be any more interrupts on this
561          * gsi once this deassign function returns.
562          */
563         flush_workqueue(irqfd_cleanup_wq);
564 
565         return 0;
566 }
567 
568 int
569 kvm_irqfd(struct kvm *kvm, struct kvm_irqfd *args)
570 {
571         if (args->flags & ~(KVM_IRQFD_FLAG_DEASSIGN | KVM_IRQFD_FLAG_RESAMPLE))
572                 return -EINVAL;
573 
574         if (args->flags & KVM_IRQFD_FLAG_DEASSIGN)
575                 return kvm_irqfd_deassign(kvm, args);
576 
577         return kvm_irqfd_assign(kvm, args);
578 }
579 
580 /*
581  * This function is called as the kvm VM fd is being released. Shutdown all
582  * irqfds that still remain open
583  */
584 void
585 kvm_irqfd_release(struct kvm *kvm)
586 {
587         struct kvm_kernel_irqfd *irqfd, *tmp;
588 
589         spin_lock_irq(&kvm->irqfds.lock);
590 
591         list_for_each_entry_safe(irqfd, tmp, &kvm->irqfds.items, list)
592                 irqfd_deactivate(irqfd);
593 
594         spin_unlock_irq(&kvm->irqfds.lock);
595 
596         /*
597          * Block until we know all outstanding shutdown jobs have completed
598          * since we do not take a kvm* reference.
599          */
600         flush_workqueue(irqfd_cleanup_wq);
601 
602 }
603 
604 /*
605  * Take note of a change in irq routing.
606  * Caller must invoke synchronize_srcu(&kvm->irq_srcu) afterwards.
607  */
608 void kvm_irq_routing_update(struct kvm *kvm)
609 {
610         struct kvm_kernel_irqfd *irqfd;
611 
612         spin_lock_irq(&kvm->irqfds.lock);
613 
614         list_for_each_entry(irqfd, &kvm->irqfds.items, list) {
615                 irqfd_update(kvm, irqfd);
616 
617 #ifdef CONFIG_HAVE_KVM_IRQ_BYPASS
618                 if (irqfd->producer) {
619                         int ret = kvm_arch_update_irqfd_routing(
620                                         irqfd->kvm, irqfd->producer->irq,
621                                         irqfd->gsi, 1);
622                         WARN_ON(ret);
623                 }
624 #endif
625         }
626 
627         spin_unlock_irq(&kvm->irqfds.lock);
628 }
629 
630 /*
631  * create a host-wide workqueue for issuing deferred shutdown requests
632  * aggregated from all vm* instances. We need our own isolated
633  * queue to ease flushing work items when a VM exits.
634  */
635 int kvm_irqfd_init(void)
636 {
637         irqfd_cleanup_wq = alloc_workqueue("kvm-irqfd-cleanup", 0, 0);
638         if (!irqfd_cleanup_wq)
639                 return -ENOMEM;
640 
641         return 0;
642 }
643 
644 void kvm_irqfd_exit(void)
645 {
646         destroy_workqueue(irqfd_cleanup_wq);
647 }
648 #endif
649 
650 /*
651  * --------------------------------------------------------------------
652  * ioeventfd: translate a PIO/MMIO memory write to an eventfd signal.
653  *
654  * userspace can register a PIO/MMIO address with an eventfd for receiving
655  * notification when the memory has been touched.
656  * --------------------------------------------------------------------
657  */
658 
659 struct _ioeventfd {
660         struct list_head     list;
661         u64                  addr;
662         int                  length;
663         struct eventfd_ctx  *eventfd;
664         u64                  datamatch;
665         struct kvm_io_device dev;
666         u8                   bus_idx;
667         bool                 wildcard;
668 };
669 
670 static inline struct _ioeventfd *
671 to_ioeventfd(struct kvm_io_device *dev)
672 {
673         return container_of(dev, struct _ioeventfd, dev);
674 }
675 
676 static void
677 ioeventfd_release(struct _ioeventfd *p)
678 {
679         eventfd_ctx_put(p->eventfd);
680         list_del(&p->list);
681         kfree(p);
682 }
683 
684 static bool
685 ioeventfd_in_range(struct _ioeventfd *p, gpa_t addr, int len, const void *val)
686 {
687         u64 _val;
688 
689         if (addr != p->addr)
690                 /* address must be precise for a hit */
691                 return false;
692 
693         if (!p->length)
694                 /* length = 0 means only look at the address, so always a hit */
695                 return true;
696 
697         if (len != p->length)
698                 /* address-range must be precise for a hit */
699                 return false;
700 
701         if (p->wildcard)
702                 /* all else equal, wildcard is always a hit */
703                 return true;
704 
705         /* otherwise, we have to actually compare the data */
706 
707         BUG_ON(!IS_ALIGNED((unsigned long)val, len));
708 
709         switch (len) {
710         case 1:
711                 _val = *(u8 *)val;
712                 break;
713         case 2:
714                 _val = *(u16 *)val;
715                 break;
716         case 4:
717                 _val = *(u32 *)val;
718                 break;
719         case 8:
720                 _val = *(u64 *)val;
721                 break;
722         default:
723                 return false;
724         }
725 
726         return _val == p->datamatch ? true : false;
727 }
728 
729 /* MMIO/PIO writes trigger an event if the addr/val match */
730 static int
731 ioeventfd_write(struct kvm_vcpu *vcpu, struct kvm_io_device *this, gpa_t addr,
732                 int len, const void *val)
733 {
734         struct _ioeventfd *p = to_ioeventfd(this);
735 
736         if (!ioeventfd_in_range(p, addr, len, val))
737                 return -EOPNOTSUPP;
738 
739         eventfd_signal(p->eventfd, 1);
740         return 0;
741 }
742 
743 /*
744  * This function is called as KVM is completely shutting down.  We do not
745  * need to worry about locking just nuke anything we have as quickly as possible
746  */
747 static void
748 ioeventfd_destructor(struct kvm_io_device *this)
749 {
750         struct _ioeventfd *p = to_ioeventfd(this);
751 
752         ioeventfd_release(p);
753 }
754 
755 static const struct kvm_io_device_ops ioeventfd_ops = {
756         .write      = ioeventfd_write,
757         .destructor = ioeventfd_destructor,
758 };
759 
760 /* assumes kvm->slots_lock held */
761 static bool
762 ioeventfd_check_collision(struct kvm *kvm, struct _ioeventfd *p)
763 {
764         struct _ioeventfd *_p;
765 
766         list_for_each_entry(_p, &kvm->ioeventfds, list)
767                 if (_p->bus_idx == p->bus_idx &&
768                     _p->addr == p->addr &&
769                     (!_p->length || !p->length ||
770                      (_p->length == p->length &&
771                       (_p->wildcard || p->wildcard ||
772                        _p->datamatch == p->datamatch))))
773                         return true;
774 
775         return false;
776 }
777 
778 static enum kvm_bus ioeventfd_bus_from_flags(__u32 flags)
779 {
780         if (flags & KVM_IOEVENTFD_FLAG_PIO)
781                 return KVM_PIO_BUS;
782         if (flags & KVM_IOEVENTFD_FLAG_VIRTIO_CCW_NOTIFY)
783                 return KVM_VIRTIO_CCW_NOTIFY_BUS;
784         return KVM_MMIO_BUS;
785 }
786 
787 static int kvm_assign_ioeventfd_idx(struct kvm *kvm,
788                                 enum kvm_bus bus_idx,
789                                 struct kvm_ioeventfd *args)
790 {
791 
792         struct eventfd_ctx *eventfd;
793         struct _ioeventfd *p;
794         int ret;
795 
796         eventfd = eventfd_ctx_fdget(args->fd);
797         if (IS_ERR(eventfd))
798                 return PTR_ERR(eventfd);
799 
800         p = kzalloc(sizeof(*p), GFP_KERNEL);
801         if (!p) {
802                 ret = -ENOMEM;
803                 goto fail;
804         }
805 
806         INIT_LIST_HEAD(&p->list);
807         p->addr    = args->addr;
808         p->bus_idx = bus_idx;
809         p->length  = args->len;
810         p->eventfd = eventfd;
811 
812         /* The datamatch feature is optional, otherwise this is a wildcard */
813         if (args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH)
814                 p->datamatch = args->datamatch;
815         else
816                 p->wildcard = true;
817 
818         mutex_lock(&kvm->slots_lock);
819 
820         /* Verify that there isn't a match already */
821         if (ioeventfd_check_collision(kvm, p)) {
822                 ret = -EEXIST;
823                 goto unlock_fail;
824         }
825 
826         kvm_iodevice_init(&p->dev, &ioeventfd_ops);
827 
828         ret = kvm_io_bus_register_dev(kvm, bus_idx, p->addr, p->length,
829                                       &p->dev);
830         if (ret < 0)
831                 goto unlock_fail;
832 
833         kvm_get_bus(kvm, bus_idx)->ioeventfd_count++;
834         list_add_tail(&p->list, &kvm->ioeventfds);
835 
836         mutex_unlock(&kvm->slots_lock);
837 
838         return 0;
839 
840 unlock_fail:
841         mutex_unlock(&kvm->slots_lock);
842 
843 fail:
844         kfree(p);
845         eventfd_ctx_put(eventfd);
846 
847         return ret;
848 }
849 
850 static int
851 kvm_deassign_ioeventfd_idx(struct kvm *kvm, enum kvm_bus bus_idx,
852                            struct kvm_ioeventfd *args)
853 {
854         struct _ioeventfd        *p, *tmp;
855         struct eventfd_ctx       *eventfd;
856         struct kvm_io_bus        *bus;
857         int                       ret = -ENOENT;
858 
859         eventfd = eventfd_ctx_fdget(args->fd);
860         if (IS_ERR(eventfd))
861                 return PTR_ERR(eventfd);
862 
863         mutex_lock(&kvm->slots_lock);
864 
865         list_for_each_entry_safe(p, tmp, &kvm->ioeventfds, list) {
866                 bool wildcard = !(args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH);
867 
868                 if (p->bus_idx != bus_idx ||
869                     p->eventfd != eventfd  ||
870                     p->addr != args->addr  ||
871                     p->length != args->len ||
872                     p->wildcard != wildcard)
873                         continue;
874 
875                 if (!p->wildcard && p->datamatch != args->datamatch)
876                         continue;
877 
878                 kvm_io_bus_unregister_dev(kvm, bus_idx, &p->dev);
879                 bus = kvm_get_bus(kvm, bus_idx);
880                 if (bus)
881                         bus->ioeventfd_count--;
882                 ioeventfd_release(p);
883                 ret = 0;
884                 break;
885         }
886 
887         mutex_unlock(&kvm->slots_lock);
888 
889         eventfd_ctx_put(eventfd);
890 
891         return ret;
892 }
893 
894 static int kvm_deassign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
895 {
896         enum kvm_bus bus_idx = ioeventfd_bus_from_flags(args->flags);
897         int ret = kvm_deassign_ioeventfd_idx(kvm, bus_idx, args);
898 
899         if (!args->len && bus_idx == KVM_MMIO_BUS)
900                 kvm_deassign_ioeventfd_idx(kvm, KVM_FAST_MMIO_BUS, args);
901 
902         return ret;
903 }
904 
905 static int
906 kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
907 {
908         enum kvm_bus              bus_idx;
909         int ret;
910 
911         bus_idx = ioeventfd_bus_from_flags(args->flags);
912         /* must be natural-word sized, or 0 to ignore length */
913         switch (args->len) {
914         case 0:
915         case 1:
916         case 2:
917         case 4:
918         case 8:
919                 break;
920         default:
921                 return -EINVAL;
922         }
923 
924         /* check for range overflow */
925         if (args->addr + args->len < args->addr)
926                 return -EINVAL;
927 
928         /* check for extra flags that we don't understand */
929         if (args->flags & ~KVM_IOEVENTFD_VALID_FLAG_MASK)
930                 return -EINVAL;
931 
932         /* ioeventfd with no length can't be combined with DATAMATCH */
933         if (!args->len && (args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH))
934                 return -EINVAL;
935 
936         ret = kvm_assign_ioeventfd_idx(kvm, bus_idx, args);
937         if (ret)
938                 goto fail;
939 
940         /* When length is ignored, MMIO is also put on a separate bus, for
941          * faster lookups.
942          */
943         if (!args->len && bus_idx == KVM_MMIO_BUS) {
944                 ret = kvm_assign_ioeventfd_idx(kvm, KVM_FAST_MMIO_BUS, args);
945                 if (ret < 0)
946                         goto fast_fail;
947         }
948 
949         return 0;
950 
951 fast_fail:
952         kvm_deassign_ioeventfd_idx(kvm, bus_idx, args);
953 fail:
954         return ret;
955 }
956 
957 int
958 kvm_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
959 {
960         if (args->flags & KVM_IOEVENTFD_FLAG_DEASSIGN)
961                 return kvm_deassign_ioeventfd(kvm, args);
962 
963         return kvm_assign_ioeventfd(kvm, args);
964 }
965 

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