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Linux/virt/kvm/eventfd.c

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  1 // SPDX-License-Identifier: GPL-2.0-only
  2 /*
  3  * kvm eventfd support - use eventfd objects to signal various KVM events
  4  *
  5  * Copyright 2009 Novell.  All Rights Reserved.
  6  * Copyright 2010 Red Hat, Inc. and/or its affiliates.
  7  *
  8  * Author:
  9  *      Gregory Haskins <ghaskins@novell.com>
 10  */
 11 
 12 #include <linux/kvm_host.h>
 13 #include <linux/kvm.h>
 14 #include <linux/kvm_irqfd.h>
 15 #include <linux/workqueue.h>
 16 #include <linux/syscalls.h>
 17 #include <linux/wait.h>
 18 #include <linux/poll.h>
 19 #include <linux/file.h>
 20 #include <linux/list.h>
 21 #include <linux/eventfd.h>
 22 #include <linux/kernel.h>
 23 #include <linux/srcu.h>
 24 #include <linux/slab.h>
 25 #include <linux/seqlock.h>
 26 #include <linux/irqbypass.h>
 27 #include <trace/events/kvm.h>
 28 
 29 #include <kvm/iodev.h>
 30 
 31 #ifdef CONFIG_HAVE_KVM_IRQFD
 32 
 33 static struct workqueue_struct *irqfd_cleanup_wq;
 34 
 35 bool __attribute__((weak))
 36 kvm_arch_irqfd_allowed(struct kvm *kvm, struct kvm_irqfd *args)
 37 {
 38         return true;
 39 }
 40 
 41 static void
 42 irqfd_inject(struct work_struct *work)
 43 {
 44         struct kvm_kernel_irqfd *irqfd =
 45                 container_of(work, struct kvm_kernel_irqfd, inject);
 46         struct kvm *kvm = irqfd->kvm;
 47 
 48         if (!irqfd->resampler) {
 49                 kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 1,
 50                                 false);
 51                 kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 0,
 52                                 false);
 53         } else
 54                 kvm_set_irq(kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
 55                             irqfd->gsi, 1, false);
 56 }
 57 
 58 /*
 59  * Since resampler irqfds share an IRQ source ID, we de-assert once
 60  * then notify all of the resampler irqfds using this GSI.  We can't
 61  * do multiple de-asserts or we risk racing with incoming re-asserts.
 62  */
 63 static void
 64 irqfd_resampler_ack(struct kvm_irq_ack_notifier *kian)
 65 {
 66         struct kvm_kernel_irqfd_resampler *resampler;
 67         struct kvm *kvm;
 68         struct kvm_kernel_irqfd *irqfd;
 69         int idx;
 70 
 71         resampler = container_of(kian,
 72                         struct kvm_kernel_irqfd_resampler, notifier);
 73         kvm = resampler->kvm;
 74 
 75         kvm_set_irq(kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
 76                     resampler->notifier.gsi, 0, false);
 77 
 78         idx = srcu_read_lock(&kvm->irq_srcu);
 79 
 80         list_for_each_entry_rcu(irqfd, &resampler->list, resampler_link)
 81                 eventfd_signal(irqfd->resamplefd, 1);
 82 
 83         srcu_read_unlock(&kvm->irq_srcu, idx);
 84 }
 85 
 86 static void
 87 irqfd_resampler_shutdown(struct kvm_kernel_irqfd *irqfd)
 88 {
 89         struct kvm_kernel_irqfd_resampler *resampler = irqfd->resampler;
 90         struct kvm *kvm = resampler->kvm;
 91 
 92         mutex_lock(&kvm->irqfds.resampler_lock);
 93 
 94         list_del_rcu(&irqfd->resampler_link);
 95         synchronize_srcu(&kvm->irq_srcu);
 96 
 97         if (list_empty(&resampler->list)) {
 98                 list_del(&resampler->link);
 99                 kvm_unregister_irq_ack_notifier(kvm, &resampler->notifier);
100                 kvm_set_irq(kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
101                             resampler->notifier.gsi, 0, false);
102                 kfree(resampler);
103         }
104 
105         mutex_unlock(&kvm->irqfds.resampler_lock);
106 }
107 
108 /*
109  * Race-free decouple logic (ordering is critical)
110  */
111 static void
112 irqfd_shutdown(struct work_struct *work)
113 {
114         struct kvm_kernel_irqfd *irqfd =
115                 container_of(work, struct kvm_kernel_irqfd, shutdown);
116         struct kvm *kvm = irqfd->kvm;
117         u64 cnt;
118 
119         /* Make sure irqfd has been initalized in assign path. */
120         synchronize_srcu(&kvm->irq_srcu);
121 
122         /*
123          * Synchronize with the wait-queue and unhook ourselves to prevent
124          * further events.
125          */
126         eventfd_ctx_remove_wait_queue(irqfd->eventfd, &irqfd->wait, &cnt);
127 
128         /*
129          * We know no new events will be scheduled at this point, so block
130          * until all previously outstanding events have completed
131          */
132         flush_work(&irqfd->inject);
133 
134         if (irqfd->resampler) {
135                 irqfd_resampler_shutdown(irqfd);
136                 eventfd_ctx_put(irqfd->resamplefd);
137         }
138 
139         /*
140          * It is now safe to release the object's resources
141          */
142 #ifdef CONFIG_HAVE_KVM_IRQ_BYPASS
143         irq_bypass_unregister_consumer(&irqfd->consumer);
144 #endif
145         eventfd_ctx_put(irqfd->eventfd);
146         kfree(irqfd);
147 }
148 
149 
150 /* assumes kvm->irqfds.lock is held */
151 static bool
152 irqfd_is_active(struct kvm_kernel_irqfd *irqfd)
153 {
154         return list_empty(&irqfd->list) ? false : true;
155 }
156 
157 /*
158  * Mark the irqfd as inactive and schedule it for removal
159  *
160  * assumes kvm->irqfds.lock is held
161  */
162 static void
163 irqfd_deactivate(struct kvm_kernel_irqfd *irqfd)
164 {
165         BUG_ON(!irqfd_is_active(irqfd));
166 
167         list_del_init(&irqfd->list);
168 
169         queue_work(irqfd_cleanup_wq, &irqfd->shutdown);
170 }
171 
172 int __attribute__((weak)) kvm_arch_set_irq_inatomic(
173                                 struct kvm_kernel_irq_routing_entry *irq,
174                                 struct kvm *kvm, int irq_source_id,
175                                 int level,
176                                 bool line_status)
177 {
178         return -EWOULDBLOCK;
179 }
180 
181 /*
182  * Called with wqh->lock held and interrupts disabled
183  */
184 static int
185 irqfd_wakeup(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
186 {
187         struct kvm_kernel_irqfd *irqfd =
188                 container_of(wait, struct kvm_kernel_irqfd, wait);
189         __poll_t flags = key_to_poll(key);
190         struct kvm_kernel_irq_routing_entry irq;
191         struct kvm *kvm = irqfd->kvm;
192         unsigned seq;
193         int idx;
194 
195         if (flags & EPOLLIN) {
196                 idx = srcu_read_lock(&kvm->irq_srcu);
197                 do {
198                         seq = read_seqcount_begin(&irqfd->irq_entry_sc);
199                         irq = irqfd->irq_entry;
200                 } while (read_seqcount_retry(&irqfd->irq_entry_sc, seq));
201                 /* An event has been signaled, inject an interrupt */
202                 if (kvm_arch_set_irq_inatomic(&irq, kvm,
203                                               KVM_USERSPACE_IRQ_SOURCE_ID, 1,
204                                               false) == -EWOULDBLOCK)
205                         schedule_work(&irqfd->inject);
206                 srcu_read_unlock(&kvm->irq_srcu, idx);
207         }
208 
209         if (flags & EPOLLHUP) {
210                 /* The eventfd is closing, detach from KVM */
211                 unsigned long iflags;
212 
213                 spin_lock_irqsave(&kvm->irqfds.lock, iflags);
214 
215                 /*
216                  * We must check if someone deactivated the irqfd before
217                  * we could acquire the irqfds.lock since the item is
218                  * deactivated from the KVM side before it is unhooked from
219                  * the wait-queue.  If it is already deactivated, we can
220                  * simply return knowing the other side will cleanup for us.
221                  * We cannot race against the irqfd going away since the
222                  * other side is required to acquire wqh->lock, which we hold
223                  */
224                 if (irqfd_is_active(irqfd))
225                         irqfd_deactivate(irqfd);
226 
227                 spin_unlock_irqrestore(&kvm->irqfds.lock, iflags);
228         }
229 
230         return 0;
231 }
232 
233 static void
234 irqfd_ptable_queue_proc(struct file *file, wait_queue_head_t *wqh,
235                         poll_table *pt)
236 {
237         struct kvm_kernel_irqfd *irqfd =
238                 container_of(pt, struct kvm_kernel_irqfd, pt);
239         add_wait_queue(wqh, &irqfd->wait);
240 }
241 
242 /* Must be called under irqfds.lock */
243 static void irqfd_update(struct kvm *kvm, struct kvm_kernel_irqfd *irqfd)
244 {
245         struct kvm_kernel_irq_routing_entry *e;
246         struct kvm_kernel_irq_routing_entry entries[KVM_NR_IRQCHIPS];
247         int n_entries;
248 
249         n_entries = kvm_irq_map_gsi(kvm, entries, irqfd->gsi);
250 
251         write_seqcount_begin(&irqfd->irq_entry_sc);
252 
253         e = entries;
254         if (n_entries == 1)
255                 irqfd->irq_entry = *e;
256         else
257                 irqfd->irq_entry.type = 0;
258 
259         write_seqcount_end(&irqfd->irq_entry_sc);
260 }
261 
262 #ifdef CONFIG_HAVE_KVM_IRQ_BYPASS
263 void __attribute__((weak)) kvm_arch_irq_bypass_stop(
264                                 struct irq_bypass_consumer *cons)
265 {
266 }
267 
268 void __attribute__((weak)) kvm_arch_irq_bypass_start(
269                                 struct irq_bypass_consumer *cons)
270 {
271 }
272 
273 int  __attribute__((weak)) kvm_arch_update_irqfd_routing(
274                                 struct kvm *kvm, unsigned int host_irq,
275                                 uint32_t guest_irq, bool set)
276 {
277         return 0;
278 }
279 #endif
280 
281 static int
282 kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args)
283 {
284         struct kvm_kernel_irqfd *irqfd, *tmp;
285         struct fd f;
286         struct eventfd_ctx *eventfd = NULL, *resamplefd = NULL;
287         int ret;
288         __poll_t events;
289         int idx;
290 
291         if (!kvm_arch_intc_initialized(kvm))
292                 return -EAGAIN;
293 
294         if (!kvm_arch_irqfd_allowed(kvm, args))
295                 return -EINVAL;
296 
297         irqfd = kzalloc(sizeof(*irqfd), GFP_KERNEL_ACCOUNT);
298         if (!irqfd)
299                 return -ENOMEM;
300 
301         irqfd->kvm = kvm;
302         irqfd->gsi = args->gsi;
303         INIT_LIST_HEAD(&irqfd->list);
304         INIT_WORK(&irqfd->inject, irqfd_inject);
305         INIT_WORK(&irqfd->shutdown, irqfd_shutdown);
306         seqcount_init(&irqfd->irq_entry_sc);
307 
308         f = fdget(args->fd);
309         if (!f.file) {
310                 ret = -EBADF;
311                 goto out;
312         }
313 
314         eventfd = eventfd_ctx_fileget(f.file);
315         if (IS_ERR(eventfd)) {
316                 ret = PTR_ERR(eventfd);
317                 goto fail;
318         }
319 
320         irqfd->eventfd = eventfd;
321 
322         if (args->flags & KVM_IRQFD_FLAG_RESAMPLE) {
323                 struct kvm_kernel_irqfd_resampler *resampler;
324 
325                 resamplefd = eventfd_ctx_fdget(args->resamplefd);
326                 if (IS_ERR(resamplefd)) {
327                         ret = PTR_ERR(resamplefd);
328                         goto fail;
329                 }
330 
331                 irqfd->resamplefd = resamplefd;
332                 INIT_LIST_HEAD(&irqfd->resampler_link);
333 
334                 mutex_lock(&kvm->irqfds.resampler_lock);
335 
336                 list_for_each_entry(resampler,
337                                     &kvm->irqfds.resampler_list, link) {
338                         if (resampler->notifier.gsi == irqfd->gsi) {
339                                 irqfd->resampler = resampler;
340                                 break;
341                         }
342                 }
343 
344                 if (!irqfd->resampler) {
345                         resampler = kzalloc(sizeof(*resampler),
346                                             GFP_KERNEL_ACCOUNT);
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_srcu(&kvm->irq_srcu);
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         idx = srcu_read_lock(&kvm->irq_srcu);
391         irqfd_update(kvm, irqfd);
392 
393         list_add_tail(&irqfd->list, &kvm->irqfds.items);
394 
395         spin_unlock_irq(&kvm->irqfds.lock);
396 
397         /*
398          * Check if there was an event already pending on the eventfd
399          * before we registered, and trigger it as if we didn't miss it.
400          */
401         events = vfs_poll(f.file, &irqfd->pt);
402 
403         if (events & EPOLLIN)
404                 schedule_work(&irqfd->inject);
405 
406 #ifdef CONFIG_HAVE_KVM_IRQ_BYPASS
407         if (kvm_arch_has_irq_bypass()) {
408                 irqfd->consumer.token = (void *)irqfd->eventfd;
409                 irqfd->consumer.add_producer = kvm_arch_irq_bypass_add_producer;
410                 irqfd->consumer.del_producer = kvm_arch_irq_bypass_del_producer;
411                 irqfd->consumer.stop = kvm_arch_irq_bypass_stop;
412                 irqfd->consumer.start = kvm_arch_irq_bypass_start;
413                 ret = irq_bypass_register_consumer(&irqfd->consumer);
414                 if (ret)
415                         pr_info("irq bypass consumer (token %p) registration fails: %d\n",
416                                 irqfd->consumer.token, ret);
417         }
418 #endif
419 
420         srcu_read_unlock(&kvm->irq_srcu, idx);
421 
422         /*
423          * do not drop the file until the irqfd is fully initialized, otherwise
424          * we might race against the EPOLLHUP
425          */
426         fdput(f);
427         return 0;
428 
429 fail:
430         if (irqfd->resampler)
431                 irqfd_resampler_shutdown(irqfd);
432 
433         if (resamplefd && !IS_ERR(resamplefd))
434                 eventfd_ctx_put(resamplefd);
435 
436         if (eventfd && !IS_ERR(eventfd))
437                 eventfd_ctx_put(eventfd);
438 
439         fdput(f);
440 
441 out:
442         kfree(irqfd);
443         return ret;
444 }
445 
446 bool kvm_irq_has_notifier(struct kvm *kvm, unsigned irqchip, unsigned pin)
447 {
448         struct kvm_irq_ack_notifier *kian;
449         int gsi, idx;
450 
451         idx = srcu_read_lock(&kvm->irq_srcu);
452         gsi = kvm_irq_map_chip_pin(kvm, irqchip, pin);
453         if (gsi != -1)
454                 hlist_for_each_entry_rcu(kian, &kvm->irq_ack_notifier_list,
455                                          link)
456                         if (kian->gsi == gsi) {
457                                 srcu_read_unlock(&kvm->irq_srcu, idx);
458                                 return true;
459                         }
460 
461         srcu_read_unlock(&kvm->irq_srcu, idx);
462 
463         return false;
464 }
465 EXPORT_SYMBOL_GPL(kvm_irq_has_notifier);
466 
467 void kvm_notify_acked_gsi(struct kvm *kvm, int gsi)
468 {
469         struct kvm_irq_ack_notifier *kian;
470 
471         hlist_for_each_entry_rcu(kian, &kvm->irq_ack_notifier_list,
472                                  link)
473                 if (kian->gsi == gsi)
474                         kian->irq_acked(kian);
475 }
476 
477 void kvm_notify_acked_irq(struct kvm *kvm, unsigned irqchip, unsigned pin)
478 {
479         int gsi, idx;
480 
481         trace_kvm_ack_irq(irqchip, pin);
482 
483         idx = srcu_read_lock(&kvm->irq_srcu);
484         gsi = kvm_irq_map_chip_pin(kvm, irqchip, pin);
485         if (gsi != -1)
486                 kvm_notify_acked_gsi(kvm, gsi);
487         srcu_read_unlock(&kvm->irq_srcu, idx);
488 }
489 
490 void kvm_register_irq_ack_notifier(struct kvm *kvm,
491                                    struct kvm_irq_ack_notifier *kian)
492 {
493         mutex_lock(&kvm->irq_lock);
494         hlist_add_head_rcu(&kian->link, &kvm->irq_ack_notifier_list);
495         mutex_unlock(&kvm->irq_lock);
496         kvm_arch_post_irq_ack_notifier_list_update(kvm);
497 }
498 
499 void kvm_unregister_irq_ack_notifier(struct kvm *kvm,
500                                     struct kvm_irq_ack_notifier *kian)
501 {
502         mutex_lock(&kvm->irq_lock);
503         hlist_del_init_rcu(&kian->link);
504         mutex_unlock(&kvm->irq_lock);
505         synchronize_srcu(&kvm->irq_srcu);
506         kvm_arch_post_irq_ack_notifier_list_update(kvm);
507 }
508 #endif
509 
510 void
511 kvm_eventfd_init(struct kvm *kvm)
512 {
513 #ifdef CONFIG_HAVE_KVM_IRQFD
514         spin_lock_init(&kvm->irqfds.lock);
515         INIT_LIST_HEAD(&kvm->irqfds.items);
516         INIT_LIST_HEAD(&kvm->irqfds.resampler_list);
517         mutex_init(&kvm->irqfds.resampler_lock);
518 #endif
519         INIT_LIST_HEAD(&kvm->ioeventfds);
520 }
521 
522 #ifdef CONFIG_HAVE_KVM_IRQFD
523 /*
524  * shutdown any irqfd's that match fd+gsi
525  */
526 static int
527 kvm_irqfd_deassign(struct kvm *kvm, struct kvm_irqfd *args)
528 {
529         struct kvm_kernel_irqfd *irqfd, *tmp;
530         struct eventfd_ctx *eventfd;
531 
532         eventfd = eventfd_ctx_fdget(args->fd);
533         if (IS_ERR(eventfd))
534                 return PTR_ERR(eventfd);
535 
536         spin_lock_irq(&kvm->irqfds.lock);
537 
538         list_for_each_entry_safe(irqfd, tmp, &kvm->irqfds.items, list) {
539                 if (irqfd->eventfd == eventfd && irqfd->gsi == args->gsi) {
540                         /*
541                          * This clearing of irq_entry.type is needed for when
542                          * another thread calls kvm_irq_routing_update before
543                          * we flush workqueue below (we synchronize with
544                          * kvm_irq_routing_update using irqfds.lock).
545                          */
546                         write_seqcount_begin(&irqfd->irq_entry_sc);
547                         irqfd->irq_entry.type = 0;
548                         write_seqcount_end(&irqfd->irq_entry_sc);
549                         irqfd_deactivate(irqfd);
550                 }
551         }
552 
553         spin_unlock_irq(&kvm->irqfds.lock);
554         eventfd_ctx_put(eventfd);
555 
556         /*
557          * Block until we know all outstanding shutdown jobs have completed
558          * so that we guarantee there will not be any more interrupts on this
559          * gsi once this deassign function returns.
560          */
561         flush_workqueue(irqfd_cleanup_wq);
562 
563         return 0;
564 }
565 
566 int
567 kvm_irqfd(struct kvm *kvm, struct kvm_irqfd *args)
568 {
569         if (args->flags & ~(KVM_IRQFD_FLAG_DEASSIGN | KVM_IRQFD_FLAG_RESAMPLE))
570                 return -EINVAL;
571 
572         if (args->flags & KVM_IRQFD_FLAG_DEASSIGN)
573                 return kvm_irqfd_deassign(kvm, args);
574 
575         return kvm_irqfd_assign(kvm, args);
576 }
577 
578 /*
579  * This function is called as the kvm VM fd is being released. Shutdown all
580  * irqfds that still remain open
581  */
582 void
583 kvm_irqfd_release(struct kvm *kvm)
584 {
585         struct kvm_kernel_irqfd *irqfd, *tmp;
586 
587         spin_lock_irq(&kvm->irqfds.lock);
588 
589         list_for_each_entry_safe(irqfd, tmp, &kvm->irqfds.items, list)
590                 irqfd_deactivate(irqfd);
591 
592         spin_unlock_irq(&kvm->irqfds.lock);
593 
594         /*
595          * Block until we know all outstanding shutdown jobs have completed
596          * since we do not take a kvm* reference.
597          */
598         flush_workqueue(irqfd_cleanup_wq);
599 
600 }
601 
602 /*
603  * Take note of a change in irq routing.
604  * Caller must invoke synchronize_srcu(&kvm->irq_srcu) afterwards.
605  */
606 void kvm_irq_routing_update(struct kvm *kvm)
607 {
608         struct kvm_kernel_irqfd *irqfd;
609 
610         spin_lock_irq(&kvm->irqfds.lock);
611 
612         list_for_each_entry(irqfd, &kvm->irqfds.items, list) {
613                 irqfd_update(kvm, irqfd);
614 
615 #ifdef CONFIG_HAVE_KVM_IRQ_BYPASS
616                 if (irqfd->producer) {
617                         int ret = kvm_arch_update_irqfd_routing(
618                                         irqfd->kvm, irqfd->producer->irq,
619                                         irqfd->gsi, 1);
620                         WARN_ON(ret);
621                 }
622 #endif
623         }
624 
625         spin_unlock_irq(&kvm->irqfds.lock);
626 }
627 
628 /*
629  * create a host-wide workqueue for issuing deferred shutdown requests
630  * aggregated from all vm* instances. We need our own isolated
631  * queue to ease flushing work items when a VM exits.
632  */
633 int kvm_irqfd_init(void)
634 {
635         irqfd_cleanup_wq = alloc_workqueue("kvm-irqfd-cleanup", 0, 0);
636         if (!irqfd_cleanup_wq)
637                 return -ENOMEM;
638 
639         return 0;
640 }
641 
642 void kvm_irqfd_exit(void)
643 {
644         destroy_workqueue(irqfd_cleanup_wq);
645 }
646 #endif
647 
648 /*
649  * --------------------------------------------------------------------
650  * ioeventfd: translate a PIO/MMIO memory write to an eventfd signal.
651  *
652  * userspace can register a PIO/MMIO address with an eventfd for receiving
653  * notification when the memory has been touched.
654  * --------------------------------------------------------------------
655  */
656 
657 struct _ioeventfd {
658         struct list_head     list;
659         u64                  addr;
660         int                  length;
661         struct eventfd_ctx  *eventfd;
662         u64                  datamatch;
663         struct kvm_io_device dev;
664         u8                   bus_idx;
665         bool                 wildcard;
666 };
667 
668 static inline struct _ioeventfd *
669 to_ioeventfd(struct kvm_io_device *dev)
670 {
671         return container_of(dev, struct _ioeventfd, dev);
672 }
673 
674 static void
675 ioeventfd_release(struct _ioeventfd *p)
676 {
677         eventfd_ctx_put(p->eventfd);
678         list_del(&p->list);
679         kfree(p);
680 }
681 
682 static bool
683 ioeventfd_in_range(struct _ioeventfd *p, gpa_t addr, int len, const void *val)
684 {
685         u64 _val;
686 
687         if (addr != p->addr)
688                 /* address must be precise for a hit */
689                 return false;
690 
691         if (!p->length)
692                 /* length = 0 means only look at the address, so always a hit */
693                 return true;
694 
695         if (len != p->length)
696                 /* address-range must be precise for a hit */
697                 return false;
698 
699         if (p->wildcard)
700                 /* all else equal, wildcard is always a hit */
701                 return true;
702 
703         /* otherwise, we have to actually compare the data */
704 
705         BUG_ON(!IS_ALIGNED((unsigned long)val, len));
706 
707         switch (len) {
708         case 1:
709                 _val = *(u8 *)val;
710                 break;
711         case 2:
712                 _val = *(u16 *)val;
713                 break;
714         case 4:
715                 _val = *(u32 *)val;
716                 break;
717         case 8:
718                 _val = *(u64 *)val;
719                 break;
720         default:
721                 return false;
722         }
723 
724         return _val == p->datamatch ? true : false;
725 }
726 
727 /* MMIO/PIO writes trigger an event if the addr/val match */
728 static int
729 ioeventfd_write(struct kvm_vcpu *vcpu, struct kvm_io_device *this, gpa_t addr,
730                 int len, const void *val)
731 {
732         struct _ioeventfd *p = to_ioeventfd(this);
733 
734         if (!ioeventfd_in_range(p, addr, len, val))
735                 return -EOPNOTSUPP;
736 
737         eventfd_signal(p->eventfd, 1);
738         return 0;
739 }
740 
741 /*
742  * This function is called as KVM is completely shutting down.  We do not
743  * need to worry about locking just nuke anything we have as quickly as possible
744  */
745 static void
746 ioeventfd_destructor(struct kvm_io_device *this)
747 {
748         struct _ioeventfd *p = to_ioeventfd(this);
749 
750         ioeventfd_release(p);
751 }
752 
753 static const struct kvm_io_device_ops ioeventfd_ops = {
754         .write      = ioeventfd_write,
755         .destructor = ioeventfd_destructor,
756 };
757 
758 /* assumes kvm->slots_lock held */
759 static bool
760 ioeventfd_check_collision(struct kvm *kvm, struct _ioeventfd *p)
761 {
762         struct _ioeventfd *_p;
763 
764         list_for_each_entry(_p, &kvm->ioeventfds, list)
765                 if (_p->bus_idx == p->bus_idx &&
766                     _p->addr == p->addr &&
767                     (!_p->length || !p->length ||
768                      (_p->length == p->length &&
769                       (_p->wildcard || p->wildcard ||
770                        _p->datamatch == p->datamatch))))
771                         return true;
772 
773         return false;
774 }
775 
776 static enum kvm_bus ioeventfd_bus_from_flags(__u32 flags)
777 {
778         if (flags & KVM_IOEVENTFD_FLAG_PIO)
779                 return KVM_PIO_BUS;
780         if (flags & KVM_IOEVENTFD_FLAG_VIRTIO_CCW_NOTIFY)
781                 return KVM_VIRTIO_CCW_NOTIFY_BUS;
782         return KVM_MMIO_BUS;
783 }
784 
785 static int kvm_assign_ioeventfd_idx(struct kvm *kvm,
786                                 enum kvm_bus bus_idx,
787                                 struct kvm_ioeventfd *args)
788 {
789 
790         struct eventfd_ctx *eventfd;
791         struct _ioeventfd *p;
792         int ret;
793 
794         eventfd = eventfd_ctx_fdget(args->fd);
795         if (IS_ERR(eventfd))
796                 return PTR_ERR(eventfd);
797 
798         p = kzalloc(sizeof(*p), GFP_KERNEL_ACCOUNT);
799         if (!p) {
800                 ret = -ENOMEM;
801                 goto fail;
802         }
803 
804         INIT_LIST_HEAD(&p->list);
805         p->addr    = args->addr;
806         p->bus_idx = bus_idx;
807         p->length  = args->len;
808         p->eventfd = eventfd;
809 
810         /* The datamatch feature is optional, otherwise this is a wildcard */
811         if (args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH)
812                 p->datamatch = args->datamatch;
813         else
814                 p->wildcard = true;
815 
816         mutex_lock(&kvm->slots_lock);
817 
818         /* Verify that there isn't a match already */
819         if (ioeventfd_check_collision(kvm, p)) {
820                 ret = -EEXIST;
821                 goto unlock_fail;
822         }
823 
824         kvm_iodevice_init(&p->dev, &ioeventfd_ops);
825 
826         ret = kvm_io_bus_register_dev(kvm, bus_idx, p->addr, p->length,
827                                       &p->dev);
828         if (ret < 0)
829                 goto unlock_fail;
830 
831         kvm_get_bus(kvm, bus_idx)->ioeventfd_count++;
832         list_add_tail(&p->list, &kvm->ioeventfds);
833 
834         mutex_unlock(&kvm->slots_lock);
835 
836         return 0;
837 
838 unlock_fail:
839         mutex_unlock(&kvm->slots_lock);
840 
841 fail:
842         kfree(p);
843         eventfd_ctx_put(eventfd);
844 
845         return ret;
846 }
847 
848 static int
849 kvm_deassign_ioeventfd_idx(struct kvm *kvm, enum kvm_bus bus_idx,
850                            struct kvm_ioeventfd *args)
851 {
852         struct _ioeventfd        *p, *tmp;
853         struct eventfd_ctx       *eventfd;
854         struct kvm_io_bus        *bus;
855         int                       ret = -ENOENT;
856 
857         eventfd = eventfd_ctx_fdget(args->fd);
858         if (IS_ERR(eventfd))
859                 return PTR_ERR(eventfd);
860 
861         mutex_lock(&kvm->slots_lock);
862 
863         list_for_each_entry_safe(p, tmp, &kvm->ioeventfds, list) {
864                 bool wildcard = !(args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH);
865 
866                 if (p->bus_idx != bus_idx ||
867                     p->eventfd != eventfd  ||
868                     p->addr != args->addr  ||
869                     p->length != args->len ||
870                     p->wildcard != wildcard)
871                         continue;
872 
873                 if (!p->wildcard && p->datamatch != args->datamatch)
874                         continue;
875 
876                 kvm_io_bus_unregister_dev(kvm, bus_idx, &p->dev);
877                 bus = kvm_get_bus(kvm, bus_idx);
878                 if (bus)
879                         bus->ioeventfd_count--;
880                 ioeventfd_release(p);
881                 ret = 0;
882                 break;
883         }
884 
885         mutex_unlock(&kvm->slots_lock);
886 
887         eventfd_ctx_put(eventfd);
888 
889         return ret;
890 }
891 
892 static int kvm_deassign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
893 {
894         enum kvm_bus bus_idx = ioeventfd_bus_from_flags(args->flags);
895         int ret = kvm_deassign_ioeventfd_idx(kvm, bus_idx, args);
896 
897         if (!args->len && bus_idx == KVM_MMIO_BUS)
898                 kvm_deassign_ioeventfd_idx(kvm, KVM_FAST_MMIO_BUS, args);
899 
900         return ret;
901 }
902 
903 static int
904 kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
905 {
906         enum kvm_bus              bus_idx;
907         int ret;
908 
909         bus_idx = ioeventfd_bus_from_flags(args->flags);
910         /* must be natural-word sized, or 0 to ignore length */
911         switch (args->len) {
912         case 0:
913         case 1:
914         case 2:
915         case 4:
916         case 8:
917                 break;
918         default:
919                 return -EINVAL;
920         }
921 
922         /* check for range overflow */
923         if (args->addr + args->len < args->addr)
924                 return -EINVAL;
925 
926         /* check for extra flags that we don't understand */
927         if (args->flags & ~KVM_IOEVENTFD_VALID_FLAG_MASK)
928                 return -EINVAL;
929 
930         /* ioeventfd with no length can't be combined with DATAMATCH */
931         if (!args->len && (args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH))
932                 return -EINVAL;
933 
934         ret = kvm_assign_ioeventfd_idx(kvm, bus_idx, args);
935         if (ret)
936                 goto fail;
937 
938         /* When length is ignored, MMIO is also put on a separate bus, for
939          * faster lookups.
940          */
941         if (!args->len && bus_idx == KVM_MMIO_BUS) {
942                 ret = kvm_assign_ioeventfd_idx(kvm, KVM_FAST_MMIO_BUS, args);
943                 if (ret < 0)
944                         goto fast_fail;
945         }
946 
947         return 0;
948 
949 fast_fail:
950         kvm_deassign_ioeventfd_idx(kvm, bus_idx, args);
951 fail:
952         return ret;
953 }
954 
955 int
956 kvm_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
957 {
958         if (args->flags & KVM_IOEVENTFD_FLAG_DEASSIGN)
959                 return kvm_deassign_ioeventfd(kvm, args);
960 
961         return kvm_assign_ioeventfd(kvm, args);
962 }
963 

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