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

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