2 * kvm eventfd support - use eventfd objects to signal various KVM events
4 * Copyright 2009 Novell. All Rights Reserved.
7 * Gregory Haskins <ghaskins@novell.com>
9 * This file is free software; you can redistribute it and/or modify
10 * it under the terms of version 2 of the GNU General Public License
11 * as published by the Free Software Foundation.
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software Foundation,
20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
23 #include <linux/kvm_host.h>
24 #include <linux/workqueue.h>
25 #include <linux/syscalls.h>
26 #include <linux/wait.h>
27 #include <linux/poll.h>
28 #include <linux/file.h>
29 #include <linux/list.h>
30 #include <linux/eventfd.h>
33 * --------------------------------------------------------------------
34 * irqfd: Allows an fd to be used to inject an interrupt to the guest
36 * Credit goes to Avi Kivity for the original idea.
37 * --------------------------------------------------------------------
42 struct eventfd_ctx
*eventfd
;
44 struct list_head list
;
46 wait_queue_head_t
*wqh
;
48 struct work_struct inject
;
49 struct work_struct shutdown
;
52 static struct workqueue_struct
*irqfd_cleanup_wq
;
55 irqfd_inject(struct work_struct
*work
)
57 struct _irqfd
*irqfd
= container_of(work
, struct _irqfd
, inject
);
58 struct kvm
*kvm
= irqfd
->kvm
;
60 mutex_lock(&kvm
->irq_lock
);
61 kvm_set_irq(kvm
, KVM_USERSPACE_IRQ_SOURCE_ID
, irqfd
->gsi
, 1);
62 kvm_set_irq(kvm
, KVM_USERSPACE_IRQ_SOURCE_ID
, irqfd
->gsi
, 0);
63 mutex_unlock(&kvm
->irq_lock
);
67 * Race-free decouple logic (ordering is critical)
70 irqfd_shutdown(struct work_struct
*work
)
72 struct _irqfd
*irqfd
= container_of(work
, struct _irqfd
, shutdown
);
75 * Synchronize with the wait-queue and unhook ourselves to prevent
78 remove_wait_queue(irqfd
->wqh
, &irqfd
->wait
);
81 * We know no new events will be scheduled at this point, so block
82 * until all previously outstanding events have completed
84 flush_work(&irqfd
->inject
);
87 * It is now safe to release the object's resources
89 eventfd_ctx_put(irqfd
->eventfd
);
94 /* assumes kvm->irqfds.lock is held */
96 irqfd_is_active(struct _irqfd
*irqfd
)
98 return list_empty(&irqfd
->list
) ? false : true;
102 * Mark the irqfd as inactive and schedule it for removal
104 * assumes kvm->irqfds.lock is held
107 irqfd_deactivate(struct _irqfd
*irqfd
)
109 BUG_ON(!irqfd_is_active(irqfd
));
111 list_del_init(&irqfd
->list
);
113 queue_work(irqfd_cleanup_wq
, &irqfd
->shutdown
);
117 * Called with wqh->lock held and interrupts disabled
120 irqfd_wakeup(wait_queue_t
*wait
, unsigned mode
, int sync
, void *key
)
122 struct _irqfd
*irqfd
= container_of(wait
, struct _irqfd
, wait
);
123 unsigned long flags
= (unsigned long)key
;
126 /* An event has been signaled, inject an interrupt */
127 schedule_work(&irqfd
->inject
);
129 if (flags
& POLLHUP
) {
130 /* The eventfd is closing, detach from KVM */
131 struct kvm
*kvm
= irqfd
->kvm
;
134 spin_lock_irqsave(&kvm
->irqfds
.lock
, flags
);
137 * We must check if someone deactivated the irqfd before
138 * we could acquire the irqfds.lock since the item is
139 * deactivated from the KVM side before it is unhooked from
140 * the wait-queue. If it is already deactivated, we can
141 * simply return knowing the other side will cleanup for us.
142 * We cannot race against the irqfd going away since the
143 * other side is required to acquire wqh->lock, which we hold
145 if (irqfd_is_active(irqfd
))
146 irqfd_deactivate(irqfd
);
148 spin_unlock_irqrestore(&kvm
->irqfds
.lock
, flags
);
155 irqfd_ptable_queue_proc(struct file
*file
, wait_queue_head_t
*wqh
,
158 struct _irqfd
*irqfd
= container_of(pt
, struct _irqfd
, pt
);
161 add_wait_queue(wqh
, &irqfd
->wait
);
165 kvm_irqfd_assign(struct kvm
*kvm
, int fd
, int gsi
)
167 struct _irqfd
*irqfd
;
168 struct file
*file
= NULL
;
169 struct eventfd_ctx
*eventfd
= NULL
;
173 irqfd
= kzalloc(sizeof(*irqfd
), GFP_KERNEL
);
179 INIT_LIST_HEAD(&irqfd
->list
);
180 INIT_WORK(&irqfd
->inject
, irqfd_inject
);
181 INIT_WORK(&irqfd
->shutdown
, irqfd_shutdown
);
183 file
= eventfd_fget(fd
);
189 eventfd
= eventfd_ctx_fileget(file
);
190 if (IS_ERR(eventfd
)) {
191 ret
= PTR_ERR(eventfd
);
195 irqfd
->eventfd
= eventfd
;
198 * Install our own custom wake-up handling so we are notified via
199 * a callback whenever someone signals the underlying eventfd
201 init_waitqueue_func_entry(&irqfd
->wait
, irqfd_wakeup
);
202 init_poll_funcptr(&irqfd
->pt
, irqfd_ptable_queue_proc
);
204 events
= file
->f_op
->poll(file
, &irqfd
->pt
);
206 spin_lock_irq(&kvm
->irqfds
.lock
);
207 list_add_tail(&irqfd
->list
, &kvm
->irqfds
.items
);
208 spin_unlock_irq(&kvm
->irqfds
.lock
);
211 * Check if there was an event already pending on the eventfd
212 * before we registered, and trigger it as if we didn't miss it.
215 schedule_work(&irqfd
->inject
);
218 * do not drop the file until the irqfd is fully initialized, otherwise
219 * we might race against the POLLHUP
226 if (eventfd
&& !IS_ERR(eventfd
))
227 eventfd_ctx_put(eventfd
);
229 if (file
&& !IS_ERR(file
))
237 kvm_irqfd_init(struct kvm
*kvm
)
239 spin_lock_init(&kvm
->irqfds
.lock
);
240 INIT_LIST_HEAD(&kvm
->irqfds
.items
);
244 * shutdown any irqfd's that match fd+gsi
247 kvm_irqfd_deassign(struct kvm
*kvm
, int fd
, int gsi
)
249 struct _irqfd
*irqfd
, *tmp
;
250 struct eventfd_ctx
*eventfd
;
252 eventfd
= eventfd_ctx_fdget(fd
);
254 return PTR_ERR(eventfd
);
256 spin_lock_irq(&kvm
->irqfds
.lock
);
258 list_for_each_entry_safe(irqfd
, tmp
, &kvm
->irqfds
.items
, list
) {
259 if (irqfd
->eventfd
== eventfd
&& irqfd
->gsi
== gsi
)
260 irqfd_deactivate(irqfd
);
263 spin_unlock_irq(&kvm
->irqfds
.lock
);
264 eventfd_ctx_put(eventfd
);
267 * Block until we know all outstanding shutdown jobs have completed
268 * so that we guarantee there will not be any more interrupts on this
269 * gsi once this deassign function returns.
271 flush_workqueue(irqfd_cleanup_wq
);
277 kvm_irqfd(struct kvm
*kvm
, int fd
, int gsi
, int flags
)
279 if (flags
& KVM_IRQFD_FLAG_DEASSIGN
)
280 return kvm_irqfd_deassign(kvm
, fd
, gsi
);
282 return kvm_irqfd_assign(kvm
, fd
, gsi
);
286 * This function is called as the kvm VM fd is being released. Shutdown all
287 * irqfds that still remain open
290 kvm_irqfd_release(struct kvm
*kvm
)
292 struct _irqfd
*irqfd
, *tmp
;
294 spin_lock_irq(&kvm
->irqfds
.lock
);
296 list_for_each_entry_safe(irqfd
, tmp
, &kvm
->irqfds
.items
, list
)
297 irqfd_deactivate(irqfd
);
299 spin_unlock_irq(&kvm
->irqfds
.lock
);
302 * Block until we know all outstanding shutdown jobs have completed
303 * since we do not take a kvm* reference.
305 flush_workqueue(irqfd_cleanup_wq
);
310 * create a host-wide workqueue for issuing deferred shutdown requests
311 * aggregated from all vm* instances. We need our own isolated single-thread
312 * queue to prevent deadlock against flushing the normal work-queue.
314 static int __init
irqfd_module_init(void)
316 irqfd_cleanup_wq
= create_singlethread_workqueue("kvm-irqfd-cleanup");
317 if (!irqfd_cleanup_wq
)
323 static void __exit
irqfd_module_exit(void)
325 destroy_workqueue(irqfd_cleanup_wq
);
328 module_init(irqfd_module_init
);
329 module_exit(irqfd_module_exit
);