1/*
2 * VFIO generic eventfd code for IRQFD support.
3 * Derived from drivers/vfio/pci/vfio_pci_intrs.c
4 *
5 * Copyright (C) 2012 Red Hat, Inc. All rights reserved.
6 * Author: Alex Williamson <alex.williamson@redhat.com>
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
11 */
12
13#include <linux/vfio.h>
14#include <linux/eventfd.h>
15#include <linux/file.h>
16#include <linux/module.h>
17#include <linux/slab.h>
18
19#define DRIVER_VERSION "0.1"
20#define DRIVER_AUTHOR "Alex Williamson <alex.williamson@redhat.com>"
21#define DRIVER_DESC "IRQFD support for VFIO bus drivers"
22
23static struct workqueue_struct *vfio_irqfd_cleanup_wq;
24static DEFINE_SPINLOCK(virqfd_lock);
25
26static int __init vfio_virqfd_init(void)
27{
28 vfio_irqfd_cleanup_wq =
29 create_singlethread_workqueue("vfio-irqfd-cleanup");
30 if (!vfio_irqfd_cleanup_wq)
31 return -ENOMEM;
32
33 return 0;
34}
35
36static void __exit vfio_virqfd_exit(void)
37{
38 destroy_workqueue(vfio_irqfd_cleanup_wq);
39}
40
41static void virqfd_deactivate(struct virqfd *virqfd)
42{
43 queue_work(vfio_irqfd_cleanup_wq, &virqfd->shutdown);
44}
45
46static int virqfd_wakeup(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
47{
48 struct virqfd *virqfd = container_of(wait, struct virqfd, wait);
49 __poll_t flags = key_to_poll(key);
50
51 if (flags & EPOLLIN) {
52 /* An event has been signaled, call function */
53 if ((!virqfd->handler ||
54 virqfd->handler(virqfd->opaque, virqfd->data)) &&
55 virqfd->thread)
56 schedule_work(&virqfd->inject);
57 }
58
59 if (flags & EPOLLHUP) {
60 unsigned long flags;
61 spin_lock_irqsave(&virqfd_lock, flags);
62
63 /*
64 * The eventfd is closing, if the virqfd has not yet been
65 * queued for release, as determined by testing whether the
66 * virqfd pointer to it is still valid, queue it now. As
67 * with kvm irqfds, we know we won't race against the virqfd
68 * going away because we hold the lock to get here.
69 */
70 if (*(virqfd->pvirqfd) == virqfd) {
71 *(virqfd->pvirqfd) = NULL;
72 virqfd_deactivate(virqfd);
73 }
74
75 spin_unlock_irqrestore(&virqfd_lock, flags);
76 }
77
78 return 0;
79}
80
81static void virqfd_ptable_queue_proc(struct file *file,
82 wait_queue_head_t *wqh, poll_table *pt)
83{
84 struct virqfd *virqfd = container_of(pt, struct virqfd, pt);
85 add_wait_queue(wqh, &virqfd->wait);
86}
87
88static void virqfd_shutdown(struct work_struct *work)
89{
90 struct virqfd *virqfd = container_of(work, struct virqfd, shutdown);
91 u64 cnt;
92
93 eventfd_ctx_remove_wait_queue(virqfd->eventfd, &virqfd->wait, &cnt);
94 flush_work(&virqfd->inject);
95 eventfd_ctx_put(virqfd->eventfd);
96
97 kfree(virqfd);
98}
99
100static void virqfd_inject(struct work_struct *work)
101{
102 struct virqfd *virqfd = container_of(work, struct virqfd, inject);
103 if (virqfd->thread)
104 virqfd->thread(virqfd->opaque, virqfd->data);
105}
106
107int vfio_virqfd_enable(void *opaque,
108 int (*handler)(void *, void *),
109 void (*thread)(void *, void *),
110 void *data, struct virqfd **pvirqfd, int fd)
111{
112 struct fd irqfd;
113 struct eventfd_ctx *ctx;
114 struct virqfd *virqfd;
115 int ret = 0;
116 __poll_t events;
117
118 virqfd = kzalloc(sizeof(*virqfd), GFP_KERNEL);
119 if (!virqfd)
120 return -ENOMEM;
121
122 virqfd->pvirqfd = pvirqfd;
123 virqfd->opaque = opaque;
124 virqfd->handler = handler;
125 virqfd->thread = thread;
126 virqfd->data = data;
127
128 INIT_WORK(&virqfd->shutdown, virqfd_shutdown);
129 INIT_WORK(&virqfd->inject, virqfd_inject);
130
131 irqfd = fdget(fd);
132 if (!irqfd.file) {
133 ret = -EBADF;
134 goto err_fd;
135 }
136
137 ctx = eventfd_ctx_fileget(irqfd.file);
138 if (IS_ERR(ctx)) {
139 ret = PTR_ERR(ctx);
140 goto err_ctx;
141 }
142
143 virqfd->eventfd = ctx;
144
145 /*
146 * virqfds can be released by closing the eventfd or directly
147 * through ioctl. These are both done through a workqueue, so
148 * we update the pointer to the virqfd under lock to avoid
149 * pushing multiple jobs to release the same virqfd.
150 */
151 spin_lock_irq(&virqfd_lock);
152
153 if (*pvirqfd) {
154 spin_unlock_irq(&virqfd_lock);
155 ret = -EBUSY;
156 goto err_busy;
157 }
158 *pvirqfd = virqfd;
159
160 spin_unlock_irq(&virqfd_lock);
161
162 /*
163 * Install our own custom wake-up handling so we are notified via
164 * a callback whenever someone signals the underlying eventfd.
165 */
166 init_waitqueue_func_entry(&virqfd->wait, virqfd_wakeup);
167 init_poll_funcptr(&virqfd->pt, virqfd_ptable_queue_proc);
168
169 events = vfs_poll(irqfd.file, &virqfd->pt);
170
171 /*
172 * Check if there was an event already pending on the eventfd
173 * before we registered and trigger it as if we didn't miss it.
174 */
175 if (events & EPOLLIN) {
176 if ((!handler || handler(opaque, data)) && thread)
177 schedule_work(&virqfd->inject);
178 }
179
180 /*
181 * Do not drop the file until the irqfd is fully initialized,
182 * otherwise we might race against the EPOLLHUP.
183 */
184 fdput(irqfd);
185
186 return 0;
187err_busy:
188 eventfd_ctx_put(ctx);
189err_ctx:
190 fdput(irqfd);
191err_fd:
192 kfree(virqfd);
193
194 return ret;
195}
196EXPORT_SYMBOL_GPL(vfio_virqfd_enable);
197
198void vfio_virqfd_disable(struct virqfd **pvirqfd)
199{
200 unsigned long flags;
201
202 spin_lock_irqsave(&virqfd_lock, flags);
203
204 if (*pvirqfd) {
205 virqfd_deactivate(*pvirqfd);
206 *pvirqfd = NULL;
207 }
208
209 spin_unlock_irqrestore(&virqfd_lock, flags);
210
211 /*
212 * Block until we know all outstanding shutdown jobs have completed.
213 * Even if we don't queue the job, flush the wq to be sure it's
214 * been released.
215 */
216 flush_workqueue(vfio_irqfd_cleanup_wq);
217}
218EXPORT_SYMBOL_GPL(vfio_virqfd_disable);
219
220module_init(vfio_virqfd_init);
221module_exit(vfio_virqfd_exit);
222
223MODULE_VERSION(DRIVER_VERSION);
224MODULE_LICENSE("GPL v2");
225MODULE_AUTHOR(DRIVER_AUTHOR);
226MODULE_DESCRIPTION(DRIVER_DESC);
227