1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * VFIO generic eventfd code for IRQFD support.
4 * Derived from drivers/vfio/pci/vfio_pci_intrs.c
5 *
6 * Copyright (C) 2012 Red Hat, Inc. All rights reserved.
7 * Author: Alex Williamson <alex.williamson@redhat.com>
8 */
9
10 #include <linux/vfio.h>
11 #include <linux/eventfd.h>
12 #include <linux/file.h>
13 #include <linux/module.h>
14 #include <linux/slab.h>
15
16 #define DRIVER_VERSION "0.1"
17 #define DRIVER_AUTHOR "Alex Williamson <alex.williamson@redhat.com>"
18 #define DRIVER_DESC "IRQFD support for VFIO bus drivers"
19
20 static struct workqueue_struct *vfio_irqfd_cleanup_wq;
21 static DEFINE_SPINLOCK(virqfd_lock);
22
vfio_virqfd_init(void)23 static int __init vfio_virqfd_init(void)
24 {
25 vfio_irqfd_cleanup_wq =
26 create_singlethread_workqueue("vfio-irqfd-cleanup");
27 if (!vfio_irqfd_cleanup_wq)
28 return -ENOMEM;
29
30 return 0;
31 }
32
vfio_virqfd_exit(void)33 static void __exit vfio_virqfd_exit(void)
34 {
35 destroy_workqueue(vfio_irqfd_cleanup_wq);
36 }
37
virqfd_deactivate(struct virqfd * virqfd)38 static void virqfd_deactivate(struct virqfd *virqfd)
39 {
40 queue_work(vfio_irqfd_cleanup_wq, &virqfd->shutdown);
41 }
42
virqfd_wakeup(wait_queue_entry_t * wait,unsigned mode,int sync,void * key)43 static int virqfd_wakeup(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
44 {
45 struct virqfd *virqfd = container_of(wait, struct virqfd, wait);
46 __poll_t flags = key_to_poll(key);
47
48 if (flags & EPOLLIN) {
49 /* An event has been signaled, call function */
50 if ((!virqfd->handler ||
51 virqfd->handler(virqfd->opaque, virqfd->data)) &&
52 virqfd->thread)
53 schedule_work(&virqfd->inject);
54 }
55
56 if (flags & EPOLLHUP) {
57 unsigned long flags;
58 spin_lock_irqsave(&virqfd_lock, flags);
59
60 /*
61 * The eventfd is closing, if the virqfd has not yet been
62 * queued for release, as determined by testing whether the
63 * virqfd pointer to it is still valid, queue it now. As
64 * with kvm irqfds, we know we won't race against the virqfd
65 * going away because we hold the lock to get here.
66 */
67 if (*(virqfd->pvirqfd) == virqfd) {
68 *(virqfd->pvirqfd) = NULL;
69 virqfd_deactivate(virqfd);
70 }
71
72 spin_unlock_irqrestore(&virqfd_lock, flags);
73 }
74
75 return 0;
76 }
77
virqfd_ptable_queue_proc(struct file * file,wait_queue_head_t * wqh,poll_table * pt)78 static void virqfd_ptable_queue_proc(struct file *file,
79 wait_queue_head_t *wqh, poll_table *pt)
80 {
81 struct virqfd *virqfd = container_of(pt, struct virqfd, pt);
82 add_wait_queue(wqh, &virqfd->wait);
83 }
84
virqfd_shutdown(struct work_struct * work)85 static void virqfd_shutdown(struct work_struct *work)
86 {
87 struct virqfd *virqfd = container_of(work, struct virqfd, shutdown);
88 u64 cnt;
89
90 eventfd_ctx_remove_wait_queue(virqfd->eventfd, &virqfd->wait, &cnt);
91 flush_work(&virqfd->inject);
92 eventfd_ctx_put(virqfd->eventfd);
93
94 kfree(virqfd);
95 }
96
virqfd_inject(struct work_struct * work)97 static void virqfd_inject(struct work_struct *work)
98 {
99 struct virqfd *virqfd = container_of(work, struct virqfd, inject);
100 if (virqfd->thread)
101 virqfd->thread(virqfd->opaque, virqfd->data);
102 }
103
vfio_virqfd_enable(void * opaque,int (* handler)(void *,void *),void (* thread)(void *,void *),void * data,struct virqfd ** pvirqfd,int fd)104 int vfio_virqfd_enable(void *opaque,
105 int (*handler)(void *, void *),
106 void (*thread)(void *, void *),
107 void *data, struct virqfd **pvirqfd, int fd)
108 {
109 struct fd irqfd;
110 struct eventfd_ctx *ctx;
111 struct virqfd *virqfd;
112 int ret = 0;
113 __poll_t events;
114
115 virqfd = kzalloc(sizeof(*virqfd), GFP_KERNEL);
116 if (!virqfd)
117 return -ENOMEM;
118
119 virqfd->pvirqfd = pvirqfd;
120 virqfd->opaque = opaque;
121 virqfd->handler = handler;
122 virqfd->thread = thread;
123 virqfd->data = data;
124
125 INIT_WORK(&virqfd->shutdown, virqfd_shutdown);
126 INIT_WORK(&virqfd->inject, virqfd_inject);
127
128 irqfd = fdget(fd);
129 if (!irqfd.file) {
130 ret = -EBADF;
131 goto err_fd;
132 }
133
134 ctx = eventfd_ctx_fileget(irqfd.file);
135 if (IS_ERR(ctx)) {
136 ret = PTR_ERR(ctx);
137 goto err_ctx;
138 }
139
140 virqfd->eventfd = ctx;
141
142 /*
143 * virqfds can be released by closing the eventfd or directly
144 * through ioctl. These are both done through a workqueue, so
145 * we update the pointer to the virqfd under lock to avoid
146 * pushing multiple jobs to release the same virqfd.
147 */
148 spin_lock_irq(&virqfd_lock);
149
150 if (*pvirqfd) {
151 spin_unlock_irq(&virqfd_lock);
152 ret = -EBUSY;
153 goto err_busy;
154 }
155 *pvirqfd = virqfd;
156
157 spin_unlock_irq(&virqfd_lock);
158
159 /*
160 * Install our own custom wake-up handling so we are notified via
161 * a callback whenever someone signals the underlying eventfd.
162 */
163 init_waitqueue_func_entry(&virqfd->wait, virqfd_wakeup);
164 init_poll_funcptr(&virqfd->pt, virqfd_ptable_queue_proc);
165
166 events = vfs_poll(irqfd.file, &virqfd->pt);
167
168 /*
169 * Check if there was an event already pending on the eventfd
170 * before we registered and trigger it as if we didn't miss it.
171 */
172 if (events & EPOLLIN) {
173 if ((!handler || handler(opaque, data)) && thread)
174 schedule_work(&virqfd->inject);
175 }
176
177 /*
178 * Do not drop the file until the irqfd is fully initialized,
179 * otherwise we might race against the EPOLLHUP.
180 */
181 fdput(irqfd);
182
183 return 0;
184 err_busy:
185 eventfd_ctx_put(ctx);
186 err_ctx:
187 fdput(irqfd);
188 err_fd:
189 kfree(virqfd);
190
191 return ret;
192 }
193 EXPORT_SYMBOL_GPL(vfio_virqfd_enable);
194
vfio_virqfd_disable(struct virqfd ** pvirqfd)195 void vfio_virqfd_disable(struct virqfd **pvirqfd)
196 {
197 unsigned long flags;
198
199 spin_lock_irqsave(&virqfd_lock, flags);
200
201 if (*pvirqfd) {
202 virqfd_deactivate(*pvirqfd);
203 *pvirqfd = NULL;
204 }
205
206 spin_unlock_irqrestore(&virqfd_lock, flags);
207
208 /*
209 * Block until we know all outstanding shutdown jobs have completed.
210 * Even if we don't queue the job, flush the wq to be sure it's
211 * been released.
212 */
213 flush_workqueue(vfio_irqfd_cleanup_wq);
214 }
215 EXPORT_SYMBOL_GPL(vfio_virqfd_disable);
216
217 module_init(vfio_virqfd_init);
218 module_exit(vfio_virqfd_exit);
219
220 MODULE_VERSION(DRIVER_VERSION);
221 MODULE_LICENSE("GPL v2");
222 MODULE_AUTHOR(DRIVER_AUTHOR);
223 MODULE_DESCRIPTION(DRIVER_DESC);
224
