xref: /openbmc/linux/drivers/xen/evtchn.c (revision 78c99ba1) 
1 /******************************************************************************
2  * evtchn.c
3  *
4  * Driver for receiving and demuxing event-channel signals.
5  *
6  * Copyright (c) 2004-2005, K A Fraser
7  * Multi-process extensions Copyright (c) 2004, Steven Smith
8  *
9  * This program is free software; you can redistribute it and/or
10  * modify it under the terms of the GNU General Public License version 2
11  * as published by the Free Software Foundation; or, when distributed
12  * separately from the Linux kernel or incorporated into other
13  * software packages, subject to the following license:
14  *
15  * Permission is hereby granted, free of charge, to any person obtaining a copy
16  * of this source file (the "Software"), to deal in the Software without
17  * restriction, including without limitation the rights to use, copy, modify,
18  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
19  * and to permit persons to whom the Software is furnished to do so, subject to
20  * the following conditions:
21  *
22  * The above copyright notice and this permission notice shall be included in
23  * all copies or substantial portions of the Software.
24  *
25  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
26  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
27  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
28  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
29  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
30  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
31  * IN THE SOFTWARE.
32  */
33 
34 #include <linux/module.h>
35 #include <linux/kernel.h>
36 #include <linux/sched.h>
37 #include <linux/slab.h>
38 #include <linux/string.h>
39 #include <linux/errno.h>
40 #include <linux/fs.h>
41 #include <linux/errno.h>
42 #include <linux/miscdevice.h>
43 #include <linux/major.h>
44 #include <linux/proc_fs.h>
45 #include <linux/stat.h>
46 #include <linux/poll.h>
47 #include <linux/irq.h>
48 #include <linux/init.h>
49 #include <linux/gfp.h>
50 #include <linux/mutex.h>
51 #include <linux/cpu.h>
52 #include <xen/events.h>
53 #include <xen/evtchn.h>
54 #include <asm/xen/hypervisor.h>
55 
56 struct per_user_data {
57 	struct mutex bind_mutex; /* serialize bind/unbind operations */
58 
59 	/* Notification ring, accessed via /dev/xen/evtchn. */
60 #define EVTCHN_RING_SIZE     (PAGE_SIZE / sizeof(evtchn_port_t))
61 #define EVTCHN_RING_MASK(_i) ((_i)&(EVTCHN_RING_SIZE-1))
62 	evtchn_port_t *ring;
63 	unsigned int ring_cons, ring_prod, ring_overflow;
64 	struct mutex ring_cons_mutex; /* protect against concurrent readers */
65 
66 	/* Processes wait on this queue when ring is empty. */
67 	wait_queue_head_t evtchn_wait;
68 	struct fasync_struct *evtchn_async_queue;
69 	const char *name;
70 };
71 
72 /* Who's bound to each port? */
73 static struct per_user_data *port_user[NR_EVENT_CHANNELS];
74 static DEFINE_SPINLOCK(port_user_lock); /* protects port_user[] and ring_prod */
75 
76 irqreturn_t evtchn_interrupt(int irq, void *data)
77 {
78 	unsigned int port = (unsigned long)data;
79 	struct per_user_data *u;
80 
81 	spin_lock(&port_user_lock);
82 
83 	u = port_user[port];
84 
85 	disable_irq_nosync(irq);
86 
87 	if ((u->ring_prod - u->ring_cons) < EVTCHN_RING_SIZE) {
88 		u->ring[EVTCHN_RING_MASK(u->ring_prod)] = port;
89 		wmb(); /* Ensure ring contents visible */
90 		if (u->ring_cons == u->ring_prod++) {
91 			wake_up_interruptible(&u->evtchn_wait);
92 			kill_fasync(&u->evtchn_async_queue,
93 				    SIGIO, POLL_IN);
94 		}
95 	} else {
96 		u->ring_overflow = 1;
97 	}
98 
99 	spin_unlock(&port_user_lock);
100 
101 	return IRQ_HANDLED;
102 }
103 
104 static ssize_t evtchn_read(struct file *file, char __user *buf,
105 			   size_t count, loff_t *ppos)
106 {
107 	int rc;
108 	unsigned int c, p, bytes1 = 0, bytes2 = 0;
109 	struct per_user_data *u = file->private_data;
110 
111 	/* Whole number of ports. */
112 	count &= ~(sizeof(evtchn_port_t)-1);
113 
114 	if (count == 0)
115 		return 0;
116 
117 	if (count > PAGE_SIZE)
118 		count = PAGE_SIZE;
119 
120 	for (;;) {
121 		mutex_lock(&u->ring_cons_mutex);
122 
123 		rc = -EFBIG;
124 		if (u->ring_overflow)
125 			goto unlock_out;
126 
127 		c = u->ring_cons;
128 		p = u->ring_prod;
129 		if (c != p)
130 			break;
131 
132 		mutex_unlock(&u->ring_cons_mutex);
133 
134 		if (file->f_flags & O_NONBLOCK)
135 			return -EAGAIN;
136 
137 		rc = wait_event_interruptible(u->evtchn_wait,
138 					      u->ring_cons != u->ring_prod);
139 		if (rc)
140 			return rc;
141 	}
142 
143 	/* Byte lengths of two chunks. Chunk split (if any) is at ring wrap. */
144 	if (((c ^ p) & EVTCHN_RING_SIZE) != 0) {
145 		bytes1 = (EVTCHN_RING_SIZE - EVTCHN_RING_MASK(c)) *
146 			sizeof(evtchn_port_t);
147 		bytes2 = EVTCHN_RING_MASK(p) * sizeof(evtchn_port_t);
148 	} else {
149 		bytes1 = (p - c) * sizeof(evtchn_port_t);
150 		bytes2 = 0;
151 	}
152 
153 	/* Truncate chunks according to caller's maximum byte count. */
154 	if (bytes1 > count) {
155 		bytes1 = count;
156 		bytes2 = 0;
157 	} else if ((bytes1 + bytes2) > count) {
158 		bytes2 = count - bytes1;
159 	}
160 
161 	rc = -EFAULT;
162 	rmb(); /* Ensure that we see the port before we copy it. */
163 	if (copy_to_user(buf, &u->ring[EVTCHN_RING_MASK(c)], bytes1) ||
164 	    ((bytes2 != 0) &&
165 	     copy_to_user(&buf[bytes1], &u->ring[0], bytes2)))
166 		goto unlock_out;
167 
168 	u->ring_cons += (bytes1 + bytes2) / sizeof(evtchn_port_t);
169 	rc = bytes1 + bytes2;
170 
171  unlock_out:
172 	mutex_unlock(&u->ring_cons_mutex);
173 	return rc;
174 }
175 
176 static ssize_t evtchn_write(struct file *file, const char __user *buf,
177 			    size_t count, loff_t *ppos)
178 {
179 	int rc, i;
180 	evtchn_port_t *kbuf = (evtchn_port_t *)__get_free_page(GFP_KERNEL);
181 	struct per_user_data *u = file->private_data;
182 
183 	if (kbuf == NULL)
184 		return -ENOMEM;
185 
186 	/* Whole number of ports. */
187 	count &= ~(sizeof(evtchn_port_t)-1);
188 
189 	rc = 0;
190 	if (count == 0)
191 		goto out;
192 
193 	if (count > PAGE_SIZE)
194 		count = PAGE_SIZE;
195 
196 	rc = -EFAULT;
197 	if (copy_from_user(kbuf, buf, count) != 0)
198 		goto out;
199 
200 	spin_lock_irq(&port_user_lock);
201 	for (i = 0; i < (count/sizeof(evtchn_port_t)); i++)
202 		if ((kbuf[i] < NR_EVENT_CHANNELS) && (port_user[kbuf[i]] == u))
203 			enable_irq(irq_from_evtchn(kbuf[i]));
204 	spin_unlock_irq(&port_user_lock);
205 
206 	rc = count;
207 
208  out:
209 	free_page((unsigned long)kbuf);
210 	return rc;
211 }
212 
213 static int evtchn_bind_to_user(struct per_user_data *u, int port)
214 {
215 	int rc = 0;
216 
217 	/*
218 	 * Ports are never reused, so every caller should pass in a
219 	 * unique port.
220 	 *
221 	 * (Locking not necessary because we haven't registered the
222 	 * interrupt handler yet, and our caller has already
223 	 * serialized bind operations.)
224 	 */
225 	BUG_ON(port_user[port] != NULL);
226 	port_user[port] = u;
227 
228 	rc = bind_evtchn_to_irqhandler(port, evtchn_interrupt, IRQF_DISABLED,
229 				       u->name, (void *)(unsigned long)port);
230 	if (rc >= 0)
231 		rc = 0;
232 
233 	return rc;
234 }
235 
236 static void evtchn_unbind_from_user(struct per_user_data *u, int port)
237 {
238 	int irq = irq_from_evtchn(port);
239 
240 	unbind_from_irqhandler(irq, (void *)(unsigned long)port);
241 
242 	/* make sure we unbind the irq handler before clearing the port */
243 	barrier();
244 
245 	port_user[port] = NULL;
246 }
247 
248 static long evtchn_ioctl(struct file *file,
249 			 unsigned int cmd, unsigned long arg)
250 {
251 	int rc;
252 	struct per_user_data *u = file->private_data;
253 	void __user *uarg = (void __user *) arg;
254 
255 	/* Prevent bind from racing with unbind */
256 	mutex_lock(&u->bind_mutex);
257 
258 	switch (cmd) {
259 	case IOCTL_EVTCHN_BIND_VIRQ: {
260 		struct ioctl_evtchn_bind_virq bind;
261 		struct evtchn_bind_virq bind_virq;
262 
263 		rc = -EFAULT;
264 		if (copy_from_user(&bind, uarg, sizeof(bind)))
265 			break;
266 
267 		bind_virq.virq = bind.virq;
268 		bind_virq.vcpu = 0;
269 		rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_virq,
270 						 &bind_virq);
271 		if (rc != 0)
272 			break;
273 
274 		rc = evtchn_bind_to_user(u, bind_virq.port);
275 		if (rc == 0)
276 			rc = bind_virq.port;
277 		break;
278 	}
279 
280 	case IOCTL_EVTCHN_BIND_INTERDOMAIN: {
281 		struct ioctl_evtchn_bind_interdomain bind;
282 		struct evtchn_bind_interdomain bind_interdomain;
283 
284 		rc = -EFAULT;
285 		if (copy_from_user(&bind, uarg, sizeof(bind)))
286 			break;
287 
288 		bind_interdomain.remote_dom  = bind.remote_domain;
289 		bind_interdomain.remote_port = bind.remote_port;
290 		rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_interdomain,
291 						 &bind_interdomain);
292 		if (rc != 0)
293 			break;
294 
295 		rc = evtchn_bind_to_user(u, bind_interdomain.local_port);
296 		if (rc == 0)
297 			rc = bind_interdomain.local_port;
298 		break;
299 	}
300 
301 	case IOCTL_EVTCHN_BIND_UNBOUND_PORT: {
302 		struct ioctl_evtchn_bind_unbound_port bind;
303 		struct evtchn_alloc_unbound alloc_unbound;
304 
305 		rc = -EFAULT;
306 		if (copy_from_user(&bind, uarg, sizeof(bind)))
307 			break;
308 
309 		alloc_unbound.dom        = DOMID_SELF;
310 		alloc_unbound.remote_dom = bind.remote_domain;
311 		rc = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound,
312 						 &alloc_unbound);
313 		if (rc != 0)
314 			break;
315 
316 		rc = evtchn_bind_to_user(u, alloc_unbound.port);
317 		if (rc == 0)
318 			rc = alloc_unbound.port;
319 		break;
320 	}
321 
322 	case IOCTL_EVTCHN_UNBIND: {
323 		struct ioctl_evtchn_unbind unbind;
324 
325 		rc = -EFAULT;
326 		if (copy_from_user(&unbind, uarg, sizeof(unbind)))
327 			break;
328 
329 		rc = -EINVAL;
330 		if (unbind.port >= NR_EVENT_CHANNELS)
331 			break;
332 
333 		spin_lock_irq(&port_user_lock);
334 
335 		rc = -ENOTCONN;
336 		if (port_user[unbind.port] != u) {
337 			spin_unlock_irq(&port_user_lock);
338 			break;
339 		}
340 
341 		evtchn_unbind_from_user(u, unbind.port);
342 
343 		spin_unlock_irq(&port_user_lock);
344 
345 		rc = 0;
346 		break;
347 	}
348 
349 	case IOCTL_EVTCHN_NOTIFY: {
350 		struct ioctl_evtchn_notify notify;
351 
352 		rc = -EFAULT;
353 		if (copy_from_user(&notify, uarg, sizeof(notify)))
354 			break;
355 
356 		if (notify.port >= NR_EVENT_CHANNELS) {
357 			rc = -EINVAL;
358 		} else if (port_user[notify.port] != u) {
359 			rc = -ENOTCONN;
360 		} else {
361 			notify_remote_via_evtchn(notify.port);
362 			rc = 0;
363 		}
364 		break;
365 	}
366 
367 	case IOCTL_EVTCHN_RESET: {
368 		/* Initialise the ring to empty. Clear errors. */
369 		mutex_lock(&u->ring_cons_mutex);
370 		spin_lock_irq(&port_user_lock);
371 		u->ring_cons = u->ring_prod = u->ring_overflow = 0;
372 		spin_unlock_irq(&port_user_lock);
373 		mutex_unlock(&u->ring_cons_mutex);
374 		rc = 0;
375 		break;
376 	}
377 
378 	default:
379 		rc = -ENOSYS;
380 		break;
381 	}
382 	mutex_unlock(&u->bind_mutex);
383 
384 	return rc;
385 }
386 
387 static unsigned int evtchn_poll(struct file *file, poll_table *wait)
388 {
389 	unsigned int mask = POLLOUT | POLLWRNORM;
390 	struct per_user_data *u = file->private_data;
391 
392 	poll_wait(file, &u->evtchn_wait, wait);
393 	if (u->ring_cons != u->ring_prod)
394 		mask |= POLLIN | POLLRDNORM;
395 	if (u->ring_overflow)
396 		mask = POLLERR;
397 	return mask;
398 }
399 
400 static int evtchn_fasync(int fd, struct file *filp, int on)
401 {
402 	struct per_user_data *u = filp->private_data;
403 	return fasync_helper(fd, filp, on, &u->evtchn_async_queue);
404 }
405 
406 static int evtchn_open(struct inode *inode, struct file *filp)
407 {
408 	struct per_user_data *u;
409 
410 	u = kzalloc(sizeof(*u), GFP_KERNEL);
411 	if (u == NULL)
412 		return -ENOMEM;
413 
414 	u->name = kasprintf(GFP_KERNEL, "evtchn:%s", current->comm);
415 	if (u->name == NULL) {
416 		kfree(u);
417 		return -ENOMEM;
418 	}
419 
420 	init_waitqueue_head(&u->evtchn_wait);
421 
422 	u->ring = (evtchn_port_t *)__get_free_page(GFP_KERNEL);
423 	if (u->ring == NULL) {
424 		kfree(u->name);
425 		kfree(u);
426 		return -ENOMEM;
427 	}
428 
429 	mutex_init(&u->bind_mutex);
430 	mutex_init(&u->ring_cons_mutex);
431 
432 	filp->private_data = u;
433 
434 	return 0;
435 }
436 
437 static int evtchn_release(struct inode *inode, struct file *filp)
438 {
439 	int i;
440 	struct per_user_data *u = filp->private_data;
441 
442 	spin_lock_irq(&port_user_lock);
443 
444 	free_page((unsigned long)u->ring);
445 
446 	for (i = 0; i < NR_EVENT_CHANNELS; i++) {
447 		if (port_user[i] != u)
448 			continue;
449 
450 		evtchn_unbind_from_user(port_user[i], i);
451 	}
452 
453 	spin_unlock_irq(&port_user_lock);
454 
455 	kfree(u->name);
456 	kfree(u);
457 
458 	return 0;
459 }
460 
461 static const struct file_operations evtchn_fops = {
462 	.owner   = THIS_MODULE,
463 	.read    = evtchn_read,
464 	.write   = evtchn_write,
465 	.unlocked_ioctl = evtchn_ioctl,
466 	.poll    = evtchn_poll,
467 	.fasync  = evtchn_fasync,
468 	.open    = evtchn_open,
469 	.release = evtchn_release,
470 };
471 
472 static struct miscdevice evtchn_miscdev = {
473 	.minor        = MISC_DYNAMIC_MINOR,
474 	.name         = "evtchn",
475 	.fops         = &evtchn_fops,
476 };
477 static int __init evtchn_init(void)
478 {
479 	int err;
480 
481 	if (!xen_domain())
482 		return -ENODEV;
483 
484 	spin_lock_init(&port_user_lock);
485 	memset(port_user, 0, sizeof(port_user));
486 
487 	/* Create '/dev/misc/evtchn'. */
488 	err = misc_register(&evtchn_miscdev);
489 	if (err != 0) {
490 		printk(KERN_ALERT "Could not register /dev/misc/evtchn\n");
491 		return err;
492 	}
493 
494 	printk(KERN_INFO "Event-channel device installed.\n");
495 
496 	return 0;
497 }
498 
499 static void __exit evtchn_cleanup(void)
500 {
501 	misc_deregister(&evtchn_miscdev);
502 }
503 
504 module_init(evtchn_init);
505 module_exit(evtchn_cleanup);
506 
507 MODULE_LICENSE("GPL");
508