xref: /openbmc/linux/drivers/xen/evtchn.c (revision e8e0929d) 
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/miscdevice.h>
42 #include <linux/major.h>
43 #include <linux/proc_fs.h>
44 #include <linux/stat.h>
45 #include <linux/poll.h>
46 #include <linux/irq.h>
47 #include <linux/init.h>
48 #include <linux/gfp.h>
49 #include <linux/mutex.h>
50 #include <linux/cpu.h>
51 #include <xen/events.h>
52 #include <xen/evtchn.h>
53 #include <asm/xen/hypervisor.h>
54 
55 struct per_user_data {
56 	struct mutex bind_mutex; /* serialize bind/unbind operations */
57 
58 	/* Notification ring, accessed via /dev/xen/evtchn. */
59 #define EVTCHN_RING_SIZE     (PAGE_SIZE / sizeof(evtchn_port_t))
60 #define EVTCHN_RING_MASK(_i) ((_i)&(EVTCHN_RING_SIZE-1))
61 	evtchn_port_t *ring;
62 	unsigned int ring_cons, ring_prod, ring_overflow;
63 	struct mutex ring_cons_mutex; /* protect against concurrent readers */
64 
65 	/* Processes wait on this queue when ring is empty. */
66 	wait_queue_head_t evtchn_wait;
67 	struct fasync_struct *evtchn_async_queue;
68 	const char *name;
69 };
70 
71 /* Who's bound to each port? */
72 static struct per_user_data *port_user[NR_EVENT_CHANNELS];
73 static DEFINE_SPINLOCK(port_user_lock); /* protects port_user[] and ring_prod */
74 
75 irqreturn_t evtchn_interrupt(int irq, void *data)
76 {
77 	unsigned int port = (unsigned long)data;
78 	struct per_user_data *u;
79 
80 	spin_lock(&port_user_lock);
81 
82 	u = port_user[port];
83 
84 	disable_irq_nosync(irq);
85 
86 	if ((u->ring_prod - u->ring_cons) < EVTCHN_RING_SIZE) {
87 		u->ring[EVTCHN_RING_MASK(u->ring_prod)] = port;
88 		wmb(); /* Ensure ring contents visible */
89 		if (u->ring_cons == u->ring_prod++) {
90 			wake_up_interruptible(&u->evtchn_wait);
91 			kill_fasync(&u->evtchn_async_queue,
92 				    SIGIO, POLL_IN);
93 		}
94 	} else {
95 		u->ring_overflow = 1;
96 	}
97 
98 	spin_unlock(&port_user_lock);
99 
100 	return IRQ_HANDLED;
101 }
102 
103 static ssize_t evtchn_read(struct file *file, char __user *buf,
104 			   size_t count, loff_t *ppos)
105 {
106 	int rc;
107 	unsigned int c, p, bytes1 = 0, bytes2 = 0;
108 	struct per_user_data *u = file->private_data;
109 
110 	/* Whole number of ports. */
111 	count &= ~(sizeof(evtchn_port_t)-1);
112 
113 	if (count == 0)
114 		return 0;
115 
116 	if (count > PAGE_SIZE)
117 		count = PAGE_SIZE;
118 
119 	for (;;) {
120 		mutex_lock(&u->ring_cons_mutex);
121 
122 		rc = -EFBIG;
123 		if (u->ring_overflow)
124 			goto unlock_out;
125 
126 		c = u->ring_cons;
127 		p = u->ring_prod;
128 		if (c != p)
129 			break;
130 
131 		mutex_unlock(&u->ring_cons_mutex);
132 
133 		if (file->f_flags & O_NONBLOCK)
134 			return -EAGAIN;
135 
136 		rc = wait_event_interruptible(u->evtchn_wait,
137 					      u->ring_cons != u->ring_prod);
138 		if (rc)
139 			return rc;
140 	}
141 
142 	/* Byte lengths of two chunks. Chunk split (if any) is at ring wrap. */
143 	if (((c ^ p) & EVTCHN_RING_SIZE) != 0) {
144 		bytes1 = (EVTCHN_RING_SIZE - EVTCHN_RING_MASK(c)) *
145 			sizeof(evtchn_port_t);
146 		bytes2 = EVTCHN_RING_MASK(p) * sizeof(evtchn_port_t);
147 	} else {
148 		bytes1 = (p - c) * sizeof(evtchn_port_t);
149 		bytes2 = 0;
150 	}
151 
152 	/* Truncate chunks according to caller's maximum byte count. */
153 	if (bytes1 > count) {
154 		bytes1 = count;
155 		bytes2 = 0;
156 	} else if ((bytes1 + bytes2) > count) {
157 		bytes2 = count - bytes1;
158 	}
159 
160 	rc = -EFAULT;
161 	rmb(); /* Ensure that we see the port before we copy it. */
162 	if (copy_to_user(buf, &u->ring[EVTCHN_RING_MASK(c)], bytes1) ||
163 	    ((bytes2 != 0) &&
164 	     copy_to_user(&buf[bytes1], &u->ring[0], bytes2)))
165 		goto unlock_out;
166 
167 	u->ring_cons += (bytes1 + bytes2) / sizeof(evtchn_port_t);
168 	rc = bytes1 + bytes2;
169 
170  unlock_out:
171 	mutex_unlock(&u->ring_cons_mutex);
172 	return rc;
173 }
174 
175 static ssize_t evtchn_write(struct file *file, const char __user *buf,
176 			    size_t count, loff_t *ppos)
177 {
178 	int rc, i;
179 	evtchn_port_t *kbuf = (evtchn_port_t *)__get_free_page(GFP_KERNEL);
180 	struct per_user_data *u = file->private_data;
181 
182 	if (kbuf == NULL)
183 		return -ENOMEM;
184 
185 	/* Whole number of ports. */
186 	count &= ~(sizeof(evtchn_port_t)-1);
187 
188 	rc = 0;
189 	if (count == 0)
190 		goto out;
191 
192 	if (count > PAGE_SIZE)
193 		count = PAGE_SIZE;
194 
195 	rc = -EFAULT;
196 	if (copy_from_user(kbuf, buf, count) != 0)
197 		goto out;
198 
199 	spin_lock_irq(&port_user_lock);
200 	for (i = 0; i < (count/sizeof(evtchn_port_t)); i++)
201 		if ((kbuf[i] < NR_EVENT_CHANNELS) && (port_user[kbuf[i]] == u))
202 			enable_irq(irq_from_evtchn(kbuf[i]));
203 	spin_unlock_irq(&port_user_lock);
204 
205 	rc = count;
206 
207  out:
208 	free_page((unsigned long)kbuf);
209 	return rc;
210 }
211 
212 static int evtchn_bind_to_user(struct per_user_data *u, int port)
213 {
214 	int rc = 0;
215 
216 	/*
217 	 * Ports are never reused, so every caller should pass in a
218 	 * unique port.
219 	 *
220 	 * (Locking not necessary because we haven't registered the
221 	 * interrupt handler yet, and our caller has already
222 	 * serialized bind operations.)
223 	 */
224 	BUG_ON(port_user[port] != NULL);
225 	port_user[port] = u;
226 
227 	rc = bind_evtchn_to_irqhandler(port, evtchn_interrupt, IRQF_DISABLED,
228 				       u->name, (void *)(unsigned long)port);
229 	if (rc >= 0)
230 		rc = 0;
231 
232 	return rc;
233 }
234 
235 static void evtchn_unbind_from_user(struct per_user_data *u, int port)
236 {
237 	int irq = irq_from_evtchn(port);
238 
239 	unbind_from_irqhandler(irq, (void *)(unsigned long)port);
240 
241 	/* make sure we unbind the irq handler before clearing the port */
242 	barrier();
243 
244 	port_user[port] = NULL;
245 }
246 
247 static long evtchn_ioctl(struct file *file,
248 			 unsigned int cmd, unsigned long arg)
249 {
250 	int rc;
251 	struct per_user_data *u = file->private_data;
252 	void __user *uarg = (void __user *) arg;
253 
254 	/* Prevent bind from racing with unbind */
255 	mutex_lock(&u->bind_mutex);
256 
257 	switch (cmd) {
258 	case IOCTL_EVTCHN_BIND_VIRQ: {
259 		struct ioctl_evtchn_bind_virq bind;
260 		struct evtchn_bind_virq bind_virq;
261 
262 		rc = -EFAULT;
263 		if (copy_from_user(&bind, uarg, sizeof(bind)))
264 			break;
265 
266 		bind_virq.virq = bind.virq;
267 		bind_virq.vcpu = 0;
268 		rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_virq,
269 						 &bind_virq);
270 		if (rc != 0)
271 			break;
272 
273 		rc = evtchn_bind_to_user(u, bind_virq.port);
274 		if (rc == 0)
275 			rc = bind_virq.port;
276 		break;
277 	}
278 
279 	case IOCTL_EVTCHN_BIND_INTERDOMAIN: {
280 		struct ioctl_evtchn_bind_interdomain bind;
281 		struct evtchn_bind_interdomain bind_interdomain;
282 
283 		rc = -EFAULT;
284 		if (copy_from_user(&bind, uarg, sizeof(bind)))
285 			break;
286 
287 		bind_interdomain.remote_dom  = bind.remote_domain;
288 		bind_interdomain.remote_port = bind.remote_port;
289 		rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_interdomain,
290 						 &bind_interdomain);
291 		if (rc != 0)
292 			break;
293 
294 		rc = evtchn_bind_to_user(u, bind_interdomain.local_port);
295 		if (rc == 0)
296 			rc = bind_interdomain.local_port;
297 		break;
298 	}
299 
300 	case IOCTL_EVTCHN_BIND_UNBOUND_PORT: {
301 		struct ioctl_evtchn_bind_unbound_port bind;
302 		struct evtchn_alloc_unbound alloc_unbound;
303 
304 		rc = -EFAULT;
305 		if (copy_from_user(&bind, uarg, sizeof(bind)))
306 			break;
307 
308 		alloc_unbound.dom        = DOMID_SELF;
309 		alloc_unbound.remote_dom = bind.remote_domain;
310 		rc = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound,
311 						 &alloc_unbound);
312 		if (rc != 0)
313 			break;
314 
315 		rc = evtchn_bind_to_user(u, alloc_unbound.port);
316 		if (rc == 0)
317 			rc = alloc_unbound.port;
318 		break;
319 	}
320 
321 	case IOCTL_EVTCHN_UNBIND: {
322 		struct ioctl_evtchn_unbind unbind;
323 
324 		rc = -EFAULT;
325 		if (copy_from_user(&unbind, uarg, sizeof(unbind)))
326 			break;
327 
328 		rc = -EINVAL;
329 		if (unbind.port >= NR_EVENT_CHANNELS)
330 			break;
331 
332 		spin_lock_irq(&port_user_lock);
333 
334 		rc = -ENOTCONN;
335 		if (port_user[unbind.port] != u) {
336 			spin_unlock_irq(&port_user_lock);
337 			break;
338 		}
339 
340 		evtchn_unbind_from_user(u, unbind.port);
341 
342 		spin_unlock_irq(&port_user_lock);
343 
344 		rc = 0;
345 		break;
346 	}
347 
348 	case IOCTL_EVTCHN_NOTIFY: {
349 		struct ioctl_evtchn_notify notify;
350 
351 		rc = -EFAULT;
352 		if (copy_from_user(&notify, uarg, sizeof(notify)))
353 			break;
354 
355 		if (notify.port >= NR_EVENT_CHANNELS) {
356 			rc = -EINVAL;
357 		} else if (port_user[notify.port] != u) {
358 			rc = -ENOTCONN;
359 		} else {
360 			notify_remote_via_evtchn(notify.port);
361 			rc = 0;
362 		}
363 		break;
364 	}
365 
366 	case IOCTL_EVTCHN_RESET: {
367 		/* Initialise the ring to empty. Clear errors. */
368 		mutex_lock(&u->ring_cons_mutex);
369 		spin_lock_irq(&port_user_lock);
370 		u->ring_cons = u->ring_prod = u->ring_overflow = 0;
371 		spin_unlock_irq(&port_user_lock);
372 		mutex_unlock(&u->ring_cons_mutex);
373 		rc = 0;
374 		break;
375 	}
376 
377 	default:
378 		rc = -ENOSYS;
379 		break;
380 	}
381 	mutex_unlock(&u->bind_mutex);
382 
383 	return rc;
384 }
385 
386 static unsigned int evtchn_poll(struct file *file, poll_table *wait)
387 {
388 	unsigned int mask = POLLOUT | POLLWRNORM;
389 	struct per_user_data *u = file->private_data;
390 
391 	poll_wait(file, &u->evtchn_wait, wait);
392 	if (u->ring_cons != u->ring_prod)
393 		mask |= POLLIN | POLLRDNORM;
394 	if (u->ring_overflow)
395 		mask = POLLERR;
396 	return mask;
397 }
398 
399 static int evtchn_fasync(int fd, struct file *filp, int on)
400 {
401 	struct per_user_data *u = filp->private_data;
402 	return fasync_helper(fd, filp, on, &u->evtchn_async_queue);
403 }
404 
405 static int evtchn_open(struct inode *inode, struct file *filp)
406 {
407 	struct per_user_data *u;
408 
409 	u = kzalloc(sizeof(*u), GFP_KERNEL);
410 	if (u == NULL)
411 		return -ENOMEM;
412 
413 	u->name = kasprintf(GFP_KERNEL, "evtchn:%s", current->comm);
414 	if (u->name == NULL) {
415 		kfree(u);
416 		return -ENOMEM;
417 	}
418 
419 	init_waitqueue_head(&u->evtchn_wait);
420 
421 	u->ring = (evtchn_port_t *)__get_free_page(GFP_KERNEL);
422 	if (u->ring == NULL) {
423 		kfree(u->name);
424 		kfree(u);
425 		return -ENOMEM;
426 	}
427 
428 	mutex_init(&u->bind_mutex);
429 	mutex_init(&u->ring_cons_mutex);
430 
431 	filp->private_data = u;
432 
433 	return 0;
434 }
435 
436 static int evtchn_release(struct inode *inode, struct file *filp)
437 {
438 	int i;
439 	struct per_user_data *u = filp->private_data;
440 
441 	spin_lock_irq(&port_user_lock);
442 
443 	free_page((unsigned long)u->ring);
444 
445 	for (i = 0; i < NR_EVENT_CHANNELS; i++) {
446 		if (port_user[i] != u)
447 			continue;
448 
449 		evtchn_unbind_from_user(port_user[i], i);
450 	}
451 
452 	spin_unlock_irq(&port_user_lock);
453 
454 	kfree(u->name);
455 	kfree(u);
456 
457 	return 0;
458 }
459 
460 static const struct file_operations evtchn_fops = {
461 	.owner   = THIS_MODULE,
462 	.read    = evtchn_read,
463 	.write   = evtchn_write,
464 	.unlocked_ioctl = evtchn_ioctl,
465 	.poll    = evtchn_poll,
466 	.fasync  = evtchn_fasync,
467 	.open    = evtchn_open,
468 	.release = evtchn_release,
469 };
470 
471 static struct miscdevice evtchn_miscdev = {
472 	.minor        = MISC_DYNAMIC_MINOR,
473 	.name         = "evtchn",
474 	.fops         = &evtchn_fops,
475 };
476 static int __init evtchn_init(void)
477 {
478 	int err;
479 
480 	if (!xen_domain())
481 		return -ENODEV;
482 
483 	spin_lock_init(&port_user_lock);
484 	memset(port_user, 0, sizeof(port_user));
485 
486 	/* Create '/dev/misc/evtchn'. */
487 	err = misc_register(&evtchn_miscdev);
488 	if (err != 0) {
489 		printk(KERN_ALERT "Could not register /dev/misc/evtchn\n");
490 		return err;
491 	}
492 
493 	printk(KERN_INFO "Event-channel device installed.\n");
494 
495 	return 0;
496 }
497 
498 static void __exit evtchn_cleanup(void)
499 {
500 	misc_deregister(&evtchn_miscdev);
501 }
502 
503 module_init(evtchn_init);
504 module_exit(evtchn_cleanup);
505 
506 MODULE_LICENSE("GPL");
507