xref: /openbmc/linux/drivers/xen/evtchn.c (revision 9d56dd3b083a3bec56e9da35ce07baca81030b03)
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 
52 #include <xen/xen.h>
53 #include <xen/events.h>
54 #include <xen/evtchn.h>
55 #include <asm/xen/hypervisor.h>
56 
57 struct per_user_data {
58 	struct mutex bind_mutex; /* serialize bind/unbind operations */
59 
60 	/* Notification ring, accessed via /dev/xen/evtchn. */
61 #define EVTCHN_RING_SIZE     (PAGE_SIZE / sizeof(evtchn_port_t))
62 #define EVTCHN_RING_MASK(_i) ((_i)&(EVTCHN_RING_SIZE-1))
63 	evtchn_port_t *ring;
64 	unsigned int ring_cons, ring_prod, ring_overflow;
65 	struct mutex ring_cons_mutex; /* protect against concurrent readers */
66 
67 	/* Processes wait on this queue when ring is empty. */
68 	wait_queue_head_t evtchn_wait;
69 	struct fasync_struct *evtchn_async_queue;
70 	const char *name;
71 };
72 
73 /* Who's bound to each port? */
74 static struct per_user_data *port_user[NR_EVENT_CHANNELS];
75 static DEFINE_SPINLOCK(port_user_lock); /* protects port_user[] and ring_prod */
76 
77 irqreturn_t evtchn_interrupt(int irq, void *data)
78 {
79 	unsigned int port = (unsigned long)data;
80 	struct per_user_data *u;
81 
82 	spin_lock(&port_user_lock);
83 
84 	u = port_user[port];
85 
86 	disable_irq_nosync(irq);
87 
88 	if ((u->ring_prod - u->ring_cons) < EVTCHN_RING_SIZE) {
89 		u->ring[EVTCHN_RING_MASK(u->ring_prod)] = port;
90 		wmb(); /* Ensure ring contents visible */
91 		if (u->ring_cons == u->ring_prod++) {
92 			wake_up_interruptible(&u->evtchn_wait);
93 			kill_fasync(&u->evtchn_async_queue,
94 				    SIGIO, POLL_IN);
95 		}
96 	} else {
97 		u->ring_overflow = 1;
98 	}
99 
100 	spin_unlock(&port_user_lock);
101 
102 	return IRQ_HANDLED;
103 }
104 
105 static ssize_t evtchn_read(struct file *file, char __user *buf,
106 			   size_t count, loff_t *ppos)
107 {
108 	int rc;
109 	unsigned int c, p, bytes1 = 0, bytes2 = 0;
110 	struct per_user_data *u = file->private_data;
111 
112 	/* Whole number of ports. */
113 	count &= ~(sizeof(evtchn_port_t)-1);
114 
115 	if (count == 0)
116 		return 0;
117 
118 	if (count > PAGE_SIZE)
119 		count = PAGE_SIZE;
120 
121 	for (;;) {
122 		mutex_lock(&u->ring_cons_mutex);
123 
124 		rc = -EFBIG;
125 		if (u->ring_overflow)
126 			goto unlock_out;
127 
128 		c = u->ring_cons;
129 		p = u->ring_prod;
130 		if (c != p)
131 			break;
132 
133 		mutex_unlock(&u->ring_cons_mutex);
134 
135 		if (file->f_flags & O_NONBLOCK)
136 			return -EAGAIN;
137 
138 		rc = wait_event_interruptible(u->evtchn_wait,
139 					      u->ring_cons != u->ring_prod);
140 		if (rc)
141 			return rc;
142 	}
143 
144 	/* Byte lengths of two chunks. Chunk split (if any) is at ring wrap. */
145 	if (((c ^ p) & EVTCHN_RING_SIZE) != 0) {
146 		bytes1 = (EVTCHN_RING_SIZE - EVTCHN_RING_MASK(c)) *
147 			sizeof(evtchn_port_t);
148 		bytes2 = EVTCHN_RING_MASK(p) * sizeof(evtchn_port_t);
149 	} else {
150 		bytes1 = (p - c) * sizeof(evtchn_port_t);
151 		bytes2 = 0;
152 	}
153 
154 	/* Truncate chunks according to caller's maximum byte count. */
155 	if (bytes1 > count) {
156 		bytes1 = count;
157 		bytes2 = 0;
158 	} else if ((bytes1 + bytes2) > count) {
159 		bytes2 = count - bytes1;
160 	}
161 
162 	rc = -EFAULT;
163 	rmb(); /* Ensure that we see the port before we copy it. */
164 	if (copy_to_user(buf, &u->ring[EVTCHN_RING_MASK(c)], bytes1) ||
165 	    ((bytes2 != 0) &&
166 	     copy_to_user(&buf[bytes1], &u->ring[0], bytes2)))
167 		goto unlock_out;
168 
169 	u->ring_cons += (bytes1 + bytes2) / sizeof(evtchn_port_t);
170 	rc = bytes1 + bytes2;
171 
172  unlock_out:
173 	mutex_unlock(&u->ring_cons_mutex);
174 	return rc;
175 }
176 
177 static ssize_t evtchn_write(struct file *file, const char __user *buf,
178 			    size_t count, loff_t *ppos)
179 {
180 	int rc, i;
181 	evtchn_port_t *kbuf = (evtchn_port_t *)__get_free_page(GFP_KERNEL);
182 	struct per_user_data *u = file->private_data;
183 
184 	if (kbuf == NULL)
185 		return -ENOMEM;
186 
187 	/* Whole number of ports. */
188 	count &= ~(sizeof(evtchn_port_t)-1);
189 
190 	rc = 0;
191 	if (count == 0)
192 		goto out;
193 
194 	if (count > PAGE_SIZE)
195 		count = PAGE_SIZE;
196 
197 	rc = -EFAULT;
198 	if (copy_from_user(kbuf, buf, count) != 0)
199 		goto out;
200 
201 	spin_lock_irq(&port_user_lock);
202 	for (i = 0; i < (count/sizeof(evtchn_port_t)); i++)
203 		if ((kbuf[i] < NR_EVENT_CHANNELS) && (port_user[kbuf[i]] == u))
204 			enable_irq(irq_from_evtchn(kbuf[i]));
205 	spin_unlock_irq(&port_user_lock);
206 
207 	rc = count;
208 
209  out:
210 	free_page((unsigned long)kbuf);
211 	return rc;
212 }
213 
214 static int evtchn_bind_to_user(struct per_user_data *u, int port)
215 {
216 	int rc = 0;
217 
218 	/*
219 	 * Ports are never reused, so every caller should pass in a
220 	 * unique port.
221 	 *
222 	 * (Locking not necessary because we haven't registered the
223 	 * interrupt handler yet, and our caller has already
224 	 * serialized bind operations.)
225 	 */
226 	BUG_ON(port_user[port] != NULL);
227 	port_user[port] = u;
228 
229 	rc = bind_evtchn_to_irqhandler(port, evtchn_interrupt, IRQF_DISABLED,
230 				       u->name, (void *)(unsigned long)port);
231 	if (rc >= 0)
232 		rc = 0;
233 
234 	return rc;
235 }
236 
237 static void evtchn_unbind_from_user(struct per_user_data *u, int port)
238 {
239 	int irq = irq_from_evtchn(port);
240 
241 	unbind_from_irqhandler(irq, (void *)(unsigned long)port);
242 
243 	/* make sure we unbind the irq handler before clearing the port */
244 	barrier();
245 
246 	port_user[port] = NULL;
247 }
248 
249 static long evtchn_ioctl(struct file *file,
250 			 unsigned int cmd, unsigned long arg)
251 {
252 	int rc;
253 	struct per_user_data *u = file->private_data;
254 	void __user *uarg = (void __user *) arg;
255 
256 	/* Prevent bind from racing with unbind */
257 	mutex_lock(&u->bind_mutex);
258 
259 	switch (cmd) {
260 	case IOCTL_EVTCHN_BIND_VIRQ: {
261 		struct ioctl_evtchn_bind_virq bind;
262 		struct evtchn_bind_virq bind_virq;
263 
264 		rc = -EFAULT;
265 		if (copy_from_user(&bind, uarg, sizeof(bind)))
266 			break;
267 
268 		bind_virq.virq = bind.virq;
269 		bind_virq.vcpu = 0;
270 		rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_virq,
271 						 &bind_virq);
272 		if (rc != 0)
273 			break;
274 
275 		rc = evtchn_bind_to_user(u, bind_virq.port);
276 		if (rc == 0)
277 			rc = bind_virq.port;
278 		break;
279 	}
280 
281 	case IOCTL_EVTCHN_BIND_INTERDOMAIN: {
282 		struct ioctl_evtchn_bind_interdomain bind;
283 		struct evtchn_bind_interdomain bind_interdomain;
284 
285 		rc = -EFAULT;
286 		if (copy_from_user(&bind, uarg, sizeof(bind)))
287 			break;
288 
289 		bind_interdomain.remote_dom  = bind.remote_domain;
290 		bind_interdomain.remote_port = bind.remote_port;
291 		rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_interdomain,
292 						 &bind_interdomain);
293 		if (rc != 0)
294 			break;
295 
296 		rc = evtchn_bind_to_user(u, bind_interdomain.local_port);
297 		if (rc == 0)
298 			rc = bind_interdomain.local_port;
299 		break;
300 	}
301 
302 	case IOCTL_EVTCHN_BIND_UNBOUND_PORT: {
303 		struct ioctl_evtchn_bind_unbound_port bind;
304 		struct evtchn_alloc_unbound alloc_unbound;
305 
306 		rc = -EFAULT;
307 		if (copy_from_user(&bind, uarg, sizeof(bind)))
308 			break;
309 
310 		alloc_unbound.dom        = DOMID_SELF;
311 		alloc_unbound.remote_dom = bind.remote_domain;
312 		rc = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound,
313 						 &alloc_unbound);
314 		if (rc != 0)
315 			break;
316 
317 		rc = evtchn_bind_to_user(u, alloc_unbound.port);
318 		if (rc == 0)
319 			rc = alloc_unbound.port;
320 		break;
321 	}
322 
323 	case IOCTL_EVTCHN_UNBIND: {
324 		struct ioctl_evtchn_unbind unbind;
325 
326 		rc = -EFAULT;
327 		if (copy_from_user(&unbind, uarg, sizeof(unbind)))
328 			break;
329 
330 		rc = -EINVAL;
331 		if (unbind.port >= NR_EVENT_CHANNELS)
332 			break;
333 
334 		spin_lock_irq(&port_user_lock);
335 
336 		rc = -ENOTCONN;
337 		if (port_user[unbind.port] != u) {
338 			spin_unlock_irq(&port_user_lock);
339 			break;
340 		}
341 
342 		evtchn_unbind_from_user(u, unbind.port);
343 
344 		spin_unlock_irq(&port_user_lock);
345 
346 		rc = 0;
347 		break;
348 	}
349 
350 	case IOCTL_EVTCHN_NOTIFY: {
351 		struct ioctl_evtchn_notify notify;
352 
353 		rc = -EFAULT;
354 		if (copy_from_user(&notify, uarg, sizeof(notify)))
355 			break;
356 
357 		if (notify.port >= NR_EVENT_CHANNELS) {
358 			rc = -EINVAL;
359 		} else if (port_user[notify.port] != u) {
360 			rc = -ENOTCONN;
361 		} else {
362 			notify_remote_via_evtchn(notify.port);
363 			rc = 0;
364 		}
365 		break;
366 	}
367 
368 	case IOCTL_EVTCHN_RESET: {
369 		/* Initialise the ring to empty. Clear errors. */
370 		mutex_lock(&u->ring_cons_mutex);
371 		spin_lock_irq(&port_user_lock);
372 		u->ring_cons = u->ring_prod = u->ring_overflow = 0;
373 		spin_unlock_irq(&port_user_lock);
374 		mutex_unlock(&u->ring_cons_mutex);
375 		rc = 0;
376 		break;
377 	}
378 
379 	default:
380 		rc = -ENOSYS;
381 		break;
382 	}
383 	mutex_unlock(&u->bind_mutex);
384 
385 	return rc;
386 }
387 
388 static unsigned int evtchn_poll(struct file *file, poll_table *wait)
389 {
390 	unsigned int mask = POLLOUT | POLLWRNORM;
391 	struct per_user_data *u = file->private_data;
392 
393 	poll_wait(file, &u->evtchn_wait, wait);
394 	if (u->ring_cons != u->ring_prod)
395 		mask |= POLLIN | POLLRDNORM;
396 	if (u->ring_overflow)
397 		mask = POLLERR;
398 	return mask;
399 }
400 
401 static int evtchn_fasync(int fd, struct file *filp, int on)
402 {
403 	struct per_user_data *u = filp->private_data;
404 	return fasync_helper(fd, filp, on, &u->evtchn_async_queue);
405 }
406 
407 static int evtchn_open(struct inode *inode, struct file *filp)
408 {
409 	struct per_user_data *u;
410 
411 	u = kzalloc(sizeof(*u), GFP_KERNEL);
412 	if (u == NULL)
413 		return -ENOMEM;
414 
415 	u->name = kasprintf(GFP_KERNEL, "evtchn:%s", current->comm);
416 	if (u->name == NULL) {
417 		kfree(u);
418 		return -ENOMEM;
419 	}
420 
421 	init_waitqueue_head(&u->evtchn_wait);
422 
423 	u->ring = (evtchn_port_t *)__get_free_page(GFP_KERNEL);
424 	if (u->ring == NULL) {
425 		kfree(u->name);
426 		kfree(u);
427 		return -ENOMEM;
428 	}
429 
430 	mutex_init(&u->bind_mutex);
431 	mutex_init(&u->ring_cons_mutex);
432 
433 	filp->private_data = u;
434 
435 	return 0;
436 }
437 
438 static int evtchn_release(struct inode *inode, struct file *filp)
439 {
440 	int i;
441 	struct per_user_data *u = filp->private_data;
442 
443 	spin_lock_irq(&port_user_lock);
444 
445 	free_page((unsigned long)u->ring);
446 
447 	for (i = 0; i < NR_EVENT_CHANNELS; i++) {
448 		if (port_user[i] != u)
449 			continue;
450 
451 		evtchn_unbind_from_user(port_user[i], i);
452 	}
453 
454 	spin_unlock_irq(&port_user_lock);
455 
456 	kfree(u->name);
457 	kfree(u);
458 
459 	return 0;
460 }
461 
462 static const struct file_operations evtchn_fops = {
463 	.owner   = THIS_MODULE,
464 	.read    = evtchn_read,
465 	.write   = evtchn_write,
466 	.unlocked_ioctl = evtchn_ioctl,
467 	.poll    = evtchn_poll,
468 	.fasync  = evtchn_fasync,
469 	.open    = evtchn_open,
470 	.release = evtchn_release,
471 };
472 
473 static struct miscdevice evtchn_miscdev = {
474 	.minor        = MISC_DYNAMIC_MINOR,
475 	.name         = "evtchn",
476 	.fops         = &evtchn_fops,
477 };
478 static int __init evtchn_init(void)
479 {
480 	int err;
481 
482 	if (!xen_domain())
483 		return -ENODEV;
484 
485 	spin_lock_init(&port_user_lock);
486 	memset(port_user, 0, sizeof(port_user));
487 
488 	/* Create '/dev/misc/evtchn'. */
489 	err = misc_register(&evtchn_miscdev);
490 	if (err != 0) {
491 		printk(KERN_ALERT "Could not register /dev/misc/evtchn\n");
492 		return err;
493 	}
494 
495 	printk(KERN_INFO "Event-channel device installed.\n");
496 
497 	return 0;
498 }
499 
500 static void __exit evtchn_cleanup(void)
501 {
502 	misc_deregister(&evtchn_miscdev);
503 }
504 
505 module_init(evtchn_init);
506 module_exit(evtchn_cleanup);
507 
508 MODULE_LICENSE("GPL");
509