1 /******************************************************************************
2  * Talks to Xen Store to figure out what devices we have.
3  *
4  * Copyright (C) 2005 Rusty Russell, IBM Corporation
5  * Copyright (C) 2005 Mike Wray, Hewlett-Packard
6  * Copyright (C) 2005, 2006 XenSource Ltd
7  *
8  * This program is free software; you can redistribute it and/or
9  * modify it under the terms of the GNU General Public License version 2
10  * as published by the Free Software Foundation; or, when distributed
11  * separately from the Linux kernel or incorporated into other
12  * software packages, subject to the following license:
13  *
14  * Permission is hereby granted, free of charge, to any person obtaining a copy
15  * of this source file (the "Software"), to deal in the Software without
16  * restriction, including without limitation the rights to use, copy, modify,
17  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
18  * and to permit persons to whom the Software is furnished to do so, subject to
19  * the following conditions:
20  *
21  * The above copyright notice and this permission notice shall be included in
22  * all copies or substantial portions of the Software.
23  *
24  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
25  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
26  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
27  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
28  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
29  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
30  * IN THE SOFTWARE.
31  */
32 
33 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
34 
35 #define DPRINTK(fmt, args...)				\
36 	pr_debug("xenbus_probe (%s:%d) " fmt ".\n",	\
37 		 __func__, __LINE__, ##args)
38 
39 #include <linux/kernel.h>
40 #include <linux/err.h>
41 #include <linux/string.h>
42 #include <linux/ctype.h>
43 #include <linux/fcntl.h>
44 #include <linux/mm.h>
45 #include <linux/proc_fs.h>
46 #include <linux/notifier.h>
47 #include <linux/kthread.h>
48 #include <linux/mutex.h>
49 #include <linux/io.h>
50 #include <linux/slab.h>
51 #include <linux/module.h>
52 
53 #include <asm/page.h>
54 #include <asm/pgtable.h>
55 #include <asm/xen/hypervisor.h>
56 
57 #include <xen/xen.h>
58 #include <xen/xenbus.h>
59 #include <xen/events.h>
60 #include <xen/xen-ops.h>
61 #include <xen/page.h>
62 
63 #include <xen/hvm.h>
64 
65 #include "xenbus.h"
66 
67 
68 int xen_store_evtchn;
69 EXPORT_SYMBOL_GPL(xen_store_evtchn);
70 
71 struct xenstore_domain_interface *xen_store_interface;
72 EXPORT_SYMBOL_GPL(xen_store_interface);
73 
74 enum xenstore_init xen_store_domain_type;
75 EXPORT_SYMBOL_GPL(xen_store_domain_type);
76 
77 static unsigned long xen_store_gfn;
78 
79 static BLOCKING_NOTIFIER_HEAD(xenstore_chain);
80 
81 /* If something in array of ids matches this device, return it. */
82 static const struct xenbus_device_id *
83 match_device(const struct xenbus_device_id *arr, struct xenbus_device *dev)
84 {
85 	for (; *arr->devicetype != '\0'; arr++) {
86 		if (!strcmp(arr->devicetype, dev->devicetype))
87 			return arr;
88 	}
89 	return NULL;
90 }
91 
92 int xenbus_match(struct device *_dev, struct device_driver *_drv)
93 {
94 	struct xenbus_driver *drv = to_xenbus_driver(_drv);
95 
96 	if (!drv->ids)
97 		return 0;
98 
99 	return match_device(drv->ids, to_xenbus_device(_dev)) != NULL;
100 }
101 EXPORT_SYMBOL_GPL(xenbus_match);
102 
103 
104 static void free_otherend_details(struct xenbus_device *dev)
105 {
106 	kfree(dev->otherend);
107 	dev->otherend = NULL;
108 }
109 
110 
111 static void free_otherend_watch(struct xenbus_device *dev)
112 {
113 	if (dev->otherend_watch.node) {
114 		unregister_xenbus_watch(&dev->otherend_watch);
115 		kfree(dev->otherend_watch.node);
116 		dev->otherend_watch.node = NULL;
117 	}
118 }
119 
120 
121 static int talk_to_otherend(struct xenbus_device *dev)
122 {
123 	struct xenbus_driver *drv = to_xenbus_driver(dev->dev.driver);
124 
125 	free_otherend_watch(dev);
126 	free_otherend_details(dev);
127 
128 	return drv->read_otherend_details(dev);
129 }
130 
131 
132 
133 static int watch_otherend(struct xenbus_device *dev)
134 {
135 	struct xen_bus_type *bus =
136 		container_of(dev->dev.bus, struct xen_bus_type, bus);
137 
138 	return xenbus_watch_pathfmt(dev, &dev->otherend_watch,
139 				    bus->otherend_changed,
140 				    "%s/%s", dev->otherend, "state");
141 }
142 
143 
144 int xenbus_read_otherend_details(struct xenbus_device *xendev,
145 				 char *id_node, char *path_node)
146 {
147 	int err = xenbus_gather(XBT_NIL, xendev->nodename,
148 				id_node, "%i", &xendev->otherend_id,
149 				path_node, NULL, &xendev->otherend,
150 				NULL);
151 	if (err) {
152 		xenbus_dev_fatal(xendev, err,
153 				 "reading other end details from %s",
154 				 xendev->nodename);
155 		return err;
156 	}
157 	if (strlen(xendev->otherend) == 0 ||
158 	    !xenbus_exists(XBT_NIL, xendev->otherend, "")) {
159 		xenbus_dev_fatal(xendev, -ENOENT,
160 				 "unable to read other end from %s.  "
161 				 "missing or inaccessible.",
162 				 xendev->nodename);
163 		free_otherend_details(xendev);
164 		return -ENOENT;
165 	}
166 
167 	return 0;
168 }
169 EXPORT_SYMBOL_GPL(xenbus_read_otherend_details);
170 
171 void xenbus_otherend_changed(struct xenbus_watch *watch,
172 			     const char *path, const char *token,
173 			     int ignore_on_shutdown)
174 {
175 	struct xenbus_device *dev =
176 		container_of(watch, struct xenbus_device, otherend_watch);
177 	struct xenbus_driver *drv = to_xenbus_driver(dev->dev.driver);
178 	enum xenbus_state state;
179 
180 	/* Protect us against watches firing on old details when the otherend
181 	   details change, say immediately after a resume. */
182 	if (!dev->otherend ||
183 	    strncmp(dev->otherend, path, strlen(dev->otherend))) {
184 		dev_dbg(&dev->dev, "Ignoring watch at %s\n", path);
185 		return;
186 	}
187 
188 	state = xenbus_read_driver_state(dev->otherend);
189 
190 	dev_dbg(&dev->dev, "state is %d, (%s), %s, %s\n",
191 		state, xenbus_strstate(state), dev->otherend_watch.node, path);
192 
193 	/*
194 	 * Ignore xenbus transitions during shutdown. This prevents us doing
195 	 * work that can fail e.g., when the rootfs is gone.
196 	 */
197 	if (system_state > SYSTEM_RUNNING) {
198 		if (ignore_on_shutdown && (state == XenbusStateClosing))
199 			xenbus_frontend_closed(dev);
200 		return;
201 	}
202 
203 	if (drv->otherend_changed)
204 		drv->otherend_changed(dev, state);
205 }
206 EXPORT_SYMBOL_GPL(xenbus_otherend_changed);
207 
208 int xenbus_dev_probe(struct device *_dev)
209 {
210 	struct xenbus_device *dev = to_xenbus_device(_dev);
211 	struct xenbus_driver *drv = to_xenbus_driver(_dev->driver);
212 	const struct xenbus_device_id *id;
213 	int err;
214 
215 	DPRINTK("%s", dev->nodename);
216 
217 	if (!drv->probe) {
218 		err = -ENODEV;
219 		goto fail;
220 	}
221 
222 	id = match_device(drv->ids, dev);
223 	if (!id) {
224 		err = -ENODEV;
225 		goto fail;
226 	}
227 
228 	err = talk_to_otherend(dev);
229 	if (err) {
230 		dev_warn(&dev->dev, "talk_to_otherend on %s failed.\n",
231 			 dev->nodename);
232 		return err;
233 	}
234 
235 	if (!try_module_get(drv->driver.owner)) {
236 		dev_warn(&dev->dev, "failed to acquire module reference on '%s'\n",
237 			 drv->driver.name);
238 		err = -ESRCH;
239 		goto fail;
240 	}
241 
242 	err = drv->probe(dev, id);
243 	if (err)
244 		goto fail_put;
245 
246 	err = watch_otherend(dev);
247 	if (err) {
248 		dev_warn(&dev->dev, "watch_otherend on %s failed.\n",
249 		       dev->nodename);
250 		return err;
251 	}
252 
253 	return 0;
254 fail_put:
255 	module_put(drv->driver.owner);
256 fail:
257 	xenbus_dev_error(dev, err, "xenbus_dev_probe on %s", dev->nodename);
258 	return err;
259 }
260 EXPORT_SYMBOL_GPL(xenbus_dev_probe);
261 
262 int xenbus_dev_remove(struct device *_dev)
263 {
264 	struct xenbus_device *dev = to_xenbus_device(_dev);
265 	struct xenbus_driver *drv = to_xenbus_driver(_dev->driver);
266 
267 	DPRINTK("%s", dev->nodename);
268 
269 	free_otherend_watch(dev);
270 
271 	if (drv->remove)
272 		drv->remove(dev);
273 
274 	module_put(drv->driver.owner);
275 
276 	free_otherend_details(dev);
277 
278 	/*
279 	 * If the toolstack has forced the device state to closing then set
280 	 * the state to closed now to allow it to be cleaned up.
281 	 * Similarly, if the driver does not support re-bind, set the
282 	 * closed.
283 	 */
284 	if (!drv->allow_rebind ||
285 	    xenbus_read_driver_state(dev->nodename) == XenbusStateClosing)
286 		xenbus_switch_state(dev, XenbusStateClosed);
287 
288 	return 0;
289 }
290 EXPORT_SYMBOL_GPL(xenbus_dev_remove);
291 
292 int xenbus_register_driver_common(struct xenbus_driver *drv,
293 				  struct xen_bus_type *bus,
294 				  struct module *owner, const char *mod_name)
295 {
296 	drv->driver.name = drv->name ? drv->name : drv->ids[0].devicetype;
297 	drv->driver.bus = &bus->bus;
298 	drv->driver.owner = owner;
299 	drv->driver.mod_name = mod_name;
300 
301 	return driver_register(&drv->driver);
302 }
303 EXPORT_SYMBOL_GPL(xenbus_register_driver_common);
304 
305 void xenbus_unregister_driver(struct xenbus_driver *drv)
306 {
307 	driver_unregister(&drv->driver);
308 }
309 EXPORT_SYMBOL_GPL(xenbus_unregister_driver);
310 
311 struct xb_find_info {
312 	struct xenbus_device *dev;
313 	const char *nodename;
314 };
315 
316 static int cmp_dev(struct device *dev, void *data)
317 {
318 	struct xenbus_device *xendev = to_xenbus_device(dev);
319 	struct xb_find_info *info = data;
320 
321 	if (!strcmp(xendev->nodename, info->nodename)) {
322 		info->dev = xendev;
323 		get_device(dev);
324 		return 1;
325 	}
326 	return 0;
327 }
328 
329 static struct xenbus_device *xenbus_device_find(const char *nodename,
330 						struct bus_type *bus)
331 {
332 	struct xb_find_info info = { .dev = NULL, .nodename = nodename };
333 
334 	bus_for_each_dev(bus, NULL, &info, cmp_dev);
335 	return info.dev;
336 }
337 
338 static int cleanup_dev(struct device *dev, void *data)
339 {
340 	struct xenbus_device *xendev = to_xenbus_device(dev);
341 	struct xb_find_info *info = data;
342 	int len = strlen(info->nodename);
343 
344 	DPRINTK("%s", info->nodename);
345 
346 	/* Match the info->nodename path, or any subdirectory of that path. */
347 	if (strncmp(xendev->nodename, info->nodename, len))
348 		return 0;
349 
350 	/* If the node name is longer, ensure it really is a subdirectory. */
351 	if ((strlen(xendev->nodename) > len) && (xendev->nodename[len] != '/'))
352 		return 0;
353 
354 	info->dev = xendev;
355 	get_device(dev);
356 	return 1;
357 }
358 
359 static void xenbus_cleanup_devices(const char *path, struct bus_type *bus)
360 {
361 	struct xb_find_info info = { .nodename = path };
362 
363 	do {
364 		info.dev = NULL;
365 		bus_for_each_dev(bus, NULL, &info, cleanup_dev);
366 		if (info.dev) {
367 			device_unregister(&info.dev->dev);
368 			put_device(&info.dev->dev);
369 		}
370 	} while (info.dev);
371 }
372 
373 static void xenbus_dev_release(struct device *dev)
374 {
375 	if (dev)
376 		kfree(to_xenbus_device(dev));
377 }
378 
379 static ssize_t nodename_show(struct device *dev,
380 			     struct device_attribute *attr, char *buf)
381 {
382 	return sprintf(buf, "%s\n", to_xenbus_device(dev)->nodename);
383 }
384 static DEVICE_ATTR_RO(nodename);
385 
386 static ssize_t devtype_show(struct device *dev,
387 			    struct device_attribute *attr, char *buf)
388 {
389 	return sprintf(buf, "%s\n", to_xenbus_device(dev)->devicetype);
390 }
391 static DEVICE_ATTR_RO(devtype);
392 
393 static ssize_t modalias_show(struct device *dev,
394 			     struct device_attribute *attr, char *buf)
395 {
396 	return sprintf(buf, "%s:%s\n", dev->bus->name,
397 		       to_xenbus_device(dev)->devicetype);
398 }
399 static DEVICE_ATTR_RO(modalias);
400 
401 static ssize_t state_show(struct device *dev,
402 			    struct device_attribute *attr, char *buf)
403 {
404 	return sprintf(buf, "%s\n",
405 			xenbus_strstate(to_xenbus_device(dev)->state));
406 }
407 static DEVICE_ATTR_RO(state);
408 
409 static struct attribute *xenbus_dev_attrs[] = {
410 	&dev_attr_nodename.attr,
411 	&dev_attr_devtype.attr,
412 	&dev_attr_modalias.attr,
413 	&dev_attr_state.attr,
414 	NULL,
415 };
416 
417 static const struct attribute_group xenbus_dev_group = {
418 	.attrs = xenbus_dev_attrs,
419 };
420 
421 const struct attribute_group *xenbus_dev_groups[] = {
422 	&xenbus_dev_group,
423 	NULL,
424 };
425 EXPORT_SYMBOL_GPL(xenbus_dev_groups);
426 
427 int xenbus_probe_node(struct xen_bus_type *bus,
428 		      const char *type,
429 		      const char *nodename)
430 {
431 	char devname[XEN_BUS_ID_SIZE];
432 	int err;
433 	struct xenbus_device *xendev;
434 	size_t stringlen;
435 	char *tmpstring;
436 
437 	enum xenbus_state state = xenbus_read_driver_state(nodename);
438 
439 	if (state != XenbusStateInitialising) {
440 		/* Device is not new, so ignore it.  This can happen if a
441 		   device is going away after switching to Closed.  */
442 		return 0;
443 	}
444 
445 	stringlen = strlen(nodename) + 1 + strlen(type) + 1;
446 	xendev = kzalloc(sizeof(*xendev) + stringlen, GFP_KERNEL);
447 	if (!xendev)
448 		return -ENOMEM;
449 
450 	xendev->state = XenbusStateInitialising;
451 
452 	/* Copy the strings into the extra space. */
453 
454 	tmpstring = (char *)(xendev + 1);
455 	strcpy(tmpstring, nodename);
456 	xendev->nodename = tmpstring;
457 
458 	tmpstring += strlen(tmpstring) + 1;
459 	strcpy(tmpstring, type);
460 	xendev->devicetype = tmpstring;
461 	init_completion(&xendev->down);
462 
463 	xendev->dev.bus = &bus->bus;
464 	xendev->dev.release = xenbus_dev_release;
465 
466 	err = bus->get_bus_id(devname, xendev->nodename);
467 	if (err)
468 		goto fail;
469 
470 	dev_set_name(&xendev->dev, "%s", devname);
471 
472 	/* Register with generic device framework. */
473 	err = device_register(&xendev->dev);
474 	if (err) {
475 		put_device(&xendev->dev);
476 		xendev = NULL;
477 		goto fail;
478 	}
479 
480 	return 0;
481 fail:
482 	kfree(xendev);
483 	return err;
484 }
485 EXPORT_SYMBOL_GPL(xenbus_probe_node);
486 
487 static int xenbus_probe_device_type(struct xen_bus_type *bus, const char *type)
488 {
489 	int err = 0;
490 	char **dir;
491 	unsigned int dir_n = 0;
492 	int i;
493 
494 	dir = xenbus_directory(XBT_NIL, bus->root, type, &dir_n);
495 	if (IS_ERR(dir))
496 		return PTR_ERR(dir);
497 
498 	for (i = 0; i < dir_n; i++) {
499 		err = bus->probe(bus, type, dir[i]);
500 		if (err)
501 			break;
502 	}
503 
504 	kfree(dir);
505 	return err;
506 }
507 
508 int xenbus_probe_devices(struct xen_bus_type *bus)
509 {
510 	int err = 0;
511 	char **dir;
512 	unsigned int i, dir_n;
513 
514 	dir = xenbus_directory(XBT_NIL, bus->root, "", &dir_n);
515 	if (IS_ERR(dir))
516 		return PTR_ERR(dir);
517 
518 	for (i = 0; i < dir_n; i++) {
519 		err = xenbus_probe_device_type(bus, dir[i]);
520 		if (err)
521 			break;
522 	}
523 
524 	kfree(dir);
525 	return err;
526 }
527 EXPORT_SYMBOL_GPL(xenbus_probe_devices);
528 
529 static unsigned int char_count(const char *str, char c)
530 {
531 	unsigned int i, ret = 0;
532 
533 	for (i = 0; str[i]; i++)
534 		if (str[i] == c)
535 			ret++;
536 	return ret;
537 }
538 
539 static int strsep_len(const char *str, char c, unsigned int len)
540 {
541 	unsigned int i;
542 
543 	for (i = 0; str[i]; i++)
544 		if (str[i] == c) {
545 			if (len == 0)
546 				return i;
547 			len--;
548 		}
549 	return (len == 0) ? i : -ERANGE;
550 }
551 
552 void xenbus_dev_changed(const char *node, struct xen_bus_type *bus)
553 {
554 	int exists, rootlen;
555 	struct xenbus_device *dev;
556 	char type[XEN_BUS_ID_SIZE];
557 	const char *p, *root;
558 
559 	if (char_count(node, '/') < 2)
560 		return;
561 
562 	exists = xenbus_exists(XBT_NIL, node, "");
563 	if (!exists) {
564 		xenbus_cleanup_devices(node, &bus->bus);
565 		return;
566 	}
567 
568 	/* backend/<type>/... or device/<type>/... */
569 	p = strchr(node, '/') + 1;
570 	snprintf(type, XEN_BUS_ID_SIZE, "%.*s", (int)strcspn(p, "/"), p);
571 	type[XEN_BUS_ID_SIZE-1] = '\0';
572 
573 	rootlen = strsep_len(node, '/', bus->levels);
574 	if (rootlen < 0)
575 		return;
576 	root = kasprintf(GFP_KERNEL, "%.*s", rootlen, node);
577 	if (!root)
578 		return;
579 
580 	dev = xenbus_device_find(root, &bus->bus);
581 	if (!dev)
582 		xenbus_probe_node(bus, type, root);
583 	else
584 		put_device(&dev->dev);
585 
586 	kfree(root);
587 }
588 EXPORT_SYMBOL_GPL(xenbus_dev_changed);
589 
590 int xenbus_dev_suspend(struct device *dev)
591 {
592 	int err = 0;
593 	struct xenbus_driver *drv;
594 	struct xenbus_device *xdev
595 		= container_of(dev, struct xenbus_device, dev);
596 
597 	DPRINTK("%s", xdev->nodename);
598 
599 	if (dev->driver == NULL)
600 		return 0;
601 	drv = to_xenbus_driver(dev->driver);
602 	if (drv->suspend)
603 		err = drv->suspend(xdev);
604 	if (err)
605 		pr_warn("suspend %s failed: %i\n", dev_name(dev), err);
606 	return 0;
607 }
608 EXPORT_SYMBOL_GPL(xenbus_dev_suspend);
609 
610 int xenbus_dev_resume(struct device *dev)
611 {
612 	int err;
613 	struct xenbus_driver *drv;
614 	struct xenbus_device *xdev
615 		= container_of(dev, struct xenbus_device, dev);
616 
617 	DPRINTK("%s", xdev->nodename);
618 
619 	if (dev->driver == NULL)
620 		return 0;
621 	drv = to_xenbus_driver(dev->driver);
622 	err = talk_to_otherend(xdev);
623 	if (err) {
624 		pr_warn("resume (talk_to_otherend) %s failed: %i\n",
625 			dev_name(dev), err);
626 		return err;
627 	}
628 
629 	xdev->state = XenbusStateInitialising;
630 
631 	if (drv->resume) {
632 		err = drv->resume(xdev);
633 		if (err) {
634 			pr_warn("resume %s failed: %i\n", dev_name(dev), err);
635 			return err;
636 		}
637 	}
638 
639 	err = watch_otherend(xdev);
640 	if (err) {
641 		pr_warn("resume (watch_otherend) %s failed: %d.\n",
642 			dev_name(dev), err);
643 		return err;
644 	}
645 
646 	return 0;
647 }
648 EXPORT_SYMBOL_GPL(xenbus_dev_resume);
649 
650 int xenbus_dev_cancel(struct device *dev)
651 {
652 	/* Do nothing */
653 	DPRINTK("cancel");
654 	return 0;
655 }
656 EXPORT_SYMBOL_GPL(xenbus_dev_cancel);
657 
658 /* A flag to determine if xenstored is 'ready' (i.e. has started) */
659 int xenstored_ready;
660 
661 
662 int register_xenstore_notifier(struct notifier_block *nb)
663 {
664 	int ret = 0;
665 
666 	if (xenstored_ready > 0)
667 		ret = nb->notifier_call(nb, 0, NULL);
668 	else
669 		blocking_notifier_chain_register(&xenstore_chain, nb);
670 
671 	return ret;
672 }
673 EXPORT_SYMBOL_GPL(register_xenstore_notifier);
674 
675 void unregister_xenstore_notifier(struct notifier_block *nb)
676 {
677 	blocking_notifier_chain_unregister(&xenstore_chain, nb);
678 }
679 EXPORT_SYMBOL_GPL(unregister_xenstore_notifier);
680 
681 void xenbus_probe(struct work_struct *unused)
682 {
683 	xenstored_ready = 1;
684 
685 	/* Notify others that xenstore is up */
686 	blocking_notifier_call_chain(&xenstore_chain, 0, NULL);
687 }
688 EXPORT_SYMBOL_GPL(xenbus_probe);
689 
690 static int __init xenbus_probe_initcall(void)
691 {
692 	if (!xen_domain())
693 		return -ENODEV;
694 
695 	if (xen_initial_domain() || xen_hvm_domain())
696 		return 0;
697 
698 	xenbus_probe(NULL);
699 	return 0;
700 }
701 
702 device_initcall(xenbus_probe_initcall);
703 
704 /* Set up event channel for xenstored which is run as a local process
705  * (this is normally used only in dom0)
706  */
707 static int __init xenstored_local_init(void)
708 {
709 	int err = -ENOMEM;
710 	unsigned long page = 0;
711 	struct evtchn_alloc_unbound alloc_unbound;
712 
713 	/* Allocate Xenstore page */
714 	page = get_zeroed_page(GFP_KERNEL);
715 	if (!page)
716 		goto out_err;
717 
718 	xen_store_gfn = virt_to_gfn((void *)page);
719 
720 	/* Next allocate a local port which xenstored can bind to */
721 	alloc_unbound.dom        = DOMID_SELF;
722 	alloc_unbound.remote_dom = DOMID_SELF;
723 
724 	err = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound,
725 					  &alloc_unbound);
726 	if (err == -ENOSYS)
727 		goto out_err;
728 
729 	BUG_ON(err);
730 	xen_store_evtchn = alloc_unbound.port;
731 
732 	return 0;
733 
734  out_err:
735 	if (page != 0)
736 		free_page(page);
737 	return err;
738 }
739 
740 static int xenbus_resume_cb(struct notifier_block *nb,
741 			    unsigned long action, void *data)
742 {
743 	int err = 0;
744 
745 	if (xen_hvm_domain()) {
746 		uint64_t v = 0;
747 
748 		err = hvm_get_parameter(HVM_PARAM_STORE_EVTCHN, &v);
749 		if (!err && v)
750 			xen_store_evtchn = v;
751 		else
752 			pr_warn("Cannot update xenstore event channel: %d\n",
753 				err);
754 	} else
755 		xen_store_evtchn = xen_start_info->store_evtchn;
756 
757 	return err;
758 }
759 
760 static struct notifier_block xenbus_resume_nb = {
761 	.notifier_call = xenbus_resume_cb,
762 };
763 
764 static int __init xenbus_init(void)
765 {
766 	int err = 0;
767 	uint64_t v = 0;
768 	xen_store_domain_type = XS_UNKNOWN;
769 
770 	if (!xen_domain())
771 		return -ENODEV;
772 
773 	xenbus_ring_ops_init();
774 
775 	if (xen_pv_domain())
776 		xen_store_domain_type = XS_PV;
777 	if (xen_hvm_domain())
778 		xen_store_domain_type = XS_HVM;
779 	if (xen_hvm_domain() && xen_initial_domain())
780 		xen_store_domain_type = XS_LOCAL;
781 	if (xen_pv_domain() && !xen_start_info->store_evtchn)
782 		xen_store_domain_type = XS_LOCAL;
783 	if (xen_pv_domain() && xen_start_info->store_evtchn)
784 		xenstored_ready = 1;
785 
786 	switch (xen_store_domain_type) {
787 	case XS_LOCAL:
788 		err = xenstored_local_init();
789 		if (err)
790 			goto out_error;
791 		xen_store_interface = gfn_to_virt(xen_store_gfn);
792 		break;
793 	case XS_PV:
794 		xen_store_evtchn = xen_start_info->store_evtchn;
795 		xen_store_gfn = xen_start_info->store_mfn;
796 		xen_store_interface = gfn_to_virt(xen_store_gfn);
797 		break;
798 	case XS_HVM:
799 		err = hvm_get_parameter(HVM_PARAM_STORE_EVTCHN, &v);
800 		if (err)
801 			goto out_error;
802 		xen_store_evtchn = (int)v;
803 		err = hvm_get_parameter(HVM_PARAM_STORE_PFN, &v);
804 		if (err)
805 			goto out_error;
806 		xen_store_gfn = (unsigned long)v;
807 		xen_store_interface =
808 			xen_remap(xen_store_gfn << XEN_PAGE_SHIFT,
809 				  XEN_PAGE_SIZE);
810 		break;
811 	default:
812 		pr_warn("Xenstore state unknown\n");
813 		break;
814 	}
815 
816 	/* Initialize the interface to xenstore. */
817 	err = xs_init();
818 	if (err) {
819 		pr_warn("Error initializing xenstore comms: %i\n", err);
820 		goto out_error;
821 	}
822 
823 	if ((xen_store_domain_type != XS_LOCAL) &&
824 	    (xen_store_domain_type != XS_UNKNOWN))
825 		xen_resume_notifier_register(&xenbus_resume_nb);
826 
827 #ifdef CONFIG_XEN_COMPAT_XENFS
828 	/*
829 	 * Create xenfs mountpoint in /proc for compatibility with
830 	 * utilities that expect to find "xenbus" under "/proc/xen".
831 	 */
832 	proc_create_mount_point("xen");
833 #endif
834 
835 out_error:
836 	return err;
837 }
838 
839 postcore_initcall(xenbus_init);
840 
841 MODULE_LICENSE("GPL");
842