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 	err = drv->probe(dev, id);
236 	if (err)
237 		goto fail;
238 
239 	err = watch_otherend(dev);
240 	if (err) {
241 		dev_warn(&dev->dev, "watch_otherend on %s failed.\n",
242 		       dev->nodename);
243 		return err;
244 	}
245 
246 	return 0;
247 fail:
248 	xenbus_dev_error(dev, err, "xenbus_dev_probe on %s", dev->nodename);
249 	xenbus_switch_state(dev, XenbusStateClosed);
250 	return err;
251 }
252 EXPORT_SYMBOL_GPL(xenbus_dev_probe);
253 
254 int xenbus_dev_remove(struct device *_dev)
255 {
256 	struct xenbus_device *dev = to_xenbus_device(_dev);
257 	struct xenbus_driver *drv = to_xenbus_driver(_dev->driver);
258 
259 	DPRINTK("%s", dev->nodename);
260 
261 	free_otherend_watch(dev);
262 
263 	if (drv->remove)
264 		drv->remove(dev);
265 
266 	free_otherend_details(dev);
267 
268 	xenbus_switch_state(dev, XenbusStateClosed);
269 	return 0;
270 }
271 EXPORT_SYMBOL_GPL(xenbus_dev_remove);
272 
273 void xenbus_dev_shutdown(struct device *_dev)
274 {
275 	struct xenbus_device *dev = to_xenbus_device(_dev);
276 	unsigned long timeout = 5*HZ;
277 
278 	DPRINTK("%s", dev->nodename);
279 
280 	get_device(&dev->dev);
281 	if (dev->state != XenbusStateConnected) {
282 		pr_info("%s: %s: %s != Connected, skipping\n",
283 			__func__, dev->nodename, xenbus_strstate(dev->state));
284 		goto out;
285 	}
286 	xenbus_switch_state(dev, XenbusStateClosing);
287 	timeout = wait_for_completion_timeout(&dev->down, timeout);
288 	if (!timeout)
289 		pr_info("%s: %s timeout closing device\n",
290 			__func__, dev->nodename);
291  out:
292 	put_device(&dev->dev);
293 }
294 EXPORT_SYMBOL_GPL(xenbus_dev_shutdown);
295 
296 int xenbus_register_driver_common(struct xenbus_driver *drv,
297 				  struct xen_bus_type *bus,
298 				  struct module *owner, const char *mod_name)
299 {
300 	drv->driver.name = drv->name ? drv->name : drv->ids[0].devicetype;
301 	drv->driver.bus = &bus->bus;
302 	drv->driver.owner = owner;
303 	drv->driver.mod_name = mod_name;
304 
305 	return driver_register(&drv->driver);
306 }
307 EXPORT_SYMBOL_GPL(xenbus_register_driver_common);
308 
309 void xenbus_unregister_driver(struct xenbus_driver *drv)
310 {
311 	driver_unregister(&drv->driver);
312 }
313 EXPORT_SYMBOL_GPL(xenbus_unregister_driver);
314 
315 struct xb_find_info {
316 	struct xenbus_device *dev;
317 	const char *nodename;
318 };
319 
320 static int cmp_dev(struct device *dev, void *data)
321 {
322 	struct xenbus_device *xendev = to_xenbus_device(dev);
323 	struct xb_find_info *info = data;
324 
325 	if (!strcmp(xendev->nodename, info->nodename)) {
326 		info->dev = xendev;
327 		get_device(dev);
328 		return 1;
329 	}
330 	return 0;
331 }
332 
333 static struct xenbus_device *xenbus_device_find(const char *nodename,
334 						struct bus_type *bus)
335 {
336 	struct xb_find_info info = { .dev = NULL, .nodename = nodename };
337 
338 	bus_for_each_dev(bus, NULL, &info, cmp_dev);
339 	return info.dev;
340 }
341 
342 static int cleanup_dev(struct device *dev, void *data)
343 {
344 	struct xenbus_device *xendev = to_xenbus_device(dev);
345 	struct xb_find_info *info = data;
346 	int len = strlen(info->nodename);
347 
348 	DPRINTK("%s", info->nodename);
349 
350 	/* Match the info->nodename path, or any subdirectory of that path. */
351 	if (strncmp(xendev->nodename, info->nodename, len))
352 		return 0;
353 
354 	/* If the node name is longer, ensure it really is a subdirectory. */
355 	if ((strlen(xendev->nodename) > len) && (xendev->nodename[len] != '/'))
356 		return 0;
357 
358 	info->dev = xendev;
359 	get_device(dev);
360 	return 1;
361 }
362 
363 static void xenbus_cleanup_devices(const char *path, struct bus_type *bus)
364 {
365 	struct xb_find_info info = { .nodename = path };
366 
367 	do {
368 		info.dev = NULL;
369 		bus_for_each_dev(bus, NULL, &info, cleanup_dev);
370 		if (info.dev) {
371 			device_unregister(&info.dev->dev);
372 			put_device(&info.dev->dev);
373 		}
374 	} while (info.dev);
375 }
376 
377 static void xenbus_dev_release(struct device *dev)
378 {
379 	if (dev)
380 		kfree(to_xenbus_device(dev));
381 }
382 
383 static ssize_t nodename_show(struct device *dev,
384 			     struct device_attribute *attr, char *buf)
385 {
386 	return sprintf(buf, "%s\n", to_xenbus_device(dev)->nodename);
387 }
388 static DEVICE_ATTR_RO(nodename);
389 
390 static ssize_t devtype_show(struct device *dev,
391 			    struct device_attribute *attr, char *buf)
392 {
393 	return sprintf(buf, "%s\n", to_xenbus_device(dev)->devicetype);
394 }
395 static DEVICE_ATTR_RO(devtype);
396 
397 static ssize_t modalias_show(struct device *dev,
398 			     struct device_attribute *attr, char *buf)
399 {
400 	return sprintf(buf, "%s:%s\n", dev->bus->name,
401 		       to_xenbus_device(dev)->devicetype);
402 }
403 static DEVICE_ATTR_RO(modalias);
404 
405 static ssize_t state_show(struct device *dev,
406 			    struct device_attribute *attr, char *buf)
407 {
408 	return sprintf(buf, "%s\n",
409 			xenbus_strstate(to_xenbus_device(dev)->state));
410 }
411 static DEVICE_ATTR_RO(state);
412 
413 static struct attribute *xenbus_dev_attrs[] = {
414 	&dev_attr_nodename.attr,
415 	&dev_attr_devtype.attr,
416 	&dev_attr_modalias.attr,
417 	&dev_attr_state.attr,
418 	NULL,
419 };
420 
421 static const struct attribute_group xenbus_dev_group = {
422 	.attrs = xenbus_dev_attrs,
423 };
424 
425 const struct attribute_group *xenbus_dev_groups[] = {
426 	&xenbus_dev_group,
427 	NULL,
428 };
429 EXPORT_SYMBOL_GPL(xenbus_dev_groups);
430 
431 int xenbus_probe_node(struct xen_bus_type *bus,
432 		      const char *type,
433 		      const char *nodename)
434 {
435 	char devname[XEN_BUS_ID_SIZE];
436 	int err;
437 	struct xenbus_device *xendev;
438 	size_t stringlen;
439 	char *tmpstring;
440 
441 	enum xenbus_state state = xenbus_read_driver_state(nodename);
442 
443 	if (state != XenbusStateInitialising) {
444 		/* Device is not new, so ignore it.  This can happen if a
445 		   device is going away after switching to Closed.  */
446 		return 0;
447 	}
448 
449 	stringlen = strlen(nodename) + 1 + strlen(type) + 1;
450 	xendev = kzalloc(sizeof(*xendev) + stringlen, GFP_KERNEL);
451 	if (!xendev)
452 		return -ENOMEM;
453 
454 	xendev->state = XenbusStateInitialising;
455 
456 	/* Copy the strings into the extra space. */
457 
458 	tmpstring = (char *)(xendev + 1);
459 	strcpy(tmpstring, nodename);
460 	xendev->nodename = tmpstring;
461 
462 	tmpstring += strlen(tmpstring) + 1;
463 	strcpy(tmpstring, type);
464 	xendev->devicetype = tmpstring;
465 	init_completion(&xendev->down);
466 
467 	xendev->dev.bus = &bus->bus;
468 	xendev->dev.release = xenbus_dev_release;
469 
470 	err = bus->get_bus_id(devname, xendev->nodename);
471 	if (err)
472 		goto fail;
473 
474 	dev_set_name(&xendev->dev, "%s", devname);
475 
476 	/* Register with generic device framework. */
477 	err = device_register(&xendev->dev);
478 	if (err) {
479 		put_device(&xendev->dev);
480 		xendev = NULL;
481 		goto fail;
482 	}
483 
484 	return 0;
485 fail:
486 	kfree(xendev);
487 	return err;
488 }
489 EXPORT_SYMBOL_GPL(xenbus_probe_node);
490 
491 static int xenbus_probe_device_type(struct xen_bus_type *bus, const char *type)
492 {
493 	int err = 0;
494 	char **dir;
495 	unsigned int dir_n = 0;
496 	int i;
497 
498 	dir = xenbus_directory(XBT_NIL, bus->root, type, &dir_n);
499 	if (IS_ERR(dir))
500 		return PTR_ERR(dir);
501 
502 	for (i = 0; i < dir_n; i++) {
503 		err = bus->probe(bus, type, dir[i]);
504 		if (err)
505 			break;
506 	}
507 
508 	kfree(dir);
509 	return err;
510 }
511 
512 int xenbus_probe_devices(struct xen_bus_type *bus)
513 {
514 	int err = 0;
515 	char **dir;
516 	unsigned int i, dir_n;
517 
518 	dir = xenbus_directory(XBT_NIL, bus->root, "", &dir_n);
519 	if (IS_ERR(dir))
520 		return PTR_ERR(dir);
521 
522 	for (i = 0; i < dir_n; i++) {
523 		err = xenbus_probe_device_type(bus, dir[i]);
524 		if (err)
525 			break;
526 	}
527 
528 	kfree(dir);
529 	return err;
530 }
531 EXPORT_SYMBOL_GPL(xenbus_probe_devices);
532 
533 static unsigned int char_count(const char *str, char c)
534 {
535 	unsigned int i, ret = 0;
536 
537 	for (i = 0; str[i]; i++)
538 		if (str[i] == c)
539 			ret++;
540 	return ret;
541 }
542 
543 static int strsep_len(const char *str, char c, unsigned int len)
544 {
545 	unsigned int i;
546 
547 	for (i = 0; str[i]; i++)
548 		if (str[i] == c) {
549 			if (len == 0)
550 				return i;
551 			len--;
552 		}
553 	return (len == 0) ? i : -ERANGE;
554 }
555 
556 void xenbus_dev_changed(const char *node, struct xen_bus_type *bus)
557 {
558 	int exists, rootlen;
559 	struct xenbus_device *dev;
560 	char type[XEN_BUS_ID_SIZE];
561 	const char *p, *root;
562 
563 	if (char_count(node, '/') < 2)
564 		return;
565 
566 	exists = xenbus_exists(XBT_NIL, node, "");
567 	if (!exists) {
568 		xenbus_cleanup_devices(node, &bus->bus);
569 		return;
570 	}
571 
572 	/* backend/<type>/... or device/<type>/... */
573 	p = strchr(node, '/') + 1;
574 	snprintf(type, XEN_BUS_ID_SIZE, "%.*s", (int)strcspn(p, "/"), p);
575 	type[XEN_BUS_ID_SIZE-1] = '\0';
576 
577 	rootlen = strsep_len(node, '/', bus->levels);
578 	if (rootlen < 0)
579 		return;
580 	root = kasprintf(GFP_KERNEL, "%.*s", rootlen, node);
581 	if (!root)
582 		return;
583 
584 	dev = xenbus_device_find(root, &bus->bus);
585 	if (!dev)
586 		xenbus_probe_node(bus, type, root);
587 	else
588 		put_device(&dev->dev);
589 
590 	kfree(root);
591 }
592 EXPORT_SYMBOL_GPL(xenbus_dev_changed);
593 
594 int xenbus_dev_suspend(struct device *dev)
595 {
596 	int err = 0;
597 	struct xenbus_driver *drv;
598 	struct xenbus_device *xdev
599 		= container_of(dev, struct xenbus_device, dev);
600 
601 	DPRINTK("%s", xdev->nodename);
602 
603 	if (dev->driver == NULL)
604 		return 0;
605 	drv = to_xenbus_driver(dev->driver);
606 	if (drv->suspend)
607 		err = drv->suspend(xdev);
608 	if (err)
609 		pr_warn("suspend %s failed: %i\n", dev_name(dev), err);
610 	return 0;
611 }
612 EXPORT_SYMBOL_GPL(xenbus_dev_suspend);
613 
614 int xenbus_dev_resume(struct device *dev)
615 {
616 	int err;
617 	struct xenbus_driver *drv;
618 	struct xenbus_device *xdev
619 		= container_of(dev, struct xenbus_device, dev);
620 
621 	DPRINTK("%s", xdev->nodename);
622 
623 	if (dev->driver == NULL)
624 		return 0;
625 	drv = to_xenbus_driver(dev->driver);
626 	err = talk_to_otherend(xdev);
627 	if (err) {
628 		pr_warn("resume (talk_to_otherend) %s failed: %i\n",
629 			dev_name(dev), err);
630 		return err;
631 	}
632 
633 	xdev->state = XenbusStateInitialising;
634 
635 	if (drv->resume) {
636 		err = drv->resume(xdev);
637 		if (err) {
638 			pr_warn("resume %s failed: %i\n", dev_name(dev), err);
639 			return err;
640 		}
641 	}
642 
643 	err = watch_otherend(xdev);
644 	if (err) {
645 		pr_warn("resume (watch_otherend) %s failed: %d.\n",
646 			dev_name(dev), err);
647 		return err;
648 	}
649 
650 	return 0;
651 }
652 EXPORT_SYMBOL_GPL(xenbus_dev_resume);
653 
654 int xenbus_dev_cancel(struct device *dev)
655 {
656 	/* Do nothing */
657 	DPRINTK("cancel");
658 	return 0;
659 }
660 EXPORT_SYMBOL_GPL(xenbus_dev_cancel);
661 
662 /* A flag to determine if xenstored is 'ready' (i.e. has started) */
663 int xenstored_ready;
664 
665 
666 int register_xenstore_notifier(struct notifier_block *nb)
667 {
668 	int ret = 0;
669 
670 	if (xenstored_ready > 0)
671 		ret = nb->notifier_call(nb, 0, NULL);
672 	else
673 		blocking_notifier_chain_register(&xenstore_chain, nb);
674 
675 	return ret;
676 }
677 EXPORT_SYMBOL_GPL(register_xenstore_notifier);
678 
679 void unregister_xenstore_notifier(struct notifier_block *nb)
680 {
681 	blocking_notifier_chain_unregister(&xenstore_chain, nb);
682 }
683 EXPORT_SYMBOL_GPL(unregister_xenstore_notifier);
684 
685 void xenbus_probe(struct work_struct *unused)
686 {
687 	xenstored_ready = 1;
688 
689 	/* Notify others that xenstore is up */
690 	blocking_notifier_call_chain(&xenstore_chain, 0, NULL);
691 }
692 EXPORT_SYMBOL_GPL(xenbus_probe);
693 
694 static int __init xenbus_probe_initcall(void)
695 {
696 	if (!xen_domain())
697 		return -ENODEV;
698 
699 	if (xen_initial_domain() || xen_hvm_domain())
700 		return 0;
701 
702 	xenbus_probe(NULL);
703 	return 0;
704 }
705 
706 device_initcall(xenbus_probe_initcall);
707 
708 /* Set up event channel for xenstored which is run as a local process
709  * (this is normally used only in dom0)
710  */
711 static int __init xenstored_local_init(void)
712 {
713 	int err = -ENOMEM;
714 	unsigned long page = 0;
715 	struct evtchn_alloc_unbound alloc_unbound;
716 
717 	/* Allocate Xenstore page */
718 	page = get_zeroed_page(GFP_KERNEL);
719 	if (!page)
720 		goto out_err;
721 
722 	xen_store_gfn = virt_to_gfn((void *)page);
723 
724 	/* Next allocate a local port which xenstored can bind to */
725 	alloc_unbound.dom        = DOMID_SELF;
726 	alloc_unbound.remote_dom = DOMID_SELF;
727 
728 	err = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound,
729 					  &alloc_unbound);
730 	if (err == -ENOSYS)
731 		goto out_err;
732 
733 	BUG_ON(err);
734 	xen_store_evtchn = alloc_unbound.port;
735 
736 	return 0;
737 
738  out_err:
739 	if (page != 0)
740 		free_page(page);
741 	return err;
742 }
743 
744 static int xenbus_resume_cb(struct notifier_block *nb,
745 			    unsigned long action, void *data)
746 {
747 	int err = 0;
748 
749 	if (xen_hvm_domain()) {
750 		uint64_t v = 0;
751 
752 		err = hvm_get_parameter(HVM_PARAM_STORE_EVTCHN, &v);
753 		if (!err && v)
754 			xen_store_evtchn = v;
755 		else
756 			pr_warn("Cannot update xenstore event channel: %d\n",
757 				err);
758 	} else
759 		xen_store_evtchn = xen_start_info->store_evtchn;
760 
761 	return err;
762 }
763 
764 static struct notifier_block xenbus_resume_nb = {
765 	.notifier_call = xenbus_resume_cb,
766 };
767 
768 static int __init xenbus_init(void)
769 {
770 	int err = 0;
771 	uint64_t v = 0;
772 	xen_store_domain_type = XS_UNKNOWN;
773 
774 	if (!xen_domain())
775 		return -ENODEV;
776 
777 	xenbus_ring_ops_init();
778 
779 	if (xen_pv_domain())
780 		xen_store_domain_type = XS_PV;
781 	if (xen_hvm_domain())
782 		xen_store_domain_type = XS_HVM;
783 	if (xen_hvm_domain() && xen_initial_domain())
784 		xen_store_domain_type = XS_LOCAL;
785 	if (xen_pv_domain() && !xen_start_info->store_evtchn)
786 		xen_store_domain_type = XS_LOCAL;
787 	if (xen_pv_domain() && xen_start_info->store_evtchn)
788 		xenstored_ready = 1;
789 
790 	switch (xen_store_domain_type) {
791 	case XS_LOCAL:
792 		err = xenstored_local_init();
793 		if (err)
794 			goto out_error;
795 		xen_store_interface = gfn_to_virt(xen_store_gfn);
796 		break;
797 	case XS_PV:
798 		xen_store_evtchn = xen_start_info->store_evtchn;
799 		xen_store_gfn = xen_start_info->store_mfn;
800 		xen_store_interface = gfn_to_virt(xen_store_gfn);
801 		break;
802 	case XS_HVM:
803 		err = hvm_get_parameter(HVM_PARAM_STORE_EVTCHN, &v);
804 		if (err)
805 			goto out_error;
806 		xen_store_evtchn = (int)v;
807 		err = hvm_get_parameter(HVM_PARAM_STORE_PFN, &v);
808 		if (err)
809 			goto out_error;
810 		xen_store_gfn = (unsigned long)v;
811 		xen_store_interface =
812 			xen_remap(xen_store_gfn << XEN_PAGE_SHIFT,
813 				  XEN_PAGE_SIZE);
814 		break;
815 	default:
816 		pr_warn("Xenstore state unknown\n");
817 		break;
818 	}
819 
820 	/* Initialize the interface to xenstore. */
821 	err = xs_init();
822 	if (err) {
823 		pr_warn("Error initializing xenstore comms: %i\n", err);
824 		goto out_error;
825 	}
826 
827 	if ((xen_store_domain_type != XS_LOCAL) &&
828 	    (xen_store_domain_type != XS_UNKNOWN))
829 		xen_resume_notifier_register(&xenbus_resume_nb);
830 
831 #ifdef CONFIG_XEN_COMPAT_XENFS
832 	/*
833 	 * Create xenfs mountpoint in /proc for compatibility with
834 	 * utilities that expect to find "xenbus" under "/proc/xen".
835 	 */
836 	proc_create_mount_point("xen");
837 #endif
838 
839 out_error:
840 	return err;
841 }
842 
843 postcore_initcall(xenbus_init);
844 
845 MODULE_LICENSE("GPL");
846