1 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
2 
3 #define DPRINTK(fmt, ...)				\
4 	pr_debug("(%s:%d) " fmt "\n",			\
5 		 __func__, __LINE__, ##__VA_ARGS__)
6 
7 #include <linux/kernel.h>
8 #include <linux/err.h>
9 #include <linux/string.h>
10 #include <linux/ctype.h>
11 #include <linux/fcntl.h>
12 #include <linux/mm.h>
13 #include <linux/proc_fs.h>
14 #include <linux/notifier.h>
15 #include <linux/kthread.h>
16 #include <linux/mutex.h>
17 #include <linux/io.h>
18 #include <linux/module.h>
19 
20 #include <asm/page.h>
21 #include <asm/pgtable.h>
22 #include <asm/xen/hypervisor.h>
23 #include <xen/xenbus.h>
24 #include <xen/events.h>
25 #include <xen/page.h>
26 #include <xen/xen.h>
27 
28 #include <xen/platform_pci.h>
29 
30 #include "xenbus.h"
31 
32 
33 
34 /* device/<type>/<id> => <type>-<id> */
35 static int frontend_bus_id(char bus_id[XEN_BUS_ID_SIZE], const char *nodename)
36 {
37 	nodename = strchr(nodename, '/');
38 	if (!nodename || strlen(nodename + 1) >= XEN_BUS_ID_SIZE) {
39 		pr_warn("bad frontend %s\n", nodename);
40 		return -EINVAL;
41 	}
42 
43 	strlcpy(bus_id, nodename + 1, XEN_BUS_ID_SIZE);
44 	if (!strchr(bus_id, '/')) {
45 		pr_warn("bus_id %s no slash\n", bus_id);
46 		return -EINVAL;
47 	}
48 	*strchr(bus_id, '/') = '-';
49 	return 0;
50 }
51 
52 /* device/<typename>/<name> */
53 static int xenbus_probe_frontend(struct xen_bus_type *bus, const char *type,
54 				 const char *name)
55 {
56 	char *nodename;
57 	int err;
58 
59 	/* ignore console/0 */
60 	if (!strncmp(type, "console", 7) && !strncmp(name, "0", 1)) {
61 		DPRINTK("Ignoring buggy device entry console/0");
62 		return 0;
63 	}
64 
65 	nodename = kasprintf(GFP_KERNEL, "%s/%s/%s", bus->root, type, name);
66 	if (!nodename)
67 		return -ENOMEM;
68 
69 	DPRINTK("%s", nodename);
70 
71 	err = xenbus_probe_node(bus, type, nodename);
72 	kfree(nodename);
73 	return err;
74 }
75 
76 static int xenbus_uevent_frontend(struct device *_dev,
77 				  struct kobj_uevent_env *env)
78 {
79 	struct xenbus_device *dev = to_xenbus_device(_dev);
80 
81 	if (add_uevent_var(env, "MODALIAS=xen:%s", dev->devicetype))
82 		return -ENOMEM;
83 
84 	return 0;
85 }
86 
87 
88 static void backend_changed(struct xenbus_watch *watch,
89 			    const char *path, const char *token)
90 {
91 	xenbus_otherend_changed(watch, path, token, 1);
92 }
93 
94 static void xenbus_frontend_delayed_resume(struct work_struct *w)
95 {
96 	struct xenbus_device *xdev = container_of(w, struct xenbus_device, work);
97 
98 	xenbus_dev_resume(&xdev->dev);
99 }
100 
101 static int xenbus_frontend_dev_resume(struct device *dev)
102 {
103 	/*
104 	 * If xenstored is running in this domain, we cannot access the backend
105 	 * state at the moment, so we need to defer xenbus_dev_resume
106 	 */
107 	if (xen_store_domain_type == XS_LOCAL) {
108 		struct xenbus_device *xdev = to_xenbus_device(dev);
109 
110 		schedule_work(&xdev->work);
111 
112 		return 0;
113 	}
114 
115 	return xenbus_dev_resume(dev);
116 }
117 
118 static int xenbus_frontend_dev_probe(struct device *dev)
119 {
120 	if (xen_store_domain_type == XS_LOCAL) {
121 		struct xenbus_device *xdev = to_xenbus_device(dev);
122 		INIT_WORK(&xdev->work, xenbus_frontend_delayed_resume);
123 	}
124 
125 	return xenbus_dev_probe(dev);
126 }
127 
128 static const struct dev_pm_ops xenbus_pm_ops = {
129 	.suspend	= xenbus_dev_suspend,
130 	.resume		= xenbus_frontend_dev_resume,
131 	.freeze		= xenbus_dev_suspend,
132 	.thaw		= xenbus_dev_cancel,
133 	.restore	= xenbus_dev_resume,
134 };
135 
136 static struct xen_bus_type xenbus_frontend = {
137 	.root = "device",
138 	.levels = 2,		/* device/type/<id> */
139 	.get_bus_id = frontend_bus_id,
140 	.probe = xenbus_probe_frontend,
141 	.otherend_changed = backend_changed,
142 	.bus = {
143 		.name		= "xen",
144 		.match		= xenbus_match,
145 		.uevent		= xenbus_uevent_frontend,
146 		.probe		= xenbus_frontend_dev_probe,
147 		.remove		= xenbus_dev_remove,
148 		.shutdown	= xenbus_dev_shutdown,
149 		.dev_groups	= xenbus_dev_groups,
150 
151 		.pm		= &xenbus_pm_ops,
152 	},
153 };
154 
155 static void frontend_changed(struct xenbus_watch *watch,
156 			     const char *path, const char *token)
157 {
158 	DPRINTK("");
159 
160 	xenbus_dev_changed(path, &xenbus_frontend);
161 }
162 
163 
164 /* We watch for devices appearing and vanishing. */
165 static struct xenbus_watch fe_watch = {
166 	.node = "device",
167 	.callback = frontend_changed,
168 };
169 
170 static int read_backend_details(struct xenbus_device *xendev)
171 {
172 	return xenbus_read_otherend_details(xendev, "backend-id", "backend");
173 }
174 
175 static int is_device_connecting(struct device *dev, void *data, bool ignore_nonessential)
176 {
177 	struct xenbus_device *xendev = to_xenbus_device(dev);
178 	struct device_driver *drv = data;
179 	struct xenbus_driver *xendrv;
180 
181 	/*
182 	 * A device with no driver will never connect. We care only about
183 	 * devices which should currently be in the process of connecting.
184 	 */
185 	if (!dev->driver)
186 		return 0;
187 
188 	/* Is this search limited to a particular driver? */
189 	if (drv && (dev->driver != drv))
190 		return 0;
191 
192 	if (ignore_nonessential) {
193 		/* With older QEMU, for PVonHVM guests the guest config files
194 		 * could contain: vfb = [ 'vnc=1, vnclisten=0.0.0.0']
195 		 * which is nonsensical as there is no PV FB (there can be
196 		 * a PVKB) running as HVM guest. */
197 
198 		if ((strncmp(xendev->nodename, "device/vkbd", 11) == 0))
199 			return 0;
200 
201 		if ((strncmp(xendev->nodename, "device/vfb", 10) == 0))
202 			return 0;
203 	}
204 	xendrv = to_xenbus_driver(dev->driver);
205 	return (xendev->state < XenbusStateConnected ||
206 		(xendev->state == XenbusStateConnected &&
207 		 xendrv->is_ready && !xendrv->is_ready(xendev)));
208 }
209 static int essential_device_connecting(struct device *dev, void *data)
210 {
211 	return is_device_connecting(dev, data, true /* ignore PV[KBB+FB] */);
212 }
213 static int non_essential_device_connecting(struct device *dev, void *data)
214 {
215 	return is_device_connecting(dev, data, false);
216 }
217 
218 static int exists_essential_connecting_device(struct device_driver *drv)
219 {
220 	return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
221 				essential_device_connecting);
222 }
223 static int exists_non_essential_connecting_device(struct device_driver *drv)
224 {
225 	return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
226 				non_essential_device_connecting);
227 }
228 
229 static int print_device_status(struct device *dev, void *data)
230 {
231 	struct xenbus_device *xendev = to_xenbus_device(dev);
232 	struct device_driver *drv = data;
233 
234 	/* Is this operation limited to a particular driver? */
235 	if (drv && (dev->driver != drv))
236 		return 0;
237 
238 	if (!dev->driver) {
239 		/* Information only: is this too noisy? */
240 		pr_info("Device with no driver: %s\n", xendev->nodename);
241 	} else if (xendev->state < XenbusStateConnected) {
242 		enum xenbus_state rstate = XenbusStateUnknown;
243 		if (xendev->otherend)
244 			rstate = xenbus_read_driver_state(xendev->otherend);
245 		pr_warn("Timeout connecting to device: %s (local state %d, remote state %d)\n",
246 			xendev->nodename, xendev->state, rstate);
247 	}
248 
249 	return 0;
250 }
251 
252 /* We only wait for device setup after most initcalls have run. */
253 static int ready_to_wait_for_devices;
254 
255 static bool wait_loop(unsigned long start, unsigned int max_delay,
256 		     unsigned int *seconds_waited)
257 {
258 	if (time_after(jiffies, start + (*seconds_waited+5)*HZ)) {
259 		if (!*seconds_waited)
260 			pr_warn("Waiting for devices to initialise: ");
261 		*seconds_waited += 5;
262 		pr_cont("%us...", max_delay - *seconds_waited);
263 		if (*seconds_waited == max_delay) {
264 			pr_cont("\n");
265 			return true;
266 		}
267 	}
268 
269 	schedule_timeout_interruptible(HZ/10);
270 
271 	return false;
272 }
273 /*
274  * On a 5-minute timeout, wait for all devices currently configured.  We need
275  * to do this to guarantee that the filesystems and / or network devices
276  * needed for boot are available, before we can allow the boot to proceed.
277  *
278  * This needs to be on a late_initcall, to happen after the frontend device
279  * drivers have been initialised, but before the root fs is mounted.
280  *
281  * A possible improvement here would be to have the tools add a per-device
282  * flag to the store entry, indicating whether it is needed at boot time.
283  * This would allow people who knew what they were doing to accelerate their
284  * boot slightly, but of course needs tools or manual intervention to set up
285  * those flags correctly.
286  */
287 static void wait_for_devices(struct xenbus_driver *xendrv)
288 {
289 	unsigned long start = jiffies;
290 	struct device_driver *drv = xendrv ? &xendrv->driver : NULL;
291 	unsigned int seconds_waited = 0;
292 
293 	if (!ready_to_wait_for_devices || !xen_domain())
294 		return;
295 
296 	while (exists_non_essential_connecting_device(drv))
297 		if (wait_loop(start, 30, &seconds_waited))
298 			break;
299 
300 	/* Skips PVKB and PVFB check.*/
301 	while (exists_essential_connecting_device(drv))
302 		if (wait_loop(start, 270, &seconds_waited))
303 			break;
304 
305 	if (seconds_waited)
306 		printk("\n");
307 
308 	bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
309 			 print_device_status);
310 }
311 
312 int __xenbus_register_frontend(struct xenbus_driver *drv, struct module *owner,
313 			       const char *mod_name)
314 {
315 	int ret;
316 
317 	drv->read_otherend_details = read_backend_details;
318 
319 	ret = xenbus_register_driver_common(drv, &xenbus_frontend,
320 					    owner, mod_name);
321 	if (ret)
322 		return ret;
323 
324 	/* If this driver is loaded as a module wait for devices to attach. */
325 	wait_for_devices(drv);
326 
327 	return 0;
328 }
329 EXPORT_SYMBOL_GPL(__xenbus_register_frontend);
330 
331 static DECLARE_WAIT_QUEUE_HEAD(backend_state_wq);
332 static int backend_state;
333 
334 static void xenbus_reset_backend_state_changed(struct xenbus_watch *w,
335 					const char *path, const char *token)
336 {
337 	if (xenbus_scanf(XBT_NIL, path, "", "%i",
338 			 &backend_state) != 1)
339 		backend_state = XenbusStateUnknown;
340 	printk(KERN_DEBUG "XENBUS: backend %s %s\n",
341 	       path, xenbus_strstate(backend_state));
342 	wake_up(&backend_state_wq);
343 }
344 
345 static void xenbus_reset_wait_for_backend(char *be, int expected)
346 {
347 	long timeout;
348 	timeout = wait_event_interruptible_timeout(backend_state_wq,
349 			backend_state == expected, 5 * HZ);
350 	if (timeout <= 0)
351 		pr_info("backend %s timed out\n", be);
352 }
353 
354 /*
355  * Reset frontend if it is in Connected or Closed state.
356  * Wait for backend to catch up.
357  * State Connected happens during kdump, Closed after kexec.
358  */
359 static void xenbus_reset_frontend(char *fe, char *be, int be_state)
360 {
361 	struct xenbus_watch be_watch;
362 
363 	printk(KERN_DEBUG "XENBUS: backend %s %s\n",
364 			be, xenbus_strstate(be_state));
365 
366 	memset(&be_watch, 0, sizeof(be_watch));
367 	be_watch.node = kasprintf(GFP_NOIO | __GFP_HIGH, "%s/state", be);
368 	if (!be_watch.node)
369 		return;
370 
371 	be_watch.callback = xenbus_reset_backend_state_changed;
372 	backend_state = XenbusStateUnknown;
373 
374 	pr_info("triggering reconnect on %s\n", be);
375 	register_xenbus_watch(&be_watch);
376 
377 	/* fall through to forward backend to state XenbusStateInitialising */
378 	switch (be_state) {
379 	case XenbusStateConnected:
380 		xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosing);
381 		xenbus_reset_wait_for_backend(be, XenbusStateClosing);
382 		/* fall through */
383 
384 	case XenbusStateClosing:
385 		xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosed);
386 		xenbus_reset_wait_for_backend(be, XenbusStateClosed);
387 		/* fall through */
388 
389 	case XenbusStateClosed:
390 		xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateInitialising);
391 		xenbus_reset_wait_for_backend(be, XenbusStateInitWait);
392 	}
393 
394 	unregister_xenbus_watch(&be_watch);
395 	pr_info("reconnect done on %s\n", be);
396 	kfree(be_watch.node);
397 }
398 
399 static void xenbus_check_frontend(char *class, char *dev)
400 {
401 	int be_state, fe_state, err;
402 	char *backend, *frontend;
403 
404 	frontend = kasprintf(GFP_NOIO | __GFP_HIGH, "device/%s/%s", class, dev);
405 	if (!frontend)
406 		return;
407 
408 	err = xenbus_scanf(XBT_NIL, frontend, "state", "%i", &fe_state);
409 	if (err != 1)
410 		goto out;
411 
412 	switch (fe_state) {
413 	case XenbusStateConnected:
414 	case XenbusStateClosed:
415 		printk(KERN_DEBUG "XENBUS: frontend %s %s\n",
416 				frontend, xenbus_strstate(fe_state));
417 		backend = xenbus_read(XBT_NIL, frontend, "backend", NULL);
418 		if (!backend || IS_ERR(backend))
419 			goto out;
420 		err = xenbus_scanf(XBT_NIL, backend, "state", "%i", &be_state);
421 		if (err == 1)
422 			xenbus_reset_frontend(frontend, backend, be_state);
423 		kfree(backend);
424 		break;
425 	default:
426 		break;
427 	}
428 out:
429 	kfree(frontend);
430 }
431 
432 static void xenbus_reset_state(void)
433 {
434 	char **devclass, **dev;
435 	int devclass_n, dev_n;
436 	int i, j;
437 
438 	devclass = xenbus_directory(XBT_NIL, "device", "", &devclass_n);
439 	if (IS_ERR(devclass))
440 		return;
441 
442 	for (i = 0; i < devclass_n; i++) {
443 		dev = xenbus_directory(XBT_NIL, "device", devclass[i], &dev_n);
444 		if (IS_ERR(dev))
445 			continue;
446 		for (j = 0; j < dev_n; j++)
447 			xenbus_check_frontend(devclass[i], dev[j]);
448 		kfree(dev);
449 	}
450 	kfree(devclass);
451 }
452 
453 static int frontend_probe_and_watch(struct notifier_block *notifier,
454 				   unsigned long event,
455 				   void *data)
456 {
457 	/* reset devices in Connected or Closed state */
458 	if (xen_hvm_domain())
459 		xenbus_reset_state();
460 	/* Enumerate devices in xenstore and watch for changes. */
461 	xenbus_probe_devices(&xenbus_frontend);
462 	register_xenbus_watch(&fe_watch);
463 
464 	return NOTIFY_DONE;
465 }
466 
467 
468 static int __init xenbus_probe_frontend_init(void)
469 {
470 	static struct notifier_block xenstore_notifier = {
471 		.notifier_call = frontend_probe_and_watch
472 	};
473 	int err;
474 
475 	DPRINTK("");
476 
477 	/* Register ourselves with the kernel bus subsystem */
478 	err = bus_register(&xenbus_frontend.bus);
479 	if (err)
480 		return err;
481 
482 	register_xenstore_notifier(&xenstore_notifier);
483 
484 	return 0;
485 }
486 subsys_initcall(xenbus_probe_frontend_init);
487 
488 #ifndef MODULE
489 static int __init boot_wait_for_devices(void)
490 {
491 	if (!xen_has_pv_devices())
492 		return -ENODEV;
493 
494 	ready_to_wait_for_devices = 1;
495 	wait_for_devices(NULL);
496 	return 0;
497 }
498 
499 late_initcall(boot_wait_for_devices);
500 #endif
501 
502 MODULE_LICENSE("GPL");
503