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