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