xref: /linux/drivers/xen/xenbus/xenbus_probe_frontend.c (revision a1c613ae4c322ddd58d5a8539dbfba2a0380a8c0)
1 // SPDX-License-Identifier: GPL-2.0-only
2 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
3 
4 #define DPRINTK(fmt, ...)				\
5 	pr_debug("(%s:%d) " fmt "\n",			\
6 		 __func__, __LINE__, ##__VA_ARGS__)
7 
8 #include <linux/kernel.h>
9 #include <linux/err.h>
10 #include <linux/string.h>
11 #include <linux/ctype.h>
12 #include <linux/fcntl.h>
13 #include <linux/mm.h>
14 #include <linux/proc_fs.h>
15 #include <linux/notifier.h>
16 #include <linux/kthread.h>
17 #include <linux/mutex.h>
18 #include <linux/io.h>
19 #include <linux/module.h>
20 
21 #include <asm/page.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> */
frontend_bus_id(char bus_id[XEN_BUS_ID_SIZE],const char * nodename)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 	strscpy(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> */
xenbus_probe_frontend(struct xen_bus_type * bus,const char * type,const char * 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 
xenbus_uevent_frontend(const struct device * _dev,struct kobj_uevent_env * env)76 static int xenbus_uevent_frontend(const struct device *_dev,
77 				  struct kobj_uevent_env *env)
78 {
79 	const 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 
backend_changed(struct xenbus_watch * watch,const char * path,const char * token)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 
xenbus_frontend_delayed_resume(struct work_struct * w)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 
xenbus_frontend_dev_resume(struct device * dev)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 
xenbus_frontend_dev_probe(struct device * dev)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 
xenbus_frontend_dev_shutdown(struct device * _dev)128 static void xenbus_frontend_dev_shutdown(struct device *_dev)
129 {
130 	struct xenbus_device *dev = to_xenbus_device(_dev);
131 	unsigned long timeout = 5*HZ;
132 
133 	DPRINTK("%s", dev->nodename);
134 
135 	get_device(&dev->dev);
136 	if (dev->state != XenbusStateConnected) {
137 		pr_info("%s: %s: %s != Connected, skipping\n",
138 			__func__, dev->nodename, xenbus_strstate(dev->state));
139 		goto out;
140 	}
141 	xenbus_switch_state(dev, XenbusStateClosing);
142 	timeout = wait_for_completion_timeout(&dev->down, timeout);
143 	if (!timeout)
144 		pr_info("%s: %s timeout closing device\n",
145 			__func__, dev->nodename);
146  out:
147 	put_device(&dev->dev);
148 }
149 
150 static const struct dev_pm_ops xenbus_pm_ops = {
151 	.suspend	= xenbus_dev_suspend,
152 	.resume		= xenbus_frontend_dev_resume,
153 	.freeze		= xenbus_dev_suspend,
154 	.thaw		= xenbus_dev_cancel,
155 	.restore	= xenbus_dev_resume,
156 };
157 
158 static struct xen_bus_type xenbus_frontend = {
159 	.root = "device",
160 	.levels = 2,		/* device/type/<id> */
161 	.get_bus_id = frontend_bus_id,
162 	.probe = xenbus_probe_frontend,
163 	.otherend_changed = backend_changed,
164 	.bus = {
165 		.name		= "xen",
166 		.match		= xenbus_match,
167 		.uevent		= xenbus_uevent_frontend,
168 		.probe		= xenbus_frontend_dev_probe,
169 		.remove		= xenbus_dev_remove,
170 		.shutdown	= xenbus_frontend_dev_shutdown,
171 		.dev_groups	= xenbus_dev_groups,
172 
173 		.pm		= &xenbus_pm_ops,
174 	},
175 };
176 
frontend_changed(struct xenbus_watch * watch,const char * path,const char * token)177 static void frontend_changed(struct xenbus_watch *watch,
178 			     const char *path, const char *token)
179 {
180 	DPRINTK("");
181 
182 	xenbus_dev_changed(path, &xenbus_frontend);
183 }
184 
185 
186 /* We watch for devices appearing and vanishing. */
187 static struct xenbus_watch fe_watch = {
188 	.node = "device",
189 	.callback = frontend_changed,
190 };
191 
read_backend_details(struct xenbus_device * xendev)192 static int read_backend_details(struct xenbus_device *xendev)
193 {
194 	return xenbus_read_otherend_details(xendev, "backend-id", "backend");
195 }
196 
is_device_connecting(struct device * dev,void * data,bool ignore_nonessential)197 static int is_device_connecting(struct device *dev, void *data, bool ignore_nonessential)
198 {
199 	struct xenbus_device *xendev = to_xenbus_device(dev);
200 	struct device_driver *drv = data;
201 	struct xenbus_driver *xendrv;
202 
203 	/*
204 	 * A device with no driver will never connect. We care only about
205 	 * devices which should currently be in the process of connecting.
206 	 */
207 	if (!dev->driver)
208 		return 0;
209 
210 	/* Is this search limited to a particular driver? */
211 	if (drv && (dev->driver != drv))
212 		return 0;
213 
214 	xendrv = to_xenbus_driver(dev->driver);
215 
216 	if (ignore_nonessential && xendrv->not_essential)
217 		return 0;
218 
219 	return (xendev->state < XenbusStateConnected ||
220 		(xendev->state == XenbusStateConnected &&
221 		 xendrv->is_ready && !xendrv->is_ready(xendev)));
222 }
essential_device_connecting(struct device * dev,void * data)223 static int essential_device_connecting(struct device *dev, void *data)
224 {
225 	return is_device_connecting(dev, data, true /* ignore PV[KBB+FB] */);
226 }
non_essential_device_connecting(struct device * dev,void * data)227 static int non_essential_device_connecting(struct device *dev, void *data)
228 {
229 	return is_device_connecting(dev, data, false);
230 }
231 
exists_essential_connecting_device(struct device_driver * drv)232 static int exists_essential_connecting_device(struct device_driver *drv)
233 {
234 	return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
235 				essential_device_connecting);
236 }
exists_non_essential_connecting_device(struct device_driver * drv)237 static int exists_non_essential_connecting_device(struct device_driver *drv)
238 {
239 	return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
240 				non_essential_device_connecting);
241 }
242 
print_device_status(struct device * dev,void * data)243 static int print_device_status(struct device *dev, void *data)
244 {
245 	struct xenbus_device *xendev = to_xenbus_device(dev);
246 	struct device_driver *drv = data;
247 
248 	/* Is this operation limited to a particular driver? */
249 	if (drv && (dev->driver != drv))
250 		return 0;
251 
252 	if (!dev->driver) {
253 		/* Information only: is this too noisy? */
254 		pr_info("Device with no driver: %s\n", xendev->nodename);
255 	} else if (xendev->state < XenbusStateConnected) {
256 		enum xenbus_state rstate = XenbusStateUnknown;
257 		if (xendev->otherend)
258 			rstate = xenbus_read_driver_state(xendev->otherend);
259 		pr_warn("Timeout connecting to device: %s (local state %d, remote state %d)\n",
260 			xendev->nodename, xendev->state, rstate);
261 	}
262 
263 	return 0;
264 }
265 
266 /* We only wait for device setup after most initcalls have run. */
267 static int ready_to_wait_for_devices;
268 
wait_loop(unsigned long start,unsigned int max_delay,unsigned int * seconds_waited)269 static bool wait_loop(unsigned long start, unsigned int max_delay,
270 		     unsigned int *seconds_waited)
271 {
272 	if (time_after(jiffies, start + (*seconds_waited+5)*HZ)) {
273 		if (!*seconds_waited)
274 			pr_warn("Waiting for devices to initialise: ");
275 		*seconds_waited += 5;
276 		pr_cont("%us...", max_delay - *seconds_waited);
277 		if (*seconds_waited == max_delay) {
278 			pr_cont("\n");
279 			return true;
280 		}
281 	}
282 
283 	schedule_timeout_interruptible(HZ/10);
284 
285 	return false;
286 }
287 /*
288  * On a 5-minute timeout, wait for all devices currently configured.  We need
289  * to do this to guarantee that the filesystems and / or network devices
290  * needed for boot are available, before we can allow the boot to proceed.
291  *
292  * This needs to be on a late_initcall, to happen after the frontend device
293  * drivers have been initialised, but before the root fs is mounted.
294  *
295  * A possible improvement here would be to have the tools add a per-device
296  * flag to the store entry, indicating whether it is needed at boot time.
297  * This would allow people who knew what they were doing to accelerate their
298  * boot slightly, but of course needs tools or manual intervention to set up
299  * those flags correctly.
300  */
wait_for_devices(struct xenbus_driver * xendrv)301 static void wait_for_devices(struct xenbus_driver *xendrv)
302 {
303 	unsigned long start = jiffies;
304 	struct device_driver *drv = xendrv ? &xendrv->driver : NULL;
305 	unsigned int seconds_waited = 0;
306 
307 	if (!ready_to_wait_for_devices || !xen_domain())
308 		return;
309 
310 	while (exists_non_essential_connecting_device(drv))
311 		if (wait_loop(start, 30, &seconds_waited))
312 			break;
313 
314 	/* Skips PVKB and PVFB check.*/
315 	while (exists_essential_connecting_device(drv))
316 		if (wait_loop(start, 270, &seconds_waited))
317 			break;
318 
319 	if (seconds_waited)
320 		printk("\n");
321 
322 	bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
323 			 print_device_status);
324 }
325 
__xenbus_register_frontend(struct xenbus_driver * drv,struct module * owner,const char * mod_name)326 int __xenbus_register_frontend(struct xenbus_driver *drv, struct module *owner,
327 			       const char *mod_name)
328 {
329 	int ret;
330 
331 	drv->read_otherend_details = read_backend_details;
332 
333 	ret = xenbus_register_driver_common(drv, &xenbus_frontend,
334 					    owner, mod_name);
335 	if (ret)
336 		return ret;
337 
338 	/* If this driver is loaded as a module wait for devices to attach. */
339 	wait_for_devices(drv);
340 
341 	return 0;
342 }
343 EXPORT_SYMBOL_GPL(__xenbus_register_frontend);
344 
345 static DECLARE_WAIT_QUEUE_HEAD(backend_state_wq);
346 static int backend_state;
347 
xenbus_reset_backend_state_changed(struct xenbus_watch * w,const char * path,const char * token)348 static void xenbus_reset_backend_state_changed(struct xenbus_watch *w,
349 					const char *path, const char *token)
350 {
351 	if (xenbus_scanf(XBT_NIL, path, "", "%i",
352 			 &backend_state) != 1)
353 		backend_state = XenbusStateUnknown;
354 	printk(KERN_DEBUG "XENBUS: backend %s %s\n",
355 	       path, xenbus_strstate(backend_state));
356 	wake_up(&backend_state_wq);
357 }
358 
xenbus_reset_wait_for_backend(char * be,int expected)359 static void xenbus_reset_wait_for_backend(char *be, int expected)
360 {
361 	long timeout;
362 	timeout = wait_event_interruptible_timeout(backend_state_wq,
363 			backend_state == expected, 5 * HZ);
364 	if (timeout <= 0)
365 		pr_info("backend %s timed out\n", be);
366 }
367 
368 /*
369  * Reset frontend if it is in Connected or Closed state.
370  * Wait for backend to catch up.
371  * State Connected happens during kdump, Closed after kexec.
372  */
xenbus_reset_frontend(char * fe,char * be,int be_state)373 static void xenbus_reset_frontend(char *fe, char *be, int be_state)
374 {
375 	struct xenbus_watch be_watch;
376 
377 	printk(KERN_DEBUG "XENBUS: backend %s %s\n",
378 			be, xenbus_strstate(be_state));
379 
380 	memset(&be_watch, 0, sizeof(be_watch));
381 	be_watch.node = kasprintf(GFP_NOIO | __GFP_HIGH, "%s/state", be);
382 	if (!be_watch.node)
383 		return;
384 
385 	be_watch.callback = xenbus_reset_backend_state_changed;
386 	backend_state = XenbusStateUnknown;
387 
388 	pr_info("triggering reconnect on %s\n", be);
389 	register_xenbus_watch(&be_watch);
390 
391 	/* fall through to forward backend to state XenbusStateInitialising */
392 	switch (be_state) {
393 	case XenbusStateConnected:
394 		xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosing);
395 		xenbus_reset_wait_for_backend(be, XenbusStateClosing);
396 		fallthrough;
397 
398 	case XenbusStateClosing:
399 		xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosed);
400 		xenbus_reset_wait_for_backend(be, XenbusStateClosed);
401 		fallthrough;
402 
403 	case XenbusStateClosed:
404 		xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateInitialising);
405 		xenbus_reset_wait_for_backend(be, XenbusStateInitWait);
406 	}
407 
408 	unregister_xenbus_watch(&be_watch);
409 	pr_info("reconnect done on %s\n", be);
410 	kfree(be_watch.node);
411 }
412 
xenbus_check_frontend(char * class,char * dev)413 static void xenbus_check_frontend(char *class, char *dev)
414 {
415 	int be_state, fe_state, err;
416 	char *backend, *frontend;
417 
418 	frontend = kasprintf(GFP_NOIO | __GFP_HIGH, "device/%s/%s", class, dev);
419 	if (!frontend)
420 		return;
421 
422 	err = xenbus_scanf(XBT_NIL, frontend, "state", "%i", &fe_state);
423 	if (err != 1)
424 		goto out;
425 
426 	switch (fe_state) {
427 	case XenbusStateConnected:
428 	case XenbusStateClosed:
429 		printk(KERN_DEBUG "XENBUS: frontend %s %s\n",
430 				frontend, xenbus_strstate(fe_state));
431 		backend = xenbus_read(XBT_NIL, frontend, "backend", NULL);
432 		if (IS_ERR_OR_NULL(backend))
433 			goto out;
434 		err = xenbus_scanf(XBT_NIL, backend, "state", "%i", &be_state);
435 		if (err == 1)
436 			xenbus_reset_frontend(frontend, backend, be_state);
437 		kfree(backend);
438 		break;
439 	default:
440 		break;
441 	}
442 out:
443 	kfree(frontend);
444 }
445 
xenbus_reset_state(void)446 static void xenbus_reset_state(void)
447 {
448 	char **devclass, **dev;
449 	int devclass_n, dev_n;
450 	int i, j;
451 
452 	devclass = xenbus_directory(XBT_NIL, "device", "", &devclass_n);
453 	if (IS_ERR(devclass))
454 		return;
455 
456 	for (i = 0; i < devclass_n; i++) {
457 		dev = xenbus_directory(XBT_NIL, "device", devclass[i], &dev_n);
458 		if (IS_ERR(dev))
459 			continue;
460 		for (j = 0; j < dev_n; j++)
461 			xenbus_check_frontend(devclass[i], dev[j]);
462 		kfree(dev);
463 	}
464 	kfree(devclass);
465 }
466 
frontend_probe_and_watch(struct notifier_block * notifier,unsigned long event,void * data)467 static int frontend_probe_and_watch(struct notifier_block *notifier,
468 				   unsigned long event,
469 				   void *data)
470 {
471 	/* reset devices in Connected or Closed state */
472 	if (xen_hvm_domain())
473 		xenbus_reset_state();
474 	/* Enumerate devices in xenstore and watch for changes. */
475 	xenbus_probe_devices(&xenbus_frontend);
476 	register_xenbus_watch(&fe_watch);
477 
478 	return NOTIFY_DONE;
479 }
480 
481 
xenbus_probe_frontend_init(void)482 static int __init xenbus_probe_frontend_init(void)
483 {
484 	static struct notifier_block xenstore_notifier = {
485 		.notifier_call = frontend_probe_and_watch
486 	};
487 	int err;
488 
489 	DPRINTK("");
490 
491 	/* Register ourselves with the kernel bus subsystem */
492 	err = bus_register(&xenbus_frontend.bus);
493 	if (err)
494 		return err;
495 
496 	register_xenstore_notifier(&xenstore_notifier);
497 
498 	return 0;
499 }
500 subsys_initcall(xenbus_probe_frontend_init);
501 
502 #ifndef MODULE
boot_wait_for_devices(void)503 static int __init boot_wait_for_devices(void)
504 {
505 	if (!xen_has_pv_devices())
506 		return -ENODEV;
507 
508 	ready_to_wait_for_devices = 1;
509 	wait_for_devices(NULL);
510 	return 0;
511 }
512 
513 late_initcall(boot_wait_for_devices);
514 #endif
515 
516 MODULE_LICENSE("GPL");
517