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> */
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 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 
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 
192 static int read_backend_details(struct xenbus_device *xendev)
193 {
194 	return xenbus_read_otherend_details(xendev, "backend-id", "backend");
195 }
196 
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 	if (ignore_nonessential) {
215 		/* With older QEMU, for PVonHVM guests the guest config files
216 		 * could contain: vfb = [ 'vnc=1, vnclisten=0.0.0.0']
217 		 * which is nonsensical as there is no PV FB (there can be
218 		 * a PVKB) running as HVM guest. */
219 
220 		if ((strncmp(xendev->nodename, "device/vkbd", 11) == 0))
221 			return 0;
222 
223 		if ((strncmp(xendev->nodename, "device/vfb", 10) == 0))
224 			return 0;
225 	}
226 	xendrv = to_xenbus_driver(dev->driver);
227 	return (xendev->state < XenbusStateConnected ||
228 		(xendev->state == XenbusStateConnected &&
229 		 xendrv->is_ready && !xendrv->is_ready(xendev)));
230 }
231 static int essential_device_connecting(struct device *dev, void *data)
232 {
233 	return is_device_connecting(dev, data, true /* ignore PV[KBB+FB] */);
234 }
235 static int non_essential_device_connecting(struct device *dev, void *data)
236 {
237 	return is_device_connecting(dev, data, false);
238 }
239 
240 static int exists_essential_connecting_device(struct device_driver *drv)
241 {
242 	return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
243 				essential_device_connecting);
244 }
245 static int exists_non_essential_connecting_device(struct device_driver *drv)
246 {
247 	return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
248 				non_essential_device_connecting);
249 }
250 
251 static int print_device_status(struct device *dev, void *data)
252 {
253 	struct xenbus_device *xendev = to_xenbus_device(dev);
254 	struct device_driver *drv = data;
255 
256 	/* Is this operation limited to a particular driver? */
257 	if (drv && (dev->driver != drv))
258 		return 0;
259 
260 	if (!dev->driver) {
261 		/* Information only: is this too noisy? */
262 		pr_info("Device with no driver: %s\n", xendev->nodename);
263 	} else if (xendev->state < XenbusStateConnected) {
264 		enum xenbus_state rstate = XenbusStateUnknown;
265 		if (xendev->otherend)
266 			rstate = xenbus_read_driver_state(xendev->otherend);
267 		pr_warn("Timeout connecting to device: %s (local state %d, remote state %d)\n",
268 			xendev->nodename, xendev->state, rstate);
269 	}
270 
271 	return 0;
272 }
273 
274 /* We only wait for device setup after most initcalls have run. */
275 static int ready_to_wait_for_devices;
276 
277 static bool wait_loop(unsigned long start, unsigned int max_delay,
278 		     unsigned int *seconds_waited)
279 {
280 	if (time_after(jiffies, start + (*seconds_waited+5)*HZ)) {
281 		if (!*seconds_waited)
282 			pr_warn("Waiting for devices to initialise: ");
283 		*seconds_waited += 5;
284 		pr_cont("%us...", max_delay - *seconds_waited);
285 		if (*seconds_waited == max_delay) {
286 			pr_cont("\n");
287 			return true;
288 		}
289 	}
290 
291 	schedule_timeout_interruptible(HZ/10);
292 
293 	return false;
294 }
295 /*
296  * On a 5-minute timeout, wait for all devices currently configured.  We need
297  * to do this to guarantee that the filesystems and / or network devices
298  * needed for boot are available, before we can allow the boot to proceed.
299  *
300  * This needs to be on a late_initcall, to happen after the frontend device
301  * drivers have been initialised, but before the root fs is mounted.
302  *
303  * A possible improvement here would be to have the tools add a per-device
304  * flag to the store entry, indicating whether it is needed at boot time.
305  * This would allow people who knew what they were doing to accelerate their
306  * boot slightly, but of course needs tools or manual intervention to set up
307  * those flags correctly.
308  */
309 static void wait_for_devices(struct xenbus_driver *xendrv)
310 {
311 	unsigned long start = jiffies;
312 	struct device_driver *drv = xendrv ? &xendrv->driver : NULL;
313 	unsigned int seconds_waited = 0;
314 
315 	if (!ready_to_wait_for_devices || !xen_domain())
316 		return;
317 
318 	while (exists_non_essential_connecting_device(drv))
319 		if (wait_loop(start, 30, &seconds_waited))
320 			break;
321 
322 	/* Skips PVKB and PVFB check.*/
323 	while (exists_essential_connecting_device(drv))
324 		if (wait_loop(start, 270, &seconds_waited))
325 			break;
326 
327 	if (seconds_waited)
328 		printk("\n");
329 
330 	bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
331 			 print_device_status);
332 }
333 
334 int __xenbus_register_frontend(struct xenbus_driver *drv, struct module *owner,
335 			       const char *mod_name)
336 {
337 	int ret;
338 
339 	drv->read_otherend_details = read_backend_details;
340 
341 	ret = xenbus_register_driver_common(drv, &xenbus_frontend,
342 					    owner, mod_name);
343 	if (ret)
344 		return ret;
345 
346 	/* If this driver is loaded as a module wait for devices to attach. */
347 	wait_for_devices(drv);
348 
349 	return 0;
350 }
351 EXPORT_SYMBOL_GPL(__xenbus_register_frontend);
352 
353 static DECLARE_WAIT_QUEUE_HEAD(backend_state_wq);
354 static int backend_state;
355 
356 static void xenbus_reset_backend_state_changed(struct xenbus_watch *w,
357 					const char *path, const char *token)
358 {
359 	if (xenbus_scanf(XBT_NIL, path, "", "%i",
360 			 &backend_state) != 1)
361 		backend_state = XenbusStateUnknown;
362 	printk(KERN_DEBUG "XENBUS: backend %s %s\n",
363 	       path, xenbus_strstate(backend_state));
364 	wake_up(&backend_state_wq);
365 }
366 
367 static void xenbus_reset_wait_for_backend(char *be, int expected)
368 {
369 	long timeout;
370 	timeout = wait_event_interruptible_timeout(backend_state_wq,
371 			backend_state == expected, 5 * HZ);
372 	if (timeout <= 0)
373 		pr_info("backend %s timed out\n", be);
374 }
375 
376 /*
377  * Reset frontend if it is in Connected or Closed state.
378  * Wait for backend to catch up.
379  * State Connected happens during kdump, Closed after kexec.
380  */
381 static void xenbus_reset_frontend(char *fe, char *be, int be_state)
382 {
383 	struct xenbus_watch be_watch;
384 
385 	printk(KERN_DEBUG "XENBUS: backend %s %s\n",
386 			be, xenbus_strstate(be_state));
387 
388 	memset(&be_watch, 0, sizeof(be_watch));
389 	be_watch.node = kasprintf(GFP_NOIO | __GFP_HIGH, "%s/state", be);
390 	if (!be_watch.node)
391 		return;
392 
393 	be_watch.callback = xenbus_reset_backend_state_changed;
394 	backend_state = XenbusStateUnknown;
395 
396 	pr_info("triggering reconnect on %s\n", be);
397 	register_xenbus_watch(&be_watch);
398 
399 	/* fall through to forward backend to state XenbusStateInitialising */
400 	switch (be_state) {
401 	case XenbusStateConnected:
402 		xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosing);
403 		xenbus_reset_wait_for_backend(be, XenbusStateClosing);
404 		fallthrough;
405 
406 	case XenbusStateClosing:
407 		xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosed);
408 		xenbus_reset_wait_for_backend(be, XenbusStateClosed);
409 		fallthrough;
410 
411 	case XenbusStateClosed:
412 		xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateInitialising);
413 		xenbus_reset_wait_for_backend(be, XenbusStateInitWait);
414 	}
415 
416 	unregister_xenbus_watch(&be_watch);
417 	pr_info("reconnect done on %s\n", be);
418 	kfree(be_watch.node);
419 }
420 
421 static void xenbus_check_frontend(char *class, char *dev)
422 {
423 	int be_state, fe_state, err;
424 	char *backend, *frontend;
425 
426 	frontend = kasprintf(GFP_NOIO | __GFP_HIGH, "device/%s/%s", class, dev);
427 	if (!frontend)
428 		return;
429 
430 	err = xenbus_scanf(XBT_NIL, frontend, "state", "%i", &fe_state);
431 	if (err != 1)
432 		goto out;
433 
434 	switch (fe_state) {
435 	case XenbusStateConnected:
436 	case XenbusStateClosed:
437 		printk(KERN_DEBUG "XENBUS: frontend %s %s\n",
438 				frontend, xenbus_strstate(fe_state));
439 		backend = xenbus_read(XBT_NIL, frontend, "backend", NULL);
440 		if (!backend || IS_ERR(backend))
441 			goto out;
442 		err = xenbus_scanf(XBT_NIL, backend, "state", "%i", &be_state);
443 		if (err == 1)
444 			xenbus_reset_frontend(frontend, backend, be_state);
445 		kfree(backend);
446 		break;
447 	default:
448 		break;
449 	}
450 out:
451 	kfree(frontend);
452 }
453 
454 static void xenbus_reset_state(void)
455 {
456 	char **devclass, **dev;
457 	int devclass_n, dev_n;
458 	int i, j;
459 
460 	devclass = xenbus_directory(XBT_NIL, "device", "", &devclass_n);
461 	if (IS_ERR(devclass))
462 		return;
463 
464 	for (i = 0; i < devclass_n; i++) {
465 		dev = xenbus_directory(XBT_NIL, "device", devclass[i], &dev_n);
466 		if (IS_ERR(dev))
467 			continue;
468 		for (j = 0; j < dev_n; j++)
469 			xenbus_check_frontend(devclass[i], dev[j]);
470 		kfree(dev);
471 	}
472 	kfree(devclass);
473 }
474 
475 static int frontend_probe_and_watch(struct notifier_block *notifier,
476 				   unsigned long event,
477 				   void *data)
478 {
479 	/* reset devices in Connected or Closed state */
480 	if (xen_hvm_domain())
481 		xenbus_reset_state();
482 	/* Enumerate devices in xenstore and watch for changes. */
483 	xenbus_probe_devices(&xenbus_frontend);
484 	register_xenbus_watch(&fe_watch);
485 
486 	return NOTIFY_DONE;
487 }
488 
489 
490 static int __init xenbus_probe_frontend_init(void)
491 {
492 	static struct notifier_block xenstore_notifier = {
493 		.notifier_call = frontend_probe_and_watch
494 	};
495 	int err;
496 
497 	DPRINTK("");
498 
499 	/* Register ourselves with the kernel bus subsystem */
500 	err = bus_register(&xenbus_frontend.bus);
501 	if (err)
502 		return err;
503 
504 	register_xenstore_notifier(&xenstore_notifier);
505 
506 	return 0;
507 }
508 subsys_initcall(xenbus_probe_frontend_init);
509 
510 #ifndef MODULE
511 static int __init boot_wait_for_devices(void)
512 {
513 	if (!xen_has_pv_devices())
514 		return -ENODEV;
515 
516 	ready_to_wait_for_devices = 1;
517 	wait_for_devices(NULL);
518 	return 0;
519 }
520 
521 late_initcall(boot_wait_for_devices);
522 #endif
523 
524 MODULE_LICENSE("GPL");
525