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