summaryrefslogtreecommitdiff
path: root/drivers/xen/xenbus/xenbus_probe_frontend.c
blob: a31b54d488398675fc01eaa2878f0a21ec49fe46 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
#define DPRINTK(fmt, args...)				\
	pr_debug("xenbus_probe (%s:%d) " fmt ".\n",	\
		 __func__, __LINE__, ##args)

#include <linux/kernel.h>
#include <linux/err.h>
#include <linux/string.h>
#include <linux/ctype.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/proc_fs.h>
#include <linux/notifier.h>
#include <linux/kthread.h>
#include <linux/mutex.h>
#include <linux/io.h>
#include <linux/module.h>

#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/xen/hypervisor.h>
#include <xen/xenbus.h>
#include <xen/events.h>
#include <xen/page.h>

#include <xen/platform_pci.h>

#include "xenbus_comms.h"
#include "xenbus_probe.h"


/* device/<type>/<id> => <type>-<id> */
static int frontend_bus_id(char bus_id[XEN_BUS_ID_SIZE], const char *nodename)
{
	nodename = strchr(nodename, '/');
	if (!nodename || strlen(nodename + 1) >= XEN_BUS_ID_SIZE) {
		printk(KERN_WARNING "XENBUS: bad frontend %s\n", nodename);
		return -EINVAL;
	}

	strlcpy(bus_id, nodename + 1, XEN_BUS_ID_SIZE);
	if (!strchr(bus_id, '/')) {
		printk(KERN_WARNING "XENBUS: bus_id %s no slash\n", bus_id);
		return -EINVAL;
	}
	*strchr(bus_id, '/') = '-';
	return 0;
}

/* device/<typename>/<name> */
static int xenbus_probe_frontend(struct xen_bus_type *bus, const char *type,
				 const char *name)
{
	char *nodename;
	int err;

	/* ignore console/0 */
	if (!strncmp(type, "console", 7) && !strncmp(name, "0", 1)) {
		DPRINTK("Ignoring buggy device entry console/0");
		return 0;
	}

	nodename = kasprintf(GFP_KERNEL, "%s/%s/%s", bus->root, type, name);
	if (!nodename)
		return -ENOMEM;

	DPRINTK("%s", nodename);

	err = xenbus_probe_node(bus, type, nodename);
	kfree(nodename);
	return err;
}

static int xenbus_uevent_frontend(struct device *_dev,
				  struct kobj_uevent_env *env)
{
	struct xenbus_device *dev = to_xenbus_device(_dev);

	if (add_uevent_var(env, "MODALIAS=xen:%s", dev->devicetype))
		return -ENOMEM;

	return 0;
}


static void backend_changed(struct xenbus_watch *watch,
			    const char **vec, unsigned int len)
{
	xenbus_otherend_changed(watch, vec, len, 1);
}

static const struct dev_pm_ops xenbus_pm_ops = {
	.suspend	= xenbus_dev_suspend,
	.resume		= xenbus_dev_resume,
	.freeze		= xenbus_dev_suspend,
	.thaw		= xenbus_dev_cancel,
	.restore	= xenbus_dev_resume,
};

static struct xen_bus_type xenbus_frontend = {
	.root = "device",
	.levels = 2,		/* device/type/<id> */
	.get_bus_id = frontend_bus_id,
	.probe = xenbus_probe_frontend,
	.otherend_changed = backend_changed,
	.bus = {
		.name		= "xen",
		.match		= xenbus_match,
		.uevent		= xenbus_uevent_frontend,
		.probe		= xenbus_dev_probe,
		.remove		= xenbus_dev_remove,
		.shutdown	= xenbus_dev_shutdown,
		.dev_attrs	= xenbus_dev_attrs,

		.pm		= &xenbus_pm_ops,
	},
};

static void frontend_changed(struct xenbus_watch *watch,
			     const char **vec, unsigned int len)
{
	DPRINTK("");

	xenbus_dev_changed(vec[XS_WATCH_PATH], &xenbus_frontend);
}


/* We watch for devices appearing and vanishing. */
static struct xenbus_watch fe_watch = {
	.node = "device",
	.callback = frontend_changed,
};

static int read_backend_details(struct xenbus_device *xendev)
{
	return xenbus_read_otherend_details(xendev, "backend-id", "backend");
}

static int is_device_connecting(struct device *dev, void *data, bool ignore_nonessential)
{
	struct xenbus_device *xendev = to_xenbus_device(dev);
	struct device_driver *drv = data;
	struct xenbus_driver *xendrv;

	/*
	 * A device with no driver will never connect. We care only about
	 * devices which should currently be in the process of connecting.
	 */
	if (!dev->driver)
		return 0;

	/* Is this search limited to a particular driver? */
	if (drv && (dev->driver != drv))
		return 0;

	if (ignore_nonessential) {
		/* With older QEMU, for PVonHVM guests the guest config files
		 * could contain: vfb = [ 'vnc=1, vnclisten=0.0.0.0']
		 * which is nonsensical as there is no PV FB (there can be
		 * a PVKB) running as HVM guest. */

		if ((strncmp(xendev->nodename, "device/vkbd", 11) == 0))
			return 0;

		if ((strncmp(xendev->nodename, "device/vfb", 10) == 0))
			return 0;
	}
	xendrv = to_xenbus_driver(dev->driver);
	return (xendev->state < XenbusStateConnected ||
		(xendev->state == XenbusStateConnected &&
		 xendrv->is_ready && !xendrv->is_ready(xendev)));
}
static int essential_device_connecting(struct device *dev, void *data)
{
	return is_device_connecting(dev, data, true /* ignore PV[KBB+FB] */);
}
static int non_essential_device_connecting(struct device *dev, void *data)
{
	return is_device_connecting(dev, data, false);
}

static int exists_essential_connecting_device(struct device_driver *drv)
{
	return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
				essential_device_connecting);
}
static int exists_non_essential_connecting_device(struct device_driver *drv)
{
	return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
				non_essential_device_connecting);
}

static int print_device_status(struct device *dev, void *data)
{
	struct xenbus_device *xendev = to_xenbus_device(dev);
	struct device_driver *drv = data;

	/* Is this operation limited to a particular driver? */
	if (drv && (dev->driver != drv))
		return 0;

	if (!dev->driver) {
		/* Information only: is this too noisy? */
		printk(KERN_INFO "XENBUS: Device with no driver: %s\n",
		       xendev->nodename);
	} else if (xendev->state < XenbusStateConnected) {
		enum xenbus_state rstate = XenbusStateUnknown;
		if (xendev->otherend)
			rstate = xenbus_read_driver_state(xendev->otherend);
		printk(KERN_WARNING "XENBUS: Timeout connecting "
		       "to device: %s (local state %d, remote state %d)\n",
		       xendev->nodename, xendev->state, rstate);
	}

	return 0;
}

/* We only wait for device setup after most initcalls have run. */
static int ready_to_wait_for_devices;

static bool wait_loop(unsigned long start, unsigned int max_delay,
		     unsigned int *seconds_waited)
{
	if (time_after(jiffies, start + (*seconds_waited+5)*HZ)) {
		if (!*seconds_waited)
			printk(KERN_WARNING "XENBUS: Waiting for "
			       "devices to initialise: ");
		*seconds_waited += 5;
		printk("%us...", max_delay - *seconds_waited);
		if (*seconds_waited == max_delay)
			return true;
	}

	schedule_timeout_interruptible(HZ/10);

	return false;
}
/*
 * On a 5-minute timeout, wait for all devices currently configured.  We need
 * to do this to guarantee that the filesystems and / or network devices
 * needed for boot are available, before we can allow the boot to proceed.
 *
 * This needs to be on a late_initcall, to happen after the frontend device
 * drivers have been initialised, but before the root fs is mounted.
 *
 * A possible improvement here would be to have the tools add a per-device
 * flag to the store entry, indicating whether it is needed at boot time.
 * This would allow people who knew what they were doing to accelerate their
 * boot slightly, but of course needs tools or manual intervention to set up
 * those flags correctly.
 */
static void wait_for_devices(struct xenbus_driver *xendrv)
{
	unsigned long start = jiffies;
	struct device_driver *drv = xendrv ? &xendrv->driver : NULL;
	unsigned int seconds_waited = 0;

	if (!ready_to_wait_for_devices || !xen_domain())
		return;

	while (exists_non_essential_connecting_device(drv))
		if (wait_loop(start, 30, &seconds_waited))
			break;

	/* Skips PVKB and PVFB check.*/
	while (exists_essential_connecting_device(drv))
		if (wait_loop(start, 270, &seconds_waited))
			break;

	if (seconds_waited)
		printk("\n");

	bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
			 print_device_status);
}

int xenbus_register_frontend(struct xenbus_driver *drv)
{
	int ret;

	drv->read_otherend_details = read_backend_details;

	ret = xenbus_register_driver_common(drv, &xenbus_frontend);
	if (ret)
		return ret;

	/* If this driver is loaded as a module wait for devices to attach. */
	wait_for_devices(drv);

	return 0;
}
EXPORT_SYMBOL_GPL(xenbus_register_frontend);

static DECLARE_WAIT_QUEUE_HEAD(backend_state_wq);
static int backend_state;

static void xenbus_reset_backend_state_changed(struct xenbus_watch *w,
					const char **v, unsigned int l)
{
	xenbus_scanf(XBT_NIL, v[XS_WATCH_PATH], "", "%i", &backend_state);
	printk(KERN_DEBUG "XENBUS: backend %s %s\n",
			v[XS_WATCH_PATH], xenbus_strstate(backend_state));
	wake_up(&backend_state_wq);
}

static void xenbus_reset_wait_for_backend(char *be, int expected)
{
	long timeout;
	timeout = wait_event_interruptible_timeout(backend_state_wq,
			backend_state == expected, 5 * HZ);
	if (timeout <= 0)
		printk(KERN_INFO "XENBUS: backend %s timed out.\n", be);
}

/*
 * Reset frontend if it is in Connected or Closed state.
 * Wait for backend to catch up.
 * State Connected happens during kdump, Closed after kexec.
 */
static void xenbus_reset_frontend(char *fe, char *be, int be_state)
{
	struct xenbus_watch be_watch;

	printk(KERN_DEBUG "XENBUS: backend %s %s\n",
			be, xenbus_strstate(be_state));

	memset(&be_watch, 0, sizeof(be_watch));
	be_watch.node = kasprintf(GFP_NOIO | __GFP_HIGH, "%s/state", be);
	if (!be_watch.node)
		return;

	be_watch.callback = xenbus_reset_backend_state_changed;
	backend_state = XenbusStateUnknown;

	printk(KERN_INFO "XENBUS: triggering reconnect on %s\n", be);
	register_xenbus_watch(&be_watch);

	/* fall through to forward backend to state XenbusStateInitialising */
	switch (be_state) {
	case XenbusStateConnected:
		xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosing);
		xenbus_reset_wait_for_backend(be, XenbusStateClosing);

	case XenbusStateClosing:
		xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosed);
		xenbus_reset_wait_for_backend(be, XenbusStateClosed);

	case XenbusStateClosed:
		xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateInitialising);
		xenbus_reset_wait_for_backend(be, XenbusStateInitWait);
	}

	unregister_xenbus_watch(&be_watch);
	printk(KERN_INFO "XENBUS: reconnect done on %s\n", be);
	kfree(be_watch.node);
}

static void xenbus_check_frontend(char *class, char *dev)
{
	int be_state, fe_state, err;
	char *backend, *frontend;

	frontend = kasprintf(GFP_NOIO | __GFP_HIGH, "device/%s/%s", class, dev);
	if (!frontend)
		return;

	err = xenbus_scanf(XBT_NIL, frontend, "state", "%i", &fe_state);
	if (err != 1)
		goto out;

	switch (fe_state) {
	case XenbusStateConnected:
	case XenbusStateClosed:
		printk(KERN_DEBUG "XENBUS: frontend %s %s\n",
				frontend, xenbus_strstate(fe_state));
		backend = xenbus_read(XBT_NIL, frontend, "backend", NULL);
		if (!backend || IS_ERR(backend))
			goto out;
		err = xenbus_scanf(XBT_NIL, backend, "state", "%i", &be_state);
		if (err == 1)
			xenbus_reset_frontend(frontend, backend, be_state);
		kfree(backend);
		break;
	default:
		break;
	}
out:
	kfree(frontend);
}

static void xenbus_reset_state(void)
{
	char **devclass, **dev;
	int devclass_n, dev_n;
	int i, j;

	devclass = xenbus_directory(XBT_NIL, "device", "", &devclass_n);
	if (IS_ERR(devclass))
		return;

	for (i = 0; i < devclass_n; i++) {
		dev = xenbus_directory(XBT_NIL, "device", devclass[i], &dev_n);
		if (IS_ERR(dev))
			continue;
		for (j = 0; j < dev_n; j++)
			xenbus_check_frontend(devclass[i], dev[j]);
		kfree(dev);
	}
	kfree(devclass);
}

static int frontend_probe_and_watch(struct notifier_block *notifier,
				   unsigned long event,
				   void *data)
{
	/* reset devices in Connected or Closed state */
	if (xen_hvm_domain())
		xenbus_reset_state();
	/* Enumerate devices in xenstore and watch for changes. */
	xenbus_probe_devices(&xenbus_frontend);
	register_xenbus_watch(&fe_watch);

	return NOTIFY_DONE;
}


static int __init xenbus_probe_frontend_init(void)
{
	static struct notifier_block xenstore_notifier = {
		.notifier_call = frontend_probe_and_watch
	};
	int err;

	DPRINTK("");

	/* Register ourselves with the kernel bus subsystem */
	err = bus_register(&xenbus_frontend.bus);
	if (err)
		return err;

	register_xenstore_notifier(&xenstore_notifier);

	return 0;
}
subsys_initcall(xenbus_probe_frontend_init);

#ifndef MODULE
static int __init boot_wait_for_devices(void)
{
	if (xen_hvm_domain() && !xen_platform_pci_unplug)
		return -ENODEV;

	ready_to_wait_for_devices = 1;
	wait_for_devices(NULL);
	return 0;
}

late_initcall(boot_wait_for_devices);
#endif

MODULE_LICENSE("GPL");