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> */
35static 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> */
53static 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
76static 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
88static 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
94static 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
101static 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
118static 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
128static 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
150static 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
158static 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
177static 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. */
187static struct xenbus_watch fe_watch = {
188	.node = "device",
189	.callback = frontend_changed,
190};
191
192static int read_backend_details(struct xenbus_device *xendev)
193{
194	return xenbus_read_otherend_details(xendev, "backend-id", "backend");
195}
196
197static 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}
231static int essential_device_connecting(struct device *dev, void *data)
232{
233	return is_device_connecting(dev, data, true /* ignore PV[KBB+FB] */);
234}
235static int non_essential_device_connecting(struct device *dev, void *data)
236{
237	return is_device_connecting(dev, data, false);
238}
239
240static 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}
245static 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
251static 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. */
275static int ready_to_wait_for_devices;
276
277static 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 */
309static 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
334int __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}
351EXPORT_SYMBOL_GPL(__xenbus_register_frontend);
352
353static DECLARE_WAIT_QUEUE_HEAD(backend_state_wq);
354static int backend_state;
355
356static 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
367static 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 */
381static 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
421static 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	}
450out:
451	kfree(frontend);
452}
453
454static 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
475static 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
490static 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}
508subsys_initcall(xenbus_probe_frontend_init);
509
510#ifndef MODULE
511static 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
521late_initcall(boot_wait_for_devices);
522#endif
523
524MODULE_LICENSE("GPL");
525