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 /* fall through */ 405 406 case XenbusStateClosing: 407 xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosed); 408 xenbus_reset_wait_for_backend(be, XenbusStateClosed); 409 /* fall through */ 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