drivers/xen/xenbus/xenbus_probe_frontend.c

   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/pgtable.h>
  23 #include <asm/xen/hypervisor.h>
  24 #include <xen/xenbus.h>
  25 #include <xen/events.h>
  26 #include <xen/page.h>
  27 #include <xen/xen.h>
  28
  29 #include <xen/platform_pci.h>
  30
  31 #include "xenbus.h"
  32
  33
  34
  35 /* device/<type>/<id> => <type>-<id> */
  36 static int frontend_bus_id(char bus_id[XEN_BUS_ID_SIZE], const char *nodename)
  37 {
  38         nodename = strchr(nodename, '/');
  39         if (!nodename || strlen(nodename + 1) >= XEN_BUS_ID_SIZE) {
  40                 pr_warn("bad frontend %s\n", nodename);
  41                 return -EINVAL;
  42         }
  43
  44         strlcpy(bus_id, nodename + 1, XEN_BUS_ID_SIZE);
  45         if (!strchr(bus_id, '/')) {
  46                 pr_warn("bus_id %s no slash\n", bus_id);
  47                 return -EINVAL;
  48         }
  49         *strchr(bus_id, '/') = '-';
  50         return 0;
  51 }
  52
  53 /* device/<typename>/<name> */
  54 static int xenbus_probe_frontend(struct xen_bus_type *bus, const char *type,
  55                                  const char *name)
  56 {
  57         char *nodename;
  58         int err;
  59
  60         /* ignore console/0 */
  61         if (!strncmp(type, "console", 7) && !strncmp(name, "0", 1)) {
  62                 DPRINTK("Ignoring buggy device entry console/0");
  63                 return 0;
  64         }
  65
  66         nodename = kasprintf(GFP_KERNEL, "%s/%s/%s", bus->root, type, name);
  67         if (!nodename)
  68                 return -ENOMEM;
  69
  70         DPRINTK("%s", nodename);
  71
  72         err = xenbus_probe_node(bus, type, nodename);
  73         kfree(nodename);
  74         return err;
  75 }
  76
  77 static int xenbus_uevent_frontend(struct device *_dev,
  78                                   struct kobj_uevent_env *env)
  79 {
  80         struct xenbus_device *dev = to_xenbus_device(_dev);
  81
  82         if (add_uevent_var(env, "MODALIAS=xen:%s", dev->devicetype))
  83                 return -ENOMEM;
  84
  85         return 0;
  86 }
  87
  88
  89 static void backend_changed(struct xenbus_watch *watch,
  90                             const char *path, const char *token)
  91 {
  92         xenbus_otherend_changed(watch, path, token, 1);
  93 }
  94
  95 static void xenbus_frontend_delayed_resume(struct work_struct *w)
  96 {
  97         struct xenbus_device *xdev = container_of(w, struct xenbus_device, work);
  98
  99         xenbus_dev_resume(&xdev->dev);
 100 }
 101
 102 static int xenbus_frontend_dev_resume(struct device *dev)
 103 {
 104         /*
 105          * If xenstored is running in this domain, we cannot access the backend
 106          * state at the moment, so we need to defer xenbus_dev_resume
 107          */
 108         if (xen_store_domain_type == XS_LOCAL) {
 109                 struct xenbus_device *xdev = to_xenbus_device(dev);
 110
 111                 schedule_work(&xdev->work);
 112
 113                 return 0;
 114         }
 115
 116         return xenbus_dev_resume(dev);
 117 }
 118
 119 static int xenbus_frontend_dev_probe(struct device *dev)
 120 {
 121         if (xen_store_domain_type == XS_LOCAL) {
 122                 struct xenbus_device *xdev = to_xenbus_device(dev);
 123                 INIT_WORK(&xdev->work, xenbus_frontend_delayed_resume);
 124         }
 125
 126         return xenbus_dev_probe(dev);
 127 }
 128
 129 static void xenbus_frontend_dev_shutdown(struct device *_dev)
 130 {
 131         struct xenbus_device *dev = to_xenbus_device(_dev);
 132         unsigned long timeout = 5*HZ;
 133
 134         DPRINTK("%s", dev->nodename);
 135
 136         get_device(&dev->dev);
 137         if (dev->state != XenbusStateConnected) {
 138                 pr_info("%s: %s: %s != Connected, skipping\n",
 139                         __func__, dev->nodename, xenbus_strstate(dev->state));
 140                 goto out;
 141         }
 142         xenbus_switch_state(dev, XenbusStateClosing);
 143         timeout = wait_for_completion_timeout(&dev->down, timeout);
 144         if (!timeout)
 145                 pr_info("%s: %s timeout closing device\n",
 146                         __func__, dev->nodename);
 147  out:
 148         put_device(&dev->dev);
 149 }
 150
 151 static const struct dev_pm_ops xenbus_pm_ops = {
 152         .suspend        = xenbus_dev_suspend,
 153         .resume         = xenbus_frontend_dev_resume,
 154         .freeze         = xenbus_dev_suspend,
 155         .thaw           = xenbus_dev_cancel,
 156         .restore        = xenbus_dev_resume,
 157 };
 158
 159 static struct xen_bus_type xenbus_frontend = {
 160         .root = "device",
 161         .levels = 2,            /* device/type/<id> */
 162         .get_bus_id = frontend_bus_id,
 163         .probe = xenbus_probe_frontend,
 164         .otherend_changed = backend_changed,
 165         .bus = {
 166                 .name           = "xen",
 167                 .match          = xenbus_match,
 168                 .uevent         = xenbus_uevent_frontend,
 169                 .probe          = xenbus_frontend_dev_probe,
 170                 .remove         = xenbus_dev_remove,
 171                 .shutdown       = xenbus_frontend_dev_shutdown,
 172                 .dev_groups     = xenbus_dev_groups,
 173
 174                 .pm             = &xenbus_pm_ops,
 175         },
 176 };
 177
 178 static void frontend_changed(struct xenbus_watch *watch,
 179                              const char *path, const char *token)
 180 {
 181         DPRINTK("");
 182
 183         xenbus_dev_changed(path, &xenbus_frontend);
 184 }
 185
 186
 187 /* We watch for devices appearing and vanishing. */
 188 static struct xenbus_watch fe_watch = {
 189         .node = "device",
 190         .callback = frontend_changed,
 191 };
 192
 193 static int read_backend_details(struct xenbus_device *xendev)
 194 {
 195         return xenbus_read_otherend_details(xendev, "backend-id", "backend");
 196 }
 197
 198 static int is_device_connecting(struct device *dev, void *data, bool ignore_nonessential)
 199 {
 200         struct xenbus_device *xendev = to_xenbus_device(dev);
 201         struct device_driver *drv = data;
 202         struct xenbus_driver *xendrv;
 203
 204         /*
 205          * A device with no driver will never connect. We care only about
 206          * devices which should currently be in the process of connecting.
 207          */
 208         if (!dev->driver)
 209                 return 0;
 210
 211         /* Is this search limited to a particular driver? */
 212         if (drv && (dev->driver != drv))
 213                 return 0;
 214
 215         if (ignore_nonessential) {
 216                 /* With older QEMU, for PVonHVM guests the guest config files
 217                  * could contain: vfb = [ 'vnc=1, vnclisten=0.0.0.0']
 218                  * which is nonsensical as there is no PV FB (there can be
 219                  * a PVKB) running as HVM guest. */
 220
 221                 if ((strncmp(xendev->nodename, "device/vkbd", 11) == 0))
 222                         return 0;
 223
 224                 if ((strncmp(xendev->nodename, "device/vfb", 10) == 0))
 225                         return 0;
 226         }
 227         xendrv = to_xenbus_driver(dev->driver);
 228         return (xendev->state < XenbusStateConnected ||
 229                 (xendev->state == XenbusStateConnected &&
 230                  xendrv->is_ready && !xendrv->is_ready(xendev)));
 231 }
 232 static int essential_device_connecting(struct device *dev, void *data)
 233 {
 234         return is_device_connecting(dev, data, true /* ignore PV[KBB+FB] */);
 235 }
 236 static int non_essential_device_connecting(struct device *dev, void *data)
 237 {
 238         return is_device_connecting(dev, data, false);
 239 }
 240
 241 static int exists_essential_connecting_device(struct device_driver *drv)
 242 {
 243         return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
 244                                 essential_device_connecting);
 245 }
 246 static int exists_non_essential_connecting_device(struct device_driver *drv)
 247 {
 248         return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
 249                                 non_essential_device_connecting);
 250 }
 251
 252 static int print_device_status(struct device *dev, void *data)
 253 {
 254         struct xenbus_device *xendev = to_xenbus_device(dev);
 255         struct device_driver *drv = data;
 256
 257         /* Is this operation limited to a particular driver? */
 258         if (drv && (dev->driver != drv))
 259                 return 0;
 260
 261         if (!dev->driver) {
 262                 /* Information only: is this too noisy? */
 263                 pr_info("Device with no driver: %s\n", xendev->nodename);
 264         } else if (xendev->state < XenbusStateConnected) {
 265                 enum xenbus_state rstate = XenbusStateUnknown;
 266                 if (xendev->otherend)
 267                         rstate = xenbus_read_driver_state(xendev->otherend);
 268                 pr_warn("Timeout connecting to device: %s (local state %d, remote state %d)\n",
 269                         xendev->nodename, xendev->state, rstate);
 270         }
 271
 272         return 0;
 273 }
 274
 275 /* We only wait for device setup after most initcalls have run. */
 276 static int ready_to_wait_for_devices;
 277
 278 static bool wait_loop(unsigned long start, unsigned int max_delay,
 279                      unsigned int *seconds_waited)
 280 {
 281         if (time_after(jiffies, start + (*seconds_waited+5)*HZ)) {
 282                 if (!*seconds_waited)
 283                         pr_warn("Waiting for devices to initialise: ");
 284                 *seconds_waited += 5;
 285                 pr_cont("%us...", max_delay - *seconds_waited);
 286                 if (*seconds_waited == max_delay) {
 287                         pr_cont("\n");
 288                         return true;
 289                 }
 290         }
 291
 292         schedule_timeout_interruptible(HZ/10);
 293
 294         return false;
 295 }
 296 /*
 297  * On a 5-minute timeout, wait for all devices currently configured.  We need
 298  * to do this to guarantee that the filesystems and / or network devices
 299  * needed for boot are available, before we can allow the boot to proceed.
 300  *
 301  * This needs to be on a late_initcall, to happen after the frontend device
 302  * drivers have been initialised, but before the root fs is mounted.
 303  *
 304  * A possible improvement here would be to have the tools add a per-device
 305  * flag to the store entry, indicating whether it is needed at boot time.
 306  * This would allow people who knew what they were doing to accelerate their
 307  * boot slightly, but of course needs tools or manual intervention to set up
 308  * those flags correctly.
 309  */
 310 static void wait_for_devices(struct xenbus_driver *xendrv)
 311 {
 312         unsigned long start = jiffies;
 313         struct device_driver *drv = xendrv ? &xendrv->driver : NULL;
 314         unsigned int seconds_waited = 0;
 315
 316         if (!ready_to_wait_for_devices || !xen_domain())
 317                 return;
 318
 319         while (exists_non_essential_connecting_device(drv))
 320                 if (wait_loop(start, 30, &seconds_waited))
 321                         break;
 322
 323         /* Skips PVKB and PVFB check.*/
 324         while (exists_essential_connecting_device(drv))
 325                 if (wait_loop(start, 270, &seconds_waited))
 326                         break;
 327
 328         if (seconds_waited)
 329                 printk("\n");
 330
 331         bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
 332                          print_device_status);
 333 }
 334
 335 int __xenbus_register_frontend(struct xenbus_driver *drv, struct module *owner,
 336                                const char *mod_name)
 337 {
 338         int ret;
 339
 340         drv->read_otherend_details = read_backend_details;
 341
 342         ret = xenbus_register_driver_common(drv, &xenbus_frontend,
 343                                             owner, mod_name);
 344         if (ret)
 345                 return ret;
 346
 347         /* If this driver is loaded as a module wait for devices to attach. */
 348         wait_for_devices(drv);
 349
 350         return 0;
 351 }
 352 EXPORT_SYMBOL_GPL(__xenbus_register_frontend);
 353
 354 static DECLARE_WAIT_QUEUE_HEAD(backend_state_wq);
 355 static int backend_state;
 356
 357 static void xenbus_reset_backend_state_changed(struct xenbus_watch *w,
 358                                         const char *path, const char *token)
 359 {
 360         if (xenbus_scanf(XBT_NIL, path, "", "%i",
 361                          &backend_state) != 1)
 362                 backend_state = XenbusStateUnknown;
 363         printk(KERN_DEBUG "XENBUS: backend %s %s\n",
 364                path, xenbus_strstate(backend_state));
 365         wake_up(&backend_state_wq);
 366 }
 367
 368 static void xenbus_reset_wait_for_backend(char *be, int expected)
 369 {
 370         long timeout;
 371         timeout = wait_event_interruptible_timeout(backend_state_wq,
 372                         backend_state == expected, 5 * HZ);
 373         if (timeout <= 0)
 374                 pr_info("backend %s timed out\n", be);
 375 }
 376
 377 /*
 378  * Reset frontend if it is in Connected or Closed state.
 379  * Wait for backend to catch up.
 380  * State Connected happens during kdump, Closed after kexec.
 381  */
 382 static void xenbus_reset_frontend(char *fe, char *be, int be_state)
 383 {
 384         struct xenbus_watch be_watch;
 385
 386         printk(KERN_DEBUG "XENBUS: backend %s %s\n",
 387                         be, xenbus_strstate(be_state));
 388
 389         memset(&be_watch, 0, sizeof(be_watch));
 390         be_watch.node = kasprintf(GFP_NOIO | __GFP_HIGH, "%s/state", be);
 391         if (!be_watch.node)
 392                 return;
 393
 394         be_watch.callback = xenbus_reset_backend_state_changed;
 395         backend_state = XenbusStateUnknown;
 396
 397         pr_info("triggering reconnect on %s\n", be);
 398         register_xenbus_watch(&be_watch);
 399
 400         /* fall through to forward backend to state XenbusStateInitialising */
 401         switch (be_state) {
 402         case XenbusStateConnected:
 403                 xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosing);
 404                 xenbus_reset_wait_for_backend(be, XenbusStateClosing);
 405                 /* fall through */
 406
 407         case XenbusStateClosing:
 408                 xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosed);
 409                 xenbus_reset_wait_for_backend(be, XenbusStateClosed);
 410                 /* fall through */
 411
 412         case XenbusStateClosed:
 413                 xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateInitialising);
 414                 xenbus_reset_wait_for_backend(be, XenbusStateInitWait);
 415         }
 416
 417         unregister_xenbus_watch(&be_watch);
 418         pr_info("reconnect done on %s\n", be);
 419         kfree(be_watch.node);
 420 }
 421
 422 static void xenbus_check_frontend(char *class, char *dev)
 423 {
 424         int be_state, fe_state, err;
 425         char *backend, *frontend;
 426
 427         frontend = kasprintf(GFP_NOIO | __GFP_HIGH, "device/%s/%s", class, dev);
 428         if (!frontend)
 429                 return;
 430
 431         err = xenbus_scanf(XBT_NIL, frontend, "state", "%i", &fe_state);
 432         if (err != 1)
 433                 goto out;
 434
 435         switch (fe_state) {
 436         case XenbusStateConnected:
 437         case XenbusStateClosed:
 438                 printk(KERN_DEBUG "XENBUS: frontend %s %s\n",
 439                                 frontend, xenbus_strstate(fe_state));
 440                 backend = xenbus_read(XBT_NIL, frontend, "backend", NULL);
 441                 if (!backend || IS_ERR(backend))
 442                         goto out;
 443                 err = xenbus_scanf(XBT_NIL, backend, "state", "%i", &be_state);
 444                 if (err == 1)
 445                         xenbus_reset_frontend(frontend, backend, be_state);
 446                 kfree(backend);
 447                 break;
 448         default:
 449                 break;
 450         }
 451 out:
 452         kfree(frontend);
 453 }
 454
 455 static void xenbus_reset_state(void)
 456 {
 457         char **devclass, **dev;
 458         int devclass_n, dev_n;
 459         int i, j;
 460
 461         devclass = xenbus_directory(XBT_NIL, "device", "", &devclass_n);
 462         if (IS_ERR(devclass))
 463                 return;
 464
 465         for (i = 0; i < devclass_n; i++) {
 466                 dev = xenbus_directory(XBT_NIL, "device", devclass[i], &dev_n);
 467                 if (IS_ERR(dev))
 468                         continue;
 469                 for (j = 0; j < dev_n; j++)
 470                         xenbus_check_frontend(devclass[i], dev[j]);
 471                 kfree(dev);
 472         }
 473         kfree(devclass);
 474 }
 475
 476 static int frontend_probe_and_watch(struct notifier_block *notifier,
 477                                    unsigned long event,
 478                                    void *data)
 479 {
 480         /* reset devices in Connected or Closed state */
 481         if (xen_hvm_domain())
 482                 xenbus_reset_state();
 483         /* Enumerate devices in xenstore and watch for changes. */
 484         xenbus_probe_devices(&xenbus_frontend);
 485         register_xenbus_watch(&fe_watch);
 486
 487         return NOTIFY_DONE;
 488 }
 489
 490
 491 static int __init xenbus_probe_frontend_init(void)
 492 {
 493         static struct notifier_block xenstore_notifier = {
 494                 .notifier_call = frontend_probe_and_watch
 495         };
 496         int err;
 497
 498         DPRINTK("");
 499
 500         /* Register ourselves with the kernel bus subsystem */
 501         err = bus_register(&xenbus_frontend.bus);
 502         if (err)
 503                 return err;
 504
 505         register_xenstore_notifier(&xenstore_notifier);
 506
 507         return 0;
 508 }
 509 subsys_initcall(xenbus_probe_frontend_init);
 510
 511 #ifndef MODULE
 512 static int __init boot_wait_for_devices(void)
 513 {
 514         if (!xen_has_pv_devices())
 515                 return -ENODEV;
 516
 517         ready_to_wait_for_devices = 1;
 518         wait_for_devices(NULL);
 519         return 0;
 520 }
 521
 522 late_initcall(boot_wait_for_devices);
 523 #endif
 524
 525 MODULE_LICENSE("GPL");