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/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                 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
 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");