drivers/xen/xenbus/xenbus_probe_frontend.c

   1 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   2
   3 #define DPRINTK(fmt, ...)                               \
   4         pr_debug("(%s:%d) " fmt "\n",                   \
   5                  __func__, __LINE__, ##__VA_ARGS__)
   6
   7 #include <linux/kernel.h>
   8 #include <linux/err.h>
   9 #include <linux/string.h>
  10 #include <linux/ctype.h>
  11 #include <linux/fcntl.h>
  12 #include <linux/mm.h>
  13 #include <linux/proc_fs.h>
  14 #include <linux/notifier.h>
  15 #include <linux/kthread.h>
  16 #include <linux/mutex.h>
  17 #include <linux/io.h>
  18 #include <linux/module.h>
  19
  20 #include <asm/page.h>
  21 #include <asm/pgtable.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 const struct dev_pm_ops xenbus_pm_ops = {
 129         .suspend        = xenbus_dev_suspend,
 130         .resume         = xenbus_frontend_dev_resume,
 131         .freeze         = xenbus_dev_suspend,
 132         .thaw           = xenbus_dev_cancel,
 133         .restore        = xenbus_dev_resume,
 134 };
 135
 136 static struct xen_bus_type xenbus_frontend = {
 137         .root = "device",
 138         .levels = 2,            /* device/type/<id> */
 139         .get_bus_id = frontend_bus_id,
 140         .probe = xenbus_probe_frontend,
 141         .otherend_changed = backend_changed,
 142         .bus = {
 143                 .name           = "xen",
 144                 .match          = xenbus_match,
 145                 .uevent         = xenbus_uevent_frontend,
 146                 .probe          = xenbus_frontend_dev_probe,
 147                 .remove         = xenbus_dev_remove,
 148                 .shutdown       = xenbus_dev_shutdown,
 149                 .dev_groups     = xenbus_dev_groups,
 150
 151                 .pm             = &xenbus_pm_ops,
 152         },
 153 };
 154
 155 static void frontend_changed(struct xenbus_watch *watch,
 156                              const char *path, const char *token)
 157 {
 158         DPRINTK("");
 159
 160         xenbus_dev_changed(path, &xenbus_frontend);
 161 }
 162
 163
 164 /* We watch for devices appearing and vanishing. */
 165 static struct xenbus_watch fe_watch = {
 166         .node = "device",
 167         .callback = frontend_changed,
 168 };
 169
 170 static int read_backend_details(struct xenbus_device *xendev)
 171 {
 172         return xenbus_read_otherend_details(xendev, "backend-id", "backend");
 173 }
 174
 175 static int is_device_connecting(struct device *dev, void *data, bool ignore_nonessential)
 176 {
 177         struct xenbus_device *xendev = to_xenbus_device(dev);
 178         struct device_driver *drv = data;
 179         struct xenbus_driver *xendrv;
 180
 181         /*
 182          * A device with no driver will never connect. We care only about
 183          * devices which should currently be in the process of connecting.
 184          */
 185         if (!dev->driver)
 186                 return 0;
 187
 188         /* Is this search limited to a particular driver? */
 189         if (drv && (dev->driver != drv))
 190                 return 0;
 191
 192         if (ignore_nonessential) {
 193                 /* With older QEMU, for PVonHVM guests the guest config files
 194                  * could contain: vfb = [ 'vnc=1, vnclisten=0.0.0.0']
 195                  * which is nonsensical as there is no PV FB (there can be
 196                  * a PVKB) running as HVM guest. */
 197
 198                 if ((strncmp(xendev->nodename, "device/vkbd", 11) == 0))
 199                         return 0;
 200
 201                 if ((strncmp(xendev->nodename, "device/vfb", 10) == 0))
 202                         return 0;
 203         }
 204         xendrv = to_xenbus_driver(dev->driver);
 205         return (xendev->state < XenbusStateConnected ||
 206                 (xendev->state == XenbusStateConnected &&
 207                  xendrv->is_ready && !xendrv->is_ready(xendev)));
 208 }
 209 static int essential_device_connecting(struct device *dev, void *data)
 210 {
 211         return is_device_connecting(dev, data, true /* ignore PV[KBB+FB] */);
 212 }
 213 static int non_essential_device_connecting(struct device *dev, void *data)
 214 {
 215         return is_device_connecting(dev, data, false);
 216 }
 217
 218 static int exists_essential_connecting_device(struct device_driver *drv)
 219 {
 220         return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
 221                                 essential_device_connecting);
 222 }
 223 static int exists_non_essential_connecting_device(struct device_driver *drv)
 224 {
 225         return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
 226                                 non_essential_device_connecting);
 227 }
 228
 229 static int print_device_status(struct device *dev, void *data)
 230 {
 231         struct xenbus_device *xendev = to_xenbus_device(dev);
 232         struct device_driver *drv = data;
 233
 234         /* Is this operation limited to a particular driver? */
 235         if (drv && (dev->driver != drv))
 236                 return 0;
 237
 238         if (!dev->driver) {
 239                 /* Information only: is this too noisy? */
 240                 pr_info("Device with no driver: %s\n", xendev->nodename);
 241         } else if (xendev->state < XenbusStateConnected) {
 242                 enum xenbus_state rstate = XenbusStateUnknown;
 243                 if (xendev->otherend)
 244                         rstate = xenbus_read_driver_state(xendev->otherend);
 245                 pr_warn("Timeout connecting to device: %s (local state %d, remote state %d)\n",
 246                         xendev->nodename, xendev->state, rstate);
 247         }
 248
 249         return 0;
 250 }
 251
 252 /* We only wait for device setup after most initcalls have run. */
 253 static int ready_to_wait_for_devices;
 254
 255 static bool wait_loop(unsigned long start, unsigned int max_delay,
 256                      unsigned int *seconds_waited)
 257 {
 258         if (time_after(jiffies, start + (*seconds_waited+5)*HZ)) {
 259                 if (!*seconds_waited)
 260                         pr_warn("Waiting for devices to initialise: ");
 261                 *seconds_waited += 5;
 262                 pr_cont("%us...", max_delay - *seconds_waited);
 263                 if (*seconds_waited == max_delay) {
 264                         pr_cont("\n");
 265                         return true;
 266                 }
 267         }
 268
 269         schedule_timeout_interruptible(HZ/10);
 270
 271         return false;
 272 }
 273 /*
 274  * On a 5-minute timeout, wait for all devices currently configured.  We need
 275  * to do this to guarantee that the filesystems and / or network devices
 276  * needed for boot are available, before we can allow the boot to proceed.
 277  *
 278  * This needs to be on a late_initcall, to happen after the frontend device
 279  * drivers have been initialised, but before the root fs is mounted.
 280  *
 281  * A possible improvement here would be to have the tools add a per-device
 282  * flag to the store entry, indicating whether it is needed at boot time.
 283  * This would allow people who knew what they were doing to accelerate their
 284  * boot slightly, but of course needs tools or manual intervention to set up
 285  * those flags correctly.
 286  */
 287 static void wait_for_devices(struct xenbus_driver *xendrv)
 288 {
 289         unsigned long start = jiffies;
 290         struct device_driver *drv = xendrv ? &xendrv->driver : NULL;
 291         unsigned int seconds_waited = 0;
 292
 293         if (!ready_to_wait_for_devices || !xen_domain())
 294                 return;
 295
 296         while (exists_non_essential_connecting_device(drv))
 297                 if (wait_loop(start, 30, &seconds_waited))
 298                         break;
 299
 300         /* Skips PVKB and PVFB check.*/
 301         while (exists_essential_connecting_device(drv))
 302                 if (wait_loop(start, 270, &seconds_waited))
 303                         break;
 304
 305         if (seconds_waited)
 306                 printk("\n");
 307
 308         bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
 309                          print_device_status);
 310 }
 311
 312 int __xenbus_register_frontend(struct xenbus_driver *drv, struct module *owner,
 313                                const char *mod_name)
 314 {
 315         int ret;
 316
 317         drv->read_otherend_details = read_backend_details;
 318
 319         ret = xenbus_register_driver_common(drv, &xenbus_frontend,
 320                                             owner, mod_name);
 321         if (ret)
 322                 return ret;
 323
 324         /* If this driver is loaded as a module wait for devices to attach. */
 325         wait_for_devices(drv);
 326
 327         return 0;
 328 }
 329 EXPORT_SYMBOL_GPL(__xenbus_register_frontend);
 330
 331 static DECLARE_WAIT_QUEUE_HEAD(backend_state_wq);
 332 static int backend_state;
 333
 334 static void xenbus_reset_backend_state_changed(struct xenbus_watch *w,
 335                                         const char *path, const char *token)
 336 {
 337         if (xenbus_scanf(XBT_NIL, path, "", "%i",
 338                          &backend_state) != 1)
 339                 backend_state = XenbusStateUnknown;
 340         printk(KERN_DEBUG "XENBUS: backend %s %s\n",
 341                path, xenbus_strstate(backend_state));
 342         wake_up(&backend_state_wq);
 343 }
 344
 345 static void xenbus_reset_wait_for_backend(char *be, int expected)
 346 {
 347         long timeout;
 348         timeout = wait_event_interruptible_timeout(backend_state_wq,
 349                         backend_state == expected, 5 * HZ);
 350         if (timeout <= 0)
 351                 pr_info("backend %s timed out\n", be);
 352 }
 353
 354 /*
 355  * Reset frontend if it is in Connected or Closed state.
 356  * Wait for backend to catch up.
 357  * State Connected happens during kdump, Closed after kexec.
 358  */
 359 static void xenbus_reset_frontend(char *fe, char *be, int be_state)
 360 {
 361         struct xenbus_watch be_watch;
 362
 363         printk(KERN_DEBUG "XENBUS: backend %s %s\n",
 364                         be, xenbus_strstate(be_state));
 365
 366         memset(&be_watch, 0, sizeof(be_watch));
 367         be_watch.node = kasprintf(GFP_NOIO | __GFP_HIGH, "%s/state", be);
 368         if (!be_watch.node)
 369                 return;
 370
 371         be_watch.callback = xenbus_reset_backend_state_changed;
 372         backend_state = XenbusStateUnknown;
 373
 374         pr_info("triggering reconnect on %s\n", be);
 375         register_xenbus_watch(&be_watch);
 376
 377         /* fall through to forward backend to state XenbusStateInitialising */
 378         switch (be_state) {
 379         case XenbusStateConnected:
 380                 xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosing);
 381                 xenbus_reset_wait_for_backend(be, XenbusStateClosing);
 382
 383         case XenbusStateClosing:
 384                 xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosed);
 385                 xenbus_reset_wait_for_backend(be, XenbusStateClosed);
 386
 387         case XenbusStateClosed:
 388                 xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateInitialising);
 389                 xenbus_reset_wait_for_backend(be, XenbusStateInitWait);
 390         }
 391
 392         unregister_xenbus_watch(&be_watch);
 393         pr_info("reconnect done on %s\n", be);
 394         kfree(be_watch.node);
 395 }
 396
 397 static void xenbus_check_frontend(char *class, char *dev)
 398 {
 399         int be_state, fe_state, err;
 400         char *backend, *frontend;
 401
 402         frontend = kasprintf(GFP_NOIO | __GFP_HIGH, "device/%s/%s", class, dev);
 403         if (!frontend)
 404                 return;
 405
 406         err = xenbus_scanf(XBT_NIL, frontend, "state", "%i", &fe_state);
 407         if (err != 1)
 408                 goto out;
 409
 410         switch (fe_state) {
 411         case XenbusStateConnected:
 412         case XenbusStateClosed:
 413                 printk(KERN_DEBUG "XENBUS: frontend %s %s\n",
 414                                 frontend, xenbus_strstate(fe_state));
 415                 backend = xenbus_read(XBT_NIL, frontend, "backend", NULL);
 416                 if (!backend || IS_ERR(backend))
 417                         goto out;
 418                 err = xenbus_scanf(XBT_NIL, backend, "state", "%i", &be_state);
 419                 if (err == 1)
 420                         xenbus_reset_frontend(frontend, backend, be_state);
 421                 kfree(backend);
 422                 break;
 423         default:
 424                 break;
 425         }
 426 out:
 427         kfree(frontend);
 428 }
 429
 430 static void xenbus_reset_state(void)
 431 {
 432         char **devclass, **dev;
 433         int devclass_n, dev_n;
 434         int i, j;
 435
 436         devclass = xenbus_directory(XBT_NIL, "device", "", &devclass_n);
 437         if (IS_ERR(devclass))
 438                 return;
 439
 440         for (i = 0; i < devclass_n; i++) {
 441                 dev = xenbus_directory(XBT_NIL, "device", devclass[i], &dev_n);
 442                 if (IS_ERR(dev))
 443                         continue;
 444                 for (j = 0; j < dev_n; j++)
 445                         xenbus_check_frontend(devclass[i], dev[j]);
 446                 kfree(dev);
 447         }
 448         kfree(devclass);
 449 }
 450
 451 static int frontend_probe_and_watch(struct notifier_block *notifier,
 452                                    unsigned long event,
 453                                    void *data)
 454 {
 455         /* reset devices in Connected or Closed state */
 456         if (xen_hvm_domain())
 457                 xenbus_reset_state();
 458         /* Enumerate devices in xenstore and watch for changes. */
 459         xenbus_probe_devices(&xenbus_frontend);
 460         register_xenbus_watch(&fe_watch);
 461
 462         return NOTIFY_DONE;
 463 }
 464
 465
 466 static int __init xenbus_probe_frontend_init(void)
 467 {
 468         static struct notifier_block xenstore_notifier = {
 469                 .notifier_call = frontend_probe_and_watch
 470         };
 471         int err;
 472
 473         DPRINTK("");
 474
 475         /* Register ourselves with the kernel bus subsystem */
 476         err = bus_register(&xenbus_frontend.bus);
 477         if (err)
 478                 return err;
 479
 480         register_xenstore_notifier(&xenstore_notifier);
 481
 482         return 0;
 483 }
 484 subsys_initcall(xenbus_probe_frontend_init);
 485
 486 #ifndef MODULE
 487 static int __init boot_wait_for_devices(void)
 488 {
 489         if (!xen_has_pv_devices())
 490                 return -ENODEV;
 491
 492         ready_to_wait_for_devices = 1;
 493         wait_for_devices(NULL);
 494         return 0;
 495 }
 496
 497 late_initcall(boot_wait_for_devices);
 498 #endif
 499
 500 MODULE_LICENSE("GPL");