drivers/xen/xenbus/xenbus_probe_frontend.c

   1 #define DPRINTK(fmt, args...)                           \
   2         pr_debug("xenbus_probe (%s:%d) " fmt ".\n",     \
   3                  __func__, __LINE__, ##args)
   4
   5 #include <linux/kernel.h>
   6 #include <linux/err.h>
   7 #include <linux/string.h>
   8 #include <linux/ctype.h>
   9 #include <linux/fcntl.h>
  10 #include <linux/mm.h>
  11 #include <linux/proc_fs.h>
  12 #include <linux/notifier.h>
  13 #include <linux/kthread.h>
  14 #include <linux/mutex.h>
  15 #include <linux/io.h>
  16 #include <linux/module.h>
  17
  18 #include <asm/page.h>
  19 #include <asm/pgtable.h>
  20 #include <asm/xen/hypervisor.h>
  21 #include <xen/xenbus.h>
  22 #include <xen/events.h>
  23 #include <xen/page.h>
  24
  25 #include <xen/platform_pci.h>
  26
  27 #include "xenbus_comms.h"
  28 #include "xenbus_probe.h"
  29
  30
  31 /* device/<type>/<id> => <type>-<id> */
  32 static int frontend_bus_id(char bus_id[XEN_BUS_ID_SIZE], const char *nodename)
  33 {
  34         nodename = strchr(nodename, '/');
  35         if (!nodename || strlen(nodename + 1) >= XEN_BUS_ID_SIZE) {
  36                 printk(KERN_WARNING "XENBUS: bad frontend %s\n", nodename);
  37                 return -EINVAL;
  38         }
  39
  40         strlcpy(bus_id, nodename + 1, XEN_BUS_ID_SIZE);
  41         if (!strchr(bus_id, '/')) {
  42                 printk(KERN_WARNING "XENBUS: bus_id %s no slash\n", bus_id);
  43                 return -EINVAL;
  44         }
  45         *strchr(bus_id, '/') = '-';
  46         return 0;
  47 }
  48
  49 /* device/<typename>/<name> */
  50 static int xenbus_probe_frontend(struct xen_bus_type *bus, const char *type,
  51                                  const char *name)
  52 {
  53         char *nodename;
  54         int err;
  55
  56         nodename = kasprintf(GFP_KERNEL, "%s/%s/%s", bus->root, type, name);
  57         if (!nodename)
  58                 return -ENOMEM;
  59
  60         DPRINTK("%s", nodename);
  61
  62         err = xenbus_probe_node(bus, type, nodename);
  63         kfree(nodename);
  64         return err;
  65 }
  66
  67 static int xenbus_uevent_frontend(struct device *_dev,
  68                                   struct kobj_uevent_env *env)
  69 {
  70         struct xenbus_device *dev = to_xenbus_device(_dev);
  71
  72         if (add_uevent_var(env, "MODALIAS=xen:%s", dev->devicetype))
  73                 return -ENOMEM;
  74
  75         return 0;
  76 }
  77
  78
  79 static void backend_changed(struct xenbus_watch *watch,
  80                             const char **vec, unsigned int len)
  81 {
  82         xenbus_otherend_changed(watch, vec, len, 1);
  83 }
  84
  85 static const struct dev_pm_ops xenbus_pm_ops = {
  86         .suspend        = xenbus_dev_suspend,
  87         .resume         = xenbus_dev_resume,
  88         .freeze         = xenbus_dev_suspend,
  89         .thaw           = xenbus_dev_cancel,
  90         .restore        = xenbus_dev_resume,
  91 };
  92
  93 static struct xen_bus_type xenbus_frontend = {
  94         .root = "device",
  95         .levels = 2,            /* device/type/<id> */
  96         .get_bus_id = frontend_bus_id,
  97         .probe = xenbus_probe_frontend,
  98         .otherend_changed = backend_changed,
  99         .bus = {
 100                 .name           = "xen",
 101                 .match          = xenbus_match,
 102                 .uevent         = xenbus_uevent_frontend,
 103                 .probe          = xenbus_dev_probe,
 104                 .remove         = xenbus_dev_remove,
 105                 .shutdown       = xenbus_dev_shutdown,
 106                 .dev_attrs      = xenbus_dev_attrs,
 107
 108                 .pm             = &xenbus_pm_ops,
 109         },
 110 };
 111
 112 static void frontend_changed(struct xenbus_watch *watch,
 113                              const char **vec, unsigned int len)
 114 {
 115         DPRINTK("");
 116
 117         xenbus_dev_changed(vec[XS_WATCH_PATH], &xenbus_frontend);
 118 }
 119
 120
 121 /* We watch for devices appearing and vanishing. */
 122 static struct xenbus_watch fe_watch = {
 123         .node = "device",
 124         .callback = frontend_changed,
 125 };
 126
 127 static int read_backend_details(struct xenbus_device *xendev)
 128 {
 129         return xenbus_read_otherend_details(xendev, "backend-id", "backend");
 130 }
 131
 132 static int is_device_connecting(struct device *dev, void *data, bool ignore_nonessential)
 133 {
 134         struct xenbus_device *xendev = to_xenbus_device(dev);
 135         struct device_driver *drv = data;
 136         struct xenbus_driver *xendrv;
 137
 138         /*
 139          * A device with no driver will never connect. We care only about
 140          * devices which should currently be in the process of connecting.
 141          */
 142         if (!dev->driver)
 143                 return 0;
 144
 145         /* Is this search limited to a particular driver? */
 146         if (drv && (dev->driver != drv))
 147                 return 0;
 148
 149         if (ignore_nonessential) {
 150                 /* With older QEMU, for PVonHVM guests the guest config files
 151                  * could contain: vfb = [ 'vnc=1, vnclisten=0.0.0.0']
 152                  * which is nonsensical as there is no PV FB (there can be
 153                  * a PVKB) running as HVM guest. */
 154
 155                 if ((strncmp(xendev->nodename, "device/vkbd", 11) == 0))
 156                         return 0;
 157
 158                 if ((strncmp(xendev->nodename, "device/vfb", 10) == 0))
 159                         return 0;
 160         }
 161         xendrv = to_xenbus_driver(dev->driver);
 162         return (xendev->state < XenbusStateConnected ||
 163                 (xendev->state == XenbusStateConnected &&
 164                  xendrv->is_ready && !xendrv->is_ready(xendev)));
 165 }
 166 static int essential_device_connecting(struct device *dev, void *data)
 167 {
 168         return is_device_connecting(dev, data, true /* ignore PV[KBB+FB] */);
 169 }
 170 static int non_essential_device_connecting(struct device *dev, void *data)
 171 {
 172         return is_device_connecting(dev, data, false);
 173 }
 174
 175 static int exists_essential_connecting_device(struct device_driver *drv)
 176 {
 177         return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
 178                                 essential_device_connecting);
 179 }
 180 static int exists_non_essential_connecting_device(struct device_driver *drv)
 181 {
 182         return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
 183                                 non_essential_device_connecting);
 184 }
 185
 186 static int print_device_status(struct device *dev, void *data)
 187 {
 188         struct xenbus_device *xendev = to_xenbus_device(dev);
 189         struct device_driver *drv = data;
 190
 191         /* Is this operation limited to a particular driver? */
 192         if (drv && (dev->driver != drv))
 193                 return 0;
 194
 195         if (!dev->driver) {
 196                 /* Information only: is this too noisy? */
 197                 printk(KERN_INFO "XENBUS: Device with no driver: %s\n",
 198                        xendev->nodename);
 199         } else if (xendev->state < XenbusStateConnected) {
 200                 enum xenbus_state rstate = XenbusStateUnknown;
 201                 if (xendev->otherend)
 202                         rstate = xenbus_read_driver_state(xendev->otherend);
 203                 printk(KERN_WARNING "XENBUS: Timeout connecting "
 204                        "to device: %s (local state %d, remote state %d)\n",
 205                        xendev->nodename, xendev->state, rstate);
 206         }
 207
 208         return 0;
 209 }
 210
 211 /* We only wait for device setup after most initcalls have run. */
 212 static int ready_to_wait_for_devices;
 213
 214 static bool wait_loop(unsigned long start, unsigned int max_delay,
 215                      unsigned int *seconds_waited)
 216 {
 217         if (time_after(jiffies, start + (*seconds_waited+5)*HZ)) {
 218                 if (!*seconds_waited)
 219                         printk(KERN_WARNING "XENBUS: Waiting for "
 220                                "devices to initialise: ");
 221                 *seconds_waited += 5;
 222                 printk("%us...", max_delay - *seconds_waited);
 223                 if (*seconds_waited == max_delay)
 224                         return true;
 225         }
 226
 227         schedule_timeout_interruptible(HZ/10);
 228
 229         return false;
 230 }
 231 /*
 232  * On a 5-minute timeout, wait for all devices currently configured.  We need
 233  * to do this to guarantee that the filesystems and / or network devices
 234  * needed for boot are available, before we can allow the boot to proceed.
 235  *
 236  * This needs to be on a late_initcall, to happen after the frontend device
 237  * drivers have been initialised, but before the root fs is mounted.
 238  *
 239  * A possible improvement here would be to have the tools add a per-device
 240  * flag to the store entry, indicating whether it is needed at boot time.
 241  * This would allow people who knew what they were doing to accelerate their
 242  * boot slightly, but of course needs tools or manual intervention to set up
 243  * those flags correctly.
 244  */
 245 static void wait_for_devices(struct xenbus_driver *xendrv)
 246 {
 247         unsigned long start = jiffies;
 248         struct device_driver *drv = xendrv ? &xendrv->driver : NULL;
 249         unsigned int seconds_waited = 0;
 250
 251         if (!ready_to_wait_for_devices || !xen_domain())
 252                 return;
 253
 254         while (exists_non_essential_connecting_device(drv))
 255                 if (wait_loop(start, 30, &seconds_waited))
 256                         break;
 257
 258         /* Skips PVKB and PVFB check.*/
 259         while (exists_essential_connecting_device(drv))
 260                 if (wait_loop(start, 270, &seconds_waited))
 261                         break;
 262
 263         if (seconds_waited)
 264                 printk("\n");
 265
 266         bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
 267                          print_device_status);
 268 }
 269
 270 int xenbus_register_frontend(struct xenbus_driver *drv)
 271 {
 272         int ret;
 273
 274         drv->read_otherend_details = read_backend_details;
 275
 276         ret = xenbus_register_driver_common(drv, &xenbus_frontend);
 277         if (ret)
 278                 return ret;
 279
 280         /* If this driver is loaded as a module wait for devices to attach. */
 281         wait_for_devices(drv);
 282
 283         return 0;
 284 }
 285 EXPORT_SYMBOL_GPL(xenbus_register_frontend);
 286
 287 static DECLARE_WAIT_QUEUE_HEAD(backend_state_wq);
 288 static int backend_state;
 289
 290 static void xenbus_reset_backend_state_changed(struct xenbus_watch *w,
 291                                         const char **v, unsigned int l)
 292 {
 293         xenbus_scanf(XBT_NIL, v[XS_WATCH_PATH], "", "%i", &backend_state);
 294         printk(KERN_DEBUG "XENBUS: backend %s %s\n",
 295                         v[XS_WATCH_PATH], xenbus_strstate(backend_state));
 296         wake_up(&backend_state_wq);
 297 }
 298
 299 static void xenbus_reset_wait_for_backend(char *be, int expected)
 300 {
 301         long timeout;
 302         timeout = wait_event_interruptible_timeout(backend_state_wq,
 303                         backend_state == expected, 5 * HZ);
 304         if (timeout <= 0)
 305                 printk(KERN_INFO "XENBUS: backend %s timed out.\n", be);
 306 }
 307
 308 /*
 309  * Reset frontend if it is in Connected or Closed state.
 310  * Wait for backend to catch up.
 311  * State Connected happens during kdump, Closed after kexec.
 312  */
 313 static void xenbus_reset_frontend(char *fe, char *be, int be_state)
 314 {
 315         struct xenbus_watch be_watch;
 316
 317         printk(KERN_DEBUG "XENBUS: backend %s %s\n",
 318                         be, xenbus_strstate(be_state));
 319
 320         memset(&be_watch, 0, sizeof(be_watch));
 321         be_watch.node = kasprintf(GFP_NOIO | __GFP_HIGH, "%s/state", be);
 322         if (!be_watch.node)
 323                 return;
 324
 325         be_watch.callback = xenbus_reset_backend_state_changed;
 326         backend_state = XenbusStateUnknown;
 327
 328         printk(KERN_INFO "XENBUS: triggering reconnect on %s\n", be);
 329         register_xenbus_watch(&be_watch);
 330
 331         /* fall through to forward backend to state XenbusStateInitialising */
 332         switch (be_state) {
 333         case XenbusStateConnected:
 334                 xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosing);
 335                 xenbus_reset_wait_for_backend(be, XenbusStateClosing);
 336
 337         case XenbusStateClosing:
 338                 xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosed);
 339                 xenbus_reset_wait_for_backend(be, XenbusStateClosed);
 340
 341         case XenbusStateClosed:
 342                 xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateInitialising);
 343                 xenbus_reset_wait_for_backend(be, XenbusStateInitWait);
 344         }
 345
 346         unregister_xenbus_watch(&be_watch);
 347         printk(KERN_INFO "XENBUS: reconnect done on %s\n", be);
 348         kfree(be_watch.node);
 349 }
 350
 351 static void xenbus_check_frontend(char *class, char *dev)
 352 {
 353         int be_state, fe_state, err;
 354         char *backend, *frontend;
 355
 356         frontend = kasprintf(GFP_NOIO | __GFP_HIGH, "device/%s/%s", class, dev);
 357         if (!frontend)
 358                 return;
 359
 360         err = xenbus_scanf(XBT_NIL, frontend, "state", "%i", &fe_state);
 361         if (err != 1)
 362                 goto out;
 363
 364         switch (fe_state) {
 365         case XenbusStateConnected:
 366         case XenbusStateClosed:
 367                 printk(KERN_DEBUG "XENBUS: frontend %s %s\n",
 368                                 frontend, xenbus_strstate(fe_state));
 369                 backend = xenbus_read(XBT_NIL, frontend, "backend", NULL);
 370                 if (!backend || IS_ERR(backend))
 371                         goto out;
 372                 err = xenbus_scanf(XBT_NIL, backend, "state", "%i", &be_state);
 373                 if (err == 1)
 374                         xenbus_reset_frontend(frontend, backend, be_state);
 375                 kfree(backend);
 376                 break;
 377         default:
 378                 break;
 379         }
 380 out:
 381         kfree(frontend);
 382 }
 383
 384 static void xenbus_reset_state(void)
 385 {
 386         char **devclass, **dev;
 387         int devclass_n, dev_n;
 388         int i, j;
 389
 390         devclass = xenbus_directory(XBT_NIL, "device", "", &devclass_n);
 391         if (IS_ERR(devclass))
 392                 return;
 393
 394         for (i = 0; i < devclass_n; i++) {
 395                 dev = xenbus_directory(XBT_NIL, "device", devclass[i], &dev_n);
 396                 if (IS_ERR(dev))
 397                         continue;
 398                 for (j = 0; j < dev_n; j++)
 399                         xenbus_check_frontend(devclass[i], dev[j]);
 400                 kfree(dev);
 401         }
 402         kfree(devclass);
 403 }
 404
 405 static int frontend_probe_and_watch(struct notifier_block *notifier,
 406                                    unsigned long event,
 407                                    void *data)
 408 {
 409         /* reset devices in Connected or Closed state */
 410         if (xen_hvm_domain())
 411                 xenbus_reset_state();
 412         /* Enumerate devices in xenstore and watch for changes. */
 413         xenbus_probe_devices(&xenbus_frontend);
 414         register_xenbus_watch(&fe_watch);
 415
 416         return NOTIFY_DONE;
 417 }
 418
 419
 420 static int __init xenbus_probe_frontend_init(void)
 421 {
 422         static struct notifier_block xenstore_notifier = {
 423                 .notifier_call = frontend_probe_and_watch
 424         };
 425         int err;
 426
 427         DPRINTK("");
 428
 429         /* Register ourselves with the kernel bus subsystem */
 430         err = bus_register(&xenbus_frontend.bus);
 431         if (err)
 432                 return err;
 433
 434         register_xenstore_notifier(&xenstore_notifier);
 435
 436         return 0;
 437 }
 438 subsys_initcall(xenbus_probe_frontend_init);
 439
 440 #ifndef MODULE
 441 static int __init boot_wait_for_devices(void)
 442 {
 443         if (xen_hvm_domain() && !xen_platform_pci_unplug)
 444                 return -ENODEV;
 445
 446         ready_to_wait_for_devices = 1;
 447         wait_for_devices(NULL);
 448         return 0;
 449 }
 450
 451 late_initcall(boot_wait_for_devices);
 452 #endif
 453
 454 MODULE_LICENSE("GPL");