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                                struct module *owner, const char *mod_name)
 272 {
 273         int ret;
 274
 275         drv->read_otherend_details = read_backend_details;
 276
 277         ret = xenbus_register_driver_common(drv, &xenbus_frontend,
 278                                             owner, mod_name);
 279         if (ret)
 280                 return ret;
 281
 282         /* If this driver is loaded as a module wait for devices to attach. */
 283         wait_for_devices(drv);
 284
 285         return 0;
 286 }
 287 EXPORT_SYMBOL_GPL(__xenbus_register_frontend);
 288
 289 static DECLARE_WAIT_QUEUE_HEAD(backend_state_wq);
 290 static int backend_state;
 291
 292 static void xenbus_reset_backend_state_changed(struct xenbus_watch *w,
 293                                         const char **v, unsigned int l)
 294 {
 295         xenbus_scanf(XBT_NIL, v[XS_WATCH_PATH], "", "%i", &backend_state);
 296         printk(KERN_DEBUG "XENBUS: backend %s %s\n",
 297                         v[XS_WATCH_PATH], xenbus_strstate(backend_state));
 298         wake_up(&backend_state_wq);
 299 }
 300
 301 static void xenbus_reset_wait_for_backend(char *be, int expected)
 302 {
 303         long timeout;
 304         timeout = wait_event_interruptible_timeout(backend_state_wq,
 305                         backend_state == expected, 5 * HZ);
 306         if (timeout <= 0)
 307                 printk(KERN_INFO "XENBUS: backend %s timed out.\n", be);
 308 }
 309
 310 /*
 311  * Reset frontend if it is in Connected or Closed state.
 312  * Wait for backend to catch up.
 313  * State Connected happens during kdump, Closed after kexec.
 314  */
 315 static void xenbus_reset_frontend(char *fe, char *be, int be_state)
 316 {
 317         struct xenbus_watch be_watch;
 318
 319         printk(KERN_DEBUG "XENBUS: backend %s %s\n",
 320                         be, xenbus_strstate(be_state));
 321
 322         memset(&be_watch, 0, sizeof(be_watch));
 323         be_watch.node = kasprintf(GFP_NOIO | __GFP_HIGH, "%s/state", be);
 324         if (!be_watch.node)
 325                 return;
 326
 327         be_watch.callback = xenbus_reset_backend_state_changed;
 328         backend_state = XenbusStateUnknown;
 329
 330         printk(KERN_INFO "XENBUS: triggering reconnect on %s\n", be);
 331         register_xenbus_watch(&be_watch);
 332
 333         /* fall through to forward backend to state XenbusStateInitialising */
 334         switch (be_state) {
 335         case XenbusStateConnected:
 336                 xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosing);
 337                 xenbus_reset_wait_for_backend(be, XenbusStateClosing);
 338
 339         case XenbusStateClosing:
 340                 xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosed);
 341                 xenbus_reset_wait_for_backend(be, XenbusStateClosed);
 342
 343         case XenbusStateClosed:
 344                 xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateInitialising);
 345                 xenbus_reset_wait_for_backend(be, XenbusStateInitWait);
 346         }
 347
 348         unregister_xenbus_watch(&be_watch);
 349         printk(KERN_INFO "XENBUS: reconnect done on %s\n", be);
 350         kfree(be_watch.node);
 351 }
 352
 353 static void xenbus_check_frontend(char *class, char *dev)
 354 {
 355         int be_state, fe_state, err;
 356         char *backend, *frontend;
 357
 358         frontend = kasprintf(GFP_NOIO | __GFP_HIGH, "device/%s/%s", class, dev);
 359         if (!frontend)
 360                 return;
 361
 362         err = xenbus_scanf(XBT_NIL, frontend, "state", "%i", &fe_state);
 363         if (err != 1)
 364                 goto out;
 365
 366         switch (fe_state) {
 367         case XenbusStateConnected:
 368         case XenbusStateClosed:
 369                 printk(KERN_DEBUG "XENBUS: frontend %s %s\n",
 370                                 frontend, xenbus_strstate(fe_state));
 371                 backend = xenbus_read(XBT_NIL, frontend, "backend", NULL);
 372                 if (!backend || IS_ERR(backend))
 373                         goto out;
 374                 err = xenbus_scanf(XBT_NIL, backend, "state", "%i", &be_state);
 375                 if (err == 1)
 376                         xenbus_reset_frontend(frontend, backend, be_state);
 377                 kfree(backend);
 378                 break;
 379         default:
 380                 break;
 381         }
 382 out:
 383         kfree(frontend);
 384 }
 385
 386 static void xenbus_reset_state(void)
 387 {
 388         char **devclass, **dev;
 389         int devclass_n, dev_n;
 390         int i, j;
 391
 392         devclass = xenbus_directory(XBT_NIL, "device", "", &devclass_n);
 393         if (IS_ERR(devclass))
 394                 return;
 395
 396         for (i = 0; i < devclass_n; i++) {
 397                 dev = xenbus_directory(XBT_NIL, "device", devclass[i], &dev_n);
 398                 if (IS_ERR(dev))
 399                         continue;
 400                 for (j = 0; j < dev_n; j++)
 401                         xenbus_check_frontend(devclass[i], dev[j]);
 402                 kfree(dev);
 403         }
 404         kfree(devclass);
 405 }
 406
 407 static int frontend_probe_and_watch(struct notifier_block *notifier,
 408                                    unsigned long event,
 409                                    void *data)
 410 {
 411         /* reset devices in Connected or Closed state */
 412         if (xen_hvm_domain())
 413                 xenbus_reset_state();
 414         /* Enumerate devices in xenstore and watch for changes. */
 415         xenbus_probe_devices(&xenbus_frontend);
 416         register_xenbus_watch(&fe_watch);
 417
 418         return NOTIFY_DONE;
 419 }
 420
 421
 422 static int __init xenbus_probe_frontend_init(void)
 423 {
 424         static struct notifier_block xenstore_notifier = {
 425                 .notifier_call = frontend_probe_and_watch
 426         };
 427         int err;
 428
 429         DPRINTK("");
 430
 431         /* Register ourselves with the kernel bus subsystem */
 432         err = bus_register(&xenbus_frontend.bus);
 433         if (err)
 434                 return err;
 435
 436         register_xenstore_notifier(&xenstore_notifier);
 437
 438         return 0;
 439 }
 440 subsys_initcall(xenbus_probe_frontend_init);
 441
 442 #ifndef MODULE
 443 static int __init boot_wait_for_devices(void)
 444 {
 445         if (xen_hvm_domain() && !xen_platform_pci_unplug)
 446                 return -ENODEV;
 447
 448         ready_to_wait_for_devices = 1;
 449         wait_for_devices(NULL);
 450         return 0;
 451 }
 452
 453 late_initcall(boot_wait_for_devices);
 454 #endif
 455
 456 MODULE_LICENSE("GPL");