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