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_comms.h"
  31 #include "xenbus_probe.h"
  32
  33
  34 static struct workqueue_struct *xenbus_frontend_wq;
  35
  36 /* device/<type>/<id> => <type>-<id> */
  37 static int frontend_bus_id(char bus_id[XEN_BUS_ID_SIZE], const char *nodename)
  38 {
  39         nodename = strchr(nodename, '/');
  40         if (!nodename || strlen(nodename + 1) >= XEN_BUS_ID_SIZE) {
  41                 pr_warn("bad frontend %s\n", nodename);
  42                 return -EINVAL;
  43         }
  44
  45         strlcpy(bus_id, nodename + 1, XEN_BUS_ID_SIZE);
  46         if (!strchr(bus_id, '/')) {
  47                 pr_warn("bus_id %s no slash\n", bus_id);
  48                 return -EINVAL;
  49         }
  50         *strchr(bus_id, '/') = '-';
  51         return 0;
  52 }
  53
  54 /* device/<typename>/<name> */
  55 static int xenbus_probe_frontend(struct xen_bus_type *bus, const char *type,
  56                                  const char *name)
  57 {
  58         char *nodename;
  59         int err;
  60
  61         /* ignore console/0 */
  62         if (!strncmp(type, "console", 7) && !strncmp(name, "0", 1)) {
  63                 DPRINTK("Ignoring buggy device entry console/0");
  64                 return 0;
  65         }
  66
  67         nodename = kasprintf(GFP_KERNEL, "%s/%s/%s", bus->root, type, name);
  68         if (!nodename)
  69                 return -ENOMEM;
  70
  71         DPRINTK("%s", nodename);
  72
  73         err = xenbus_probe_node(bus, type, nodename);
  74         kfree(nodename);
  75         return err;
  76 }
  77
  78 static int xenbus_uevent_frontend(struct device *_dev,
  79                                   struct kobj_uevent_env *env)
  80 {
  81         struct xenbus_device *dev = to_xenbus_device(_dev);
  82
  83         if (add_uevent_var(env, "MODALIAS=xen:%s", dev->devicetype))
  84                 return -ENOMEM;
  85
  86         return 0;
  87 }
  88
  89
  90 static void backend_changed(struct xenbus_watch *watch,
  91                             const char **vec, unsigned int len)
  92 {
  93         xenbus_otherend_changed(watch, vec, len, 1);
  94 }
  95
  96 static void xenbus_frontend_delayed_resume(struct work_struct *w)
  97 {
  98         struct xenbus_device *xdev = container_of(w, struct xenbus_device, work);
  99
 100         xenbus_dev_resume(&xdev->dev);
 101 }
 102
 103 static int xenbus_frontend_dev_resume(struct device *dev)
 104 {
 105         /*
 106          * If xenstored is running in this domain, we cannot access the backend
 107          * state at the moment, so we need to defer xenbus_dev_resume
 108          */
 109         if (xen_store_domain_type == XS_LOCAL) {
 110                 struct xenbus_device *xdev = to_xenbus_device(dev);
 111
 112                 if (!xenbus_frontend_wq) {
 113                         pr_err("%s: no workqueue to process delayed resume\n",
 114                                xdev->nodename);
 115                         return -EFAULT;
 116                 }
 117
 118                 INIT_WORK(&xdev->work, xenbus_frontend_delayed_resume);
 119                 queue_work(xenbus_frontend_wq, &xdev->work);
 120
 121                 return 0;
 122         }
 123
 124         return xenbus_dev_resume(dev);
 125 }
 126
 127 static const struct dev_pm_ops xenbus_pm_ops = {
 128         .suspend        = xenbus_dev_suspend,
 129         .resume         = xenbus_frontend_dev_resume,
 130         .freeze         = xenbus_dev_suspend,
 131         .thaw           = xenbus_dev_cancel,
 132         .restore        = xenbus_dev_resume,
 133 };
 134
 135 static struct xen_bus_type xenbus_frontend = {
 136         .root = "device",
 137         .levels = 2,            /* device/type/<id> */
 138         .get_bus_id = frontend_bus_id,
 139         .probe = xenbus_probe_frontend,
 140         .otherend_changed = backend_changed,
 141         .bus = {
 142                 .name           = "xen",
 143                 .match          = xenbus_match,
 144                 .uevent         = xenbus_uevent_frontend,
 145                 .probe          = xenbus_dev_probe,
 146                 .remove         = xenbus_dev_remove,
 147                 .shutdown       = xenbus_dev_shutdown,
 148                 .dev_attrs      = xenbus_dev_attrs,
 149
 150                 .pm             = &xenbus_pm_ops,
 151         },
 152 };
 153
 154 static void frontend_changed(struct xenbus_watch *watch,
 155                              const char **vec, unsigned int len)
 156 {
 157         DPRINTK("");
 158
 159         xenbus_dev_changed(vec[XS_WATCH_PATH], &xenbus_frontend);
 160 }
 161
 162
 163 /* We watch for devices appearing and vanishing. */
 164 static struct xenbus_watch fe_watch = {
 165         .node = "device",
 166         .callback = frontend_changed,
 167 };
 168
 169 static int read_backend_details(struct xenbus_device *xendev)
 170 {
 171         return xenbus_read_otherend_details(xendev, "backend-id", "backend");
 172 }
 173
 174 static int is_device_connecting(struct device *dev, void *data, bool ignore_nonessential)
 175 {
 176         struct xenbus_device *xendev = to_xenbus_device(dev);
 177         struct device_driver *drv = data;
 178         struct xenbus_driver *xendrv;
 179
 180         /*
 181          * A device with no driver will never connect. We care only about
 182          * devices which should currently be in the process of connecting.
 183          */
 184         if (!dev->driver)
 185                 return 0;
 186
 187         /* Is this search limited to a particular driver? */
 188         if (drv && (dev->driver != drv))
 189                 return 0;
 190
 191         if (ignore_nonessential) {
 192                 /* With older QEMU, for PVonHVM guests the guest config files
 193                  * could contain: vfb = [ 'vnc=1, vnclisten=0.0.0.0']
 194                  * which is nonsensical as there is no PV FB (there can be
 195                  * a PVKB) running as HVM guest. */
 196
 197                 if ((strncmp(xendev->nodename, "device/vkbd", 11) == 0))
 198                         return 0;
 199
 200                 if ((strncmp(xendev->nodename, "device/vfb", 10) == 0))
 201                         return 0;
 202         }
 203         xendrv = to_xenbus_driver(dev->driver);
 204         return (xendev->state < XenbusStateConnected ||
 205                 (xendev->state == XenbusStateConnected &&
 206                  xendrv->is_ready && !xendrv->is_ready(xendev)));
 207 }
 208 static int essential_device_connecting(struct device *dev, void *data)
 209 {
 210         return is_device_connecting(dev, data, true /* ignore PV[KBB+FB] */);
 211 }
 212 static int non_essential_device_connecting(struct device *dev, void *data)
 213 {
 214         return is_device_connecting(dev, data, false);
 215 }
 216
 217 static int exists_essential_connecting_device(struct device_driver *drv)
 218 {
 219         return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
 220                                 essential_device_connecting);
 221 }
 222 static int exists_non_essential_connecting_device(struct device_driver *drv)
 223 {
 224         return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
 225                                 non_essential_device_connecting);
 226 }
 227
 228 static int print_device_status(struct device *dev, void *data)
 229 {
 230         struct xenbus_device *xendev = to_xenbus_device(dev);
 231         struct device_driver *drv = data;
 232
 233         /* Is this operation limited to a particular driver? */
 234         if (drv && (dev->driver != drv))
 235                 return 0;
 236
 237         if (!dev->driver) {
 238                 /* Information only: is this too noisy? */
 239                 pr_info("Device with no driver: %s\n", xendev->nodename);
 240         } else if (xendev->state < XenbusStateConnected) {
 241                 enum xenbus_state rstate = XenbusStateUnknown;
 242                 if (xendev->otherend)
 243                         rstate = xenbus_read_driver_state(xendev->otherend);
 244                 pr_warn("Timeout connecting to device: %s (local state %d, remote state %d)\n",
 245                         xendev->nodename, xendev->state, rstate);
 246         }
 247
 248         return 0;
 249 }
 250
 251 /* We only wait for device setup after most initcalls have run. */
 252 static int ready_to_wait_for_devices;
 253
 254 static bool wait_loop(unsigned long start, unsigned int max_delay,
 255                      unsigned int *seconds_waited)
 256 {
 257         if (time_after(jiffies, start + (*seconds_waited+5)*HZ)) {
 258                 if (!*seconds_waited)
 259                         pr_warn("Waiting for devices to initialise: ");
 260                 *seconds_waited += 5;
 261                 pr_cont("%us...", max_delay - *seconds_waited);
 262                 if (*seconds_waited == max_delay) {
 263                         pr_cont("\n");
 264                         return true;
 265                 }
 266         }
 267
 268         schedule_timeout_interruptible(HZ/10);
 269
 270         return false;
 271 }
 272 /*
 273  * On a 5-minute timeout, wait for all devices currently configured.  We need
 274  * to do this to guarantee that the filesystems and / or network devices
 275  * needed for boot are available, before we can allow the boot to proceed.
 276  *
 277  * This needs to be on a late_initcall, to happen after the frontend device
 278  * drivers have been initialised, but before the root fs is mounted.
 279  *
 280  * A possible improvement here would be to have the tools add a per-device
 281  * flag to the store entry, indicating whether it is needed at boot time.
 282  * This would allow people who knew what they were doing to accelerate their
 283  * boot slightly, but of course needs tools or manual intervention to set up
 284  * those flags correctly.
 285  */
 286 static void wait_for_devices(struct xenbus_driver *xendrv)
 287 {
 288         unsigned long start = jiffies;
 289         struct device_driver *drv = xendrv ? &xendrv->driver : NULL;
 290         unsigned int seconds_waited = 0;
 291
 292         if (!ready_to_wait_for_devices || !xen_domain())
 293                 return;
 294
 295         while (exists_non_essential_connecting_device(drv))
 296                 if (wait_loop(start, 30, &seconds_waited))
 297                         break;
 298
 299         /* Skips PVKB and PVFB check.*/
 300         while (exists_essential_connecting_device(drv))
 301                 if (wait_loop(start, 270, &seconds_waited))
 302                         break;
 303
 304         if (seconds_waited)
 305                 printk("\n");
 306
 307         bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
 308                          print_device_status);
 309 }
 310
 311 int xenbus_register_frontend(struct xenbus_driver *drv)
 312 {
 313         int ret;
 314
 315         drv->read_otherend_details = read_backend_details;
 316
 317         ret = xenbus_register_driver_common(drv, &xenbus_frontend);
 318         if (ret)
 319                 return ret;
 320
 321         /* If this driver is loaded as a module wait for devices to attach. */
 322         wait_for_devices(drv);
 323
 324         return 0;
 325 }
 326 EXPORT_SYMBOL_GPL(xenbus_register_frontend);
 327
 328 static DECLARE_WAIT_QUEUE_HEAD(backend_state_wq);
 329 static int backend_state;
 330
 331 static void xenbus_reset_backend_state_changed(struct xenbus_watch *w,
 332                                         const char **v, unsigned int l)
 333 {
 334         xenbus_scanf(XBT_NIL, v[XS_WATCH_PATH], "", "%i", &backend_state);
 335         printk(KERN_DEBUG "XENBUS: backend %s %s\n",
 336                         v[XS_WATCH_PATH], xenbus_strstate(backend_state));
 337         wake_up(&backend_state_wq);
 338 }
 339
 340 static void xenbus_reset_wait_for_backend(char *be, int expected)
 341 {
 342         long timeout;
 343         timeout = wait_event_interruptible_timeout(backend_state_wq,
 344                         backend_state == expected, 5 * HZ);
 345         if (timeout <= 0)
 346                 pr_info("backend %s timed out\n", be);
 347 }
 348
 349 /*
 350  * Reset frontend if it is in Connected or Closed state.
 351  * Wait for backend to catch up.
 352  * State Connected happens during kdump, Closed after kexec.
 353  */
 354 static void xenbus_reset_frontend(char *fe, char *be, int be_state)
 355 {
 356         struct xenbus_watch be_watch;
 357
 358         printk(KERN_DEBUG "XENBUS: backend %s %s\n",
 359                         be, xenbus_strstate(be_state));
 360
 361         memset(&be_watch, 0, sizeof(be_watch));
 362         be_watch.node = kasprintf(GFP_NOIO | __GFP_HIGH, "%s/state", be);
 363         if (!be_watch.node)
 364                 return;
 365
 366         be_watch.callback = xenbus_reset_backend_state_changed;
 367         backend_state = XenbusStateUnknown;
 368
 369         pr_info("triggering reconnect on %s\n", be);
 370         register_xenbus_watch(&be_watch);
 371
 372         /* fall through to forward backend to state XenbusStateInitialising */
 373         switch (be_state) {
 374         case XenbusStateConnected:
 375                 xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosing);
 376                 xenbus_reset_wait_for_backend(be, XenbusStateClosing);
 377
 378         case XenbusStateClosing:
 379                 xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosed);
 380                 xenbus_reset_wait_for_backend(be, XenbusStateClosed);
 381
 382         case XenbusStateClosed:
 383                 xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateInitialising);
 384                 xenbus_reset_wait_for_backend(be, XenbusStateInitWait);
 385         }
 386
 387         unregister_xenbus_watch(&be_watch);
 388         pr_info("reconnect done on %s\n", be);
 389         kfree(be_watch.node);
 390 }
 391
 392 static void xenbus_check_frontend(char *class, char *dev)
 393 {
 394         int be_state, fe_state, err;
 395         char *backend, *frontend;
 396
 397         frontend = kasprintf(GFP_NOIO | __GFP_HIGH, "device/%s/%s", class, dev);
 398         if (!frontend)
 399                 return;
 400
 401         err = xenbus_scanf(XBT_NIL, frontend, "state", "%i", &fe_state);
 402         if (err != 1)
 403                 goto out;
 404
 405         switch (fe_state) {
 406         case XenbusStateConnected:
 407         case XenbusStateClosed:
 408                 printk(KERN_DEBUG "XENBUS: frontend %s %s\n",
 409                                 frontend, xenbus_strstate(fe_state));
 410                 backend = xenbus_read(XBT_NIL, frontend, "backend", NULL);
 411                 if (!backend || IS_ERR(backend))
 412                         goto out;
 413                 err = xenbus_scanf(XBT_NIL, backend, "state", "%i", &be_state);
 414                 if (err == 1)
 415                         xenbus_reset_frontend(frontend, backend, be_state);
 416                 kfree(backend);
 417                 break;
 418         default:
 419                 break;
 420         }
 421 out:
 422         kfree(frontend);
 423 }
 424
 425 static void xenbus_reset_state(void)
 426 {
 427         char **devclass, **dev;
 428         int devclass_n, dev_n;
 429         int i, j;
 430
 431         devclass = xenbus_directory(XBT_NIL, "device", "", &devclass_n);
 432         if (IS_ERR(devclass))
 433                 return;
 434
 435         for (i = 0; i < devclass_n; i++) {
 436                 dev = xenbus_directory(XBT_NIL, "device", devclass[i], &dev_n);
 437                 if (IS_ERR(dev))
 438                         continue;
 439                 for (j = 0; j < dev_n; j++)
 440                         xenbus_check_frontend(devclass[i], dev[j]);
 441                 kfree(dev);
 442         }
 443         kfree(devclass);
 444 }
 445
 446 static int frontend_probe_and_watch(struct notifier_block *notifier,
 447                                    unsigned long event,
 448                                    void *data)
 449 {
 450         /* reset devices in Connected or Closed state */
 451         if (xen_hvm_domain())
 452                 xenbus_reset_state();
 453         /* Enumerate devices in xenstore and watch for changes. */
 454         xenbus_probe_devices(&xenbus_frontend);
 455         register_xenbus_watch(&fe_watch);
 456
 457         return NOTIFY_DONE;
 458 }
 459
 460
 461 static int __init xenbus_probe_frontend_init(void)
 462 {
 463         static struct notifier_block xenstore_notifier = {
 464                 .notifier_call = frontend_probe_and_watch
 465         };
 466         int err;
 467
 468         DPRINTK("");
 469
 470         /* Register ourselves with the kernel bus subsystem */
 471         err = bus_register(&xenbus_frontend.bus);
 472         if (err)
 473                 return err;
 474
 475         register_xenstore_notifier(&xenstore_notifier);
 476
 477         xenbus_frontend_wq = create_workqueue("xenbus_frontend");
 478
 479         return 0;
 480 }
 481 subsys_initcall(xenbus_probe_frontend_init);
 482
 483 #ifndef MODULE
 484 static int __init boot_wait_for_devices(void)
 485 {
 486         if (xen_hvm_domain() && !xen_platform_pci_unplug)
 487                 return -ENODEV;
 488
 489         ready_to_wait_for_devices = 1;
 490         wait_for_devices(NULL);
 491         return 0;
 492 }
 493
 494 late_initcall(boot_wait_for_devices);
 495 #endif
 496
 497 MODULE_LICENSE("GPL");