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                 queue_work(xenbus_frontend_wq, &xdev->work);
 119
 120                 return 0;
 121         }
 122
 123         return xenbus_dev_resume(dev);
 124 }
 125
 126 static int xenbus_frontend_dev_probe(struct device *dev)
 127 {
 128         if (xen_store_domain_type == XS_LOCAL) {
 129                 struct xenbus_device *xdev = to_xenbus_device(dev);
 130                 INIT_WORK(&xdev->work, xenbus_frontend_delayed_resume);
 131         }
 132
 133         return xenbus_dev_probe(dev);
 134 }
 135
 136 static const struct dev_pm_ops xenbus_pm_ops = {
 137         .suspend        = xenbus_dev_suspend,
 138         .resume         = xenbus_frontend_dev_resume,
 139         .freeze         = xenbus_dev_suspend,
 140         .thaw           = xenbus_dev_cancel,
 141         .restore        = xenbus_dev_resume,
 142 };
 143
 144 static struct xen_bus_type xenbus_frontend = {
 145         .root = "device",
 146         .levels = 2,            /* device/type/<id> */
 147         .get_bus_id = frontend_bus_id,
 148         .probe = xenbus_probe_frontend,
 149         .otherend_changed = backend_changed,
 150         .bus = {
 151                 .name           = "xen",
 152                 .match          = xenbus_match,
 153                 .uevent         = xenbus_uevent_frontend,
 154                 .probe          = xenbus_frontend_dev_probe,
 155                 .remove         = xenbus_dev_remove,
 156                 .shutdown       = xenbus_dev_shutdown,
 157                 .dev_attrs      = xenbus_dev_attrs,
 158
 159                 .pm             = &xenbus_pm_ops,
 160         },
 161 };
 162
 163 static void frontend_changed(struct xenbus_watch *watch,
 164                              const char **vec, unsigned int len)
 165 {
 166         DPRINTK("");
 167
 168         xenbus_dev_changed(vec[XS_WATCH_PATH], &xenbus_frontend);
 169 }
 170
 171
 172 /* We watch for devices appearing and vanishing. */
 173 static struct xenbus_watch fe_watch = {
 174         .node = "device",
 175         .callback = frontend_changed,
 176 };
 177
 178 static int read_backend_details(struct xenbus_device *xendev)
 179 {
 180         return xenbus_read_otherend_details(xendev, "backend-id", "backend");
 181 }
 182
 183 static int is_device_connecting(struct device *dev, void *data, bool ignore_nonessential)
 184 {
 185         struct xenbus_device *xendev = to_xenbus_device(dev);
 186         struct device_driver *drv = data;
 187         struct xenbus_driver *xendrv;
 188
 189         /*
 190          * A device with no driver will never connect. We care only about
 191          * devices which should currently be in the process of connecting.
 192          */
 193         if (!dev->driver)
 194                 return 0;
 195
 196         /* Is this search limited to a particular driver? */
 197         if (drv && (dev->driver != drv))
 198                 return 0;
 199
 200         if (ignore_nonessential) {
 201                 /* With older QEMU, for PVonHVM guests the guest config files
 202                  * could contain: vfb = [ 'vnc=1, vnclisten=0.0.0.0']
 203                  * which is nonsensical as there is no PV FB (there can be
 204                  * a PVKB) running as HVM guest. */
 205
 206                 if ((strncmp(xendev->nodename, "device/vkbd", 11) == 0))
 207                         return 0;
 208
 209                 if ((strncmp(xendev->nodename, "device/vfb", 10) == 0))
 210                         return 0;
 211         }
 212         xendrv = to_xenbus_driver(dev->driver);
 213         return (xendev->state < XenbusStateConnected ||
 214                 (xendev->state == XenbusStateConnected &&
 215                  xendrv->is_ready && !xendrv->is_ready(xendev)));
 216 }
 217 static int essential_device_connecting(struct device *dev, void *data)
 218 {
 219         return is_device_connecting(dev, data, true /* ignore PV[KBB+FB] */);
 220 }
 221 static int non_essential_device_connecting(struct device *dev, void *data)
 222 {
 223         return is_device_connecting(dev, data, false);
 224 }
 225
 226 static int exists_essential_connecting_device(struct device_driver *drv)
 227 {
 228         return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
 229                                 essential_device_connecting);
 230 }
 231 static int exists_non_essential_connecting_device(struct device_driver *drv)
 232 {
 233         return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
 234                                 non_essential_device_connecting);
 235 }
 236
 237 static int print_device_status(struct device *dev, void *data)
 238 {
 239         struct xenbus_device *xendev = to_xenbus_device(dev);
 240         struct device_driver *drv = data;
 241
 242         /* Is this operation limited to a particular driver? */
 243         if (drv && (dev->driver != drv))
 244                 return 0;
 245
 246         if (!dev->driver) {
 247                 /* Information only: is this too noisy? */
 248                 pr_info("Device with no driver: %s\n", xendev->nodename);
 249         } else if (xendev->state < XenbusStateConnected) {
 250                 enum xenbus_state rstate = XenbusStateUnknown;
 251                 if (xendev->otherend)
 252                         rstate = xenbus_read_driver_state(xendev->otherend);
 253                 pr_warn("Timeout connecting to device: %s (local state %d, remote state %d)\n",
 254                         xendev->nodename, xendev->state, rstate);
 255         }
 256
 257         return 0;
 258 }
 259
 260 /* We only wait for device setup after most initcalls have run. */
 261 static int ready_to_wait_for_devices;
 262
 263 static bool wait_loop(unsigned long start, unsigned int max_delay,
 264                      unsigned int *seconds_waited)
 265 {
 266         if (time_after(jiffies, start + (*seconds_waited+5)*HZ)) {
 267                 if (!*seconds_waited)
 268                         pr_warn("Waiting for devices to initialise: ");
 269                 *seconds_waited += 5;
 270                 pr_cont("%us...", max_delay - *seconds_waited);
 271                 if (*seconds_waited == max_delay) {
 272                         pr_cont("\n");
 273                         return true;
 274                 }
 275         }
 276
 277         schedule_timeout_interruptible(HZ/10);
 278
 279         return false;
 280 }
 281 /*
 282  * On a 5-minute timeout, wait for all devices currently configured.  We need
 283  * to do this to guarantee that the filesystems and / or network devices
 284  * needed for boot are available, before we can allow the boot to proceed.
 285  *
 286  * This needs to be on a late_initcall, to happen after the frontend device
 287  * drivers have been initialised, but before the root fs is mounted.
 288  *
 289  * A possible improvement here would be to have the tools add a per-device
 290  * flag to the store entry, indicating whether it is needed at boot time.
 291  * This would allow people who knew what they were doing to accelerate their
 292  * boot slightly, but of course needs tools or manual intervention to set up
 293  * those flags correctly.
 294  */
 295 static void wait_for_devices(struct xenbus_driver *xendrv)
 296 {
 297         unsigned long start = jiffies;
 298         struct device_driver *drv = xendrv ? &xendrv->driver : NULL;
 299         unsigned int seconds_waited = 0;
 300
 301         if (!ready_to_wait_for_devices || !xen_domain())
 302                 return;
 303
 304         while (exists_non_essential_connecting_device(drv))
 305                 if (wait_loop(start, 30, &seconds_waited))
 306                         break;
 307
 308         /* Skips PVKB and PVFB check.*/
 309         while (exists_essential_connecting_device(drv))
 310                 if (wait_loop(start, 270, &seconds_waited))
 311                         break;
 312
 313         if (seconds_waited)
 314                 printk("\n");
 315
 316         bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
 317                          print_device_status);
 318 }
 319
 320 int xenbus_register_frontend(struct xenbus_driver *drv)
 321 {
 322         int ret;
 323
 324         drv->read_otherend_details = read_backend_details;
 325
 326         ret = xenbus_register_driver_common(drv, &xenbus_frontend);
 327         if (ret)
 328                 return ret;
 329
 330         /* If this driver is loaded as a module wait for devices to attach. */
 331         wait_for_devices(drv);
 332
 333         return 0;
 334 }
 335 EXPORT_SYMBOL_GPL(xenbus_register_frontend);
 336
 337 static DECLARE_WAIT_QUEUE_HEAD(backend_state_wq);
 338 static int backend_state;
 339
 340 static void xenbus_reset_backend_state_changed(struct xenbus_watch *w,
 341                                         const char **v, unsigned int l)
 342 {
 343         xenbus_scanf(XBT_NIL, v[XS_WATCH_PATH], "", "%i", &backend_state);
 344         printk(KERN_DEBUG "XENBUS: backend %s %s\n",
 345                         v[XS_WATCH_PATH], xenbus_strstate(backend_state));
 346         wake_up(&backend_state_wq);
 347 }
 348
 349 static void xenbus_reset_wait_for_backend(char *be, int expected)
 350 {
 351         long timeout;
 352         timeout = wait_event_interruptible_timeout(backend_state_wq,
 353                         backend_state == expected, 5 * HZ);
 354         if (timeout <= 0)
 355                 pr_info("backend %s timed out\n", be);
 356 }
 357
 358 /*
 359  * Reset frontend if it is in Connected or Closed state.
 360  * Wait for backend to catch up.
 361  * State Connected happens during kdump, Closed after kexec.
 362  */
 363 static void xenbus_reset_frontend(char *fe, char *be, int be_state)
 364 {
 365         struct xenbus_watch be_watch;
 366
 367         printk(KERN_DEBUG "XENBUS: backend %s %s\n",
 368                         be, xenbus_strstate(be_state));
 369
 370         memset(&be_watch, 0, sizeof(be_watch));
 371         be_watch.node = kasprintf(GFP_NOIO | __GFP_HIGH, "%s/state", be);
 372         if (!be_watch.node)
 373                 return;
 374
 375         be_watch.callback = xenbus_reset_backend_state_changed;
 376         backend_state = XenbusStateUnknown;
 377
 378         pr_info("triggering reconnect on %s\n", be);
 379         register_xenbus_watch(&be_watch);
 380
 381         /* fall through to forward backend to state XenbusStateInitialising */
 382         switch (be_state) {
 383         case XenbusStateConnected:
 384                 xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosing);
 385                 xenbus_reset_wait_for_backend(be, XenbusStateClosing);
 386
 387         case XenbusStateClosing:
 388                 xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosed);
 389                 xenbus_reset_wait_for_backend(be, XenbusStateClosed);
 390
 391         case XenbusStateClosed:
 392                 xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateInitialising);
 393                 xenbus_reset_wait_for_backend(be, XenbusStateInitWait);
 394         }
 395
 396         unregister_xenbus_watch(&be_watch);
 397         pr_info("reconnect done on %s\n", be);
 398         kfree(be_watch.node);
 399 }
 400
 401 static void xenbus_check_frontend(char *class, char *dev)
 402 {
 403         int be_state, fe_state, err;
 404         char *backend, *frontend;
 405
 406         frontend = kasprintf(GFP_NOIO | __GFP_HIGH, "device/%s/%s", class, dev);
 407         if (!frontend)
 408                 return;
 409
 410         err = xenbus_scanf(XBT_NIL, frontend, "state", "%i", &fe_state);
 411         if (err != 1)
 412                 goto out;
 413
 414         switch (fe_state) {
 415         case XenbusStateConnected:
 416         case XenbusStateClosed:
 417                 printk(KERN_DEBUG "XENBUS: frontend %s %s\n",
 418                                 frontend, xenbus_strstate(fe_state));
 419                 backend = xenbus_read(XBT_NIL, frontend, "backend", NULL);
 420                 if (!backend || IS_ERR(backend))
 421                         goto out;
 422                 err = xenbus_scanf(XBT_NIL, backend, "state", "%i", &be_state);
 423                 if (err == 1)
 424                         xenbus_reset_frontend(frontend, backend, be_state);
 425                 kfree(backend);
 426                 break;
 427         default:
 428                 break;
 429         }
 430 out:
 431         kfree(frontend);
 432 }
 433
 434 static void xenbus_reset_state(void)
 435 {
 436         char **devclass, **dev;
 437         int devclass_n, dev_n;
 438         int i, j;
 439
 440         devclass = xenbus_directory(XBT_NIL, "device", "", &devclass_n);
 441         if (IS_ERR(devclass))
 442                 return;
 443
 444         for (i = 0; i < devclass_n; i++) {
 445                 dev = xenbus_directory(XBT_NIL, "device", devclass[i], &dev_n);
 446                 if (IS_ERR(dev))
 447                         continue;
 448                 for (j = 0; j < dev_n; j++)
 449                         xenbus_check_frontend(devclass[i], dev[j]);
 450                 kfree(dev);
 451         }
 452         kfree(devclass);
 453 }
 454
 455 static int frontend_probe_and_watch(struct notifier_block *notifier,
 456                                    unsigned long event,
 457                                    void *data)
 458 {
 459         /* reset devices in Connected or Closed state */
 460         if (xen_hvm_domain())
 461                 xenbus_reset_state();
 462         /* Enumerate devices in xenstore and watch for changes. */
 463         xenbus_probe_devices(&xenbus_frontend);
 464         register_xenbus_watch(&fe_watch);
 465
 466         return NOTIFY_DONE;
 467 }
 468
 469
 470 static int __init xenbus_probe_frontend_init(void)
 471 {
 472         static struct notifier_block xenstore_notifier = {
 473                 .notifier_call = frontend_probe_and_watch
 474         };
 475         int err;
 476
 477         DPRINTK("");
 478
 479         /* Register ourselves with the kernel bus subsystem */
 480         err = bus_register(&xenbus_frontend.bus);
 481         if (err)
 482                 return err;
 483
 484         register_xenstore_notifier(&xenstore_notifier);
 485
 486         if (xen_store_domain_type == XS_LOCAL) {
 487                 xenbus_frontend_wq = create_workqueue("xenbus_frontend");
 488                 if (!xenbus_frontend_wq)
 489                         pr_warn("create xenbus frontend workqueue failed, S3 resume is likely to fail\n");
 490         }
 491
 492         return 0;
 493 }
 494 subsys_initcall(xenbus_probe_frontend_init);
 495
 496 #ifndef MODULE
 497 static int __init boot_wait_for_devices(void)
 498 {
 499         if (xen_hvm_domain() && !xen_platform_pci_unplug)
 500                 return -ENODEV;
 501
 502         ready_to_wait_for_devices = 1;
 503         wait_for_devices(NULL);
 504         return 0;
 505 }
 506
 507 late_initcall(boot_wait_for_devices);
 508 #endif
 509
 510 MODULE_LICENSE("GPL");