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_groups     = xenbus_dev_groups,
 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, struct module *owner,
 321                                const char *mod_name)
 322 {
 323         int ret;
 324
 325         drv->read_otherend_details = read_backend_details;
 326
 327         ret = xenbus_register_driver_common(drv, &xenbus_frontend,
 328                                             owner, mod_name);
 329         if (ret)
 330                 return ret;
 331
 332         /* If this driver is loaded as a module wait for devices to attach. */
 333         wait_for_devices(drv);
 334
 335         return 0;
 336 }
 337 EXPORT_SYMBOL_GPL(__xenbus_register_frontend);
 338
 339 static DECLARE_WAIT_QUEUE_HEAD(backend_state_wq);
 340 static int backend_state;
 341
 342 static void xenbus_reset_backend_state_changed(struct xenbus_watch *w,
 343                                         const char **v, unsigned int l)
 344 {
 345         xenbus_scanf(XBT_NIL, v[XS_WATCH_PATH], "", "%i", &backend_state);
 346         printk(KERN_DEBUG "XENBUS: backend %s %s\n",
 347                         v[XS_WATCH_PATH], xenbus_strstate(backend_state));
 348         wake_up(&backend_state_wq);
 349 }
 350
 351 static void xenbus_reset_wait_for_backend(char *be, int expected)
 352 {
 353         long timeout;
 354         timeout = wait_event_interruptible_timeout(backend_state_wq,
 355                         backend_state == expected, 5 * HZ);
 356         if (timeout <= 0)
 357                 pr_info("backend %s timed out\n", be);
 358 }
 359
 360 /*
 361  * Reset frontend if it is in Connected or Closed state.
 362  * Wait for backend to catch up.
 363  * State Connected happens during kdump, Closed after kexec.
 364  */
 365 static void xenbus_reset_frontend(char *fe, char *be, int be_state)
 366 {
 367         struct xenbus_watch be_watch;
 368
 369         printk(KERN_DEBUG "XENBUS: backend %s %s\n",
 370                         be, xenbus_strstate(be_state));
 371
 372         memset(&be_watch, 0, sizeof(be_watch));
 373         be_watch.node = kasprintf(GFP_NOIO | __GFP_HIGH, "%s/state", be);
 374         if (!be_watch.node)
 375                 return;
 376
 377         be_watch.callback = xenbus_reset_backend_state_changed;
 378         backend_state = XenbusStateUnknown;
 379
 380         pr_info("triggering reconnect on %s\n", be);
 381         register_xenbus_watch(&be_watch);
 382
 383         /* fall through to forward backend to state XenbusStateInitialising */
 384         switch (be_state) {
 385         case XenbusStateConnected:
 386                 xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosing);
 387                 xenbus_reset_wait_for_backend(be, XenbusStateClosing);
 388
 389         case XenbusStateClosing:
 390                 xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosed);
 391                 xenbus_reset_wait_for_backend(be, XenbusStateClosed);
 392
 393         case XenbusStateClosed:
 394                 xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateInitialising);
 395                 xenbus_reset_wait_for_backend(be, XenbusStateInitWait);
 396         }
 397
 398         unregister_xenbus_watch(&be_watch);
 399         pr_info("reconnect done on %s\n", be);
 400         kfree(be_watch.node);
 401 }
 402
 403 static void xenbus_check_frontend(char *class, char *dev)
 404 {
 405         int be_state, fe_state, err;
 406         char *backend, *frontend;
 407
 408         frontend = kasprintf(GFP_NOIO | __GFP_HIGH, "device/%s/%s", class, dev);
 409         if (!frontend)
 410                 return;
 411
 412         err = xenbus_scanf(XBT_NIL, frontend, "state", "%i", &fe_state);
 413         if (err != 1)
 414                 goto out;
 415
 416         switch (fe_state) {
 417         case XenbusStateConnected:
 418         case XenbusStateClosed:
 419                 printk(KERN_DEBUG "XENBUS: frontend %s %s\n",
 420                                 frontend, xenbus_strstate(fe_state));
 421                 backend = xenbus_read(XBT_NIL, frontend, "backend", NULL);
 422                 if (!backend || IS_ERR(backend))
 423                         goto out;
 424                 err = xenbus_scanf(XBT_NIL, backend, "state", "%i", &be_state);
 425                 if (err == 1)
 426                         xenbus_reset_frontend(frontend, backend, be_state);
 427                 kfree(backend);
 428                 break;
 429         default:
 430                 break;
 431         }
 432 out:
 433         kfree(frontend);
 434 }
 435
 436 static void xenbus_reset_state(void)
 437 {
 438         char **devclass, **dev;
 439         int devclass_n, dev_n;
 440         int i, j;
 441
 442         devclass = xenbus_directory(XBT_NIL, "device", "", &devclass_n);
 443         if (IS_ERR(devclass))
 444                 return;
 445
 446         for (i = 0; i < devclass_n; i++) {
 447                 dev = xenbus_directory(XBT_NIL, "device", devclass[i], &dev_n);
 448                 if (IS_ERR(dev))
 449                         continue;
 450                 for (j = 0; j < dev_n; j++)
 451                         xenbus_check_frontend(devclass[i], dev[j]);
 452                 kfree(dev);
 453         }
 454         kfree(devclass);
 455 }
 456
 457 static int frontend_probe_and_watch(struct notifier_block *notifier,
 458                                    unsigned long event,
 459                                    void *data)
 460 {
 461         /* reset devices in Connected or Closed state */
 462         if (xen_hvm_domain())
 463                 xenbus_reset_state();
 464         /* Enumerate devices in xenstore and watch for changes. */
 465         xenbus_probe_devices(&xenbus_frontend);
 466         register_xenbus_watch(&fe_watch);
 467
 468         return NOTIFY_DONE;
 469 }
 470
 471
 472 static int __init xenbus_probe_frontend_init(void)
 473 {
 474         static struct notifier_block xenstore_notifier = {
 475                 .notifier_call = frontend_probe_and_watch
 476         };
 477         int err;
 478
 479         DPRINTK("");
 480
 481         /* Register ourselves with the kernel bus subsystem */
 482         err = bus_register(&xenbus_frontend.bus);
 483         if (err)
 484                 return err;
 485
 486         register_xenstore_notifier(&xenstore_notifier);
 487
 488         if (xen_store_domain_type == XS_LOCAL) {
 489                 xenbus_frontend_wq = create_workqueue("xenbus_frontend");
 490                 if (!xenbus_frontend_wq)
 491                         pr_warn("create xenbus frontend workqueue failed, S3 resume is likely to fail\n");
 492         }
 493
 494         return 0;
 495 }
 496 subsys_initcall(xenbus_probe_frontend_init);
 497
 498 #ifndef MODULE
 499 static int __init boot_wait_for_devices(void)
 500 {
 501         if (!xen_has_pv_devices())
 502                 return -ENODEV;
 503
 504         ready_to_wait_for_devices = 1;
 505         wait_for_devices(NULL);
 506         return 0;
 507 }
 508
 509 late_initcall(boot_wait_for_devices);
 510 #endif
 511
 512 MODULE_LICENSE("GPL");