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 #include <xen/xen.h>
  25
  26 #include <xen/platform_pci.h>
  27
  28 #include "xenbus_comms.h"
  29 #include "xenbus_probe.h"
  30
  31
  32 static struct workqueue_struct *xenbus_frontend_wq;
  33
  34 /* device/<type>/<id> => <type>-<id> */
  35 static int frontend_bus_id(char bus_id[XEN_BUS_ID_SIZE], const char *nodename)
  36 {
  37         nodename = strchr(nodename, '/');
  38         if (!nodename || strlen(nodename + 1) >= XEN_BUS_ID_SIZE) {
  39                 printk(KERN_WARNING "XENBUS: bad frontend %s\n", nodename);
  40                 return -EINVAL;
  41         }
  42
  43         strlcpy(bus_id, nodename + 1, XEN_BUS_ID_SIZE);
  44         if (!strchr(bus_id, '/')) {
  45                 printk(KERN_WARNING "XENBUS: bus_id %s no slash\n", bus_id);
  46                 return -EINVAL;
  47         }
  48         *strchr(bus_id, '/') = '-';
  49         return 0;
  50 }
  51
  52 /* device/<typename>/<name> */
  53 static int xenbus_probe_frontend(struct xen_bus_type *bus, const char *type,
  54                                  const char *name)
  55 {
  56         char *nodename;
  57         int err;
  58
  59         /* ignore console/0 */
  60         if (!strncmp(type, "console", 7) && !strncmp(name, "0", 1)) {
  61                 DPRINTK("Ignoring buggy device entry console/0");
  62                 return 0;
  63         }
  64
  65         nodename = kasprintf(GFP_KERNEL, "%s/%s/%s", bus->root, type, name);
  66         if (!nodename)
  67                 return -ENOMEM;
  68
  69         DPRINTK("%s", nodename);
  70
  71         err = xenbus_probe_node(bus, type, nodename);
  72         kfree(nodename);
  73         return err;
  74 }
  75
  76 static int xenbus_uevent_frontend(struct device *_dev,
  77                                   struct kobj_uevent_env *env)
  78 {
  79         struct xenbus_device *dev = to_xenbus_device(_dev);
  80
  81         if (add_uevent_var(env, "MODALIAS=xen:%s", dev->devicetype))
  82                 return -ENOMEM;
  83
  84         return 0;
  85 }
  86
  87
  88 static void backend_changed(struct xenbus_watch *watch,
  89                             const char **vec, unsigned int len)
  90 {
  91         xenbus_otherend_changed(watch, vec, len, 1);
  92 }
  93
  94 static void xenbus_frontend_delayed_resume(struct work_struct *w)
  95 {
  96         struct xenbus_device *xdev = container_of(w, struct xenbus_device, work);
  97
  98         xenbus_dev_resume(&xdev->dev);
  99 }
 100
 101 static int xenbus_frontend_dev_resume(struct device *dev)
 102 {
 103         /*
 104          * If xenstored is running in this domain, we cannot access the backend
 105          * state at the moment, so we need to defer xenbus_dev_resume
 106          */
 107         if (xen_store_domain_type == XS_LOCAL) {
 108                 struct xenbus_device *xdev = to_xenbus_device(dev);
 109
 110                 if (!xenbus_frontend_wq) {
 111                         pr_err("%s: no workqueue to process delayed resume\n",
 112                                xdev->nodename);
 113                         return -EFAULT;
 114                 }
 115
 116                 INIT_WORK(&xdev->work, xenbus_frontend_delayed_resume);
 117                 queue_work(xenbus_frontend_wq, &xdev->work);
 118
 119                 return 0;
 120         }
 121
 122         return xenbus_dev_resume(dev);
 123 }
 124
 125 static const struct dev_pm_ops xenbus_pm_ops = {
 126         .suspend        = xenbus_dev_suspend,
 127         .resume         = xenbus_frontend_dev_resume,
 128         .freeze         = xenbus_dev_suspend,
 129         .thaw           = xenbus_dev_cancel,
 130         .restore        = xenbus_dev_resume,
 131 };
 132
 133 static struct xen_bus_type xenbus_frontend = {
 134         .root = "device",
 135         .levels = 2,            /* device/type/<id> */
 136         .get_bus_id = frontend_bus_id,
 137         .probe = xenbus_probe_frontend,
 138         .otherend_changed = backend_changed,
 139         .bus = {
 140                 .name           = "xen",
 141                 .match          = xenbus_match,
 142                 .uevent         = xenbus_uevent_frontend,
 143                 .probe          = xenbus_dev_probe,
 144                 .remove         = xenbus_dev_remove,
 145                 .shutdown       = xenbus_dev_shutdown,
 146                 .dev_attrs      = xenbus_dev_attrs,
 147
 148                 .pm             = &xenbus_pm_ops,
 149         },
 150 };
 151
 152 static void frontend_changed(struct xenbus_watch *watch,
 153                              const char **vec, unsigned int len)
 154 {
 155         DPRINTK("");
 156
 157         xenbus_dev_changed(vec[XS_WATCH_PATH], &xenbus_frontend);
 158 }
 159
 160
 161 /* We watch for devices appearing and vanishing. */
 162 static struct xenbus_watch fe_watch = {
 163         .node = "device",
 164         .callback = frontend_changed,
 165 };
 166
 167 static int read_backend_details(struct xenbus_device *xendev)
 168 {
 169         return xenbus_read_otherend_details(xendev, "backend-id", "backend");
 170 }
 171
 172 static int is_device_connecting(struct device *dev, void *data, bool ignore_nonessential)
 173 {
 174         struct xenbus_device *xendev = to_xenbus_device(dev);
 175         struct device_driver *drv = data;
 176         struct xenbus_driver *xendrv;
 177
 178         /*
 179          * A device with no driver will never connect. We care only about
 180          * devices which should currently be in the process of connecting.
 181          */
 182         if (!dev->driver)
 183                 return 0;
 184
 185         /* Is this search limited to a particular driver? */
 186         if (drv && (dev->driver != drv))
 187                 return 0;
 188
 189         if (ignore_nonessential) {
 190                 /* With older QEMU, for PVonHVM guests the guest config files
 191                  * could contain: vfb = [ 'vnc=1, vnclisten=0.0.0.0']
 192                  * which is nonsensical as there is no PV FB (there can be
 193                  * a PVKB) running as HVM guest. */
 194
 195                 if ((strncmp(xendev->nodename, "device/vkbd", 11) == 0))
 196                         return 0;
 197
 198                 if ((strncmp(xendev->nodename, "device/vfb", 10) == 0))
 199                         return 0;
 200         }
 201         xendrv = to_xenbus_driver(dev->driver);
 202         return (xendev->state < XenbusStateConnected ||
 203                 (xendev->state == XenbusStateConnected &&
 204                  xendrv->is_ready && !xendrv->is_ready(xendev)));
 205 }
 206 static int essential_device_connecting(struct device *dev, void *data)
 207 {
 208         return is_device_connecting(dev, data, true /* ignore PV[KBB+FB] */);
 209 }
 210 static int non_essential_device_connecting(struct device *dev, void *data)
 211 {
 212         return is_device_connecting(dev, data, false);
 213 }
 214
 215 static int exists_essential_connecting_device(struct device_driver *drv)
 216 {
 217         return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
 218                                 essential_device_connecting);
 219 }
 220 static int exists_non_essential_connecting_device(struct device_driver *drv)
 221 {
 222         return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
 223                                 non_essential_device_connecting);
 224 }
 225
 226 static int print_device_status(struct device *dev, void *data)
 227 {
 228         struct xenbus_device *xendev = to_xenbus_device(dev);
 229         struct device_driver *drv = data;
 230
 231         /* Is this operation limited to a particular driver? */
 232         if (drv && (dev->driver != drv))
 233                 return 0;
 234
 235         if (!dev->driver) {
 236                 /* Information only: is this too noisy? */
 237                 printk(KERN_INFO "XENBUS: Device with no driver: %s\n",
 238                        xendev->nodename);
 239         } else if (xendev->state < XenbusStateConnected) {
 240                 enum xenbus_state rstate = XenbusStateUnknown;
 241                 if (xendev->otherend)
 242                         rstate = xenbus_read_driver_state(xendev->otherend);
 243                 printk(KERN_WARNING "XENBUS: Timeout connecting "
 244                        "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                         printk(KERN_WARNING "XENBUS: Waiting for "
 260                                "devices to initialise: ");
 261                 *seconds_waited += 5;
 262                 printk("%us...", max_delay - *seconds_waited);
 263                 if (*seconds_waited == max_delay)
 264                         return true;
 265         }
 266
 267         schedule_timeout_interruptible(HZ/10);
 268
 269         return false;
 270 }
 271 /*
 272  * On a 5-minute timeout, wait for all devices currently configured.  We need
 273  * to do this to guarantee that the filesystems and / or network devices
 274  * needed for boot are available, before we can allow the boot to proceed.
 275  *
 276  * This needs to be on a late_initcall, to happen after the frontend device
 277  * drivers have been initialised, but before the root fs is mounted.
 278  *
 279  * A possible improvement here would be to have the tools add a per-device
 280  * flag to the store entry, indicating whether it is needed at boot time.
 281  * This would allow people who knew what they were doing to accelerate their
 282  * boot slightly, but of course needs tools or manual intervention to set up
 283  * those flags correctly.
 284  */
 285 static void wait_for_devices(struct xenbus_driver *xendrv)
 286 {
 287         unsigned long start = jiffies;
 288         struct device_driver *drv = xendrv ? &xendrv->driver : NULL;
 289         unsigned int seconds_waited = 0;
 290
 291         if (!ready_to_wait_for_devices || !xen_domain())
 292                 return;
 293
 294         while (exists_non_essential_connecting_device(drv))
 295                 if (wait_loop(start, 30, &seconds_waited))
 296                         break;
 297
 298         /* Skips PVKB and PVFB check.*/
 299         while (exists_essential_connecting_device(drv))
 300                 if (wait_loop(start, 270, &seconds_waited))
 301                         break;
 302
 303         if (seconds_waited)
 304                 printk("\n");
 305
 306         bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
 307                          print_device_status);
 308 }
 309
 310 int xenbus_register_frontend(struct xenbus_driver *drv)
 311 {
 312         int ret;
 313
 314         drv->read_otherend_details = read_backend_details;
 315
 316         ret = xenbus_register_driver_common(drv, &xenbus_frontend);
 317         if (ret)
 318                 return ret;
 319
 320         /* If this driver is loaded as a module wait for devices to attach. */
 321         wait_for_devices(drv);
 322
 323         return 0;
 324 }
 325 EXPORT_SYMBOL_GPL(xenbus_register_frontend);
 326
 327 static DECLARE_WAIT_QUEUE_HEAD(backend_state_wq);
 328 static int backend_state;
 329
 330 static void xenbus_reset_backend_state_changed(struct xenbus_watch *w,
 331                                         const char **v, unsigned int l)
 332 {
 333         xenbus_scanf(XBT_NIL, v[XS_WATCH_PATH], "", "%i", &backend_state);
 334         printk(KERN_DEBUG "XENBUS: backend %s %s\n",
 335                         v[XS_WATCH_PATH], xenbus_strstate(backend_state));
 336         wake_up(&backend_state_wq);
 337 }
 338
 339 static void xenbus_reset_wait_for_backend(char *be, int expected)
 340 {
 341         long timeout;
 342         timeout = wait_event_interruptible_timeout(backend_state_wq,
 343                         backend_state == expected, 5 * HZ);
 344         if (timeout <= 0)
 345                 printk(KERN_INFO "XENBUS: backend %s timed out.\n", be);
 346 }
 347
 348 /*
 349  * Reset frontend if it is in Connected or Closed state.
 350  * Wait for backend to catch up.
 351  * State Connected happens during kdump, Closed after kexec.
 352  */
 353 static void xenbus_reset_frontend(char *fe, char *be, int be_state)
 354 {
 355         struct xenbus_watch be_watch;
 356
 357         printk(KERN_DEBUG "XENBUS: backend %s %s\n",
 358                         be, xenbus_strstate(be_state));
 359
 360         memset(&be_watch, 0, sizeof(be_watch));
 361         be_watch.node = kasprintf(GFP_NOIO | __GFP_HIGH, "%s/state", be);
 362         if (!be_watch.node)
 363                 return;
 364
 365         be_watch.callback = xenbus_reset_backend_state_changed;
 366         backend_state = XenbusStateUnknown;
 367
 368         printk(KERN_INFO "XENBUS: triggering reconnect on %s\n", be);
 369         register_xenbus_watch(&be_watch);
 370
 371         /* fall through to forward backend to state XenbusStateInitialising */
 372         switch (be_state) {
 373         case XenbusStateConnected:
 374                 xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosing);
 375                 xenbus_reset_wait_for_backend(be, XenbusStateClosing);
 376
 377         case XenbusStateClosing:
 378                 xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateClosed);
 379                 xenbus_reset_wait_for_backend(be, XenbusStateClosed);
 380
 381         case XenbusStateClosed:
 382                 xenbus_printf(XBT_NIL, fe, "state", "%d", XenbusStateInitialising);
 383                 xenbus_reset_wait_for_backend(be, XenbusStateInitWait);
 384         }
 385
 386         unregister_xenbus_watch(&be_watch);
 387         printk(KERN_INFO "XENBUS: reconnect done on %s\n", be);
 388         kfree(be_watch.node);
 389 }
 390
 391 static void xenbus_check_frontend(char *class, char *dev)
 392 {
 393         int be_state, fe_state, err;
 394         char *backend, *frontend;
 395
 396         frontend = kasprintf(GFP_NOIO | __GFP_HIGH, "device/%s/%s", class, dev);
 397         if (!frontend)
 398                 return;
 399
 400         err = xenbus_scanf(XBT_NIL, frontend, "state", "%i", &fe_state);
 401         if (err != 1)
 402                 goto out;
 403
 404         switch (fe_state) {
 405         case XenbusStateConnected:
 406         case XenbusStateClosed:
 407                 printk(KERN_DEBUG "XENBUS: frontend %s %s\n",
 408                                 frontend, xenbus_strstate(fe_state));
 409                 backend = xenbus_read(XBT_NIL, frontend, "backend", NULL);
 410                 if (!backend || IS_ERR(backend))
 411                         goto out;
 412                 err = xenbus_scanf(XBT_NIL, backend, "state", "%i", &be_state);
 413                 if (err == 1)
 414                         xenbus_reset_frontend(frontend, backend, be_state);
 415                 kfree(backend);
 416                 break;
 417         default:
 418                 break;
 419         }
 420 out:
 421         kfree(frontend);
 422 }
 423
 424 static void xenbus_reset_state(void)
 425 {
 426         char **devclass, **dev;
 427         int devclass_n, dev_n;
 428         int i, j;
 429
 430         devclass = xenbus_directory(XBT_NIL, "device", "", &devclass_n);
 431         if (IS_ERR(devclass))
 432                 return;
 433
 434         for (i = 0; i < devclass_n; i++) {
 435                 dev = xenbus_directory(XBT_NIL, "device", devclass[i], &dev_n);
 436                 if (IS_ERR(dev))
 437                         continue;
 438                 for (j = 0; j < dev_n; j++)
 439                         xenbus_check_frontend(devclass[i], dev[j]);
 440                 kfree(dev);
 441         }
 442         kfree(devclass);
 443 }
 444
 445 static int frontend_probe_and_watch(struct notifier_block *notifier,
 446                                    unsigned long event,
 447                                    void *data)
 448 {
 449         /* reset devices in Connected or Closed state */
 450         if (xen_hvm_domain())
 451                 xenbus_reset_state();
 452         /* Enumerate devices in xenstore and watch for changes. */
 453         xenbus_probe_devices(&xenbus_frontend);
 454         register_xenbus_watch(&fe_watch);
 455
 456         return NOTIFY_DONE;
 457 }
 458
 459
 460 static int __init xenbus_probe_frontend_init(void)
 461 {
 462         static struct notifier_block xenstore_notifier = {
 463                 .notifier_call = frontend_probe_and_watch
 464         };
 465         int err;
 466
 467         DPRINTK("");
 468
 469         /* Register ourselves with the kernel bus subsystem */
 470         err = bus_register(&xenbus_frontend.bus);
 471         if (err)
 472                 return err;
 473
 474         register_xenstore_notifier(&xenstore_notifier);
 475
 476         xenbus_frontend_wq = create_workqueue("xenbus_frontend");
 477
 478         return 0;
 479 }
 480 subsys_initcall(xenbus_probe_frontend_init);
 481
 482 #ifndef MODULE
 483 static int __init boot_wait_for_devices(void)
 484 {
 485         if (xen_hvm_domain() && !xen_platform_pci_unplug)
 486                 return -ENODEV;
 487
 488         ready_to_wait_for_devices = 1;
 489         wait_for_devices(NULL);
 490         return 0;
 491 }
 492
 493 late_initcall(boot_wait_for_devices);
 494 #endif
 495
 496 MODULE_LICENSE("GPL");