drivers/xen/xenbus/xenbus_client.c

   1 /******************************************************************************
   2  * Client-facing interface for the Xenbus driver.  In other words, the
   3  * interface between the Xenbus and the device-specific code, be it the
   4  * frontend or the backend of that driver.
   5  *
   6  * Copyright (C) 2005 XenSource Ltd
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License version 2
  10  * as published by the Free Software Foundation; or, when distributed
  11  * separately from the Linux kernel or incorporated into other
  12  * software packages, subject to the following license:
  13  *
  14  * Permission is hereby granted, free of charge, to any person obtaining a copy
  15  * of this source file (the "Software"), to deal in the Software without
  16  * restriction, including without limitation the rights to use, copy, modify,
  17  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
  18  * and to permit persons to whom the Software is furnished to do so, subject to
  19  * the following conditions:
  20  *
  21  * The above copyright notice and this permission notice shall be included in
  22  * all copies or substantial portions of the Software.
  23  *
  24  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  25  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  26  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  27  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  28  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  29  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  30  * IN THE SOFTWARE.
  31  */
  32
  33 #include <linux/mm.h>
  34 #include <linux/slab.h>
  35 #include <linux/types.h>
  36 #include <linux/spinlock.h>
  37 #include <linux/vmalloc.h>
  38 #include <linux/export.h>
  39 #include <asm/xen/hypervisor.h>
  40 #include <asm/xen/page.h>
  41 #include <xen/interface/xen.h>
  42 #include <xen/interface/event_channel.h>
  43 #include <xen/balloon.h>
  44 #include <xen/events.h>
  45 #include <xen/grant_table.h>
  46 #include <xen/xenbus.h>
  47 #include <xen/xen.h>
  48
  49 #include "xenbus_probe.h"
  50
  51 struct xenbus_map_node {
  52         struct list_head next;
  53         union {
  54                 struct vm_struct *area; /* PV */
  55                 struct page *page;     /* HVM */
  56         };
  57         grant_handle_t handle;
  58 };
  59
  60 static DEFINE_SPINLOCK(xenbus_valloc_lock);
  61 static LIST_HEAD(xenbus_valloc_pages);
  62
  63 struct xenbus_ring_ops {
  64         int (*map)(struct xenbus_device *dev, int gnt, void **vaddr);
  65         int (*unmap)(struct xenbus_device *dev, void *vaddr);
  66 };
  67
  68 static const struct xenbus_ring_ops *ring_ops __read_mostly;
  69
  70 const char *xenbus_strstate(enum xenbus_state state)
  71 {
  72         static const char *const name[] = {
  73                 [ XenbusStateUnknown      ] = "Unknown",
  74                 [ XenbusStateInitialising ] = "Initialising",
  75                 [ XenbusStateInitWait     ] = "InitWait",
  76                 [ XenbusStateInitialised  ] = "Initialised",
  77                 [ XenbusStateConnected    ] = "Connected",
  78                 [ XenbusStateClosing      ] = "Closing",
  79                 [ XenbusStateClosed       ] = "Closed",
  80                 [XenbusStateReconfiguring] = "Reconfiguring",
  81                 [XenbusStateReconfigured] = "Reconfigured",
  82         };
  83         return (state < ARRAY_SIZE(name)) ? name[state] : "INVALID";
  84 }
  85 EXPORT_SYMBOL_GPL(xenbus_strstate);
  86
  87 /**
  88  * xenbus_watch_path - register a watch
  89  * @dev: xenbus device
  90  * @path: path to watch
  91  * @watch: watch to register
  92  * @callback: callback to register
  93  *
  94  * Register a @watch on the given path, using the given xenbus_watch structure
  95  * for storage, and the given @callback function as the callback.  Return 0 on
  96  * success, or -errno on error.  On success, the given @path will be saved as
  97  * @watch->node, and remains the caller's to free.  On error, @watch->node will
  98  * be NULL, the device will switch to %XenbusStateClosing, and the error will
  99  * be saved in the store.
 100  */
 101 int xenbus_watch_path(struct xenbus_device *dev, const char *path,
 102                       struct xenbus_watch *watch,
 103                       void (*callback)(struct xenbus_watch *,
 104                                        const char **, unsigned int))
 105 {
 106         int err;
 107
 108         watch->node = path;
 109         watch->callback = callback;
 110
 111         err = register_xenbus_watch(watch);
 112
 113         if (err) {
 114                 watch->node = NULL;
 115                 watch->callback = NULL;
 116                 xenbus_dev_fatal(dev, err, "adding watch on %s", path);
 117         }
 118
 119         return err;
 120 }
 121 EXPORT_SYMBOL_GPL(xenbus_watch_path);
 122
 123
 124 /**
 125  * xenbus_watch_pathfmt - register a watch on a sprintf-formatted path
 126  * @dev: xenbus device
 127  * @watch: watch to register
 128  * @callback: callback to register
 129  * @pathfmt: format of path to watch
 130  *
 131  * Register a watch on the given @path, using the given xenbus_watch
 132  * structure for storage, and the given @callback function as the callback.
 133  * Return 0 on success, or -errno on error.  On success, the watched path
 134  * (@path/@path2) will be saved as @watch->node, and becomes the caller's to
 135  * kfree().  On error, watch->node will be NULL, so the caller has nothing to
 136  * free, the device will switch to %XenbusStateClosing, and the error will be
 137  * saved in the store.
 138  */
 139 int xenbus_watch_pathfmt(struct xenbus_device *dev,
 140                          struct xenbus_watch *watch,
 141                          void (*callback)(struct xenbus_watch *,
 142                                         const char **, unsigned int),
 143                          const char *pathfmt, ...)
 144 {
 145         int err;
 146         va_list ap;
 147         char *path;
 148
 149         va_start(ap, pathfmt);
 150         path = kvasprintf(GFP_NOIO | __GFP_HIGH, pathfmt, ap);
 151         va_end(ap);
 152
 153         if (!path) {
 154                 xenbus_dev_fatal(dev, -ENOMEM, "allocating path for watch");
 155                 return -ENOMEM;
 156         }
 157         err = xenbus_watch_path(dev, path, watch, callback);
 158
 159         if (err)
 160                 kfree(path);
 161         return err;
 162 }
 163 EXPORT_SYMBOL_GPL(xenbus_watch_pathfmt);
 164
 165 static void xenbus_switch_fatal(struct xenbus_device *, int, int,
 166                                 const char *, ...);
 167
 168 static int
 169 __xenbus_switch_state(struct xenbus_device *dev,
 170                       enum xenbus_state state, int depth)
 171 {
 172         /* We check whether the state is currently set to the given value, and
 173            if not, then the state is set.  We don't want to unconditionally
 174            write the given state, because we don't want to fire watches
 175            unnecessarily.  Furthermore, if the node has gone, we don't write
 176            to it, as the device will be tearing down, and we don't want to
 177            resurrect that directory.
 178
 179            Note that, because of this cached value of our state, this
 180            function will not take a caller's Xenstore transaction
 181            (something it was trying to in the past) because dev->state
 182            would not get reset if the transaction was aborted.
 183          */
 184
 185         struct xenbus_transaction xbt;
 186         int current_state;
 187         int err, abort;
 188
 189         if (state == dev->state)
 190                 return 0;
 191
 192 again:
 193         abort = 1;
 194
 195         err = xenbus_transaction_start(&xbt);
 196         if (err) {
 197                 xenbus_switch_fatal(dev, depth, err, "starting transaction");
 198                 return 0;
 199         }
 200
 201         err = xenbus_scanf(xbt, dev->nodename, "state", "%d", &current_state);
 202         if (err != 1)
 203                 goto abort;
 204
 205         err = xenbus_printf(xbt, dev->nodename, "state", "%d", state);
 206         if (err) {
 207                 xenbus_switch_fatal(dev, depth, err, "writing new state");
 208                 goto abort;
 209         }
 210
 211         abort = 0;
 212 abort:
 213         err = xenbus_transaction_end(xbt, abort);
 214         if (err) {
 215                 if (err == -EAGAIN && !abort)
 216                         goto again;
 217                 xenbus_switch_fatal(dev, depth, err, "ending transaction");
 218         } else
 219                 dev->state = state;
 220
 221         return 0;
 222 }
 223
 224 /**
 225  * xenbus_switch_state
 226  * @dev: xenbus device
 227  * @state: new state
 228  *
 229  * Advertise in the store a change of the given driver to the given new_state.
 230  * Return 0 on success, or -errno on error.  On error, the device will switch
 231  * to XenbusStateClosing, and the error will be saved in the store.
 232  */
 233 int xenbus_switch_state(struct xenbus_device *dev, enum xenbus_state state)
 234 {
 235         return __xenbus_switch_state(dev, state, 0);
 236 }
 237
 238 EXPORT_SYMBOL_GPL(xenbus_switch_state);
 239
 240 int xenbus_frontend_closed(struct xenbus_device *dev)
 241 {
 242         xenbus_switch_state(dev, XenbusStateClosed);
 243         complete(&dev->down);
 244         return 0;
 245 }
 246 EXPORT_SYMBOL_GPL(xenbus_frontend_closed);
 247
 248 /**
 249  * Return the path to the error node for the given device, or NULL on failure.
 250  * If the value returned is non-NULL, then it is the caller's to kfree.
 251  */
 252 static char *error_path(struct xenbus_device *dev)
 253 {
 254         return kasprintf(GFP_KERNEL, "error/%s", dev->nodename);
 255 }
 256
 257
 258 static void xenbus_va_dev_error(struct xenbus_device *dev, int err,
 259                                 const char *fmt, va_list ap)
 260 {
 261         int ret;
 262         unsigned int len;
 263         char *printf_buffer = NULL;
 264         char *path_buffer = NULL;
 265
 266 #define PRINTF_BUFFER_SIZE 4096
 267         printf_buffer = kmalloc(PRINTF_BUFFER_SIZE, GFP_KERNEL);
 268         if (printf_buffer == NULL)
 269                 goto fail;
 270
 271         len = sprintf(printf_buffer, "%i ", -err);
 272         ret = vsnprintf(printf_buffer+len, PRINTF_BUFFER_SIZE-len, fmt, ap);
 273
 274         BUG_ON(len + ret > PRINTF_BUFFER_SIZE-1);
 275
 276         dev_err(&dev->dev, "%s\n", printf_buffer);
 277
 278         path_buffer = error_path(dev);
 279
 280         if (path_buffer == NULL) {
 281                 dev_err(&dev->dev, "failed to write error node for %s (%s)\n",
 282                        dev->nodename, printf_buffer);
 283                 goto fail;
 284         }
 285
 286         if (xenbus_write(XBT_NIL, path_buffer, "error", printf_buffer) != 0) {
 287                 dev_err(&dev->dev, "failed to write error node for %s (%s)\n",
 288                        dev->nodename, printf_buffer);
 289                 goto fail;
 290         }
 291
 292 fail:
 293         kfree(printf_buffer);
 294         kfree(path_buffer);
 295 }
 296
 297
 298 /**
 299  * xenbus_dev_error
 300  * @dev: xenbus device
 301  * @err: error to report
 302  * @fmt: error message format
 303  *
 304  * Report the given negative errno into the store, along with the given
 305  * formatted message.
 306  */
 307 void xenbus_dev_error(struct xenbus_device *dev, int err, const char *fmt, ...)
 308 {
 309         va_list ap;
 310
 311         va_start(ap, fmt);
 312         xenbus_va_dev_error(dev, err, fmt, ap);
 313         va_end(ap);
 314 }
 315 EXPORT_SYMBOL_GPL(xenbus_dev_error);
 316
 317 /**
 318  * xenbus_dev_fatal
 319  * @dev: xenbus device
 320  * @err: error to report
 321  * @fmt: error message format
 322  *
 323  * Equivalent to xenbus_dev_error(dev, err, fmt, args), followed by
 324  * xenbus_switch_state(dev, XenbusStateClosing) to schedule an orderly
 325  * closedown of this driver and its peer.
 326  */
 327
 328 void xenbus_dev_fatal(struct xenbus_device *dev, int err, const char *fmt, ...)
 329 {
 330         va_list ap;
 331
 332         va_start(ap, fmt);
 333         xenbus_va_dev_error(dev, err, fmt, ap);
 334         va_end(ap);
 335
 336         xenbus_switch_state(dev, XenbusStateClosing);
 337 }
 338 EXPORT_SYMBOL_GPL(xenbus_dev_fatal);
 339
 340 /**
 341  * Equivalent to xenbus_dev_fatal(dev, err, fmt, args), but helps
 342  * avoiding recursion within xenbus_switch_state.
 343  */
 344 static void xenbus_switch_fatal(struct xenbus_device *dev, int depth, int err,
 345                                 const char *fmt, ...)
 346 {
 347         va_list ap;
 348
 349         va_start(ap, fmt);
 350         xenbus_va_dev_error(dev, err, fmt, ap);
 351         va_end(ap);
 352
 353         if (!depth)
 354                 __xenbus_switch_state(dev, XenbusStateClosing, 1);
 355 }
 356
 357 /**
 358  * xenbus_grant_ring
 359  * @dev: xenbus device
 360  * @ring_mfn: mfn of ring to grant
 361
 362  * Grant access to the given @ring_mfn to the peer of the given device.  Return
 363  * 0 on success, or -errno on error.  On error, the device will switch to
 364  * XenbusStateClosing, and the error will be saved in the store.
 365  */
 366 int xenbus_grant_ring(struct xenbus_device *dev, unsigned long ring_mfn)
 367 {
 368         int err = gnttab_grant_foreign_access(dev->otherend_id, ring_mfn, 0);
 369         if (err < 0)
 370                 xenbus_dev_fatal(dev, err, "granting access to ring page");
 371         return err;
 372 }
 373 EXPORT_SYMBOL_GPL(xenbus_grant_ring);
 374
 375
 376 /**
 377  * Allocate an event channel for the given xenbus_device, assigning the newly
 378  * created local port to *port.  Return 0 on success, or -errno on error.  On
 379  * error, the device will switch to XenbusStateClosing, and the error will be
 380  * saved in the store.
 381  */
 382 int xenbus_alloc_evtchn(struct xenbus_device *dev, int *port)
 383 {
 384         struct evtchn_alloc_unbound alloc_unbound;
 385         int err;
 386
 387         alloc_unbound.dom = DOMID_SELF;
 388         alloc_unbound.remote_dom = dev->otherend_id;
 389
 390         err = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound,
 391                                           &alloc_unbound);
 392         if (err)
 393                 xenbus_dev_fatal(dev, err, "allocating event channel");
 394         else
 395                 *port = alloc_unbound.port;
 396
 397         return err;
 398 }
 399 EXPORT_SYMBOL_GPL(xenbus_alloc_evtchn);
 400
 401
 402 /**
 403  * Bind to an existing interdomain event channel in another domain. Returns 0
 404  * on success and stores the local port in *port. On error, returns -errno,
 405  * switches the device to XenbusStateClosing, and saves the error in XenStore.
 406  */
 407 int xenbus_bind_evtchn(struct xenbus_device *dev, int remote_port, int *port)
 408 {
 409         struct evtchn_bind_interdomain bind_interdomain;
 410         int err;
 411
 412         bind_interdomain.remote_dom = dev->otherend_id;
 413         bind_interdomain.remote_port = remote_port;
 414
 415         err = HYPERVISOR_event_channel_op(EVTCHNOP_bind_interdomain,
 416                                           &bind_interdomain);
 417         if (err)
 418                 xenbus_dev_fatal(dev, err,
 419                                  "binding to event channel %d from domain %d",
 420                                  remote_port, dev->otherend_id);
 421         else
 422                 *port = bind_interdomain.local_port;
 423
 424         return err;
 425 }
 426 EXPORT_SYMBOL_GPL(xenbus_bind_evtchn);
 427
 428
 429 /**
 430  * Free an existing event channel. Returns 0 on success or -errno on error.
 431  */
 432 int xenbus_free_evtchn(struct xenbus_device *dev, int port)
 433 {
 434         struct evtchn_close close;
 435         int err;
 436
 437         close.port = port;
 438
 439         err = HYPERVISOR_event_channel_op(EVTCHNOP_close, &close);
 440         if (err)
 441                 xenbus_dev_error(dev, err, "freeing event channel %d", port);
 442
 443         return err;
 444 }
 445 EXPORT_SYMBOL_GPL(xenbus_free_evtchn);
 446
 447
 448 /**
 449  * xenbus_map_ring_valloc
 450  * @dev: xenbus device
 451  * @gnt_ref: grant reference
 452  * @vaddr: pointer to address to be filled out by mapping
 453  *
 454  * Based on Rusty Russell's skeleton driver's map_page.
 455  * Map a page of memory into this domain from another domain's grant table.
 456  * xenbus_map_ring_valloc allocates a page of virtual address space, maps the
 457  * page to that address, and sets *vaddr to that address.
 458  * Returns 0 on success, and GNTST_* (see xen/include/interface/grant_table.h)
 459  * or -ENOMEM on error. If an error is returned, device will switch to
 460  * XenbusStateClosing and the error message will be saved in XenStore.
 461  */
 462 int xenbus_map_ring_valloc(struct xenbus_device *dev, int gnt_ref, void **vaddr)
 463 {
 464         return ring_ops->map(dev, gnt_ref, vaddr);
 465 }
 466 EXPORT_SYMBOL_GPL(xenbus_map_ring_valloc);
 467
 468 static int xenbus_map_ring_valloc_pv(struct xenbus_device *dev,
 469                                      int gnt_ref, void **vaddr)
 470 {
 471         struct gnttab_map_grant_ref op = {
 472                 .flags = GNTMAP_host_map | GNTMAP_contains_pte,
 473                 .ref   = gnt_ref,
 474                 .dom   = dev->otherend_id,
 475         };
 476         struct xenbus_map_node *node;
 477         struct vm_struct *area;
 478         pte_t *pte;
 479
 480         *vaddr = NULL;
 481
 482         node = kzalloc(sizeof(*node), GFP_KERNEL);
 483         if (!node)
 484                 return -ENOMEM;
 485
 486         area = alloc_vm_area(PAGE_SIZE, &pte);
 487         if (!area) {
 488                 kfree(node);
 489                 return -ENOMEM;
 490         }
 491
 492         op.host_addr = arbitrary_virt_to_machine(pte).maddr;
 493
 494         gnttab_batch_map(&op, 1);
 495
 496         if (op.status != GNTST_okay) {
 497                 free_vm_area(area);
 498                 kfree(node);
 499                 xenbus_dev_fatal(dev, op.status,
 500                                  "mapping in shared page %d from domain %d",
 501                                  gnt_ref, dev->otherend_id);
 502                 return op.status;
 503         }
 504
 505         node->handle = op.handle;
 506         node->area = area;
 507
 508         spin_lock(&xenbus_valloc_lock);
 509         list_add(&node->next, &xenbus_valloc_pages);
 510         spin_unlock(&xenbus_valloc_lock);
 511
 512         *vaddr = area->addr;
 513         return 0;
 514 }
 515
 516 static int xenbus_map_ring_valloc_hvm(struct xenbus_device *dev,
 517                                       int gnt_ref, void **vaddr)
 518 {
 519         struct xenbus_map_node *node;
 520         int err;
 521         void *addr;
 522
 523         *vaddr = NULL;
 524
 525         node = kzalloc(sizeof(*node), GFP_KERNEL);
 526         if (!node)
 527                 return -ENOMEM;
 528
 529         err = alloc_xenballooned_pages(1, &node->page, false /* lowmem */);
 530         if (err)
 531                 goto out_err;
 532
 533         addr = pfn_to_kaddr(page_to_pfn(node->page));
 534
 535         err = xenbus_map_ring(dev, gnt_ref, &node->handle, addr);
 536         if (err)
 537                 goto out_err_free_ballooned_pages;
 538
 539         spin_lock(&xenbus_valloc_lock);
 540         list_add(&node->next, &xenbus_valloc_pages);
 541         spin_unlock(&xenbus_valloc_lock);
 542
 543         *vaddr = addr;
 544         return 0;
 545
 546  out_err_free_ballooned_pages:
 547         free_xenballooned_pages(1, &node->page);
 548  out_err:
 549         kfree(node);
 550         return err;
 551 }
 552
 553
 554 /**
 555  * xenbus_map_ring
 556  * @dev: xenbus device
 557  * @gnt_ref: grant reference
 558  * @handle: pointer to grant handle to be filled
 559  * @vaddr: address to be mapped to
 560  *
 561  * Map a page of memory into this domain from another domain's grant table.
 562  * xenbus_map_ring does not allocate the virtual address space (you must do
 563  * this yourself!). It only maps in the page to the specified address.
 564  * Returns 0 on success, and GNTST_* (see xen/include/interface/grant_table.h)
 565  * or -ENOMEM on error. If an error is returned, device will switch to
 566  * XenbusStateClosing and the error message will be saved in XenStore.
 567  */
 568 int xenbus_map_ring(struct xenbus_device *dev, int gnt_ref,
 569                     grant_handle_t *handle, void *vaddr)
 570 {
 571         struct gnttab_map_grant_ref op;
 572
 573         gnttab_set_map_op(&op, (unsigned long)vaddr, GNTMAP_host_map, gnt_ref,
 574                           dev->otherend_id);
 575
 576         gnttab_batch_map(&op, 1);
 577
 578         if (op.status != GNTST_okay) {
 579                 xenbus_dev_fatal(dev, op.status,
 580                                  "mapping in shared page %d from domain %d",
 581                                  gnt_ref, dev->otherend_id);
 582         } else
 583                 *handle = op.handle;
 584
 585         return op.status;
 586 }
 587 EXPORT_SYMBOL_GPL(xenbus_map_ring);
 588
 589
 590 /**
 591  * xenbus_unmap_ring_vfree
 592  * @dev: xenbus device
 593  * @vaddr: addr to unmap
 594  *
 595  * Based on Rusty Russell's skeleton driver's unmap_page.
 596  * Unmap a page of memory in this domain that was imported from another domain.
 597  * Use xenbus_unmap_ring_vfree if you mapped in your memory with
 598  * xenbus_map_ring_valloc (it will free the virtual address space).
 599  * Returns 0 on success and returns GNTST_* on error
 600  * (see xen/include/interface/grant_table.h).
 601  */
 602 int xenbus_unmap_ring_vfree(struct xenbus_device *dev, void *vaddr)
 603 {
 604         return ring_ops->unmap(dev, vaddr);
 605 }
 606 EXPORT_SYMBOL_GPL(xenbus_unmap_ring_vfree);
 607
 608 static int xenbus_unmap_ring_vfree_pv(struct xenbus_device *dev, void *vaddr)
 609 {
 610         struct xenbus_map_node *node;
 611         struct gnttab_unmap_grant_ref op = {
 612                 .host_addr = (unsigned long)vaddr,
 613         };
 614         unsigned int level;
 615
 616         spin_lock(&xenbus_valloc_lock);
 617         list_for_each_entry(node, &xenbus_valloc_pages, next) {
 618                 if (node->area->addr == vaddr) {
 619                         list_del(&node->next);
 620                         goto found;
 621                 }
 622         }
 623         node = NULL;
 624  found:
 625         spin_unlock(&xenbus_valloc_lock);
 626
 627         if (!node) {
 628                 xenbus_dev_error(dev, -ENOENT,
 629                                  "can't find mapped virtual address %p", vaddr);
 630                 return GNTST_bad_virt_addr;
 631         }
 632
 633         op.handle = node->handle;
 634         op.host_addr = arbitrary_virt_to_machine(
 635                 lookup_address((unsigned long)vaddr, &level)).maddr;
 636
 637         if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1))
 638                 BUG();
 639
 640         if (op.status == GNTST_okay)
 641                 free_vm_area(node->area);
 642         else
 643                 xenbus_dev_error(dev, op.status,
 644                                  "unmapping page at handle %d error %d",
 645                                  node->handle, op.status);
 646
 647         kfree(node);
 648         return op.status;
 649 }
 650
 651 static int xenbus_unmap_ring_vfree_hvm(struct xenbus_device *dev, void *vaddr)
 652 {
 653         int rv;
 654         struct xenbus_map_node *node;
 655         void *addr;
 656
 657         spin_lock(&xenbus_valloc_lock);
 658         list_for_each_entry(node, &xenbus_valloc_pages, next) {
 659                 addr = pfn_to_kaddr(page_to_pfn(node->page));
 660                 if (addr == vaddr) {
 661                         list_del(&node->next);
 662                         goto found;
 663                 }
 664         }
 665         node = addr = NULL;
 666  found:
 667         spin_unlock(&xenbus_valloc_lock);
 668
 669         if (!node) {
 670                 xenbus_dev_error(dev, -ENOENT,
 671                                  "can't find mapped virtual address %p", vaddr);
 672                 return GNTST_bad_virt_addr;
 673         }
 674
 675         rv = xenbus_unmap_ring(dev, node->handle, addr);
 676
 677         if (!rv)
 678                 free_xenballooned_pages(1, &node->page);
 679         else
 680                 WARN(1, "Leaking %p\n", vaddr);
 681
 682         kfree(node);
 683         return rv;
 684 }
 685
 686 /**
 687  * xenbus_unmap_ring
 688  * @dev: xenbus device
 689  * @handle: grant handle
 690  * @vaddr: addr to unmap
 691  *
 692  * Unmap a page of memory in this domain that was imported from another domain.
 693  * Returns 0 on success and returns GNTST_* on error
 694  * (see xen/include/interface/grant_table.h).
 695  */
 696 int xenbus_unmap_ring(struct xenbus_device *dev,
 697                       grant_handle_t handle, void *vaddr)
 698 {
 699         struct gnttab_unmap_grant_ref op;
 700
 701         gnttab_set_unmap_op(&op, (unsigned long)vaddr, GNTMAP_host_map, handle);
 702
 703         if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1))
 704                 BUG();
 705
 706         if (op.status != GNTST_okay)
 707                 xenbus_dev_error(dev, op.status,
 708                                  "unmapping page at handle %d error %d",
 709                                  handle, op.status);
 710
 711         return op.status;
 712 }
 713 EXPORT_SYMBOL_GPL(xenbus_unmap_ring);
 714
 715
 716 /**
 717  * xenbus_read_driver_state
 718  * @path: path for driver
 719  *
 720  * Return the state of the driver rooted at the given store path, or
 721  * XenbusStateUnknown if no state can be read.
 722  */
 723 enum xenbus_state xenbus_read_driver_state(const char *path)
 724 {
 725         enum xenbus_state result;
 726         int err = xenbus_gather(XBT_NIL, path, "state", "%d", &result, NULL);
 727         if (err)
 728                 result = XenbusStateUnknown;
 729
 730         return result;
 731 }
 732 EXPORT_SYMBOL_GPL(xenbus_read_driver_state);
 733
 734 static const struct xenbus_ring_ops ring_ops_pv = {
 735         .map = xenbus_map_ring_valloc_pv,
 736         .unmap = xenbus_unmap_ring_vfree_pv,
 737 };
 738
 739 static const struct xenbus_ring_ops ring_ops_hvm = {
 740         .map = xenbus_map_ring_valloc_hvm,
 741         .unmap = xenbus_unmap_ring_vfree_hvm,
 742 };
 743
 744 void __init xenbus_ring_ops_init(void)
 745 {
 746         if (xen_pv_domain())
 747                 ring_ops = &ring_ops_pv;
 748         else
 749                 ring_ops = &ring_ops_hvm;
 750 }