drivers/xen/gntdev.c

   1 /******************************************************************************
   2  * gntdev.c
   3  *
   4  * Device for accessing (in user-space) pages that have been granted by other
   5  * domains.
   6  *
   7  * Copyright (c) 2006-2007, D G Murray.
   8  *           (c) 2009 Gerd Hoffmann <kraxel@redhat.com>
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  18  */
  19
  20 #undef DEBUG
  21
  22 #include <linux/module.h>
  23 #include <linux/kernel.h>
  24 #include <linux/init.h>
  25 #include <linux/miscdevice.h>
  26 #include <linux/fs.h>
  27 #include <linux/mm.h>
  28 #include <linux/mman.h>
  29 #include <linux/mmu_notifier.h>
  30 #include <linux/types.h>
  31 #include <linux/uaccess.h>
  32 #include <linux/sched.h>
  33 #include <linux/spinlock.h>
  34 #include <linux/slab.h>
  35 #include <linux/highmem.h>
  36
  37 #include <xen/xen.h>
  38 #include <xen/grant_table.h>
  39 #include <xen/gntdev.h>
  40 #include <xen/events.h>
  41 #include <asm/xen/hypervisor.h>
  42 #include <asm/xen/hypercall.h>
  43 #include <asm/xen/page.h>
  44
  45 MODULE_LICENSE("GPL");
  46 MODULE_AUTHOR("Derek G. Murray <Derek.Murray@cl.cam.ac.uk>, "
  47               "Gerd Hoffmann <kraxel@redhat.com>");
  48 MODULE_DESCRIPTION("User-space granted page access driver");
  49
  50 static int limit = 1024*1024;
  51 module_param(limit, int, 0644);
  52 MODULE_PARM_DESC(limit, "Maximum number of grants that may be mapped by "
  53                 "the gntdev device");
  54
  55 static atomic_t pages_mapped = ATOMIC_INIT(0);
  56
  57 static int use_ptemod;
  58
  59 struct gntdev_priv {
  60         struct list_head maps;
  61         /* lock protects maps from concurrent changes */
  62         spinlock_t lock;
  63         struct mm_struct *mm;
  64         struct mmu_notifier mn;
  65 };
  66
  67 struct unmap_notify {
  68         int flags;
  69         /* Address relative to the start of the grant_map */
  70         int addr;
  71         int event;
  72 };
  73
  74 struct grant_map {
  75         struct list_head next;
  76         struct vm_area_struct *vma;
  77         int index;
  78         int count;
  79         int flags;
  80         int is_mapped;
  81         atomic_t users;
  82         struct unmap_notify notify;
  83         struct ioctl_gntdev_grant_ref *grants;
  84         struct gnttab_map_grant_ref   *map_ops;
  85         struct gnttab_unmap_grant_ref *unmap_ops;
  86         struct page **pages;
  87 };
  88
  89 static int unmap_grant_pages(struct grant_map *map, int offset, int pages);
  90
  91 /* ------------------------------------------------------------------ */
  92
  93 static void gntdev_print_maps(struct gntdev_priv *priv,
  94                               char *text, int text_index)
  95 {
  96 #ifdef DEBUG
  97         struct grant_map *map;
  98
  99         pr_debug("%s: maps list (priv %p)\n", __func__, priv);
 100         list_for_each_entry(map, &priv->maps, next)
 101                 pr_debug("  index %2d, count %2d %s\n",
 102                        map->index, map->count,
 103                        map->index == text_index && text ? text : "");
 104 #endif
 105 }
 106
 107 static struct grant_map *gntdev_alloc_map(struct gntdev_priv *priv, int count)
 108 {
 109         struct grant_map *add;
 110         int i;
 111
 112         add = kzalloc(sizeof(struct grant_map), GFP_KERNEL);
 113         if (NULL == add)
 114                 return NULL;
 115
 116         add->grants    = kzalloc(sizeof(add->grants[0])    * count, GFP_KERNEL);
 117         add->map_ops   = kzalloc(sizeof(add->map_ops[0])   * count, GFP_KERNEL);
 118         add->unmap_ops = kzalloc(sizeof(add->unmap_ops[0]) * count, GFP_KERNEL);
 119         add->pages     = kzalloc(sizeof(add->pages[0])     * count, GFP_KERNEL);
 120         if (NULL == add->grants    ||
 121             NULL == add->map_ops   ||
 122             NULL == add->unmap_ops ||
 123             NULL == add->pages)
 124                 goto err;
 125
 126         for (i = 0; i < count; i++) {
 127                 add->pages[i] = alloc_page(GFP_KERNEL | __GFP_HIGHMEM);
 128                 if (add->pages[i] == NULL)
 129                         goto err;
 130         }
 131
 132         add->index = 0;
 133         add->count = count;
 134         atomic_set(&add->users, 1);
 135
 136         return add;
 137
 138 err:
 139         if (add->pages)
 140                 for (i = 0; i < count; i++) {
 141                         if (add->pages[i])
 142                                 __free_page(add->pages[i]);
 143                 }
 144         kfree(add->pages);
 145         kfree(add->grants);
 146         kfree(add->map_ops);
 147         kfree(add->unmap_ops);
 148         kfree(add);
 149         return NULL;
 150 }
 151
 152 static void gntdev_add_map(struct gntdev_priv *priv, struct grant_map *add)
 153 {
 154         struct grant_map *map;
 155
 156         list_for_each_entry(map, &priv->maps, next) {
 157                 if (add->index + add->count < map->index) {
 158                         list_add_tail(&add->next, &map->next);
 159                         goto done;
 160                 }
 161                 add->index = map->index + map->count;
 162         }
 163         list_add_tail(&add->next, &priv->maps);
 164
 165 done:
 166         gntdev_print_maps(priv, "[new]", add->index);
 167 }
 168
 169 static struct grant_map *gntdev_find_map_index(struct gntdev_priv *priv,
 170                 int index, int count)
 171 {
 172         struct grant_map *map;
 173
 174         list_for_each_entry(map, &priv->maps, next) {
 175                 if (map->index != index)
 176                         continue;
 177                 if (count && map->count != count)
 178                         continue;
 179                 return map;
 180         }
 181         return NULL;
 182 }
 183
 184 static void gntdev_put_map(struct grant_map *map)
 185 {
 186         int i;
 187
 188         if (!map)
 189                 return;
 190
 191         if (!atomic_dec_and_test(&map->users))
 192                 return;
 193
 194         atomic_sub(map->count, &pages_mapped);
 195
 196         if (map->notify.flags & UNMAP_NOTIFY_SEND_EVENT) {
 197                 notify_remote_via_evtchn(map->notify.event);
 198         }
 199
 200         if (map->pages) {
 201                 if (!use_ptemod)
 202                         unmap_grant_pages(map, 0, map->count);
 203
 204                 for (i = 0; i < map->count; i++) {
 205                         uint32_t check, *tmp;
 206                         if (!map->pages[i])
 207                                 continue;
 208                         /* XXX When unmapping in an HVM domain, Xen will
 209                          * sometimes end up mapping the GFN to an invalid MFN.
 210                          * In this case, writes will be discarded and reads will
 211                          * return all 0xFF bytes.  Leak these unusable GFNs
 212                          * until Xen supports fixing their p2m mapping.
 213                          *
 214                          * Confirmed present in Xen 4.1-RC3 with HVM source
 215                          */
 216                         tmp = kmap(map->pages[i]);
 217                         *tmp = 0xdeaddead;
 218                         mb();
 219                         check = *tmp;
 220                         kunmap(map->pages[i]);
 221                         if (check == 0xdeaddead)
 222                                 __free_page(map->pages[i]);
 223                         else
 224                                 pr_debug("Discard page %d=%ld\n", i,
 225                                         page_to_pfn(map->pages[i]));
 226                 }
 227         }
 228         kfree(map->pages);
 229         kfree(map->grants);
 230         kfree(map->map_ops);
 231         kfree(map->unmap_ops);
 232         kfree(map);
 233 }
 234
 235 /* ------------------------------------------------------------------ */
 236
 237 static int find_grant_ptes(pte_t *pte, pgtable_t token,
 238                 unsigned long addr, void *data)
 239 {
 240         struct grant_map *map = data;
 241         unsigned int pgnr = (addr - map->vma->vm_start) >> PAGE_SHIFT;
 242         int flags = map->flags | GNTMAP_application_map | GNTMAP_contains_pte;
 243         u64 pte_maddr;
 244
 245         BUG_ON(pgnr >= map->count);
 246         pte_maddr = arbitrary_virt_to_machine(pte).maddr;
 247
 248         gnttab_set_map_op(&map->map_ops[pgnr], pte_maddr, flags,
 249                           map->grants[pgnr].ref,
 250                           map->grants[pgnr].domid);
 251         gnttab_set_unmap_op(&map->unmap_ops[pgnr], pte_maddr, flags,
 252                             0 /* handle */);
 253         return 0;
 254 }
 255
 256 static int map_grant_pages(struct grant_map *map)
 257 {
 258         int i, err = 0;
 259         phys_addr_t addr;
 260
 261         if (!use_ptemod) {
 262                 for (i = 0; i < map->count; i++) {
 263                         addr = (phys_addr_t)
 264                                 pfn_to_kaddr(page_to_pfn(map->pages[i]));
 265                         gnttab_set_map_op(&map->map_ops[i], addr, map->flags,
 266                                 map->grants[i].ref,
 267                                 map->grants[i].domid);
 268                         gnttab_set_unmap_op(&map->unmap_ops[i], addr,
 269                                 map->flags, 0 /* handle */);
 270                 }
 271         }
 272
 273         pr_debug("map %d+%d\n", map->index, map->count);
 274         err = gnttab_map_refs(map->map_ops, map->pages, map->count);
 275         if (err)
 276                 return err;
 277
 278         for (i = 0; i < map->count; i++) {
 279                 if (map->map_ops[i].status)
 280                         err = -EINVAL;
 281                 map->unmap_ops[i].handle = map->map_ops[i].handle;
 282         }
 283         return err;
 284 }
 285
 286 static int unmap_grant_pages(struct grant_map *map, int offset, int pages)
 287 {
 288         int i, err = 0;
 289
 290         if (map->notify.flags & UNMAP_NOTIFY_CLEAR_BYTE) {
 291                 int pgno = (map->notify.addr >> PAGE_SHIFT);
 292                 if (pgno >= offset && pgno < offset + pages) {
 293                         uint8_t *tmp = kmap(map->pages[pgno]);
 294                         tmp[map->notify.addr & (PAGE_SIZE-1)] = 0;
 295                         kunmap(map->pages[pgno]);
 296                         map->notify.flags &= ~UNMAP_NOTIFY_CLEAR_BYTE;
 297                 }
 298         }
 299
 300         pr_debug("map %d+%d [%d+%d]\n", map->index, map->count, offset, pages);
 301         err = gnttab_unmap_refs(map->unmap_ops + offset, map->pages, pages);
 302         if (err)
 303                 return err;
 304
 305         for (i = 0; i < pages; i++) {
 306                 if (map->unmap_ops[offset+i].status)
 307                         err = -EINVAL;
 308                 map->unmap_ops[offset+i].handle = 0;
 309         }
 310         return err;
 311 }
 312
 313 /* ------------------------------------------------------------------ */
 314
 315 static void gntdev_vma_close(struct vm_area_struct *vma)
 316 {
 317         struct grant_map *map = vma->vm_private_data;
 318
 319         pr_debug("close %p\n", vma);
 320         map->is_mapped = 0;
 321         map->vma = NULL;
 322         vma->vm_private_data = NULL;
 323         gntdev_put_map(map);
 324 }
 325
 326 static struct vm_operations_struct gntdev_vmops = {
 327         .close = gntdev_vma_close,
 328 };
 329
 330 /* ------------------------------------------------------------------ */
 331
 332 static void mn_invl_range_start(struct mmu_notifier *mn,
 333                                 struct mm_struct *mm,
 334                                 unsigned long start, unsigned long end)
 335 {
 336         struct gntdev_priv *priv = container_of(mn, struct gntdev_priv, mn);
 337         struct grant_map *map;
 338         unsigned long mstart, mend;
 339         int err;
 340
 341         spin_lock(&priv->lock);
 342         list_for_each_entry(map, &priv->maps, next) {
 343                 if (!map->vma)
 344                         continue;
 345                 if (!map->is_mapped)
 346                         continue;
 347                 if (map->vma->vm_start >= end)
 348                         continue;
 349                 if (map->vma->vm_end <= start)
 350                         continue;
 351                 mstart = max(start, map->vma->vm_start);
 352                 mend   = min(end,   map->vma->vm_end);
 353                 pr_debug("map %d+%d (%lx %lx), range %lx %lx, mrange %lx %lx\n",
 354                                 map->index, map->count,
 355                                 map->vma->vm_start, map->vma->vm_end,
 356                                 start, end, mstart, mend);
 357                 err = unmap_grant_pages(map,
 358                                         (mstart - map->vma->vm_start) >> PAGE_SHIFT,
 359                                         (mend - mstart) >> PAGE_SHIFT);
 360                 WARN_ON(err);
 361         }
 362         spin_unlock(&priv->lock);
 363 }
 364
 365 static void mn_invl_page(struct mmu_notifier *mn,
 366                          struct mm_struct *mm,
 367                          unsigned long address)
 368 {
 369         mn_invl_range_start(mn, mm, address, address + PAGE_SIZE);
 370 }
 371
 372 static void mn_release(struct mmu_notifier *mn,
 373                        struct mm_struct *mm)
 374 {
 375         struct gntdev_priv *priv = container_of(mn, struct gntdev_priv, mn);
 376         struct grant_map *map;
 377         int err;
 378
 379         spin_lock(&priv->lock);
 380         list_for_each_entry(map, &priv->maps, next) {
 381                 if (!map->vma)
 382                         continue;
 383                 pr_debug("map %d+%d (%lx %lx)\n",
 384                                 map->index, map->count,
 385                                 map->vma->vm_start, map->vma->vm_end);
 386                 err = unmap_grant_pages(map, /* offset */ 0, map->count);
 387                 WARN_ON(err);
 388         }
 389         spin_unlock(&priv->lock);
 390 }
 391
 392 struct mmu_notifier_ops gntdev_mmu_ops = {
 393         .release                = mn_release,
 394         .invalidate_page        = mn_invl_page,
 395         .invalidate_range_start = mn_invl_range_start,
 396 };
 397
 398 /* ------------------------------------------------------------------ */
 399
 400 static int gntdev_open(struct inode *inode, struct file *flip)
 401 {
 402         struct gntdev_priv *priv;
 403         int ret = 0;
 404
 405         priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 406         if (!priv)
 407                 return -ENOMEM;
 408
 409         INIT_LIST_HEAD(&priv->maps);
 410         spin_lock_init(&priv->lock);
 411
 412         if (use_ptemod) {
 413                 priv->mm = get_task_mm(current);
 414                 if (!priv->mm) {
 415                         kfree(priv);
 416                         return -ENOMEM;
 417                 }
 418                 priv->mn.ops = &gntdev_mmu_ops;
 419                 ret = mmu_notifier_register(&priv->mn, priv->mm);
 420                 mmput(priv->mm);
 421         }
 422
 423         if (ret) {
 424                 kfree(priv);
 425                 return ret;
 426         }
 427
 428         flip->private_data = priv;
 429         pr_debug("priv %p\n", priv);
 430
 431         return 0;
 432 }
 433
 434 static int gntdev_release(struct inode *inode, struct file *flip)
 435 {
 436         struct gntdev_priv *priv = flip->private_data;
 437         struct grant_map *map;
 438
 439         pr_debug("priv %p\n", priv);
 440
 441         spin_lock(&priv->lock);
 442         while (!list_empty(&priv->maps)) {
 443                 map = list_entry(priv->maps.next, struct grant_map, next);
 444                 list_del(&map->next);
 445                 gntdev_put_map(map);
 446         }
 447         spin_unlock(&priv->lock);
 448
 449         if (use_ptemod)
 450                 mmu_notifier_unregister(&priv->mn, priv->mm);
 451         kfree(priv);
 452         return 0;
 453 }
 454
 455 static long gntdev_ioctl_map_grant_ref(struct gntdev_priv *priv,
 456                                        struct ioctl_gntdev_map_grant_ref __user *u)
 457 {
 458         struct ioctl_gntdev_map_grant_ref op;
 459         struct grant_map *map;
 460         int err;
 461
 462         if (copy_from_user(&op, u, sizeof(op)) != 0)
 463                 return -EFAULT;
 464         pr_debug("priv %p, add %d\n", priv, op.count);
 465         if (unlikely(op.count <= 0))
 466                 return -EINVAL;
 467
 468         err = -ENOMEM;
 469         map = gntdev_alloc_map(priv, op.count);
 470         if (!map)
 471                 return err;
 472
 473         if (unlikely(atomic_add_return(op.count, &pages_mapped) > limit)) {
 474                 pr_debug("can't map: over limit\n");
 475                 gntdev_put_map(map);
 476                 return err;
 477         }
 478
 479         if (copy_from_user(map->grants, &u->refs,
 480                            sizeof(map->grants[0]) * op.count) != 0) {
 481                 gntdev_put_map(map);
 482                 return err;
 483         }
 484
 485         spin_lock(&priv->lock);
 486         gntdev_add_map(priv, map);
 487         op.index = map->index << PAGE_SHIFT;
 488         spin_unlock(&priv->lock);
 489
 490         if (copy_to_user(u, &op, sizeof(op)) != 0)
 491                 return -EFAULT;
 492
 493         return 0;
 494 }
 495
 496 static long gntdev_ioctl_unmap_grant_ref(struct gntdev_priv *priv,
 497                                          struct ioctl_gntdev_unmap_grant_ref __user *u)
 498 {
 499         struct ioctl_gntdev_unmap_grant_ref op;
 500         struct grant_map *map;
 501         int err = -ENOENT;
 502
 503         if (copy_from_user(&op, u, sizeof(op)) != 0)
 504                 return -EFAULT;
 505         pr_debug("priv %p, del %d+%d\n", priv, (int)op.index, (int)op.count);
 506
 507         spin_lock(&priv->lock);
 508         map = gntdev_find_map_index(priv, op.index >> PAGE_SHIFT, op.count);
 509         if (map) {
 510                 list_del(&map->next);
 511                 gntdev_put_map(map);
 512                 err = 0;
 513         }
 514         spin_unlock(&priv->lock);
 515         return err;
 516 }
 517
 518 static long gntdev_ioctl_get_offset_for_vaddr(struct gntdev_priv *priv,
 519                                               struct ioctl_gntdev_get_offset_for_vaddr __user *u)
 520 {
 521         struct ioctl_gntdev_get_offset_for_vaddr op;
 522         struct vm_area_struct *vma;
 523         struct grant_map *map;
 524
 525         if (copy_from_user(&op, u, sizeof(op)) != 0)
 526                 return -EFAULT;
 527         pr_debug("priv %p, offset for vaddr %lx\n", priv, (unsigned long)op.vaddr);
 528
 529         vma = find_vma(current->mm, op.vaddr);
 530         if (!vma || vma->vm_ops != &gntdev_vmops)
 531                 return -EINVAL;
 532
 533         map = vma->vm_private_data;
 534         if (!map)
 535                 return -EINVAL;
 536
 537         op.offset = map->index << PAGE_SHIFT;
 538         op.count = map->count;
 539
 540         if (copy_to_user(u, &op, sizeof(op)) != 0)
 541                 return -EFAULT;
 542         return 0;
 543 }
 544
 545 static long gntdev_ioctl_notify(struct gntdev_priv *priv, void __user *u)
 546 {
 547         struct ioctl_gntdev_unmap_notify op;
 548         struct grant_map *map;
 549         int rc;
 550
 551         if (copy_from_user(&op, u, sizeof(op)))
 552                 return -EFAULT;
 553
 554         if (op.action & ~(UNMAP_NOTIFY_CLEAR_BYTE|UNMAP_NOTIFY_SEND_EVENT))
 555                 return -EINVAL;
 556
 557         spin_lock(&priv->lock);
 558
 559         list_for_each_entry(map, &priv->maps, next) {
 560                 uint64_t begin = map->index << PAGE_SHIFT;
 561                 uint64_t end = (map->index + map->count) << PAGE_SHIFT;
 562                 if (op.index >= begin && op.index < end)
 563                         goto found;
 564         }
 565         rc = -ENOENT;
 566         goto unlock_out;
 567
 568  found:
 569         map->notify.flags = op.action;
 570         map->notify.addr = op.index - (map->index << PAGE_SHIFT);
 571         map->notify.event = op.event_channel_port;
 572         rc = 0;
 573  unlock_out:
 574         spin_unlock(&priv->lock);
 575         return rc;
 576 }
 577
 578 static long gntdev_ioctl(struct file *flip,
 579                          unsigned int cmd, unsigned long arg)
 580 {
 581         struct gntdev_priv *priv = flip->private_data;
 582         void __user *ptr = (void __user *)arg;
 583
 584         switch (cmd) {
 585         case IOCTL_GNTDEV_MAP_GRANT_REF:
 586                 return gntdev_ioctl_map_grant_ref(priv, ptr);
 587
 588         case IOCTL_GNTDEV_UNMAP_GRANT_REF:
 589                 return gntdev_ioctl_unmap_grant_ref(priv, ptr);
 590
 591         case IOCTL_GNTDEV_GET_OFFSET_FOR_VADDR:
 592                 return gntdev_ioctl_get_offset_for_vaddr(priv, ptr);
 593
 594         case IOCTL_GNTDEV_SET_UNMAP_NOTIFY:
 595                 return gntdev_ioctl_notify(priv, ptr);
 596
 597         default:
 598                 pr_debug("priv %p, unknown cmd %x\n", priv, cmd);
 599                 return -ENOIOCTLCMD;
 600         }
 601
 602         return 0;
 603 }
 604
 605 static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)
 606 {
 607         struct gntdev_priv *priv = flip->private_data;
 608         int index = vma->vm_pgoff;
 609         int count = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
 610         struct grant_map *map;
 611         int i, err = -EINVAL;
 612
 613         if ((vma->vm_flags & VM_WRITE) && !(vma->vm_flags & VM_SHARED))
 614                 return -EINVAL;
 615
 616         pr_debug("map %d+%d at %lx (pgoff %lx)\n",
 617                         index, count, vma->vm_start, vma->vm_pgoff);
 618
 619         spin_lock(&priv->lock);
 620         map = gntdev_find_map_index(priv, index, count);
 621         if (!map)
 622                 goto unlock_out;
 623         if (use_ptemod && map->vma)
 624                 goto unlock_out;
 625         if (use_ptemod && priv->mm != vma->vm_mm) {
 626                 printk(KERN_WARNING "Huh? Other mm?\n");
 627                 goto unlock_out;
 628         }
 629
 630         atomic_inc(&map->users);
 631
 632         vma->vm_ops = &gntdev_vmops;
 633
 634         vma->vm_flags |= VM_RESERVED|VM_DONTCOPY|VM_DONTEXPAND|VM_PFNMAP;
 635
 636         vma->vm_private_data = map;
 637
 638         if (use_ptemod)
 639                 map->vma = vma;
 640
 641         map->flags = GNTMAP_host_map;
 642         if (!(vma->vm_flags & VM_WRITE))
 643                 map->flags |= GNTMAP_readonly;
 644
 645         spin_unlock(&priv->lock);
 646
 647         if (use_ptemod) {
 648                 err = apply_to_page_range(vma->vm_mm, vma->vm_start,
 649                                           vma->vm_end - vma->vm_start,
 650                                           find_grant_ptes, map);
 651                 if (err) {
 652                         printk(KERN_WARNING "find_grant_ptes() failure.\n");
 653                         return err;
 654                 }
 655         }
 656
 657         err = map_grant_pages(map);
 658         if (err) {
 659                 printk(KERN_WARNING "map_grant_pages() failure.\n");
 660                 return err;
 661         }
 662
 663         map->is_mapped = 1;
 664
 665         if (!use_ptemod) {
 666                 for (i = 0; i < count; i++) {
 667                         err = vm_insert_page(vma, vma->vm_start + i*PAGE_SIZE,
 668                                 map->pages[i]);
 669                         if (err)
 670                                 return err;
 671                 }
 672         }
 673
 674         return 0;
 675
 676 unlock_out:
 677         spin_unlock(&priv->lock);
 678         return err;
 679 }
 680
 681 static const struct file_operations gntdev_fops = {
 682         .owner = THIS_MODULE,
 683         .open = gntdev_open,
 684         .release = gntdev_release,
 685         .mmap = gntdev_mmap,
 686         .unlocked_ioctl = gntdev_ioctl
 687 };
 688
 689 static struct miscdevice gntdev_miscdev = {
 690         .minor        = MISC_DYNAMIC_MINOR,
 691         .name         = "xen/gntdev",
 692         .fops         = &gntdev_fops,
 693 };
 694
 695 /* ------------------------------------------------------------------ */
 696
 697 static int __init gntdev_init(void)
 698 {
 699         int err;
 700
 701         if (!xen_domain())
 702                 return -ENODEV;
 703
 704         use_ptemod = xen_pv_domain();
 705
 706         err = misc_register(&gntdev_miscdev);
 707         if (err != 0) {
 708                 printk(KERN_ERR "Could not register gntdev device\n");
 709                 return err;
 710         }
 711         return 0;
 712 }
 713
 714 static void __exit gntdev_exit(void)
 715 {
 716         misc_deregister(&gntdev_miscdev);
 717 }
 718
 719 module_init(gntdev_init);
 720 module_exit(gntdev_exit);
 721
 722 /* ------------------------------------------------------------------ */