drivers/gpu/drm/ttm/ttm_bo_vm.c

   1 /* SPDX-License-Identifier: GPL-2.0 OR MIT */
   2 /**************************************************************************
   3  *
   4  * Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
   5  * All Rights Reserved.
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a
   8  * copy of this software and associated documentation files (the
   9  * "Software"), to deal in the Software without restriction, including
  10  * without limitation the rights to use, copy, modify, merge, publish,
  11  * distribute, sub license, and/or sell copies of the Software, and to
  12  * permit persons to whom the Software is furnished to do so, subject to
  13  * the following conditions:
  14  *
  15  * The above copyright notice and this permission notice (including the
  16  * next paragraph) shall be included in all copies or substantial portions
  17  * of the Software.
  18  *
  19  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  20  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  21  * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
  22  * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
  23  * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
  24  * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
  25  * USE OR OTHER DEALINGS IN THE SOFTWARE.
  26  *
  27  **************************************************************************/
  28 /*
  29  * Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
  30  */
  31
  32 #define pr_fmt(fmt) "[TTM] " fmt
  33
  34 #include <drm/ttm/ttm_module.h>
  35 #include <drm/ttm/ttm_bo_driver.h>
  36 #include <drm/ttm/ttm_placement.h>
  37 #include <drm/drm_vma_manager.h>
  38 #include <linux/mm.h>
  39 #include <linux/pfn_t.h>
  40 #include <linux/rbtree.h>
  41 #include <linux/module.h>
  42 #include <linux/uaccess.h>
  43 #include <linux/mem_encrypt.h>
  44
  45 static vm_fault_t ttm_bo_vm_fault_idle(struct ttm_buffer_object *bo,
  46                                 struct vm_fault *vmf)
  47 {
  48         vm_fault_t ret = 0;
  49         int err = 0;
  50
  51         if (likely(!bo->moving))
  52                 goto out_unlock;
  53
  54         /*
  55          * Quick non-stalling check for idle.
  56          */
  57         if (dma_fence_is_signaled(bo->moving))
  58                 goto out_clear;
  59
  60         /*
  61          * If possible, avoid waiting for GPU with mmap_lock
  62          * held.  We only do this if the fault allows retry and this
  63          * is the first attempt.
  64          */
  65         if (fault_flag_allow_retry_first(vmf->flags)) {
  66                 ret = VM_FAULT_RETRY;
  67                 if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT)
  68                         goto out_unlock;
  69
  70                 ttm_bo_get(bo);
  71                 mmap_read_unlock(vmf->vma->vm_mm);
  72                 (void) dma_fence_wait(bo->moving, true);
  73                 dma_resv_unlock(bo->base.resv);
  74                 ttm_bo_put(bo);
  75                 goto out_unlock;
  76         }
  77
  78         /*
  79          * Ordinary wait.
  80          */
  81         err = dma_fence_wait(bo->moving, true);
  82         if (unlikely(err != 0)) {
  83                 ret = (err != -ERESTARTSYS) ? VM_FAULT_SIGBUS :
  84                         VM_FAULT_NOPAGE;
  85                 goto out_unlock;
  86         }
  87
  88 out_clear:
  89         dma_fence_put(bo->moving);
  90         bo->moving = NULL;
  91
  92 out_unlock:
  93         return ret;
  94 }
  95
  96 static unsigned long ttm_bo_io_mem_pfn(struct ttm_buffer_object *bo,
  97                                        unsigned long page_offset)
  98 {
  99         struct ttm_bo_device *bdev = bo->bdev;
 100
 101         if (bdev->driver->io_mem_pfn)
 102                 return bdev->driver->io_mem_pfn(bo, page_offset);
 103
 104         return (bo->mem.bus.offset >> PAGE_SHIFT) + page_offset;
 105 }
 106
 107 /**
 108  * ttm_bo_vm_reserve - Reserve a buffer object in a retryable vm callback
 109  * @bo: The buffer object
 110  * @vmf: The fault structure handed to the callback
 111  *
 112  * vm callbacks like fault() and *_mkwrite() allow for the mm_sem to be dropped
 113  * during long waits, and after the wait the callback will be restarted. This
 114  * is to allow other threads using the same virtual memory space concurrent
 115  * access to map(), unmap() completely unrelated buffer objects. TTM buffer
 116  * object reservations sometimes wait for GPU and should therefore be
 117  * considered long waits. This function reserves the buffer object interruptibly
 118  * taking this into account. Starvation is avoided by the vm system not
 119  * allowing too many repeated restarts.
 120  * This function is intended to be used in customized fault() and _mkwrite()
 121  * handlers.
 122  *
 123  * Return:
 124  *    0 on success and the bo was reserved.
 125  *    VM_FAULT_RETRY if blocking wait.
 126  *    VM_FAULT_NOPAGE if blocking wait and retrying was not allowed.
 127  */
 128 vm_fault_t ttm_bo_vm_reserve(struct ttm_buffer_object *bo,
 129                              struct vm_fault *vmf)
 130 {
 131         /*
 132          * Work around locking order reversal in fault / nopfn
 133          * between mmap_lock and bo_reserve: Perform a trylock operation
 134          * for reserve, and if it fails, retry the fault after waiting
 135          * for the buffer to become unreserved.
 136          */
 137         if (unlikely(!dma_resv_trylock(bo->base.resv))) {
 138                 /*
 139                  * If the fault allows retry and this is the first
 140                  * fault attempt, we try to release the mmap_lock
 141                  * before waiting
 142                  */
 143                 if (fault_flag_allow_retry_first(vmf->flags)) {
 144                         if (!(vmf->flags & FAULT_FLAG_RETRY_NOWAIT)) {
 145                                 ttm_bo_get(bo);
 146                                 mmap_read_unlock(vmf->vma->vm_mm);
 147                                 if (!dma_resv_lock_interruptible(bo->base.resv,
 148                                                                  NULL))
 149                                         dma_resv_unlock(bo->base.resv);
 150                                 ttm_bo_put(bo);
 151                         }
 152
 153                         return VM_FAULT_RETRY;
 154                 }
 155
 156                 if (dma_resv_lock_interruptible(bo->base.resv, NULL))
 157                         return VM_FAULT_NOPAGE;
 158         }
 159
 160         /*
 161          * Refuse to fault imported pages. This should be handled
 162          * (if at all) by redirecting mmap to the exporter.
 163          */
 164         if (bo->ttm && (bo->ttm->page_flags & TTM_PAGE_FLAG_SG)) {
 165                 dma_resv_unlock(bo->base.resv);
 166                 return VM_FAULT_SIGBUS;
 167         }
 168
 169         return 0;
 170 }
 171 EXPORT_SYMBOL(ttm_bo_vm_reserve);
 172
 173 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 174 /**
 175  * ttm_bo_vm_insert_huge - Insert a pfn for PUD or PMD faults
 176  * @vmf: Fault data
 177  * @bo: The buffer object
 178  * @page_offset: Page offset from bo start
 179  * @fault_page_size: The size of the fault in pages.
 180  * @pgprot: The page protections.
 181  * Does additional checking whether it's possible to insert a PUD or PMD
 182  * pfn and performs the insertion.
 183  *
 184  * Return: VM_FAULT_NOPAGE on successful insertion, VM_FAULT_FALLBACK if
 185  * a huge fault was not possible, or on insertion error.
 186  */
 187 static vm_fault_t ttm_bo_vm_insert_huge(struct vm_fault *vmf,
 188                                         struct ttm_buffer_object *bo,
 189                                         pgoff_t page_offset,
 190                                         pgoff_t fault_page_size,
 191                                         pgprot_t pgprot)
 192 {
 193         pgoff_t i;
 194         vm_fault_t ret;
 195         unsigned long pfn;
 196         pfn_t pfnt;
 197         struct ttm_tt *ttm = bo->ttm;
 198         bool write = vmf->flags & FAULT_FLAG_WRITE;
 199
 200         /* Fault should not cross bo boundary. */
 201         page_offset &= ~(fault_page_size - 1);
 202         if (page_offset + fault_page_size > bo->num_pages)
 203                 goto out_fallback;
 204
 205         if (bo->mem.bus.is_iomem)
 206                 pfn = ttm_bo_io_mem_pfn(bo, page_offset);
 207         else
 208                 pfn = page_to_pfn(ttm->pages[page_offset]);
 209
 210         /* pfn must be fault_page_size aligned. */
 211         if ((pfn & (fault_page_size - 1)) != 0)
 212                 goto out_fallback;
 213
 214         /* Check that memory is contiguous. */
 215         if (!bo->mem.bus.is_iomem) {
 216                 for (i = 1; i < fault_page_size; ++i) {
 217                         if (page_to_pfn(ttm->pages[page_offset + i]) != pfn + i)
 218                                 goto out_fallback;
 219                 }
 220         } else if (bo->bdev->driver->io_mem_pfn) {
 221                 for (i = 1; i < fault_page_size; ++i) {
 222                         if (ttm_bo_io_mem_pfn(bo, page_offset + i) != pfn + i)
 223                                 goto out_fallback;
 224                 }
 225         }
 226
 227         pfnt = __pfn_to_pfn_t(pfn, PFN_DEV);
 228         if (fault_page_size == (HPAGE_PMD_SIZE >> PAGE_SHIFT))
 229                 ret = vmf_insert_pfn_pmd_prot(vmf, pfnt, pgprot, write);
 230 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 231         else if (fault_page_size == (HPAGE_PUD_SIZE >> PAGE_SHIFT))
 232                 ret = vmf_insert_pfn_pud_prot(vmf, pfnt, pgprot, write);
 233 #endif
 234         else
 235                 WARN_ON_ONCE(ret = VM_FAULT_FALLBACK);
 236
 237         if (ret != VM_FAULT_NOPAGE)
 238                 goto out_fallback;
 239
 240         return VM_FAULT_NOPAGE;
 241 out_fallback:
 242         count_vm_event(THP_FAULT_FALLBACK);
 243         return VM_FAULT_FALLBACK;
 244 }
 245 #else
 246 static vm_fault_t ttm_bo_vm_insert_huge(struct vm_fault *vmf,
 247                                         struct ttm_buffer_object *bo,
 248                                         pgoff_t page_offset,
 249                                         pgoff_t fault_page_size,
 250                                         pgprot_t pgprot)
 251 {
 252         return VM_FAULT_FALLBACK;
 253 }
 254 #endif
 255
 256 /**
 257  * ttm_bo_vm_fault_reserved - TTM fault helper
 258  * @vmf: The struct vm_fault given as argument to the fault callback
 259  * @prot: The page protection to be used for this memory area.
 260  * @num_prefault: Maximum number of prefault pages. The caller may want to
 261  * specify this based on madvice settings and the size of the GPU object
 262  * backed by the memory.
 263  * @fault_page_size: The size of the fault in pages.
 264  *
 265  * This function inserts one or more page table entries pointing to the
 266  * memory backing the buffer object, and then returns a return code
 267  * instructing the caller to retry the page access.
 268  *
 269  * Return:
 270  *   VM_FAULT_NOPAGE on success or pending signal
 271  *   VM_FAULT_SIGBUS on unspecified error
 272  *   VM_FAULT_OOM on out-of-memory
 273  *   VM_FAULT_RETRY if retryable wait
 274  */
 275 vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf,
 276                                     pgprot_t prot,
 277                                     pgoff_t num_prefault,
 278                                     pgoff_t fault_page_size)
 279 {
 280         struct vm_area_struct *vma = vmf->vma;
 281         struct ttm_buffer_object *bo = vma->vm_private_data;
 282         struct ttm_bo_device *bdev = bo->bdev;
 283         unsigned long page_offset;
 284         unsigned long page_last;
 285         unsigned long pfn;
 286         struct ttm_tt *ttm = NULL;
 287         struct page *page;
 288         int err;
 289         pgoff_t i;
 290         vm_fault_t ret = VM_FAULT_NOPAGE;
 291         unsigned long address = vmf->address;
 292
 293         /*
 294          * Wait for buffer data in transit, due to a pipelined
 295          * move.
 296          */
 297         ret = ttm_bo_vm_fault_idle(bo, vmf);
 298         if (unlikely(ret != 0))
 299                 return ret;
 300
 301         err = ttm_mem_io_reserve(bdev, &bo->mem);
 302         if (unlikely(err != 0))
 303                 return VM_FAULT_SIGBUS;
 304
 305         page_offset = ((address - vma->vm_start) >> PAGE_SHIFT) +
 306                 vma->vm_pgoff - drm_vma_node_start(&bo->base.vma_node);
 307         page_last = vma_pages(vma) + vma->vm_pgoff -
 308                 drm_vma_node_start(&bo->base.vma_node);
 309
 310         if (unlikely(page_offset >= bo->num_pages))
 311                 return VM_FAULT_SIGBUS;
 312
 313         prot = ttm_io_prot(bo, &bo->mem, prot);
 314         if (!bo->mem.bus.is_iomem) {
 315                 struct ttm_operation_ctx ctx = {
 316                         .interruptible = false,
 317                         .no_wait_gpu = false,
 318                         .force_alloc = true
 319                 };
 320
 321                 ttm = bo->ttm;
 322                 if (ttm_tt_populate(bdev, bo->ttm, &ctx))
 323                         return VM_FAULT_OOM;
 324         } else {
 325                 /* Iomem should not be marked encrypted */
 326                 prot = pgprot_decrypted(prot);
 327         }
 328
 329         /* We don't prefault on huge faults. Yet. */
 330         if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && fault_page_size != 1)
 331                 return ttm_bo_vm_insert_huge(vmf, bo, page_offset,
 332                                              fault_page_size, prot);
 333
 334         /*
 335          * Speculatively prefault a number of pages. Only error on
 336          * first page.
 337          */
 338         for (i = 0; i < num_prefault; ++i) {
 339                 if (bo->mem.bus.is_iomem) {
 340                         pfn = ttm_bo_io_mem_pfn(bo, page_offset);
 341                 } else {
 342                         page = ttm->pages[page_offset];
 343                         if (unlikely(!page && i == 0)) {
 344                                 return VM_FAULT_OOM;
 345                         } else if (unlikely(!page)) {
 346                                 break;
 347                         }
 348                         page->index = drm_vma_node_start(&bo->base.vma_node) +
 349                                 page_offset;
 350                         pfn = page_to_pfn(page);
 351                 }
 352
 353                 /*
 354                  * Note that the value of @prot at this point may differ from
 355                  * the value of @vma->vm_page_prot in the caching- and
 356                  * encryption bits. This is because the exact location of the
 357                  * data may not be known at mmap() time and may also change
 358                  * at arbitrary times while the data is mmap'ed.
 359                  * See vmf_insert_mixed_prot() for a discussion.
 360                  */
 361                 if (vma->vm_flags & VM_MIXEDMAP)
 362                         ret = vmf_insert_mixed_prot(vma, address,
 363                                                     __pfn_to_pfn_t(pfn, PFN_DEV),
 364                                                     prot);
 365                 else
 366                         ret = vmf_insert_pfn_prot(vma, address, pfn, prot);
 367
 368                 /* Never error on prefaulted PTEs */
 369                 if (unlikely((ret & VM_FAULT_ERROR))) {
 370                         if (i == 0)
 371                                 return VM_FAULT_NOPAGE;
 372                         else
 373                                 break;
 374                 }
 375
 376                 address += PAGE_SIZE;
 377                 if (unlikely(++page_offset >= page_last))
 378                         break;
 379         }
 380         return ret;
 381 }
 382 EXPORT_SYMBOL(ttm_bo_vm_fault_reserved);
 383
 384 vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf)
 385 {
 386         struct vm_area_struct *vma = vmf->vma;
 387         pgprot_t prot;
 388         struct ttm_buffer_object *bo = vma->vm_private_data;
 389         vm_fault_t ret;
 390
 391         ret = ttm_bo_vm_reserve(bo, vmf);
 392         if (ret)
 393                 return ret;
 394
 395         prot = vma->vm_page_prot;
 396         ret = ttm_bo_vm_fault_reserved(vmf, prot, TTM_BO_VM_NUM_PREFAULT, 1);
 397         if (ret == VM_FAULT_RETRY && !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT))
 398                 return ret;
 399
 400         dma_resv_unlock(bo->base.resv);
 401
 402         return ret;
 403 }
 404 EXPORT_SYMBOL(ttm_bo_vm_fault);
 405
 406 void ttm_bo_vm_open(struct vm_area_struct *vma)
 407 {
 408         struct ttm_buffer_object *bo = vma->vm_private_data;
 409
 410         WARN_ON(bo->bdev->dev_mapping != vma->vm_file->f_mapping);
 411
 412         ttm_bo_get(bo);
 413 }
 414 EXPORT_SYMBOL(ttm_bo_vm_open);
 415
 416 void ttm_bo_vm_close(struct vm_area_struct *vma)
 417 {
 418         struct ttm_buffer_object *bo = vma->vm_private_data;
 419
 420         ttm_bo_put(bo);
 421         vma->vm_private_data = NULL;
 422 }
 423 EXPORT_SYMBOL(ttm_bo_vm_close);
 424
 425 static int ttm_bo_vm_access_kmap(struct ttm_buffer_object *bo,
 426                                  unsigned long offset,
 427                                  uint8_t *buf, int len, int write)
 428 {
 429         unsigned long page = offset >> PAGE_SHIFT;
 430         unsigned long bytes_left = len;
 431         int ret;
 432
 433         /* Copy a page at a time, that way no extra virtual address
 434          * mapping is needed
 435          */
 436         offset -= page << PAGE_SHIFT;
 437         do {
 438                 unsigned long bytes = min(bytes_left, PAGE_SIZE - offset);
 439                 struct ttm_bo_kmap_obj map;
 440                 void *ptr;
 441                 bool is_iomem;
 442
 443                 ret = ttm_bo_kmap(bo, page, 1, &map);
 444                 if (ret)
 445                         return ret;
 446
 447                 ptr = (uint8_t *)ttm_kmap_obj_virtual(&map, &is_iomem) + offset;
 448                 WARN_ON_ONCE(is_iomem);
 449                 if (write)
 450                         memcpy(ptr, buf, bytes);
 451                 else
 452                         memcpy(buf, ptr, bytes);
 453                 ttm_bo_kunmap(&map);
 454
 455                 page++;
 456                 buf += bytes;
 457                 bytes_left -= bytes;
 458                 offset = 0;
 459         } while (bytes_left);
 460
 461         return len;
 462 }
 463
 464 int ttm_bo_vm_access(struct vm_area_struct *vma, unsigned long addr,
 465                      void *buf, int len, int write)
 466 {
 467         struct ttm_buffer_object *bo = vma->vm_private_data;
 468         unsigned long offset = (addr) - vma->vm_start +
 469                 ((vma->vm_pgoff - drm_vma_node_start(&bo->base.vma_node))
 470                  << PAGE_SHIFT);
 471         int ret;
 472
 473         if (len < 1 || (offset + len) >> PAGE_SHIFT > bo->num_pages)
 474                 return -EIO;
 475
 476         ret = ttm_bo_reserve(bo, true, false, NULL);
 477         if (ret)
 478                 return ret;
 479
 480         switch (bo->mem.mem_type) {
 481         case TTM_PL_SYSTEM:
 482                 if (unlikely(bo->ttm->page_flags & TTM_PAGE_FLAG_SWAPPED)) {
 483                         ret = ttm_tt_swapin(bo->ttm);
 484                         if (unlikely(ret != 0))
 485                                 return ret;
 486                 }
 487                 fallthrough;
 488         case TTM_PL_TT:
 489                 ret = ttm_bo_vm_access_kmap(bo, offset, buf, len, write);
 490                 break;
 491         default:
 492                 if (bo->bdev->driver->access_memory)
 493                         ret = bo->bdev->driver->access_memory(
 494                                 bo, offset, buf, len, write);
 495                 else
 496                         ret = -EIO;
 497         }
 498
 499         ttm_bo_unreserve(bo);
 500
 501         return ret;
 502 }
 503 EXPORT_SYMBOL(ttm_bo_vm_access);
 504
 505 static const struct vm_operations_struct ttm_bo_vm_ops = {
 506         .fault = ttm_bo_vm_fault,
 507         .open = ttm_bo_vm_open,
 508         .close = ttm_bo_vm_close,
 509         .access = ttm_bo_vm_access,
 510 };
 511
 512 static struct ttm_buffer_object *ttm_bo_vm_lookup(struct ttm_bo_device *bdev,
 513                                                   unsigned long offset,
 514                                                   unsigned long pages)
 515 {
 516         struct drm_vma_offset_node *node;
 517         struct ttm_buffer_object *bo = NULL;
 518
 519         drm_vma_offset_lock_lookup(bdev->vma_manager);
 520
 521         node = drm_vma_offset_lookup_locked(bdev->vma_manager, offset, pages);
 522         if (likely(node)) {
 523                 bo = container_of(node, struct ttm_buffer_object,
 524                                   base.vma_node);
 525                 bo = ttm_bo_get_unless_zero(bo);
 526         }
 527
 528         drm_vma_offset_unlock_lookup(bdev->vma_manager);
 529
 530         if (!bo)
 531                 pr_err("Could not find buffer object to map\n");
 532
 533         return bo;
 534 }
 535
 536 static void ttm_bo_mmap_vma_setup(struct ttm_buffer_object *bo, struct vm_area_struct *vma)
 537 {
 538         vma->vm_ops = &ttm_bo_vm_ops;
 539
 540         /*
 541          * Note: We're transferring the bo reference to
 542          * vma->vm_private_data here.
 543          */
 544
 545         vma->vm_private_data = bo;
 546
 547         /*
 548          * We'd like to use VM_PFNMAP on shared mappings, where
 549          * (vma->vm_flags & VM_SHARED) != 0, for performance reasons,
 550          * but for some reason VM_PFNMAP + x86 PAT + write-combine is very
 551          * bad for performance. Until that has been sorted out, use
 552          * VM_MIXEDMAP on all mappings. See freedesktop.org bug #75719
 553          */
 554         vma->vm_flags |= VM_MIXEDMAP;
 555         vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP;
 556 }
 557
 558 int ttm_bo_mmap(struct file *filp, struct vm_area_struct *vma,
 559                 struct ttm_bo_device *bdev)
 560 {
 561         struct ttm_bo_driver *driver;
 562         struct ttm_buffer_object *bo;
 563         int ret;
 564
 565         if (unlikely(vma->vm_pgoff < DRM_FILE_PAGE_OFFSET_START))
 566                 return -EINVAL;
 567
 568         bo = ttm_bo_vm_lookup(bdev, vma->vm_pgoff, vma_pages(vma));
 569         if (unlikely(!bo))
 570                 return -EINVAL;
 571
 572         driver = bo->bdev->driver;
 573         if (unlikely(!driver->verify_access)) {
 574                 ret = -EPERM;
 575                 goto out_unref;
 576         }
 577         ret = driver->verify_access(bo, filp);
 578         if (unlikely(ret != 0))
 579                 goto out_unref;
 580
 581         ttm_bo_mmap_vma_setup(bo, vma);
 582         return 0;
 583 out_unref:
 584         ttm_bo_put(bo);
 585         return ret;
 586 }
 587 EXPORT_SYMBOL(ttm_bo_mmap);
 588
 589 int ttm_bo_mmap_obj(struct vm_area_struct *vma, struct ttm_buffer_object *bo)
 590 {
 591         ttm_bo_get(bo);
 592         ttm_bo_mmap_vma_setup(bo, vma);
 593         return 0;
 594 }
 595 EXPORT_SYMBOL(ttm_bo_mmap_obj);