drivers/gpu/drm/ttm/ttm_bo_util.c

   1 /* SPDX-License-Identifier: GPL-2.0 OR MIT */
   2 /**************************************************************************
   3  *
   4  * Copyright (c) 2007-2009 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 #include <drm/ttm/ttm_bo_driver.h>
  33 #include <drm/ttm/ttm_placement.h>
  34 #include <drm/drm_cache.h>
  35 #include <drm/drm_vma_manager.h>
  36 #include <linux/dma-buf-map.h>
  37 #include <linux/io.h>
  38 #include <linux/highmem.h>
  39 #include <linux/wait.h>
  40 #include <linux/slab.h>
  41 #include <linux/vmalloc.h>
  42 #include <linux/module.h>
  43 #include <linux/dma-resv.h>
  44
  45 struct ttm_transfer_obj {
  46         struct ttm_buffer_object base;
  47         struct ttm_buffer_object *bo;
  48 };
  49
  50 int ttm_mem_io_reserve(struct ttm_device *bdev,
  51                        struct ttm_resource *mem)
  52 {
  53         if (mem->bus.offset || mem->bus.addr)
  54                 return 0;
  55
  56         mem->bus.is_iomem = false;
  57         if (!bdev->funcs->io_mem_reserve)
  58                 return 0;
  59
  60         return bdev->funcs->io_mem_reserve(bdev, mem);
  61 }
  62
  63 void ttm_mem_io_free(struct ttm_device *bdev,
  64                      struct ttm_resource *mem)
  65 {
  66         if (!mem->bus.offset && !mem->bus.addr)
  67                 return;
  68
  69         if (bdev->funcs->io_mem_free)
  70                 bdev->funcs->io_mem_free(bdev, mem);
  71
  72         mem->bus.offset = 0;
  73         mem->bus.addr = NULL;
  74 }
  75
  76 /**
  77  * ttm_move_memcpy - Helper to perform a memcpy ttm move operation.
  78  * @bo: The struct ttm_buffer_object.
  79  * @new_mem: The struct ttm_resource we're moving to (copy destination).
  80  * @new_iter: A struct ttm_kmap_iter representing the destination resource.
  81  * @src_iter: A struct ttm_kmap_iter representing the source resource.
  82  *
  83  * This function is intended to be able to move out async under a
  84  * dma-fence if desired.
  85  */
  86 void ttm_move_memcpy(struct ttm_buffer_object *bo,
  87                      u32 num_pages,
  88                      struct ttm_kmap_iter *dst_iter,
  89                      struct ttm_kmap_iter *src_iter)
  90 {
  91         const struct ttm_kmap_iter_ops *dst_ops = dst_iter->ops;
  92         const struct ttm_kmap_iter_ops *src_ops = src_iter->ops;
  93         struct ttm_tt *ttm = bo->ttm;
  94         struct dma_buf_map src_map, dst_map;
  95         pgoff_t i;
  96
  97         /* Single TTM move. NOP */
  98         if (dst_ops->maps_tt && src_ops->maps_tt)
  99                 return;
 100
 101         /* Don't move nonexistent data. Clear destination instead. */
 102         if (src_ops->maps_tt && (!ttm || !ttm_tt_is_populated(ttm))) {
 103                 if (ttm && !(ttm->page_flags & TTM_PAGE_FLAG_ZERO_ALLOC))
 104                         return;
 105
 106                 for (i = 0; i < num_pages; ++i) {
 107                         dst_ops->map_local(dst_iter, &dst_map, i);
 108                         if (dst_map.is_iomem)
 109                                 memset_io(dst_map.vaddr_iomem, 0, PAGE_SIZE);
 110                         else
 111                                 memset(dst_map.vaddr, 0, PAGE_SIZE);
 112                         if (dst_ops->unmap_local)
 113                                 dst_ops->unmap_local(dst_iter, &dst_map);
 114                 }
 115                 return;
 116         }
 117
 118         for (i = 0; i < num_pages; ++i) {
 119                 dst_ops->map_local(dst_iter, &dst_map, i);
 120                 src_ops->map_local(src_iter, &src_map, i);
 121
 122                 drm_memcpy_from_wc(&dst_map, &src_map, PAGE_SIZE);
 123
 124                 if (src_ops->unmap_local)
 125                         src_ops->unmap_local(src_iter, &src_map);
 126                 if (dst_ops->unmap_local)
 127                         dst_ops->unmap_local(dst_iter, &dst_map);
 128         }
 129 }
 130 EXPORT_SYMBOL(ttm_move_memcpy);
 131
 132 int ttm_bo_move_memcpy(struct ttm_buffer_object *bo,
 133                        struct ttm_operation_ctx *ctx,
 134                        struct ttm_resource *dst_mem)
 135 {
 136         struct ttm_device *bdev = bo->bdev;
 137         struct ttm_resource_manager *dst_man =
 138                 ttm_manager_type(bo->bdev, dst_mem->mem_type);
 139         struct ttm_tt *ttm = bo->ttm;
 140         struct ttm_resource *src_mem = bo->resource;
 141         struct ttm_resource_manager *src_man =
 142                 ttm_manager_type(bdev, src_mem->mem_type);
 143         struct ttm_resource src_copy = *src_mem;
 144         union {
 145                 struct ttm_kmap_iter_tt tt;
 146                 struct ttm_kmap_iter_linear_io io;
 147         } _dst_iter, _src_iter;
 148         struct ttm_kmap_iter *dst_iter, *src_iter;
 149         int ret = 0;
 150
 151         if (ttm && ((ttm->page_flags & TTM_PAGE_FLAG_SWAPPED) ||
 152                     dst_man->use_tt)) {
 153                 ret = ttm_tt_populate(bdev, ttm, ctx);
 154                 if (ret)
 155                         return ret;
 156         }
 157
 158         dst_iter = ttm_kmap_iter_linear_io_init(&_dst_iter.io, bdev, dst_mem);
 159         if (PTR_ERR(dst_iter) == -EINVAL && dst_man->use_tt)
 160                 dst_iter = ttm_kmap_iter_tt_init(&_dst_iter.tt, bo->ttm);
 161         if (IS_ERR(dst_iter))
 162                 return PTR_ERR(dst_iter);
 163
 164         src_iter = ttm_kmap_iter_linear_io_init(&_src_iter.io, bdev, src_mem);
 165         if (PTR_ERR(src_iter) == -EINVAL && src_man->use_tt)
 166                 src_iter = ttm_kmap_iter_tt_init(&_src_iter.tt, bo->ttm);
 167         if (IS_ERR(src_iter)) {
 168                 ret = PTR_ERR(src_iter);
 169                 goto out_src_iter;
 170         }
 171
 172         ttm_move_memcpy(bo, dst_mem->num_pages, dst_iter, src_iter);
 173         src_copy = *src_mem;
 174         ttm_bo_move_sync_cleanup(bo, dst_mem);
 175
 176         if (!src_iter->ops->maps_tt)
 177                 ttm_kmap_iter_linear_io_fini(&_src_iter.io, bdev, &src_copy);
 178 out_src_iter:
 179         if (!dst_iter->ops->maps_tt)
 180                 ttm_kmap_iter_linear_io_fini(&_dst_iter.io, bdev, dst_mem);
 181
 182         return ret;
 183 }
 184 EXPORT_SYMBOL(ttm_bo_move_memcpy);
 185
 186 static void ttm_transfered_destroy(struct ttm_buffer_object *bo)
 187 {
 188         struct ttm_transfer_obj *fbo;
 189
 190         fbo = container_of(bo, struct ttm_transfer_obj, base);
 191         ttm_bo_put(fbo->bo);
 192         kfree(fbo);
 193 }
 194
 195 /**
 196  * ttm_buffer_object_transfer
 197  *
 198  * @bo: A pointer to a struct ttm_buffer_object.
 199  * @new_obj: A pointer to a pointer to a newly created ttm_buffer_object,
 200  * holding the data of @bo with the old placement.
 201  *
 202  * This is a utility function that may be called after an accelerated move
 203  * has been scheduled. A new buffer object is created as a placeholder for
 204  * the old data while it's being copied. When that buffer object is idle,
 205  * it can be destroyed, releasing the space of the old placement.
 206  * Returns:
 207  * !0: Failure.
 208  */
 209
 210 static int ttm_buffer_object_transfer(struct ttm_buffer_object *bo,
 211                                       struct ttm_buffer_object **new_obj)
 212 {
 213         struct ttm_transfer_obj *fbo;
 214         int ret;
 215
 216         fbo = kmalloc(sizeof(*fbo), GFP_KERNEL);
 217         if (!fbo)
 218                 return -ENOMEM;
 219
 220         fbo->base = *bo;
 221
 222         ttm_bo_get(bo);
 223         fbo->bo = bo;
 224
 225         /**
 226          * Fix up members that we shouldn't copy directly:
 227          * TODO: Explicit member copy would probably be better here.
 228          */
 229
 230         atomic_inc(&ttm_glob.bo_count);
 231         INIT_LIST_HEAD(&fbo->base.ddestroy);
 232         INIT_LIST_HEAD(&fbo->base.lru);
 233         fbo->base.moving = NULL;
 234         drm_vma_node_reset(&fbo->base.base.vma_node);
 235
 236         kref_init(&fbo->base.kref);
 237         fbo->base.destroy = &ttm_transfered_destroy;
 238         fbo->base.pin_count = 0;
 239         if (bo->type != ttm_bo_type_sg)
 240                 fbo->base.base.resv = &fbo->base.base._resv;
 241
 242         dma_resv_init(&fbo->base.base._resv);
 243         fbo->base.base.dev = NULL;
 244         ret = dma_resv_trylock(&fbo->base.base._resv);
 245         WARN_ON(!ret);
 246
 247         ttm_bo_move_to_lru_tail_unlocked(&fbo->base);
 248
 249         *new_obj = &fbo->base;
 250         return 0;
 251 }
 252
 253 pgprot_t ttm_io_prot(struct ttm_buffer_object *bo, struct ttm_resource *res,
 254                      pgprot_t tmp)
 255 {
 256         struct ttm_resource_manager *man;
 257         enum ttm_caching caching;
 258
 259         man = ttm_manager_type(bo->bdev, res->mem_type);
 260         caching = man->use_tt ? bo->ttm->caching : res->bus.caching;
 261
 262         return ttm_prot_from_caching(caching, tmp);
 263 }
 264 EXPORT_SYMBOL(ttm_io_prot);
 265
 266 static int ttm_bo_ioremap(struct ttm_buffer_object *bo,
 267                           unsigned long offset,
 268                           unsigned long size,
 269                           struct ttm_bo_kmap_obj *map)
 270 {
 271         struct ttm_resource *mem = bo->resource;
 272
 273         if (bo->resource->bus.addr) {
 274                 map->bo_kmap_type = ttm_bo_map_premapped;
 275                 map->virtual = ((u8 *)bo->resource->bus.addr) + offset;
 276         } else {
 277                 resource_size_t res = bo->resource->bus.offset + offset;
 278
 279                 map->bo_kmap_type = ttm_bo_map_iomap;
 280                 if (mem->bus.caching == ttm_write_combined)
 281                         map->virtual = ioremap_wc(res, size);
 282 #ifdef CONFIG_X86
 283                 else if (mem->bus.caching == ttm_cached)
 284                         map->virtual = ioremap_cache(res, size);
 285 #endif
 286                 else
 287                         map->virtual = ioremap(res, size);
 288         }
 289         return (!map->virtual) ? -ENOMEM : 0;
 290 }
 291
 292 static int ttm_bo_kmap_ttm(struct ttm_buffer_object *bo,
 293                            unsigned long start_page,
 294                            unsigned long num_pages,
 295                            struct ttm_bo_kmap_obj *map)
 296 {
 297         struct ttm_resource *mem = bo->resource;
 298         struct ttm_operation_ctx ctx = {
 299                 .interruptible = false,
 300                 .no_wait_gpu = false
 301         };
 302         struct ttm_tt *ttm = bo->ttm;
 303         pgprot_t prot;
 304         int ret;
 305
 306         BUG_ON(!ttm);
 307
 308         ret = ttm_tt_populate(bo->bdev, ttm, &ctx);
 309         if (ret)
 310                 return ret;
 311
 312         if (num_pages == 1 && ttm->caching == ttm_cached) {
 313                 /*
 314                  * We're mapping a single page, and the desired
 315                  * page protection is consistent with the bo.
 316                  */
 317
 318                 map->bo_kmap_type = ttm_bo_map_kmap;
 319                 map->page = ttm->pages[start_page];
 320                 map->virtual = kmap(map->page);
 321         } else {
 322                 /*
 323                  * We need to use vmap to get the desired page protection
 324                  * or to make the buffer object look contiguous.
 325                  */
 326                 prot = ttm_io_prot(bo, mem, PAGE_KERNEL);
 327                 map->bo_kmap_type = ttm_bo_map_vmap;
 328                 map->virtual = vmap(ttm->pages + start_page, num_pages,
 329                                     0, prot);
 330         }
 331         return (!map->virtual) ? -ENOMEM : 0;
 332 }
 333
 334 int ttm_bo_kmap(struct ttm_buffer_object *bo,
 335                 unsigned long start_page, unsigned long num_pages,
 336                 struct ttm_bo_kmap_obj *map)
 337 {
 338         unsigned long offset, size;
 339         int ret;
 340
 341         map->virtual = NULL;
 342         map->bo = bo;
 343         if (num_pages > bo->resource->num_pages)
 344                 return -EINVAL;
 345         if ((start_page + num_pages) > bo->resource->num_pages)
 346                 return -EINVAL;
 347
 348         ret = ttm_mem_io_reserve(bo->bdev, bo->resource);
 349         if (ret)
 350                 return ret;
 351         if (!bo->resource->bus.is_iomem) {
 352                 return ttm_bo_kmap_ttm(bo, start_page, num_pages, map);
 353         } else {
 354                 offset = start_page << PAGE_SHIFT;
 355                 size = num_pages << PAGE_SHIFT;
 356                 return ttm_bo_ioremap(bo, offset, size, map);
 357         }
 358 }
 359 EXPORT_SYMBOL(ttm_bo_kmap);
 360
 361 void ttm_bo_kunmap(struct ttm_bo_kmap_obj *map)
 362 {
 363         if (!map->virtual)
 364                 return;
 365         switch (map->bo_kmap_type) {
 366         case ttm_bo_map_iomap:
 367                 iounmap(map->virtual);
 368                 break;
 369         case ttm_bo_map_vmap:
 370                 vunmap(map->virtual);
 371                 break;
 372         case ttm_bo_map_kmap:
 373                 kunmap(map->page);
 374                 break;
 375         case ttm_bo_map_premapped:
 376                 break;
 377         default:
 378                 BUG();
 379         }
 380         ttm_mem_io_free(map->bo->bdev, map->bo->resource);
 381         map->virtual = NULL;
 382         map->page = NULL;
 383 }
 384 EXPORT_SYMBOL(ttm_bo_kunmap);
 385
 386 int ttm_bo_vmap(struct ttm_buffer_object *bo, struct dma_buf_map *map)
 387 {
 388         struct ttm_resource *mem = bo->resource;
 389         int ret;
 390
 391         ret = ttm_mem_io_reserve(bo->bdev, mem);
 392         if (ret)
 393                 return ret;
 394
 395         if (mem->bus.is_iomem) {
 396                 void __iomem *vaddr_iomem;
 397
 398                 if (mem->bus.addr)
 399                         vaddr_iomem = (void __iomem *)mem->bus.addr;
 400                 else if (mem->bus.caching == ttm_write_combined)
 401                         vaddr_iomem = ioremap_wc(mem->bus.offset,
 402                                                  bo->base.size);
 403 #ifdef CONFIG_X86
 404                 else if (mem->bus.caching == ttm_cached)
 405                         vaddr_iomem = ioremap_cache(mem->bus.offset,
 406                                                   bo->base.size);
 407 #endif
 408                 else
 409                         vaddr_iomem = ioremap(mem->bus.offset, bo->base.size);
 410
 411                 if (!vaddr_iomem)
 412                         return -ENOMEM;
 413
 414                 dma_buf_map_set_vaddr_iomem(map, vaddr_iomem);
 415
 416         } else {
 417                 struct ttm_operation_ctx ctx = {
 418                         .interruptible = false,
 419                         .no_wait_gpu = false
 420                 };
 421                 struct ttm_tt *ttm = bo->ttm;
 422                 pgprot_t prot;
 423                 void *vaddr;
 424
 425                 ret = ttm_tt_populate(bo->bdev, ttm, &ctx);
 426                 if (ret)
 427                         return ret;
 428
 429                 /*
 430                  * We need to use vmap to get the desired page protection
 431                  * or to make the buffer object look contiguous.
 432                  */
 433                 prot = ttm_io_prot(bo, mem, PAGE_KERNEL);
 434                 vaddr = vmap(ttm->pages, ttm->num_pages, 0, prot);
 435                 if (!vaddr)
 436                         return -ENOMEM;
 437
 438                 dma_buf_map_set_vaddr(map, vaddr);
 439         }
 440
 441         return 0;
 442 }
 443 EXPORT_SYMBOL(ttm_bo_vmap);
 444
 445 void ttm_bo_vunmap(struct ttm_buffer_object *bo, struct dma_buf_map *map)
 446 {
 447         struct ttm_resource *mem = bo->resource;
 448
 449         if (dma_buf_map_is_null(map))
 450                 return;
 451
 452         if (!map->is_iomem)
 453                 vunmap(map->vaddr);
 454         else if (!mem->bus.addr)
 455                 iounmap(map->vaddr_iomem);
 456         dma_buf_map_clear(map);
 457
 458         ttm_mem_io_free(bo->bdev, bo->resource);
 459 }
 460 EXPORT_SYMBOL(ttm_bo_vunmap);
 461
 462 static int ttm_bo_wait_free_node(struct ttm_buffer_object *bo,
 463                                  bool dst_use_tt)
 464 {
 465         int ret;
 466         ret = ttm_bo_wait(bo, false, false);
 467         if (ret)
 468                 return ret;
 469
 470         if (!dst_use_tt)
 471                 ttm_bo_tt_destroy(bo);
 472         ttm_resource_free(bo, &bo->resource);
 473         return 0;
 474 }
 475
 476 static int ttm_bo_move_to_ghost(struct ttm_buffer_object *bo,
 477                                 struct dma_fence *fence,
 478                                 bool dst_use_tt)
 479 {
 480         struct ttm_buffer_object *ghost_obj;
 481         int ret;
 482
 483         /**
 484          * This should help pipeline ordinary buffer moves.
 485          *
 486          * Hang old buffer memory on a new buffer object,
 487          * and leave it to be released when the GPU
 488          * operation has completed.
 489          */
 490
 491         dma_fence_put(bo->moving);
 492         bo->moving = dma_fence_get(fence);
 493
 494         ret = ttm_buffer_object_transfer(bo, &ghost_obj);
 495         if (ret)
 496                 return ret;
 497
 498         dma_resv_add_excl_fence(&ghost_obj->base._resv, fence);
 499
 500         /**
 501          * If we're not moving to fixed memory, the TTM object
 502          * needs to stay alive. Otherwhise hang it on the ghost
 503          * bo to be unbound and destroyed.
 504          */
 505
 506         if (dst_use_tt)
 507                 ghost_obj->ttm = NULL;
 508         else
 509                 bo->ttm = NULL;
 510         bo->resource = NULL;
 511
 512         dma_resv_unlock(&ghost_obj->base._resv);
 513         ttm_bo_put(ghost_obj);
 514         return 0;
 515 }
 516
 517 static void ttm_bo_move_pipeline_evict(struct ttm_buffer_object *bo,
 518                                        struct dma_fence *fence)
 519 {
 520         struct ttm_device *bdev = bo->bdev;
 521         struct ttm_resource_manager *from;
 522
 523         from = ttm_manager_type(bdev, bo->resource->mem_type);
 524
 525         /**
 526          * BO doesn't have a TTM we need to bind/unbind. Just remember
 527          * this eviction and free up the allocation
 528          */
 529         spin_lock(&from->move_lock);
 530         if (!from->move || dma_fence_is_later(fence, from->move)) {
 531                 dma_fence_put(from->move);
 532                 from->move = dma_fence_get(fence);
 533         }
 534         spin_unlock(&from->move_lock);
 535
 536         ttm_resource_free(bo, &bo->resource);
 537
 538         dma_fence_put(bo->moving);
 539         bo->moving = dma_fence_get(fence);
 540 }
 541
 542 int ttm_bo_move_accel_cleanup(struct ttm_buffer_object *bo,
 543                               struct dma_fence *fence,
 544                               bool evict,
 545                               bool pipeline,
 546                               struct ttm_resource *new_mem)
 547 {
 548         struct ttm_device *bdev = bo->bdev;
 549         struct ttm_resource_manager *from = ttm_manager_type(bdev, bo->resource->mem_type);
 550         struct ttm_resource_manager *man = ttm_manager_type(bdev, new_mem->mem_type);
 551         int ret = 0;
 552
 553         dma_resv_add_excl_fence(bo->base.resv, fence);
 554         if (!evict)
 555                 ret = ttm_bo_move_to_ghost(bo, fence, man->use_tt);
 556         else if (!from->use_tt && pipeline)
 557                 ttm_bo_move_pipeline_evict(bo, fence);
 558         else
 559                 ret = ttm_bo_wait_free_node(bo, man->use_tt);
 560
 561         if (ret)
 562                 return ret;
 563
 564         ttm_bo_assign_mem(bo, new_mem);
 565
 566         return 0;
 567 }
 568 EXPORT_SYMBOL(ttm_bo_move_accel_cleanup);
 569
 570 /**
 571  * ttm_bo_pipeline_gutting - purge the contents of a bo
 572  * @bo: The buffer object
 573  *
 574  * Purge the contents of a bo, async if the bo is not idle.
 575  * After a successful call, the bo is left unpopulated in
 576  * system placement. The function may wait uninterruptible
 577  * for idle on OOM.
 578  *
 579  * Return: 0 if successful, negative error code on failure.
 580  */
 581 int ttm_bo_pipeline_gutting(struct ttm_buffer_object *bo)
 582 {
 583         static const struct ttm_place sys_mem = { .mem_type = TTM_PL_SYSTEM };
 584         struct ttm_buffer_object *ghost;
 585         struct ttm_resource *sys_res;
 586         struct ttm_tt *ttm;
 587         int ret;
 588
 589         ret = ttm_resource_alloc(bo, &sys_mem, &sys_res);
 590         if (ret)
 591                 return ret;
 592
 593         /* If already idle, no need for ghost object dance. */
 594         ret = ttm_bo_wait(bo, false, true);
 595         if (ret != -EBUSY) {
 596                 if (!bo->ttm) {
 597                         /* See comment below about clearing. */
 598                         ret = ttm_tt_create(bo, true);
 599                         if (ret)
 600                                 goto error_free_sys_mem;
 601                 } else {
 602                         ttm_tt_unpopulate(bo->bdev, bo->ttm);
 603                         if (bo->type == ttm_bo_type_device)
 604                                 ttm_tt_mark_for_clear(bo->ttm);
 605                 }
 606                 ttm_resource_free(bo, &bo->resource);
 607                 ttm_bo_assign_mem(bo, sys_res);
 608                 return 0;
 609         }
 610
 611         /*
 612          * We need an unpopulated ttm_tt after giving our current one,
 613          * if any, to the ghost object. And we can't afford to fail
 614          * creating one *after* the operation. If the bo subsequently gets
 615          * resurrected, make sure it's cleared (if ttm_bo_type_device)
 616          * to avoid leaking sensitive information to user-space.
 617          */
 618
 619         ttm = bo->ttm;
 620         bo->ttm = NULL;
 621         ret = ttm_tt_create(bo, true);
 622         swap(bo->ttm, ttm);
 623         if (ret)
 624                 goto error_free_sys_mem;
 625
 626         ret = ttm_buffer_object_transfer(bo, &ghost);
 627         if (ret)
 628                 goto error_destroy_tt;
 629
 630         ret = dma_resv_copy_fences(&ghost->base._resv, bo->base.resv);
 631         /* Last resort, wait for the BO to be idle when we are OOM */
 632         if (ret)
 633                 ttm_bo_wait(bo, false, false);
 634
 635         dma_resv_unlock(&ghost->base._resv);
 636         ttm_bo_put(ghost);
 637         bo->ttm = ttm;
 638         bo->resource = NULL;
 639         ttm_bo_assign_mem(bo, sys_res);
 640         return 0;
 641
 642 error_destroy_tt:
 643         ttm_tt_destroy(bo->bdev, ttm);
 644
 645 error_free_sys_mem:
 646         ttm_resource_free(bo, &sys_res);
 647         return ret;
 648 }