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/iosys-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)
  67                 return;
  68
  69         if (!mem->bus.offset && !mem->bus.addr)
  70                 return;
  71
  72         if (bdev->funcs->io_mem_free)
  73                 bdev->funcs->io_mem_free(bdev, mem);
  74
  75         mem->bus.offset = 0;
  76         mem->bus.addr = NULL;
  77 }
  78
  79 /**
  80  * ttm_move_memcpy - Helper to perform a memcpy ttm move operation.
  81  * @clear: Whether to clear rather than copy.
  82  * @num_pages: Number of pages of the operation.
  83  * @dst_iter: A struct ttm_kmap_iter representing the destination resource.
  84  * @src_iter: A struct ttm_kmap_iter representing the source resource.
  85  *
  86  * This function is intended to be able to move out async under a
  87  * dma-fence if desired.
  88  */
  89 void ttm_move_memcpy(bool clear,
  90                      u32 num_pages,
  91                      struct ttm_kmap_iter *dst_iter,
  92                      struct ttm_kmap_iter *src_iter)
  93 {
  94         const struct ttm_kmap_iter_ops *dst_ops = dst_iter->ops;
  95         const struct ttm_kmap_iter_ops *src_ops = src_iter->ops;
  96         struct iosys_map src_map, dst_map;
  97         pgoff_t i;
  98
  99         /* Single TTM move. NOP */
 100         if (dst_ops->maps_tt && src_ops->maps_tt)
 101                 return;
 102
 103         /* Don't move nonexistent data. Clear destination instead. */
 104         if (clear) {
 105                 for (i = 0; i < num_pages; ++i) {
 106                         dst_ops->map_local(dst_iter, &dst_map, i);
 107                         if (dst_map.is_iomem)
 108                                 memset_io(dst_map.vaddr_iomem, 0, PAGE_SIZE);
 109                         else
 110                                 memset(dst_map.vaddr, 0, PAGE_SIZE);
 111                         if (dst_ops->unmap_local)
 112                                 dst_ops->unmap_local(dst_iter, &dst_map);
 113                 }
 114                 return;
 115         }
 116
 117         for (i = 0; i < num_pages; ++i) {
 118                 dst_ops->map_local(dst_iter, &dst_map, i);
 119                 src_ops->map_local(src_iter, &src_map, i);
 120
 121                 drm_memcpy_from_wc(&dst_map, &src_map, PAGE_SIZE);
 122
 123                 if (src_ops->unmap_local)
 124                         src_ops->unmap_local(src_iter, &src_map);
 125                 if (dst_ops->unmap_local)
 126                         dst_ops->unmap_local(dst_iter, &dst_map);
 127         }
 128 }
 129 EXPORT_SYMBOL(ttm_move_memcpy);
 130
 131 int ttm_bo_move_memcpy(struct ttm_buffer_object *bo,
 132                        struct ttm_operation_ctx *ctx,
 133                        struct ttm_resource *dst_mem)
 134 {
 135         struct ttm_device *bdev = bo->bdev;
 136         struct ttm_resource_manager *dst_man =
 137                 ttm_manager_type(bo->bdev, dst_mem->mem_type);
 138         struct ttm_tt *ttm = bo->ttm;
 139         struct ttm_resource *src_mem = bo->resource;
 140         struct ttm_resource_manager *src_man;
 141         union {
 142                 struct ttm_kmap_iter_tt tt;
 143                 struct ttm_kmap_iter_linear_io io;
 144         } _dst_iter, _src_iter;
 145         struct ttm_kmap_iter *dst_iter, *src_iter;
 146         bool clear;
 147         int ret = 0;
 148
 149         if (!src_mem)
 150                 return 0;
 151
 152         src_man = ttm_manager_type(bdev, src_mem->mem_type);
 153         if (ttm && ((ttm->page_flags & TTM_TT_FLAG_SWAPPED) ||
 154                     dst_man->use_tt)) {
 155                 ret = ttm_tt_populate(bdev, ttm, ctx);
 156                 if (ret)
 157                         return ret;
 158         }
 159
 160         dst_iter = ttm_kmap_iter_linear_io_init(&_dst_iter.io, bdev, dst_mem);
 161         if (PTR_ERR(dst_iter) == -EINVAL && dst_man->use_tt)
 162                 dst_iter = ttm_kmap_iter_tt_init(&_dst_iter.tt, bo->ttm);
 163         if (IS_ERR(dst_iter))
 164                 return PTR_ERR(dst_iter);
 165
 166         src_iter = ttm_kmap_iter_linear_io_init(&_src_iter.io, bdev, src_mem);
 167         if (PTR_ERR(src_iter) == -EINVAL && src_man->use_tt)
 168                 src_iter = ttm_kmap_iter_tt_init(&_src_iter.tt, bo->ttm);
 169         if (IS_ERR(src_iter)) {
 170                 ret = PTR_ERR(src_iter);
 171                 goto out_src_iter;
 172         }
 173
 174         clear = src_iter->ops->maps_tt && (!ttm || !ttm_tt_is_populated(ttm));
 175         if (!(clear && ttm && !(ttm->page_flags & TTM_TT_FLAG_ZERO_ALLOC)))
 176                 ttm_move_memcpy(clear, ttm->num_pages, dst_iter, src_iter);
 177
 178         if (!src_iter->ops->maps_tt)
 179                 ttm_kmap_iter_linear_io_fini(&_src_iter.io, bdev, src_mem);
 180         ttm_bo_move_sync_cleanup(bo, dst_mem);
 181
 182 out_src_iter:
 183         if (!dst_iter->ops->maps_tt)
 184                 ttm_kmap_iter_linear_io_fini(&_dst_iter.io, bdev, dst_mem);
 185
 186         return ret;
 187 }
 188 EXPORT_SYMBOL(ttm_bo_move_memcpy);
 189
 190 static void ttm_transfered_destroy(struct ttm_buffer_object *bo)
 191 {
 192         struct ttm_transfer_obj *fbo;
 193
 194         fbo = container_of(bo, struct ttm_transfer_obj, base);
 195         dma_resv_fini(&fbo->base.base._resv);
 196         ttm_bo_put(fbo->bo);
 197         kfree(fbo);
 198 }
 199
 200 /**
 201  * ttm_buffer_object_transfer
 202  *
 203  * @bo: A pointer to a struct ttm_buffer_object.
 204  * @new_obj: A pointer to a pointer to a newly created ttm_buffer_object,
 205  * holding the data of @bo with the old placement.
 206  *
 207  * This is a utility function that may be called after an accelerated move
 208  * has been scheduled. A new buffer object is created as a placeholder for
 209  * the old data while it's being copied. When that buffer object is idle,
 210  * it can be destroyed, releasing the space of the old placement.
 211  * Returns:
 212  * !0: Failure.
 213  */
 214
 215 static int ttm_buffer_object_transfer(struct ttm_buffer_object *bo,
 216                                       struct ttm_buffer_object **new_obj)
 217 {
 218         struct ttm_transfer_obj *fbo;
 219         int ret;
 220
 221         fbo = kmalloc(sizeof(*fbo), GFP_KERNEL);
 222         if (!fbo)
 223                 return -ENOMEM;
 224
 225         fbo->base = *bo;
 226
 227         /**
 228          * Fix up members that we shouldn't copy directly:
 229          * TODO: Explicit member copy would probably be better here.
 230          */
 231
 232         atomic_inc(&ttm_glob.bo_count);
 233         INIT_LIST_HEAD(&fbo->base.ddestroy);
 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         if (fbo->base.resource) {
 248                 ttm_resource_set_bo(fbo->base.resource, &fbo->base);
 249                 bo->resource = NULL;
 250                 ttm_bo_set_bulk_move(&fbo->base, NULL);
 251         } else {
 252                 fbo->base.bulk_move = NULL;
 253         }
 254
 255         ret = dma_resv_reserve_fences(&fbo->base.base._resv, 1);
 256         if (ret) {
 257                 kfree(fbo);
 258                 return ret;
 259         }
 260
 261         ttm_bo_get(bo);
 262         fbo->bo = bo;
 263
 264         ttm_bo_move_to_lru_tail_unlocked(&fbo->base);
 265
 266         *new_obj = &fbo->base;
 267         return 0;
 268 }
 269
 270 pgprot_t ttm_io_prot(struct ttm_buffer_object *bo, struct ttm_resource *res,
 271                      pgprot_t tmp)
 272 {
 273         struct ttm_resource_manager *man;
 274         enum ttm_caching caching;
 275
 276         man = ttm_manager_type(bo->bdev, res->mem_type);
 277         caching = man->use_tt ? bo->ttm->caching : res->bus.caching;
 278
 279         return ttm_prot_from_caching(caching, tmp);
 280 }
 281 EXPORT_SYMBOL(ttm_io_prot);
 282
 283 static int ttm_bo_ioremap(struct ttm_buffer_object *bo,
 284                           unsigned long offset,
 285                           unsigned long size,
 286                           struct ttm_bo_kmap_obj *map)
 287 {
 288         struct ttm_resource *mem = bo->resource;
 289
 290         if (bo->resource->bus.addr) {
 291                 map->bo_kmap_type = ttm_bo_map_premapped;
 292                 map->virtual = ((u8 *)bo->resource->bus.addr) + offset;
 293         } else {
 294                 resource_size_t res = bo->resource->bus.offset + offset;
 295
 296                 map->bo_kmap_type = ttm_bo_map_iomap;
 297                 if (mem->bus.caching == ttm_write_combined)
 298                         map->virtual = ioremap_wc(res, size);
 299 #ifdef CONFIG_X86
 300                 else if (mem->bus.caching == ttm_cached)
 301                         map->virtual = ioremap_cache(res, size);
 302 #endif
 303                 else
 304                         map->virtual = ioremap(res, size);
 305         }
 306         return (!map->virtual) ? -ENOMEM : 0;
 307 }
 308
 309 static int ttm_bo_kmap_ttm(struct ttm_buffer_object *bo,
 310                            unsigned long start_page,
 311                            unsigned long num_pages,
 312                            struct ttm_bo_kmap_obj *map)
 313 {
 314         struct ttm_resource *mem = bo->resource;
 315         struct ttm_operation_ctx ctx = {
 316                 .interruptible = false,
 317                 .no_wait_gpu = false
 318         };
 319         struct ttm_tt *ttm = bo->ttm;
 320         pgprot_t prot;
 321         int ret;
 322
 323         BUG_ON(!ttm);
 324
 325         ret = ttm_tt_populate(bo->bdev, ttm, &ctx);
 326         if (ret)
 327                 return ret;
 328
 329         if (num_pages == 1 && ttm->caching == ttm_cached) {
 330                 /*
 331                  * We're mapping a single page, and the desired
 332                  * page protection is consistent with the bo.
 333                  */
 334
 335                 map->bo_kmap_type = ttm_bo_map_kmap;
 336                 map->page = ttm->pages[start_page];
 337                 map->virtual = kmap(map->page);
 338         } else {
 339                 /*
 340                  * We need to use vmap to get the desired page protection
 341                  * or to make the buffer object look contiguous.
 342                  */
 343                 prot = ttm_io_prot(bo, mem, PAGE_KERNEL);
 344                 map->bo_kmap_type = ttm_bo_map_vmap;
 345                 map->virtual = vmap(ttm->pages + start_page, num_pages,
 346                                     0, prot);
 347         }
 348         return (!map->virtual) ? -ENOMEM : 0;
 349 }
 350
 351 int ttm_bo_kmap(struct ttm_buffer_object *bo,
 352                 unsigned long start_page, unsigned long num_pages,
 353                 struct ttm_bo_kmap_obj *map)
 354 {
 355         unsigned long offset, size;
 356         int ret;
 357
 358         map->virtual = NULL;
 359         map->bo = bo;
 360         if (num_pages > PFN_UP(bo->resource->size))
 361                 return -EINVAL;
 362         if ((start_page + num_pages) > PFN_UP(bo->resource->size))
 363                 return -EINVAL;
 364
 365         ret = ttm_mem_io_reserve(bo->bdev, bo->resource);
 366         if (ret)
 367                 return ret;
 368         if (!bo->resource->bus.is_iomem) {
 369                 return ttm_bo_kmap_ttm(bo, start_page, num_pages, map);
 370         } else {
 371                 offset = start_page << PAGE_SHIFT;
 372                 size = num_pages << PAGE_SHIFT;
 373                 return ttm_bo_ioremap(bo, offset, size, map);
 374         }
 375 }
 376 EXPORT_SYMBOL(ttm_bo_kmap);
 377
 378 void ttm_bo_kunmap(struct ttm_bo_kmap_obj *map)
 379 {
 380         if (!map->virtual)
 381                 return;
 382         switch (map->bo_kmap_type) {
 383         case ttm_bo_map_iomap:
 384                 iounmap(map->virtual);
 385                 break;
 386         case ttm_bo_map_vmap:
 387                 vunmap(map->virtual);
 388                 break;
 389         case ttm_bo_map_kmap:
 390                 kunmap(map->page);
 391                 break;
 392         case ttm_bo_map_premapped:
 393                 break;
 394         default:
 395                 BUG();
 396         }
 397         ttm_mem_io_free(map->bo->bdev, map->bo->resource);
 398         map->virtual = NULL;
 399         map->page = NULL;
 400 }
 401 EXPORT_SYMBOL(ttm_bo_kunmap);
 402
 403 int ttm_bo_vmap(struct ttm_buffer_object *bo, struct iosys_map *map)
 404 {
 405         struct ttm_resource *mem = bo->resource;
 406         int ret;
 407
 408         dma_resv_assert_held(bo->base.resv);
 409
 410         ret = ttm_mem_io_reserve(bo->bdev, mem);
 411         if (ret)
 412                 return ret;
 413
 414         if (mem->bus.is_iomem) {
 415                 void __iomem *vaddr_iomem;
 416
 417                 if (mem->bus.addr)
 418                         vaddr_iomem = (void __iomem *)mem->bus.addr;
 419                 else if (mem->bus.caching == ttm_write_combined)
 420                         vaddr_iomem = ioremap_wc(mem->bus.offset,
 421                                                  bo->base.size);
 422 #ifdef CONFIG_X86
 423                 else if (mem->bus.caching == ttm_cached)
 424                         vaddr_iomem = ioremap_cache(mem->bus.offset,
 425                                                   bo->base.size);
 426 #endif
 427                 else
 428                         vaddr_iomem = ioremap(mem->bus.offset, bo->base.size);
 429
 430                 if (!vaddr_iomem)
 431                         return -ENOMEM;
 432
 433                 iosys_map_set_vaddr_iomem(map, vaddr_iomem);
 434
 435         } else {
 436                 struct ttm_operation_ctx ctx = {
 437                         .interruptible = false,
 438                         .no_wait_gpu = false
 439                 };
 440                 struct ttm_tt *ttm = bo->ttm;
 441                 pgprot_t prot;
 442                 void *vaddr;
 443
 444                 ret = ttm_tt_populate(bo->bdev, ttm, &ctx);
 445                 if (ret)
 446                         return ret;
 447
 448                 /*
 449                  * We need to use vmap to get the desired page protection
 450                  * or to make the buffer object look contiguous.
 451                  */
 452                 prot = ttm_io_prot(bo, mem, PAGE_KERNEL);
 453                 vaddr = vmap(ttm->pages, ttm->num_pages, 0, prot);
 454                 if (!vaddr)
 455                         return -ENOMEM;
 456
 457                 iosys_map_set_vaddr(map, vaddr);
 458         }
 459
 460         return 0;
 461 }
 462 EXPORT_SYMBOL(ttm_bo_vmap);
 463
 464 void ttm_bo_vunmap(struct ttm_buffer_object *bo, struct iosys_map *map)
 465 {
 466         struct ttm_resource *mem = bo->resource;
 467
 468         dma_resv_assert_held(bo->base.resv);
 469
 470         if (iosys_map_is_null(map))
 471                 return;
 472
 473         if (!map->is_iomem)
 474                 vunmap(map->vaddr);
 475         else if (!mem->bus.addr)
 476                 iounmap(map->vaddr_iomem);
 477         iosys_map_clear(map);
 478
 479         ttm_mem_io_free(bo->bdev, bo->resource);
 480 }
 481 EXPORT_SYMBOL(ttm_bo_vunmap);
 482
 483 static int ttm_bo_wait_free_node(struct ttm_buffer_object *bo,
 484                                  bool dst_use_tt)
 485 {
 486         int ret;
 487         ret = ttm_bo_wait(bo, false, false);
 488         if (ret)
 489                 return ret;
 490
 491         if (!dst_use_tt)
 492                 ttm_bo_tt_destroy(bo);
 493         ttm_resource_free(bo, &bo->resource);
 494         return 0;
 495 }
 496
 497 static int ttm_bo_move_to_ghost(struct ttm_buffer_object *bo,
 498                                 struct dma_fence *fence,
 499                                 bool dst_use_tt)
 500 {
 501         struct ttm_buffer_object *ghost_obj;
 502         int ret;
 503
 504         /**
 505          * This should help pipeline ordinary buffer moves.
 506          *
 507          * Hang old buffer memory on a new buffer object,
 508          * and leave it to be released when the GPU
 509          * operation has completed.
 510          */
 511
 512         ret = ttm_buffer_object_transfer(bo, &ghost_obj);
 513         if (ret)
 514                 return ret;
 515
 516         dma_resv_add_fence(&ghost_obj->base._resv, fence,
 517                            DMA_RESV_USAGE_KERNEL);
 518
 519         /**
 520          * If we're not moving to fixed memory, the TTM object
 521          * needs to stay alive. Otherwhise hang it on the ghost
 522          * bo to be unbound and destroyed.
 523          */
 524
 525         if (dst_use_tt)
 526                 ghost_obj->ttm = NULL;
 527         else
 528                 bo->ttm = NULL;
 529
 530         dma_resv_unlock(&ghost_obj->base._resv);
 531         ttm_bo_put(ghost_obj);
 532         return 0;
 533 }
 534
 535 static void ttm_bo_move_pipeline_evict(struct ttm_buffer_object *bo,
 536                                        struct dma_fence *fence)
 537 {
 538         struct ttm_device *bdev = bo->bdev;
 539         struct ttm_resource_manager *from;
 540
 541         from = ttm_manager_type(bdev, bo->resource->mem_type);
 542
 543         /**
 544          * BO doesn't have a TTM we need to bind/unbind. Just remember
 545          * this eviction and free up the allocation
 546          */
 547         spin_lock(&from->move_lock);
 548         if (!from->move || dma_fence_is_later(fence, from->move)) {
 549                 dma_fence_put(from->move);
 550                 from->move = dma_fence_get(fence);
 551         }
 552         spin_unlock(&from->move_lock);
 553
 554         ttm_resource_free(bo, &bo->resource);
 555 }
 556
 557 int ttm_bo_move_accel_cleanup(struct ttm_buffer_object *bo,
 558                               struct dma_fence *fence,
 559                               bool evict,
 560                               bool pipeline,
 561                               struct ttm_resource *new_mem)
 562 {
 563         struct ttm_device *bdev = bo->bdev;
 564         struct ttm_resource_manager *from = ttm_manager_type(bdev, bo->resource->mem_type);
 565         struct ttm_resource_manager *man = ttm_manager_type(bdev, new_mem->mem_type);
 566         int ret = 0;
 567
 568         dma_resv_add_fence(bo->base.resv, fence, DMA_RESV_USAGE_KERNEL);
 569         if (!evict)
 570                 ret = ttm_bo_move_to_ghost(bo, fence, man->use_tt);
 571         else if (!from->use_tt && pipeline)
 572                 ttm_bo_move_pipeline_evict(bo, fence);
 573         else
 574                 ret = ttm_bo_wait_free_node(bo, man->use_tt);
 575
 576         if (ret)
 577                 return ret;
 578
 579         ttm_bo_assign_mem(bo, new_mem);
 580
 581         return 0;
 582 }
 583 EXPORT_SYMBOL(ttm_bo_move_accel_cleanup);
 584
 585 void ttm_bo_move_sync_cleanup(struct ttm_buffer_object *bo,
 586                               struct ttm_resource *new_mem)
 587 {
 588         struct ttm_device *bdev = bo->bdev;
 589         struct ttm_resource_manager *man = ttm_manager_type(bdev, new_mem->mem_type);
 590         int ret;
 591
 592         ret = ttm_bo_wait_free_node(bo, man->use_tt);
 593         if (WARN_ON(ret))
 594                 return;
 595
 596         ttm_bo_assign_mem(bo, new_mem);
 597 }
 598 EXPORT_SYMBOL(ttm_bo_move_sync_cleanup);
 599
 600 /**
 601  * ttm_bo_pipeline_gutting - purge the contents of a bo
 602  * @bo: The buffer object
 603  *
 604  * Purge the contents of a bo, async if the bo is not idle.
 605  * After a successful call, the bo is left unpopulated in
 606  * system placement. The function may wait uninterruptible
 607  * for idle on OOM.
 608  *
 609  * Return: 0 if successful, negative error code on failure.
 610  */
 611 int ttm_bo_pipeline_gutting(struct ttm_buffer_object *bo)
 612 {
 613         static const struct ttm_place sys_mem = { .mem_type = TTM_PL_SYSTEM };
 614         struct ttm_buffer_object *ghost;
 615         struct ttm_resource *sys_res;
 616         struct ttm_tt *ttm;
 617         int ret;
 618
 619         ret = ttm_resource_alloc(bo, &sys_mem, &sys_res);
 620         if (ret)
 621                 return ret;
 622
 623         /* If already idle, no need for ghost object dance. */
 624         ret = ttm_bo_wait(bo, false, true);
 625         if (ret != -EBUSY) {
 626                 if (!bo->ttm) {
 627                         /* See comment below about clearing. */
 628                         ret = ttm_tt_create(bo, true);
 629                         if (ret)
 630                                 goto error_free_sys_mem;
 631                 } else {
 632                         ttm_tt_unpopulate(bo->bdev, bo->ttm);
 633                         if (bo->type == ttm_bo_type_device)
 634                                 ttm_tt_mark_for_clear(bo->ttm);
 635                 }
 636                 ttm_resource_free(bo, &bo->resource);
 637                 ttm_bo_assign_mem(bo, sys_res);
 638                 return 0;
 639         }
 640
 641         /*
 642          * We need an unpopulated ttm_tt after giving our current one,
 643          * if any, to the ghost object. And we can't afford to fail
 644          * creating one *after* the operation. If the bo subsequently gets
 645          * resurrected, make sure it's cleared (if ttm_bo_type_device)
 646          * to avoid leaking sensitive information to user-space.
 647          */
 648
 649         ttm = bo->ttm;
 650         bo->ttm = NULL;
 651         ret = ttm_tt_create(bo, true);
 652         swap(bo->ttm, ttm);
 653         if (ret)
 654                 goto error_free_sys_mem;
 655
 656         ret = ttm_buffer_object_transfer(bo, &ghost);
 657         if (ret)
 658                 goto error_destroy_tt;
 659
 660         ret = dma_resv_copy_fences(&ghost->base._resv, bo->base.resv);
 661         /* Last resort, wait for the BO to be idle when we are OOM */
 662         if (ret)
 663                 ttm_bo_wait(bo, false, false);
 664
 665         dma_resv_unlock(&ghost->base._resv);
 666         ttm_bo_put(ghost);
 667         bo->ttm = ttm;
 668         ttm_bo_assign_mem(bo, sys_res);
 669         return 0;
 670
 671 error_destroy_tt:
 672         ttm_tt_destroy(bo->bdev, ttm);
 673
 674 error_free_sys_mem:
 675         ttm_resource_free(bo, &sys_res);
 676         return ret;
 677 }