drm/ttm: revert "drm/ttm: make TT creation purely optional v3"

This reverts commit 2ddef176.

As it turned out VMWGFX needs a much wider audit to fix this.
Signed-off-by: NChristian König <christian.koenig@amd.com>
Reviewed-by: NDave Airlie <airlied@redhat.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200811092400.188124-1-christian.koenig@amd.com

drivers/gpu/drm/ttm/ttm_bo.c

@@ -287,11 +287,12 @@ static int ttm_bo_handle_move_mem(struct ttm_buffer_object *bo,
 	 */
 
 	if (!(new_man->flags & TTM_MEMTYPE_FLAG_FIXED)) {
-		bool zero = !(old_man->flags & TTM_MEMTYPE_FLAG_FIXED);
-
-		ret = ttm_tt_create(bo, zero);
-		if (ret)
-			goto out_err;
+		if (bo->ttm == NULL) {
+			bool zero = !(old_man->flags & TTM_MEMTYPE_FLAG_FIXED);
+			ret = ttm_tt_create(bo, zero);
+			if (ret)
+				goto out_err;
+		}
 
 		ret = ttm_tt_set_placement_caching(bo->ttm, mem->placement);
 		if (ret)
@@ -652,8 +653,13 @@ static int ttm_bo_evict(struct ttm_buffer_object *bo,
 	placement.num_busy_placement = 0;
 	bdev->driver->evict_flags(bo, &placement);
 
-	if (!placement.num_placement && !placement.num_busy_placement)
-		return ttm_bo_pipeline_gutting(bo);
+	if (!placement.num_placement && !placement.num_busy_placement) {
+		ret = ttm_bo_pipeline_gutting(bo);
+		if (ret)
+			return ret;
+
+		return ttm_tt_create(bo, false);
+	}
 
 	evict_mem = bo->mem;
 	evict_mem.mm_node = NULL;
@@ -1192,8 +1198,13 @@ int ttm_bo_validate(struct ttm_buffer_object *bo,
 	/*
 	 * Remove the backing store if no placement is given.
 	 */
-	if (!placement->num_placement && !placement->num_busy_placement)
-		return ttm_bo_pipeline_gutting(bo);
+	if (!placement->num_placement && !placement->num_busy_placement) {
+		ret = ttm_bo_pipeline_gutting(bo);
+		if (ret)
+			return ret;
+
+		return ttm_tt_create(bo, false);
+	}
 
 	/*
 	 * Check whether we need to move buffer.
@@ -1210,6 +1221,14 @@ int ttm_bo_validate(struct ttm_buffer_object *bo,
 		ttm_flag_masked(&bo->mem.placement, new_flags,
 				~TTM_PL_MASK_MEMTYPE);
 	}
+	/*
+	 * We might need to add a TTM.
+	 */
+	if (bo->mem.mem_type == TTM_PL_SYSTEM && bo->ttm == NULL) {
+		ret = ttm_tt_create(bo, true);
+		if (ret)
+			return ret;
+	}
 	return 0;
 }
 EXPORT_SYMBOL(ttm_bo_validate);

drivers/gpu/drm/ttm/ttm_bo_util.c

@@ -531,15 +531,12 @@ static int ttm_bo_kmap_ttm(struct ttm_buffer_object *bo,
 		.interruptible = false,
 		.no_wait_gpu = false
 	};
-	struct ttm_tt *ttm;
+	struct ttm_tt *ttm = bo->ttm;
 	pgprot_t prot;
 	int ret;
 
-	ret = ttm_tt_create(bo, true);
-	if (ret)
-		return ret;
+	BUG_ON(!ttm);
 
-	ttm = bo->ttm;
 	ret = ttm_tt_populate(ttm, &ctx);
 	if (ret)
 		return ret;

drivers/gpu/drm/ttm/ttm_bo_vm.c

@@ -351,11 +351,6 @@ vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf,
 
 		};
 
-		if (ttm_tt_create(bo, true)) {
-			ret = VM_FAULT_OOM;
-			goto out_io_unlock;
-		}
-
 		ttm = bo->ttm;
 		if (ttm_tt_populate(bo->ttm, &ctx)) {
 			ret = VM_FAULT_OOM;

drivers/gpu/drm/ttm/ttm_tt.c

@@ -50,9 +50,6 @@ int ttm_tt_create(struct ttm_buffer_object *bo, bool zero_alloc)
 
 	dma_resv_assert_held(bo->base.resv);
 
-	if (bo->ttm)
-		return 0;
-
 	if (bdev->need_dma32)
 		page_flags |= TTM_PAGE_FLAG_DMA32;
 
@@ -70,6 +67,7 @@ int ttm_tt_create(struct ttm_buffer_object *bo, bool zero_alloc)
 		page_flags |= TTM_PAGE_FLAG_SG;
 		break;
 	default:
+		bo->ttm = NULL;
 		pr_err("Illegal buffer object type\n");
 		return -EINVAL;
 	}