[PATCH 3/3] drm/ttm: avoid multihop moves in drivers.

[Dave Airlie <airlied@gmail.com>]

From: Dave Airlie <airlied@redhat.com>

Currently drivers get called to move a buffer, but if they have to
move it temporarily through another space (SYSTEM->VRAM via TT)
then they can end up with a lot of ttm->driver->ttm call stacks,
if the temprorary space moves requires eviction.

Instead of letting the driver do all the placement/space for the
temporary, allow it to report back (-EMULTIHOP) a placement (hop)
to the move code, which will then do the temporary move, and the
correct placement move afterwards.

This removes a lot of code from drivers, at the expense of
adding some midlayering. I've some further ideas on how to turn
it inside out, but I think this is a good solution to the call
stack problems.

Signed-off-by: Dave Airlie <airlied@redhat.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c    | 139 +++------------------
 drivers/gpu/drm/drm_gem_vram_helper.c      |   3 +-
 drivers/gpu/drm/nouveau/nouveau_bo.c       | 115 +++--------------
 drivers/gpu/drm/qxl/qxl_ttm.c              |   3 +-
 drivers/gpu/drm/radeon/radeon_ttm.c        | 122 +++---------------
 drivers/gpu/drm/ttm/ttm_bo.c               |  62 +++++++--
 drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c |   3 +-
 include/drm/ttm/ttm_bo_driver.h            |   5 +-
 8 files changed, 108 insertions(+), 344 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 62f9194b1dd1..0fd4f270d794 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -515,119 +515,6 @@ static int amdgpu_move_blit(struct ttm_buffer_object *bo,
 	return r;
 }
 
-/**
- * amdgpu_move_vram_ram - Copy VRAM buffer to RAM buffer
- *
- * Called by amdgpu_bo_move().
- */
-static int amdgpu_move_vram_ram(struct ttm_buffer_object *bo, bool evict,
-				struct ttm_operation_ctx *ctx,
-				struct ttm_resource *new_mem)
-{
-	struct ttm_resource *old_mem = &bo->mem;
-	struct ttm_resource tmp_mem;
-	struct ttm_place placements;
-	struct ttm_placement placement;
-	int r;
-
-	/* create space/pages for new_mem in GTT space */
-	tmp_mem = *new_mem;
-	tmp_mem.mm_node = NULL;
-	placement.num_placement = 1;
-	placement.placement = &placements;
-	placement.num_busy_placement = 1;
-	placement.busy_placement = &placements;
-	placements.fpfn = 0;
-	placements.lpfn = 0;
-	placements.mem_type = TTM_PL_TT;
-	placements.flags = 0;
-	r = ttm_bo_mem_space(bo, &placement, &tmp_mem, ctx);
-	if (unlikely(r)) {
-		pr_err("Failed to find GTT space for blit from VRAM\n");
-		return r;
-	}
-
-	r = ttm_tt_populate(bo->bdev, bo->ttm, ctx);
-	if (unlikely(r))
-		goto out_cleanup;
-
-	/* Bind the memory to the GTT space */
-	r = amdgpu_ttm_backend_bind(bo->bdev, bo->ttm, &tmp_mem);
-	if (unlikely(r)) {
-		goto out_cleanup;
-	}
-
-	/* blit VRAM to GTT */
-	r = amdgpu_move_blit(bo, evict, &tmp_mem, old_mem);
-	if (unlikely(r)) {
-		goto out_cleanup;
-	}
-
-	r = ttm_bo_wait_ctx(bo, ctx);
-	if (unlikely(r))
-		goto out_cleanup;
-
-	amdgpu_ttm_backend_unbind(bo->bdev, bo->ttm);
-	ttm_resource_free(bo, &bo->mem);
-	ttm_bo_assign_mem(bo, new_mem);
-out_cleanup:
-	ttm_resource_free(bo, &tmp_mem);
-	return r;
-}
-
-/**
- * amdgpu_move_ram_vram - Copy buffer from RAM to VRAM
- *
- * Called by amdgpu_bo_move().
- */
-static int amdgpu_move_ram_vram(struct ttm_buffer_object *bo, bool evict,
-				struct ttm_operation_ctx *ctx,
-				struct ttm_resource *new_mem)
-{
-	struct ttm_resource *old_mem = &bo->mem;
-	struct ttm_resource tmp_mem;
-	struct ttm_placement placement;
-	struct ttm_place placements;
-	int r;
-
-	/* make space in GTT for old_mem buffer */
-	tmp_mem = *new_mem;
-	tmp_mem.mm_node = NULL;
-	placement.num_placement = 1;
-	placement.placement = &placements;
-	placement.num_busy_placement = 1;
-	placement.busy_placement = &placements;
-	placements.fpfn = 0;
-	placements.lpfn = 0;
-	placements.mem_type = TTM_PL_TT;
-	placements.flags = 0;
-	r = ttm_bo_mem_space(bo, &placement, &tmp_mem, ctx);
-	if (unlikely(r)) {
-		pr_err("Failed to find GTT space for blit to VRAM\n");
-		return r;
-	}
-
-	/* move/bind old memory to GTT space */
-	r = ttm_tt_populate(bo->bdev, bo->ttm, ctx);
-	if (unlikely(r))
-		return r;
-
-	r = amdgpu_ttm_backend_bind(bo->bdev, bo->ttm, &tmp_mem);
-	if (unlikely(r)) {
-		goto out_cleanup;
-	}
-
-	ttm_bo_assign_mem(bo, &tmp_mem);
-	/* copy to VRAM */
-	r = amdgpu_move_blit(bo, evict, new_mem, old_mem);
-	if (unlikely(r)) {
-		goto out_cleanup;
-	}
-out_cleanup:
-	ttm_resource_free(bo, &tmp_mem);
-	return r;
-}
-
 /**
  * amdgpu_mem_visible - Check that memory can be accessed by ttm_bo_move_memcpy
  *
@@ -659,13 +546,25 @@ static bool amdgpu_mem_visible(struct amdgpu_device *adev,
  */
 static int amdgpu_bo_move(struct ttm_buffer_object *bo, bool evict,
 			  struct ttm_operation_ctx *ctx,
-			  struct ttm_resource *new_mem)
+			  struct ttm_resource *new_mem,
+			  struct ttm_place *hop)
 {
 	struct amdgpu_device *adev;
 	struct amdgpu_bo *abo;
 	struct ttm_resource *old_mem = &bo->mem;
 	int r;
 
+	if ((old_mem->mem_type == TTM_PL_SYSTEM &&
+	     new_mem->mem_type == TTM_PL_VRAM) ||
+	    (old_mem->mem_type == TTM_PL_VRAM &&
+	     new_mem->mem_type == TTM_PL_SYSTEM)) {
+		hop->fpfn = 0;
+		hop->lpfn = 0;
+		hop->mem_type = TTM_PL_TT;
+		hop->flags = 0;
+		return -EMULTIHOP;
+	}
+
 	if (new_mem->mem_type == TTM_PL_TT) {
 		r = amdgpu_ttm_backend_bind(bo->bdev, bo->ttm, new_mem);
 		if (r)
@@ -719,16 +618,8 @@ static int amdgpu_bo_move(struct ttm_buffer_object *bo, bool evict,
 		goto memcpy;
 	}
 
-	if (old_mem->mem_type == TTM_PL_VRAM &&
-	    new_mem->mem_type == TTM_PL_SYSTEM) {
-		r = amdgpu_move_vram_ram(bo, evict, ctx, new_mem);
-	} else if (old_mem->mem_type == TTM_PL_SYSTEM &&
-		   new_mem->mem_type == TTM_PL_VRAM) {
-		r = amdgpu_move_ram_vram(bo, evict, ctx, new_mem);
-	} else {
-		r = amdgpu_move_blit(bo, evict,
-				     new_mem, old_mem);
-	}
+	r = amdgpu_move_blit(bo, evict,
+			     new_mem, old_mem);
 
 	if (r) {
 memcpy:
diff --git a/drivers/gpu/drm/drm_gem_vram_helper.c b/drivers/gpu/drm/drm_gem_vram_helper.c
index 9da823eb0edd..c51096cc7fb2 100644
--- a/drivers/gpu/drm/drm_gem_vram_helper.c
+++ b/drivers/gpu/drm/drm_gem_vram_helper.c
@@ -965,7 +965,8 @@ static void bo_driver_delete_mem_notify(struct ttm_buffer_object *bo)
 static int bo_driver_move(struct ttm_buffer_object *bo,
 			  bool evict,
 			  struct ttm_operation_ctx *ctx,
-			  struct ttm_resource *new_mem)
+			  struct ttm_resource *new_mem,
+			  struct ttm_place *hop)
 {
 	struct drm_gem_vram_object *gbo;
 
diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c
index acff82afe260..623577412d19 100644
--- a/drivers/gpu/drm/nouveau/nouveau_bo.c
+++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
@@ -862,96 +862,6 @@ nouveau_bo_move_init(struct nouveau_drm *drm)
 	NV_INFO(drm, "MM: using %s for buffer copies\n", name);
 }
 
-static int
-nouveau_bo_move_flipd(struct ttm_buffer_object *bo, bool evict,
-		      struct ttm_operation_ctx *ctx,
-		      struct ttm_resource *new_reg)
-{
-	struct ttm_place placement_memtype = {
-		.fpfn = 0,
-		.lpfn = 0,
-		.mem_type = TTM_PL_TT,
-		.flags = 0
-	};
-	struct ttm_placement placement;
-	struct ttm_resource tmp_reg;
-	int ret;
-
-	placement.num_placement = placement.num_busy_placement = 1;
-	placement.placement = placement.busy_placement = &placement_memtype;
-
-	tmp_reg = *new_reg;
-	tmp_reg.mm_node = NULL;
-	ret = ttm_bo_mem_space(bo, &placement, &tmp_reg, ctx);
-	if (ret)
-		return ret;
-
-	ret = ttm_tt_populate(bo->bdev, bo->ttm, ctx);
-	if (ret)
-		goto out;
-
-	ret = nouveau_ttm_tt_bind(bo->bdev, bo->ttm, &tmp_reg);
-	if (ret)
-		goto out;
-
-	ret = nouveau_bo_move_m2mf(bo, true, ctx, &tmp_reg);
-	if (ret)
-		goto out;
-
-	ret = ttm_bo_wait_ctx(bo, ctx);
-	if (ret)
-		goto out;
-
-	nouveau_ttm_tt_unbind(bo->bdev, bo->ttm);
-	ttm_resource_free(bo, &bo->mem);
-	ttm_bo_assign_mem(bo, &tmp_reg);
-out:
-	ttm_resource_free(bo, &tmp_reg);
-	return ret;
-}
-
-static int
-nouveau_bo_move_flips(struct ttm_buffer_object *bo, bool evict,
-		      struct ttm_operation_ctx *ctx,
-		      struct ttm_resource *new_reg)
-{
-	struct ttm_place placement_memtype = {
-		.fpfn = 0,
-		.lpfn = 0,
-		.mem_type = TTM_PL_TT,
-		.flags = 0
-	};
-	struct ttm_placement placement;
-	struct ttm_resource tmp_reg;
-	int ret;
-
-	placement.num_placement = placement.num_busy_placement = 1;
-	placement.placement = placement.busy_placement = &placement_memtype;
-
-	tmp_reg = *new_reg;
-	tmp_reg.mm_node = NULL;
-	ret = ttm_bo_mem_space(bo, &placement, &tmp_reg, ctx);
-	if (ret)
-		return ret;
-
-	ret = ttm_tt_populate(bo->bdev, bo->ttm, ctx);
-	if (unlikely(ret != 0))
-		return ret;
-
-	ret = nouveau_ttm_tt_bind(bo->bdev, bo->ttm, &tmp_reg);
-	if (unlikely(ret != 0))
-		return ret;
-
-	ttm_bo_assign_mem(bo, &tmp_reg);
-	ret = nouveau_bo_move_m2mf(bo, true, ctx, new_reg);
-	if (ret)
-		goto out;
-
-out:
-	ttm_resource_free(bo, &tmp_reg);
-	return ret;
-}
-
 static void
 nouveau_bo_move_ntfy(struct ttm_buffer_object *bo, bool evict,
 		     struct ttm_resource *new_reg)
@@ -1024,7 +934,8 @@ nouveau_bo_vm_cleanup(struct ttm_buffer_object *bo,
 static int
 nouveau_bo_move(struct ttm_buffer_object *bo, bool evict,
 		struct ttm_operation_ctx *ctx,
-		struct ttm_resource *new_reg)
+		struct ttm_resource *new_reg,
+		struct ttm_place *hop)
 {
 	struct nouveau_drm *drm = nouveau_bdev(bo->bdev);
 	struct nouveau_bo *nvbo = nouveau_bo(bo);
@@ -1032,6 +943,17 @@ nouveau_bo_move(struct ttm_buffer_object *bo, bool evict,
 	struct nouveau_drm_tile *new_tile = NULL;
 	int ret = 0;
 
+	if ((old_reg->mem_type == TTM_PL_SYSTEM &&
+	     new_reg->mem_type == TTM_PL_VRAM) ||
+	    (old_reg->mem_type == TTM_PL_VRAM &&
+	     new_reg->mem_type == TTM_PL_SYSTEM)) {
+		hop->fpfn = 0;
+		hop->lpfn = 0;
+		hop->mem_type = TTM_PL_TT;
+		hop->flags = 0;
+		return -EMULTIHOP;
+	}
+
 	if (new_reg->mem_type == TTM_PL_TT) {
 		ret = nouveau_ttm_tt_bind(bo->bdev, bo->ttm, new_reg);
 		if (ret)
@@ -1074,15 +996,8 @@ nouveau_bo_move(struct ttm_buffer_object *bo, bool evict,
 
 	/* Hardware assisted copy. */
 	if (drm->ttm.move) {
-		if (new_reg->mem_type == TTM_PL_SYSTEM)
-			ret = nouveau_bo_move_flipd(bo, evict, ctx,
-						    new_reg);
-		else if (old_reg->mem_type == TTM_PL_SYSTEM)
-			ret = nouveau_bo_move_flips(bo, evict, ctx,
-						    new_reg);
-		else
-			ret = nouveau_bo_move_m2mf(bo, evict, ctx,
-						   new_reg);
+		ret = nouveau_bo_move_m2mf(bo, evict, ctx,
+					   new_reg);
 		if (!ret)
 			goto out;
 	}
diff --git a/drivers/gpu/drm/qxl/qxl_ttm.c b/drivers/gpu/drm/qxl/qxl_ttm.c
index b52a4563b47b..103e4f248f37 100644
--- a/drivers/gpu/drm/qxl/qxl_ttm.c
+++ b/drivers/gpu/drm/qxl/qxl_ttm.c
@@ -141,7 +141,8 @@ static void qxl_bo_move_notify(struct ttm_buffer_object *bo,
 
 static int qxl_bo_move(struct ttm_buffer_object *bo, bool evict,
 		       struct ttm_operation_ctx *ctx,
-		       struct ttm_resource *new_mem)
+		       struct ttm_resource *new_mem,
+		       struct ttm_place *hop)
 {
 	struct ttm_resource *old_mem = &bo->mem;
 	int ret;
diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c
index 321c09d20c6c..ddb04a2dc25f 100644
--- a/drivers/gpu/drm/radeon/radeon_ttm.c
+++ b/drivers/gpu/drm/radeon/radeon_ttm.c
@@ -207,110 +207,27 @@ static int radeon_move_blit(struct ttm_buffer_object *bo,
 	return r;
 }
 
-static int radeon_move_vram_ram(struct ttm_buffer_object *bo,
-				bool evict,
-				struct ttm_operation_ctx *ctx,
-				struct ttm_resource *new_mem)
-{
-	struct ttm_resource *old_mem = &bo->mem;
-	struct ttm_resource tmp_mem;
-	struct ttm_place placements;
-	struct ttm_placement placement;
-	int r;
-
-	tmp_mem = *new_mem;
-	tmp_mem.mm_node = NULL;
-	placement.num_placement = 1;
-	placement.placement = &placements;
-	placement.num_busy_placement = 1;
-	placement.busy_placement = &placements;
-	placements.fpfn = 0;
-	placements.lpfn = 0;
-	placements.mem_type = TTM_PL_TT;
-	placements.flags = 0;
-	r = ttm_bo_mem_space(bo, &placement, &tmp_mem, ctx);
-	if (unlikely(r)) {
-		return r;
-	}
-
-	r = ttm_tt_populate(bo->bdev, bo->ttm, ctx);
-	if (unlikely(r)) {
-		goto out_cleanup;
-	}
-
-	r = radeon_ttm_tt_bind(bo->bdev, bo->ttm, &tmp_mem);
-	if (unlikely(r)) {
-		goto out_cleanup;
-	}
-	r = radeon_move_blit(bo, true, &tmp_mem, old_mem);
-	if (unlikely(r)) {
-		goto out_cleanup;
-	}
-	r = ttm_bo_wait_ctx(bo, ctx);
-	if (unlikely(r))
-		goto out_cleanup;
-
-	radeon_ttm_tt_unbind(bo->bdev, bo->ttm);
-	ttm_resource_free(bo, &bo->mem);
-	ttm_bo_assign_mem(bo, new_mem);
-out_cleanup:
-	ttm_resource_free(bo, &tmp_mem);
-	return r;
-}
-
-static int radeon_move_ram_vram(struct ttm_buffer_object *bo,
-				bool evict,
-				struct ttm_operation_ctx *ctx,
-				struct ttm_resource *new_mem)
-{
-	struct ttm_resource *old_mem = &bo->mem;
-	struct ttm_resource tmp_mem;
-	struct ttm_placement placement;
-	struct ttm_place placements;
-	int r;
-
-	tmp_mem = *new_mem;
-	tmp_mem.mm_node = NULL;
-	placement.num_placement = 1;
-	placement.placement = &placements;
-	placement.num_busy_placement = 1;
-	placement.busy_placement = &placements;
-	placements.fpfn = 0;
-	placements.lpfn = 0;
-	placements.mem_type = TTM_PL_TT;
-	placements.flags = 0;
-	r = ttm_bo_mem_space(bo, &placement, &tmp_mem, ctx);
-	if (unlikely(r)) {
-		return r;
-	}
-
-	r = ttm_tt_populate(bo->bdev, bo->ttm, ctx);
-	if (unlikely(r))
-		goto out_cleanup;
-
-	r = radeon_ttm_tt_bind(bo->bdev, bo->ttm, &tmp_mem);
-	if (unlikely(r))
-		goto out_cleanup;
-
-	ttm_bo_assign_mem(bo, &tmp_mem);
-	r = radeon_move_blit(bo, true, new_mem, old_mem);
-	if (unlikely(r)) {
-		goto out_cleanup;
-	}
-out_cleanup:
-	ttm_resource_free(bo, &tmp_mem);
-	return r;
-}
-
 static int radeon_bo_move(struct ttm_buffer_object *bo, bool evict,
 			  struct ttm_operation_ctx *ctx,
-			  struct ttm_resource *new_mem)
+			  struct ttm_resource *new_mem,
+			  struct ttm_place *hop)
 {
 	struct radeon_device *rdev;
 	struct radeon_bo *rbo;
 	struct ttm_resource *old_mem = &bo->mem;
 	int r;
 
+	if ((old_mem->mem_type == TTM_PL_SYSTEM &&
+	     new_mem->mem_type == TTM_PL_VRAM) ||
+	    (old_mem->mem_type == TTM_PL_VRAM &&
+	     new_mem->mem_type == TTM_PL_SYSTEM)) {
+		hop->fpfn = 0;
+		hop->lpfn = 0;
+		hop->mem_type = TTM_PL_TT;
+		hop->flags = 0;
+		return -EMULTIHOP;
+	}
+
 	if (new_mem->mem_type == TTM_PL_TT) {
 		r = radeon_ttm_tt_bind(bo->bdev, bo->ttm, new_mem);
 		if (r)
@@ -351,17 +268,8 @@ static int radeon_bo_move(struct ttm_buffer_object *bo, bool evict,
 		goto memcpy;
 	}
 
-	if (old_mem->mem_type == TTM_PL_VRAM &&
-	    new_mem->mem_type == TTM_PL_SYSTEM) {
-		r = radeon_move_vram_ram(bo, evict, ctx, new_mem);
-	} else if (old_mem->mem_type == TTM_PL_SYSTEM &&
-		   new_mem->mem_type == TTM_PL_VRAM) {
-		r = radeon_move_ram_vram(bo, evict, ctx, new_mem);
-	} else {
-		r = radeon_move_blit(bo, evict,
-				     new_mem, old_mem);
-	}
-
+	r = radeon_move_blit(bo, evict,
+			     new_mem, old_mem);
 	if (r) {
 memcpy:
 		r = ttm_bo_move_memcpy(bo, ctx, new_mem);
diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index 5b411252a857..a8830fdf8bc6 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -231,7 +231,8 @@ EXPORT_SYMBOL(ttm_bo_bulk_move_lru_tail);
 
 static int ttm_bo_handle_move_mem(struct ttm_buffer_object *bo,
 				  struct ttm_resource *mem, bool evict,
-				  struct ttm_operation_ctx *ctx)
+				  struct ttm_operation_ctx *ctx,
+				  struct ttm_place *hop)
 {
 	struct ttm_bo_device *bdev = bo->bdev;
 	struct ttm_resource_manager *old_man = ttm_manager_type(bdev, bo->mem.mem_type);
@@ -259,9 +260,12 @@ static int ttm_bo_handle_move_mem(struct ttm_buffer_object *bo,
 		}
 	}
 
-	ret = bdev->driver->move(bo, evict, ctx, mem);
-	if (ret)
+	ret = bdev->driver->move(bo, evict, ctx, mem, hop);
+	if (ret) {
+		if (ret == -EMULTIHOP)
+			return ret;
 		goto out_err;
+	}
 
 	ctx->bytes_moved += bo->num_pages << PAGE_SHIFT;
 	return 0;
@@ -596,7 +600,7 @@ static int ttm_bo_evict(struct ttm_buffer_object *bo,
 		goto out;
 	}
 
-	ret = ttm_bo_handle_move_mem(bo, &evict_mem, true, ctx);
+	ret = ttm_bo_handle_move_mem(bo, &evict_mem, true, ctx, NULL);
 	if (unlikely(ret)) {
 		if (ret != -ERESTARTSYS)
 			pr_err("Buffer eviction failed\n");
@@ -936,11 +940,39 @@ int ttm_bo_mem_space(struct ttm_buffer_object *bo,
 }
 EXPORT_SYMBOL(ttm_bo_mem_space);
 
+static int ttm_bo_bounce_temp_buffer(struct ttm_buffer_object *bo,
+				     struct ttm_resource *mem,
+				     struct ttm_operation_ctx *ctx,
+				     struct ttm_place *hop)
+{
+	struct ttm_placement hop_placement;
+	int ret;
+	struct ttm_resource hop_mem = *mem;
+
+	hop_mem.mm_node = NULL;
+	hop_mem.mem_type = TTM_PL_SYSTEM;
+	hop_mem.placement = 0;
+
+	hop_placement.num_placement = hop_placement.num_busy_placement = 1;
+	hop_placement.placement = hop_placement.busy_placement = hop;
+
+	/* find space in the bounce domain */
+	ret = ttm_bo_mem_space(bo, &hop_placement, &hop_mem, ctx);
+	if (ret)
+		return ret;
+	/* move to the bounce domain */
+	ret = ttm_bo_handle_move_mem(bo, &hop_mem, false, ctx, NULL);
+	if (ret)
+		return ret;
+	return 0;
+}
+
 static int ttm_bo_move_buffer(struct ttm_buffer_object *bo,
 			      struct ttm_placement *placement,
 			      struct ttm_operation_ctx *ctx)
 {
 	int ret = 0;
+	struct ttm_place hop = {};
 	struct ttm_resource mem;
 
 	dma_resv_assert_held(bo->base.resv);
@@ -954,12 +986,25 @@ static int ttm_bo_move_buffer(struct ttm_buffer_object *bo,
 
 	/*
 	 * Determine where to move the buffer.
+	 *
+	 * If driver determines move is going to need
+	 * an extra step then it will return -EMULTIHOP
+	 * and the buffer will be moved to the temporary
+	 * stop and the driver will be called to make
+	 * the second hop.
 	 */
+bounce:
 	ret = ttm_bo_mem_space(bo, placement, &mem, ctx);
 	if (ret)
-		goto out_unlock;
-	ret = ttm_bo_handle_move_mem(bo, &mem, false, ctx);
-out_unlock:
+		return ret;
+	ret = ttm_bo_handle_move_mem(bo, &mem, false, ctx, &hop);
+	if (ret == -EMULTIHOP) {
+		ret = ttm_bo_bounce_temp_buffer(bo, &mem, ctx, &hop);
+		if (ret)
+			return ret;
+		/* try and move to final place now. */
+		goto bounce;
+	}
 	if (ret)
 		ttm_resource_free(bo, &mem);
 	return ret;
@@ -1435,7 +1480,7 @@ int ttm_bo_swapout(struct ttm_operation_ctx *ctx)
 		evict_mem.placement = 0;
 		evict_mem.mem_type = TTM_PL_SYSTEM;
 
-		ret = ttm_bo_handle_move_mem(bo, &evict_mem, true, &ctx);
+		ret = ttm_bo_handle_move_mem(bo, &evict_mem, true, &ctx, NULL);
 		if (unlikely(ret != 0))
 			goto out;
 	}
@@ -1481,4 +1526,3 @@ void ttm_bo_tt_destroy(struct ttm_buffer_object *bo)
 	ttm_tt_destroy(bo->bdev, bo->ttm);
 	bo->ttm = NULL;
 }
-
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c
index 88be48ad0344..d48b70605a56 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c
@@ -731,7 +731,8 @@ static void vmw_swap_notify(struct ttm_buffer_object *bo)
 static int vmw_move(struct ttm_buffer_object *bo,
 		    bool evict,
 		    struct ttm_operation_ctx *ctx,
-		    struct ttm_resource *new_mem)
+		    struct ttm_resource *new_mem,
+		    struct ttm_place *hop)
 {
 	struct ttm_resource_manager *old_man = ttm_manager_type(bo->bdev, bo->mem.mem_type);
 	struct ttm_resource_manager *new_man = ttm_manager_type(bo->bdev, new_mem->mem_type);
diff --git a/include/drm/ttm/ttm_bo_driver.h b/include/drm/ttm/ttm_bo_driver.h
index 29f6a1d1c853..e4eab7a45ace 100644
--- a/include/drm/ttm/ttm_bo_driver.h
+++ b/include/drm/ttm/ttm_bo_driver.h
@@ -133,12 +133,15 @@ struct ttm_bo_driver {
 	 * the graphics address space
 	 * @ctx: context for this move with parameters
 	 * @new_mem: the new memory region receiving the buffer
+	 @ @hop: placement for driver directed intermediate hop
 	 *
 	 * Move a buffer between two memory regions.
+	 * Returns errno -EMULTIHOP if driver requests a hop
 	 */
 	int (*move)(struct ttm_buffer_object *bo, bool evict,
 		    struct ttm_operation_ctx *ctx,
-		    struct ttm_resource *new_mem);
+		    struct ttm_resource *new_mem,
+		    struct ttm_place *hop);
 
 	/**
 	 * struct ttm_bo_driver_member verify_access
-- 
2.27.0

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