[PATCH RFC 2/2] drm/amdgpu: Set/clear CPU_ACCESS flag on page fault and move to VRAM

[John Brooks]

When a BO is moved to VRAM, clear AMDGPU_BO_FLAG_CPU_ACCESS. This allows it
to potentially later move to invisible VRAM if the CPU does not access it
again.

Setting the CPU_ACCESS flag in amdgpu_fault_reserve_notify() also means
that we can remove the loop to restrict lpfn to the end of visible VRAM,
because amdgpu_ttm_placement_init() will do it for us.

Signed-off-by: John Brooks <john at fastquake.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_object.c | 3 +++
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c    | 8 ++++++++
 2 files changed, 11 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
index fa8aeca..19bd2fd 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
@@ -953,6 +953,9 @@ int amdgpu_bo_fault_reserve_notify(struct ttm_buffer_object *bo)
 		return 0;
 
 	abo = container_of(bo, struct amdgpu_bo, tbo);
+
+	abo->flags |= AMDGPU_BO_FLAG_CPU_ACCESS;
+
 	if (bo->mem.mem_type != TTM_PL_VRAM)
 		return 0;
 
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index c9b131b..cc65cdd 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -417,6 +417,7 @@ static int amdgpu_move_ram_vram(struct ttm_buffer_object *bo,
 				struct ttm_mem_reg *new_mem)
 {
 	struct amdgpu_device *adev;
+	struct amdgpu_bo *abo;
 	struct ttm_mem_reg *old_mem = &bo->mem;
 	struct ttm_mem_reg tmp_mem;
 	struct ttm_placement placement;
@@ -424,6 +425,7 @@ static int amdgpu_move_ram_vram(struct ttm_buffer_object *bo,
 	int r;
 
 	adev = amdgpu_ttm_adev(bo->bdev);
+	abo = container_of(bo, struct amdgpu_bo, tbo);
 	tmp_mem = *new_mem;
 	tmp_mem.mm_node = NULL;
 	placement.num_placement = 1;
@@ -446,6 +448,12 @@ static int amdgpu_move_ram_vram(struct ttm_buffer_object *bo,
 	if (unlikely(r)) {
 		goto out_cleanup;
 	}
+
+	/* The page fault handler will re-set this if the CPU accesses the BO
+	 * after it's moved.
+	 */
+	abo->flags &= ~AMDGPU_BO_FLAG_CPU_ACCESS;
+
 out_cleanup:
 	ttm_bo_mem_put(bo, &tmp_mem);
 	return r;
-- 
2.7.4