drm/amdgpu: add shadow flag V2

Indicate if need to sync between bo and shadow, where sync to where.
V2:
Rename to backup_shadow

Signed-off-by: Chunming Zhou <David1.Zhou@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu.h

@@ -480,6 +480,12 @@ struct amdgpu_bo_va {
 
 #define AMDGPU_GEM_DOMAIN_MAX		0x3
 
+enum amdgpu_bo_shadow {
+	AMDGPU_BO_SHADOW_TO_NONE = 0,
+	AMDGPU_BO_SHADOW_TO_PARENT,
+	AMDGPU_BO_SHADOW_TO_SHADOW,
+};
+
 struct amdgpu_bo {
 	/* Protected by gem.mutex */
 	struct list_head		list;
@@ -506,6 +512,8 @@ struct amdgpu_bo {
 	struct drm_gem_object		gem_base;
 	struct amdgpu_bo		*parent;
 	struct amdgpu_bo		*shadow;
+	/* indicate if need to sync between bo and shadow */
+	enum amdgpu_bo_shadow           backup_shadow;
 
 	struct ttm_bo_kmap_obj		dma_buf_vmap;
 	struct amdgpu_mn		*mn;