drm/xe: Fix incorrect migration of backed-up object to VRAM

If an object is backed up to shmem it is incorrectly identified
as not having valid data by the move code. This means moving
to VRAM skips the -EMULTIHOP step and the bo is cleared. This
causes all sorts of weird behaviour on DGFX if an already evicted
object is targeted by the shrinker.

Fix this by using ttm_tt_is_swapped() to identify backed-up
objects.

Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/5996
Fixes: 00c8efc ("drm/xe: Add a shrinker for xe bos")
Cc: Matthew Brost <[email protected]>
Cc: Matthew Auld <[email protected]>
Cc: <[email protected]> # v6.15+
Signed-off-by: Thomas Hellström <[email protected]>
Reviewed-by: Matthew Auld <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
(cherry picked from commit 1047bd8)
Signed-off-by: Rodrigo Vivi <[email protected]>

Author: Thomas Hellström

drivers/gpu/drm/xe/xe_bo.c

@@ -819,8 +819,7 @@ static int xe_bo_move(struct ttm_buffer_object *ttm_bo, bool evict,
 		return ret;
 	}
 
-	tt_has_data = ttm && (ttm_tt_is_populated(ttm) ||
-			      (ttm->page_flags & TTM_TT_FLAG_SWAPPED));
+	tt_has_data = ttm && (ttm_tt_is_populated(ttm) || ttm_tt_is_swapped(ttm));
 
 	move_lacks_source = !old_mem || (handle_system_ccs ? (!bo->ccs_cleared) :
 					 (!mem_type_is_vram(old_mem_type) && !tt_has_data));