drm/xe: Wait for migration job before unmapping pages

Fix a potential GPU page fault during tt -> system moves by waiting for
migration jobs to complete before unmapping SG. This ensures that IOMMU
mappings are not prematurely torn down while a migration job is still in
progress.

v2: Use intr=false(Matt A)
v3: Update commit message(Matt A)
v4: s/DMA_RESV_USAGE_BOOKKEEP/DMA_RESV_USAGE_KERNEL(Thomas)

Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/3466
Fixes: 75521e8 ("drm/xe: Perform dma_map when moving system buffer objects to TT")
Cc: Thomas Hellström <[email protected]>
Cc: Matthew Brost <[email protected]>
Cc: Lucas De Marchi <[email protected]>
Cc: [email protected] # v6.11+
Cc: Matthew Auld <[email protected]>
Reviewed-by: Matthew Auld <[email protected]>
Reviewed-by: Thomas Hellström <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
Signed-off-by: Nirmoy Das <[email protected]>

Author: nirmoy

drivers/gpu/drm/xe/xe_bo.c

@@ -857,8 +857,16 @@ static int xe_bo_move(struct ttm_buffer_object *ttm_bo, bool evict,
 
 out:
 	if ((!ttm_bo->resource || ttm_bo->resource->mem_type == XE_PL_SYSTEM) &&
-	    ttm_bo->ttm)
+	    ttm_bo->ttm) {
+		long timeout = dma_resv_wait_timeout(ttm_bo->base.resv,
+						     DMA_RESV_USAGE_KERNEL,
+						     false,
+						     MAX_SCHEDULE_TIMEOUT);
+		if (timeout < 0)
+			ret = timeout;
+
 		xe_tt_unmap_sg(ttm_bo->ttm);
+	}
 
 	return ret;
 }