[PATCH V19 04/15] drm/xe: Handle NULL resource and allow purging of VRAM pages

[Tejas Upadhyay <tejas.upadhyay@intel.com>]

Add NULL checks for the buffer object's resource pointer in
xe_bo_is_vram() and xe_bo_is_stolen() to prevent potential NULL
pointer dereferences when checking memory location during page
offlining.

Additionally, remove the `!ttm_bo->ttm` check from
xe_ttm_bo_purge(). This restriction is stripped away to
explicitly allow the driver to purge VRAM pages during the
memory page offline sequence.

v2(Sashiko):
- Split export and this patch also Check NULL res in
  xe_bo_is_vram() and xe_bo_is_stolen()

Cc: Andi Shyti <andi.shyti@linux.intel.com>
Signed-off-by: Tejas Upadhyay <tejas.upadhyay@intel.com>
---
 drivers/gpu/drm/xe/xe_bo.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
index 8f93e09e51bb..d30a8411d2a3 100644
--- a/drivers/gpu/drm/xe/xe_bo.c
+++ b/drivers/gpu/drm/xe/xe_bo.c
@@ -104,13 +104,16 @@ static bool resource_is_vram(struct ttm_resource *res)
 
 bool xe_bo_is_vram(struct xe_bo *bo)
 {
-	return resource_is_vram(bo->ttm.resource) ||
-		resource_is_stolen_vram(xe_bo_device(bo), bo->ttm.resource);
+	struct ttm_resource *res = bo->ttm.resource;
+
+	return  res && (resource_is_vram(res) || resource_is_stolen_vram(xe_bo_device(bo), res));
 }
 
 bool xe_bo_is_stolen(struct xe_bo *bo)
 {
-	return bo->ttm.resource->mem_type == XE_PL_STOLEN;
+	struct ttm_resource *res = bo->ttm.resource;
+
+	return res && res->mem_type == XE_PL_STOLEN;
 }
 
 /**
@@ -929,9 +932,6 @@ int xe_ttm_bo_purge(struct ttm_buffer_object *ttm_bo, struct ttm_operation_ctx *
 
 	xe_bo_assert_held(bo);
 
-	if (!ttm_bo->ttm)
-		return 0;
-
 	if (!xe_bo_madv_is_dontneed(bo))
 		return 0;
 
-- 
2.52.0