drm/xe: Assert that VF will never use fixed placement of BOs

Most BOs do not care at which offset they will be accessed within
GGTT or PPGTT. The few which do care, should be only created
on PF, and mapped within GGTT. On VFs, mapping at fixed offset
is prohibited, as each VF is granted access to a range of
GGTT address space.

Since fixed addresses of GGTT mapping can only be used on PF,
add an assert which makes sure no attempt of fixed placement
will happen for a driver probed on a VF.

Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: Tomasz Lis <tomasz.lis@intel.com>
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://lore.kernel.org/r/20251021224817.1593817-4-tomasz.lis@intel.com

Author: tomaszli

drivers/gpu/drm/xe/xe_bo.c

@@ -2275,6 +2275,12 @@ static int __xe_bo_fixed_placement(struct xe_device *xe,
 	struct ttm_place *place = bo->placements;
 	u32 vram_flag, vram_stolen_flags;
 
+	/*
+	 * to allow fixed placement in GGTT of a VF, post-migration fixups would have to
+	 * include selecting a new fixed offset and shifting the page ranges for it
+	 */
+	xe_assert(xe, !IS_SRIOV_VF(xe) || !(bo->flags & XE_BO_FLAG_GGTT));
+
 	if (flags & (XE_BO_FLAG_USER | XE_BO_FLAG_SYSTEM))
 		return -EINVAL;