[PATCH v2 1/5] drm/xe: Guard against NULL GT in xe_sriov_vf.c

[Jonathan Cavitt <jonathan.cavitt@intel.com>]

Static analysis reveals the following issue:
xe_device_get_gt is theoretically able to return NULL in some cases, but
several use cases don't check the return value before performing a
dereference, resulting in a NULL pointer dereference.

Add guards against this in xe_sriov_vf.c:
- Use xe_root_mmio_gt instead of xe_device_get_gt for the gt id 0 case.
- Assert the return value of xe_device_get_gt when this is not possible.

v2: Use xe_assert in vf_post_migration_recovery (Michal)

Signed-off-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
---
 drivers/gpu/drm/xe/xe_sriov_vf.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/xe/xe_sriov_vf.c b/drivers/gpu/drm/xe/xe_sriov_vf.c
index cdd9f8e78b2a..2c9cef191826 100644
--- a/drivers/gpu/drm/xe/xe_sriov_vf.c
+++ b/drivers/gpu/drm/xe/xe_sriov_vf.c
@@ -178,7 +178,7 @@ static void vf_migration_init_early(struct xe_device *xe)
 	if (!IS_DGFX(xe)) {
 		struct xe_uc_fw_version guc_version;
 
-		xe_gt_sriov_vf_guc_versions(xe_device_get_gt(xe, 0), NULL, &guc_version);
+		xe_gt_sriov_vf_guc_versions(xe_root_mmio_gt(xe), NULL, &guc_version);
 		if (MAKE_GUC_VER_STRUCT(guc_version) < MAKE_GUC_VER(1, 23, 0))
 			return vf_disable_migration(xe,
 						    "CCS migration requires GuC ABI >= 1.23 but only %u.%u found",
@@ -361,6 +361,8 @@ static void vf_post_migration_recovery(struct xe_device *xe)
 	while (id = vf_get_next_migrated_gt_id(xe), id >= 0) {
 		struct xe_gt *gt = xe_device_get_gt(xe, id);
 
+		xe_assert(xe, gt);
+
 		err = gt_vf_post_migration_fixups(gt);
 		if (err)
 			goto fail;
-- 
2.43.0