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

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Fri, Sep 26, 2025 at 08:09:19PM +0000, Jonathan Cavitt wrote:
> 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);

I really have my doubts if the tool will understand this or you will end up
anyway having to mark that as false positive.

Let's just mark as false positive in the tool and move on.

> +
>  		err = gt_vf_post_migration_fixups(gt);
>  		if (err)
>  			goto fail;
> -- 
> 2.43.0
>