Re: [PATCH v2 4/5] drm/xe: Guard against NULL GT in xe_guc.c

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

On Fri, Sep 26, 2025 at 08:09:22PM +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.
> 
> Use xe_assert to assert root_gt is not NULL before dereferencing it.
> 
> While we're here, replace xe_device_get_gt(xe, 0) with the equivalent
> call xe_root_mmio_gt(xe).  There's no reason to use the flexible
> xe_device_get_gt function when we're only always tring to get GT0 here.
> 
> v2: xe_assert root_gt is not NULL (Michal, Matt)

I really don't believe this is what they suggested.
I had understood that the suggestion was to mark the case as false
positive in the tool.

> 
> Signed-off-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
> Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
> Cc: Matt Roper <matthew.d.roper@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_guc.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_guc.c b/drivers/gpu/drm/xe/xe_guc.c
> index d5adbbb013ec..38fba439f1e8 100644
> --- a/drivers/gpu/drm/xe/xe_guc.c
> +++ b/drivers/gpu/drm/xe/xe_guc.c
> @@ -466,10 +466,13 @@ static int guc_g2g_alloc(struct xe_guc *guc)
>  		return 0;
>  
>  	if (gt->info.id != 0) {
> -		struct xe_gt *root_gt = xe_device_get_gt(xe, 0);
> -		struct xe_guc *root_guc = &root_gt->uc.guc;
> +		struct xe_gt *root_gt = xe_root_mmio_gt(xe);
> +		struct xe_guc *root_guc;
>  		struct xe_bo *bo;
>  
> +		xe_assert(xe, root_gt);
> +		root_guc = &root_gt->uc.guc;
> +
>  		bo = xe_bo_get(root_guc->g2g.bo);
>  		if (!bo)
>  			return -ENODEV;
> -- 
> 2.43.0
>