Re: [PATCH 1/2] drm/xe/guc: Fix stack_depot usage

["Summers, Stuart" <stuart.summers@intel.com>]

On Tue, 2025-11-18 at 11:08 -0800, Lucas De Marchi wrote:
> Add missing stack_depot_init() call when CONFIG_DRM_XE_DEBUG_GUC is
> enabled to fix the following call stack:
> 
>         [] BUG: kernel NULL pointer dereference, address:
> 0000000000000000
>         [] Workqueue:  drm_sched_run_job_work [gpu_sched]
>         [] RIP: 0010:stack_depot_save_flags+0x172/0x870
>         [] Call Trace:
>         []  <TASK>
>         []  fast_req_track+0x58/0xb0 [xe]
> 
> Fixes: 16b7e65d299d ("drm/xe/guc: Track FAST_REQ H2Gs to report where
> errors came from")
> Tested-by: Sagar Ghuge <sagar.ghuge@intel.com>
> Cc: <stable@vger.kernel.org> # v6.17+
> Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

Reviewed-by: Stuart Summers <stuart.summers@intel.com>

I believe in CI we're setting the DEBUG_MM config option which also
does this. It looks like that stack_depot_init() checks if it was
already initialized (statically) before doing the initialization, so
should be harmless calling this twice if we do have that config set.

Thanks,
Stuart

> ---
>  drivers/gpu/drm/xe/xe_guc_ct.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_guc_ct.c
> b/drivers/gpu/drm/xe/xe_guc_ct.c
> index 2697d711adb2b..07ae0d601910e 100644
> --- a/drivers/gpu/drm/xe/xe_guc_ct.c
> +++ b/drivers/gpu/drm/xe/xe_guc_ct.c
> @@ -236,6 +236,9 @@ int xe_guc_ct_init_noalloc(struct xe_guc_ct *ct)
>  #if IS_ENABLED(CONFIG_DRM_XE_DEBUG)
>         spin_lock_init(&ct->dead.lock);
>         INIT_WORK(&ct->dead.worker, ct_dead_worker_func);
> +#if IS_ENABLED(CONFIG_DRM_XE_DEBUG_GUC)
> +       stack_depot_init();
> +#endif
>  #endif
>         init_waitqueue_head(&ct->wq);
>         init_waitqueue_head(&ct->g2h_fence_wq);
>