Re: [PATCH v2] drm/xe/xe_guc_ct: Exit CT submission fence wait on GT reset

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

On Tue, 2025-12-23 at 23:02 +0000, Jonathan Cavitt wrote:
> It's possible if unlikely that the GuC could be reset in the time
> between performing a guc_ct_send and the G2H fence completing in
> guc_ct_send_recv.  Exit early if this is occurs.
> 
> v2: Rebase
> 
> Suggested-by: Stuart Summers <stuart.summers@intel.com>
> Signed-off-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_guc_ct.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_guc_ct.c
> b/drivers/gpu/drm/xe/xe_guc_ct.c
> index dfbf76037b04..64ac985867ae 100644
> --- a/drivers/gpu/drm/xe/xe_guc_ct.c
> +++ b/drivers/gpu/drm/xe/xe_guc_ct.c
> @@ -1238,6 +1238,10 @@ int xe_guc_ct_send_g2h_handler(struct
> xe_guc_ct *ct, const u32 *action, u32 len)
>         return ret;
>  }
>  
> +#define ct_alive(ct)    \
> +       (xe_guc_ct_enabled(ct) && !ct->ctbs.h2g.info.broken && \
> +        !ct->ctbs.g2h.info.broken)
> +
>  /*
>   * Check if a GT reset is in progress or will occur and if GT reset
> brought the
>   * CT back up. Randomly picking 5 seconds for an upper limit to do a
> GT a reset.
> @@ -1247,12 +1251,8 @@ static bool retry_failure(struct xe_guc_ct
> *ct, int ret)
>         if (!(ret == -EDEADLK || ret == -EPIPE || ret == -ENODEV))
>                 return false;
>  
> -#define ct_alive(ct)   \
> -       (xe_guc_ct_enabled(ct) && !ct->ctbs.h2g.info.broken && \
> -        !ct->ctbs.g2h.info.broken)
>         if (!wait_event_interruptible_timeout(ct->wq, ct_alive(ct),
> HZ * 5))
>                 return false;
> -#undef ct_alive
>  
>         return true;
>  }
> @@ -1304,7 +1304,8 @@ static int guc_ct_send_recv(struct xe_guc_ct
> *ct, const u32 *action, u32 len,
>         /* READ_ONCEs pairs with WRITE_ONCEs in parse_g2h_response
>          * and g2h_fence_cancel.
>          */
> -       ret = wait_event_timeout(ct->g2h_fence_wq,
> READ_ONCE(g2h_fence.done), HZ);
> +       ret = wait_event_timeout(ct->g2h_fence_wq, !ct_alive(ct) ||

So I think we want to do something similar here to what we had done
with the guc_ct_send() call above - basically jump back to
retry_same_fence to retry again if !ct_alive. The idea being that GuC
should eventually recover after the reset and begin accepting
communication.

Thanks,
Stuart

> +                                READ_ONCE(g2h_fence.done), HZ);
>         if (!ret) {
>                 LNL_FLUSH_WORK(&ct->g2h_worker);
>                 if (READ_ONCE(g2h_fence.done)) {