Re: [PATCH v3 09/36] drm/xe: Don't change LRC ring head on job resubmission

["Lis, Tomasz" <tomasz.lis@intel.com>]

On 9/29/2025 4:55 AM, Matthew Brost wrote:
> Now that we save the job's head during submission, it's no longer
> necessary to adjust the LRC ring head during resubmission. Instead, a
> software-based adjustment of the tail will overwrite the old jobs in
> place. For some odd reason, adjusting the LRC ring head didn't work on
> parallel queues, which was causing issues in our CI.
>
> v6:
>   - Also set LRC tail to head so queue is idle coming out of reset
Reviewed-by: Tomasz Lis <tomasz.lis@intel.com>
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> ---
>   drivers/gpu/drm/xe/xe_guc_submit.c | 10 ++++++++--
>   1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_guc_submit.c b/drivers/gpu/drm/xe/xe_guc_submit.c
> index 3a534d93505f..70306f902ba5 100644
> --- a/drivers/gpu/drm/xe/xe_guc_submit.c
> +++ b/drivers/gpu/drm/xe/xe_guc_submit.c
> @@ -2008,11 +2008,17 @@ static void guc_exec_queue_start(struct xe_exec_queue *q)
>   	struct xe_gpu_scheduler *sched = &q->guc->sched;
>   
>   	if (!exec_queue_killed_or_banned_or_wedged(q)) {
> +		struct xe_sched_job *job = xe_sched_first_pending_job(sched);
>   		int i;
>   
>   		trace_xe_exec_queue_resubmit(q);
> -		for (i = 0; i < q->width; ++i)
> -			xe_lrc_set_ring_head(q->lrc[i], q->lrc[i]->ring.tail);
> +		if (job) {
> +			for (i = 0; i < q->width; ++i) {
> +				q->lrc[i]->ring.tail = job->ptrs[i].head;
> +				xe_lrc_set_ring_tail(q->lrc[i],
> +						     xe_lrc_ring_head(q->lrc[i]));
> +			}
> +		}
>   		xe_sched_resubmit_jobs(sched);
>   	}
>