Re: [PATCH 6/7] drm/xe/gt: Drop third submission for default context

[Tvrtko Ursulin <tvrtko.ursulin@igalia.com>]

On 03/07/2025 23:41, Lucas De Marchi wrote:
> There's no need to submit the nop job again on the first queue. Any
> state needed is already saved when the first LRC is switched out. The
> comment is a little misleading regarding indirect W/A: first of all
> there's still no indirect W/A enabled and secondly, even after they are,
> there's no need to submit this job again for having their state
> propagated: the indirect W/A will actually run on every LRC switch.
> 
> Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
> ---
>   drivers/gpu/drm/xe/xe_gt.c | 8 --------
>   1 file changed, 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_gt.c b/drivers/gpu/drm/xe/xe_gt.c
> index 67425e37c2187..439e7c703ed84 100644
> --- a/drivers/gpu/drm/xe/xe_gt.c
> +++ b/drivers/gpu/drm/xe/xe_gt.c
> @@ -361,14 +361,6 @@ int xe_gt_record_default_lrcs(struct xe_gt *gt)
>   			goto put_nop_q;
>   		}
>   
> -		/* Reload golden LRC to record the effect of any indirect W/A */
> -		err = emit_nop_job(gt, q);
> -		if (err) {
> -			xe_gt_err(gt, "hwe %s: emit_nop_job failed (%pe) guc_id=%u\n",
> -				  hwe->name, ERR_PTR(err), q->guc->id);
> -			goto put_nop_q;
> -		}
> -
>   		xe_map_memcpy_from(xe, default_lrc,
>   				   &q->lrc[0]->bo->vmap,
>   				   xe_lrc_pphwsp_offset(q->lrc[0]),
> 

Wasn't it also racy to memcpy from q's LRC without guaranteeing context 
save had completed? I don't think dma_fence_wait in emit_nop_job 
guarantees it. If that is so this patch should actually have Fixes: 
added and commit message adjusted accordingly.

Regards,

Tvrtko