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

[Matthew Brost <matthew.brost@intel.com>]

On Mon, Jul 07, 2025 at 09:55:58PM -0500, Lucas De Marchi wrote:
> On Fri, Jul 04, 2025 at 12:21:50PM +0100, Tvrtko Ursulin wrote:
> > 
> > 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.
> 
> I don't think it really fixes anything, it's just pointless to do it.
> It would just save the same information from the first time it executed
> even if there was a race.
> 

Agree with Lucas, this pointless yet harmless.

Matt

> Lucas De Marchi
> 
> > 
> > Regards,
> > 
> > Tvrtko
> >