Re: [PATCH 2/8] drm/i915/xehp: CCS shares the render reset domain

[Matt Roper <matthew.d.roper@intel.com>]

On Wed, Sep 08, 2021 at 11:07:07AM +0100, Tvrtko Ursulin wrote:
> 
> On 07/09/2021 18:19, Matt Roper wrote:
> > The reset domain is shared between render and all compute engines,
> > so resetting one will affect the others.
> > 
> > Note:  Before performing a reset on an RCS or CCS engine, the GuC will
> > attempt to preempt-to-idle the other non-hung RCS/CCS engines to avoid
> > impacting other clients (since some shared modules will be reset).  If
> > other engines are executing non-preemptable workloads, the impact is
> > unavoidable and some work may be lost.
> 
> Since here it talks about engine reset, should this patch add warning if
> same is attempted by i915 on a GuC platform - to document it is not

Did you mean "on a *non* GuC platform" here?  We aren't going to have
compute engine support on any platforms where GuC submission isn't the
default operating model, so the only way to get compute engines +
execlist submission is to force an override via module parameters (e.g.,
enable_guc=0).  Doing so will taint the kernel, so I think the current
consensus from offline discussion is that the user has already put
themselves into a configuration where it's easier than usual to shoot
themselves in the foot; it's not too much different than the kind of
trouble a user could get themselves into if they loaded the driver with
hangcheck disabled or something.


Matt

> implemented/supported? Or perhaps later in the series, or future series
> works better.
> 
> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> 
> Regards,
> 
> Tvrtko
> 
> > Bspec: 52549
> > Original-patch-by: Michel Thierry
> > Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
> > Cc: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
> > Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
> > Signed-off-by: Aravind Iddamsetty <aravind.iddamsetty@intel.com>
> > Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
> > ---
> >   drivers/gpu/drm/i915/gt/intel_reset.c | 4 ++++
> >   1 file changed, 4 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/gt/intel_reset.c b/drivers/gpu/drm/i915/gt/intel_reset.c
> > index 91200c43951f..30598c1d070c 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_reset.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_reset.c
> > @@ -507,6 +507,10 @@ static int gen11_reset_engines(struct intel_gt *gt,
> >   		[VECS1] = GEN11_GRDOM_VECS2,
> >   		[VECS2] = GEN11_GRDOM_VECS3,
> >   		[VECS3] = GEN11_GRDOM_VECS4,
> > +		[CCS0] = GEN11_GRDOM_RENDER,
> > +		[CCS1] = GEN11_GRDOM_RENDER,
> > +		[CCS2] = GEN11_GRDOM_RENDER,
> > +		[CCS3] = GEN11_GRDOM_RENDER,
> >   	};
> >   	struct intel_engine_cs *engine;
> >   	intel_engine_mask_t tmp;
> > 

-- 
Matt Roper
Graphics Software Engineer
VTT-OSGC Platform Enablement
Intel Corporation
(916) 356-2795