[Intel-gfx] [PATCH 1/2] drm/i915/icl: Default to Thread Group preemption for compute workloads

[Jason Ekstrand]

FYI: For compute shaders, we have a bit in INTERFACE_DESCRIPTOR_DATA
for this which we can set from userspace without whitelisting a
register.  If drivers can't handle mid-thread, they should just set
that bit.  Unless we can mid-thread preempt media or 3D which don't
have such a bit in which case maybe we need to do something in the
kernel.

--Jason

On Wed, Mar 6, 2019 at 5:20 AM Joonas Lahtinen
<joonas.lahtinen at linux.intel.com> wrote:
>
> Quoting Chris Wilson (2019-03-05 21:10:42)
> > Quoting Rafael Antognolli (2019-03-05 17:30:00)
> > > On Tue, Mar 05, 2019 at 01:48:26PM +0100, Michał Winiarski wrote:
> > > > We assumed that the default preemption granularity is fine for ICL.
> > > > Unfortunately, it turns out that some drivers don't support mid-thread
> > > > preemption for compute workloads.
> > > > If a workload that doesn't support mid-thread preemption gets mid-thread
> > > > preempted, we're going to observe a GPU hang.
> > > > While I'm here, let's also update the "workaround" naming.
> > >
> > > Yeah, in Mesa we are not implementing the SIP, so we can't do
> > > thread-level preemption yet and need the granularity to be no higher
> > > than thread group level.
> > >
> > > Acked-by: Rafael Antognolli <rafael.antognolli at intel.com>
> > >
> > > > Signed-off-by: Michał Winiarski <michal.winiarski at intel.com>
> > > > Cc: Anuj Phogat <anuj.phogat at intel.com>
> > > > Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> > > > Cc: Matt Roper <matthew.d.roper at intel.com>
> > > > Cc: Rafael Antognolli <rafael.antognolli at intel.com>
> > > > Tested-by: Anuj Phogat <anuj.phogat at intel.com>
> > > > Reviewed-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
> >
> > And pushed, thanks everyone for the testing and reviewed. I've held off
> > on pushing the second patch as we just want to double check that the
> > whitelisting is required.
>
> Yeah, we should only need to push it once there is an actual consumer
> that will enable it.
>
> Regards, Joonas
>
> > -Chris
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