Re: [Intel-gfx] [PATCH 1/2] drm/i915/execlists: HWS is uncached on !llc platforms

2015-10-23 Thread Ville Syrjälä
On Fri, Oct 23, 2015 at 08:08:34PM +0100, Chris Wilson wrote: > On Fri, Oct 23, 2015 at 09:41:29PM +0300, Ville Syrjälä wrote: > > On Fri, Oct 23, 2015 at 07:29:08PM +0100, Chris Wilson wrote: > > > On Fri, Oct 23, 2015 at 09:22:38PM +0300, Ville Syrjälä wrote: > > > > On Fri, Oct 23, 2015 at 06:56

Re: [Intel-gfx] [PATCH 1/2] drm/i915/execlists: HWS is uncached on !llc platforms

2015-10-23 Thread Chris Wilson
On Fri, Oct 23, 2015 at 09:41:29PM +0300, Ville Syrjälä wrote: > On Fri, Oct 23, 2015 at 07:29:08PM +0100, Chris Wilson wrote: > > On Fri, Oct 23, 2015 at 09:22:38PM +0300, Ville Syrjälä wrote: > > > On Fri, Oct 23, 2015 at 06:56:41PM +0100, Chris Wilson wrote: > > > > On Fri, Oct 23, 2015 at 08:50

Re: [Intel-gfx] [PATCH 1/2] drm/i915/execlists: HWS is uncached on !llc platforms

2015-10-23 Thread Ville Syrjälä
On Fri, Oct 23, 2015 at 07:29:08PM +0100, Chris Wilson wrote: > On Fri, Oct 23, 2015 at 09:22:38PM +0300, Ville Syrjälä wrote: > > On Fri, Oct 23, 2015 at 06:56:41PM +0100, Chris Wilson wrote: > > > On Fri, Oct 23, 2015 at 08:50:42PM +0300, Ville Syrjälä wrote: > > > > On Fri, Oct 23, 2015 at 06:43

Re: [Intel-gfx] [PATCH 1/2] drm/i915/execlists: HWS is uncached on !llc platforms

2015-10-23 Thread Chris Wilson
On Fri, Oct 23, 2015 at 09:22:38PM +0300, Ville Syrjälä wrote: > On Fri, Oct 23, 2015 at 06:56:41PM +0100, Chris Wilson wrote: > > On Fri, Oct 23, 2015 at 08:50:42PM +0300, Ville Syrjälä wrote: > > > On Fri, Oct 23, 2015 at 06:43:31PM +0100, Chris Wilson wrote: > > > > As the HWS is mapped into the

Re: [Intel-gfx] [PATCH 1/2] drm/i915/execlists: HWS is uncached on !llc platforms

2015-10-23 Thread Ville Syrjälä
On Fri, Oct 23, 2015 at 06:56:41PM +0100, Chris Wilson wrote: > On Fri, Oct 23, 2015 at 08:50:42PM +0300, Ville Syrjälä wrote: > > On Fri, Oct 23, 2015 at 06:43:31PM +0100, Chris Wilson wrote: > > > As the HWS is mapped into the GPU as uncached, > > > > Since when? > > Since it is embedded into e

Re: [Intel-gfx] [PATCH 1/2] drm/i915/execlists: HWS is uncached on !llc platforms

2015-10-23 Thread Chris Wilson
On Fri, Oct 23, 2015 at 08:50:42PM +0300, Ville Syrjälä wrote: > On Fri, Oct 23, 2015 at 06:43:31PM +0100, Chris Wilson wrote: > > As the HWS is mapped into the GPU as uncached, > > Since when? Since it is embedded into execlists' default context which is allocated using the system default cache

Re: [Intel-gfx] [PATCH 1/2] drm/i915/execlists: HWS is uncached on !llc platforms

2015-10-23 Thread Ville Syrjälä
On Fri, Oct 23, 2015 at 06:43:31PM +0100, Chris Wilson wrote: > As the HWS is mapped into the GPU as uncached, Since when? > writes into that page do > not automatically snoop the CPU cache and therefore if we want to see > coherent values we need to clear the stale cacheline first. Note, we > al

[Intel-gfx] [PATCH 1/2] drm/i915/execlists: HWS is uncached on !llc platforms

2015-10-23 Thread Chris Wilson
As the HWS is mapped into the GPU as uncached, writes into that page do not automatically snoop the CPU cache and therefore if we want to see coherent values we need to clear the stale cacheline first. Note, we already had a workaround for BXT-A for an identical issue, but since we never enabled sn