[Intel-gfx] [PATCH] drm/i915: Disable read only ppgtt support for gen11

[Chris Wilson]

Quoting Rodrigo Vivi (2019-04-11 20:47:48)
> On Thu, Apr 11, 2019 at 11:30:34AM +0300, Mika Kuoppala wrote:
> > On gen11 writing to read only ppgtt page causes a gpu hang.
> > This behaviour is different than with previous gen where
> > read only ppgtt access is supported. On those, the write
> > is just dropped without visible side effects.
> > 
> > Disable ro ppgtt support on gen11 until a solution can
> > be found to bring it into line with its predecessors.
> > 
> > References: HSDES#1807136187
> > References: https://bugzilla.freedesktop.org/show_bug.cgi?id=108569
> > Cc: Chris Wilson <chris at chris-wilson.co.uk>
> > Signed-off-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_gem_gtt.c | 9 +++++++--
> >  1 file changed, 7 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> > index 736c845eb77f..caae8cdafc1a 100644
> > --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> > +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> > @@ -1548,8 +1548,13 @@ static struct i915_hw_ppgtt *gen8_ppgtt_create(struct drm_i915_private *i915)
> >  
> >       ppgtt_init(i915, ppgtt);
> >  
> > -     /* From bdw, there is support for read-only pages in the PPGTT. */
> > -     ppgtt->vm.has_read_only = true;
> > +     /*
> > +      * From bdw, there is hw support for read-only pages in the PPGTT.
> > +      *
> > +      * Gen11 has HSDES#:1807136187 unresolved. Disable ro support
> > +      * for now.
> > +      */
> > +     ppgtt->vm.has_read_only = INTEL_GEN(i915) != 11;
> 
> I believe it is safest to use < 11, no?!

No. It's an issue in Icelake.
-Chris