[Intel-gfx] [PATCH 1/2] drm/i915/gtt: Enable full-ppgtt by default everywhere

[Chris Wilson]

Quoting Kenneth Graunke (2018-07-17 21:02:33)
> On Tuesday, July 17, 2018 2:57:50 AM PDT Chris Wilson wrote:
> > We should we have all the kinks worked out and full-ppgtt now works
> > reliably on gen7 (Ivybridge, Valleyview/Baytrail and Haswell). If we can
> > let userspace have full control over their own ppgtt, it makes softpinning
> > far more effective, in turn making GPU dispatch far more efficient by
> > virtue of better mm segregation.  On the other hand, switching over to a
> > different GTT for every client does incur noticeable overhead, but only
> > for very lightweight tasks.
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> > Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> > Cc: Matthew Auld <matthew.william.auld at gmail.com>
> > Reviewed-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> > Cc: Jason Ekstrand <jason.ekstrand at intel.com>
> > Cc: Kenneth Graunke <kenneth at whitecape.org>
> > ---
> >  drivers/gpu/drm/i915/i915_gem_gtt.c | 10 ++++------
> >  1 file changed, 4 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> > index f00c7fbef79e..9bad73332ce7 100644
> > --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> > +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> > @@ -179,13 +179,11 @@ int intel_sanitize_enable_ppgtt(struct drm_i915_private *dev_priv,
> >               return 0;
> >       }
> >  
> > -     if (HAS_LOGICAL_RING_CONTEXTS(dev_priv)) {
> > -             if (has_full_48bit_ppgtt)
> > -                     return 3;
> > +     if (has_full_48bit_ppgtt)
> > +             return 3;
> >  
> > -             if (has_full_ppgtt)
> > -                     return 2;
> > -     }
> > +     if (has_full_ppgtt)
> > +             return 2;
> >  
> >       return 1;
> >  }
> > 
> 
> I'm very glad to see this land, PPGTT is really important for security.
> It may also enable us to do more interesting things on Gen7.x.
> 
> Acked-by: Kenneth Graunke <kenneth at whitecape.org>

Plonked in. If I timed it right, it should have just missed the 4.19
cutoff, so we have the best part of 6 months to detect any damage.
-Chris