Re: [PATCH 2/7] drm/i915: Enable full ppgtt for vgpu

Zhiyuan Lv
2015-08-27T02:36:08Z

Hi Danie,

On Wed, Aug 26, 2015 at 10:47:37AM +0200, Daniel Vetter wrote:
> On Thu, Aug 20, 2015 at 01:57:13PM +0300, Joonas Lahtinen wrote:
> > On to, 2015-08-20 at 15:45 +0800, Zhiyuan Lv wrote:
> > > The full ppgtt is supported in Intel GVT-g device model. So the
> > > restriction can be removed.
> > >
> > > Signed-off-by: Zhiyuan Lv <zhiyuan.lv@intel.com>
> > > Signed-off-by: Zhi Wang <zhi.a.wang@intel.com>
> >
> > Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> >
> > > ---
> > > drivers/gpu/drm/i915/i915_gem_gtt.c | 3 ---
> > > 1 file changed, 3 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c
> > > b/drivers/gpu/drm/i915/i915_gem_gtt.c
> > > index ed10e77..823005c 100644
> > > --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> > > +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> > > @@ -108,9 +108,6 @@ static int sanitize_enable_ppgtt(struct
> > > drm_device *dev, int enable_ppgtt)
> > > has_aliasing_ppgtt = INTEL_INFO(dev)->gen >= 6;
> > > has_full_ppgtt = INTEL_INFO(dev)->gen >= 7;
> > >
> > > - if (intel_vgpu_active(dev))
> > > - has_full_ppgtt = false; /* emulation is too hard */
>
> Don't we need a feature check for the virtual gpu here? Or at least a
> platform check? Seems like the backwards/forwards compat story isn't too
> thought out yet here. Note that the kernel of the host and the guest might
> not be the same at all, much less the kvm part.

Yeah, backwards/forwards compatibility is not considered, since we are
just to start the upstream of iGVT-g host changes. Right now if people
uses new enough iGVT-g code (off-tree now), both HSW and BDW should
work with PPGTT.

So new host with both old guest or new guest are working. The only
thing impacted is old host with new guest kernel. In order to keep it
work, I can change the code like:

+ if (intel_vgpu_active(dev))
+ has_full_ppgtt = !IS_HASWELL(dev);

Any comments? Thanks for the review!

Regards,
-Zhiyuan

> -Daniel
>
> > > -
> > > /*
> > > * We don't allow disabling PPGTT for gen9+ as it's a
> > > requirement for
> > > * execlists, the sole mechanism available to submit work.
> > _______________________________________________
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> > Intel-gfx@lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch