[Intel-gfx] [PATCH v3] drm/i915: Enable guest i915 full ppgtt functionality

[Zhenyu Wang]

On 2017.05.30 11:37:50 +0300, Joonas Lahtinen wrote:
> On ma, 2017-05-22 at 16:19 +0800, Tina Zhang wrote:
> > Enable the guest i915 full ppgtt functionality when host can provide this
> > capability. vgt_caps is introduced to guest i915 driver to get the vgpu
> > capabilities from the device model. VGT_CPAS_FULL_PPGTT is one of the
> > capabilities type to let guest i915 dirver know that the guest i915 full
> > ppgtt is supported by device model.
> > 
> > Changes since v1:
> > - Use u32 instead of uint32_t (Joonas)
> > - Move VGT_CAPS_FULL_PPGTT introduction to this patch and use #define
> >   instead of enum (Joonas)
> > - Rewrite the vgpu full ppgtt capability checking logic. (Joonas)
> > - Some coding style refine. (Joonas)
> > 
> > Changes since v2:
> > - Divide the whole patch set into two separate patch series, with one
> >   patch in i915 side to check guest i915 full ppgtt capability and enable
> >   it when this capability is supported by the device model, and the other
> >   one in gvt side which fixs the blocking issue and enables the device
> >   model to provide the capability to guest. And this patch focuses on guest
> >   i915 side. (Joonas)
> > - Change the title from "introduce vgt_caps to pvinfo" to
> >   "Enable guest i915 full ppgtt functionality". (Tina)
> > 
> > Reviewed-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> > Signed-off-by: Tina Zhang <tina.zhang at intel.com>
> 
> I just noticed there is INTEL_VGT_IF_VERSION when I was looking to make
> sure that vgt_if is zeroed. Neither the version is incremented nor do I
> see VGT_PVINFO_PAGE getting zeroed.
>
> What measures are in place to make sure running a new i915 under older
> DOM0 won't result in corruption?
> 
> The dependencies between i915 and gvt are rather tricky, so we'd need
> INTEL_VGT_IF_VERSION minor increment and also a one line change
> (zeroing of the new caps register) from gvt code to the same patch,
> otherwise bisecting will break.
> 

That's unfortunate...We can't increment minor now as it would break
older guest, need to fix guest pvinfo version compat check, and new caps
field is kept as zero if not used, so now depend on that for compatibility.

-- 
Open Source Technology Center, Intel ltd.

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