[Intel-gfx] [RFC 03/10] drm/i915/gvt: context submission pvmmio optimization

[Joonas Lahtinen]

Quoting Xiaolin Zhang (2018-09-27 19:37:48)
> It is performance optimization to reduce mmio trap numbers from 4 to
> 1 durning ELSP porting writing (context submission).
> 
> When context subission, to cache elsp_data[4] values in
> the shared page, the last elsp_data[0] port writing will be trapped
> to gvt for real context submission.
> 
> Use PVMMIO_ELSP_SUBMIT to control this level of pvmmio optimization.
> 
> Signed-off-by: Xiaolin Zhang <xiaolin.zhang at intel.com>

These changes are somewhat invasive to the ELSP submit path.

We should instead look into providing "pvgpu" (just a suggestion for
name) flavour of virtual functions which do the para-virtualized talking.
We don't want to sprinkle pv code around the driver with ifs.

Regards, Joonas