[Intel-gfx] [PATCHi v2] drm/i915: Enhanced disable access to stolen memory as a guest

[Zhang, Xiong Y]

> > Reviewed-by: Zhenyu Wang <zhenyuw at linux.intel.com>
> 
> Entirely disabling stolen is rather massive, this stuff is supposed to
> work ... There should be special RMRR mappings in the iommu to help the
> guest access the stolen range correctly from the gpu.
> 
> Which machine where does this blow up on?
> -Daniel
[Zhang, Xiong Y] Yes. Stolen memory is protected by RMRR on host. But Qemu couldn't support and don't have plan to support RMRR. Then EPT lack of mapping for stolen memory, guest couldn't access it.
The Qemu/Vfio is designed by Redhat engineers, Redhat has a white paper to explain why Qemu don't support RMRR:
https://access.redhat.com/sites/default/files/attachments/rmrr-wp1.pdf

> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch