[PATCH] drm/i915/gvt: update guest page table even p2m faild

[He, Min]

Zhi, 
But we should do our best to avoid this situation. We had partial entry update in
ppgtt table, just because we updated wrong value into the PPGTT table. 

> -----Original Message-----
> From: Wang, Zhi A
> Sent: Wednesday, March 15, 2017 11:00 PM
> To: He, Min <min.he at intel.com>; Chen, Xiaoguang
> <xiaoguang.chen at intel.com>; intel-gvt-dev at lists.freedesktop.org
> Cc: Chen, Xiaoguang <xiaoguang.chen at intel.com>
> Subject: RE: [PATCH] drm/i915/gvt: update guest page table even p2m faild
> 
> Hi Min:
>     Even the GGTT entry is not correct, it's caused by guest itself. E.g. guest just
> writes part of the entry then use it, it's a fault of guest not us. For us, we try to
> translate the "partial" GPA when guest write the entry, if succeed, it means, the
> GPA is a part of guest RAM, we update the shadow GGTT, if guest use it, then it's
> a fault of guest. If the GPA is not a part of guest RAM we set the shadow to
> scratch page.
> 
> Thanks,
> Zhi.
> 
> -----Original Message-----
> From: intel-gvt-dev [mailto:intel-gvt-dev-bounces at lists.freedesktop.org] On
> Behalf Of He, Min
> Sent: Thursday, March 16, 2017 11:52 AM
> To: Chen, Xiaoguang <xiaoguang.chen at intel.com>; intel-gvt-
> dev at lists.freedesktop.org
> Cc: Chen, Xiaoguang <xiaoguang.chen at intel.com>
> Subject: RE: [PATCH] drm/i915/gvt: update guest page table even p2m faild
> 
> This patch may cause an incorrect value to be written to the GTT table.
> Do we have better solutions? For example, change back to the partial mode of
> the old vgt mode?
> 
> Thanks.
> 
> > -----Original Message-----
> > From: intel-gvt-dev
> > [mailto:intel-gvt-dev-bounces at lists.freedesktop.org] On Behalf Of
> > Xiaoguang Chen
> > Sent: Wednesday, March 15, 2017 7:09 PM
> > To: intel-gvt-dev at lists.freedesktop.org
> > Cc: Chen, Xiaoguang <xiaoguang.chen at intel.com>
> > Subject: [PATCH] drm/i915/gvt: update guest page table even p2m faild
> >
> > Sometimes guest driver will write the gtt mmio page table with length
> > of 4 while the entry size is 8. In this situation the p2m may failed.
> > Even the p2m failed we should update the guest gtt mmio page table but
> > not update the shadow gtt mmio page table.
> >
> > Signed-off-by: Xiaoguang Chen<xiaoguang.chen at intel.com>
> > Reviewed-by: Zhi Wang <zhi.a.wang at intel.com>
> 
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