Re: [Xen-devel] Intentional EPT Misconfigurations in xen

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.12.16 at 03:12, <tww20123030@xxxxxxxxx> wrote:
> Thanks a lot. I find that if guest writes or reads MSR related to
> MTRR which will cause vm exit, xen will just calculate mtrr type and store
> it without setting the EPT. Why doesn't xen set the memory type (ie,emt
> filed)in entry of EPT when handling vm exit resulting from writing/reading
> MSR related to MTRR?

Because that could take an (almost) unbounded amount of time,
as we'd have to process potentially very many EPT entries.

> I also find that xen will get the field of corresponding entries properly
> set when handling EPT Misconfigurations. But memory type related to these
> entries may be changed by guest after xen dose this. So how do we handle
> these properly configured EPT entries which don't cause EPT
> Misconfigurations any more when the memory type is changed by guest?

By marking the whole tree mis-configured again.

Jan


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