Re: [Xen-devel] [PATCH 5/7] x86/shadow: Use the pagewalk reserved bits helpers

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 01/03/17 16:03, Jan Beulich wrote:
>>>> On 27.02.17 at 15:03, <andrew.cooper3@xxxxxxxxxx> wrote:
>> The shadow logic should never create a shadow of a guest PTE which contains
>> reserved bits from the guests point of view.  Such a shadowed entry might not
>> cause #PF[RSVD] when walked by hardware, thus won't behave architecturally
>> from the guests point of view.
> But are we already or-ing in the RSVD bit accordingly in such cases,
> before handing the #PF to the guest? The patch here certainly
> doesn't make any change towards that, afaics.

The purpose of this patch is to ensure we never create a shadow which
risks causing hardware to generate #PF[RSVD] when running on the
shadows, other than the one deliberate case (MMIO fastpath).

~Andrew

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