Re: [Xen-devel] [PATCH 5/6] x86/vvmx: Fix handing of the MSR_BITMAP field with VMCS shadowing

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Andrew Cooper [mailto:andrew.cooper3@xxxxxxxxxx]
> Sent: Wednesday, July 19, 2017 7:58 PM
> 
> Currently, the following sequence of actions:
> 
>  * VMPTRLD (creates a mapping, likely pointing at gfn 0 for an empty vmcs)
>  * VMWRITE CPU_BASED_VM_EXEC_CONTROL (completed by hardware)
>  * VMWRITE MSR_BITMAP (completed by hardware)
>  * VMLAUNCH
> 
> results in an L2 guest running with ACTIVATE_MSR_BITMAP set, but Xen
> using a
> stale mapping (likely gfn 0) when reading the interception bitmap.  The
> MSR_BITMAP field needs unconditionally intercepting even with VMCS
> shadowing,
> so Xen's mapping of the bitmap can be updated.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Acked-by: Kevin Tian <kevin.tian@xxxxxxxxx>

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