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


  • To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxx>
  • From: "Tian, Kevin" <kevin.tian@xxxxxxxxx>
  • Date: Thu, 27 Jul 2017 06:11:50 +0000
  • Accept-language: en-US
  • Cc: "Nakajima, Jun" <jun.nakajima@xxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxx>
  • Delivery-date: Thu, 27 Jul 2017 06:12:02 +0000
  • Dlp-product: dlpe-windows
  • Dlp-reaction: no-action
  • Dlp-version: 10.0.102.7
  • List-id: Xen developer discussion <xen-devel.lists.xen.org>
  • Thread-index: AQHTAIZLs9p8UWHf7k6b5acvh5JRcaJnPN8w
  • Thread-topic: [PATCH 5/6] x86/vvmx: Fix handing of the MSR_BITMAP field with VMCS shadowing

> 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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