Re: [Xen-devel] [PATCH 3/4 V3] X86: MPX IA32_BNDCFGS msr handle

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 27.11.13 at 14:57, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
> On 27/11/13 13:50, Liu, Jinsong wrote:
>> From 291adaf4ad6174c5641a7239c1801373e92e9975 Mon Sep 17 00:00:00 2001
>> From: Liu Jinsong <jinsong.liu@xxxxxxxxx>
>> Date: Thu, 28 Nov 2013 05:26:06 +0800
>> Subject: [PATCH 3/4 V3] X86: MPX IA32_BNDCFGS msr handle
>>
>> When MPX supported, a new guest-state field for IA32_BNDCFGS
>> is added to the VMCS. In addition, two new controls are added:
>>  - a VM-exit control called "clear BNDCFGS"
>>  - a VM-entry control called "load BNDCFGS."
>> VM exits always save IA32_BNDCFGS into BNDCFGS field of VMCS.
>>
>> Signed-off-by: Xudong Hao <xudong.hao@xxxxxxxxx>
>> Reviewed-by: Liu Jinsong <jinsong.liu@xxxxxxxxx>
>>
>> Unlikely, but in case VMX support is not available, not expose
>> MPX to hvm guest.
> 
> You are still missing the point.
> 
> I as the administrator choose to prevent an HVM guest from using MPX. 
> Perhaps I want to create a heterogeneous pool.
> 
> Therefore, the bit is disabled in the domains cpuid policy, despite
> being available on the hardware.

I think that with this latest version of the patch this is of no concern
anymore, or if it was it'd require a per-guest VM entry control
setting rather than a global one.

Jan


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