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

["Liu, Jinsong" <jinsong.liu@xxxxxxxxx>]

Andrew Cooper wrote:
> On 27/11/13 14:27, Liu, Jinsong wrote:
>> Andrew Cooper 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.
>>> 
>>> ~Andrew
>>> 
>> Could you tell me the reason why choose to prevent HVM from using
>> MPX? 
>> 
>> Thanks,
>> Jinsong
> 
> For exactly the case I gave - a VM in a heterogeneous pool where one
> server supports MPX and the other is lacking the MPX feature.
> 
> ~Andrew
> 

I didn't see the point of your case to prevent HVM MPX feature.
Could you elaborate more of your concern?

Thanks,
Jinsong
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