Re: [Xen-devel] [PATCH] VMX: Eliminate cr3 store/load vmexit when UG enabled

["Zhang, Yang Z" <yang.z.zhang@xxxxxxxxx>]

Andrew Cooper wrote on 2013-10-28:
> On 28/10/13 13:22, Jan Beulich wrote:
>>>>> On 24.10.13 at 06:41, "Zhang, Yang Z" <yang.z.zhang@xxxxxxxxx> wrote:
>>> Andrew Cooper wrote on 2013-10-23:
>>>> On 23/10/13 08:39, Yang Zhang wrote:
>>>>> From: Yang Zhang <yang.z.zhang@xxxxxxxxx>
>>>>> 
>>>>> With the feature of unrestricted guest, there should no vmexit be
>>>>> triggered when guest accesses the cr3 in non-paging mode.
>>>>> 
>>>>> Signed-off-by: Yang Zhang <yang.z.zhang@xxxxxxxxx>
>>>> You English here confused me for a bit.  I presume you mean "Xen
>>>> should not cause vmexits for cr3 accesses in unrestricted guests",
>>>> whereas the current meaning implies that hardware wont generate a
>>>> vmexit for cr3 accesses for unrestricted guests (which is not
>>>> correct
>>> according to the SDM).
>>> Apology for my poor English. Yes, your understanding is right.
>> So assuming we'll get an ack from one of the VMX maintainers, should
>> this then be committed with the suggested change to the description?
>> Also, Andrew, any more concerns regarding this change (IOW did Yang
>> address your earlier questions)?
>> 
>> Jan
>> 
> 
> I think so, but I really don't think I know the implications of the
> changes well enough to be happy giving it a Reviewed-by tag.

I will ask our QA to do a full testing against this patch to see whether it 
introduces any regression.

> 
> Given the clarification regarding the commit message, I shall defer to
> the maintainers for the correctness of the change.
> 
> ~Andrew


Best regards,
Yang



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