Re: [Xen-devel] [PATCH 1/3] Nested VMX: update nested paging mode when vmswitch is in progress

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

Zhang, Yang Z wrote on 2013-12-13:
> Egger, Christoph wrote on 2013-12-12:
>> On 12.12.13 03:06, Yang Zhang wrote:
>>> From: Yang Zhang <yang.z.zhang@xxxxxxxxx>
>>> 
>>> virtual vmentry will change paging related stucture, so
>>> corrensponding nested mode need to be updated which is missing currently.
>>> 
>>> Signed-off-by: Yang Zhang <yang.z.zhang@xxxxxxxxx>
>> 
>> I weakly remember the "!nestedhvm_vmswitch_in_progress" is needed to
>> avoid a nested pagefault loop on AMD. I do not remember the actual
>> reproduction case. Unfortunately, I do not have a setup to verify.
> 
> So you mean if CR0.PG bit is changed during vmentry, there is no need
> to update nested paging mode on AMD?
> Consider that, if the nested VCPU is scheduled from ETP to shadow and
> you don't update the nested paging mode, then it will cause problem,
> and vice versa.

Hi, Christoph,

Any concern with this patch?

Best regards,
Yang


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