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

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

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.

Best regards,
Yang


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