linux-kernel - Re: [PATCH 04/17] Fix deep C-state TSC desynchronization

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Message-ID: <4C191B5F.7080109@redhat.com>
Date:	Wed, 16 Jun 2010 08:43:43 -1000
From:	Zachary Amsden <zamsden@...hat.com>
To:	Jason Wang <jasowang@...hat.com>
CC:	avi@...hat.com, mtosatti@...hat.com, glommer@...hat.com,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 04/17] Fix deep C-state TSC desynchronization

On 06/15/2010 10:10 PM, Jason Wang wrote:
> Zachary Amsden wrote:
>    
>> When CPUs with unstable TSCs enter deep C-state, TSC may stop
>> running.  This causes us to require resynchronization.  Since
>> we can't tell when this may potentially happen, we assume the
>> worst by forcing re-compensation for it at every point the VCPU
>> task is descheduled.
>>
>>
>>      
> Is there any method to do the compensation on host TSC when recovering
> from C-state? It should be simpler than do it on guest TSC.
>    

Actually, yes, we could re-calibrate from HPET.  Considering this patch 
is already broken, maybe that's a better idea.
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