linux-kernel - Re: KVM timekeeping fixes, V2

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Message-ID: <4C430E23.9070707@redhat.com>
Date:	Sun, 18 Jul 2010 17:22:27 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Joerg Roedel <joro@...tes.org>
CC:	Zachary Amsden <zamsden@...hat.com>, KVM <kvm@...r.kernel.org>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Glauber Costa <glommer@...hat.com>,
	Linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: KVM timekeeping fixes, V2

On 07/16/2010 10:26 PM, Joerg Roedel wrote:
> On Fri, Jul 16, 2010 at 07:20:32AM -1000, Zachary Amsden wrote:
>
>    
>> I've been very careful to keep nested SVM safe, but I've not got a good
>> test for that.  Is there any test suite for the nested case?
>>      
> To test this you can boot a nested Linux guest and let both, L1 and L2
> guest use kvm_clock. Then put some load into the L2 guest and see if the
> L2 or the L1 freezes hard (which happens with kvm_clock when the TSC
> went backwards for one of them).
>
>    

With recent guests, they won't freeze any more, since we detect the tsc 
going backwards and compensate (in a brute-force way, nothing clever).

But you can printk the maximum compensation and see if it's something 
unreasonable.

-- 
error compiling committee.c: too many arguments to function

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