From mboxrd@z Thu Jan  1 00:00:00 1970
From: Avi Kivity <avi@argo.co.il>
Subject: Re: [kvm-devel] Guest kernel hangs in smp kvm for older kernels	prior
 to tsc sync cleanup
Date: Wed, 19 Dec 2007 16:27:19 +0200
Message-ID: <47692A47.4040803@argo.co.il>
References: <47680173.6060606@qumranet.com> <20071218221930.GA26109@elte.hu> <4768BB43.1000609@qumranet.com> <4768FE27.7020305@qumranet.com> <47690304.1090903@qumranet.com> <20071219140624.GF21282@elte.hu>
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Cc: Avi Kivity <avi@qumranet.com>,
	kvm-devel <kvm-devel@lists.sourceforge.net>,
	linux-kernel <linux-kernel@vger.kernel.org>
To: Ingo Molnar <mingo@elte.hu>
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In-Reply-To: <20071219140624.GF21282@elte.hu>
Sender: linux-kernel-owner@vger.kernel.org
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Ingo Molnar wrote:
> * Avi Kivity <avi@qumranet.com> wrote:
>
>   
>> Avi Kivity wrote:
>>     
>>>  Testing shows wrmsr and rdtsc function normally.
>>>
>>> I'll try pinning the vcpus to cpus and see if that helps.
>>>
>>>       
>> It does.
>>     
>
> do we let the guest read the physical CPU's TSC? That would be trouble.
>
>   

vmx (and svm) allow us to add an offset to the physical tsc.  We set it 
on startup to -tsc (so that an rdtsc on boot would return 0), and 
massage it on vcpu migration so that guest rdtsc is monotonic.

The net effect is that tsc on a vcpu can experience large forward jumps 
and changes in rate, but no negative jumps.

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