linux-kernel - Re: [kvm-devel] Guest kernel hangs in smp kvm for older kernelsprior to tsc sync cleanup

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Date:	Wed, 19 Dec 2007 19:09:48 +0200
From:	Avi Kivity <avi@...ranet.com>
To:	dor.laor@...ranet.com
CC:	Amit Shah <amit.shah@...ranet.com>,
	kvm-devel@...ts.sourceforge.net,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Avi Kivity <avi@...o.co.il>, Gerd Hoffmann <kraxel@...hat.com>
Subject: Re: [kvm-devel] Guest kernel hangs in smp kvm for older kernelsprior
 to tsc sync cleanup

Dor Laor wrote:
>> > >
>> > > 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.
>> >
>> > Changes in rate does not sound good. It's possibly what's screwing up
>> > my paravirt clock implementation in smp.
>>
>> Do you mean in the case of VM migration, or just starting them on a 
>> single
>> host?
>>
> It's the cpu preemption stuff on local host and not VM migration

No, migrating a vcpu to another cpu.

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

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