linux-kernel - Re: [PATCH 1/5] Add a global synchronization point for pvclock

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Message-ID: <1288090162.3530.0.camel@mothafucka.localdomain>
Date:	Tue, 26 Oct 2010 08:49:22 -0200
From:	Glauber Costa <glommer@...hat.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	Jeremy Fitzhardinge <jeremy@...p.org>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Zachary Amsden <zamsden@...hat.com>,
	"Xen-devel@...ts.xensource.com" <Xen-devel@...ts.xensource.com>
Subject: Re: [PATCH 1/5] Add a global synchronization point for pvclock

On Tue, 2010-10-26 at 10:14 +0200, Avi Kivity wrote:
> On 10/26/2010 01:30 AM, Jeremy Fitzhardinge wrote:
> > Unfortunately this is breaking Xen save/restore: if you restore on a
> > host which was booted more recently than the save host, causing the
> > system time to be smaller.  The effect is that the domain's time leaps
> > forward to a fixed point, and stays there until the host catches up to
> > the source host...
> 
> Shouldn't save/restore also save the timebase?
> 
> > I guess last_time needs to be reset on this type of event.  I guess the
> > cleanest way would be for pvclock.c to register a sysdev suspend/resume
> > handler.
> 
> Should be for Xen only; kvm save/restore doesn't involve the guest.

the suspend/resume path do adjust the time base. Maybe something similar
should be done ?


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