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Re: [Xen-devel] Re: migration of pv guest fails from small to large host

To: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Subject: Re: [Xen-devel] Re: migration of pv guest fails from small to large host
From: Olaf Hering <olaf@xxxxxxxxx>
Date: Thu, 7 Jul 2011 23:02:25 +0200
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On Thu, Jul 07, Konrad Rzeszutek Wilk wrote:

> On Thu, Jul 07, 2011 at 06:20:42AM -0700, Olaf Hering wrote:
> > On Tue, Jul 05, Konrad Rzeszutek Wilk wrote:
> > 
> > > On Fri, Jul 01, 2011 at 06:20:23PM +0200, Olaf Hering wrote:
> > > > 
> > > > The situation with Linux 3.0 is different, crashes on target. With 
> > > > SLES11
> > > > kernel I can not attach to the console, the guest is appearently 
> > > > running.
> > > 
> > > What happens if you 'xl save', 'xl restore' on the same machine? Does 
> > > that work?
> > 
> > save/restore on the same system works, just any form of transit from
> > small to large fails.
> I am not sure what 'small' to 'large' means in this context? As in the
> migration from a machine with less memory than than the other? What happens
> if you migratte the other way? Does it work if you use the old style 'xm' 
> commands?

xm or xl make no difference, they call the same helper function.
If the guest is started on a large system (>64GB), then migrated to a
small system (<64GB) and back to the large system nothing bad happens.
But if the guest is started on the small system, then migrated to the
large system the guest either crashes or hangs, depending on the guest
kernel. So far I have no handle what actually happens. Doing a dump
fails because the p2m stuff is not yet configured by the guest.

Today I wrote some debug code to get some tracing info, which I need to


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