Re: [Xen-devel] pv 2.6.31 (kernel.org) and save/migrate

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Fri, Nov 06, 2009 at 04:08:26PM -0800, Dan Magenheimer wrote:
> > On Fri, Nov 06, 2009 at 02:27:27PM -0800, Dan Magenheimer wrote:
> > > > On Fri, Nov 06, 2009 at 10:37:49AM -0800, Dan Magenheimer wrote:
> > > > > Sorry for another possibly stupid question:
> > > > > 
> > > > > I've observed that for a pv domain that's been updated
> > > > > to a 2.6.31 kernel (straight from kernel.org), "xm save"
> > > > > never completes.  When the older kernel (2.6.18)
> > > > > is booted, "xm save" works fine.  Is this a known problem...
> > > > > or perhaps xm save has never worked with an upstream pv
> > > > > kernel and I've never noticed?
> > > > > 
> > > > > I'd assume migrate and live migrate would fail also but
> > > > > haven't tried them.
> > > > > 
> > > > 
> > > > Just checking.. are you running the latest 2.6.31.5 ? I think 
> > > > there has
> > > > been multiple xen related bugfixes in the 2.6.31.X releases.
> > > > 
> > > > -- Pasi
> > > 
> > > No it was plain 2.6.31.  But I downloaded/built 2.6.31.5 and
> > > can't even get it to boot (and no console or VNC output at
> > > all).  Are CONFIG changes required betwen 2.6.31 and 2.6.31.5
> > > for Xen?  (I checked and I am using the same .config.)
> > > 
> > > Trying to reproduce on a different machine, just to verify.
> > 
> > There shouldn't be any .config changes needed.
> > 
> > Can you paste the full domU console output? Does it crash or? 
> > 
> > -- Pasi
> 
> Well, first, I got 2.6.31.5 to boot in a PV guest in another
> machine and it fails to save also.  Are you able to save
> 2.6.31{,.5} successfully?  On latest xen-unstable?
> (NOTE: Yes, I do have CONFIG_XEN_SAVE_RESTORE=y... don't
> know if that is important.)
> 

I'll have to try it later today..

> (On the machine I couldn't boot 2.6.31.5 as a PV guest, there
> was absolutely no console output.  However, I think tools
> are out-of-date on that machine so ignore that.)

Did you have "console=hvc0 earlyprintk=xen" in the domU kernel
parameters?

You might also change the xen guest cfgfile so that you have
on_crash=preserve and then when the PV guest is crashed run this:

/usr/lib/xen/bin/xenctx -s System.map-domUkernelversion <domid>

(if you have 64b host the xenctx binary might be under /usr/lib64/)

to get a stack trace..

-- Pasi


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