Re: [Xen-users] Cannot start domains after FC6->F7 upgrade

["Daniel P. Berrange" <berrange@xxxxxxxxxx>]

On Fri, Jun 29, 2007 at 01:30:01AM +0100, Mark Williamson wrote:
> > > Did you reboot with the new Xen kernel? Or did you pull your kernel or
> > > assemble it form elsewhere?
> >
> > Yes.  Standard xen kernel.  But had to use the FC6 xen kernel because
> > the F7 xen kernel crashes on our hardware.
> >
> > > My local mirror does not have FC7 yet, so I haven't been able to play
> > > with it.
> >
> > I've opened a Fedora bug:
> > https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=246169
> 
> Chiming in here; I don't have a RH bugzilla account.
> 
> The matching rules for kernel / tools / xen versions are a bit complex.  The 
> userspace tools and Xen itself must *always* be matched.
> 
> Since around 3.0.4 (I think?) it's been possible to mix and match dom0 kernel 
> versions.  i.e. any dom0 kernel since 3.0.4 should run on any Xen from 3.0.4. 
>  
> Before that release the dom0 and Xen interfaces were tied together and you 
> couldn't really mix and match /at all/.  Although you couldn't strictly mix 
> and match, you could sometimes get dom0 to boot on Xen, but things didn't 
> work properly - this may be what you're seeing, I guess.

Since we distribute the hypervisor as part of kernel-xen, this is kinda
academic. For Fedora we guarentee that we will never update the Xen 
hypervisor version within the course of a major release, so as a general
rule users don't have to worry about incompatabilities between 'xen' and
'kernel-xen' if applying updates to the distro.  The problem in this case 
was that there was a mix of packages from two different distros - F7 and 
FC6 between xen & kernel-xen RPMs which is not guarenteed to work because
of lack of a stable ABI in Xen. 

This whole issue could be avoided if just a tiny bit more care were taken
in Xen hypervisor development to maintain a back-compat ABI.  You don't 
expect your GLibC to break when you update to a new kernel - but that's 
exactly the situation we're in with Xen where updating a HV breaks your
userspace :-(

Dan.
-- 
|=- Red Hat, Engineering, Emerging Technologies, Boston.  +1 978 392 2496 -=|
|=-           Perl modules: http://search.cpan.org/~danberr/              -=|
|=-               Projects: http://freshmeat.net/~danielpb/               -=|
|=-  GnuPG: 7D3B9505   F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505  -=| 

_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users