Re: kvm-84 + virtio Ubuntu Hardy guests

[Mark McLoughlin <markmc@redhat.com>]

On Mon, 2009-04-06 at 09:55 -0700, Dustin Kirkland wrote:
> On Tue, Mar 31, 2009 at 5:28 PM, Dustin Kirkland <kirkland@canonical.com> wrote:
> > I'm receiving a heavy volume of Ubuntu Jaunty Beta users reporting
> > that Jaunty hosts running kvm-84 (userspace and kernel) are not able
> > to boot previously-working Hardy guests (2.6.24 kernel) if virtio
> > networking is enabled [1].  Users report that if e1000 is used
> > instead, the guest is able to boot (with degraded network performance,
> > obviously).  Users are also reporting that this was not a problem when
> > kvm-82 was used in Jaunty (though we also merged libvirt 0.5.1 up to
> > 0.6.0 in roughly the same timeframe).
> ...
> > [1] https://bugs.launchpad.net/ubuntu/+source/kvm/+bug/331128
> 
> Howdy-
> 
> Just a follow-up...
> 
> Anthony was able to confirm this issue, and create a patch for KVM,
> which we're carrying in Ubuntu.  It's a bit of a special-case hack,
> but I'm dropping it here for the sake of completeness.
> 
> Basically, Hardy guests do not have working GSO (general segment
> offload) support.  Some changes in kvm/libvirt appear to be exposing
> this, and breaking some guests when running virtio.
> 
> This patch from Anthony basically disables this support in KVM
> userspace (until we have a better solution for auto-detecting GSO
> support or lack thereof).

The problem here is that 2.6.24/5 vintage guests are saying they support
something they don't. See this for further details:

http://lists.gnu.org/archive/html/qemu-devel/2009-01/msg00574.html

Cheers,
Mark.