Re: [Qemu-devel] [PATCH 3/4] net/virtio: add failover support

[Eduardo Habkost <ehabkost@redhat.com>]

On Tue, Jun 04, 2019 at 03:43:21PM +0200, Jens Freimann wrote:
> On Mon, Jun 03, 2019 at 04:36:48PM -0300, Eduardo Habkost wrote:
> > On Mon, Jun 03, 2019 at 10:24:56AM +0200, Jens Freimann wrote:
> > > On Fri, May 31, 2019 at 06:47:48PM -0300, Eduardo Habkost wrote:
> > > > On Thu, May 30, 2019 at 04:56:45PM +0200, Jens Freimann wrote:
> > > > > On Tue, May 28, 2019 at 11:04:15AM -0400, Michael S. Tsirkin wrote:
> > > > > > On Tue, May 21, 2019 at 10:45:05AM +0100, Dr. David Alan Gilbert wrote:
> > > > > > > * Jens Freimann (jfreimann@redhat.com) wrote:
> > > Why is it bad to fully re-create the device in case of a failed migration?
> > 
> > Bad or not, I thought the whole point of doing it inside QEMU was
> > to do something libvirt wouldn't be able to do (namely,
> > unplugging the device while not freeing resources).  If we are
> > doing something that management software is already capable of
> > doing, what's the point?
> 
> Event though management software seems to be capable of it, a failover
> implementation has never happened. As Michael says network failover is
> a mechanism (there's no good reason not to use a PT device if it is
> available), not a policy. We are now trying to implement it in a
> simple way, contained within QEMU.

I don't think this is a strong enough reason to move complexity
to QEMU.

This might look like it's reducing complexity in the
QEMU<->libvirt interface, but having QEMU unplugging/plugging
devices automatically without libvirt involvement is actually
complicating that interface.

That said, I won't try to prevent this from being merged if the
maintainers and libvirt developers agree on this interface.

-- 
Eduardo