Re: [Qemu-devel] [PATCH 1/1] migration: announce VM's new home just before VM is runnable

[Amit Shah]

On (Wed) 14 Oct 2015 [17:12:44], Michael S. Tsirkin wrote:
> On Wed, Oct 14, 2015 at 03:21:15PM +0200, Juan Quintela wrote:
> > Amit Shah <address@hidden> wrote:
> > > We were announcing the dest host's IP as our new IP a bit too soon -- if
> > > there were errors detected after this announcement was done, the
> > > migration is failed and the VM could continue running on the src host --
> > > causing problems later.
> > >
> > > Move around the qemu_announce_self() call so it's done just before the
> > > VM is runnable.
> > >
> > > Signed-off-by: Amit Shah <address@hidden>
> > 
> > Reviewed-by: Juan Quintela <address@hidden>
> > 
> > applied.
> > 
> > I have the same question than Dave, but also agree that this is a
> > movement in the right direction.
> > 
> > Why it is not only needed when we do a vm_start()?
> 
> It's a complex question.  We don't want to do this on each
> vmstop/vmcont. But maybe we want to, on the 1st vmstart after
> qemu is started.

Why?  When a guest starts, it will issue ARP requests and everything
will just work.  We need this announce_self only to tell the switches
that the MAC belonging to the guest's IP has changed..

                Amit