Re: [PATCH 0/4 for 2.3] vhost-user live migration support

[Yuanhan Liu <yuanhan.liu@linux.intel.com>]

On Mon, Dec 14, 2015 at 11:58:42AM +0800, Peter Xu wrote:
> On Fri, Dec 11, 2015 at 01:22:23PM +0300, Pavel Fedin wrote:
> >  BTW, it works, and it was my bad. openvswitch was configured incorrectly on the other side, vhost port number was different for
> > some reason, while ruleset was the same. I reconfigured it and now everything migrates correctly, except increased downtime because
> > of missing GARP (the guest misses some PINGs, then it retries ARP, which brings the link back up).
> 
> Hi,
> 
> When doing the ping, was it from the guest (to another host) or to
> the guest (from another host)?
> 
> In any case, I still could not understand why the ping loss happened
> in this test.
> 
> If ping from guest, no ARP refresh is required at all?
> 
> If ping to guest from outside, when the migration finishes on the
> target side of qemu, qemu_self_announce() will be called.

It's supposed to see some ARP requests if I run tcpdump against
with the ovs bridge, right? However, in fact, I saw nothing from
tcpdump on the target host when the migration is done.

I mean I do find that qemu_annouce_self composes an ARP
broadcoast request, but it seems that I didn't catch it on
the target host.

Something wrong, or someting I missed?

	--yliu

> Although
> we might see a warning like "Vhost user backend fails to broadcast
> fake RARP" (notify is done by hacking vhost_user_receive(), even if
> notify fails, things will still move on), QEMU should still send a
> RARP onto the link.
> 
> Not sure whether I missed anything.
> 
> Thanks.
> Peter