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

[Laine Stump <laine@redhat.com>]

On 6/4/19 9:43 AM, 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.

I'm pretty sure RHV/oVirt+vdsm has implemented it and it is even being 
used in production. Of course it requires a bond/team device to be 
configured in the guest OS, but the part about auto-detaching the VF 
before migration, then reattaching a similar VF on the destination is 
all done by vdsm. (Don't misunderstand this as discouraging this new 
method! Just wanted to set the record straight.)