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

[Eduardo Habkost]

On Thu, Dec 06, 2018 at 10:01:46AM +0000, Daniel P. Berrangé wrote:
> Users absolutely *do* care why migration is not finishing. A migration that
> does not finish is a major problem for mgmt apps in many case of the use
> cases for migration. Especially important when evacuating VMs from a host
> in order to do a software upgrade or replace faulty hardware. As mentioned
> previously, they will also often serialize migrations to prevent eh network
> being overutilized, so a migration that runs indefinitely will stall
> evacuation of additional VMs too.  Predictable execution of migration and
> clear error reporting/handling are critical features. IMHO this is the key
> reason VFIO unplug/plug needs to be done explicitly by the mgmt app, so it
> can be in control over when each part of the process takes place.

On Fri, Apr 05, 2019 at 09:56:29AM +0100, Dr. David Alan Gilbert wrote:
> Why not just let this happen at the libvirt level; then you do the
> hotunplug etc before you actually tell qemu anything about starting a
> migration?

On Thu, May 30, 2019 at 07:00:23PM +0100, Dr. David Alan Gilbert wrote:
> Well no, we need to know this thing isn't going to hang in the migration
> setup phase, or if it does how we recover.  This patch series is very
> odd precisely because it's trying to do the unplug itself in the
> migration phase rather than let the management layer do it - so unless
> it's nailed down how to make sure that's really really bullet proof
> then we've got to go back and ask the question about whether we should
> really fix it so it can be done by the management layer.
> 

I have the impression we are running in circles here.

-- 
Eduardo