Re: [Qemu-devel] [PATCH 0/4] Fix QEMU crash on vhost-user socket disconnect.

[Ilya Maximets <i.maximets@samsung.com>]

------- Original Message -------
Sender : Michael S. Tsirkin<mst@redhat.com>
Date : Apr 05, 2016 13:46 (GMT+03:00)
Title : Re: [PATCH 0/4] Fix QEMU crash on vhost-user socket disconnect.

> On Thu, Mar 31, 2016 at 09:02:01AM +0300, Ilya Maximets wrote:
> > On 30.03.2016 20:01, Michael S. Tsirkin wrote:
> > > On Wed, Mar 30, 2016 at 06:14:05PM +0300, Ilya Maximets wrote:
> > >> Currently QEMU always crashes in following scenario (assume that
> > >> vhost-user application is Open vSwitch with 'dpdkvhostuser' port):
> > > 
> > > In fact, wouldn't the right thing to do be stopping the VM?
> > 
> > I don't think that is reasonable to stop VM on failure of just one of
> > network interfaces.
> 
> We don't start QEMU until vhost user connects, either.
> Making guest run properly with a backend is a much bigger
> project, let's tackle this separately.
> 
> Also, I think handling graceful disconnect is the correct first step.
> Handling misbehaving clients is much harder as we have asserts on remote
> obeying protocol rules all over the place.
> 
> > There may be still working vhost-kernel interfaces.
> > Even connection can still be established if vhost-user interface was in
> > bonding with kernel interface.
> 
> Could not parse this.
>
> > Anyway user should be able to save all his data before QEMU restart.
>
> So reconnect a new backend, and VM will keep going.

We cant't do this because of 2 reasons:
1. Segmentation fault of QEMU on disconnect. (fixed by this patch-set)
2. There is no reconnect functionality in current QEMU version.

So, what are you talking about?

Best regards, Ilya Maximets.