[Xen-devel] Re: [Xen-changelog] [xen-3.1-testing] xend: fix server/netif.py so that it respects type=None.

["Daniel P. Berrange" <berrange@xxxxxxxxxx>]

On Fri, Oct 05, 2007 at 01:21:24AM +0100, John Levon wrote:
> On Thu, Oct 04, 2007 at 08:40:16AM -0700, Xen patchbot-3.1-testing wrote:
> 
> > xend: fix server/netif.py so that it respects type=None.
> > Signed-off-by: Daniel P. Berrange <berrange@xxxxxxxxxx>
> > xen-unstable changeset:   15972:3a799196ff69d3a3d5e4a891c13434aa61ce60a9
> > xen-unstable date:        Thu Sep 27 17:44:03 2007 +0100
> >  
> > -        if not typ:
> > -            typ = xoptions.netback_type
> > -
> 
> Grumble, this makes xoptions.netback_type now clearly unused. I'm not
> sure whether this breaks us yet, but certainly there's either cleanup
> needed or it needs fixing.

It shouldn't break anything unless it was already broken.

Basically with type=None, then the in-memory VM would be booted with type
of None, but at the same time the VM config would be written out to disk
with type of 'netfront'. You could stop & start the HVM guest many times
and XenD would always use a type of None when configuring qemu/netback.
The moment you restarted XenD (or rebooted the machine), then it would read
the config in from disk & now see type=netfront. So your config which had
been working fine, suddenly changes when XenD is restarted & your qemu 
NICs disappear. So if this breaks anything for Solaris, then it must have
been broken all along, because this only changes the config written to disk,
not the in-memory one XenD is actuall using to start off with.

> What does type=None do?

The behaviour is

  - type == netfront  -> setup netback only
  - type == ioemu     -> setup qemu-dm only
  - type is None      -> setup netback & qemu-dm

The latter is the preferred behavour because it means the same VM config works
whether the guest is using the RTL8139 emulated NIC, or PV drivers.

Dan.
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