[libvirt] [PATCH v2 2/2] qemu: Default to virtio-net where available

[Daniel P. Berrange]

On Thu, Sep 03, 2015 at 09:36:47AM +0100, Daniel P. Berrange wrote:
> On Wed, Sep 02, 2015 at 04:08:52PM -0400, Laine Stump wrote:
> > On 09/02/2015 12:14 PM, Andrea Bolognani wrote:
> > >This applies to all architectures except for ARM, which already
> > >has its own logic to pick the best default.
> > >
> > >Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1254044
> > >---
> > >Changes from v1:
> > >
> > >   * make sure virtio-net is available using capabilities
> > >     instead of blindly using it (thanks Martin)
> > >
> > >   * change the default for all architectures (except arm)
> > >     instead of just ppc64
> > 
> > Are we certain we want to do this even for x86 guests? I don't think it's a
> > good idea - it makes the default into something for which no driver exists
> > on the install media for *many* x86 guests, meaning it is highly likely that
> > a "default" config would have non-functional networking. AFAIR this is why
> > we didn't make virtio the default several years ago when we began recording
> > a default into the XML (and why the last time changing the default was
> > discussed, I believe it was pointing more towards something like e1000, i.e.
> > something which 1) we are certain has a driver on every guest OS
> > installation media that might be found, 2) is better maintained in qemu than
> > the rtl8139, and 3) performs better than rtl8139 (although obviously not as
> > good as virtio).
> 
> Agreed, making virtio-net the default is a bad idea because the guest
> OS support for it is pretty limited to essentially just modern Linux
> guests out of the box. So nack to this patch.

Oh and I meant to say, the task of getting "optimal" defaults for the
various guest OS really falls to libosinfo, which has info on what
each OS is capable of using.

Regards,
Daniel
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