Re: [Qemu-devel] [virtio-dev] [PATCH 4/4] virtio-net: add linkspeed and duplex settings to virtio-net

[Michael S. Tsirkin]

On Tue, Mar 06, 2018 at 01:02:06PM -0500, Jason Baron wrote:
> 
> 
> On 03/04/2018 08:05 AM, Yan Vugenfirer wrote:
> > 
> > 
> >> On 2 Mar 2018, at 22:19, Michael S. Tsirkin <address@hidden
> >> <mailto:address@hidden>> wrote:
> >>
> >> On Fri, Mar 02, 2018 at 03:14:01PM +0800, Jason Wang wrote:
> >>>
> >>>
> >>> On 2018年03月02日 11:46, Jason Baron wrote:
> >>>> Although linkspeed and duplex can be set in a linux guest via
> >>>> 'ethtool -s',
> >>>> this requires custom ethtool commands for virtio-net by default.
> >>>>
> >>>> Introduce a new feature flag, VIRTIO_NET_F_SPEED_DUPLEX, which allows
> >>>> the hypervisor to export a linkspeed and duplex setting. The user can
> >>>> subsequently overwrite it later if desired via: 'ethtool -s'.
> >>>>
> >>>> Linkspeed and duplex settings can be set as:
> >>>> '-device virtio-net,speed=10000,duplex=full'
> >>>
> >>> I was thinking whether or not it's better to decide the duplex by the
> >>> type
> >>> of backends.
> >>>
> >>> E.g userspace and vhost-kernel implement a in fact half duplex. But dpdk
> >>> implement a full duplex.
> >>>
> >>> Thanks
> >>
> >> OTOH it's a priority for some people to be able to support migration
> >> between different backend types. Breaking that won't be nice.
> > 
> > I think that in this case we need a way to update the settings of link
> > speed and link duplex (maybe add QMP command). Migration between
> > different backend types should cause link down\link up events. And this
> > is a time for a driver to re-read the settings and update the OS.
> > 
> > Best regards,
> > Yan.
> > 
> 
> So the virtio_net driver in linux will re-read these settings on link up
> events. So I could add a qmp command to set these (in addition to the
> command-line) interface, if desired. Is there a consensus that we need
> to add a qmp command here? Or can that be treated as a future item, if
> somebody wants it?
> 
> Thanks,
> 
> -Jason

We already have ability to take link down and up.
I'd say it's a future item.

-- 
MST