Re: [virtio-dev] [PATCH 4/4] virtio-net: add linkspeed and duplex settin

On 2 Mar 2018, at 22:19, Michael S. Tsirkin <mst@redhat.com> 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.

where speed is [0...INT_MAX], and duplex is ["half"|"full"].

Signed-off-by: Jason Baron<jbaron@akamai.com>
Cc: "Michael S. Tsirkin"<mst@redhat.com>
Cc: Jason Wang<jasowang@redhat.com>
Cc:virtio-dev@lists.oasis-open.org
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