Re: [PATCH net-next 1/2] virtio_net: Introduce VIRTIO_NET_F_MASTER feature bit

["Samudrala, Sridhar" <sridhar.samudrala@intel.com>]

On 1/3/2018 9:43 AM, Michael S. Tsirkin wrote:
> On Tue, Jan 02, 2018 at 04:35:37PM -0800, Sridhar Samudrala wrote:
> > This feature bit can be used by hypervisor to indicate virtio_net device to
> > act as a master for a directly attached passthru device with the same MAC
> > address.
> >
> > Signed-off-by: Sridhar Samudrala <sridhar.samudrala@intel.com>
> > ---
> >   drivers/net/virtio_net.c        | 3 ++-
> >   include/uapi/linux/virtio_net.h | 1 +
> >   2 files changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index 6fb7b658a6cc..46844a1d9a62 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -2796,7 +2796,8 @@ static struct virtio_device_id id_table[] = {
> >   	VIRTIO_NET_F_CTRL_RX, VIRTIO_NET_F_CTRL_VLAN, \
> >   	VIRTIO_NET_F_GUEST_ANNOUNCE, VIRTIO_NET_F_MQ, \
> >   	VIRTIO_NET_F_CTRL_MAC_ADDR, \
> > -	VIRTIO_NET_F_MTU, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS
> > +	VIRTIO_NET_F_MTU, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS, \
> > +	VIRTIO_NET_F_MASTER
> >   
> >   static unsigned int features[] = {
> >   	VIRTNET_FEATURES,
> > diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
> > index fc353b518288..a9b4e0836786 100644
> > --- a/include/uapi/linux/virtio_net.h
> > +++ b/include/uapi/linux/virtio_net.h
> > @@ -56,6 +56,7 @@
> >   #define VIRTIO_NET_F_MQ	22	/* Device supports Receive Flow
> >   					 * Steering */
> >   #define VIRTIO_NET_F_CTRL_MAC_ADDR 23	/* Set MAC address */
> > +#define VIRTIO_NET_F_MASTER	62	/* act as master for a VF device */
> Well the virtio hardware doesn't really know whether it's a master or
> the slave of a bond. In fact quite possibly down the road we'll add a
> virtual device on top as others seem to want to do - that other one will
> be the master then.
>
> And we do nothing do check it's a VF.
>
> So maybe a better name would be
>
> #define VIRTIO_NET_F_BACKUP	62	/* Act as backup for another device with the same MAC */
Yes. BACKUP  does make more sense as virtio is only used as a BACKUP 
datapath when the other
device is unplugged.


> >   
> >   #ifndef VIRTIO_NET_NO_LEGACY
> >   #define VIRTIO_NET_F_GSO	6	/* Host handles pkts w/ any GSO type */
> > --
> > 2.14.3