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

On 1/3/2018 9:43 AM, Michael S. Tsirkin wrote:

On Tue, Jan 02, 2018 at 04:35:37PM -0800, Sridhar Samudrala wrote:

quoted

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.

quoted

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