virtio_net: notify MAC address change on device initialization

Bugzilla: http://bugzilla.redhat.com/2153210

commit 9f62d22
Author: Laurent Vivier <lvivier@redhat.com>
Date:   Fri Jan 27 21:45:00 2023 +0100

    virtio_net: notify MAC address change on device initialization

    In virtnet_probe(), if the device doesn't provide a MAC address the
    driver assigns a random one.
    As we modify the MAC address we need to notify the device to allow it
    to update all the related information.

    The problem can be seen with vDPA and mlx5_vdpa driver as it doesn't
    assign a MAC address by default. The virtio_net device uses a random
    MAC address (we can see it with "ip link"), but we can't ping a net
    namespace from another one using the virtio-vdpa device because the
    new MAC address has not been provided to the hardware:
    RX packets are dropped since they don't go through the receive filters,
    TX packets go through unaffected.

    Signed-off-by: Laurent Vivier <lvivier@redhat.com>
    Acked-by: Michael S. Tsirkin <mst@redhat.com>
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Conflict in the context because of missing commit:

    f2edaa4 ("net: virtio: use eth_hw_addr_set()")

Signed-off-by: Laurent Vivier <lvivier@redhat.com>

Author: vivier

drivers/net/virtio_net.c

@@ -3186,8 +3186,11 @@ static int virtnet_probe(struct virtio_device *vdev)
 		virtio_cread_bytes(vdev,
 				   offsetof(struct virtio_net_config, mac),
 				   dev->dev_addr, dev->addr_len);
-	else
+	else {
 		eth_hw_addr_random(dev);
+		dev_info(&vdev->dev, "Assigned random MAC address %pM\n",
+			 dev->dev_addr);
+	}
 
 	/* Set up our device-specific information */
 	vi = netdev_priv(dev);
@@ -3287,6 +3290,24 @@ static int virtnet_probe(struct virtio_device *vdev)
 
 	virtio_device_ready(vdev);
 
+	/* a random MAC address has been assigned, notify the device.
+	 * We don't fail probe if VIRTIO_NET_F_CTRL_MAC_ADDR is not there
+	 * because many devices work fine without getting MAC explicitly
+	 */
+	if (!virtio_has_feature(vdev, VIRTIO_NET_F_MAC) &&
+	    virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_MAC_ADDR)) {
+		struct scatterlist sg;
+
+		sg_init_one(&sg, dev->dev_addr, dev->addr_len);
+		if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_MAC,
+					  VIRTIO_NET_CTRL_MAC_ADDR_SET, &sg)) {
+			pr_debug("virtio_net: setting MAC address failed\n");
+			rtnl_unlock();
+			err = -EINVAL;
+			goto free_unregister_netdev;
+		}
+	}
+
 	rtnl_unlock();
 
 	err = virtnet_cpu_notif_add(vi);