On Mon, Jan 23, 2023 at 01:00:22PM +0100, Laurent Vivier wrote:
> 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.
And then what exactly happens? Does hardware drop the outgoing
or the incoming packets? Pls include in the commit log.
> Signed-off-by: Laurent Vivier <lviv...@redhat.com>
> ---
> drivers/net/virtio_net.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 7723b2a49d8e..4bdc8286678b 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -3800,6 +3800,8 @@ static int virtnet_probe(struct virtio_device *vdev)
> eth_hw_addr_set(dev, addr);
> } 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 */
> @@ -3956,6 +3958,18 @@ static int virtnet_probe(struct virtio_device *vdev)
> pr_debug("virtnet: registered device %s with %d RX and TX vq's\n",
> dev->name, max_queue_pairs);
>
> + /* a random MAC address has been assigned, notify the device */
> + if (!virtio_has_feature(vdev, VIRTIO_NET_F_MAC) &&
> + virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_MAC_ADDR)) {
Maybe add a comment explaining that we don't fail probe if
VIRTIO_NET_F_CTRL_MAC_ADDR is not there because
many devices work fine without getting MAC explicitly.
> + 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)) {
> + dev_warn(&vdev->dev, "Failed to update MAC address.\n");
Here, I'm not sure we want to proceed. Is it useful sometimes?
I note that we deny with virtnet_set_mac_address.
> + }
> + }
> +
> return 0;
Also, some code duplication with virtnet_set_mac_address here.
Also:
When using the legacy interface, \field{mac} is driver-writable
which provided a way for drivers to update the MAC without
negotiating VIRTIO_NET_F_CTRL_MAC_ADDR.
How about factoring out code in virtnet_set_mac_address
and reusing that?
This will also handle corner cases such as VIRTIO_NET_F_STANDBY
which are not currently addressed.
> free_unregister_netdev:
> --
> 2.39.0
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