Re: [PATCH 1/4] virtio_net: notify MAC address change on device initialization

[Laurent Vivier]

On 1/22/23 14:47, Eli Cohen wrote:
> On 22/01/2023 12:05, 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.
> >
> > Signed-off-by: Laurent Vivier <lvivier@xxxxxxxxxx>
> > ---
> >   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..25511a86590e 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 (dev->addr_assign_type == NET_ADDR_RANDOM &&
> Maybe it's better to not count on addr_assign_type and use a local variable to indicate 
> that virtnet_probe assigned random MAC. The reason is that the hardware driver might have 
> done that as well and does not need notification.

eth_hw_addr_random() sets explicitly NET_ADDR_RANDOM, while eth_hw_addr_set() doesn't 
change addr_assign_type so it doesn't seem this value is set by the hardware driver.

So I guess it's the default value (NET_ADDR_PERM) in this case (even if it's a random 
address from the point of view of the hardware).

If you prefer I can replace it by "!virtio_has_feature(vdev, VIRTIO_NET_F_MAC)"?

Thanks,
Laurent