Re: [Qemu-devel] [PATCH v2 2/2] virtio-net: introduce a new control to set macaddr

[Amos Kong]

On Wed, Jan 16, 2013 at 02:20:39PM +0800, Jason Wang wrote:
> On Wednesday, January 16, 2013 01:57:01 PM address@hidden wrote:
> > From: Amos Kong <address@hidden>
> > 
> > Currently we write MAC address to pci config space byte by byte,
> > this means that we have an intermediate step where mac is wrong.
> > This patch introduced a new control command to set MAC address
> > in one time.
> > 
> > VIRTIO_NET_F_CTRL_MAC_ADDR is a new feature bit for compatibility.
> > 
> > Signed-off-by: Amos Kong <address@hidden>
> > ---
> >  drivers/net/virtio_net.c        | 24 +++++++++++++++++-------
> >  include/uapi/linux/virtio_net.h |  8 +++++++-
> >  2 files changed, 24 insertions(+), 8 deletions(-)
> > 
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index 395ab4f..c8901b6 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -802,16 +802,25 @@ static int virtnet_set_mac_address(struct net_device
> > *dev, void *p) struct virtnet_info *vi = netdev_priv(dev);
> >     struct virtio_device *vdev = vi->vdev;
> >     int ret;
> > +   struct sockaddr *addr = p;
> > +   struct scatterlist sg;
> > 
> > -   ret = eth_mac_addr(dev, p);
> > -   if (ret)
> > -           return ret;
> > -
> > -   if (virtio_has_feature(vdev, VIRTIO_NET_F_MAC))
> > +   if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_MAC_ADDR)) {
> > +           sg_init_one(&sg, addr->sa_data, dev->addr_len);
> > +           if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_MAC,
> > +                                     VIRTIO_NET_CTRL_MAC_ADDR_SET,
> > +                                     &sg, 1, 0)) {
> > +                   dev_warn(&vdev->dev,
> > +                            "Failed to set mac address by vq command.\n");
> > +                   return -EINVAL;
> > +           }
> > +   } else if (virtio_has_feature(vdev, VIRTIO_NET_F_MAC)) {
> >             vdev->config->set(vdev, offsetof(struct virtio_net_config, mac),
> > -                             dev->dev_addr, dev->addr_len);
> > +                             addr->sa_data, dev->addr_len);
> > +   }
> > +   ret = eth_mac_addr(dev, p);
> > 
> 
> The you will the validity check in eth_mac_addr which may result a wrong mac 
> address to be set in the hardware (or is there any check in qemu) and a 
> inconsistency bettween what kernel assumes and qemu has.
> 
> You can take a look at netvsc driver that calls eth_mac_addr() first and 
> restore the software mac address when fail to enforce it to hardware.

Thanks for the catching, I will move eth_mac_addr() back to above,
just restore addr if fail to send command.

I will also use DEFINE_PROP_BIT to fix migration issue, thanks.
 
> Thanks
> > -   return 0;
> > +   return ret;
> >  }