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

Amos Kong
2013-01-16T05:23:26Z

On Thu, Jan 10, 2013 at 10:57:05PM +0800, Jason Wang wrote:
> On 01/10/2013 10:45 PM, akong@redhat.com wrote:
> > From: Amos Kong <akong@redhat.com>
> >
> > 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 <akong@redhat.com>
> > ---
> > drivers/net/virtio_net.c | 16 +++++++++++++++-
> > include/uapi/linux/virtio_net.h | 8 +++++++-
> > 2 files changed, 22 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index 395ab4f..ff22bcd 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -803,13 +803,26 @@ static int virtnet_set_mac_address(struct net_device *dev, void *p)
> > struct virtio_device *vdev = vi->vdev;
> > int ret;
> >
> > + 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)) {
> > + /* Set MAC address by sending vq command */
> > + sg_init_one(&sg, dev->dev_addr, dev->addr_len);
> > + virtnet_send_command(vi, VIRTIO_NET_CTRL_MAC,
> > + VIRTIO_NET_CTRL_MAC_ADDR_SET,
> > + &sg, 1, 0);
> > + return 0;
> > + }
> > +
>
> Better to check the return of virtnet_send_command() and give a warn
> like other command. Btw, need we fail back to try the old way then?

Yes, it's necessary to check the return value of
virtnet_send_command().

In fail case, I like to return -EINVAL to userspace, because we don't
only want to set mac successfully, we also want to resolve the
addr inconsistent issue by this feature (vq cmd).