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

[Jason Wang]

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
> -     return 0;
> +     return ret;
>  }
> 
>  static struct rtnl_link_stats64 *virtnet_stats(struct net_device *dev,
> @@ -1627,6 +1636,7 @@ static unsigned int features[] = {
>       VIRTIO_NET_F_MRG_RXBUF, VIRTIO_NET_F_STATUS, VIRTIO_NET_F_CTRL_VQ,
>       VIRTIO_NET_F_CTRL_RX, VIRTIO_NET_F_CTRL_VLAN,
>       VIRTIO_NET_F_GUEST_ANNOUNCE, VIRTIO_NET_F_MQ,
> +     VIRTIO_NET_F_CTRL_MAC_ADDR,
>  };
> 
>  static struct virtio_driver virtio_net_driver = {
> diff --git a/include/uapi/linux/virtio_net.h
> b/include/uapi/linux/virtio_net.h index 848e358..a5a8c88 100644
> --- a/include/uapi/linux/virtio_net.h
> +++ b/include/uapi/linux/virtio_net.h
> @@ -53,6 +53,7 @@
>                                        * network */
>  #define VIRTIO_NET_F_MQ      22      /* Device supports Receive Flow
>                                        * Steering */
> +#define VIRTIO_NET_F_CTRL_MAC_ADDR 23        /* Set MAC address */
> 
>  #define VIRTIO_NET_S_LINK_UP 1       /* Link is up */
>  #define VIRTIO_NET_S_ANNOUNCE        2       /* Announcement is needed */
> @@ -127,7 +128,7 @@ typedef __u8 virtio_net_ctrl_ack;
>   #define VIRTIO_NET_CTRL_RX_NOBCAST      5
> 
>  /*
> - * Control the MAC filter table.
> + * Control the MAC
>   *
>   * The MAC filter table is managed by the hypervisor, the guest should
>   * assume the size is infinite.  Filtering should be considered
> @@ -140,6 +141,10 @@ typedef __u8 virtio_net_ctrl_ack;
>   * first sg list contains unicast addresses, the second is for multicast.
>   * This functionality is present if the VIRTIO_NET_F_CTRL_RX feature
>   * is available.
> + *
> + * The ADDR_SET command requests one out scatterlist, it contains a
> + * 6 bytes MAC address. This functionality is present if the
> + * VIRTIO_NET_F_CTRL_MAC_ADDR feature is available.
>   */
>  struct virtio_net_ctrl_mac {
>       __u32 entries;
> @@ -148,6 +153,7 @@ struct virtio_net_ctrl_mac {
> 
>  #define VIRTIO_NET_CTRL_MAC    1
>   #define VIRTIO_NET_CTRL_MAC_TABLE_SET        0
> + #define VIRTIO_NET_CTRL_MAC_ADDR_SET         1
> 
>  /*
>   * Control VLAN filtering