Re: [Qemu-devel] [RFC v3 2/3] vhost-net: Notify the backend about the host MTU

[Aaron Conole <aconole@redhat.com>]

Maxime Coquelin <maxime.coquelin@redhat.com> writes:

> This patch provides a way for virtio-net to notify the
> backend about the host MTU set by the user.
>
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Aaron Conole <aconole@redhat.com>
> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> ---
>  hw/net/vhost_net.c      | 22 ++++++++++++++++++++++
>  include/net/vhost_net.h |  2 ++
>  2 files changed, 24 insertions(+)
>
> diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> index f2d49ad..d7c13d4 100644
> --- a/hw/net/vhost_net.c
> +++ b/hw/net/vhost_net.c
> @@ -51,6 +51,7 @@ static const int kernel_feature_bits[] = {
>      VIRTIO_RING_F_EVENT_IDX,
>      VIRTIO_NET_F_MRG_RXBUF,
>      VIRTIO_F_VERSION_1,
> +    VIRTIO_NET_F_MTU,
>      VHOST_INVALID_FEATURE_BIT
>  };
>  
> @@ -74,6 +75,7 @@ static const int user_feature_bits[] = {
>      VIRTIO_NET_F_HOST_ECN,
>      VIRTIO_NET_F_HOST_UFO,
>      VIRTIO_NET_F_MRG_RXBUF,
> +    VIRTIO_NET_F_MTU,
>  
>      /* This bit implies RARP isn't sent by QEMU out of band */
>      VIRTIO_NET_F_GUEST_ANNOUNCE,
> @@ -435,6 +437,22 @@ int vhost_set_vring_enable(NetClientState *nc, int enable)
>      return 0;
>  }
>  
> +int vhost_net_set_mtu(struct vhost_net *net, uint16_t mtu)
> +{
> +    const VhostOps *vhost_ops = net->dev.vhost_ops;
> +    int ret;
> +
> +    if (!vhost_ops->vhost_net_set_mtu) {
> +        return -ENOSYS;
> +    }
> +
> +    ret = vhost_ops->vhost_net_set_mtu(&net->dev, mtu);
> +    if (ret < 0) {
> +        return -errno;
> +    }
> +    return 0;
> +}
> +
>  #else
>  uint64_t vhost_net_get_max_queues(VHostNetState *net)
>  {
> @@ -501,4 +519,8 @@ int vhost_set_vring_enable(NetClientState *nc, int enable)
>  {
>      return 0;
>  }
> +
> +int vhost_net_set_mtu(struct vhost_net *net, uint16_t mtu)
> +{
> +}
>  #endif

I think this should return something - I don't know what value will come
through if it doesn't :).

> diff --git a/include/net/vhost_net.h b/include/net/vhost_net.h
> index 5a08eff..afc1499 100644
> --- a/include/net/vhost_net.h
> +++ b/include/net/vhost_net.h
> @@ -35,4 +35,6 @@ int vhost_set_vring_enable(NetClientState * nc, int enable);
>  
>  uint64_t vhost_net_get_acked_features(VHostNetState *net);
>  
> +int vhost_net_set_mtu(struct vhost_net *net, uint16_t mtu);
> +
>  #endif