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

[Maxime Coquelin]

On 12/06/2016 07:31 PM, Aaron Conole wrote:
> Maxime Coquelin <address@hidden> 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 <address@hidden>
> > Cc: Aaron Conole <address@hidden>
> > Signed-off-by: Maxime Coquelin <address@hidden>
> > ---
> >  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 :).

Good catch, of course something should be returned...

Thanks!
Maxime