Re: [PATCH RFC v3 12/13] net: implement tunnel probing

[Jason Wang <jasowang@redhat.com>]

On Tue, Jul 22, 2025 at 3:33 PM Paolo Abeni <pabeni@redhat.com> wrote:
>
> On 7/22/25 5:50 AM, Jason Wang wrote:
> > On Fri, Jul 18, 2025 at 4:54 PM Paolo Abeni <pabeni@redhat.com> wrote:
> >> Tap devices support GSO over UDP tunnel offload. Probe for such
> >> feature in a similar manner to other offloads.
> >>
> >> GSO over UDP tunnel needs to be enabled in addition to a "plain"
> >> offload (TSO or USO).
> >>
> >> No need to check separately for the outer header checksum offload:
> >> the kernel is going to support both of them or none.
> >>
> >> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> >> ---
> >> v2 -> v3:
> >>   - use bool type for tap_probe_has_tunnel()
> >>   - rebased on top of 2deec9ab7d ("virtio-net: Move
> >>         virtio_net_get_features() down")
> >>   - _array -> _ex
> >>
> >> v1 -> v2:
> >>   - peer_has_tunnel return a bool
> >>   - move TUN_F definition in net/tun-linux.h
> >> ---
> >>  hw/net/virtio-net.c | 37 +++++++++++++++++++++++++++++++++++++
> >>  include/net/net.h   |  3 +++
> >>  net/net.c           |  9 +++++++++
> >>  net/tap-bsd.c       |  5 +++++
> >>  net/tap-linux.c     | 11 +++++++++++
> >>  net/tap-linux.h     |  9 +++++++++
> >>  net/tap-solaris.c   |  5 +++++
> >>  net/tap-stub.c      |  5 +++++
> >>  net/tap.c           | 11 +++++++++++
> >>  net/tap_int.h       |  1 +
> >>  10 files changed, 96 insertions(+)
> >>
> >> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> >> index 53413ec4d5..70c85f7f77 100644
> >> --- a/hw/net/virtio-net.c
> >> +++ b/hw/net/virtio-net.c
> >> @@ -649,6 +649,15 @@ static int peer_has_uso(VirtIONet *n)
> >>      return qemu_has_uso(qemu_get_queue(n->nic)->peer);
> >>  }
> >>
> >> +static bool peer_has_tunnel(VirtIONet *n)
> >
> > Nit: it looks better to use peer_has_udp_gso_tunnel().
> >
> >> +{
> >> +    if (!peer_has_vnet_hdr(n)) {
> >> +        return false;
> >> +    }
> >> +
> >> +    return qemu_has_tunnel(qemu_get_queue(n->nic)->peer);
> >> +}
> >> +
> >>  static void virtio_net_set_mrg_rx_bufs(VirtIONet *n, int mergeable_rx_bufs,
> >>                                         int version_1, int hash_report)
> >>  {
> >> @@ -3070,6 +3079,13 @@ static void virtio_net_get_features(VirtIODevice *vdev, uint64_t *features,
> >>          virtio_clear_feature_ex(features, VIRTIO_NET_F_GUEST_USO4);
> >>          virtio_clear_feature_ex(features, VIRTIO_NET_F_GUEST_USO6);
> >>
> >> +        virtio_clear_feature_ex(features, VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO);
> >> +        virtio_clear_feature_ex(features, VIRTIO_NET_F_HOST_UDP_TUNNEL_GSO);
> >> +        virtio_clear_feature_ex(features,
> >> +                                VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO_CSUM);
> >> +        virtio_clear_feature_ex(features,
> >> +                                VIRTIO_NET_F_HOST_UDP_TUNNEL_GSO_CSUM);
> >> +
> >>          virtio_clear_feature_ex(features, VIRTIO_NET_F_HASH_REPORT);
> >>      }
> >>
> >> @@ -3083,6 +3099,15 @@ static void virtio_net_get_features(VirtIODevice *vdev, uint64_t *features,
> >>          virtio_clear_feature_ex(features, VIRTIO_NET_F_GUEST_USO6);
> >>      }
> >>
> >> +    if (!peer_has_tunnel(n)) {
> >> +        virtio_clear_feature_ex(features, VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO);
> >> +        virtio_clear_feature_ex(features, VIRTIO_NET_F_HOST_UDP_TUNNEL_GSO);
> >> +        virtio_clear_feature_ex(features,
> >> +                                VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO_CSUM);
> >> +        virtio_clear_feature_ex(features,
> >> +                                VIRTIO_NET_F_HOST_UDP_TUNNEL_GSO_CSUM);
> >> +    }
> >> +
> >>      if (!get_vhost_net(nc->peer)) {
> >>          if (!use_own_hash) {
> >>              virtio_clear_feature_ex(features, VIRTIO_NET_F_HASH_REPORT);
> >> @@ -4137,6 +4162,10 @@ static const VMStateDescription vmstate_virtio_net = {
> >>      .dev_unplug_pending = dev_unplug_pending,
> >>  };
> >>
> >> +#define DEFINE_PROP_FEATURE(_name, _state, _field, _bit, _defval)   \
> >> +    DEFINE_PROP_BIT64(_name, _state, _field[VIRTIO_DWORD(_bit)],    \
> >> +                      (_bit) % 64, _defval)
> >> +
> >>  static const Property virtio_net_properties[] = {
> >>      DEFINE_PROP_BIT64("csum", VirtIONet, host_features,
> >>                      VIRTIO_NET_F_CSUM, true),
> >> @@ -4245,6 +4274,14 @@ static const Property virtio_net_properties[] = {
> >>                                    rss_data.specified_hash_types,
> >>                                    VIRTIO_NET_HASH_REPORT_UDPv6_EX - 1,
> >>                                    ON_OFF_AUTO_AUTO),
> >> +    DEFINE_PROP_FEATURE("host_tunnel", VirtIONet, host_features_ex,
> >> +                        VIRTIO_NET_F_HOST_UDP_TUNNEL_GSO, true),
> >> +    DEFINE_PROP_FEATURE("host_tunnel_csum", VirtIONet, host_features_ex,
> >> +                        VIRTIO_NET_F_HOST_UDP_TUNNEL_GSO_CSUM, true),
> >> +    DEFINE_PROP_FEATURE("guest_tunnel", VirtIONet, host_features_ex,
> >> +                        VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO, true),
> >> +    DEFINE_PROP_FEATURE("guest_tunnel_csum", VirtIONet, host_features_ex,
> >> +                        VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO_CSUM, true),
> >>  };
> >
> > Need compatibility work like:
> >
> > d83f46d189 ("virtio-pci: compat page aligned ATS")
>
> If I read correctly the only missing pieces are the hw_compat_10_1
> entries, am I correct?
>
> If so, as mentioned here:
>
> https://lists.gnu.org/archive/html/qemu-devel/2025-07/msg05032.html

Exactly.

>
> I'll add the needed entries after that the hw_compat_10_1 will be created.
>
> Thanks,
>
> Paolo

Thanks

>