Re: [PATCH v6 net-next 0/9] virtio: introduce GSO over UDP tunnel

[Paolo Abeni <pabeni@redhat.com>]

On 6/24/25 4:09 PM, Paolo Abeni wrote:
> Some virtualized deployments use UDP tunnel pervasively and are impacted
> negatively by the lack of GSO support for such kind of traffic in the
> virtual NIC driver.
> 
> The virtio_net specification recently introduced support for GS over
> UDP tunnel, this series updates the virtio implementation to support
> such a feature.
> 
> Currently the kernel virtio support limits the feature space to 64,
> while the virtio specification allows for a larger number of features.
> Specifically the GSO-over-UDP-tunnel-related virtio features use bits
> 65-69.
> 
> The first four patches in this series rework the virtio and vhost
> feature support to cope with up to 128 bits. The limit is set by
> a define and could be easily raised in future, as needed.
> 
> This implementation choice is aimed at keeping the code churn as
> limited as possible. For the same reason, only the virtio_net driver is
> reworked to leverage the extended feature space; all other
> virtio/vhost drivers are unaffected, but could be upgraded to support
> the extended features space in a later time.
> 
> The last four patches bring in the actual GSO over UDP tunnel support.
> As per specification, some additional fields are introduced into the
> virtio net header to support the new offload. The presence of such
> fields depends on the negotiated features.
> 
> New helpers are introduced to convert the UDP-tunneled skb metadata to
> an extended virtio net header and vice versa. Such helpers are used by
> the tun and virtio_net driver to cope with the newly supported offloads.
> 
> Tested with basic stream transfer with all the possible permutations of
> host kernel/qemu/guest kernel with/without GSO over UDP tunnel support.
> 
> This is also are available in the Git repository at:
> 
> git@github.com:pabeni/linux-devel.git virtio_udp_tunnel_24_06_2025
> 
> Ideally both the net-next tree and the vhost tree could pull from the
> above.

As Michael prefers to hide the warning in patch 4/9 and this series in
the current form has now conflicts with the current net-next tree, I
just shared a v7, with a more detailed merge plan in the cover letter.

Thanks,

Paolo