Re: [PATCH v5 00/13] virtio: introduce support for GSO over UDP tunnel

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Sep 01, 2025 at 08:44:46AM +0200, Paolo Abeni wrote:
> On 9/1/25 4:47 AM, Jason Wang wrote:
> > On Thu, Aug 28, 2025 at 9:47 AM Akihiko Odaki
> > <odaki@rsg.ci.i.u-tokyo.ac.jp> wrote:
> >>
> >> On 2025/08/13 19:28, 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 GSO over
> >>> UDP tunnel, and the kernel side of the implementation has been merged
> >>> into the net-next tree; this series updates the virtio implementation to
> >>> support such a feature.
> >>>
> >>> Currently the qemu virtio support limits the feature space to 64 bits,
> >>> 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 larger part of this series (patches 4-12) actually deals with
> >>> extending the features space.
> >>>
> >>> The extended features are carried by fixed size uint64_t arrays,
> >>> bringing the current maximum features number to 128.
> >>>
> >>> The patches use some syntactic sugar to try to minimize the otherwise
> >>> very large code churn. Specifically the extended features are boundled
> >>> in an union with 'legacy' features definition, allowing no changes in
> >>> the virtio devices not needing the extended features set.
> >>>
> >>> The actual offload implementation is in patches 13 and 14 and boils down
> >>> to propagating the new offload to the tun devices and the vhost backend.
> >>>
> >>> Patch 1 is a small pre-req refactor that ideally could enter the
> >>> tree separately; it's presented here in the same series to help
> >>> reviewers more easily getting the full picture, patch 2 updates to
> >>> linux headers update script to deal with annotations recently introduce
> >>> in the kernel and patch 3 is a needed linux headers update.
> >>>
> >>> Tested with basic stream transfer with all the possible permutations of
> >>> host kernel/qemu/guest kernel with/without GSO over UDP tunnel support,
> >>> vs snapshots creation and restore and vs migration.
> >>>
> >>> The new features are disabled by default to avoid compatibilty issues.
> >>> They could be enabled after that hw_compat_10_1 will be added, together
> >>> with the related compatiblity entries.
> >>>
> >>> Based-on: 9d71108d7de139dd4f4e6efe6837cabb32bf5616.1755078918.git.pabeni@redhat.com
> >>
> >> Now everything looks good to me. For the whole series:
> >>
> >> Reviewed-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
> >>
> >> Regards,
> >> Akihiko Odaki
> >>
> > 
> > Acked-by: Jason Wang <jasowang@redhat.com>
> 
> Thank you for the feedback. I guess this series will go through
> Micheal's tree, am I correct?
> 
> Also I suspect/fear it could need rebasing due to some other patches
> being applied meanwhile, please LMK if a repost is needed, thanks!
> 
> Paolo

Yes - I am however traveling for the KVM forum. Will work on it
when I am back.