Re: [PATCH net-next v11 00/10] tun: Introduce virtio-net hashing feature

[Lei Yang]

QE tested this series of patches v11 under linux-next repo with
virtio-net regression tests, everything works fine.

Tested-by: Lei Yang <leiyang@xxxxxxxxxx>

On Tue, Mar 18, 2025 at 8:29 AM Jason Wang <jasowang@xxxxxxxxxx> wrote:
>
> On Mon, Mar 17, 2025 at 6:58 PM Akihiko Odaki <akihiko.odaki@xxxxxxxxxx> wrote:
> >
> > virtio-net have two usage of hashes: one is RSS and another is hash
> > reporting. Conventionally the hash calculation was done by the VMM.
> > However, computing the hash after the queue was chosen defeats the
> > purpose of RSS.
> >
> > Another approach is to use eBPF steering program. This approach has
> > another downside: it cannot report the calculated hash due to the
> > restrictive nature of eBPF.
> >
> > Introduce the code to compute hashes to the kernel in order to overcome
> > thse challenges.
> >
> > An alternative solution is to extend the eBPF steering program so that it
> > will be able to report to the userspace, but it is based on context
> > rewrites, which is in feature freeze. We can adopt kfuncs, but they will
> > not be UAPIs. We opt to ioctl to align with other relevant UAPIs (KVM
> > and vhost_net).
> >
> > The patches for QEMU to use this new feature was submitted as RFC and
> > is available at:
> > https://patchew.org/QEMU/20250313-hash-v4-0-c75c494b495e@xxxxxxxxxx/
> >
> > This work was presented at LPC 2024:
> > https://lpc.events/event/18/contributions/1963/
> >
> > V1 -> V2:
> >   Changed to introduce a new BPF program type.
> >
> > Signed-off-by: Akihiko Odaki <akihiko.odaki@xxxxxxxxxx>
> > ---
> > Changes in v11:
> > - Added the missing code to free vnet_hash in patch
> >   "tap: Introduce virtio-net hash feature".
> > - Link to v10: https://lore.kernel.org/r/20250313-rss-v10-0-3185d73a9af0@xxxxxxxxxx
> >
>
> We only have 2 or 3 points that need to be sorted out. Let's hold on
> to the iteration until we had an agreement.
>
> Thanks
>