On Sun, Oct 8, 2023 at 7:21 AM 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 makes little sense to > allow to implement different hashing algorithms with eBPF since the hash > value reported by virtio-net is strictly defined by the specification. But using the existing BPF steering may have the benefit of requiring a lot less new code. There is ample precedence for BPF programs that work this way. The flow dissector comes to mind.
