On 06/24, Jakub Kicinski wrote: > On Fri, 23 Jun 2023 19:52:03 -0700 Alexei Starovoitov wrote: > > That's pretty much what I'm suggesting. > > Add two driver specific __weak nop hook points where necessary > > with few driver specific kfuncs. > > Don't build generic infra when it's too early to generalize. > > > > It would mean that bpf progs will be driver specific, > > but when something novel like this is being proposed it's better > > to start with minimal code change to core kernel (ideally none) > > and when common things are found then generalize. > > > > Sounds like Stanislav use case is timestamps in TX > > while Donald's are checksums on RX, TX. These use cases are too different. > > To make HW TX checksum compute checksum driven by AF_XDP > > a lot more needs to be done than what Stan is proposing for timestamps. > > I'd think HW TX csum is actually simpler than dealing with time, > will you change your mind if Stan posts Tx csum within a few days? :) > > The set of offloads is barely changing, the lack of clarity > on what is needed seems overstated. IMHO AF_XDP is getting no use > today, because everything remotely complex was stripped out of > the implementation to get it merged. Aren't we hand waving the > complexity away simply because we don't want to deal with it? > > These are the features today's devices support (rx/tx is a mirror): > - L4 csum > - segmentation > - time reporting > > Some may also support: > - forwarding md tagging > - Tx launch time > - no fcs > Legacy / irrelevant: > - VLAN insertion Right, the goal of the series is to lay out the foundation to support AF_XDP offloads. I'm starting with tx timestamp because that's more pressing. But, as I mentioned in another thread, we do have other users that want to adopt AF_XDP, but due to missing tx offloads, they aren't able to. IMHO, with pre-tx/post-tx hooks, it's pretty easy to go from TX timestamp to TX checksum offload, we don't need a lot: - define another generic kfunc bpf_request_tx_csum(from, to) - drivers implement it - af_xdp users call this kfunc from devtx hook We seem to be arguing over start-with-my-specific-narrow-use-case vs start-with-generic implementation, so maybe time for the office hours? I can try to present some cohesive plan of how we start with the framework plus tx-timestamp and expand with tx-checksum/etc. There is a lot of commonality in these offloads, so I'm probably not communicating it properly..
