Ryan Wilson <ryantimwilson@xxxxxxxxx> writes: > On Fri, Nov 15, 2024 at 3:07 AM Toke Høiland-Jørgensen <toke@xxxxxxxxxx> wrote: >> >> Hi Ryan >> >> I'll take a more detailed look at your patch later, but wanted to add >> a few smallish comment now, see below: >> >> >> Ryan Wilson <ryantimwilson@xxxxxxxxx> writes: >> > On Thu, Nov 14, 2024 at 4:52 PM Alexei Starovoitov >> > <alexei.starovoitov@xxxxxxxxx> wrote: >> >> >> >> On Thu, Nov 14, 2024 at 9:07 AM Ryan Wilson <ryantimwilson@xxxxxxxxx> wrote: >> >> > >> >> > Currently, network devices only support a single XDP program. However, >> >> > there are use cases for multiple XDP programs per device. For example, >> >> > at Meta, we have XDP programs for firewalls, DDOS and logging that must >> >> > all run in a specific order. To work around the lack of multi-program >> >> > support, a single daemon loads all programs and uses bpf_tail_call() >> >> > in a loop to jump to each program contained in a BPF map. >> >> >> >> The support for multiple XDP progs per netdev is long overdue. >> >> Thank you for working on this! >> >> +1 on this! >> >> >> [...] >> >> > Note for real drivers, we do not hit this code. This is how it works >> > for real drivers: >> > - When installing a BPF program on a driver, we call the driver's >> > ndo_bpf() callback function with command = XDP_QUERY_MPROG_SUPPORT. If >> > this returns 0, then mprog is supported. Otherwise, mprog is not >> > supported. >> >> We already have feature flags for XDP, so why not just make mprog >> support a feature flag instead of the query thing? It probably should be >> anyway, so it can also be reported to userspace. > > Oh wow can't believe I missed the feature flag API. Yes, I'll use this > in v2 instead. Thanks for the suggestion! Cool! You're welcome. > And if it's exposed to userspace, users no longer need to guess if > their driver supports mprog or not - although hopefully this is an > intermediary state and the mprog migration for all drivers will be > relatively quick and painless. Famous last words? ;) -Toke
