From: Toke Høiland-Jørgensen <toke@xxxxxxxxxx> Date: Sun, 23 May 2021 13:54:47 +0200 > Saeed Mahameed <saeed@xxxxxxxxxx> writes: > > > On Fri, 2021-05-21 at 15:31 +0200, Jesper Dangaard Brouer wrote: > >> On Fri, 21 May 2021 10:53:40 +0000 > >> "Lobakin, Alexandr" <alexandr.lobakin@xxxxxxxxx> wrote: > >> > >> > I've opened two discussions at https://github.com/alobakin/linux, > >> > feel free to join them and/or create new ones to share your thoughts > >> > and concerns. > >> > >> Thanks Alexandr for keeping the thread/subject alive. > >> > >> I guess this is a new GitHub features "Discussions". I've never used > >> that in a project before, lets see how this goes. The usual approach > >> is discussions over email on netdev (Cc. netdev@xxxxxxxxxxxxxxx). > > > > I agree we need full visibility and transparency, i actually recommend: > > bpf@xxxxxxxxxxxxxxx > > +1, please keep this on the list :) Sure, let's keep it the classic way. I removed the netdev ML from the CCs and added bpf there. Regarding the comments from GitHub discussions: alobakin: > Since 5.11, it's now possible to obtain a BTF not only for vmlinux, > but also for modules. > This will eliminate a need for manually composing and registering a > BTF inside the driver code, which is 100+ locs for ice for example. > > That's obviously not the most straightforward and trivial way, but > could help a lot. saeedtx: > the point of registering BTF directly from the driver is to allow > "Flex metadata" meaning that meta data format can be constructed on > the fly according to user demand. > BTF for modules is constructed only at compilation time and > registered only on module load. so there is no way to implement flex > metadata with vmlinux BTF. we still need a dynamic registration API > for current and future HW where the HW will provide the BTF > dynamically. > > I am sure we can find mutliple ways to reduce the 100+ LOC, but the > goal is to have the dynamic btf_register/unregister API We initially planned to register just one (or several) predefined BTF(s) per module/netdevice that would provide a full list of supported fields. The flexibility of metadata then is in that BPF core calls for netdevice's ndo_bpf() on BPF program setup and provides a metadata layout requested by that BPF prog to the driver, so it could configure its hotpath (current NICs) or a hardware (future NICs) to build metadata accordingly. Driver can declare several BTFs (e.g. a "generic" one with things like hashes and csums one and a custom one) and it would work either through dynamic registering or through /sys approach. This is all discussable anyways, we're happy to hear different opinions and thoughts to collectively choose the optimal way. > -Toke Thanks, Al
