On Mon, Nov 20, 2023 at 12:05 AM Akihiko Odaki <akihiko.odaki@xxxxxxxxxx> wrote: > > On 2023/11/20 6:02, Song Liu wrote: [...] > >> In contrast, our intended use case is more like a normal application. > >> So, for example, a user may download a container and run QEMU (including > >> the BPF program) installed in the container. As such, it is nice if the > >> ABI is stable across kernel releases, but it is not guaranteed for > >> kfuncs. Such a use case is already covered with the eBPF steering > >> program so I want to maintain it if possible. > > > > TBH, I don't think stability should be a concern for kfuncs used by QEMU. > > Many core BPF APIs are now implemented as kfuncs: bpf_dynptr_*, > > bpf_rcu_*, etc. As long as there are valid use cases,these kfuncs will > > be supported. > > Documentation/bpf/kfuncs.rst still says: > > kfuncs provide a kernel <-> kernel API, and thus are not bound by any > > of the strict stability restrictions associated with kernel <-> user > > UAPIs. > > Is it possible to change the statement like as follows: > "Most kfuncs provide a kernel <-> kernel API, and thus are not bound by > any of the strict stability restrictions associated with kernel <-> user > UAPIs. kfuncs that have same stability restrictions associated with > UAPIs are exceptional, and must be carefully reviewed by subsystem (and > BPF?) maintainers as any other UAPIs are." I am afraid this is against the intention to not guarantee UAPI-level stability for kfuncs. Thanks, Song
