On Tue, Oct 17, 2023 at 7:53 AM Alexei Starovoitov
<alexei.starovoitov@xxxxxxxxx> wrote:
>
> On Sun, Oct 15, 2023 at 10:10 AM Akihiko Odaki <akihiko.odaki@xxxxxxxxxx> wrote:
> >
> > On 2023/10/16 1:07, Alexei Starovoitov wrote:
> > > On Sun, Oct 15, 2023 at 7:17 AM Akihiko Odaki <akihiko.odaki@xxxxxxxxxx> wrote:
> > >>
> > >> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > >> index 0448700890f7..298634556fab 100644
> > >> --- a/include/uapi/linux/bpf.h
> > >> +++ b/include/uapi/linux/bpf.h
> > >> @@ -988,6 +988,7 @@ enum bpf_prog_type {
> > >> BPF_PROG_TYPE_SK_LOOKUP,
> > >> BPF_PROG_TYPE_SYSCALL, /* a program that can execute syscalls */
> > >> BPF_PROG_TYPE_NETFILTER,
> > >> + BPF_PROG_TYPE_VNET_HASH,
> > >
> > > Sorry, we do not add new stable program types anymore.
> > >
> > >> @@ -6111,6 +6112,10 @@ struct __sk_buff {
> > >> __u8 tstamp_type;
> > >> __u32 :24; /* Padding, future use. */
> > >> __u64 hwtstamp;
> > >> +
> > >> + __u32 vnet_hash_value;
> > >> + __u16 vnet_hash_report;
> > >> + __u16 vnet_rss_queue;
> > >> };
> > >
> > > we also do not add anything to uapi __sk_buff.
> > >
> > >> +const struct bpf_verifier_ops vnet_hash_verifier_ops = {
> > >> + .get_func_proto = sk_filter_func_proto,
> > >> + .is_valid_access = sk_filter_is_valid_access,
> > >> + .convert_ctx_access = bpf_convert_ctx_access,
> > >> + .gen_ld_abs = bpf_gen_ld_abs,
> > >> +};
> > >
> > > and we don't do ctx rewrites like this either.
> > >
> > > Please see how hid-bpf and cgroup rstat are hooking up bpf
> > > in _unstable_ way.
> >
> > Can you describe what "stable" and "unstable" mean here? I'm new to BPF
> > and I'm worried if it may mean the interface stability.
> >
> > Let me describe the context. QEMU bundles an eBPF program that is used
> > for the "eBPF steering program" feature of tun. Now I'm proposing to
> > extend the feature to allow to return some values to the userspace and
> > vhost_net. As such, the extension needs to be done in a way that ensures
> > interface stability.
>
> bpf is not an option then.
> we do not add stable bpf program types or hooks any more.
Does this mean eBPF could not be used for any new use cases other than
the existing ones?
> If a kernel subsystem wants to use bpf it needs to accept the fact
> that such bpf extensibility will be unstable and subsystem maintainers
> can decide to remove such bpf support in the future.
I don't see how it is different from the existing ones.
Thanks
>
