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Message-ID: <CACGkMEs22078F7rSLEz6eQabkZZ=kujSONUNMThZz5Gp=YiidQ@mail.gmail.com> Date: Tue, 17 Oct 2023 10:38:00 +0800 From: Jason Wang <jasowang@...hat.com> To: Alexei Starovoitov <alexei.starovoitov@...il.com> Cc: Akihiko Odaki <akihiko.odaki@...nix.com>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...gle.com>, Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, Jonathan Corbet <corbet@....net>, Willem de Bruijn <willemdebruijn.kernel@...il.com>, "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, "Michael S. Tsirkin" <mst@...hat.com>, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>, bpf <bpf@...r.kernel.org>, "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, Network Development <netdev@...r.kernel.org>, kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org, "open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@...r.kernel.org>, Yuri Benditovich <yuri.benditovich@...nix.com>, Andrew Melnychenko <andrew@...nix.com> Subject: Re: [RFC PATCH v2 1/7] bpf: Introduce BPF_PROG_TYPE_VNET_HASH On Tue, Oct 17, 2023 at 7:53 AM Alexei Starovoitov <alexei.starovoitov@...il.com> wrote: > > On Sun, Oct 15, 2023 at 10:10 AM Akihiko Odaki <akihiko.odaki@...nix.com> wrote: > > > > On 2023/10/16 1:07, Alexei Starovoitov wrote: > > > On Sun, Oct 15, 2023 at 7:17 AM Akihiko Odaki <akihiko.odaki@...nix.com> 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 >
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