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* [xdp-hints] [RFC bpf-next 0/5] xdp: hints via kfuncs
@ 2022-10-27 20:00 Stanislav Fomichev
  2022-10-27 20:00 ` [xdp-hints] [RFC bpf-next 1/5] bpf: Support inlined/unrolled kfuncs for xdp metadata Stanislav Fomichev
                   ` (5 more replies)
  0 siblings, 6 replies; 50+ messages in thread
From: Stanislav Fomichev @ 2022-10-27 20:00 UTC (permalink / raw)
  To: bpf
  Cc: ast, daniel, andrii, martin.lau, song, yhs, john.fastabend,
	kpsingh, sdf, haoluo, jolsa, Jakub Kicinski, Willem de Bruijn,
	Jesper Dangaard Brouer, Anatoly Burakov, Alexander Lobakin,
	Magnus Karlsson, Maryam Tahhan, xdp-hints, netdev

This is an RFC for the alternative approach suggested by Martin and
Jakub. I've tried to CC most of the people from the original discussion,
feel free to add more if you think I've missed somebody.

Summary:
- add new BPF_F_XDP_HAS_METADATA program flag and abuse
  attr->prog_ifindex to pass target device ifindex at load time
- at load time, find appropriate ndo_unroll_kfunc and call
  it to unroll/inline kfuncs; kfuncs have the default "safe"
  implementation if unrolling is not supported by a particular
  device
- rewrite xskxceiver test to use C bpf program and extend
  it to export rx_timestamp (plus add rx timestamp to veth driver)

I've intentionally kept it small and hacky to see whether the approach is
workable or not.

Pros:
- we avoid BTF complexity; the BPF programs themselves are now responsible
  for agreeing on the metadata layout with the AF_XDP consumer
- the metadata is free if not used
- the metadata should, in theory, be cheap if used; kfuncs should be
  unrolled to the same code as if the metadata was pre-populated and
  passed with a BTF id
- it's not all or nothing; users can use small subset of metadata which
  is more efficient than the BTF id approach where all metadata has to be
  exposed for every frame (and selectively consumed by the users)

Cons:
- forwarding has to be handled explicitly; the BPF programs have to
  agree on the metadata layout (IOW, the forwarding program
  has to be aware of the final AF_XDP consumer metadata layout)
- TX picture is not clear; but it's not clear with BTF ids as well;
  I think we've agreed that just reusing whatever we have at RX
  won't fly at TX; seems like TX XDP program might be the answer
  here? (with a set of another tx kfuncs to "expose" bpf/af_xdp metatata
  back into the kernel)

Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Willem de Bruijn <willemb@google.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Anatoly Burakov <anatoly.burakov@intel.com>
Cc: Alexander Lobakin <alexandr.lobakin@intel.com>
Cc: Magnus Karlsson <magnus.karlsson@gmail.com>
Cc: Maryam Tahhan <mtahhan@redhat.com>
Cc: xdp-hints@xdp-project.net
Cc: netdev@vger.kernel.org

Stanislav Fomichev (5):
  bpf: Support inlined/unrolled kfuncs for xdp metadata
  veth: Support rx timestamp metadata for xdp
  libbpf: Pass prog_ifindex via bpf_object_open_opts
  selftests/bpf: Convert xskxceiver to use custom program
  selftests/bpf: Test rx_timestamp metadata in xskxceiver

 drivers/net/veth.c                            |  31 +++++
 include/linux/bpf.h                           |   1 +
 include/linux/btf.h                           |   1 +
 include/linux/btf_ids.h                       |   4 +
 include/linux/netdevice.h                     |   3 +
 include/net/xdp.h                             |  22 ++++
 include/uapi/linux/bpf.h                      |   5 +
 kernel/bpf/syscall.c                          |  28 ++++-
 kernel/bpf/verifier.c                         |  60 +++++++++
 net/core/dev.c                                |   7 ++
 net/core/xdp.c                                |  28 +++++
 tools/include/uapi/linux/bpf.h                |   5 +
 tools/lib/bpf/libbpf.c                        |   1 +
 tools/lib/bpf/libbpf.h                        |   6 +-
 tools/testing/selftests/bpf/Makefile          |   1 +
 .../testing/selftests/bpf/progs/xskxceiver.c  |  43 +++++++
 tools/testing/selftests/bpf/xskxceiver.c      | 119 +++++++++++++++---
 tools/testing/selftests/bpf/xskxceiver.h      |   5 +-
 18 files changed, 348 insertions(+), 22 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/progs/xskxceiver.c

-- 
2.38.1.273.g43a17bfeac-goog


^ permalink raw reply	[flat|nested] 50+ messages in thread

end of thread, other threads:[~2022-11-03 15:25 UTC | newest]

Thread overview: 50+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-10-27 20:00 [xdp-hints] [RFC bpf-next 0/5] xdp: hints via kfuncs Stanislav Fomichev
2022-10-27 20:00 ` [xdp-hints] [RFC bpf-next 1/5] bpf: Support inlined/unrolled kfuncs for xdp metadata Stanislav Fomichev
2022-10-27 20:00 ` [xdp-hints] [RFC bpf-next 2/5] veth: Support rx timestamp metadata for xdp Stanislav Fomichev
2022-10-28  8:40   ` [xdp-hints] " Jesper Dangaard Brouer
2022-10-28 18:46     ` Stanislav Fomichev
2022-10-27 20:00 ` [xdp-hints] [RFC bpf-next 3/5] libbpf: Pass prog_ifindex via bpf_object_open_opts Stanislav Fomichev
2022-10-27 20:05   ` [xdp-hints] " Andrii Nakryiko
2022-10-27 20:10     ` Stanislav Fomichev
2022-10-27 20:00 ` [xdp-hints] [RFC bpf-next 4/5] selftests/bpf: Convert xskxceiver to use custom program Stanislav Fomichev
2022-10-27 20:00 ` [xdp-hints] [RFC bpf-next 5/5] selftests/bpf: Test rx_timestamp metadata in xskxceiver Stanislav Fomichev
2022-10-28  6:22   ` [xdp-hints] " Martin KaFai Lau
2022-10-28 10:37     ` Jesper Dangaard Brouer
2022-10-28 18:46       ` Stanislav Fomichev
2022-10-31 14:20         ` Alexander Lobakin
2022-10-31 14:29           ` Alexander Lobakin
2022-10-31 17:00           ` Stanislav Fomichev
2022-11-01 13:18             ` Jesper Dangaard Brouer
2022-11-01 20:12               ` Stanislav Fomichev
2022-11-01 22:23               ` Toke Høiland-Jørgensen
2022-10-28 15:58 ` [xdp-hints] Re: [RFC bpf-next 0/5] xdp: hints via kfuncs John Fastabend
2022-10-28 18:04   ` Jakub Kicinski
2022-10-28 18:46     ` Stanislav Fomichev
2022-10-28 23:16       ` John Fastabend
2022-10-29  1:14         ` Jakub Kicinski
2022-10-31 14:10           ` Bezdeka, Florian
2022-10-31 15:28             ` Toke Høiland-Jørgensen
2022-10-31 17:00               ` Stanislav Fomichev
2022-10-31 22:57                 ` Martin KaFai Lau
2022-11-01  1:59                   ` Stanislav Fomichev
2022-11-01 12:52                     ` Toke Høiland-Jørgensen
2022-11-01 13:43                       ` David Ahern
2022-11-01 14:20                         ` Toke Høiland-Jørgensen
2022-11-01 17:05                     ` Martin KaFai Lau
2022-11-01 20:12                       ` Stanislav Fomichev
2022-11-02 14:06                       ` Jesper Dangaard Brouer
2022-11-02 22:01                         ` Toke Høiland-Jørgensen
2022-11-02 23:10                           ` Stanislav Fomichev
2022-11-03  0:09                             ` Toke Høiland-Jørgensen
2022-11-03 12:01                               ` Jesper Dangaard Brouer
2022-11-03 12:48                                 ` Toke Høiland-Jørgensen
2022-11-03 15:25                                   ` Jesper Dangaard Brouer
2022-10-31 19:36               ` Yonghong Song
2022-10-31 22:09                 ` Stanislav Fomichev
2022-10-31 22:38                   ` Yonghong Song
2022-10-31 22:55                     ` Stanislav Fomichev
2022-11-01 14:23                       ` Jesper Dangaard Brouer
2022-11-01 17:31                   ` Martin KaFai Lau
2022-11-01 20:12                     ` Stanislav Fomichev
2022-11-01 21:17                       ` Martin KaFai Lau
2022-10-31 17:01           ` John Fastabend

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