netdev - [PATCH v2 bpf-next 0/4] bpf: Introduce minimal support for sleepable progs

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Date:   Thu, 28 May 2020 21:38:35 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     davem@...emloft.net
Cc:     daniel@...earbox.net, netdev@...r.kernel.org, bpf@...r.kernel.org,
        kernel-team@...com
Subject: [PATCH v2 bpf-next 0/4] bpf: Introduce minimal support for sleepable progs

From: Alexei Starovoitov <ast@...nel.org>

v1->v2:
- split fmod_ret fix into separate patch
- added blacklist

v1:
This patch set introduces the minimal viable support for sleepable bpf programs.
In this patch only fentry/fexit/fmod_ret and lsm progs can be sleepable.
Only array and pre-allocated hash and lru maps allowed.

Here is 'perf report' difference of sleepable vs non-sleepable:
   3.86%  bench     [k] __srcu_read_unlock
   3.22%  bench     [k] __srcu_read_lock
   0.92%  bench     [k] bpf_prog_740d4210cdcd99a3_bench_trigger_fentry_sleep
   0.50%  bench     [k] bpf_trampoline_10297
   0.26%  bench     [k] __bpf_prog_exit_sleepable
   0.21%  bench     [k] __bpf_prog_enter_sleepable
vs
   0.88%  bench     [k] bpf_prog_740d4210cdcd99a3_bench_trigger_fentry
   0.84%  bench     [k] bpf_trampoline_10297
   0.13%  bench     [k] __bpf_prog_enter
   0.12%  bench     [k] __bpf_prog_exit

Clearly sleepable vs non-sleepable program invocation overhead is high, but it
could be acceptable in certain cases until rcu_trace is available.

bpf_copy_from_user(), bpf_msleep() will be coming in the future patches.
Support for perf_event_array and bpf_perf_event_output() will follow as well.

Alexei Starovoitov (4):
  bpf: Fix use-after-free in fmod_ret check
  bpf: Introduce sleepable BPF programs
  libbpf: support sleepable progs
  selftests/bpf: basic sleepable tests

 arch/x86/net/bpf_jit_comp.c                   | 36 +++++---
 include/linux/bpf.h                           |  4 +
 include/uapi/linux/bpf.h                      |  8 ++
 kernel/bpf/arraymap.c                         |  5 ++
 kernel/bpf/hashtab.c                          | 19 +++--
 kernel/bpf/syscall.c                          | 12 ++-
 kernel/bpf/trampoline.c                       | 33 +++++++-
 kernel/bpf/verifier.c                         | 84 ++++++++++++++++---
 tools/include/uapi/linux/bpf.h                |  8 ++
 tools/lib/bpf/libbpf.c                        | 25 +++++-
 tools/testing/selftests/bpf/bench.c           |  2 +
 .../selftests/bpf/benchs/bench_trigger.c      | 17 ++++
 tools/testing/selftests/bpf/progs/lsm.c       |  9 +-
 .../selftests/bpf/progs/trigger_bench.c       |  7 ++
 14 files changed, 232 insertions(+), 37 deletions(-)

-- 
2.23.0