netdev - Re: [PATCH bpf-next 0/4] Switch from kfuncs to direct helper calls in prologue/epilogue

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Message-ID: <CAMB2axNQxpJUiz7uE+pAV8uV0fye36OyAJ4qQqO-4Pdkb61=0Q@mail.gmail.com>
Date: Thu, 22 Jan 2026 19:10:13 -0800
From: Amery Hung <ameryhung@...il.com>
To: Jakub Sitnicki <jakub@...udflare.com>
Cc: bpf@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, John Fastabend <john.fastabend@...il.com>, 
	Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, 
	Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, KP Singh <kpsingh@...nel.org>, 
	Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, 
	netdev@...r.kernel.org, kernel-team@...udflare.com
Subject: Re: [PATCH bpf-next 0/4] Switch from kfuncs to direct helper calls in prologue/epilogue

On Mon, Jan 19, 2026 at 11:53 AM Jakub Sitnicki <jakub@...udflare.com> wrote:
>
> This series enables direct helper calls using BPF_EMIT_CALL from prologue
> and epilogue code generated by verifier ops. The goal is to simplify the
> calling convention and remove kfunc support from prologue/epilogue, as
> suggested by Alexei [1].
>
> Patch 1 adds the infrastructure to mark direct helper calls as finalized
> (already resolved) so the verifier skips the imm fixup.
>
> Patch 2 converts bpf_qdisc to use BPF_EMIT_CALL instead of BPF_CALL_KFUNC
> for the init prologue and reset/destroy epilogue helpers.
>
> Patch 3 removes the now-unused kfunc support code from prologue/epilogue
> handling in the verifier.
>
> Patch 4 removes the corresponding selftests that exercised kfuncs in
> prologue/epilogue.
>

Thanks for converting bpf qdisc to using BPF_EMIT_CALL. The patchset
looks good to me.

Reviewed-by: Amery Hung <ameryhung@...il.com>

> [1] https://lore.kernel.org/bpf/CAADnVQJ=kmVAZsgkG9P2nEBTUG3E4PrDG=Yz8tfeFysH4ZBqVw@mail.gmail.com/
>
> Signed-off-by: Jakub Sitnicki <jakub@...udflare.com>
> ---
> Jakub Sitnicki (4):
>       bpf, verifier: Support direct helper calls from prologue/epilogue
>       bpf: net_sched: Use direct helper calls instead of kfuncs in pro/epilogue
>       bpf: Remove kfunc support in prologue and epilogue
>       selftests/bpf: Remove tests for prologue/epilogue with kfuncs
>
>  include/linux/bpf_verifier.h                       |  1 +
>  kernel/bpf/verifier.c                              | 47 +++++------
>  net/core/filter.c                                  |  3 +-
>  net/sched/bpf_qdisc.c                              | 76 ++++++++----------
>  .../selftests/bpf/prog_tests/pro_epilogue.c        |  2 -
>  .../selftests/bpf/progs/pro_epilogue_with_kfunc.c  | 88 ---------------------
>  .../testing/selftests/bpf/test_kmods/bpf_testmod.c | 92 ----------------------
>  7 files changed, 61 insertions(+), 248 deletions(-)
>