From: KaFai Wan <kafai.wan@linux.dev>
To: Tiezhu Yang <yangtiezhu@loongson.cn>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Eduard Zingerman <eddyz87@gmail.com>,
Kumar Kartikeya Dwivedi <memxor@gmail.com>,
Martin KaFai Lau <martin.lau@linux.dev>,
Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
Jiri Olsa <jolsa@kernel.org>,
Emil Tsalapatis <emil@etsalapatis.com>
Cc: bpf@vger.kernel.org, loongarch@lists.linux.dev,
"Leon Hwang" <leon.hwang@linux.dev>,
"Puranjay Mohan" <puranjay@kernel.org>,
"Björn Töpel" <bjorn@kernel.org>
Subject: Re: [PATCH bpf-next v8 1/2] bpf: Introduce jit_required flag and remove bpf_prog_has_kfunc_call()
Date: Mon, 06 Jul 2026 19:39:12 +0800 [thread overview]
Message-ID: <dd75b7afbe2b5507ac818df14dd44aff32db1e18.camel@linux.dev> (raw)
In-Reply-To: <20260706040006.10331-2-yangtiezhu@loongson.cn>
On Mon, 2026-07-06 at 12:00 +0800, Tiezhu Yang wrote:
> Introduce a 'jit_required' bitfield flag in struct bpf_prog. This bit
> tracks whether a BPF program strictly requires the JIT compiler to run,
> preventing dangerous runtime fallback to the interpreter for features
> not implemented there.
>
> Set the flag 'jit_required' to 1 at the entry of bpf_add_kfunc_call()
> right after the kfunc_tab allocation succeeds. This cleanly marks the
> lifecycle of any program attempting to utilize kernel functions.
>
> Furthermore, completely remove the bpf_prog_has_kfunc_call() helper,
> as its logic is now unified under the 'jit_required' flag.
>
> In bpf_fixup_call_args(), check with 'prog->jit_required' rather than
> bpf_prog_has_kfunc_call(), and generalize the error message to generic
> BPF JIT availability.
>
> In __bpf_prog_select_runtime(), check with 'fp->jit_required' rather
> than bpf_prog_has_kfunc_call() to unify the logic.
>
If you have a new version, I think we could simplify the description of the code details a bit.
The code is fine by me, others might have comments.
> Suggested-by: Alexei Starovoitov <ast@kernel.org>
> Suggested-by: KaFai Wan <kafai.wan@linux.dev>
> Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
> ---
--
Thanks,
KaFai
next prev parent reply other threads:[~2026-07-06 11:39 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-06 4:00 [PATCH bpf-next v8 0/2] Introduce jit_required to prevent a kernel panic Tiezhu Yang
2026-07-06 4:00 ` [PATCH bpf-next v8 1/2] bpf: Introduce jit_required flag and remove bpf_prog_has_kfunc_call() Tiezhu Yang
2026-07-06 11:39 ` KaFai Wan [this message]
2026-07-07 1:43 ` Tiezhu Yang
2026-07-06 4:00 ` [PATCH bpf-next v8 2/2] bpf: Reject programs with inlined helpers if JIT is not available Tiezhu Yang
2026-07-06 21:41 ` Eduard Zingerman
2026-07-07 1:37 ` Tiezhu Yang
2026-07-07 2:03 ` Leon Hwang
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