From: Ihor Solodrai <ihor.solodrai@linux.dev>
To: Eduard Zingerman <eddyz87@gmail.com>,
Kumar Kartikeya Dwivedi <memxor@gmail.com>,
bpf@vger.kernel.org
Cc: Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Emil Tsalapatis <emil@etsalapatis.com>,
kkd@meta.com, kernel-team@meta.com
Subject: Re: [PATCH bpf-next v1 01/14] bpf: Split arena kfunc and struct_ops JIT capabilities
Date: Wed, 26 Aug 2026 12:52:19 -0700 [thread overview]
Message-ID: <86ca92e5-fcbd-42b4-a322-219b0a8e517a@linux.dev> (raw)
In-Reply-To: <f48031ff6aa8c6f2f7e98e4111912050dc9c3fd6.camel@gmail.com>
On 2026-08-24 3:28 p.m., Eduard Zingerman wrote:
> On Sat, 2026-08-22 at 01:34 +0200, Kumar Kartikeya Dwivedi wrote:
>> Arena pointer kfunc calls and struct_ops callbacks need different JIT
>> support. The former rebases BPF arena offsets before a kfunc call, while
>> the latter converts kernel pointers when an indirect trampoline builds a
>> callback context.
>>
>> A single bpf_jit_supports_arena_args() hook forces an architecture to
>> implement both paths at once. That ties bpf_arena_alloc_pages()
>> conversion to struct_ops trampoline support and prevents the paths from
>> being enabled and reviewed independently.
>>
>> Replace it with separate kfunc and struct_ops capability hooks. Make the
>> verifier query the hook for the path it is checking, and have x86-64 and
>> arm64 advertise both capabilities to preserve their current behavior.
>>
>> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
>> ---
>
> I see no particular reason for this split.
+1
I don't think the split makes sense in general, independent of the
powerpc point.
The arch either supports the arena pointers everywhere, or the support
is incomplete, which IMO means it doesn't support them.
> Don't see any guards in the generic or powerpc related code preventing
> struct_ops programs from loading. Hence, I presume these are supported
> by the arch. Why excluding the arch, given that all changes are
> vibe-coded?
next prev parent reply other threads:[~2026-08-26 19:52 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-21 23:34 [PATCH bpf-next v1 00/14] Retire KF_ARENA_ARG kfunc flags Kumar Kartikeya Dwivedi
2026-08-21 23:34 ` [PATCH bpf-next v1 01/14] bpf: Split arena kfunc and struct_ops JIT capabilities Kumar Kartikeya Dwivedi
2026-08-22 0:46 ` bot+bpf-ci
2026-08-24 22:28 ` Eduard Zingerman
2026-08-24 22:37 ` Kumar Kartikeya Dwivedi
2026-08-26 19:52 ` Ihor Solodrai [this message]
2026-08-21 23:34 ` [PATCH bpf-next v1 02/14] bpf, riscv: Fix stack-passed arguments for indirect trampolines Kumar Kartikeya Dwivedi
2026-08-24 6:21 ` Pu Lehui
2026-08-21 23:34 ` [PATCH bpf-next v1 03/14] bpf, riscv: JIT arena kfunc argument rebasing Kumar Kartikeya Dwivedi
2026-08-24 6:36 ` Pu Lehui
2026-08-21 23:34 ` [PATCH bpf-next v1 04/14] bpf, riscv: Convert struct_ops arena arguments in the trampoline Kumar Kartikeya Dwivedi
2026-08-21 23:44 ` sashiko-bot
2026-08-24 6:38 ` Pu Lehui
2026-08-21 23:34 ` [PATCH bpf-next v1 05/14] bpf, s390: JIT arena kfunc argument rebasing Kumar Kartikeya Dwivedi
2026-08-21 23:35 ` [PATCH bpf-next v1 06/14] bpf, s390: Convert struct_ops arena arguments Kumar Kartikeya Dwivedi
2026-08-22 0:46 ` bot+bpf-ci
2026-08-21 23:35 ` [PATCH bpf-next v1 07/14] bpf, loongarch: Fix stack arguments for indirect trampolines Kumar Kartikeya Dwivedi
2026-08-22 0:46 ` bot+bpf-ci
2026-08-21 23:35 ` [PATCH bpf-next v1 08/14] bpf, loongarch: JIT arena kfunc argument rebasing Kumar Kartikeya Dwivedi
2026-08-21 23:46 ` sashiko-bot
2026-08-21 23:35 ` [PATCH bpf-next v1 09/14] bpf, loongarch: Convert struct_ops arena arguments in trampolines Kumar Kartikeya Dwivedi
2026-08-21 23:51 ` sashiko-bot
2026-08-21 23:35 ` [PATCH bpf-next v1 10/14] bpf, powerpc: JIT arena kfunc argument rebasing Kumar Kartikeya Dwivedi
2026-08-22 0:46 ` bot+bpf-ci
2026-08-21 23:35 ` [PATCH bpf-next v1 11/14] bpf: Replace arena kfunc argument flags with suffixes Kumar Kartikeya Dwivedi
2026-08-21 23:58 ` sashiko-bot
2026-08-22 0:46 ` bot+bpf-ci
2026-08-24 22:15 ` Eduard Zingerman
2026-08-24 22:52 ` Kumar Kartikeya Dwivedi
2026-08-26 20:42 ` Ihor Solodrai
2026-08-21 23:35 ` [PATCH bpf-next v1 12/14] resolve_btfids: Drop KF_ARENA_ARG flag support Kumar Kartikeya Dwivedi
2026-08-22 0:46 ` bot+bpf-ci
2026-08-24 22:25 ` Eduard Zingerman
2026-08-24 22:53 ` Kumar Kartikeya Dwivedi
2026-08-26 20:47 ` Ihor Solodrai
2026-08-21 23:35 ` [PATCH bpf-next v1 13/14] selftests/bpf: Exercise arena arguments on every capable JIT Kumar Kartikeya Dwivedi
2026-08-22 0:46 ` bot+bpf-ci
2026-08-26 20:50 ` Ihor Solodrai
2026-08-21 23:35 ` [PATCH bpf-next v1 14/14] docs/bpf: Document split arena argument JIT capabilities Kumar Kartikeya Dwivedi
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