From: "Kumar Kartikeya Dwivedi" <memxor@gmail.com>
To: <bot+bpf-ci@kernel.org>, <bpf@vger.kernel.org>
Cc: <ast@kernel.org>, <andrii@kernel.org>, <daniel@iogearbox.net>,
<eddyz87@gmail.com>, <emil@etsalapatis.com>, <tj@kernel.org>,
<kkd@meta.com>, <kernel-team@meta.com>, <martin.lau@kernel.org>,
<yonghong.song@linux.dev>, <mason@kernel.org>,
<ihor.solodrai@linux.dev>
Subject: Re: [PATCH bpf-next v2 17/18] bpf, arm64: Allow programs 2 KiB of stack
Date: Thu, 24 Sep 2026 11:57:45 +0200 [thread overview]
Message-ID: <DLNGHIB312GJ.2YIJYBY4U9TNZ@gmail.com> (raw)
In-Reply-To: <4ee0bb9bfdc8274a074f6e80dfc65d386e15586e27dd3951317d0eb4b01aa0f3@mail.kernel.org>
On Thu Sep 24, 2026 at 11:00 AM CEST, bot+bpf-ci wrote:
>> diff --git a/Documentation/bpf/bpf_design_QA.rst b/Documentation/bpf/bpf_design_QA.rst
>> index be5fc4ac00d6..98d70b8a2533 100644
>> --- a/Documentation/bpf/bpf_design_QA.rst
>> +++ b/Documentation/bpf/bpf_design_QA.rst
>> @@ -223,11 +223,12 @@ Q: How much stack space a BPF program uses?
>> -------------------------------------------
>> A: A program may use up to 2 KiB of stack, combined over its call
>> chain, when the JIT of the architecture reports support for large
>> -stacks (currently x86-64); a single function may use all of it, and
>> -every frame of a program running on a private stack gets the whole
>> -amount. Elsewhere, and whenever the interpreter is used, the limit is
>> -512 bytes. The verifier computes the actual amount of stack used and
>> -both interpreter and most JITed code consume necessary amount.
>> +stacks (currently x86-64 and arm64); a single function may use all of
>> +it, and every frame of a program running on a private stack gets the
>> +whole amount. Elsewhere, and for programs verified for the interpreter,
>> +the limit is 512 bytes; the interpreter itself never runs a frame
>> +larger than that. The verifier computes the actual amount of stack
>> +used and both interpreter and most JITed code consume necessary amount.
>
> This isn't a bug, but the interpreter sentence changes meaning here,
> not just the architecture list. The old sentence said "whenever the
> interpreter is used, the limit is 512 bytes" while the new one says
> "for programs verified for the interpreter, the limit is 512 bytes; the
> interpreter itself never runs a frame larger than that."
>
> Would this correction fit better in the x86 patch that first added the
> paragraph, or could the changelog say why it changes?
>
Not a bug; the sentence was corrected in the patch that adds arm64 because that
is where the wording was revisited, and it stays here.
> [ ... ]
>
>
> ---
> AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
> See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
>
> CI run summary: https://github.com/kernel-patches/bpf/actions/runs/35976322553
next prev parent reply other threads:[~2026-09-24 9:57 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-24 8:25 [PATCH bpf-next v2 00/18] Raise BPF program stack size to 2KiB Kumar Kartikeya Dwivedi
2026-09-24 8:25 ` [PATCH bpf-next v2 01/18] bpf: Add accessors for verifier stack slots Kumar Kartikeya Dwivedi
2026-09-24 8:25 ` [PATCH bpf-next v2 02/18] bpf: Widen the stack slot index in the jump history Kumar Kartikeya Dwivedi
2026-09-24 8:25 ` [PATCH bpf-next v2 03/18] bpf: Store linked registers in the jump history as an array Kumar Kartikeya Dwivedi
2026-09-24 8:25 ` [PATCH bpf-next v2 04/18] bpf: Track backtracking stack slots with bitmaps Kumar Kartikeya Dwivedi
2026-09-24 8:25 ` [PATCH bpf-next v2 05/18] bpf: Track scratched stack slots with a bitmap Kumar Kartikeya Dwivedi
2026-09-24 8:25 ` [PATCH bpf-next v2 06/18] bpf: Treat unknown-size stack reads as reaching the frame top Kumar Kartikeya Dwivedi
2026-09-24 8:25 ` [PATCH bpf-next v2 07/18] bpf: Size liveness stack masks by the stack each frame uses Kumar Kartikeya Dwivedi
2026-09-24 15:12 ` Alexei Starovoitov
2026-09-24 8:25 ` [PATCH bpf-next v2 08/18] bpf: Grow the verifier id scratch on demand Kumar Kartikeya Dwivedi
2026-09-24 9:13 ` bot+bpf-ci
2026-09-24 9:55 ` Kumar Kartikeya Dwivedi
2026-09-24 8:25 ` [PATCH bpf-next v2 09/18] selftests/bpf: Cover the tail call caller stack depth limit Kumar Kartikeya Dwivedi
2026-09-24 8:25 ` [PATCH bpf-next v2 10/18] selftests/bpf: Check that narrow stack stores define no slot Kumar Kartikeya Dwivedi
2026-09-24 8:25 ` [PATCH bpf-next v2 11/18] selftests/bpf: Check liveness merge of masks with different widths Kumar Kartikeya Dwivedi
2026-09-24 8:25 ` [PATCH bpf-next v2 12/18] bpf: Size the per-frame verifier structures for a 2 KiB stack Kumar Kartikeya Dwivedi
2026-09-24 9:13 ` bot+bpf-ci
2026-09-24 9:56 ` Kumar Kartikeya Dwivedi
2026-09-24 8:25 ` [PATCH bpf-next v2 13/18] bpf: Bound program stack use by a per-program limit Kumar Kartikeya Dwivedi
2026-09-24 9:13 ` bot+bpf-ci
2026-09-24 9:56 ` Kumar Kartikeya Dwivedi
2026-09-24 8:25 ` [PATCH bpf-next v2 14/18] selftests/bpf: Add load conditions on the program stack limit Kumar Kartikeya Dwivedi
2026-09-24 8:25 ` [PATCH bpf-next v2 15/18] selftests/bpf: Give the 512-byte stack boundary tests a 2 KiB twin Kumar Kartikeya Dwivedi
2026-09-24 9:13 ` bot+bpf-ci
2026-09-24 9:56 ` Kumar Kartikeya Dwivedi
2026-09-24 8:25 ` [PATCH bpf-next v2 16/18] bpf, x86: Allow programs 2 KiB of stack Kumar Kartikeya Dwivedi
2026-09-24 9:13 ` bot+bpf-ci
2026-09-24 9:57 ` Kumar Kartikeya Dwivedi
2026-09-24 8:25 ` [PATCH bpf-next v2 17/18] bpf, arm64: " Kumar Kartikeya Dwivedi
2026-09-24 9:00 ` bot+bpf-ci
2026-09-24 9:57 ` Kumar Kartikeya Dwivedi [this message]
2026-09-24 8:25 ` [PATCH bpf-next v2 18/18] selftests/bpf: Test the 2 KiB stack budget Kumar Kartikeya Dwivedi
2026-09-24 9:13 ` bot+bpf-ci
2026-09-24 9:58 ` Kumar Kartikeya Dwivedi
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