linux-kernel - Re: [PATCH AUTOSEL 6.17-5.4] x86/build: Remove cc-option from stack alignment flags

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Message-ID: <aORNI3nnm5PRvNuT@laps>
Date: Mon, 6 Oct 2025 19:13:39 -0400
From: Sasha Levin <sashal@...nel.org>
To: Nathan Chancellor <nathan@...nel.org>
Cc: patches@...ts.linux.dev, stable@...r.kernel.org,
	"Borislav Petkov (AMD)" <bp@...en8.de>, tglx@...utronix.de,
	mingo@...hat.com, dave.hansen@...ux.intel.com, x86@...nel.org,
	linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH AUTOSEL 6.17-5.4] x86/build: Remove cc-option from stack
 alignment flags

On Mon, Oct 06, 2025 at 02:55:05PM -0700, Nathan Chancellor wrote:
>On Mon, Oct 06, 2025 at 02:17:33PM -0400, Sasha Levin wrote:
>> From: Nathan Chancellor <nathan@...nel.org>
>>
>> [ Upstream commit d87208128a3330c0eab18301ab39bdb419647730 ]
>>
>> '-mpreferred-stack-boundary' (the GCC option) and '-mstack-alignment'
>> (the clang option) have been supported in their respective compilers for
>> some time, so it is unnecessary to check for support for them via
>> cc-option. '-mpreferred-stack-boundary=3' had a restriction on
>> '-mno-sse' until GCC 7.1 but that is irrelevant for most of the kernel,
>> which includes '-mno-sse'.
>>
>> Move to simple Kconfig checks to avoid querying the compiler for the
>> flags that it supports.
>>
>> Signed-off-by: Nathan Chancellor <nathan@...nel.org>
>> Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
>> Link: https://lore.kernel.org/20250814-x86-min-ver-cleanups-v1-2-ff7f19457523@kernel.org
>> Signed-off-by: Sasha Levin <sashal@...nel.org>
>...
>> ## Backport Status: NO
>...
>> **Dependency Analysis:**
>> - Requires minimum GCC 8.1 for x86 (introduced in v6.15 via commit
>>   a3e8fe814ad1)
>> - Requires minimum Clang 15.0.0 for x86 (commit 7861640aac52b)
>> - Both requirements are satisfied in 6.17 stable tree (verified via
>>   scripts/min-tool-version.sh)
>> - GCC 7.1+ supports `-mpreferred-stack-boundary=3` with `-msse` (per GCC
>>   commit 34fac449e121)
>...
>> ### Conclusion
>>
>> While this commit is technically safe and provides a marginal build-time
>> performance improvement by eliminating unnecessary runtime compiler
>> checks, **it does not meet the fundamental requirement for stable kernel
>> backporting**: it does not fix a bug that affects users.
>>
>> The commit is purely a cleanup that removes obsolete code after compiler
>> minimum version requirements were raised. Such cleanups belong in
>> mainline development, not stable trees, which should focus exclusively
>> on fixing bugs that impact users.
>>
>> The fact that it was auto-selected by AUTOSEL does not override the
>> documented stable kernel rules. This commit should be **rejected** from
>> stable backporting or **reverted** if already applied.
>
>Based on all of this, I would agree that it is not really suitable for
>backporting (at least not beyond 6.15, whereas the subject says back to
>5.4), so why was this still sent for review?

Sorry for the noise, I thought I dropped this one :(

-- 
Thanks,
Sasha