linux-kernel - Re: [PATCH] x86/Kconfig: Fix dependency for X86_DEBUG

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Message-ID: <a874a35f-b63a-4e7b-8d5a-3696b7f39b74@linuxfoundation.org>
Date: Thu, 10 Apr 2025 15:18:30 -0600
From: Shuah Khan <skhan@...uxfoundation.org>
To: Ingo Molnar <mingo@...nel.org>
Cc: tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
 dave.hansen@...ux.intel.com, x86@...nel.org, linux-kernel@...r.kernel.org,
 hpa@...or.com, Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH] x86/Kconfig: Fix dependency for X86_DEBUG_FPU

On 4/10/25 00:31, Ingo Molnar wrote:
> 
> * Shuah Khan <skhan@...uxfoundation.org> wrote:
> 
>> Yes it is vanilla
> 
> Thx.
> 
>>> More importantly, X86_REQUIRED_FEATURE_FPU *does not exist* in the
>>> vanilla v6.14 kernel, it's a new v6.15 feature. So this part of
>>> your changelog totally doesn't apply to a v6.14 kernel:
>>
>> I started with vanilla 6.14 kernel running oldconfig on it. In this
>> case if X86_DEBUG_FPU is enabled in the oldconfig, should the config
>> generated for 6.15 add X86_REQUIRED_FEATURE_FPU.
>>
>> It appears there is a dependency between X86_DEBUG_FPU and the newly
>> added X86_REQUIRED_FEATURE_FPU
> 
> Could you send the v6.15-rc1 config that has this missing dependency?
> 
> Because if I put the config you sent through 'make oldconfig' and
> accept all default suggestions, the X86_REQUIRED_FEATURE_FPU dependency
> is present:
> 
>   starship:~/tip> grep _FPU .config
>   CONFIG_X86_REQUIRED_FEATURE_FPU=y
>   CONFIG_ARCH_HAS_KERNEL_FPU_SUPPORT=y
>   CONFIG_X86_DEBUG_FPU=y
>   # CONFIG_TEST_FPU is not set
> 
> ... and the build succeeds:
> 
>      OBJCOPY arch/x86/boot/setup.bin
>      BUILD   arch/x86/boot/bzImage
>    Kernel: arch/x86/boot/bzImage is ready  (#4)
> 
> Ie. I cannot reproduce the build failure with the config you provided.
> 

Okay. I ran a few more experiments with a fresh repo. I can't reproduce
the problem.

The only thing I can think of is somehow make didn't run oldconfig or
if it did didn't pick up the right the first time around ... Not sure.

You can ignore this patch. Sorry for the noise.

thanks,
-- Shuah