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Date: Mon, 18 Mar 2024 10:08:04 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
To: Xin Li <xin@zytor.com>, linux-kernel@vger.kernel.org,
        linux-perf-users@vger.kernel.org
CC: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
        dave.hansen@linux.intel.com, x86@kernel.org, will@kernel.org,
        peterz@infradead.org, akpm@linux-foundation.org, acme@kernel.org,
        namhyung@kernel.org
Subject: =?US-ASCII?Q?Re=3A_=5BPATCH_v1_0/3=5D_x86/cpufeatures=3A_Automatical?=
 =?US-ASCII?Q?ly_generate_required_and_disabled_feature_masks?=
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On March 18, 2024 10:01:19 AM PDT, Xin Li <xin@zytor=2Ecom> wrote:
>On 1/31/2024 9:46 PM, Xin Li (Intel) wrote:
>> When a CPU feature is not configured, e=2Eg=2E, CONFIG_X86_FRED=3Dn, in=
 a
>> build config, its feature disable flag, e=2Eg=2E DISABLE_FRED, needs to
>> be defined and added to a specific disabled CPU features mask in
>> <asm/disabled-features=2Eh>, as the following commit:
>> https://git=2Ekernel=2Eorg/pub/scm/linux/kernel/git/tip/tip=2Egit/commi=
t/?h=3Dx86/fred&id=3De554a8ca49d6d6d782f546ae4d7f036946e7dd87
>>=20
>> This patch set adds an awk script to automatically generate a header
>> with required and disabled CPU features masks based on build config=2E
>
>A gentle ping=2E
>
>This is an infrastructural improvement which has a lower priority,
>however it would be nice to get some feedback first=2E
>
>Thanks!
>    Xin
>
>
>>=20
>>=20
>> H=2E Peter Anvin (Intel) (2):
>>    x86/cpufeatures: Add {required,disabled} feature configs
>>    x86/cpufeatures: Generate a feature mask header based on build confi=
g
>>=20
>> Xin Li (Intel) (1):
>>    x86/cpufeatures: Remove {disabled,required}-features=2Eh
>>=20
>>   arch/x86/Kconfig                              |   4 +-
>>   arch/x86/Kconfig=2Ecpu                          |  16 +-
>>   arch/x86/Kconfig=2Ecpufeatures                  | 149 +++++++++++++++=
++
>>   arch/x86/Makefile                             |  17 +-
>>   arch/x86/boot/cpucheck=2Ec                      |   3 +-
>>   arch/x86/boot/cpuflags=2Ec                      |   1 -
>>   arch/x86/boot/mkcpustr=2Ec                      |   3 +-
>>   arch/x86/include/asm/Kbuild                   |   1 +
>>   arch/x86/include/asm/asm-prototypes=2Eh         |   2 +-
>>   arch/x86/include/asm/atomic64_32=2Eh            |   2 +-
>>   arch/x86/include/asm/bitops=2Eh                 |   4 +-
>>   arch/x86/include/asm/cmpxchg_32=2Eh             |   4 +-
>>   arch/x86/include/asm/cpufeature=2Eh             |   1 +
>>   arch/x86/include/asm/cpufeatures=2Eh            |   8 -
>>   arch/x86/include/asm/disabled-features=2Eh      | 154 ---------------=
---
>>   arch/x86/include/asm/required-features=2Eh      | 104 ------------
>>   arch/x86/kernel/verify_cpu=2ES                  |   1 +
>>   arch/x86/lib/Makefile                         |   2 +-
>>   arch/x86/lib/cmpxchg8b_emu=2ES                  |   2 +-
>>   arch/x86/tools/featuremasks=2Eawk               | 108 ++++++++++++
>>   lib/atomic64_test=2Ec                           |   2 +-
>>   tools/arch/x86/include/asm/cpufeatures=2Eh      |   8 -
>>   =2E=2E=2E/arch/x86/include/asm/disabled-features=2Eh  | 154 ---------=
---------
>>   =2E=2E=2E/arch/x86/include/asm/required-features=2Eh  | 104 ---------=
---
>>   tools/perf/check-headers=2Esh                   |   2 -
>>   25 files changed, 303 insertions(+), 553 deletions(-)
>>   create mode 100644 arch/x86/Kconfig=2Ecpufeatures
>>   delete mode 100644 arch/x86/include/asm/disabled-features=2Eh
>>   delete mode 100644 arch/x86/include/asm/required-features=2Eh
>>   create mode 100755 arch/x86/tools/featuremasks=2Eawk
>>   delete mode 100644 tools/arch/x86/include/asm/disabled-features=2Eh
>>   delete mode 100644 tools/arch/x86/include/asm/required-features=2Eh
>>=20
>>=20
>> base-commit: 078b7b997b47c7166c1240cf1d39db9f646a56be
>

A key pay of this is that it eliminates the need to manually assign featur=
es to cpufeature words=2E It was one thing when there were four of them, bu=
t with over 20 it is going to cause mistakes=2E