Re: [PATCH v2 02/15] x86/cpu: Extract cpuid helpers to arch-independent

From: Borislav Petkov <bp@alien8.de>
To: Iwona Winiarska <iwona.winiarska@intel.com>
Cc: linux-kernel@vger.kernel.org, openbmc@lists.ozlabs.org,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	x86@kernel.org, devicetree@vger.kernel.org,
	linux-aspeed@lists.ozlabs.org,
	linux-arm-kernel@lists.infradead.org,
	linux-hwmon@vger.kernel.org, linux-doc@vger.kernel.org,
	Rob Herring <robh+dt@kernel.org>, Joel Stanley <joel@jms.id.au>,
	Andrew Jeffery <andrew@aj.id.au>,
	Jean Delvare <jdelvare@suse.com>,
	Guenter Roeck <linux@roeck-us.net>, Arnd Bergmann <arnd@arndb.de>,
	Olof Johansson <olof@lixom.net>, Jonathan Corbet <corbet@lwn.net>,
	Thomas Gleixner <tglx@linutronix.de>,
	Andy Lutomirski <luto@kernel.org>, Ingo Molnar <mingo@redhat.com>,
	Yazen Ghannam <yazen.ghannam@amd.com>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>,
	Tony Luck <tony.luck@intel.com>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Randy Dunlap <rdunlap@infradead.org>,
	Zev Weiss <zweiss@equinix.com>,
	David Muller <d.mueller@elsoft.ch>
Subject: Re: [PATCH v2 02/15] x86/cpu: Extract cpuid helpers to arch-independent
Date: Mon, 4 Oct 2021 21:08:22 +0200	[thread overview]
Message-ID: <YVtRJiYD9EqGh7TM@zn.tnic> (raw)
In-Reply-To: <20210803113134.2262882-3-iwona.winiarska@intel.com>

On Tue, Aug 03, 2021 at 01:31:21PM +0200, Iwona Winiarska wrote:
> Baseboard management controllers (BMC) often run Linux but are usually
> implemented with non-X86 processors. They can use PECI to access package
> config space (PCS) registers on the host CPU and since some information,
> e.g. figuring out the core count, can be obtained using different
> registers on different CPU generations, they need to decode the family
> and model.
> 
> The format of Package Identifier PCS register that describes CPUID
> information has the same layout as CPUID_1.EAX, so let's allow to reuse
> cpuid helpers by making it available for other architectures as well.
> 
> Signed-off-by: Iwona Winiarska <iwona.winiarska@intel.com>
> Reviewed-by: Tony Luck <tony.luck@intel.com>
> Reviewed-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  MAINTAINERS                      | 1 +
>  arch/x86/Kconfig                 | 1 +
>  arch/x86/include/asm/cpu.h       | 3 ---
>  arch/x86/include/asm/microcode.h | 2 +-
>  arch/x86/kvm/cpuid.h             | 3 ++-
>  arch/x86/lib/Makefile            | 2 +-
>  drivers/edac/mce_amd.c           | 3 +--
>  include/linux/x86/cpu.h          | 9 +++++++++
>  lib/Kconfig                      | 4 ++++
>  lib/Makefile                     | 2 ++
>  lib/x86/Makefile                 | 3 +++
>  {arch/x86/lib => lib/x86}/cpu.c  | 2 +-
>  12 files changed, 26 insertions(+), 9 deletions(-)
>  create mode 100644 include/linux/x86/cpu.h
>  create mode 100644 lib/x86/Makefile
>  rename {arch/x86/lib => lib/x86}/cpu.c (95%)

AFAICT, all that churn is done for x86_family() and x86_model() which
are used *exactly* *once* and which are almost trivial anyway.

What's wrong with simply computing the family and model "by hand", so to
speak, in peci_device_info_init() and do away with that diffstat

 12 files changed, 26 insertions(+), 9 deletions(-)

?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette