linux-kernel - Re: [PATCH v2 01/15] x86/cpu: Move intel-family to arch-independent headers

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Date:   Mon, 11 Oct 2021 12:40:18 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Winiarska, Iwona" <iwona.winiarska@...el.com>,
        "bp@...en8.de" <bp@...en8.de>
Cc:     "corbet@....net" <corbet@....net>,
        "jae.hyun.yoo@...ux.intel.com" <jae.hyun.yoo@...ux.intel.com>,
        "d.mueller@...oft.ch" <d.mueller@...oft.ch>,
        "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>,
        "andrew@...id.au" <andrew@...id.au>,
        "Luck, Tony" <tony.luck@...el.com>,
        "Lutomirski, Andy" <luto@...nel.org>,
        "andriy.shevchenko@...ux.intel.com" 
        <andriy.shevchenko@...ux.intel.com>,
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        "x86@...nel.org" <x86@...nel.org>,
        "Williams, Dan J" <dan.j.williams@...el.com>
Subject: Re: [PATCH v2 01/15] x86/cpu: Move intel-family to arch-independent
 headers

On 10/11/21 12:21 PM, Winiarska, Iwona wrote:
> On Mon, 2021-10-04 at 21:03 +0200, Borislav Petkov wrote:
>> On Tue, Aug 03, 2021 at 01:31:20PM +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.
>>>
>>> Move the data from arch/x86/include/asm/intel-family.h into a new file
>>> include/linux/x86/intel-family.h so that it can be used by other
>>> architectures.
>>>
>>> Signed-off-by: Iwona Winiarska <iwona.winiarska@...el.com>
>>> Reviewed-by: Tony Luck <tony.luck@...el.com>
>>> Reviewed-by: Dan Williams <dan.j.williams@...el.com>
>>> ---
>>> To limit tree-wide changes and help people that were expecting
>>> intel-family defines in arch/x86 to find it more easily without going
>>> through git history, we're not removing the original header
>>> completely, we're keeping it as a "stub" that includes the new one.
>>> If there is a consensus that the tree-wide option is better,
>>> we can choose this approach.
>> Why can't the linux/ namespace header include the x86 one so that
>> nothing changes for arch/x86/?
> Same reason why PECI can't just include arch/x86 directly (we're building for
> ARM, not x86).
If you're in include/linux/x86-hacks.h, what prevents you from doing

#include "../../arch/x86/include/asm/intel-family.h"

?

In the end, to the compiler, it's just a file in a weird location in the
tree.  I think I'd prefer one weird include to moving that file out of
arch/x86.