linux-kernel - Re: [PATCH 04/15] x86/kbuild: Introduce the 'x86

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Message-Id: <80bf15f5-b34a-4095-beb5-ae9a530da9a4@app.fastmail.com>
Date: Fri, 09 May 2025 20:05:56 +0200
From: "Arnd Bergmann" <arnd@...db.de>
To: "Ingo Molnar" <mingo@...nel.org>
Cc: linux-kernel@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>,
 "Linus Torvalds" <torvalds@...ux-foundation.org>,
 "Peter Zijlstra" <peterz@...radead.org>, "Borislav Petkov" <bp@...en8.de>,
 "Thomas Gleixner" <tglx@...utronix.de>,
 "Vitaly Kuznetsov" <vkuznets@...hat.com>, "Ard Biesheuvel" <ardb@...nel.org>,
 "David Woodhouse" <dwmw@...zon.co.uk>,
 "Masahiro Yamada" <yamada.masahiro@...ionext.com>,
 "Michal Marek" <michal.lkml@...kovi.net>
Subject: Re: [PATCH 04/15] x86/kbuild: Introduce the 'x86_32' subarchitecture

On Wed, May 7, 2025, at 08:35, Ingo Molnar wrote:
> * Arnd Bergmann <arnd@...db.de> wrote:
>> On Tue, May 6, 2025, at 19:09, Ingo Molnar wrote:

>> Also, I don't think there are any systems that return 'x86_32' from 
>> 'uname -m', so your added special case would never be used by 
>> default, only when cross-compiling from some other architecture.
>
> No, on most 32-bit systems 'uname -m' returns 'i686', which we cannot 
> use straight away anyway. And it looked a bit silly to me for us to 
> fudge over the architecture from 'i686' to 'i386', when we haven't 
> supported i386 for quite some while and are now working on i486 
> removal...
>
> Let's just have x86_32 as the internal primary subarchitecture name, 
> with support for historic aliases like 'i386'. That it cleans up things 
> for defconfig naming is a bonus.

If we're going to remove the ARCH=i386 stuff anyway, I wouldn't add
x86_32 now, what I suggested was to  remove both i386 and x86_64 as
identifiers here and just keep ARCH=x86 internally. It's only used
in two places anyway: the 'make defconfig' and the CONFIG_64BIT
selection.

The SUBARCH= logic is independent of that, this bit is only used
for arch/um/, though that would have to change the same way as
arch/x86

      Arnd