linux-kernel - Re: [PATCH 09/11] x86: rework CONFIG_GENERIC

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Message-ID: <Z1GLrISQEaXelzqu@smile.fi.intel.com>
Date: Thu, 5 Dec 2024 13:17:00 +0200
From: Andy Shevchenko <andy@...nel.org>
To: Arnd Bergmann <arnd@...db.de>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
	Arnd Bergmann <arnd@...nel.org>, linux-kernel@...r.kernel.org,
	x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Matthew Wilcox <willy@...radead.org>,
	Sean Christopherson <seanjc@...gle.com>,
	Davide Ciminaghi <ciminaghi@...dd.com>,
	Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org
Subject: Re: [PATCH 09/11] x86: rework CONFIG_GENERIC_CPU compiler flags

On Thu, Dec 05, 2024 at 11:09:41AM +0100, Arnd Bergmann wrote:
> On Thu, Dec 5, 2024, at 09:13, Andy Shevchenko wrote:
> > On Wed, Dec 04, 2024 at 03:33:19PM -0800, Linus Torvalds wrote:
> >> On Wed, 4 Dec 2024 at 11:44, Arnd Bergmann <arnd@...db.de> wrote:

...

> >> Will that work when you cross-compile? No. Do we care? Also no. It's
> >> basically a simple "you want to optimize for your own local machine"
> >> switch.
> >
> > Maybe it's okay for 64-bit machines, but for cross-compiling for 32-bit on
> > 64-bit. I dunno what '-march=native -m32' (or equivalent) will give in such
> > cases.
> 
> From the compiler's perspective this is nothing special, it just
> builds a 32-bit binary that can use any instruction supported in
> 32-bit mode of that 64-bit CPU,

But does this affect building, e.g., for Quark on my Skylake desktop?

> the same as the 32-bit CONFIG_MCORE2 option that I disallow in patch 04/11.

-- 
With Best Regards,
Andy Shevchenko