linux-kernel - Re: [PATCH 03/11] x86: Kconfig.cpu: split out 64-bit atom

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Message-ID: <CAHp75VfZW2A1s+QLdVHXnFV16dWhM=T5gtWw97d1gM-Pys+CZw@mail.gmail.com>
Date: Wed, 4 Dec 2024 20:21:04 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: "H. Peter Anvin" <hpa@...or.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Arnd Bergmann <arnd@...nel.org>, linux-kernel@...r.kernel.org, 
	x86@...nel.org, Arnd Bergmann <arnd@...db.de>, Ingo Molnar <mingo@...hat.com>, 
	Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, 
	Linus Torvalds <torvalds@...ux-foundation.org>, Andy Shevchenko <andy@...nel.org>, 
	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 03/11] x86: Kconfig.cpu: split out 64-bit atom

On Wed, Dec 4, 2024 at 5:55 PM H. Peter Anvin <hpa@...or.com> wrote:
>
> On December 4, 2024 5:16:50 AM PST, Thomas Gleixner <tglx@...utronix.de> wrote:
> >On Wed, Dec 04 2024 at 11:30, Arnd Bergmann wrote:
> >> From: Arnd Bergmann <arnd@...db.de>
> >>
> >> Both 32-bit and 64-bit builds allow optimizing using "-march=atom", but
> >> this is somewhat suboptimal, as gcc and clang use this option to refer
> >> to the original in-order "Bonnell" microarchitecture used in the early
> >> "Diamondville" and "Silverthorne" processors that were mostly 32-bit only.
> >>
> >> The later 22nm "Silvermont" architecture saw a significant redesign to
> >> an out-of-order architecture that is reflected in the -mtune=silvermont
> >> flag in the compilers, and all of these are 64-bit capable.
> >
> >In theory. There are quite some crippled variants of silvermont which
> >are 32-bit only (either fused or at least officially not-supported to
> >run 64-bit)...

> Yeah. That was a sad story, which I unfortunately am not at liberty to share.

Are they available in the wild? What I know with that core are
Merrifield, Moorefield, and Bay Trail that were distributed in
millions and are perfectly available, but I never heard about ones
that are 32-bit only. The Avoton and Rangley I have read about on
https://en.wikipedia.org/wiki/Silvermont seems specific to the servers
and routers and most likely are gone from use.


-- 
With Best Regards,
Andy Shevchenko