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

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Message-ID: <3B214995-70A6-4777-B7E3-F10018F7D71E@zytor.com>
Date: Wed, 04 Dec 2024 07:55:22 -0800
From: "H. Peter Anvin" <hpa@...or.com>
To: Thomas Gleixner <tglx@...utronix.de>, Arnd Bergmann <arnd@...nel.org>,
        linux-kernel@...r.kernel.org, x86@...nel.org
CC: 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 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.