linux-kernel - Re: [PATCH RESEND 1/2] x86/locking: Use ALT_OUTPUT_SP() for percpu_{,try_}cmpxchg{64,128}

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Message-ID: <cf264b5f-be03-af53-3de3-a97051f9577e@gentwo.org>
Date: Fri, 14 Feb 2025 10:22:08 -0800 (PST)
From: "Christoph Lameter (Ampere)" <cl@...two.org>
To: Uros Bizjak <ubizjak@...il.com>
cc: Dave Hansen <dave.hansen@...el.com>, x86@...nel.org, linux-mm@...ck.org, 
    linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>, 
    Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>, 
    Dave Hansen <dave.hansen@...ux.intel.com>, 
    "H. Peter Anvin" <hpa@...or.com>, Dennis Zhou <dennis@...nel.org>, 
    Tejun Heo <tj@...nel.org>, "Peter Zijlstra (Intel)" <peterz@...radead.org>
Subject: Re: [PATCH RESEND 1/2] x86/locking: Use ALT_OUTPUT_SP() for
 percpu_{,try_}cmpxchg{64,128}_op()

On Thu, 13 Feb 2025, Uros Bizjak wrote:

> OTOH, all recent x86_64 processors support CMPXCHG128 insn, so the
> call alternative will be rarely used.

Do we still support processors without cmpxchg128? If not then lets just
drop the calls from the kernel.