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: <CAFULd4YMNsSzNS8wBZBC8iy2uNnoV8kDWpp70r4Wx+-wJ1j1Rg@mail.gmail.com>
Date: Fri, 14 Feb 2025 20:55:09 +0100
From: Uros Bizjak <ubizjak@...il.com>
To: "Christoph Lameter (Ampere)" <cl@...two.org>
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 Fri, Feb 14, 2025 at 7:22 PM Christoph Lameter (Ampere)
<cl@...two.org> wrote:
>
> 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.

I'm not aware of any discussion about that decision.

Thanks,
Uros.