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

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To: Uros Bizjak <ubizjak@xxxxxxxxx>
Subject: Re: [PATCH RESEND 1/2] x86/locking: Use ALT_OUTPUT_SP() for percpu_{,try_}cmpxchg{64,128}_op()
From: "Christoph Lameter (Ampere)" <cl@xxxxxxxxxx>
Date: Fri, 14 Feb 2025 10:22:08 -0800 (PST)
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>, x86@xxxxxxxxxx, linux-mm@xxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, Dennis Zhou <dennis@xxxxxxxxxx>, Tejun Heo <tj@xxxxxxxxxx>, "Peter Zijlstra (Intel)" <peterz@xxxxxxxxxxxxx>
In-reply-to: <CAFULd4YUSCBSJQ1F0Rn45bwTonQJb2_=c2sZZEGV7RfgHBAOJA@mail.gmail.com>
References: <20250213191457.12377-1-ubizjak@gmail.com> <04adffd9-2900-4cdb-a557-1c486a87b522@intel.com> <CAFULd4YUSCBSJQ1F0Rn45bwTonQJb2_=c2sZZEGV7RfgHBAOJA@mail.gmail.com>

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.

Follow-Ups:
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References:
- [PATCH RESEND 1/2] x86/locking: Use ALT_OUTPUT_SP() for percpu_{,try_}cmpxchg{64,128}_op()
  - From: Uros Bizjak
- Re: [PATCH RESEND 1/2] x86/locking: Use ALT_OUTPUT_SP() for percpu_{,try_}cmpxchg{64,128}_op()
  - From: Dave Hansen
- Re: [PATCH RESEND 1/2] x86/locking: Use ALT_OUTPUT_SP() for percpu_{,try_}cmpxchg{64,128}_op()
  - From: Uros Bizjak

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