linux-kernel - RE: [PATCH 4/4] x86/cpu: Use SERIALIZE in sync

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Date:   Mon, 27 Jul 2020 16:27:18 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     "hpa@...or.com" <hpa@...or.com>,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...e.de>,
        Andy Lutomirski <luto@...nel.org>,
        "x86@...nel.org" <x86@...nel.org>
CC:     "Hansen, Dave" <dave.hansen@...el.com>,
        "Zhang, Cathy" <cathy.zhang@...el.com>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        "Park, Kyung Min" <kyung.min.park@...el.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>,
        "Christopherson, Sean J" <sean.j.christopherson@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Neri, Ricardo" <ricardo.neri@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>
Subject: RE: [PATCH 4/4] x86/cpu: Use SERIALIZE in sync_core() when available

> For a really overenginered solution, but which might perform unnecessary poorly on existing hardware:
>
> asm volatile("1: .byte 0xf, 0x1, 0xe8; 2:"
>                        _ASM_EXTABLE(1b,2b));

You win the prize for the smallest code.  Might need (the already large) comment to double
in size to explain the subtleties!

-Tony