linux-kernel - Re: [PATCH v2 4/4] x86/static_call: Add inline static call implementation for x86-64

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Message-ID: <20181130152852.456ce379@gandalf.local.home>
Date:   Fri, 30 Nov 2018 15:28:52 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>, X86 ML <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Jason Baron <jbaron@...mai.com>, Jiri Kosina <jkosina@...e.cz>,
        David Laight <David.Laight@...lab.com>,
        Borislav Petkov <bp@...en8.de>, julia@...com, jeyu@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v2 4/4] x86/static_call: Add inline static call
 implementation for x86-64

On Fri, 30 Nov 2018 12:18:33 -0800
Andy Lutomirski <luto@...nel.org> wrote:

> Or we could replace that IPI with x86's bona fide serialize-all-cpus
> primitive and then we can just retry instead of emulating.  It's a
> piece of cake -- we just trigger an SMI :)  /me runs away.

I must have fallen on my head one too many times, because I really like
the idea of synchronizing all the CPUs with an SMI! (If that's even
possible). The IPI's that are sent are only to force smp_mb() on all
CPUs. Which should be something an SMI could do.

/me runs after Andy

-- Steve