linux-kernel - Re: [RFC PATCH 00/16] x86/split_lock: Enable #AC exception for split locked accesses

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Message-ID: <20180621221337.GE2494@hirez.programming.kicks-ass.net>
Date:   Fri, 22 Jun 2018 00:13:37 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Fenghua Yu <fenghua.yu@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
        "H. Peter Anvin" <hpa@...ux.intel.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Rafael Wysocki <rafael.j.wysocki@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Alan Cox <alan@...ux.intel.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        Arjan van de Ven <arjan@...radead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>
Subject: Re: [RFC PATCH 00/16] x86/split_lock: Enable #AC exception for split
 locked accesses

On Thu, Jun 21, 2018 at 03:00:03PM -0700, Fenghua Yu wrote:
> For example, on a consolidated real-time machine, some cores are running

> Another example, in a public cloud deployed in the field, a user process

In either case a single split-lock shouldn't be a real problem, if you
program the event with a count of 1 and have the NMI handler kill the
offending task, you should be good.

Not saying the #AC isn't nicer, just saying the PMU based thing can
still work.