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

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Message-ID: <6fbff2df-96c9-db51-371b-a23d1a84d070@intel.com>
Date:   Thu, 21 Jun 2018 15:18:19 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        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>,
        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 06/21/2018 03:08 PM, Peter Zijlstra wrote:
> On Thu, Jun 21, 2018 at 03:00:03PM -0700, Fenghua Yu wrote:
>> The control knob for kernel is to choose re-executing the faulting
>> instruction (default) or kernel panic. Kernel panic may be useful in hard
>> real time which has less tolerant to bad performance.
> The kernel should never trigger this, ever. Any #AC is a plain bug and
> should be fixed. So unconditional WARN+disable is suffient.

It sounds like we need to start with that functionality and then if
Fenghua wants to do more, we have add-on patches that can be evaluated
by themselves.