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

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Message-ID: <alpine.DEB.2.21.1806221125240.2402@nanos.tec.linutronix.de>
Date:   Fri, 22 Jun 2018 11:28:21 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Fenghua Yu <fenghua.yu@...el.com>
cc:     Peter Zijlstra <peterz@...radead.org>, 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, 21 Jun 2018, Fenghua Yu wrote:
> The control knob for firmware is to choose continuing firmware execution
> by disabling #AC split lock (default) or stopping firmware execution
> by enabling #AC for split lock. Stopping firmware execution may be useful
> in hard real time system to identify any split lock issue on the platform.

There is no maybe on a real-time system. Either the thing is sane or it's
not. There is no middle ground. The default has to be fail otherwise
firmware wont be fixed ever.

> So the control knobs may be useful for different scenarios, right?

The control knobs are just helping to proliferate crap, so they are not
useful, they are outright counterproductive.

Thanks,

	tglx