linux-kernel - Re: [PATCH v10 6/6] x86/split_lock: Enable split lock detection by kernel parameter

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Message-ID: <20191121080038.GK4097@hirez.programming.kicks-ass.net>
Date:   Thu, 21 Nov 2019 09:00:38 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Fenghua Yu <fenghua.yu@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        Tony Luck <tony.luck@...el.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        linux-kernel <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>
Subject: Re: [PATCH v10 6/6] x86/split_lock: Enable split lock detection by
 kernel parameter

On Wed, Nov 20, 2019 at 04:53:23PM -0800, Fenghua Yu wrote:
> Split lock detection is disabled by default. Enable the feature by
> kernel parameter "split_lock_detect".
> 
> Usually it is enabled in real time when expensive split lock issues
> cannot be tolerated so should be fatal errors, or for debugging and
> fixing the split lock issues to improve performance.
> 
> Please note: enabling this feature will cause kernel panic or SIGBUS
> to user application when a split lock issue is detected.

ARGGGHH, by having this default disabled, firmware will _NEVER_ be
exposed to this before it ships.

How will you guarantee the firmware will not explode the moment you
enable this?