linux-kernel - Re: [RFC PATCH 02/16] x86/split_lock: Handle #AC exception for split lock in kernel mode

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Message-ID: <20180621194656.GB13636@worktop.programming.kicks-ass.net>
Date:   Thu, 21 Jun 2018 21:46:56 +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 02/16] x86/split_lock: Handle #AC exception for split
 lock in kernel mode

On Sun, May 27, 2018 at 08:45:51AM -0700, Fenghua Yu wrote:
> When #AC exception for split lock is triggered from a kernel instruction,
> by default we don't want the exception to panic the whole system. Instead,
> the exception handler should log the fault information for debug and
> continue the instruction execution.

This should not happen today, did you find any unaligned LOCK insns?

This is a lot of code to 'handle' something that really should not ever
happen. Maybe just WARN and clear the MSR bit, nothing complicated.

Also, fix your "disgusting drug-induced crap" comments.