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

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Message-ID: <20191122203213.GF2844@hirez.programming.kicks-ass.net>
Date:   Fri, 22 Nov 2019 21:32:14 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     David Laight <David.Laight@...LAB.COM>
Cc:     'Andy Lutomirski' <luto@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Fenghua Yu <fenghua.yu@...el.com>,
        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 Fri, Nov 22, 2019 at 09:46:16AM +0000, David Laight wrote:
> From Andy Lutomirski

> > Can we really not just change the lock asm to use 32-bit accesses for
> > set_bit(), etc?  Sure, it will fail if the bit index is greater than
> > 2^32, but that seems nuts.
> 
> For little endian 64bit cpu it is safe(ish) to cast int [] to long [] for the bitops.

But that generates the alignment issues this patch set is concerned
about.