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

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Date:   Fri, 22 Nov 2019 12:42:04 -0800
From:   Fenghua Yu <fenghua.yu@...el.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     "Luck, Tony" <tony.luck@...el.com>, Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "Shankar, Ravi V" <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 09:23:45PM +0100, Peter Zijlstra wrote:
> On Fri, Nov 22, 2019 at 06:02:04PM +0000, Luck, Tony wrote:
> > > it requires we get the kernel and firmware clean, but only warns about
> > > dodgy userspace, which I really don't think there is much of.
> > >
> > > getting the kernel clean should be pretty simple.
> > 
> > Fenghua has a half dozen additional patches (I think they were
> > all posted in previous iterations of the patch) that were found by
> > code inspection, rather than by actually hitting them.
> 
> I thought we merged at least some of that, but maybe my recollection is
> faulty.

At least 2 key fixes are in TIP tree:
https://lore.kernel.org/lkml/157384597983.12247.8995835529288193538.tip-bot2@tip-bot2/
https://lore.kernel.org/lkml/157384597947.12247.7200239597382357556.tip-bot2@tip-bot2/

The two issues are blocking kernel boot when split lock is enabled.

> 
> > Those should go in ahead of this.
> 
> Yes, we should make the kernel as clean as possible before doing this.

I'll send out other 6 fixes for atomic bitops shortly. These issues are found
by code inspection.

Thanks.

-Fenghua