linux-kernel - Re: perf: perf_fuzzer quickly locks up on 4.15-rc7

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Message-ID: <20180109102507.GG6176@hirez.programming.kicks-ass.net>
Date:   Tue, 9 Jan 2018 11:25:07 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Vince Weaver <vincent.weaver@...ne.edu>
Cc:     Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: perf: perf_fuzzer quickly locks up on 4.15-rc7

On Mon, Jan 08, 2018 at 03:29:42PM -0500, Vince Weaver wrote:
> On Mon, 8 Jan 2018, Ingo Molnar wrote:
> > 
> > Note that the page table isolation (PTI) feature has a number of effects on perf 
> > and on NMI handlers, so one of the things to try would be to disable PTI.
> 
> Yes, it seems to be a KPTI issue.
> 
> With KPTI disabled I can fuzz for a few hours, no problems.
> 
> With KPTI enabled the perf_fuzzer on this haswell machine will lock up 
> within minutes.

I'll go take a look...