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

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Message-ID: <alpine.DEB.2.21.1801081528110.14364@macbook-air>
Date:   Mon, 8 Jan 2018 15:29:42 -0500 (EST)
From:   Vince Weaver <vincent.weaver@...ne.edu>
To:     Ingo Molnar <mingo@...nel.org>
cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: perf: perf_fuzzer quickly locks up on 4.15-rc7

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.

It's a hard lockup with nothing over the serial console.  It is not 
deterministic/reproducible either.

Vince