Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1752986AbeAIKZP (ORCPT <rfc822;ralf@linux-mips.org> + 1 other);
        Tue, 9 Jan 2018 05:25:15 -0500
Received: from bombadil.infradead.org ([65.50.211.133]:44675 "EHLO
        bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1751165AbeAIKZM (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 9 Jan 2018 05:25:12 -0500
Date: Tue, 9 Jan 2018 11:25:07 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Vince Weaver <vincent.weaver@maine.edu>
Cc: Ingo Molnar <mingo@kernel.org>, linux-kernel@vger.kernel.org,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: Re: perf: perf_fuzzer quickly locks up on 4.15-rc7
Message-ID: <20180109102507.GG6176@hirez.programming.kicks-ass.net>
References: <alpine.DEB.2.21.1801081105570.319@macbook-air>
 <20180108173005.lkglqrixb2ota6g2@gmail.com>
 <alpine.DEB.2.21.1801081528110.14364@macbook-air>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <alpine.DEB.2.21.1801081528110.14364@macbook-air>
User-Agent: Mutt/1.9.2 (2017-12-15)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Return-Path: <linux-kernel-owner@vger.kernel.org>

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...