Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760000AbeAIRHT (ORCPT + 1 other); Tue, 9 Jan 2018 12:07:19 -0500 Received: from mx1.redhat.com ([209.132.183.28]:35814 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759985AbeAIRHR (ORCPT ); Tue, 9 Jan 2018 12:07:17 -0500 Date: Tue, 9 Jan 2018 11:07:16 -0600 From: Josh Poimboeuf To: Peter Zijlstra Cc: Vince Weaver , Ingo Molnar , linux-kernel@vger.kernel.org, Ingo Molnar , Arnaldo Carvalho de Melo , Thomas Gleixner , Andy Lutomirski Subject: Re: perf: perf_fuzzer quickly locks up on 4.15-rc7 Message-ID: <20180109170716.bqmexpmywwr4bwuv@treble> References: <20180108173005.lkglqrixb2ota6g2@gmail.com> <20180109102507.GG6176@hirez.programming.kicks-ass.net> <20180109132602.GA2369@hirez.programming.kicks-ass.net> <20180109151253.GK6176@hirez.programming.kicks-ass.net> <20180109153341.GL6176@hirez.programming.kicks-ass.net> <20180109160551.GK3040@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20180109160551.GK3040@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.6.0.1 (2016-04-01) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Tue, 09 Jan 2018 17:07:17 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On Tue, Jan 09, 2018 at 05:05:51PM +0100, Peter Zijlstra wrote: > On Tue, Jan 09, 2018 at 10:56:52AM -0500, Vince Weaver wrote: > > On Tue, 9 Jan 2018, Peter Zijlstra wrote: > > > > > So CONFIG_PAGE_TABLE_ISOLATION=y and booting with "pti=off" makes it > > > 'work', right? > > > > yes. Previously I was changing CONFIG_PAGE_TABLE_ISOLATION and > > recompiling, but just now I booted with it set to yes and pti=off and the > > fuzzer has been running fine for a half hour (usually it crashes in under > > 5 minutes). > > > > I did see these in the logs which I don't think I've seen before. > > > > WARNING: stack recursion on stack type 2 > > WARNING: can't dereference iret registers at 000000000783fea8 for ip paranoid_entry+0x2e/0x90 > > WARNING: can't dereference registers at 00000000f0698d17 for ip paranoid_entry+0x4c/0x90 > > WARNING: stack going in the wrong direction? ip=native_sched_clock+0x9/0x90 > > I've seen that last one, but not the ones before. Josh, this isn't > healty, right? :-) Looks like some funky things may be happening on the stack there, though we have seen some issues related to ORC getting confused by paravirt patching. I'm a bit swamped at the moment but I'll look deeper as time permits... -- Josh