Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935672AbeAKTu1 (ORCPT + 1 other); Thu, 11 Jan 2018 14:50:27 -0500 Received: from bombadil.infradead.org ([65.50.211.133]:32963 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932684AbeAKTuY (ORCPT ); Thu, 11 Jan 2018 14:50:24 -0500 Date: Thu, 11 Jan 2018 20:50:18 +0100 From: Peter Zijlstra To: Josh Poimboeuf 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: <20180111195018.GB3397@worktop> References: <20180109151253.GK6176@hirez.programming.kicks-ass.net> <20180109153341.GL6176@hirez.programming.kicks-ass.net> <20180109160551.GK3040@hirez.programming.kicks-ass.net> <20180109170716.bqmexpmywwr4bwuv@treble> <20180111052538.2qhj6oxnc24xumhk@treble> <20180111192112.d35nkotzklicd27c@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180111192112.d35nkotzklicd27c@treble> User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On Thu, Jan 11, 2018 at 01:21:12PM -0600, Josh Poimboeuf wrote: > Yuck. This time it was stack recursion on the entry stack. In the > previous error, recursion was detected on the IRQ stack. Otherwise they > look quite similar. > > Was that also with nopti? Both with pti enabled, nopti makes things work again. > I haven't had a chance to try it yet, any idea if these would be > recreatable in a VM? Good question; typically we run the perf fuzzer on read hardware because the PMU doesn't virtualize much. But if software perf is enough to trigger this, that would certainly help.