Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934141AbeAIQQM (ORCPT + 1 other); Tue, 9 Jan 2018 11:16:12 -0500 Received: from mail-wr0-f194.google.com ([209.85.128.194]:33059 "EHLO mail-wr0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933583AbeAIQQL (ORCPT ); Tue, 9 Jan 2018 11:16:11 -0500 X-Google-Smtp-Source: ACJfBosh1fv8nN25edJCblLCcG6gmTiVIQzdOCheMU4IV/0/GL7wYDkfmlK43pChoRodLDhqnfCo6Q== Date: Tue, 9 Jan 2018 17:16:06 +0100 From: Ingo Molnar To: Peter Zijlstra Cc: Vince Weaver , linux-kernel@vger.kernel.org, Ingo Molnar , Arnaldo Carvalho de Melo , Thomas Gleixner Subject: Re: perf: perf_fuzzer quickly locks up on 4.15-rc7 Message-ID: <20180109161606.etvacvfe6rq777ps@gmail.com> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180109153341.GL6176@hirez.programming.kicks-ass.net> User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: * Peter Zijlstra wrote: > On Tue, Jan 09, 2018 at 10:24:55AM -0500, Vince Weaver wrote: > > On Tue, 9 Jan 2018, Peter Zijlstra wrote: > > > > > > I'll try your patch and see if it makes a difference. > > > > > > I suspect not, it shouldn't be PTI specific. > > > > yes, applying your patch didn't help, still locks up on the Haswell > > machine. > > So CONFIG_PAGE_TABLE_ISOLATION=y and booting with "pti=off" makes it > 'work', right? > > > Is there any debugging I could turn on that would help? I tried KASAN > > but it didn't help. I think I have the regular lockdep stuff enabled. > > > > alt-sysrq doesn't work either (or at least, the version using BREAK over > > the serial console doesn't, I can maybe try hooking up a keyboard/display > > to see if that helps). > > The below is always my first try to get something out of the machine, > after that its printk() stuffing code to see how far we get.. > > In particular I'd start instrumenting the NMI entry_64.S code, because > that's really the biggest difference between PTI and !PTI :/ all rather > bothersome I'm afraid. > > Really sucks I cannot as yet reproduce. > > --- > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 5e486b6509e5..fc9021fd6e3c 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -1172,6 +1172,11 @@ > parameter will force ia64_sal_cache_flush to call > ia64_pal_cache_flush instead of SAL_CACHE_FLUSH. > > + force_early_printk > + Forcefully uses early_console (as per earlyprintk=) > + usage for regular printk, bypassing everything, > + including the syslog (dmesg will be empty). BTW., this looks very useful - please consider pushing it upstream if it does not hurt any of the other syslog usecases. Thanks, Ingo