Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759005AbeAIP5B (ORCPT + 1 other); Tue, 9 Jan 2018 10:57:01 -0500 Received: from mail-io0-f181.google.com ([209.85.223.181]:39810 "EHLO mail-io0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758913AbeAIP45 (ORCPT ); Tue, 9 Jan 2018 10:56:57 -0500 X-Google-Smtp-Source: ACJfBovQAEP6GemjH/U2Zzx6kZzrBG/Wj05jD8nH1WfpEpb1jL97leMV4XfXlMdZ//jhZ0KaSsePqw== From: Vince Weaver X-Google-Original-From: Vince Weaver Date: Tue, 9 Jan 2018 10:56:52 -0500 (EST) X-X-Sender: vince@macbook-air To: Peter Zijlstra cc: Ingo Molnar , 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 In-Reply-To: <20180109153341.GL6176@hirez.programming.kicks-ass.net> Message-ID: 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> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: 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 > 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. I'll try that next. Also getting a few other machines up and into a state that I can start fuzzing on them. (extra challenge, the lab my machines is in possibly has a leak in the roof, and they're calling for an inch of rain on top of 3 feet of existing snow so I might have to shut everything down and relocate on short notice). Vince