Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1031475AbcCQSau (ORCPT ); Thu, 17 Mar 2016 14:30:50 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56475 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S967213AbcCQSak (ORCPT ); Thu, 17 Mar 2016 14:30:40 -0400 Date: Thu, 17 Mar 2016 18:30:38 +0000 From: "Richard W.M. Jones" To: Josh Boyer Cc: Thomas Gleixner , x86 , "Linux-Kernel@Vger. Kernel. Org" Subject: Re: Oops from calibrate_delay_is_known on qemu machine with Linux v4.5-1523-g271ecc5253e2 Message-ID: <20160317183038.GG1681@redhat.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-12-10) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1160 Lines: 28 On Thu, Mar 17, 2016 at 01:54:36PM -0400, Josh Boyer wrote: > Hi Thomas, > > We've had a report [1] of the mainline kernel crashing on a single-cpu > QEMU machine (not kvm) in Fedora. It looks as if the emulated machine > is failing to provide a TSC and the calibrate_delay_is_known function > is passing NULL to cpumask_any_but for the mask parameter. At least > that's all I've been able to discern thus far. > > I was wondering if you had any insight into this issue, given your > recent commit to change calibrate_delay_is_known to use > topology_core_cpumask. The backtrace is below. Thanks for reporting this upstream Josh. I've added to the bug a simple test script that reproduces the issue, not 100% reliably by any means, but some of the time. See: https://bugzilla.redhat.com/show_bug.cgi?id=1318596#c6 Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-df lists disk usage of guests without needing to install any software inside the virtual machine. Supports Linux and Windows. http://people.redhat.com/~rjones/virt-df/