Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758827Ab1CCUrl (ORCPT ); Thu, 3 Mar 2011 15:47:41 -0500 Received: from mx1.redhat.com ([209.132.183.28]:44342 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758472Ab1CCUrj (ORCPT ); Thu, 3 Mar 2011 15:47:39 -0500 Message-ID: <4D6FFE5D.1030401@redhat.com> Date: Thu, 03 Mar 2011 15:47:25 -0500 From: Zachary Amsden User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.10) Gecko/20100621 Fedora/3.0.5-1.fc13 Thunderbird/3.0.5 MIME-Version: 1.0 To: Nikola Ciprich CC: Avi Kivity , Nikola Ciprich , KVM list , Linux kernel list , Glauber Costa Subject: Re: regression - 2.6.36 -> 2.6.37 - kvm - 32bit SMP guests don't boot References: <20110225104823.GD29840@pcnci.linuxbox.cz> <4D67C077.6060108@redhat.com> <20110227172052.GB2474@nik-comp.lan> <4D6BA85B.7080908@redhat.com> <20110228143247.GE29840@pcnci.linuxbox.cz> <4D6BBC84.6020408@redhat.com> <20110228152823.GF29840@pcnci.linuxbox.cz> <4D6BC5CA.8060004@redhat.com> <20110228171550.GA2173@nik-comp.lan> <4D6EF536.305@redhat.com> <20110303070652.GG29840@pcnci.linuxbox.cz> In-Reply-To: <20110303070652.GG29840@pcnci.linuxbox.cz> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1392 Lines: 38 On 03/03/2011 02:06 AM, Nikola Ciprich wrote: >> No worries. What mess? >> > twice sending the same mail, nevermind :) > > >> I have two things you can try: >> >> first is running a single VCPU guest, if you have not done so already. >> > yup, UP guest is fine, just SMP doesn't work. > > >> Second is adding the bootparameter "clocksource=acpi_pm" to your guest >> kernel. >> > yes, this makes SMP work too! I just realized when You were asking about current > clocksource, I told You only host source, not the guest. So I checked now, > and (at least for UP, I guess for SMP it's the same), the clocksource is > kvm-clock! So seems like it got broken with the TSC changes? > What is the exact kernel version you are using in the guest. It appears that some earlier 32-bit versions of kvm-clock enabled kernels are still missing the required atomic check for backwards-time protection which would be needed on SMP. This explains why 64-bit is fine, 32-bit is not. Why this change triggers that problem still is a slight mystery, logically it should only affect the system if you have an unstable TSC. Zach -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/