From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: 2.6.35-rc1 regression with pvclock and smp guests Date: Sun, 25 Jul 2010 11:44:27 +0300 Message-ID: <4C4BF96B.7010005@redhat.com> References: <4C483F67.1010007@amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: glommer@redhat.com, Zachary Amsden , KVM list To: Andre Przywara Return-path: Received: from mx1.redhat.com ([209.132.183.28]:30077 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751377Ab0GYIoa (ORCPT ); Sun, 25 Jul 2010 04:44:30 -0400 In-Reply-To: <4C483F67.1010007@amd.com> Sender: kvm-owner@vger.kernel.org List-ID: On 07/22/2010 03:53 PM, Andre Przywara wrote: > Hi, > > I found a regression with pvclock and SMP KVM _guests_. > PVCLOCK enabled guest kernels boot with qemu-kvm.git and with smp=1, > but with smp=2 halt at: > > Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled > (last line shown) > > I bisected this down to: > commit 489fb490dbf8dab0249ad82b56688ae3842a79e8 > Author: Glauber Costa > Date: Tue May 11 12:17:40 2010 -0400 > > x86, paravirt: Add a global synchronization point for pvclock > > One commit before works, smp=1 always works, disabling PVCLOCK works. > Using qemu-kvm-0.12.4 works, too. > Having PVCLOCK enabled and with smp=2 the kernel halts without any > further message. > This is still the case with the lastest tip. > Even pinning both VCPU threads to the same host core show the bug. > The bug triggers on all hosts I tested, an single socket quadcore > Athlon, a dual socket dualcore K8-Opteron and a quad socket 12core > Opteron. > > Please note that this is the guest kernel, the host kernel does not > matter. > > I have no idea (and don't feel like ;-) debugging this, so I hope > someone will find and fix the bug. Does this go away with CONFIG_DEBUG_RODATA=n? If so, it's a known bug in the atomic_*() clobber lists. -- error compiling committee.c: too many arguments to function