From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andre Przywara Subject: Re: KVM warning about uncertified CPU for SMP for AMD model 2, stepping 3 Date: Wed, 31 Mar 2010 14:11:57 +0200 Message-ID: <4BB33C0D.9090808@amd.com> References: <20100331024213.GV20695@one.firstfloor.org> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Cc: Jiri Kosina , Ingo Molnar , Avi Kivity , Marcelo Tosatti , Joerg Roedel , linux-kernel@vger.kernel.org, kvm@vger.kernel.org To: Andi Kleen Return-path: In-Reply-To: <20100331024213.GV20695@one.firstfloor.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org Andi Kleen wrote: > On Wed, Mar 31, 2010 at 01:03:02AM +0200, Jiri Kosina wrote: >> Hi, >> >> booting 32bit guest on 32bit host on AMD system gives me the following >> warning when KVM is instructed to boot as SMP: > > I guess these warnings could be just disabled. With nearly everyone > using multi-core these days they are kind of obsolete anyways. Well, the warning refers to an old single-core only CPU model. Most of those were able to run in SMP boards, but only a subset of them was officially certified to do so (Athlon-MP instead of Athlon-XP). To avoid complaints about instability of such systems, the warning was introduced. If you consider these systems still supported, I wouldn't disable this warning, at least the check should be disabled only if the hypervisor CPUID bit is set. But the far better solution is to instruct QEMU/KVM to inject a better CPU model (as it was suggested by some people two weeks ago). I am about to test various guests with respect to their behavior regarding different family/model/stepping settings (one issue is already fixed). If this goes well, I will send out the patch to inject the host's CPUID F/M/S into the guest by default (which has other advantages, but denies migration mostly). BTW.: I encourage people to test their KVM guests with "-cpu host" (on newer QEMUs) and send me any crash logs. Regards, Andre. -- Andre Przywara AMD-Operating System Research Center (OSRC), Dresden, Germany Tel: +49 351 448-3567-12