From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: Linux in VirtualPC in KVM fails Date: Fri, 09 Jan 2009 21:34:49 +0200 Message-ID: <4967A6D9.9090309@redhat.com> References: <4967708E.2060907@suse.de> <49678E6E.4020306@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Kevin Wolf , kvm@vger.kernel.org To: Alexander Graf Return-path: Received: from mx2.redhat.com ([66.187.237.31]:54251 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751900AbZAITel (ORCPT ); Fri, 9 Jan 2009 14:34:41 -0500 In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: Alexander Graf wrote: >> We're in a nice compatibility mess. We can't just switch paravirt >> detection methods since that will break older guests _and_ older >> hosts on non-nested virtualization (which is the common case). > > Shouldn't it be ok to push patches to linux-stable to use the CPUID > and MSR information and simply not expose the CPUID identification in > newer KVM versions? That way older guests on newer KVM don't use KVM > paravirt (which should still be ok), but everything else runs as > smoothly as possible. No. It's a regression (esp. kvmclock). It's perfectly legitimate to say we support Virtual PC beginning some kvm version (and to supply the command line workaround for older versions). But we shouldn't knowingly break existing setups. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.