From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: tainted Linux kernel in default SMP QEMU/KVM guests Date: Fri, 19 Mar 2010 13:58:33 +0100 Message-ID: <4BA374F9.9040008@redhat.com> References: <4BA36B06.5060002@amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: QEMU devel , KVM list To: Andre Przywara Return-path: Received: from mail-pw0-f46.google.com ([209.85.160.46]:59126 "EHLO mail-pw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751838Ab0CSM6k (ORCPT ); Fri, 19 Mar 2010 08:58:40 -0400 Received: by pwi5 with SMTP id 5so1203224pwi.19 for ; Fri, 19 Mar 2010 05:58:39 -0700 (PDT) In-Reply-To: <4BA36B06.5060002@amd.com> Sender: kvm-owner@vger.kernel.org List-ID: > 1) Change the default CPUID bits from 6/2/3 to 6/6/1, this passes the > Linux kernel check. But I am not sure if that would introduce > regressions, since some OSes apply quirks if they detect certain models > (like we had with the sysenter issue in the past) > > 2) Only change the CPUID bits to 6/6/1 if we use SMP. Still has the > above drawback, but would be limited to SMP guests only. > > 3) Set kvm64/kvm32 as the default CPU model if KVM is enabled. This > would limit the report and taint to TCG, where SMP is rarely used. > Additionally less people (if any) use it for production systems. > > 4) Make the Linux' kernel quirk dependent on the missing hypervisor bit. > I don't think this will be accepted easily upstream (and I don't want to > support Ingo's recent ideas ;-), also this would not fix older kernels. > > I can easily provide patches for all solutions, but I'd like to get > advice from people on which one to pursue. Doing (3) seems the most sensible thing to do, and it does not prevent doing (1) later on for TCG only. Paolo From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1Nsbmk-0001mK-Ms for qemu-devel@nongnu.org; Fri, 19 Mar 2010 08:58:42 -0400 Received: from [199.232.76.173] (port=52533 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Nsbmk-0001m0-Cb for qemu-devel@nongnu.org; Fri, 19 Mar 2010 08:58:42 -0400 Received: from Debian-exim by monty-python.gnu.org with spam-scanned (Exim 4.60) (envelope-from ) id 1Nsbmj-0001CI-JU for qemu-devel@nongnu.org; Fri, 19 Mar 2010 08:58:42 -0400 Received: from mail-pw0-f45.google.com ([209.85.160.45]:58110) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1Nsbmj-0001C6-3w for qemu-devel@nongnu.org; Fri, 19 Mar 2010 08:58:41 -0400 Received: by pwi9 with SMTP id 9so2159390pwi.4 for ; Fri, 19 Mar 2010 05:58:39 -0700 (PDT) Sender: Paolo Bonzini Message-ID: <4BA374F9.9040008@redhat.com> Date: Fri, 19 Mar 2010 13:58:33 +0100 From: Paolo Bonzini MIME-Version: 1.0 References: <4BA36B06.5060002@amd.com> In-Reply-To: <4BA36B06.5060002@amd.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] Re: tainted Linux kernel in default SMP QEMU/KVM guests List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Andre Przywara Cc: QEMU devel , KVM list > 1) Change the default CPUID bits from 6/2/3 to 6/6/1, this passes the > Linux kernel check. But I am not sure if that would introduce > regressions, since some OSes apply quirks if they detect certain models > (like we had with the sysenter issue in the past) > > 2) Only change the CPUID bits to 6/6/1 if we use SMP. Still has the > above drawback, but would be limited to SMP guests only. > > 3) Set kvm64/kvm32 as the default CPU model if KVM is enabled. This > would limit the report and taint to TCG, where SMP is rarely used. > Additionally less people (if any) use it for production systems. > > 4) Make the Linux' kernel quirk dependent on the missing hypervisor bit. > I don't think this will be accepted easily upstream (and I don't want to > support Ingo's recent ideas ;-), also this would not fix older kernels. > > I can easily provide patches for all solutions, but I'd like to get > advice from people on which one to pursue. Doing (3) seems the most sensible thing to do, and it does not prevent doing (1) later on for TCG only. Paolo