From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tomasz Chmielewski Subject: AMD-Intel guest migration and CPUs without NX Date: Tue, 24 Mar 2009 11:48:47 +0100 Message-ID: <49C8BA8F.8000008@wpkg.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit To: "kvm@vger.kernel.org" Return-path: Received: from mx03.syneticon.net ([78.111.66.105]:45499 "EHLO mx03.syneticon.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756566AbZCXKsx (ORCPT ); Tue, 24 Mar 2009 06:48:53 -0400 Received: from localhost (filter1.syneticon.net [192.168.113.83]) by mx03.syneticon.net (Postfix) with ESMTP id 0136136149 for ; Tue, 24 Mar 2009 11:48:51 +0100 (CET) Received: from mx03.syneticon.net ([192.168.113.84]) by localhost (mx03.syneticon.net [192.168.113.83]) (amavisd-new, port 10025) with ESMTP id arPlWsNeyOHB for ; Tue, 24 Mar 2009 11:48:48 +0100 (CET) Received: from [192.168.10.145] (koln-4db483fa.pool.einsundeins.de [77.180.131.250]) by mx03.syneticon.net (Postfix) with ESMTPSA for ; Tue, 24 Mar 2009 11:48:48 +0100 (CET) Sender: kvm-owner@vger.kernel.org List-ID: I have an older Intel CPU which doesn't support NX (/proc/cpuinfo - below). Is it safe to migrate guests running on newer CPUs to this older CPU? I made some simple tests and migration works, but I'm not sure if the guests will be stable after such migration. I'm also a bit confused a bit over what the documentation says: According to http://www.linux-kvm.org/page/Migration: There are some older Intel processors which don't support NX (or XD), which may cause problems in a cluster which includes NX-supporting hosts. We may add a feature to hide NX if this proves to be a problem in actual deployments. So the above says I may have some problems. On the other hand, FAQ below seems to indicate that migration on 64 bit hosts should be fine (even when they don't support NX?), only 32 bit hosts may have problems: http://www.linux-kvm.org/page/FAQ Yes. There may be issues on 32-bit Intel hosts which don't support NX (or XD), but for 64-bit hosts back and forth migration should work well. Migration of 32-bit guests should work between 32-bit hosts and 64-bit hosts. processor : 1 vendor_id : GenuineIntel cpu family : 6 model : 15 model name : Intel(R) Xeon(R) CPU 3050 @ 2.13GHz stepping : 6 cpu MHz : 2133.410 cache size : 2048 KB physical id : 0 siblings : 2 core id : 1 cpu cores : 2 fpu : yes fpu_exception : yes cpuid level : 10 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall lm constant_tsc arch_perfmon pebs bts rep_good pni monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr lahf_lm bogomips : 4266.87 clflush size : 64 cache_alignment : 64 address sizes : 36 bits physical, 48 bits virtual power management: -- Tomasz Chmielewski http://wpkg.org