From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH v4 2/3] target-i386: add migration support for Intel LMCE Date: Thu, 16 Jun 2016 19:40:20 +0200 Message-ID: <7e106359-c7e3-93b5-4cca-d669c26c873e@redhat.com> References: <20160616060621.30422-1-haozhong.zhang@intel.com> <20160616060621.30422-3-haozhong.zhang@intel.com> <1d2312d2-4dd3-6a73-d0d7-84b4e8c749e2@redhat.com> <20160616102918.7geiaomeitldj7jy@hz-desktop> <20160616105529.dpmjjeqsdnf5cdnm@hz-desktop> <20160616173624.GO18662@thinpad.lan.raisama.net> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit To: Eduardo Habkost , qemu-devel@nongnu.org, Richard Henderson , "Michael S . Tsirkin" , Marcelo Tosatti , kvm@vger.kernel.org, Boris Petkov , Tony Luck , Andi Kleen , rkrcmar@redhat.com, Ashok Raj Return-path: Received: from mx1.redhat.com ([209.132.183.28]:39332 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755064AbcFPRk0 (ORCPT ); Thu, 16 Jun 2016 13:40:26 -0400 In-Reply-To: <20160616173624.GO18662@thinpad.lan.raisama.net> Sender: kvm-owner@vger.kernel.org List-ID: On 16/06/2016 19:36, Eduardo Habkost wrote: >> > >> > Eduardo said nice for this part in previous version [1], so we may wait >> > for his comments? >> > >> > [1] http://lists.nongnu.org/archive/html/qemu-devel/2016-06/msg01992.html > I agree we don't need this check, but I still believe it is a > nice thing to have. > > In addition to detecting user errors, they don't hurt and are > useful for things like "-cpu host", that don't guarantee > live-migration compatibility but still allow migration if you > ensure host capabilities are the same on both sides. On the other hand we don't check for this on any other property, either CPU or device, do we? Considering "lmce=on" always breaks on an old kernel (i.e. there's no need for an explicit ",enforce" on the -cpu flag), I think it's unnecessary and makes things inconsistent. > (I was going to suggest enabling lmce automatically on "-cpu > host" as a follow-up patch, BTW.) Interesting. Technically it comes from the host kernel, not from the host CPU. But it does sounds like a good idea; -cpu host pretty much implies the same kernel (in addition to the same processor) on both sides of the migration. Paolo From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48508) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bDbHK-0006Xb-2F for qemu-devel@nongnu.org; Thu, 16 Jun 2016 13:40:31 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bDbHG-0005Lq-Pv for qemu-devel@nongnu.org; Thu, 16 Jun 2016 13:40:30 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46854) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bDbHG-0005Li-K2 for qemu-devel@nongnu.org; Thu, 16 Jun 2016 13:40:26 -0400 References: <20160616060621.30422-1-haozhong.zhang@intel.com> <20160616060621.30422-3-haozhong.zhang@intel.com> <1d2312d2-4dd3-6a73-d0d7-84b4e8c749e2@redhat.com> <20160616102918.7geiaomeitldj7jy@hz-desktop> <20160616105529.dpmjjeqsdnf5cdnm@hz-desktop> <20160616173624.GO18662@thinpad.lan.raisama.net> From: Paolo Bonzini Message-ID: <7e106359-c7e3-93b5-4cca-d669c26c873e@redhat.com> Date: Thu, 16 Jun 2016 19:40:20 +0200 MIME-Version: 1.0 In-Reply-To: <20160616173624.GO18662@thinpad.lan.raisama.net> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v4 2/3] target-i386: add migration support for Intel LMCE List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eduardo Habkost , qemu-devel@nongnu.org, Richard Henderson , "Michael S . Tsirkin" , Marcelo Tosatti , kvm@vger.kernel.org, Boris Petkov , Tony Luck , Andi Kleen , rkrcmar@redhat.com, Ashok Raj On 16/06/2016 19:36, Eduardo Habkost wrote: >> > >> > Eduardo said nice for this part in previous version [1], so we may wait >> > for his comments? >> > >> > [1] http://lists.nongnu.org/archive/html/qemu-devel/2016-06/msg01992.html > I agree we don't need this check, but I still believe it is a > nice thing to have. > > In addition to detecting user errors, they don't hurt and are > useful for things like "-cpu host", that don't guarantee > live-migration compatibility but still allow migration if you > ensure host capabilities are the same on both sides. On the other hand we don't check for this on any other property, either CPU or device, do we? Considering "lmce=on" always breaks on an old kernel (i.e. there's no need for an explicit ",enforce" on the -cpu flag), I think it's unnecessary and makes things inconsistent. > (I was going to suggest enabling lmce automatically on "-cpu > host" as a follow-up patch, BTW.) Interesting. Technically it comes from the host kernel, not from the host CPU. But it does sounds like a good idea; -cpu host pretty much implies the same kernel (in addition to the same processor) on both sides of the migration. Paolo