From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [Qemu-devel] [PATCH 2/10] Allow the monitor to be suspended during non-blocking op Date: Wed, 10 Sep 2008 14:11:56 +0300 Message-ID: <48C7AB7C.30407@qumranet.com> References: <1220989802-13706-1-git-send-email-aliguori@us.ibm.com> <1220989802-13706-3-git-send-email-aliguori@us.ibm.com> <48C76EB1.6040906@qumranet.com> <20080910100520.GE2662@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: qemu-devel@nongnu.org, Chris Wright , Uri Lublin , Anthony Liguori , kvm@vger.kernel.org To: "Daniel P. Berrange" Return-path: Received: from il.qumranet.com ([212.179.150.194]:59739 "EHLO il.qumranet.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751131AbYIJLL5 (ORCPT ); Wed, 10 Sep 2008 07:11:57 -0400 In-Reply-To: <20080910100520.GE2662@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Daniel P. Berrange wrote: >> This means that migration is no longer transparent. While migration is >> going on, you can't change the cdrom media, look at cpu registers, or do >> anything that requires the monitor. >> > > Changing cdrom media while in the middle of migration sounds like a rather > troubleprone thing todo - you'd need to change the media in both active > QEMU instances at the same time to be safe. Or rather, such state should be part of the migration. There's the question of whether to transform the path on the target, but "which media is in the drive" is part of the hardware state. (logically we would copy all of the data of all block devices, but that's not very practical, so we assume shared storage). What other commands are unsafe during migration? I exclude host device assignment which is obviously migration unfriendly. -- error compiling committee.c: too many arguments to function From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1KdNc7-0002QX-VY for qemu-devel@nongnu.org; Wed, 10 Sep 2008 07:12:00 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1KdNc6-0002Od-I2 for qemu-devel@nongnu.org; Wed, 10 Sep 2008 07:11:58 -0400 Received: from [199.232.76.173] (port=52114 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1KdNc5-0002OE-T2 for qemu-devel@nongnu.org; Wed, 10 Sep 2008 07:11:57 -0400 Received: from il.qumranet.com ([212.179.150.194]:59740) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1KdNc6-0005z9-0A for qemu-devel@nongnu.org; Wed, 10 Sep 2008 07:11:58 -0400 Message-ID: <48C7AB7C.30407@qumranet.com> Date: Wed, 10 Sep 2008 14:11:56 +0300 From: Avi Kivity MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH 2/10] Allow the monitor to be suspended during non-blocking op References: <1220989802-13706-1-git-send-email-aliguori@us.ibm.com> <1220989802-13706-3-git-send-email-aliguori@us.ibm.com> <48C76EB1.6040906@qumranet.com> <20080910100520.GE2662@redhat.com> In-Reply-To: <20080910100520.GE2662@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Daniel P. Berrange" Cc: Chris Wright , Uri Lublin , Anthony Liguori , qemu-devel@nongnu.org, kvm@vger.kernel.org Daniel P. Berrange wrote: >> This means that migration is no longer transparent. While migration is >> going on, you can't change the cdrom media, look at cpu registers, or do >> anything that requires the monitor. >> > > Changing cdrom media while in the middle of migration sounds like a rather > troubleprone thing todo - you'd need to change the media in both active > QEMU instances at the same time to be safe. Or rather, such state should be part of the migration. There's the question of whether to transform the path on the target, but "which media is in the drive" is part of the hardware state. (logically we would copy all of the data of all block devices, but that's not very practical, so we assume shared storage). What other commands are unsafe during migration? I exclude host device assignment which is obviously migration unfriendly. -- error compiling committee.c: too many arguments to function