From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1KdJZ6-0004N1-E3 for qemu-devel@nongnu.org; Wed, 10 Sep 2008 02:52:36 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1KdJZ5-0004Mp-Hq for qemu-devel@nongnu.org; Wed, 10 Sep 2008 02:52:36 -0400 Received: from [199.232.76.173] (port=33155 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1KdJZ5-0004Mm-ED for qemu-devel@nongnu.org; Wed, 10 Sep 2008 02:52:35 -0400 Received: from mx20.gnu.org ([199.232.41.8]:36839) by monty-python.gnu.org with esmtps (TLS-1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1KdJZ5-0005yE-1C for qemu-devel@nongnu.org; Wed, 10 Sep 2008 02:52:35 -0400 Received: from il.qumranet.com ([212.179.150.194]) by mx20.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1KdJZ2-00014B-Bq for qemu-devel@nongnu.org; Wed, 10 Sep 2008 02:52:32 -0400 Message-ID: <48C76EB1.6040906@qumranet.com> Date: Wed, 10 Sep 2008 09:52:33 +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> In-Reply-To: <1220989802-13706-3-git-send-email-aliguori@us.ibm.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: qemu-devel@nongnu.org Cc: Chris Wright , Uri Lublin , Anthony Liguori , kvm@vger.kernel.org Anthony Liguori wrote: > Live migration happens in the background, but it is useful to make the monitor > command appear as if it's blocking. This allows a management tool to > immediately know when the live migration has completed without having to poll > the migration status. > > This patch allows the monitor to be suspended from a monitor callback which > will prevent new monitor commands from being executed. > > 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. This both reduces the functionality and complicates management applications. IMO migration should have asynchronous notification (and no, I don't think multiple monitors is the correct solution). -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.