From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:53621) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S6jbL-0005u7-H2 for qemu-devel@nongnu.org; Sun, 11 Mar 2012 10:18:43 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1S6jbJ-0006Pa-QC for qemu-devel@nongnu.org; Sun, 11 Mar 2012 10:18:23 -0400 Received: from mail-yw0-f45.google.com ([209.85.213.45]:59303) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S6jbJ-0006PR-Lp for qemu-devel@nongnu.org; Sun, 11 Mar 2012 10:18:21 -0400 Received: by yhoo21 with SMTP id o21so2235242yho.4 for ; Sun, 11 Mar 2012 07:18:20 -0700 (PDT) Message-ID: <4F5CB429.4000907@codemonkey.ws> Date: Sun, 11 Mar 2012 09:18:17 -0500 From: Anthony Liguori MIME-Version: 1.0 References: <4F5CA590.1000605@redhat.com> In-Reply-To: <4F5CA590.1000605@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] seamless migration with spice List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Yonit Halperin Cc: qemu-devel , "spice-devel@freedesktop.org" , Gerd Hoffmann On 03/11/2012 08:16 AM, Yonit Halperin wrote: > Hi, > > We would like to implement seamless migration for Spice, i.e., keeping the > currently opened spice client session valid after migration. > Today, the spice client establishes the connection to the destination before > migration starts, and when migration completes, the client's session is moved to > the destination, but all the session data is being reset. > > We face 2 main challenges when coming to implement seamless migration: > > (1) Spice client must establish the connection to the destination before the > spice password expires. However, during migration, qemu main loop is not > processed, and when migration completes, the password might have already expired. > > Today we solve this by the async command client_migrate_info, which is expected > to be called before migration starts. The command is completed > once spice client has connected to the destination (or a timeout). > > Since async monitor commands are no longer supported, we are looking for a new > solution. We need to fix async monitor commands. Luiz sent a note our to qemu-devel recently on this topic. I'm not sure we'll get there for 1.1 but if we do a 3 month release cycle for 1.2, then that's a pretty reasonable target IMHO. Regards, Anthony Liguori > The straightforward solution would be to process the main loop on the > destination side during migration. > > (2) In order to restore the source-client spice session in the destination, we > need to pass data from the source to the destination. > Example for such data: in flight copy paste data, in flight usb data > We want to pass the data from the source spice server to the destination, via > Spice client. This introduces a possible race: after migration completes, the > source qemu can be killed before the spice-server completes transferring the > migration data to the client. > > Possible solutions: > - Have an async migration state notifiers. The migration state will change after > all the notifiers complete callbacks are called. > - libvirt will wait for qmp event corresponding to spice completing its > migration, and only then will kill the source qemu process. > > Any thoughts? > > Thanks, > Yonit. >