From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35909) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YzQQg-00051o-AB for qemu-devel@nongnu.org; Mon, 01 Jun 2015 10:11:03 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YzQQc-0002HQ-2L for qemu-devel@nongnu.org; Mon, 01 Jun 2015 10:11:02 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41768) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YzQQb-0002HK-SN for qemu-devel@nongnu.org; Mon, 01 Jun 2015 10:10:57 -0400 Date: Mon, 1 Jun 2015 16:10:54 +0200 From: "Michael S. Tsirkin" Message-ID: <20150601141054.GA11304@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Subject: [Qemu-devel] fw cfg files cross-version migration races List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: somlo@cmu.edu, kraxel@redhat.com Hi all, At the moment we have devices adding and removing fw cfg file entries. One problem is that this makes the contents of fw cfg depend on order of device initialization. Since the fw cfg file list is not migrated, this means that guest will break if it is migrated between qemu versions which generate the list diferently, and if migration triggers while guest happens to read fw cfg. As there are plans to extend the use of fw cfg, I think it's important to fix this issue sooner rather than later. Ideas: - sort fw cfg files by name before exposing them to guest - keep doing what we did for compat machine types, hope that things don't break too often More ideas? Comments? Anyone wants to try implementing this? -- MST