From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55006) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aY7bC-0005yD-3n for qemu-devel@nongnu.org; Tue, 23 Feb 2016 02:41:34 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aY7b8-0007zu-T1 for qemu-devel@nongnu.org; Tue, 23 Feb 2016 02:41:34 -0500 Received: from mx1.redhat.com ([209.132.183.28]:55573) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aY7b8-0007zq-O0 for qemu-devel@nongnu.org; Tue, 23 Feb 2016 02:41:30 -0500 Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) by mx1.redhat.com (Postfix) with ESMTPS id 4F1AE65415 for ; Tue, 23 Feb 2016 07:41:30 +0000 (UTC) Date: Tue, 23 Feb 2016 13:11:21 +0530 From: Amit Shah Message-ID: <20160223074121.GF10967@grmbl.mre> References: <1483e0d74dcfd183ff46dd63cc57e1fe8b775bf8.1454680535.git.amit.shah@redhat.com> <56BC86C6.6060103@redhat.com> <20160222123940.GD10967@grmbl.mre> <56CC0422.3010005@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56CC0422.3010005@redhat.com> Subject: Re: [Qemu-devel] [PULL 8/9] static checker: e1000-82540em got aliased to e1000 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jason Wang Cc: Paolo Bonzini , Juan Quintela , qemu list , "Dr. David Alan Gilbert" On (Tue) 23 Feb 2016 [15:02:58], Jason Wang wrote: > >> This means that 2.5 cannot migrate 2.4 virtual machines, right? Is that > >> something we want to rectify in 2.6 by making e1000-82540em an alias of > >> e1000 (instead of the other way round)? > > You're right; I misread it. With that commit (8304402033): > > > > 2.4 with e1000-82540em will not migrate to 2.5 with e1000-82540em. > > > > This is despite they're aliased (so the cmdline is backward > > compatible), but the migration device name actually changed. > > > > Of course, 2.5->2.4 will also not work. > > > > Since 2.4 emits 'e1000-82540em' as the device name in the migration > > stream, and 2.5 emits just 'e1000', we have two different names for > > the same device in two versions. > > > > To fix this, we'll need a hack on the dest side to allow e1000 and > > e1000-82540em in the migration stream for the device, and this can be > > done for 2.6 and 2.5.stable. > > > > Jason, can you attempt this? > > > Sure, but just need to understand the "problem". If I understand this > correctly, the issue only happen for JSON description at the end of > migration stream, and it won't break migration in fact? No, this does break migration. The stream contained 'e1000-82540em' as the section header for the device earlier. It now only has 'e1000'. So a newer qemu will only accept 'e1000', but not 'e1000-82540em' (from an older release). Amit