From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53131) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WQJAT-00041d-F7 for qemu-devel@nongnu.org; Wed, 19 Mar 2014 12:16:42 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WQJAO-00046V-Gr for qemu-devel@nongnu.org; Wed, 19 Mar 2014 12:16:37 -0400 Received: from static.92.5.9.176.clients.your-server.de ([176.9.5.92]:38695 helo=hallynmail2) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WQJAO-00046O-Aq for qemu-devel@nongnu.org; Wed, 19 Mar 2014 12:16:32 -0400 Date: Wed, 19 Mar 2014 17:16:31 +0100 From: "Serge E. Hallyn" Message-ID: <20140319161631.GA32205@mail.hallyn.com> References: <20140319154247.GA31501@mail.hallyn.com> <5329BCA1.3030303@redhat.com> <20140319155216.GA31857@mail.hallyn.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140319155216.GA31857@mail.hallyn.com> Subject: Re: [Qemu-devel] migrating instances from qemu-kvm to qemu List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Serge E. Hallyn" Cc: Paolo Bonzini , qemu-devel@nongnu.org Quoting Serge E. Hallyn (serge@hallyn.com): > Quoting Paolo Bonzini (pbonzini@redhat.com): > > Il 19/03/2014 16:42, Serge E. Hallyn ha scritto: > > >Hi, > > > > > >at https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1291321 > > >it was found that migrating running vms from a machine with > > >qemu-kvm to one with qemu, migration fails due to some mismatches. > > >The first one we usually hit is > > > > > >Length mismatch: vga.vram: 1000000 in != 800000 > > > > > >while the second one is network card (and I have not gone beyond > > >that). > > > > This is just a different default. Make sure you specify the right > > model on the command line. > > > > >The vga one can be handled on the command line by > > >specifying the -global cirrus-vga.vrammem_mb=8. However that > > >doesn't help with a libvirt migration. > > > > You can patch Ubuntu's QEMU to detect old machine types (pc-1.2 and > > earlier) and give cirrus-vga 16MB memory by default. Migration only > > works with versioned machine types (or between same-version QEMU), > > so it's okay to only do it there. > > > > >I guess this happens at ram_load() unfortunately - is there any > > >good way that this could be detected at incoming migration time > > >and the virtual hardware modified as needed for migration to > > >continue? > > > > It cannot, but the destination can be patched to operate correctly > > for the old machine types, on the assumption that migration from the > > old machine types is always from Ubuntu's qemu-kvm. > > > > Paolo > > Ah, thank you, that assumption should be safe and sounds like a > great idea. Although, some people are using newer qemu with '-M pc-1.0'. So we'd be stopping thing from migrating to support the people coming from qemu-kvm. Hmm. -serge