Quoting Cole Robinson (crobi...@redhat.com): > On 03/19/2014 12:16 PM, Serge E. Hallyn wrote: > > Quoting Serge E. Hallyn (se...@hallyn.com): > >> Quoting Paolo Bonzini (pbonz...@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. > > > > FWIW, we've carried a patch like this in Fedora 18, 19, and 20: > > http://pkgs.fedoraproject.org/cgit/qemu.git/tree/0001-Fix-migration-from-qemu-kvm.patch?h=f20 > > As you say, it breaks incoming migration from stock qemu.git. But we never > shipped qemu.git prior to F18 (well, not in any timeframe that matters here), > so back compat wasn't a real concern. > > For Fedora 21 we are dropping this patch, since there's been enough releases > for the people to transition: > > http://blog.wikichoon.com/2013/12/kvm-migration-from-fedora-17-to-fedora.html
Thanks, Cole. I notice it doesn't do anything for -vga cirrus - is that just bc in general fedora users tend to use -vga qxl? -serge