Quoting Cole Robinson (crobi...@redhat.com): > On 03/21/2014 01:00 PM, Serge E. Hallyn wrote: > > 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? > > > > Line 149 of the patch changes the cirrus-vga default memory for old machine > types, seems to fix things in my testing.
Hh, hm, how did i miss that. thanks, -serge
