[Bug 1291321] Re: migration fails between 12.04 Precise and 14.04 Trusty

[Alex Bligh]

This is pretty annoying. In a situation where you have many customer VMs
running on 12.04, and want to migrate them to a host running 14.04 (so
you can do a rolling OS upgrade), I'm afraid "shut down all your
customer VMs and restart" isn't really an option for obvious reasons.

Equally, installing two versions of qemu, or custom versions of qemu is
not really an option.

In my situation I'm not using virsh / libvirt, so adding '-machine
pc-1.0 -global cirrus-vga.vgamem_mb=10' or similar would be a reasonable
fix; when the VM is eventually rebooted, I can reboot without that, and
the hardware will appear to be upgraded (not great, but ok).

However, this doesn't work as (as far as I can tell) there is no way to get past:
'Length mismatch: 0000:00:03.0/virtio-net-pci.rom: 10000 in != 20000'

through command-line skulduggery.

What it seems to me one should do is define a pc-1.0-precise machine
type (which is obviously not going to be used by anyone using raring
etc.), and use this solely for incoming migrations. I'd produce the
patch myself save I've not yet discovered where the relevant tweak for
changing virtio-net-pci.rom size is.

If I find it (I've contributed to qemu before) would you take this as an
SRU?

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https://bugs.launchpad.net/bugs/1291321

Title:
  migration fails between 12.04 Precise and 14.04 Trusty

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