Comment 0 for bug 1894772

[Impact]

livemigration of windows 2012 r2 instance with virtio balloon driver
from qemu 2.5(mitaka) to qemu 2.11(queens) is not working properly.

Especially instance keep moving e.g 2.5 -> 2.5 -> 2.11

Then It shows below msg from the 2nd mitaka node.

Migration: [ 94 %]error: internal error: qemu unexpectedly closed the monitor: 2020-09-07T07:45:11.799345Z qemu-system-x86_64: warning: Unknown firmware file in legacy mode: etc/msr_feature_control
2020-09-07T07:45:12.765618Z qemu-system-x86_64: VQ 2 size 0x80 < last_avail_idx 0x1 - used_idx 0x2
2020-09-07T07:45:12.765642Z qemu-system-x86_64: Failed to load virtio-balloon:virtio
2020-09-07T07:45:12.765648Z qemu-system-x86_64: error while loading state for instance 0x0 of device '0000:00:07.0/virtio-balloon'
2020-09-07T07:45:12.766483Z qemu-system-x86_64: load of migration failed: Operation not permitted

[Test Case]

Deploy 2 mitaka-staging machines kvm host
Deploy 1 queens-staging machines kvm host

Deploy windows 2012r2 guest instance with virtio balloon driver on one of the mitaka host

migrate it from mitaka to mitaka (it should be ok )

migrate it from mitaka to queens ( it raises error )

TBD

[Regressions]
TBD

[Others]