[Qemu-devel] [PATCH RFC 0/1] virtio: fix config_vector migration issues

[Cornelia Huck]

We've noticed a problem when migrating guests using virtio-ccw: the
ballooner will stop working after migration. Turns out that the
config_vector field was not migrated and still remained at its initial
value on the target system - therefore no working config changed
notifications.

config_vector is located in VirtIODevice, so we assumed core would take
care of migrating the value; virtio-pci does it itself.

We cannot simply add new values to the virtio stream, so I introduced
a new, optional, subsection only to be included when config_vector has
actually been changed from its initial value. Not wanting to introduce
problems with migrating virtio-pci based machines, I've introduced a
callback for virtio-pci to override creation of this subsection.

Migration for virtio-ccw based machines seems to be fixed with this one
(ballooner continues to work on the target system), but I'd like
confirmation whether this setup makes sense for virtio-pci as well.

Cornelia Huck (1):
  virtio: migrate config_vector

 hw/virtio/virtio-pci.c         | 14 ++++++++++++++
 hw/virtio/virtio.c             | 25 +++++++++++++++++++++++++
 include/hw/virtio/virtio-bus.h |  5 +++++
 3 files changed, 44 insertions(+)

-- 
2.1.4