Autodeflate can be enabled/disabled for memballon device
of model 'virtio'.
xml:
<devices>
<memballoon model='virtio' autodeflate='on'/>
</devices>
qemu:
qemu -device virtio-balloon-pci,...,deflate-on-oom=on
Autodeflate cannot be enabled/disabled for running domain.
Dmitry Andreev