Hi developers,

I have questions about balloon-change or control-error event:

1. What's the meaning of these events

2. When do the events occur?

The comments of their callbacks don't mention that(https://gitlab.com/libvirt/libvirt/-/blob/master/include/libvirt/libvirt-domain.h#L4130 https://gitlab.com/libvirt/libvirt/-/blob/master/include/libvirt/libvirt-domain.h#L3736)