The rule is oddly written, and may conflict with another similar one that already exist in the distro (hence may not be useful to begin with). The modern generic rule for doing vCPU hotplug is, which would be preferable to the current z10-xen-vcpu-hotplug.rules. ACTION=="add", SUBSYSTEM=="cpu", ATTR{online}=="0", ATTR{online}="1"

on my side importing backup config in a new XO installation worked (Using Webinterface). (i build from sources). Only thing wich bugs are backup jobs - i had to open and resubmit every backup job to get them work... br Mark