Comment 2 for bug 1559643

After commenting out the first two line 2 lines:
**********
# On Hyper-V and Xen Virtual Machines we want to add memory and cpus as soon as they appear
#ATTR{[dmi/id]sys_vendor}=="Microsoft Corporation", ATTR{[dmi/id]product_name}=="Virtual Machine", GOTO="vm_hotadd_apply"
#ATTR{[dmi/id]sys_vendor}=="Xen", GOTO="vm_hotadd_apply"
**********
in file
/lib/udev/rules.d/40-vm-hotadd.rules

and rebooting the system in working normally again.