How to activate a windows 2008 virtual machine that is running on a host with windows 2012 datacenter under Hyper-V?

Question

Hyper-V

Good day to all.
There was a task to raise a windows 2008 std virtual machine, on a windows 2012 DC server.
In Google I found information that under the datacenter you can run any VM under the DC license. All the manuals that I found described guest activation via automatic virtual machine activation (AVMA), and it is only for 2012 guests.
Key for windows 2012 DC - retail.
Q: Is it possible to activate a non-2012 guest on a 2012 DC at no extra cost? If so, how?
Thank you.
ps For the first time I encountered windows server, and even more so with its licensing, so please do not kick with your feet

Answer 1

AVMA keys are here