Active Directory Time Synchronization

I currently am in the process of upgrading my Active Directory Domain Controllers from 2008 R2 to 2012 R2.

I have 2 domains, 1 parent and 1 child. Currently my FSMO role holder in the parent domain is syncing time with an external time source and is a physical server.

I know when I set it up in 2009 it was strongly recommended that the time server be a physical server.

Is this still the Microsoft recommendation or is it OK to setup the time server on a virtual Hyper-V machine?

Thanks,

Eddie