Last week, Red Hat announced the general availability of Red Hat Enterprise Linux 5.9 (details here:http://www.redhat.com/about/news/press-archive/2013/1/red-hat-announces-general-availability-of-red-hat-enterprise-linux-5-9). Amongst the various improvements is built-in support for Hyper-V:
New Virtualization Capabilities and Flexibility in Multi-vendor Environments. Red Hat Enterprise Linux 5.9 enhances the operating system’s usability in multi-vendor environments by introducing Microsoft Hyper-V drivers for improved performance. This enhances the usability of Red Hat Enterprise Linux 5 for guests in heterogeneous, multi-vendor virtualized environments and provides improved flexibility and interoperability for enterprises.
This is great news if you use Red Hat Linux as your standard Linux distribution.