The following features are included in the 2.1 release:
Driver support for synthetic devices: Linux Integration Services supports the synthetic network controller and the synthetic storage controller that were developed specifically for Hyper-V.
Fastpath Boot Support for Hyper-V: Boot devices take advantage of the block Virtualization Service Client (VSC) to provide enhanced performance.
Timesync: The clock inside the virtual machine will remain synchronized with the clock on the host.
Integrated Shutdown: Virtual machines running Linux can be gracefully shut down from either Hyper-V Manager or System Center Virtual Machine Manager.
Symmetric Multi-Processing (SMP) Support: Supported Linux distributions can use up to 4 virtual processors (VP) per virtual machine.
Heartbeat: Allows the host to detect whether the guest is running and responsive.
Pluggable Time Source: A pluggable clock source module is included to provide a more accurate time source to the guest.
This version of the integration services for Hyper-V supports Novell SUSE Linux Enterprise Server 10 SP3, SUSE Linux Enterprise Server 11, and Red Hat Enterprise Linux 5.2 / 5.3 / 5.4 / 5.5.
Read more: Microsoft Virtualization Team Blog