Recently, Mike Sterling posted about the availability of Linux Integration Components for Hyper-V here:
http://blogs.msdn.com/mikester/archive/2008/09/10/linux-integration-components-now-posted.aspx
The final release is localized in 12 languages and will provide the following features:
Driver support for synthetic devices: The Linux integration components include support for both the synthetic network controller and synthetic storage controller that have been developed specifically for Hyper-V. These components take advantage of the new high-speed bus, VMBus, which was developed for Hyper-V.
Hypercall adapter: The Hypercall adapter is a thin layer of software that translates the Xen-specific virtualization function calls from a Xen-enabled Linux kernel to Microsoft Hyper-V hypercalls. This results in improved performance for the Linux virtual machine.
Fastpath Boot Support: Boot devices now take advantage of the storage VSC to provide enhanced performance.
To download Linux Integration Components for Hyper-V you should visit the following addres at Microsoft Connect Site:
https://connect.microsoft.com/Downloads/Downloads.aspx?SiteID=495
If you have not access to the project you should search it on the Connection Directory, or, if you previously declined the project you can ask the Connect HelpDesk to give you access again trough this page and selecting "Program Help".
Also available at http://www.andreatedeschi.com/2008/09/linux-integration-components-for-hyper.html