UPDATE: This issue has since been resolved.
KB4056894 has the potential to break Windows 2008 R2 Hyper-V hosts. The server itself comes up just fine, however the VMs get stuck in restoring mode at 0%. This poses a huge problem. So far this has only happened to one of our host servers with the rest coming up normally (Server 2012, Server 2012 R2, and one other Server 2008 R2 host). So how do you fix this issue? So long as the host comes up, simply uninstall the offending patch and restart. When we did this, the VMs immediately booted back up.
It is interesting to note that at one point Microsoft pulled these patches, but has obviously made them available again. Thankfully, the only issue we have had affected only this one server (so far) out of several hosts and over a hundred VMs. Of course, now Intel recommends that you skip those patches completely.