If you are running a Hyper-V 2012 r2 host with guest VMs that are of earlier versions of windows you will notice a couple of unknown devices in the device manager, even after installing the hyper-v integration services on the guest. When I first noticed this I thought maybe some driver didn’t install correctly, but after doing a little digging i found a Microsoft Knowledge Base article dealing with this very subject kb2925727. The article states “On a Windows Server 2012 R2 Datacenter Hyper-V host, you may see 2 unknown device under Other Devices in device manager of any virtual machine running operating systems earlier than Windows Server 2012 R2. These Virtual Devices (VDev) are provided for Automatic Virtual Machine Activation (AVMA) to communicate with the host. AVMA is only supported on virtual machines running Windows Server 2012 R2 or later versions of operating systems. The unknown devices are harmless and can be ignored. ” So there you go.