Q: When I perform an upgrade within a Hyper-V virtual machine (VM) to Windows Server 2012 R2, I receive a warning that Microsoft Hyper-V S3 Cap may not work after the upgrade. Is this a problem?

A: No, this can be ignored. The S3 Trio 765 emulated device is now so old, the driver is no longer included. This isn't a problem as Windows Server 2012 R2 includes all the drivers for Hyper-V built-in. Ignore the error and the upgrade will complete successfully.