I thought I'd put this out there since I had to try quite a few things to find a solution, and this seems to be (possibly) a recent issue that cropped up in Windows 10 Fall Creators Update.
The host is Windows 10 Pro (Version 10.0.17134 Build 17134) running Hyper-V, guest is Windows 7 Pro x86 (new installation).
The guest operating system acts like it is running in fast-forward. The Windows startup animation runs 3x - 4x as fast as it would be expected to. The cursor on the login screen blinks several times as fast as it should. Mouse animations are several times faster than they should be. The system clock races ahead at approximately one minute every 6-10 seconds.