HyperV_Mon is a free tool for monitoring and diagnosing performance issues with Hyper-V.
After prompting from a user with a lot more processors then the test systems here, I updated the HyperV_Mon tool to handle resizing in general, and to adjust the root partition processor display. This new version is a minor release (1.8.0).
In the works will be a version 2.0 that will look at 2008 R2 with SP1 changes. This should come out in Q1 of next year.
Click on the image to jump to the tools section of the TMurgent website, then scroll down to find the download link.
Screen Shot of HyperV_Mon 1.8