Is there a good place to learn about cpu pinning and the various settings?

I've built a test VM and am trying to understand

- I've given it 2 cpus, 4 cores each, 1 thread per core.

- The VM is pinned to a specific host with passthrough cpu enabled

- numa pinning, first 4 cores on physical socket 1 and the next 4 on physical socket 2 

- The host has two sockets each with 20 core cpus

I would expect to see a load applied on 8 of the 40 cores on the host during testing. Instead it seems like 32 of 40 cores are working at 100%.  What are the effects of this on the performance of the vm?