Why Does it introduce unpredictable noise to the counter values observed by the user?

[omerguzelelectronicguy]

This is not an issue but I couldn't find where to discuss it. I have a question actually.

Why noise to the counter values observed by the user is a problem? Can't the user prevent noise when core switching thread or handling traps by storing the counter while switching?

The counters can be stored similarly to how the architectural state is stored, and then loaded upon returning from a handled trap.