How does a Hypervisor distinguish multiple VMs running on it and isolate them from the underlying h/w?

Question

How does a Hypervisor distinguish multiple VMs running on it and isolate them from the underlying h/w? eg if there is a system call from with in a guest OS, how does the HV know it belongs to a specific guest OS? Not much details about lower details of HV operation.

Answer 1

A normal system call in a guest is processed by the guest OS without intervention of the hypervisor.

However, when the guest does cause a trap to the hypervisor (not a system call, but some other operation that requires hypervisor service), the hypervisor knows which guest it is because it knows which guest it scheduled on that CPU.