CPU reservation and affinity using taskset and isolcpus kernel parameter with JVM?

We need for the JVM to reserve a set number of CPUs. Following my research we can use taskset along with the kernel parameter isolcpus= so that no other process uses this CPU. A few questions arise: - does the process need to be started with taskset? - does the reservation means that the process can only run on that CPU and if there are resources problems it can expand to the other CPUs?