The name SMP already gives it away:
It is MP, as in multiprocessor. The system consists of multiple identical CPUs.
It is symmetric. All processors have an identical view of the system. They all have the same capabilities. For example, they have identical access to any location in memory as well as to any I/O device.
Everything else is single. It has a single memory system, a single copy of the operating system, a single Run Queue.
Figure 15.3 captures the SMP story.
Unless your application code bends over backwards, threads have no affinity to any particular CPU. The same thread may execute ...