1. A method of providing a plurality of virtual processors, which is carried out by a physical computer including a physical processor and a memory, comprising the steps of: generating, by a first virtual machine manager, a first virtual processor; generating, by a second virtual machine manager executed on the first virtual processor, a second virtual processor; executing, by the second virtual processor, a user program; receiving, by the first virtual machine manager, a call for the first virtual machine manager from the physical processor; analyzing, by the first virtual machine manager, a cause of the call for the first virtual machine manager; managing, by the first virtual machine manager, an operation mode flag of information indicating which of the second virtual machine manager and the user program is operating on the first virtual processor; determining, by the first virtual machine manager upon receiving the call for the first virtual machine manager, which of the second virtual machine manager and the user program to execute by referencing the operation mode flag; and instructing, by the first virtual machine manager, based on a result of the determining, the first virtual processor to execute one of the second virtual machine manager and the user program.