1. A virtualization method for a machine having a processor and memory connected to the processor, wherein the machine includes: a first virtual machine manager that is executed by the processor and manages a plurality of virtual machines generated by virtually dividing a physical resource of the machine; a second virtual machine manager that is executed on each of the virtual machines and manages an operating system to execute an application; first management information that is stored in the memory by the first virtual machine manager and manages status of the first virtual machine manager and the second virtual machine manager; second management information that is stored in the memory by the second virtual machine manager and manages status of the second virtual machine manager and one of the operating system and the application; and wherein the processor includes: a register to store control information for controlling the processor; and a shadowing function to read a specified value from one of the first management information and the second management information in accordance with a read operation on the register, the virtualization method comprising: a first step for the first virtual machine manager to detect a call from the second virtual machine manager; a second step for the first virtual machine manager to determine whether an instruction for enabling the shadowing function causes a call from the second virtual machine manager; and a third step for the first virtual machine manager to enable the shadowing function when it is determined that an instruction for enabling the shadowing function causes a call from the second virtual machine manager.