Virtual machine control program and virtual machine system

A virtual machine system having a CPU and memory in which a plurality of OS's and a control program for making the plurality of OS's operate are installed,

• wherein the CPU has a memory protection function controlled based on a data structure,
• wherein the data structure includes the first field and the second field that control approval/disapproval of a memory operation in each memory area,
• wherein the memory protection function generates a protection exception to an operation of the memory area when the first or second field thereof is set as operation-prohibited, and creates the cause code indicating a field that became a reason of occurrence of the protection exception,
• wherein the OS controls the first data structure that is made up of the data structure on the memory,
• wherein the first data structure is such that a memory area being set as operation-prohibited by the first field is larger than the memory area being set as operation-prohibited by the second field, and
• wherein the control program has:
• a function of referring to the first data structure;
• a function of creating a second data structure that is made up of the data structure and such that a memory operation of the memory area requiring emulation of reading/writing is prohibited using the second field;
• a function of making the memory protection function refer to the second data structure;
• and
• a function of determining the necessity of emulation by referring to the cause code at the time of occurrence of the protection exception.

A virtual machine system that is realized by program processing using a computer system including a CPU and memory and in which a plurality of OS's and a control program for driving the plurality of OS's are installed,

• wherein each of the plurality of OS's is equipped with a first event handler and a first data structure such that the memory is divided into a plurality of memory areas and a memory address and access approval/disapproval are controlled in the each memory area,
• wherein the control program is equipped with a second event handler, a first function of executing emulation in response to an instruction issued by each of the plurality of OS's, and a second function of creating a second data structure reflecting the first data structure,
• wherein each of the first and second data structures is equipped with the first field and that second field that specify access approval/disapproval in the each memory area,
• wherein the CPU makes notification to the first event handler when the first field of the second data structure is set as access-prohibited,
• wherein the CPU makes notification to the second event handler when the second field of the second data structure is set as access-prohibited, and
• wherein the control program executes the emulation when notification is made to the second event handler.