Virtual computer system

In a virtual computer system for selectively running a plurality of operating system programs under control of a virtual machine monitor program and having a main storage for storing said operating system programs and said virtual machine monitor program, the improvement comprising:

• an operation unit;
• at least one group of operand registers connected to said operation unit and said main storage each for holding address or data signals provided from, or to be provided to, said main storage or said operation unit;
• a group of instruction address registers each provided for a respective one of the programs, including the virtual machine monitor program and the operating system programs;
• a first identification register for holding an identification signal indicating a running program from among the operating system programs and the virtual machine monitor program;
• selection means connected to said group of instruction address registers and said first identification register for holding an instruction address register corresponding to the running program in an accessible state;
• instruction execution means connected to said main storage, said operation unit and said group of instruction address registers for executing instructions of the running program, including means for repeatedly renewing contents of said one instruction address register held in an accessible state by said selection means and for fetching an instruction of the running program from said main storage based upon the renewed contents of said one instruction address register.

In a virtual computer system for selectively running a plurality of operating system programs under control of a virtual machine monitor program and having a main storage for storing said operating system programs and said virtual machine monitor program, the improvement comprising:

• an operation unit;
• instruction execution means connected to said main storage and said operation unit for executing instructions of a running program from among the operating system programs and the virtual machine monitor program;
• a group of status registers, each status register being provided for a respective one of the operating system programs and the virtual machine monitor program and each for holding an interrupt mask signal;
• an identification register for holding an identification signal designating a program from among the virtual machine monitor program and the operating system programs;
• selection means connected to said group of status registers and said identification register for holding one status register corresponding to a program designated by said identification signal in an accessible state;
• and
• access means connected to said group of status registers and said instruction execution means, and responsive to said instruction execution means executing an instruction requiring access to a status register, for reading or rewriting an interrupt mask signal in said one status register held in an accessible state by said selection means.

In a virtual computer system for selectively running a plurality of operating system programs under control of a virtual machine monitor program and having a main storage for storing said operating system programs and said virtual machine monitor program, the improvement comprising:

• an operation unit;
• identification signal designating a program running on said system from among the virtual machine monitor program and the operating system programs;
• a group of instruction address registers connected to said main storage, each instruction address register being provided for a corresponding one of the virtual machine monitor program and the operating system programs, each for holding an address of an instruction to be fetched from said main storage;
• a plurality of groups of operand registers connected to said main storage and said operation unit, each group of operand registers being provided for a respective one of said virtual machine monitor program and operating system programs and each operand register holding an address or data signal provided from, or to be provided to, said main storage or said operation unit;
• selection means connected to said first identification register, said group of instruction address registers and said plurality of groups of operand registers for holding one of said instruction address registers and one group of operand registers both corresponding to said running program designated by the first identification signal in an accessible state;
• and
• instruction execution means connected to said first identification register, said group of instruction address registers, said groups of operand registers, said main storage and said operation unit for executing instructions of the running program, said instruction execution means including first means for repeatedly renewing contents of said one instruction address register held in an accessible state by said selection means and for fetching from said main storage an instruction of the running program based upon said renewed contents and second means for accessing an operand register within said one group of operand registers held in an accessible state, when the fetched instruction required access to one of said operand registers.