Operating system accessing control blocks by using home address space segment table to control instruction and operand fetch and store operations

Claim 1

In a data processing system having a CPU, a dynamic address translation facility, a system storage including address spaces and an operating system including a dispatcher, said CPU further including a multi-field program status word and a plurality of control registers which store segment table designators containing pointers to segment tables used by said dynamic address translation facility for translating virtual addresses in at least one of said address spaces in said system storage accessible to said CPU, a method for providing an improved and efficient way for said operating system to access control blocks, instructions and data in a multiple address space environment, said method comprising the steps of: a. dispatching, via said dispatcher, an address space having the highest priority with a dispatchable unit of work as a home address space which contains control blocks for defining said dispatchable unit of work; b. loading a pointer to a segment table for said home address space in one of said control registers to provide virtual address translation in said home address space; c. setting, via a CPU instruction, address space control bits in a field of said program status word in said CPU thereby identifying a home mode and causing said home address space segment table to be the one to be used by said dynamic address translation facility to translate virtual addresses in said home address space; and then d. accessing said control blocks by said operating system using said home address space segment table to predictably control instruction and operand fetch and store operations from and to said home address space for said dispatchable unit of work in said home address space accessible to said CPU when said program status word in said CPU is set to home mode, without further modification of any other segment table designators.