Peter Hermon Gum

System/370 extended architecture: facilities for virtual machines

This paper describes the evolution of facilities for virtual machines on IBM System/370 computers, and presents the elements of a new architectural facility designed for the virtual-machine environment. Assists that have been added to various System/370 models to support the use of virtual machines are summarized, and a general facility for this purpose which was introduced with the System/370 Extended Architecture (370-XA) is described. A new instruction of the 370-XA architecture places the machine in a specific mode in which several special capabilities are enabled. These allow the machine to provide execution in the virtual-machine environment of most of the instructions (including many privileged instructions) and most of the facilities (such as dynamic address translation) of both the System/370 and the 370-XA architectures. The major features of this new facility are individually discussed and summarized.

ESA/390 interpretive-execution architecture, foundation for VM/ESA

The interpretive-execution facility of Enterprise Systems Architecture/390™ (ESA/390™) provides an instruction for the execution of virtual machines. This instruction, called START INTERPRETIVE EXECUTION (SIE), was initially created for virtualizing either System/370 or 370-XA architectures, and was used later for virtualizing ESA/370™ and ESA/390 architectures. SIE has evolved to provide capabilities for a number of specialized performance environments. Most recently it provides for the unique requirements of Enterprise Systems Architecture/Extended Configuration (ESA/XC) virtual-machine architecture. This comprehensive set of capabilities in the architecture serves as the platform for the ability of VM/ESA™ to provide functions in virtual machines for end users and system servers. This paper describes the evolution of SIE and outlines use of the various capabilities in VM/ESA.