Contemporary Concepts of Microprogramming and Emulation
ACM Computing Surveys (CSUR)
Protection and the control of information sharing in multics
Communications of the ACM
A hardware architecture for implementing protection rings
Communications of the ACM
Architecture of virtual machines
Proceedings of the workshop on virtual computer systems
Extended architecture and Hypervisor performance
Proceedings of the workshop on virtual computer systems
Sharing data and services in a virtual machine system
SOSP '75 Proceedings of the fifth ACM symposium on Operating systems principles
Verifiable secure operating system software
AFIPS '74 Proceedings of the May 6-10, 1974, national computer conference and exposition
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The architecture of a virtual machine system has specific advantages over that of conventional operating systems because virtual machines are well separated from one another and from the control program. This structure requires that a protected, multi-user resource manager be placed in a distinct virtual machine because the protection domain and scheduling unit are one entity, the virtual machine. But cooperation between distinct virtual machines necessarily entails scheduling overhead and often delay. This paper describes an experimental extension to VM/370 whereby a distinct execution and data domain (Virtual Control Storage) is made available to virtual machines that require access to a resource manager, without requiring a change in the scheduling unit. Thus scheduling overhead and delays are avoided when transition is made between user program and resource manager. A mechanism is described for exchanging data between execution domains by means of address-space mapping.