Processor and I/O Storage Protection for Relocate Mechanisms
Original Publication Date: 1985-Oct-01
Included in the Prior Art Database: 2005-Feb-19
This protection mechanism provides isolation of storage access from processor and I/O devices to shared storage on a segment basis determined by the source of the storage request. As shown in the figure, the relocate mechanism acts as the address translator and storage controller for requests generated by the processor or I/O devices on the I/O bus. Since storage is being shared by the processor and I/O devices, a mechanism is required that selectively accesses specific storage areas for the processor only, I/O only, both, or neither. The relocate mechanism provides three access control facilities. The first facility determines if an access is allowed based on the source of the request (processor or I/O device), and the processor and I/O access protect bits in the selected segment register.