Method for managing I/O buffers in shared storage by structuring buffer table having entries include storage keys for controlling accesses to the buffers

摘要

A program stored on a portable storage medium for transferring the program from/to a data processing system, including to or from a disk medium in the system. The program manages I/O buffers that use I/O storage protection key for protecting storage blocks (page frames) in a shared main storage against unwanted I/O accesses, but the I/O storage keys do not protect the storage blocks from an CP (central processor) accesses. CP key protection may optionally be provided to independently protect the same storage block against unwanted CP accesses. Processes initialize, and address I/O buffers used by I/O programs; each I/O buffer is comprised of a contiguous set of the blocks (page frames). The I/O keys are used independently of any CP keys, and both I/O and CP keys are required for protecting any block against unwanted accesses by both I/O and CP accesses. The I/O keys are supported by a hardware I/O storage key array when real (or absolute) addressing is used by I/O the programs. However, the CP keys may be, but need not be, supported by CP keys in a second hardware key array; since the CP storage keys instead may be supported as virtual CP keys in CP key fields in page table entries (which are used in translating CP virtual addresses to CP real addresses). The separate I/O and CPU storage protection functions may each include any or all of: write protection, read protection, and storage key protection for page frames.