| 摘要 |
Combines a storage protect key stack with an access key register (AKR) and active access key (AAK) select circuits. Storage key entries in the stack correspond to the physical blocks in main memory. This combination can provide storage protection for different storage access types within address sub-ranges in the main memory associated with respective access keys. The sub-ranges are blocks of addresses within the full range of addresses of the physical memory. The protect key operation applies to physical addresses, and it obtains system addressing compatibility with an address translation operation using the same access keys as address keys with program logical addresses. Special features include a shared protect key, which need not be loaded in the AKR, to make specified sub-range(s) shareable by all users of the system, so that any user can access the blocks in memory associated with the shared protect key. For I/O accesses, an override is provided which ignores any read-only control of any memory block to which an I/O access is requested. Supervisor accesses can be made in all key areas, regardless of the AAK, the protect keys, or the read-only flag bits. |
