US 5,809,546 AGranted

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

AssigneeInternational Business Machines Corporation

InventorsPaul Gregory Greenstein, Richard Roland Guyette, John Ted Rodell

Life of this patent

Estimating the term…

Loading patent…

Abstract

I/O protection key processes for protecting storage blocks (page frames) in a shared main storage against unwanted I/O accesses. Independent CP (central processor) key protection may optionally be provided to protect the same storage against unwanted CP accesses. Processes are included for initializing, and addressing I/O buffers used by the I/O programs; each I/O buffer is comprised of a contiguous set of the blocks (page frames). The I/O keys may be used independently of any CP keys provided for protecting the same blocks against unwanted accesses by any CP in the system. The I/O keys must be supported by a hardware I/O storage array when only real (or absolute) addressing is used by I/O programs. However, the CP keys may be supported by either real CP keys in a second hardware key array; or alternatively the CP keys may be provided as virtual CP keys in a field in each page table entry (which is used for translating CP virtual addresses to CP real addresses). The separate I/O and CPU access protection functions may each include any or all of: write protection, read protection, and storage key protection for page frames.

Claims21

Dependent claims

A method of managing I/O buffers in a shared main storage of a data processing system, comprising the steps of:

indicating a size indicator for each I/O buffer to be setup for indicating the number of blocks of storage in each I/O buffer,
allocating storage for each I/O buffer to be setup, and fixing the allocated storage in the shared main storage for each I/O buffer to prevent paging out to I/O of any block in an I/O buffer,
selecting an entry in a I/O buffer table (IOBT) to represent each I/O buffer being setup, and setting an in-use indicator to an in-use state in the entry to lock the entry for preventing interference during buffer setup,
storing in the entry:
the size indicator obtained from the indicating step, an address to the location of the I/O buffer in the shared main storage, and an I/O storage key for managing an I/O storage key for the I/O buffer,
loading each I/O storage key from a respective entry in the IOBT into an I/O storage key array of a storage controller at locations corresponding to locations of blocks in an associated I/O buffer, and
setting the in-use indicator in the respective entry to a not-in-use state to prevent use of a respective I/O buffer until the I/O buffer is assigned to a using program.

4 more elements

Dependencies are inferred from the claim text.