US 5,600,805 AGranted

Pass-through for I/O channel subsystem call instructions for accessing shared resources in a computer system having a plurality of operating systems

AssigneeInternational Business Machines Corporation

InventorsKenneth J. Fredericks, Robert E. Galbraith, Richard R. Guyette, Marten J. Halma, Roger E. Hough, Suzanne M. John, James C. Mazurowski, Kenneth J. Oakes, Leslie W. Wyman

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Abstract

Enables any OS of plural OSs within any of plural logical-resource partitions (LPARs) of a CEC to use interpretive execution for synchronously-executable CHSC (channel subsystem call) commands. A CHSC command authorization mask (CCAM) is provided to control which CHSC commands are allowed to execute interpretively (with pass-through), and which commands are executed with hypervisor intervention (as all prior CHSC commands did). By enabling interpretive execution of those commands which can successfully operate with pass-through, significant system efficiency is obtained. And by disabling interpretive execution for a subset of CHSC commands (which are not allowed to execute with pass-through) potential system failures may be prevented. Thus, interpretive execution may be restricted differently among the OSs in a CEC. Novel CHSC command execution now handles multiple images of shared I/O resources by use of image identifiers, which could not be done before. The information requested by any OS issuing a CHSC command is filtered and optionally compacted by the I/O subsystem responding to the command by only providing information obtained from control blocks associated with the OS which issued the command. This is done by having a set of control blocks for each I/O resource, each control block in the set being associated with a particular OS.

Claims20

Dependent claims

A method of controlling system hardware operations for a plurality of I/O subsystem call instructions issued by any of a plurality of operating systems (OSs), including control programs, executing on a computer electronic complex (CEC) in which the plurality of OSs operate in different logical partitions of resources of the CEC, comprising the steps of:

executing instructions on a central processor (CPU) of the CEC for any of the OSs, including different types of I/O subsystem call (CHSC) instructions for communicating different types of requests by OSs to the I/O subsystem for requesting different types of I/O subsystem data and operations, including a request for I/O configuration data;
sharing by the OSs of I/O resources of the I/O subsystem;
storing a pass-thru CHSC control mask (CCAM) in system storage having fields associated with different types of CHSC instructions;
accessing the CCAM during CPU execution of any type of CHSC instruction, and accessing a field in the CCAM associated with a type of CHSC instruction being currently executed by the CPU to indicate whether the CPU is to execute the CHSC instruction in a pass-thru mode or not;
and
if in pass-thru mode, signalling by the CPU to the I/O subsystem to continue execution of the CHSC instruction by obtaining I/O data and performing operations indicated for the CHSC instruction, including transferring by the I/O subsystem to a storage area available to a requesting OS of requested I/O data associated only with the requesting OS, and filtering out non-meaningful data of the requested type associated with other OSs in the CEC.

3 more elements

Dependencies are inferred from the claim text.