Part 1. Control Program (CP) Part 1 contains the following information:
Introduction to VM/SP Program States Using Processor Resources
Interruption Handling
Functional Information
Performance Guidelines
Virtual Machine Assist Feature VM/370 Extended Control-Program Support VM/VS Handshaking
Performance Observation and Analysis
Accounting Information
Generating Named Systems and Saving Systems The Virtual Machine Communication Facility
The Inter-User Communications Vehicle SNA Virtual Console Support The Message System Service The DASD Block I/O System Service The Special Message Facility
The Single Image Consol Facility VM/SP Use of the IBM 3850 MSS The Logical Device Support Facility Timers CP in Attached Processor and Multiprocessor Modes DIAGNOSE Instruction CP Conventions
How To Add a Console Function
How To Add a New Print or Forms Buffer Image
The IBM 3800 Printing Subsystem
J ournaling Logon, Autolog, and Link Commands
Suppressing Passwords
Part 1. Control Program (CP)
VM/SP The VM/SP Control Program manages the resources of a single computer in such a
manner that multiple computing systems appear to exist. Each "virtual" computing
system, or virtual machine, is the functional equivalent of an IBM System/370. A virtual machine is configured by recording appropriate information in the VM/SP directory. The virtual machine configuration includes counterparts of the
components of a real IBM System/370: A virtual operator's console
Virtual storage
A virtual processor
Virtual I/O devices CP makes these components appear real to whichever operating system is control­
ling the work flow of the virtual machine.
The virtual machines operate concurrently via multiprogramming techniques. CP overlaps the idle time of one virtual machine with execution in another.
Each virtual machine is managed at two levels. The work to be done by the virtual
machine is scheduled and controlled by some System/360 or System/370 operat­
ing system. The concurrent execution of multiple virtual machines is managed by
the Control Program. VM/SP performs some functions differently when running in attached processor or
multiprocessor mode. For a description of the additional processing performed, see
the VM / SP System Logic and Problem Determination Guide.
Introduction to the VM/SP Control Program
2 VM!SP System Programmer's Guide
A virtual machine is created for a user when he logs on VM/SP, on the basis of
information stored in his VM/SP directory entry. The entry for each user identifi­
cation includes a list of the virtual input/output devices associated with the partic­
ular virtual machine.
Additional information about the virtual machine is kept in the VM/SP directory
entry. Included are the VM/SP command privilege class, accounting data, normal
and maximum virtual storage sizes, dispatching priority, and optional virtual
machine characteristics such as extended control mode.
The Control Program supervises the execution of virtual machines by permitting
only problem state execution except in its own routines, and receiving control after
all real computing system interrupts. CP intercepts each privileged instruction and
simulates it if the current program status word of the issuing virtual machine indi­
cates a virtual supervisor state; if the virtual machine is executing in virtual prob­
lem state, the attempt to execute the privileged instruction is reflected to the virtual
machine as a program interrupt. All virtual machine interrupts (including those
caused by attempting privileged instructions) are first handled by CP, and are
reflected to the virtual machine if a similar interrupt would have occurred on a real
machine.
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