Program States When instructions in the Control Program are being executed, the real
computer is in the supervisor state; at all other times, when running
virtual machines, the real computer is in the problem state. Therefore,
privileged instructions cannot be executedby the virtual machine. Programs running on a virtual machine can issue Frivileged instructions;
but such an instruction either (1) causes an interruption that is
handledby the Control program, or (2) is intercepted and handled by the
processor, if the virtual machine assist feature orVK/370 Extended
Control-program Support is enabled and supports that instruction.CP examines the operating status of the virtual machine PSi. If the
virtual machine indicates that it is functioning in supervisor mode, the
privileged instruction is simulated according to its type.II the virtual machine is in problem mode, the privileged interrupt is
reflected to the virtual machine.Only the Control Program may operate in the supervisor state on the
real machine. All programs other thanCP operate in the problem state
on the real machine. All user interrupts, including those caused by
attempted privileged operations, are handled by either the control
program or the processor (if the virtual machine assist feature orVK/370 Extended Control-program Support is available). Only those
interrupts that the user program would expect from a real machine are
reflected to it. A problem program executes on the virtual machine in amanner identical to its execution on a real System/370 processor
l as
long as the problem program does not violate theCP restrictions. CP restrictions are documented in the Part 2. Control Program (CP) 83
computer is in the supervisor state; at all other times, when running
virtual machines, the real computer is in the problem state. Therefore,
privileged instructions cannot be executed
but such an instruction either (1) causes an interruption that is
handled
processor, if the virtual machine assist feature or
Control-program Support is enabled and supports that instruction.
virtual machine indicates that it is functioning in supervisor mode, the
privileged instruction is simulated according to its type.
reflected to the virtual machine.
real machine. All programs other than
on the real machine. All user interrupts, including those caused by
attempted privileged operations, are handled by either the control
program or the processor (if the virtual machine assist feature or
interrupts that the user program would expect from a real machine are
reflected to it. A problem program executes on the virtual machine in a
l as
long as the problem program does not violate the