Communication interface of a secure interface control

A computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions executable a computer to cause operations comprising:

• receiving, by a communication interface of a secure interface control executing between the secure interface control of a computer and hardware of the computer, an instruction;
• determining, by the communication interface, whether the instruction is a millicoded instruction;
• entering, by the communication interface, a millimode comprising enabling the secure interface control to engage millicode of the hardware through the communication interface based on the instruction being the millicoded instruction;
• and
• executing, by the millicode, the instruction, wherein:
• during execution of the instruction, the hardware of the computer
• maintains a state of the calling entity, while the calling entity is running, independent of a state of the millicode;
• and
• the secure interface control includes a hardware mechanism that prevents storage locations assigned to secure entities from being accessed by other secure entities or by unsecured entities.

A system comprising:

• hardware comprising a millicode;
• a secure interface control;
• a communication interface of the secure interface control executing between the secure interface control and the hardware;
• wherein the system is executable to cause operations comprising:
• receiving, by the communication interface, an instruction;
• determining, by the communication interface, whether the instruction is a millicoded instruction;
• entering, by the communication interface, a millimode comprising enabling the secure interface control to engage millicode of the hardware through the communication interface based on the instruction being the millicoded instruction;
• and
• executing, by the millicode, the instruction, wherein:
• during execution of the instruction, the hardware of the computer
• maintains a state of the calling entity, while the calling entity is running, independent of a state of the millicode;
• and
• the secure interface control includes a hardware mechanism that prevents storage locations assigned to secure entities from being accessed by other secure entities or by unsecured entities.