SELECTIVE RESOURCE ACTIVATION BASED ON PRIVILEGE LEVEL

• US 20170123800A1
• Filed: 11/04/2015
• Published: 05/04/2017
• Est. Priority Date: 11/04/2015
• Status: Active Application

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Frazier, Giles R., Stanton, David A. Larson
• Application Number:
  US14/931,938
• Publication Number:
  US 20170123800A1
• Time in Patent Office: Days
• CPC Class Codes: G06F 2009/45575 Starting, stopping, suspending or resuming virtual machine instances
• CPC Class Codes: G06F 9/45533 Hypervisors; Virtual machine monitors
• CPC Class Codes: G06F 9/45558 Hypervisor-specific management and integration aspects
• CPC Class Codes: G06F 9/48 Program initiating; Program switching, e.g. by interrupt

Abstract

Prevention of “context-changing interrupts” (see definition, below) and/or “performance-affecting interventions” (see definition, below) to be made with respect to a newly-dispatched program before the relevant control registers associated with the program have been initialized. This can be especially helpful in systems where control registers are not initialized until the newly-dispatched program needs to use a facility and/or resource that requires initialization of the control registers.

Claims

1. A method for use with a computer system including a plurality of resources and a processor(s) set including a plurality of control registers, the method comprising:

starting to run a program;

in response to starting to run the program, controlling initialization of control registers of the plurality of control registers that are associated with the program so that at least some of the control registers do not immediately initialize in direct response to the starting of the running of the program;

receiving, from a first resource of the plurality of resources, an attempt to make a context-changing interrupt with respect to the program;

determining whether the attempted context-changing interrupt by the first resource would involve control registers associated with the program that have not been initialized; and

in response to a determination that the attempted context-changing interrupt would involve control registers that have not been initialized, preventing, by machine logic, the attempted context-changing interrupt from proceeding.

2. The method of claim 1 wherein the program starts to run at a privilege level other than the lowest privilege level.

3. The method of claim 1 further comprising:

in response to a determination that the attempted context-changing interrupt would not involve control registers that have not been initialized, allowing the attempted context-changing interrupt to proceed.

4. The method of claim 1 wherein the attempted context-changing interrupt is designed to change context in at least one of the following types of context:

privilege level, priority, address translation, available facilities, and/or replace the executing program.

5. The method of claim 1 wherein the attempted interrupt is an asynchronous interrupt.

6. The method of claim 1 wherein the prevention, by machine logic, of the attempted context-changing interrupt includes disabling the associated resource until control registers required by that resource have been initialized.

7. A computer program product comprising:

a storage device structured and/or programmed to store machine readable data in a manner that is not transitory in the way that a signal in transit is transitory;

data stored on the storage device, including respective sets of machine readable instructions respectively programmed to cause a set of processor(s) to perform the following actions;

start to run a program,

in response to starting to run the program, control initialization of control registers of the plurality of control registers that are associated with the program so that at least some of the control registers do not immediately initialize in direct response to the starting of the running of the program,

receive, from a first resource of the plurality of resources, an attempt to make a context-changing interrupt with respect to the program,

determine whether the attempted context-changing interrupt by the first resource would involve control registers associated with the program that have not been initialized, and

in response to a determination that the attempted context-changing interrupt would involve control registers that have not been initialized, prevent, by machine logic, the attempted context-changing interrupt from proceeding.

8. The computer program product of claim 7 wherein the set of machine readable instructions programmed to start to run a program are further programmed to start to run at a privilege level other than the lowest privilege level.

9. The computer program product of claim 7 wherein the data stored on the storage device further includes a further set of machine readable instructions programmed to cause a computer system to:

in response to a determination that the attempted context-changing interrupt would not involve control registers that have not been initialized, allow the attempted context-changing interrupt to proceed.

10. The computer program product of claim 7 wherein the attempted context-changing interrupt is designed to change context in at least one of the following types of context:

privilege level, priority, address translation, available facilities, and/or replace the executing program.

11. The computer program product of claim 7 wherein the attempted interrupt is an asynchronous interrupt.

12. The computer program product of claim 7 wherein the set of machine readable instructions programmed to prevent the context-changing interrupt are further programmed to effect the prevention by disabling the associated resource until control registers required by that resource have been initialized.

13. The computer program product of claim 7 further comprising:

a set of processor(s) is structured and/or programmed to perform the actions corresponding to the sets of machine readable instructions, and includes the control registers.

14. A method for use with a computer system including a plurality of resources and a processor(s) set including a plurality of control registers, the method comprising:

starting to run a program;

in response to starting to run the program, controlling initialization of control registers of the plurality of control registers that are associated with the program so that at least some of the control registers do not immediately initialize in direct response to the starting of the running of the program;

subsequent to the control of initialization of control registers so that at least some of the control registers do not immediately initialize, initializing the at least some of the control registers; and

controlling, by machine logic included in a processor(s) set, a first facility included in the processor(s) set so that the first facility does not attempt to make a performance-affecting intervention in the running of the program until after initialization of the at least some of the control registers, with a performance-affecting intervention being defined as any “

intervention”

which;

(i) does not change the order of execution of instructions of the program, and (ii) does impact performance of the program.

15. The method of claim 14 wherein the first facility is a data stream control register (DSCR).

16. The method of claim 14 wherein the performance-affecting intervention will, if allowed, affect execution speed.

17. The method of claim 14 wherein the performance-affecting invention will, if allowed, affect at least one of the following characteristics and/or actions:

data cache size, data cache replacement algorithm, branch prediction method, branch prediction history buffer depth, program priority register, freezing of priority at some default regardless of the priority register value, disabling a register that controls instruction fusion, routing of instructions in specific ways in an internal pipeline, and/or branch history rolling buffer (BHRB) size.

18. The method of claim 14 wherein the program starts to run at a privilege level other than the lowest privilege level.

19. The method of claim 14 wherein the program starts to run at the lowest privilege level.

20. The method of claim 14 further comprising:

controlling, by machine logic included in a processor(s) set, the first facility included in the processor(s) set so that the first facility does make a performance-affecting intervention(s) in the running of the program after initialization of the at least some of the control registers.