VIRTUAL MACHINE CONTEXT MANAGEMENT

• US 20160011895A1
• Filed: 07/10/2014
• Published: 01/14/2016
• Est. Priority Date: 07/10/2014
• Status: Active Grant

• Current Assignee: Red Hat Israel Ltd. (International Business Machines Corporation)
• Original Assignee: Red Hat Israel Ltd. (International Business Machines Corporation)
• Inventors: Tsirkin, Michael, Bonzini, Paolo
• Granted Patent: US 11,249,777 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 2009/45575 Starting, stopping, suspending or resuming virtual machine instances
• CPC Class Codes: G06F 2009/45591 Monitoring or debugging support
• CPC Class Codes: G06F 9/45558 Hypervisor-specific management and integration aspects
• CPC Class Codes: G06F 9/461 Saving or restoring of program or task context

Abstract

According to one example, a method performed by a physical computing system includes, with a hypervisor, detecting that a guest system running on a virtual machine has executed a halt instruction for a virtual processor of the virtual machine. The method further includes, with a physical processor, switching from a context of the virtual machine to a context of the hypervisor. The method further includes re-entering the context of the virtual machine in response to determining that there are no tasks pending for processes outside the context of the virtual machine, the processes being for execution by the physical processor.

Claims

1. A method performed by a physical computing system, the method comprising:

with a hypervisor, detecting a halt instruction for execution on a virtual processor of a virtual machine;

with a physical processor, exiting a context of the virtual machine to a context of the hypervisor;

before occurrence of an event intended to take the virtual processor out of a halt state, re-entering the context of the virtual machine in response to determining that there are no instructions pending execution on the physical processor, the instructions being outside the context of the virtual machine.

2. The method of claim 1, further comprising, halting the virtual processor if a time period between the halt instruction and a previous time the virtual processor entered a halt state exceeds a threshold time period.

3. The method of claim 1, wherein the instructions pending for processes outside the context of the virtual machine comprise tasks for a hypervisor process.

4. The method of claim 1, wherein the instructions pending for processes outside the context of the virtual machine comprise tasks for a different virtual machine process.

5. The method of claim 1, further comprising, keeping the virtual processor in an operating state in response to determining that interrupts are enabled.

6. The method of claim 1, wherein re-entering the context of the virtual machine comprises re-entering at a same address as the halt instruction.

7. The method of claim 1, wherein re-entering the context of the virtual machine comprises re-entering at an address subsequent to the halt instruction.

8. The method of claim 1, further comprising, before re-entering the context of the virtual machine, executing a waiting instruction.

9. The method of claim 1, further comprising, halting the virtual processor in response to determining that interrupts are not enabled.

10. The method of claim 1, further comprising, halting the virtual processor and exiting the context of the virtual processor if it is determined that other instructions are pending for execution by the processor.

11. The method of claim 1, wherein the instructions pending for processes outside the context of the virtual machine comprise tasks for a host machine associated with the processor.

12. A computing system comprising:

a processor; and

a memory comprising computer readable instructions that when executed by the processor, cause the system to;

run a hypervisor to host a virtual machine;

detect a halt instruction for execution by a virtual processor;

cause the processor to exit a context of the virtual machine;

determine that there are no pending instructions for execution by the processor; and

re-enter the context of the virtual machine.

13. The system of claim 12, wherein the processor is to further cause the system to halt the virtual processor in response to determining that another virtual machine has pending instructions for the processor.

14. The system of claim 12, wherein the processor is to further cause the system to halt the virtual processor if it is determined that interrupts are not enabled.

15. The system of claim 12, wherein the processor is to further cause the system to execute a pause instruction before re-entering the context of the virtual machine.

16. The system of claim 12, wherein the processor is further to cause the system to re-enter the context of the virtual machine at an address that is at or after an address of the halt instruction.

17. The system of claim 12, wherein the pending instructions for execution by the processor are associated with a different virtual machine.

18. A method performed by a physical computing system, the method comprising:

with a hypervisor, detecting that a guest system running on a virtual machine has provided a halt instruction for execution on a virtual processor of the virtual machine;

with a physical processor of the physical system, switching from a context of the virtual machine to a context of the hypervisor; and

re-entering the context of the virtual machine in response to determining that;

interrupts are enabled; and

there are no instructions pending for processes outside the context of the virtual machine, the processes being for execution by the physical processor.

19. The method of claim 18, wherein re-entering the context of the hypervisor comprises re-entering the context of the virtual machine at an address that is at or after an address of the halt instruction.

20. The method of claim 18, wherein the instructions pending for processes outside the context of the virtual machine are associated with a different virtual machine.