Providing support for a timer associated with a virtual machine monitor

• US 20060075402A1
• Filed: 09/30/2004
• Published: 04/06/2006
• Est. Priority Date: 09/30/2004
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Schoenberg, Sebastian, Anderson, Andrew V., Neiger, Gilbert, Bennett, Steven M., Uhlig, Richard A., Rodgers, Dion, Hall, Clifford D., Smith, Lawrence O., Glew, Andy, Cota-Robles, Erik, Kozuch, Michael
• Granted Patent: US 7,840,962 B2
• Time in Patent Office: Days
• US Class Current: 718/1
• CPC Class Codes: G06F 9/45558 Hypervisor-specific management and integration aspects

Abstract

In one embodiment, a method includes transitioning control to a virtual machine (VM) from a virtual machine monitor (VMM), determining that a VMM timer indicator is set to an enabling value, and identifying a VMM timer value configured by the VMM. The method further includes periodically comparing a current value of a timing source with the VMM timer value, generating an internal event if the current value of the timing source has reached the VMM timer value, and transitioning control to the VMM in response to the internal event without incurring an event handling procedure in any one of the VMM and the VM.

Claims

1. A method comprising:

transitioning control to a virtual machine (VM) from a virtual machine monitor (VMM);

determining that a VMM timer indicator is set to an enabling value;

identifying a VMM timer value configured by the VMM;

periodically comparing a current value of a timing source with the VMM timer value;

generating an internal event if the current value of the timing source has reached the VMM timer value; and

transitioning control to the VMM in response to the internal event, without incurring an event handling procedure in any one of the VMM and the VM.

2. The method of claim 1 further comprising:

transitioning control to the VMM; and

informing the VMM that control is returned to the VMM due to the VMM timer value.

3. The method of claim 1 wherein identifying the VMM timer value configured by the VMM comprises retrieving the VMM timer value from a virtual machine control structure (VMCS).

4. The method of claim 4 wherein periodically comparing the current value of the timing source comprises:

comparing the current value of the timing source with the VMM timer value after each cycle executed by the VM.

5. A method comprising:

transitioning control to a virtual machine (VM) from a virtual machine monitor (VMM);

determining that a VMM timer indicator is set to an enabling value;

decrementing, every predefined number of ticks of a timing source, a VMM timer value, while executing the VM;

generating an internal event if determining that the VMM timer value has reached zero, and

transitioning control to the VMM in response to the internal event, without incurring an event handling procedure in any one of the VMM and the VM.

6. The method of claim 5 further comprising:

detecting a fault associated with a transition of control to the VMM;

storing the decremented VMM timer value in a virtual machine control structure (VMCS); and

transitioning control to the VMM.

7. The method of claim 5 further comprising:

storing the VMM timer value in a register.

8. An apparatus comprising:

a virtual machine monitor (VMM);

a data structure controlled by the VMM, the data structure storing a VMM timer indicator and a VMM timer value configured by the VMM; and

VMM timer support logic to transition control to a virtual machine (VM) from the VMM, to determine that the VMM timer indicator is set to an enabling value, to periodically compare a current value of a timing source with the VMM timer value, to generate an internal event if the current value of the timing source has reached the VMM timer value, and to transition control to the VMM in response to the internal event, without incurring an event handling procedure in any one of the VMM and the VM.

9. The apparatus of claim 8 wherein the VMM timer support logic is further to transition control to the VMM, and to inform the VMM that control is returned to the VMM due to the VMM timer value.

10. The apparatus of claim 8 wherein the VMM timer logic is to periodically compare the current value of the timing source by comparing the current value of the timing source with the VMM timer value after each cycle executed by the VM.

11. An apparatus comprising:

a virtual machine monitor (VMM);

a data structure controlled by the VMM, the data structure storing a VMM timer indicator; and

VMM timer support logic to transition control to a virtual machine (VM) from the VMM, to determine that the VMM timer indicator is set to an enabling value, to decrement, every predefined number of ticks of a timing source, a VMM timer value, while executing the VM, to generate an internal event if determining that the VMM timer value has reached zero, and to transition control to the VMM in response to the internal event, without incurring an event handling procedure in any one of the VMM and the VM.

12. The apparatus of claim 11 wherein the VMM timer support logic is further to detect a fault associated with a transition of control to the VMM prior to determining that the VMM timer has reached zero, to store the decremented VMM timer value in the data structure controlled by the VMM, and to transition control to the VMM.

13. The apparatus of claim 11 further comprising:

a register to store the VMM timer value.

14. A system comprising:

a memory to store a timer indicator and a timer value; and

a processor, coupled to the memory, to use the timer indicator to determine during operation of a virtual machine (VM) that a virtual machine monitor (VMM) timer is enabled, to periodically compare a current value of a timing source with the timer value, and to generate an internal event if the current value of the timing source has reached the timer value, and to transition control to the VMM in response to the internal event, without incurring an event handling procedure in any one of the VMM and the VM.

15. The system of claim 14 wherein the processor is further to transition control to the VMM, and to inform the VMM that control is returned to the VMM due to the VMM timer value.

16. The system of claim 14 wherein the processor is to periodically compare the current value of the timing source by comparing the current value of the timing source with the VMM timer value after each cycle executed by the VM.

17. A system comprising:

a memory to store a timer indicator; and

a processor, coupled to the memory, to use the timer indicator to determine during operation of a virtual machine (VM) that a virtual machine monitor (VMM) timer is enabled, to decrement, every predefined number of ticks of a timing source, a VMM timer value, while executing the VM, to generate an internal event if determining that the VMM timer value has reached zero, and to transition control to the VMM in response to the internal event, without incurring an event handling procedure in any one of the VMM and the VM.

18. The system of claim 17 wherein the processor is further to detect a fault associated with a transition of control to the VMM prior to determining that the VMM timer has reached zero, to store the decremented VMM timer value in the data structure controlled by the VMM, and to transition control to the VMM.

19. The system of claim 17 further comprising:

a register to store the VMM timer value.

20. A machine-readable medium containing instructions which, when executed by a processing system, cause the processing system to perform a method, the method comprising:

transitioning control to a virtual machine (VM) from a virtual machine monitor (VMM);

determining that a VMM timer indicator is set to an enabling value;

identifying a VMM timer value configured by the VMM;

periodically comparing a current value of a timing source with the VMM timer value;

if the current value of the timing source has reached the VMM timer value, generating an internal event; and

transitioning control to the VMM in response to the internal event, without incurring an event handling procedure in any one of the VMM and the VM.

21. The machine-readable medium of claim 20 wherein the method further comprises:

transitioning control to the VMM; and

informing the VMM that control is returned to the VMM due to the VMM timer value.

22. The machine-readable medium of claim 20 wherein identifying the VMM timer value configured by the VMM comprises retrieving the VMM timer value from a virtual machine control structure (VMCS).

23. A machine-readable medium containing instructions which, when executed by a processing system, cause the processing system to perform a method, the method comprising:

transitioning control to a virtual machine (VM) from a virtual machine monitor (VMM);

determining that a VMM timer indicator is set to an enabling value;

decrementing, every predefined number of ticks of a timing source, a VMM timer value, while executing the VM;

generating an internal event if determining that the VMM timer value has reached zero, and

transitioning control to the VMM in response to the internal event, without incurring an event handling procedure in any one of the VMM and the VM.

24. The machine-readable medium of claim 23 wherein the method further comprises:

detecting a fault associated with a transition of control to the VMM;

storing the decremented VMM timer value in a virtual machine control structure (VMCS); and

transitioning control to the VMM.

25. The machine-readable medium of claim 23 wherein the method further comprises:

storing the VMM timer value in a register.