Changing frequency of a virtual programmable interrupt timer in virtual machines to control virtual time

Patent metadata

Field	Value
Publication number	US-9110698-B2
Application number	US-201314020209-A
Country	US
Kind code	B2
Filing date	Sep 6, 2013
Priority date	Aug 4, 2005
Publication date	Aug 18, 2015
Grant date	Aug 18, 2015

Abstract

A catch-up mode that runs a virtual programmable interrupt timer faster than a nominal rate to prevent time loss in a virtual machine can be implemented. If time loss is determined, a catch-up mode can be initiated to cause increased firings, beyond a nominal rate, of the programmable interrupt timer to adjust the clock of the virtual machine to the clock of the host system. The virtual programmable interrupt timer can also be readjusted to a predetermined nominal rate when the time loss in the guest operating system is determined approximately within a predetermined tolerance range. The catch-up mode can be monitored to avoid “interrupt storms” on the virtual machine. The virtual programmable interrupt timer can be altered by the guest operating system to accommodate different operating systems.

First claim

What is claimed:

1. A method for controlling time loss within a virtual machine operating on a computing device, comprising:
detecting a time loss in an operating system executing on the virtual machine, when an expected timer expiration time of the virtual machine and an actual timer expiration time of the computing device is outside of a predetermined tolerance range;
adjusting a virtual programmable interrupt timer responsive to the time loss to operate at a rate greater than…

Assignees

• Microsoft Technology Licensing Llc

Inventors

• Nicholas Andrew Ernest
• Vega Rene Antonio

Classifications

• G06F9/45533 Primary

  Physics · mapped topic

• G06F9/4825

  Physics · mapped topic