FORCING REGISTERED CODE INTO AN EXECUTION CONTEXT OF GUEST SOFTWARE

• US 20090055571A1
• Filed: 08/08/2008
• Published: 02/26/2009
• Est. Priority Date: 08/08/2007
• Status: Active Grant

• Current Assignee: Vmware LLC (Broadcom, Inc.)
• Original Assignee: VMware, Inc. (Broadcom, Inc.)
• Inventors: Chen, Xiaoxin, Waldspurger, Carl, Subrahmanyam, Pratap, Horovitz, Oded, Budko, Dmitriy
• Granted Patent: US 8,250,519 B2
• Time in Patent Office: Days
• US Class Current: 711/6
• CPC Class Codes: G06F 2009/45587 Isolation or security of virtual machine instances
• CPC Class Codes: G06F 2009/45591 Monitoring or debugging support
• CPC Class Codes: G06F 21/53 by executing in a restricted environment, e.g. sandbox or secure virtual machine
• CPC Class Codes: G06F 9/45558 Hypervisor-specific management and integration aspects

Abstract

One embodiment of the present invention includes a method for: (a) executing guest computations in a virtual machine of the virtualization system; and (b) forcing execution of registered code into an execution context of the guest, wherein the forcing is performed from the virtualization system based on an execution trigger monitored without reliance on functionality of the guest software.

Claims

1. A method of operating a virtualization system, the method comprising:

executing guest computations in a virtual machine of the virtualization system; and

forcing execution of registered code into an execution context of the guest, wherein the forcing is performed from the virtualization system based on an execution trigger monitored without reliance on functionality of the guest software.

2. The method of claim 1, wherein the forcing includes:

performing an upcall from the virtualization system into the guest execution context, the upcall causing a transfer of control to an instruction sequence of the registered code; and

executing the registered code in the guest execution context based on the upcall.

3. The method of claim 2,

wherein the transfer of control is within the virtual machine from a then-executing instruction sequence of the guest.

4. The method of claim 2,

wherein the transfer of control is to an another virtual machine that is idle, not running or unscheduled.

5. The method of claim 3, further comprising:

returning control to the previously-executing instruction sequence of the guest.

6. The method of claim 2, further comprising:

during the execution of the registered code, disabling, masking or buffering at least a subset of interrupts ordinarily supplied to the guest by the virtual machine.

7. The method of claim 3, further comprising:

selecting, based at least in part on a then-operative interrupt model, a suitable point in the then-executing instruction sequence for the upcall.

8. The method of claim 2, further comprising:

forking to create a second instance of the virtual machine, the second virtual machine instance including a duplicate instance of an original guest execution context,

wherein the upcall is into the duplicate instance and the registered code is executed therein; and

wherein state associated with the duplicate instance is discarded after successful completion of the registered code, such that execution of the upcall is transparent to the original guest execution context.

9. The method of claim 1, further comprising:

cloaking the registered code from other execution contexts of the guest using a page mapping mechanism of the virtualization system.

10. The method of claim 1, further comprising:

instantiating the registered code in physical memory; and

updating memory mapping information maintained by the virtualization system for the guest execution context to include a mapping to the registered code;

executing the registered code under control of the guest, and

thereafter, updating the memory mapping information maintained by the virtualization system for the guest execution context to remove the mapping to the registered code.

11. The method of claim 1, further comprising:

forking to create a second instance of the virtual machine; and

executing the registered code in the second virtual machine instance.

12. The method of claim 11, further comprising:

performing an upcall into the guest execution context of the forked virtual machine instance and executing the registered code therein; and

upon completion of the registered code execution, exiting the forked virtual machine instance and reverting to pre-fork virtual machine state.

13. The method of claim 11,

wherein the virtualization system manages state of the guest execution context in the forked virtual machine instance using a copy-on-write mechanism;

and

wherein, upon completion of the registered code execution, state of the forked virtual machine instance is discarded such that execution of the registered code is transparent to an original instance of the virtual machine.

14. The method of claim 1, wherein the execution trigger is specified in terms of one or more events selected from a set including:

a time- or timer-based event;

a memory access or access attempt;

an input or output event; and

execution of, or failure to execute, some particular code of the guest computations.

15. The method of claim 1, further comprising:

registering the registered code in response to a request from within the virtual machine.

16. The method of claim 1,

wherein the registered code is identified in connection with configuration information for the virtual machine.

17. The method of claim 1, wherein the registered code includes code associated with operation of one or more of:

an antivirus system;

a firewall or gateway;

an intrusion detection system;

a performance or uptime monitoring system;

a license monitoring, metering or enforcement system;

a copyright or digital rights management system; and

critical operating system functionality.

18. The method of claim 1,

wherein the guest includes a guest operating system;

and

wherein the guest operating system coordinates execution of plural execution contexts including that into which the registered code is forced.

19. The method of claim 1,

wherein the guest includes a software appliance.

20. A computational system that forces execution of registered code into an execution context of guest software executing on a virtual machine, wherein the forcing is performed from behind a virtualization barrier based on an execution trigger monitored without reliance on functionality of the guest software.

21. The computational system of claim 20, further comprising:

a guest operating system instantiated in the virtual machine as the guest software,

wherein the guest operating system coordinates execution of plural execution contexts including that into which the registered code is forced.

22. The computational system of claim 20, further comprising:

a virtualization system that coordinates execution, on an underlying hardware machine, of instruction sequences that correspond to respective execution contexts of the guest software,

wherein the forcing includes performing, based on the execution trigger, an upcall from the virtualization system into the guest execution context, the upcall causing a transfer of control in the virtual machine from a then-executing instruction sequence of the guest software to an instruction sequence of the registered code; and

executing the registered code in the guest execution context based on the upcall.

23. The computational system of claim 20, further comprising:

a virtualization system that maintains mapping information for memory pages exposed by the virtual machine, the mapping being from a guest memory space to a physical memory space addressable by the virtualization system,

wherein the execution of the registered code is cloaked by updating memory mapping information maintained by the virtualization system for the guest execution context to include a mapping to the registered code, executing the registered code under control of the guest, and thereafter, updating the memory mapping information maintained by the virtualization system for the guest execution context to remove the mapping to the registered code.

24. The computational system of claim 20, further comprising:

a virtualization system that supports forking a duplicate instance of the virtual machine and which manages state of the guest execution context in the forked virtual machine instance using a copy-on-write mechanism,

wherein, upon completion of the registered code execution, state of the guest execution context in the forked virtual machine instance is discarded such that the execution of the registered code is transparent to the guest software executing in an original instance of the virtual machine.

25. An apparatus comprising:

a hardware machine;

virtualization software encoded in one or more media accessible to the hardware machine and executable to expose at least one virtual machine using resources of the hardware machine; and

guest software encoded in one or more media accessible to the virtual machine, the guest software executable on an exposed virtual machine,

wherein the virtualization software includes code executable on the hardware machine to force execution of registered code into an execution context of the guest software, wherein the forcing is performed from behind a virtualization barrier based on an execution trigger monitored without reliance on functionality of the guest software.

26. A computer program product comprising:

one or more functional sequences executable as, or in conjunction with, a virtualization system to force execution of registered code into an execution context of guest software executing on a virtual machine, wherein the forcing is performed from behind a virtualization barrier based on an execution trigger monitored without reliance on functionality of the guest software.

27. The computer program product of claim 26, further comprising:

an upcall interface by which the virtualization system initiates a transfer of control in the virtual machine from a then-executing instruction sequence of a guest execution context to an instruction sequence of the registered code.

28. The computer program product of claim 26, further comprising:

memory management code executable to selectively update page table entries maintained by the virtualization system for the guest execution context to include a mapping to the registered code and, after execution of the registered code in the guest execution context, to update the page table entries to remove the mapping to the registered code.

29. The computer program product of claim 26, encoded in at least one computer readable medium selected from the set of a disk, tape or other magnetic, optical or electronic storage medium.

30. The computer program product of claim 26, at least transiently encoded in connection with transmission via a network, wire line, wireless or other communications medium.