Virtual Machine-Preserving Host Updates

• US 20140157264A1
• Filed: 12/04/2012
• Published: 06/05/2014
• Est. Priority Date: 12/04/2012
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Russinovich, Mark Eugene, Raghuraman, Melur K.
• Granted Patent: US 9,110,762 B2
• Time in Patent Office: Days
• US Class Current: 718/1
• CPC Class Codes: G06F 2009/45575 Starting, stopping, suspending or resuming virtual machine instances
• CPC Class Codes: G06F 8/63 Image based installation; Cloning; Build to order
• CPC Class Codes: G06F 8/65 Updates security arrangements therefor G06F21/57
• CPC Class Codes: G06F 8/656 while running
• CPC Class Codes: G06F 9/44 Arrangements for executing specific programs
• CPC Class Codes: G06F 9/455 Emulation; Interpretation; Software simulation, e.g. virtualisation or emulation of application or operating system execution engines
• CPC Class Codes: G06F 9/45533 Hypervisors; Virtual machine monitors
• CPC Class Codes: G06F 9/45545 Guest-host, i.e. hypervisor is an application program itself, e.g. VirtualBox

Abstract

Techniques are described for updating a host operating system on a server while maintaining virtual machines running on the server. An updated host operating system is copied to the server. The currently active host operating system freezes the virtual machines but leaves them resident in RAM. The allocations and state for each virtual machine is copied to RAM or local storage. The active host operating system is shut down. Instead of issuing a command to reboot the server after it finishes shutting down, the active host operating system transfers execution to a loader. The loader reads the kernel of the updated host operating system into RAM along with an allocation map for the virtual machines and instructions to resume the virtual machines. The loader transfers execution to the updated host operating system entry point, and the updated host operating system loads the states of the virtual machines and resumes them.

Claims

1. A computer-implemented method, comprising:

receiving a copy of an updated host operating system on a computer system;

suspending all virtual machines running on the computer system;

recording an allocation map and state for each of the virtual machines;

transferring execution from the active host operating system to a loader;

reading a kernel of updated host operating system into RAM via the loader;

loading the allocation map and state for each of the virtual machines; and

resuming operation of the virtual machines by the updated host operating system.

2. The computer-implemented method of claim 1, further comprising:

leaving the virtual machines resident in RAM when the virtual machines are suspended.

3. The computer-implemented method of claim 1, further comprising:

recording the allocation map and state for the virtual machines to RAM or to local storage.

4. The computer-implemented method of claim 1, wherein transferring execution from the active host operating system to the loader further comprises:

shutting down the active host operating system.

5. The computer-implemented method of claim 4, further comprising:

transferring execution from the active host operating system to the loader as part of the active host operating system shut down, wherein the loader executes in place of rebooting the computer system.

6. The computer-implemented method of claim 1, wherein loading the allocation map and state for each of the virtual machines further comprises:

loading instructions to resume the virtual machines.

7. The computer-implemented method of claim 1, further comprising:

maintaining virtual machine caches while the virtual machines are suspended.

8. A computer system, comprising:

a processor;

system memory;

one or more computer-readable storage media having stored thereon computer-executable instructions that, when executed by the processor, causes the processor to perform a method for updating a host operating system, the processor operating to;

load an updated host operating system to the system memory;

suspend virtual machines running on the computer system;

store an allocation map and state for each of the virtual machines to the system memory;

shut down the active host operating system;

transfer execution from the active host operating system to a loader;

load a kernel of updated host operating system into the system memory via the loader;

initialize the updated host operating system;

load the allocation map and state for each of the virtual machines; and

resume operation of the virtual machines by the updated host operating system.

9. The computer system of claim 8, the processor further operating to:

maintaining the virtual machines resident in system memory when the virtual machines are suspended.

10. The computer system of claim 8, wherein the system memory is RAM.

11. The computer system of claim 8, the processor further operating to:

transfer execution from the active host operating system to the loader as part of the active host operating system shut down, wherein the loader executes in place of rebooting the computer system.

12. The computer system of claim 8, wherein loading the allocation map and state for each of the virtual machines further comprises:

loading instructions to resume the virtual machines.

13. The computer system of claim 8, the processor further operating to:

maintain virtual machine caches while the virtual machines are suspended.

14. The computer system of claim 8, wherein the computer system is a resource on a distributed computing environment, and wherein the updated host operating system is loaded from the distributed computing environment.

15. A computer program product for implementing a method for updating a host operating system, the computer program product comprising one or more computer-readable storage media having stored thereon computer-executable instructions that, when executed by one or more processors of a computer system, cause the computer system to perform the method comprising:

receiving an updated host operating system;

suspending all virtual machines running on the computer system;

recording an allocation map and state for each of the virtual machines;

transferring execution from the active host operating system to a loader;

reading a kernel of updated host operating system into RAM via the loader;

loading the allocation map and state for each of the virtual machines; and

resuming operation of the virtual machines by the updated host operating system.

16. The computer program product of claim 15, the method further comprising:

leaving the virtual machines resident in RAM when the virtual machines are suspended.

17. The computer program product of claim 15, the method further comprising:

recording the allocation map and state for the virtual machines to RAM or to local storage.

18. The computer program product of claim 15, wherein transferring execution from the active host operating system to the loader further comprises:

shutting down the active host operating system.

19. The computer program product of claim 15, the method further comprising:

transferring execution from the active host operating system to the loader as part of the active host operating system shut down, wherein the loader executes in place of rebooting the computer system.

20. The computer program product of claim 15, wherein loading the allocation map and state for each of the virtual machines further comprises:

loading instructions to resume the virtual machines.