LOGGING AND REPLAYING INPUT/OUTPUT EVENTS FOR A VIRTUAL MACHINE

• US 20090007111A1
• Filed: 06/27/2008
• Published: 01/01/2009
• Est. Priority Date: 06/27/2007
• Status: Abandoned Application

• Current Assignee: VMware, Inc. (Broadcom, Inc.)
• Original Assignee: VMware, Inc. (Broadcom, Inc.)
• Inventors: Venkitachalam, Ganesh, Nelson, Michael
• Application Number:
  US12/163,543
• Publication Number:
  US 20090007111A1
• Time in Patent Office: Days
• US Class Current: 718/1
• CPC Class Codes: G06F 11/1471 involving logging of persistent data for recovery
• CPC Class Codes: G06F 11/3409 for performance assessment
• CPC Class Codes: G06F 11/3476 Data logging G06F11/14, G06F11/2205 take precedence
• CPC Class Codes: G06F 2009/45579 I/O management, e.g. providing access to device drivers or storage
• CPC Class Codes: G06F 2009/45591 Monitoring or debugging support
• CPC Class Codes: G06F 2201/815 Virtual
• CPC Class Codes: G06F 2201/86 Event-based monitoring
• CPC Class Codes: G06F 9/45558 Hypervisor-specific management and integration aspects

Abstract

Methods for logging and replaying input/output (I/O) events for a virtual machine (VM). The I/O events may be asynchronous or synchronous. In particular, one embodiment is a computer-implemented method for logging input/output (I/O) events for a virtual machine, the method including: executing the virtual machine from a checkpoint; and logging external events, including I/O events; wherein logging an I/O event comprises logging the event, and then, logging I/O data relating to the I/O event.

Claims

1. A computer-implemented method for logging input/output (I/O) events for a virtual machine, the method comprising:

executing the virtual machine from a checkpoint; and

logging external events, including I/O events;

wherein logging an I/O event comprises logging the event and logging I/O data relating to the I/O event.

2. The method of claim 1 wherein logging further comprises:

a device emulator allocating an event identifier to an I/O event request from the virtual machine, and associating an event handler with the event identifier;

when an I/O event completion needs to be delivered to the virtual machine, posting an event-request with the event identifier for a virtual machine monitor; and

when the virtual machine monitor processes the event-request, the virtual machine monitor acting by;

stopping the virtual machine, synchronizing a guest virtual CPU state, and then calling the associated event handler function.

3. The method of claim 2 wherein the event handler logs the event, and then logs any data associated with the event.

4. The method of claim 2 wherein the I/O event relates to incoming network packets, the method further comprising:

when a packet is received, posting the event-request for the virtual machine monitor;

when the virtual machine monitor processes the event-request, the virtual machine monitor acting by;

stopping the virtual machine, synchronizing a guest virtual CPU state, and then, calling the associated event handler function; and

the event handler function acting by;

logging the event, receiving the packets, logging their contents, and marking the last packet in the log.

5. The method of claim 1 wherein an I/O event is a direct memory access (DMA) event, the method further comprising:

unmapping DMA buffers from virtual machine address space before an I/O request is posted to physical hardware on which the virtual machine runs; and

remapping the DMA buffers before an I/O completion is posted to the virtual machine.

6. A computer-implemented method for replaying a virtual machine which comprises:

executing the virtual machine from a checkpoint; and

reading external events, including I/O events, from a log;

when an I/O event is encountered in the log, calling a device emulator; and

the device emulator reading all packets in the log, and copying them into memory of the virtual machine.

7. A computer-implemented method of replaying I/O events for a virtual machine, the method comprising:

when the virtual machine issues an I/O request;

logging the I/O request, including an associated identifier;

placing a request descriptor into a request queue; and

issuing the I/O request to an underlying platform;

when the I/O request completes;

deferring I/O completion until a subsequent interrupt; and

when the subsequent interrupt is raised;

stopping the virtual machine;

processing all completions;

finding a corresponding I/O request in the request queue, and

posting the completion to the virtual machine.

8. A computer-implemented method for logging input/output (I/O) events for a virtual machine, the method comprising:

during logging, using a virtual machine monitor and a device emulator so that the virtual machine monitor stops the virtual machine, and the device emulator logs an I/O event; and

during replay, stopping the virtual machine when an I/O event is encountered in a log.

9. The method of claim 8 wherein, during logging, the method further comprises posting the I/O event to the virtual machine.

10. The method of claim 9 wherein, during logging, the method further comprises the device emulator logging contents of the I/O event.

11. The method of claim 8 wherein, during replay, the method further comprises:

before stopping the virtual machine when an I/O event is encountered in a log, placing contents of the I/O event where it cannot be seen by the virtual machine.

12. The method of claim 11 wherein, during replay, the method further comprises, after stopping the virtual machine, making visible the contents of the I/O event to the virtual machine.

13. A computer-implemented method of replaying input/output (I/O) events for a virtual machine, the method comprising:

when the virtual machine issues an I/O request;

logging the I/O request including an associated identifier, placing a request descriptor into a request queue, and issuing the I/O request to an underlying platform;

when the I/O request completes, deferring I/O completion until a subsequent interrupt;

when the subsequent interrupt is raised, stopping the virtual machine;

processing all I/O completions, finding a corresponding I/O request in the request queue, and posting the completion to the virtual machine; and

during the replaying, avoiding issuing an I/O request from the virtual machine since a corresponding result has already been logged.

14. The method of claim 13 further comprising:

when a logged I/O completion entry is encountered, placing it onto a first queue for future use wherein the I/O completion entry comprises a unique identification.

15. The method of claim 14 further comprising:

when any physical I/O completes, notifying an emulator and placing information about the I/O completion into a second queue wherein a unique ID for the I/O request is contained in the queue entry.

16. The method of claim 15 wherein all entries in the first queue are processed upon the stopping of the virtual machine.

17. The method of claim 16 wherein the virtual machine blocks until the I/O completes provided there is no corresponding completion in the first queue with a same unique identification as corresponding to the second queue.

18. A computer readable medium comprising instructions that when executed by a processor implement a method of logging input/output (I/O) events for a virtual machine, the method comprising:

executing the virtual machine from a checkpoint; and

logging external events, including I/O events;

wherein logging an I/O event comprises logging the event and logging I/O data relating to the I/O event.

19. The computer readable medium of claim 18 wherein the method further comprises:

a device emulator allocating an event identifier to an I/O event request from the virtual machine, and associating an event handler with the event identifier;

when an I/O event completion needs to be delivered to the virtual machine, posting an event-request with the event identifier for a virtual machine monitor; and

when the virtual machine monitor processes the event-request, the virtual machine monitor acting by;

stopping the virtual machine, synchronizing a guest virtual CPU state, and then calling the associated event handler function.