| Patent application number | Description | Published |
|---|
| 20090119493 | Using Branch Instruction Counts to Facilitate Replay of Virtual Machine Instruction Execution - A method and computer program product for logging non-deterministic events of a virtual machine executing a sequence guest instructions, the method including tracking an execution point in the sequence of executing guest instructions, the tracking of the execution point including determining a branch count of executed branch instructions; and detecting an occurrence of a non-deterministic event directed to the virtual machine during execution of the sequence of guest instructions, and recording information which includes an identifier of a current execution point, wherein the identifier includes the branch count. | 05-07-2009 |
| 20090248611 | Trace Collection for a Virtual Machine - One embodiment is a computer-implemented method of trace collection for a virtual machine that includes: executing a sequence of instructions from an initial state of the virtual machine; accessing an event log of data relating to nondeterministic events, which data includes an execution point; making at least a portion of the data available to the virtual machine when the sequence reaches the execution point; collecting trace information in response to expansion parameters; and storing the trace information in a trace file. | 10-01-2009 |
| 20090249049 | PRECISE BRANCH COUNTING IN VIRTUALIZATION SYSTEMS - A method for precisely counting guest branch instructions in a virtualized computer system is described. In one embodiment, guest instructions execute in a direct execution mode of the virtualized computer system. The direct execution mode operates at a first privilege level having a lower privilege than a second privilege level. A branch count of previously executed first privilege level branch instructions is maintained as instructions execute. Execution of a first privilege level branch instruction caused by a control transfer to the direct execution mode is detected. Responsive to the detection, a guest branch instruction count is determined based on the first privilege level branch count. | 10-01-2009 |
| 20090327574 | REPLAY TIME ONLY FUNCTIONALITIES - Replay-time-only functionalities in a computer program are executed only during replay in a virtual machine and are skipped outside of replay. If a replay-time-only functionality is detected during the replay of a program execution in a virtual machine, the replay may be paused and the virtual machine state may be saved. The replay-time-only core functionality is executed. When this execution is complete, a prior state of the virtual machine may be restored and the replay may be resumed. | 12-31-2009 |
| 20100005464 | EFFICIENT RECORDING AND REPLAYING OF NON-DETERMINISTIC INSTRUCTIONS IN A VIRTUAL MACHINE AND CPU THEREFOR - The output of a non-deterministic instruction is handled during record and replay in a virtual machine. An output of a non-deterministic instruction is stored to a buffer during record mode and retrieved from a buffer during replay mode without exiting to the hypervisor. At least part of the contents of the buffer can be stored to a log when the buffer is full during record mode, and the buffer can be replenished from a log when the buffer is empty during replay mode. | 01-07-2010 |
| 20100107158 | LOW OVERHEAD FAULT TOLERANCE THROUGH HYBRID CHECKPOINTING AND REPLAY - A virtualized computer system provides fault tolerant operation of a primary virtual machine. In one embodiment, this system includes a backup computer system that stores a snapshot of the primary virtual machine and a log file containing non-deterministic events occuring in the instruction stream of the primary virtual machine. The primary virtual machine periodically updates the snapshot and the log file. Upon a failure of the primary virtual machine, the backup computer can instantiate a failover backup virtual machine by consuming the stored snapshot and log file. | 04-29-2010 |
| 20100318762 | Synchronizing A Translation Lookaside Buffer with Page Tables - The translation lookaside buffer (TLB) of a processor is kept in synchronization with a guest page table by use of an indicator referred to as a âTâ bit. The T bit of the NPT/EPT entries mapping the guest page table are set when a page walk is performed on the NPT/EPT. When modifications are made to pages mapped by NPT/EPT entries with their T bit set, changes to the TLB are made so that the TLB remains in synchronization with the guest page table. Accordingly, record/replay of virtual machines of virtualized computer systems may be performed reliably with no non-determinism introduced by stale TLBs that fall out of synchronization with the guest page table. | 12-16-2010 |
| 20100318991 | Virtual Machine Fault Tolerance - In a computer system running a primary virtual machine (VM) on virtualization software on a primary virtualized computer system (VCS) and running a secondary VM on virtualization software on a secondary VCS, a method for the secondary VM to provide quasi-lockstep fault tolerance for the primary VM includes: as the primary VM is executing a workload, virtualization software in the primary VCS is: (a) causing predetermined events to be recorded in an event log, (b) keeping output associated with the predetermined events pending, and (c) sending the log entries to the virtualization software in the secondary VCS; as the secondary VM is replaying the workload, virtualization software in the secondary VCS is: (a) sending acknowledgements indicating that log entries have been received; (b) when the virtualization software encounters one of the predetermined events, searching the log entries to determine whether a log entry corresponding to the same event was received from the primary VCS, and if so, comparing data associated with the predetermined event produced by the secondary VM with that of the primary VM; if there is a match, the virtualization software in the secondary VCS transmitting an acknowledgement to the virtualization software in the primary VCS; one of the virtualization software in the primary or secondary VCS dropping the event and the other dispatching the output; and if there is no match, performing a checkpoint resynchronization. | 12-16-2010 |
