Vmware, Inc.

Beng-Hong Lim

Scott W Devine

Edouard Bugnion

Kinshuk Govil

Michael Nelson

Bich Cau Le

According to one aspect of the invention, a request to generate a state checkpoint of a computer is initiated within a user-level software entity, such as a virtual machine. Upon sensing the request, a checkpointing mechanism generates and stores at least one checkpoint, each checkpoint comprising a representation of the total state of the computer system. Upon sensing a state restoration request corresponding to one of the checkpoints, the checkpointing mechanism restores the checkpointed state in the computer, which can then resume operation from the restored total state. According to another aspect of the invention, a total checkpointed state is exported to another computer, where the state can be modified, for example, debugged, and then loaded into either the originally checkpointed computer (which, again, may be a virtual machine), or some other computer.

Mechanism for providing virtual machines for use by multiple users

In a virtualized system running one or more virtual machines on a first hypervisor, a second hypervisor is installed and control of the hardware resources of the physical computer supporting the virtualized system is migrated from the first hypervisor to the second hypervisor without interrupting the operation of the first hypervisor and the virtual machines. Initially a minimal set of hardware resources is hot-removed from control by the first hypervisor, and the second hypervisor is launched on the minimal set of hardware resources. Both the remaining hardware resources and the virtual machines are then migrated from the first hypervisor to the second hypervisor until all the virtual machines have been migrated over to the second hypervisor, while the virtual machines and the first hypervisor continue running largely unaffected by the migration process.

On-line replacement and changing of virtualization software

A computer architecture includes a first operating system (COS), which may be a commodity operating system, and a kernel, which acts as a second operating system. The COS is used to boot the system as a whole. After booting, the kernel is loaded and displaces the COS from the system level, meaning that the kernel itself directly accesses predetermined physical resources of the computer. All requests for use of system resources then pass via the kernel. System resources are divided into those that, in order to maximize speed, are controlled exclusively by the kernel, those that the kernel allows the COS to handle exclusively, and those for which control is shared by the kernel and COS. In the preferred embodiment of the invention, at least one virtual machine (VM) runs via a virtual machine monitor, which is installed to run on the kernel. Each VM, the COS, and even each processor in a multiprocessor embodiment, are treated as separately schedulable entities that are scheduled by the kernel. Mechanisms for high-speed I/O between VM's and I/O devices are also included.

System software displacement in a virtual computer system

Computer configuration for resource management in systems including a virtual machine

A computer system is interrupted, and its entire state information is extracted as one or more checkpoints at one or more respective points during operation of the system. The checkpoint may be restored into the system at any later time, even multiple times, and it may also even be loaded into one or more other systems; all systems loaded with the same checkpoint will then execute from the same checkpointed state. The state extraction mechanism is preferably a virtual machine monitor, on which one or more virtual machines are installed, each virtual machine constituting an encapsulated, virtualized computer system whose states can be checkpointed under control of the virtual machine monitor. Checkpoints may be stored on a portable memory device or transmitted as a batch or dynamically over a network so that even virtual machines installed at different sites may execute from the same state.

Mechanism for restoring, porting, replicating and checkpointing computer systems using state extraction

One or more virtual machines (VM's) run via a virtual machine monitor (VMM) on a hardware platform that has a segmented memory architecture. Each VM has at least one VM descriptor table that has, as entries, VM segment descriptors. At least one VMM descriptor table is established, including at least one shadow descriptor table that stores shadow descriptors for certain of the VM segment descriptors, which are then shadowed descriptors. The VMM compares the shadow descriptors with their respective corresponding shadowed VM descriptors, detects any lack of correspondence between the shadow descriptor table and the corresponding VM descriptor table, and updates and thereby synchronizes each shadow descriptor with its respective shadowed VM descriptor no later than, and preferably only upon the first use of, the respective descriptor by the VM. Whenever the VMM detects any attempt by the VM to load an usynchronized shadowed descriptor, the VMM verifies that the VM is allowed to load it, and then establishes synchronization for the pair of descriptors. One detection mechanism is the tracing of entire memory pages in which VM descriptors are stored; another involves sensing and setting the state of a segment present bit for individual descriptors. The invention improves virtualization performance by reducing the number of descriptors that need to be kept coherent. The VMM also has a flexible mechanism to invalidate descriptors, for example, when the VM unmaps or remaps the memory page it is located in, or when the VM sets a new segment descriptor table.

Growing community of inventors

Atherton, CA, United States of America

Beng-Hong Lim