BACKGROUND

The updating of host operating systems traditionally requires a reboot and therefore workload downtime. For virtualization hosts running virtual machine (VM) instances, downtime also implies downtime of the workloads in hosted virtual machines. Virtualization technology often allows running VM contexts to be preserved by pausing execution of VMs and writing their associated RANI contexts to disk. However, such operations are typically relatively slow and result in detectable outages, especially where the storage subsystem is slow or the amount of memory to be preserved and therefore the amount of 10 required would be very large.

In some update operations, rather than writing VM memory contents to disk, the host memory pages used for VM memory are catalogued such that the virtualization software can reassemble the state of VMs across the update operation. During the update operation, the current operating system catalogues the VM artifacts, tears down the VM, prepares the new software for execution, unloads the current software, and loads the updated software which reads the meta-data and reconstructs the VMs using the same memory pages as previously used. While this can be faster than writing memory contents to disk, the duration of the operation and therefore the window of downtime is still negatively affected by several factors, including: 1) the quantity and continuity of memory to be preserved 2) the destruction (including un-mapping) and re-construction (including re-mapping) of VM artifacts, especially the guest to host page mappings. In addition, VM instances which have assigned devices cannot participate in the update operation because assigned device cannot be paused or quiesced across the operation nor can their state be saved and restored.

The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced.

BRIEF SUMMARY

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

At least one embodiment disclosed herein is related to computing systems and methods for performing a servicing operation on a virtual machine (VM). A computing system has first virtual machine components and second VM components that remain loaded in computing system physical hardware during the servicing operation. An operation of a VM running the first and second VM components is suspended so that the servicing operation for the VM can be performed. The VM has devices that are directly attached to it. A state of the first VM components is saved. An identification pointer for the second VM components is saved in a portion of the computing system physical memory without removing any underlying data structures of the second VM components from the computing system physical hardware. The directly attached devices remain configured as attached to the VM and configured to be in communication with the VM while the VM is suspended and while the servicing operation is performed. The first VM components are shut down and then restored at the completion of the servicing operation using the saved state. The restored first VM components are reconnected to the second VM components using the identification pointers. The operation of the VM is restored.

Additional features and advantages will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the teachings herein. Features and advantages of the invention may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. Features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.

