Monday, August 8, 2011

Hardware virtualization layer

The hardware virtualization layer is created by installing Microsoft Hyper-V on one or more compatible hardware platforms. Hyper-V, Microsoft’s entry into the hypervisor market, is a very thin layer that presents a small attack surface. It can do this because Microsoft does not embed drivers. Instead, Hyper-V uses vendor-supplied drivers to manage VM hardware requests.

Each VM exists within a partition, starting with the root partition. The root partition must run Windows 2008 Server _64 or Windows 2008 Server Core _64. Subsequent partitions, known as child partitions, usually communicate with the underlying hardware via the root partition. Some calls directly from a child partition to Hyper-V are possible using WinHv (defined below) if the OS running in the partition is “enlightened.” An enlightened OS understands how to behave in a Hyper-V environment. Communication is limited for an unenlightened OS partition, and applications there tend to run much more slowly than those in an enlightened one. Performance issues are generally related to the requirement for emulation software to interface hosted services.

The Hyper-V components responsible for managing VM, hypervisor, and hardware communication are the VMBus, VSCs, and VSPs. These and other Hyper-V components.

» Advanced Programmable Interrupt Controller (APIC)—An APIC allows priority levels to be assigned to interrupt outputs.

» Hypercalls—Hypercalls are made to Hyper-V to optimize partition calls for service. An enlightened partition may use WinHv or UnixHv to speak directly to the hypervisor instead of routing certain requests through the root partition.

» Integration Component (IC)—An IC allows child partitions to communicate with other partitions and the hypervisor.

» Memory Service Routine (MSR)

» Virtualization Infrastructure Driver (VID)—The VSD provides partition management services, virtual processor management services, and memory management services.

» VMBus—The VMBus is a channel-based communication mechanism. It enables interpartition communication and device enumeration. It is included in and installed with Hyper-V Integration Services.

» Virtual Machine Management Service (VMMS)—The VMMS is responsible for managing VM state associated with all child partitions. A separate instance exists for each VM.

» Virtual Machine Worker Process (VMWP)—The VMWP is a user-mode component of the virtualization stack. It enables VMMSs for the root partition so it can manage VMs in the child partitions.

» Virtualization Service Client (VSC)—The VSC is a synthetic device instance residing in a child partition. It uses hardware resources provided by VSPs. A VSC and VSP communicate via the VMBus.

» Virtualization Service Provider (VSP)—The VSPs reside in the root partition. They work with VSCs to provide device support to child partitions over the VMBus.

» Windows Hypervisor Interface Library (WinHv)—The WinHv is a bridge between a hosted operating system’s drivers and the hypervisor. It allows drivers to call the hypervisor using standard Windows calling conventions when an enlightened environment is running within the partition.

» Windows Management Instrumentation (WMI)—The WMI exposes a set of APIs for managing virtual machines.

Source of Information : Elsevier-Microsoft Virtualization Master Microsoft Server Desktop Application and Presentation

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