A Virtual Machine Monitor( VMM) also known as a Hypervisor consists of software that controls the execution of multiple guest operating systems on a single physical machine. It is a thin software layer that exports a virtual machine abstraction. The abstraction looks enough like the hardware that any software written for that hardware will run in the virtual machine. The VMM provides each guest the appearance of full control over a complete computer system (memory, CPU, and all peripheral devices). Fundamentally, a VMM works by intercepting and emulating in a safe manner sensitive operations in the guest (such as changing the page tables, which could give a guest access to memory it is not allowed to access).
There are numerous techniques for implementing virtualization. Until the recent arrival of Intel and AMD hardware support, x86 - the wold's most popular architecture was very hostile towards virtualization. Complicated Software workarounds were developed to virtualize x86 machines, but not without the associated overhead. Hardware virtualization, though immature at present, represents the future of virtualization. This is the inspiration behind the HVMM design.
The HVMM is designed to run on machines with AMD-V hardware virtualization support codenamed “Pacifica”. The AMD Secure Virtual Machine (SVM) architecture provides hardware assists to improve performance and facilitate implementation of virtualization.
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