Virtual Machine Hardware

Virtual Machine Hardware

1. Types of VMH

   • Full Virtualization
     • VMM decouples guest OS from the underlying physical hardware
     • Guest OS is not aware of being virtualized
     • virtualization technique used to provide a VME that completely simulates the underlying hardware
     • runs in Ring 0
   • Paravirtualization
     • Guest OS knows that it is virtualized
     • Modified guest OS kernel is used
       • Linux
       • OpenBSD
     • a virtualization technique that presents a software interface to the virtual machines which is similar, yet not identical to the underlying hardware–software interface
   • Hardware Assisted Virtualization
     • hypervisor-aware CPU to handle privileged instructions
     • Advantage
       • Reduces overhead caused due to full and paravirtualization
       • CPU and Memory virtualization support is provided in hardware
     • a platform virtualization approach that enables efficient full virtualization using help from hardware capabilities, primarily from the host processors.

2. Components

   • vCPU
   • vRAM
   • Virtual Disk
   • Virtual Network Adaptor

3. NEEDS

   • need to place virtual layer below the OS layer

4. Rings

   • The x86 family of CPUs provide a range of protection levels also known as rings in which code can execute.
   • Ring 0 has the highest level privilege and it is in this ring that the operating system kernel normally runs
   • User applications run in Ring 3