Question

1. When executed with a VM on a modern hypervisor providing full hardware virtualization, what happens when a guest OS executes a privileged instruction of this sort? Explain your answer? (5 Points) Describe the difference of full virtualization and para-virtualization, and their advantages. (5 Points)

1.a) When executed with a VM on a modern hypervisor providing full hardware
virtualization, what happens
when a guest OS executes a privileged instruction of this sort? Explain
your answer?

b) Describe the difference of full virtualization and para-virtualization,
and their advantages.

Answer 1

1. a) Hardware assisting processors give the guest OS the authority it needs to have direct access to platform resources without sharing control of the hardware. Previously, the Virtual machine had to emulate the hardware to the guest OS while it retained control of the physical platform.

These new processors give both the VM and the guest OS the authority each needs to run without hardware emulation or OS modification. Hardware assisted processors, all of which support 64-bit processing, now allow the benefits of 64-bit computing to filter up to the guest OS and its hosted applications. This provides virtual machines with greater capabilities.

b)

Full Virtualization	Para Virtualization
It doesn't require hardware or OS assistance to virtualize system operations.	It completely depends upon the direct communication between the guest kernel and the underlying hypervision.
Runs unmodified off the shelf guests	Guest OS and drivers must be modified to run.
It enables admins to run applications on an isolated guest OS.	It provides easier backups, faster migrations, reduced power consumption and improved server consolidation.
It enables OS to emulate new hardware, which can improve security and productivity of a system.	It doesn't fully rebuild the hardware which can significantly reduce virtualization.

Advantage of Full Virtualization :

• Most operating systems can be installed without any modification.
• Provides complete isolation of each virtual machine.
• Provides near-native CPU and memory performance.
• Uses sophisticated techniques to trap and emulate instructions in runtime.

Advantage of Para Virtualization :

• When no hardware assistance is available, para virtualized guests tend to be the highest performing virtual machines for network and disk I/O.
• Easier to implement than full virtualization.