CS-3310 - 07 Virtualization - Basics

Why do organizations use multiple virtual machines instead of one big server?

Isolation, reliability, and flexibility.

What is a VMM or hypervisor?

Software creating multiple virtual machines.

What is the key idea of virtualization?

One machine emulates many separate machines.

Why does virtualization improve reliability?

Failures in one VM don't affect others.

Why is a hypervisor more reliable than a full OS?

Smaller code base; fewer bugs.

What is sandboxing used for?

Keeping services isolated for security.

Why is virtualization useful for running multiple OSs?

Each VM can run a different OS.

How does virtualization save costs?

Fewer physical machines needed.

What is checkpointing in virtualization?

Saving a VM's state for later restoration.

What is migration?

Moving a VM between physical hosts.

What is one major use case for virtualization today?

Cloud computing.

What are the cloud's advantages?

On-demand resources and cost efficiency.

Who developed early virtual machine systems?

IBM (SIMMON, CP-40, CP/CMS).

What did Popek and Goldberg define?

Conditions for efficient virtualization.

Why couldn't early x86 CPUs support classical virtualization?

Sensitive instructions didn't always trap.

What are the three virtualization requirements?

Safety, fidelity, efficiency.

What is safety in virtualization?

Hypervisor must control all hardware access.

What is fidelity?

Programs behave as if running on real hardware.

What is efficiency?

Most instructions run without hypervisor intervention.

What are privileged instructions?

Instructions that trap when run in user mode.

What are sensitive instructions?

Instructions that behave differently depending on mode.

What was the virtualization problem on x86 before 2005?

Sensitive not subset of privileged instructions.

What are Intel VT and AMD SVM?

Hardware virtualization extensions.

How do VT/SVM help virtualization?

Force sensitive instructions to trap.

What is trap-and-emulate virtualization?

Hypervisor intercepts privileged operations and emulates them.

What is binary translation?

Replacing problematic instructions at runtime.

Why use binary translation even with VT?

Performance optimization.