Week 14: Virtualization

Question 1

Virtualization :

Answer 1

the ability for a computer to run multiple operating systems on the
same physical machine

Question 2

Host :

Answer 2

the underlying physical machine hardware

Question 3

Virtual machine manager or hypervisor

Answer 3

software that allows creating and
running virtual machines on the host machine; the VM’s each then run with their
own operating systems and applications; the VMM manages the computing,
memory, and storage resources required for the VMs

Question 4

Guest operating system

Answer 4

user-level process that usually runs an operating

system over the VMM hypervisor

Question 5

Host operating system

Answer 5

the OS that runs on the hardware (for a type 2

hypervisor)

Question 6

Type 0 hypervisor :

Answer 6

a hypervisor that’s implemented in firmware or hardware;

hardware is statically partitioned across different guest operating systems

Question 7

Type 1 hypervisor:

Answer 7

the hypervisor itself essentially replaces the operating
system and runs in kernel mode; the guest OS believes it is running on bare
metal

Question 8

Type 2 hypervisor:

Answer 8

the VMM hypervisor runs on top of the host operating

system in user mode as a process; the host doesn’t know that the VMM is running guest OSes

Question 9

Sandboxing :

Answer 9

a type of virtualization in which a tightly controlled environment
with a guest operating system and isolated set of resources is created, to allow untested, unverified, or untrusted programs to run; This technique helps maintain
security for the host machine or host operating system

Question 10

VM templating :

Answer 10

create an operating system and application image, and clone it
across multiple machines, saving installation the effort of doing manual software
installations

Question 11

Virtual CPU:

Answer 11

a software emulation of a CPU that represents the state of the CPU
(including the PCB and execution state) for each of the guest operating systems

Question 12

Trap and emulate :

Answer 12

when the guest OS of the VM attempts to execute a
privileged instruction, since it is in user mode, the action will cause a “trap”; the
VMM will handle the trap and execute the instruction attempted by the guest,
then return control to the guest in user mode

Question 13

● Binary translation :

Answer 13

alternative to trap and emulate in which instead of doing
trap-and-emulate for every instruction that runs in the guest operating system,
the guest OS instructions are translated on the fly to equivalent instructions in the
VMM. The original assembly code from the guest OS is simply translated to code
for the equivalent implementation in the VMM

Question 14

CPU scheduling for virtualization:

Answer 14

given multiple VCPUs and physical CPUs,

the scheduling algorithm decides which VCPU to run next on a given CPU

Question 15

Memory management for virtualization:

Answer 15

Guest page table:
Host page table :
Shadow page table :

Question 16

Shadow page table :

Answer 16

maintained by the VMM to map guest virtual
addresses to host physical addresses, optimizing the translation process
to manage virtualization; the shadow page table is loaded into the MMU
during a context switch

Question 17

Host page table

Answer 17

the guest physical addresses are separately mapped to
host virtual addresses; the host page table maps the host virtual
addresses to the host physical addresses

Question 18

Guest page table:

Answer 18

maps the guest OS’s virtual addresses to what the

guest OS believes to be physical addresses

Question 19

Full virtualization:

Answer 19

the guest OS is unaware of the hypervisor and believes it is running on bare metal

Question 20

Paravirtualization:

Answer 20

the guest OS is aware of the underlying hypervisor and thus implements optimizations given this knowledge; the shadow page table and
efficient I/O techniques are examples of paravirtualization

Question 21

Efficient I/O :

Answer 21

circular buffer maintains all the intermediate I/O state
between the guest and the VMM through shared memory which results in
much better performance than dealing with the levels of indirection
between the guest OS and physical device

Question 22

Application containment

Answer 22

containerization is an alternative to full virtualization
that allows isolating individual applications; the different containers run on the host operating system and have standard formats; the container virtualization
layer allows the containers to communicate and abstracts the specific host OS from the application containers

Question 23

Microservices :

Answer 23

complicated applications are broken down into modular

components called microservice; each service is its own process

Question 24

Programming environment virtualization:

Answer 24

a custom environment designed for a programming language that includes features that enable optimized execution (e.g. Java Virtual Machine)