What is full virtualization, paravirtualization?

Question

Virtualization

Can you explain in simple terms what full virtualization is, and what paravirtualization is (this is what interests you the most) and what is their difference?
PS in Google it is difficult to write, I do not fully understand ...

Answer 1

Vitualization is a process that completely emulates a "computer", with a processor, memory, a set of hardware, from a video card to hard drives. In virtualization, we are completely placed in a closed box, from which, theoretically, nothing sticks out.
In the case of full virtualization, the devices of the virtual machine completely emulate the operation of the hardware, down to registers, memory, etc. In this case, the internal program practically does not suspect any substitution.
Paravirtualization, the same as in the previous case, but some components, such as network or disk (and other) devices, can be accessed directly through calls outside the virtual machine (with some reservations). To work with paravirtualized hardware, separate drivers and program calls are needed.
Paravirtualization is generally faster because there is no overhead for unnecessary emulation.
This is in a simple way.

Answer 2

Full virtualization is based on virtualization mechanisms built into the op process
. Paravirtualization is based on software emulation.

Answer 3

paravirtualization (this is what interests me the most)

A virtual machine is a kind of design solution in the camp of operating systems. Monolithic, multilevel, client-server, micronuclear, exonuclear in the same place.
(according to Tonenbaum) To run virtual machine software, the CPU must be ready to run in this mode /virtualization/. When an operating system running in a virtual machine (in user mode) executes privileged instructions, such as changing the program status word (PSW) or an I/O operation, the hardware needs to intercept those instructions and invoke the virtual machine monitor to emulate them in software. .
So one of the approaches to processing these instructions is to modify the operating system (virtualized) in order to remove them. This approach is just paravirtualization.
In short, the OS is modified in order to cut out everything that may not be supported by the equipment with all the ensuing consequences.