Virtual machines and their architecture

Technical Seminar on VMs and their Architecture

1. SREENIDHI INSTITUTE OF SCIENCE AND TECHNOLOGY (Autonomous Institution, approved by UGC and Accredited by NAAC with ‘A’ Grade) TECHNICAL SEMINAR Presented by… Mrinmoy Dalal CSE A (13311A0506)

2. Can a “small” operating system simulate the hardware of some machine so that: Another operating system can run in that simulated hardware? More than one instance of that operating system run on the same hardware at the same time? More than one different operating system can share the same hardware at the same time? Question

3. VIRTUAL MACHINES

4. VIRTUALIZATION Virtualization is an abstraction layer that decouples the physical hardware from the operating system to deliver greater IT resource utilization and flexibility. It allows multiple virtual machines, with heterogeneous operating systems to run in isolation, side-by-side on the same physical machine. Virtualization hides the physical characteristics of computing resources from their users, be they applications, or end users.

5. Normal Computer System Virtualized Computer System

6. HYPERVISOR Hypervisor is a software program that manages multiple operating systems (or multiple instances of the same operating system) on a single computer system. The hypervisor manages the system's processor, memory, and other resources to allocate what each operating system requires. Hypervisors are designed for a particular processor architecture and may also be called Virtualization managers .

7. WHAT is a Virtual Machine?

8. „A machine is a tool that consists of one or more parts, and uses energy to achieve a particular goal.“ -WIKIPEDIA

9. „A virtual machine ( VM) is a simulation of a machine (abstract or real) that is usually different from the target machine (where it is being simulated on).“ -WIKIPEDIA

10. The resources of the physical computer are shared to create the virtual machines CPU scheduling can create the appearance that each user has own processor Spooling and a file system provide virtual card readers, virtual line printers Disk partitioned to provide virtual disks A normal user time-sharing terminal serves as the virtual machine operator’s console

11. Non Virtual Machine Virtual Machine

12. Virtual-machine concept provides complete protection of system resources Each virtual machine is isolated from all other virtual machines. However, no direct sharing of resources Virtual-machine system is a good vehicle for operating-systems research and development. System development is done on the virtual machine does not disrupt normal operation Multiple concurrent developers can work at same time The virtual machine concept is difficult to implement due to the effort required to provide an exact duplicate to the simulated machine

13. VM COMPATIBILITY Hardware Independent Physical hardware hidden by the virtualization layer . Create Once, Run Anywhere No Configuration Issues Migrate VMs between Hosts Legacy VMs Run Ancient OS on new platform Eg : DOS

14. EXAMPLE – PAGE TABLES Suppose guest OS has its own page tables Then virtualization layer must Copy those tables to its own Trap every reference or update to tables and simulate it During page fault Virtualization layer must decide whether fault belongs to guest OS or self If guest OS , must simulate a page fault Likewise, virtualization layer must trap and simulate every privileged instruction in machine!

15. Some hardware architectures or features are impossible to virtualize Certain registers or state not exposed Unusual devices and device control Clocks, time, and real-time behavior

16. VIRTUAL MACHINE MONITOR Virtual machine monitor (VMM) or hypervisor is software that supports VMs. It determines how to map virtual resources to physical ones Physical resource may be time-shared, partitioned, or emulated in software. VMM much smaller than a traditional OS ( Isolation portion of a VMM is  10,000 lines of code),

17. MAIN CONCERN OF VMM Biggest problem faced by the VMM is to present the hardware to the VM in a “safe, transparent and efficient way” Safe: whatever the VM does, it should not be able to affect other VM’s or the VMM Maintain illusion by tricking the software into thinking it has the hardware to itself and by hiding the true state of the hardware

18. ATTRIBUTES OF VMM Encapsulation VMM manages both software and hardware thus giving it the ability to manage the hardware resources as well as manipulate and control software stack Performance Overhead is generally transparent for most workloads, only slowdowns occur for isolation or maintain the transparent illusion of hardware usage levels

19. Programmers really love to make it complicated ...

20. Types Of Virtual Machines

21. HARDWARE LEVEL VIRTUALIZATION Virtualization layer sits right on top of the real hardware Since the VM presents a version the real machine, all software written for that hardware (x86) will run on that virtual machine Original design from IBM in the 1960’s

22. OPERATING SYSTEM LEVEL VIRTUALIZATION Virtualization layer sit between the operating system and the application programs that run on the operating system Virtual Machine runs applications, or sets of applications written for the operating system but in a controlled environment use host OS API Real Machine OS VMM Virtual Machine Application Applications

23. HIGH-LEVEL LANGUAGE VIRTUAL MACHINES The virtualization layer sits as an application program on top of the operating system Can run any programs written for that virtual machine abstraction regardless of the operating system hosting that virtual machine Anyone have an example of this? Real Machine OS JVM Java Byte Code Applications -Java

24. WITH GREAT POWER COMES GREAT EXPLOITS

25. ATTRIBUTES OF ALL VIRTUAL MACHINES (1) Software Compatibility VM provides compatible abstraction so all software written for the machine that VM is virtualizing will run on it Java: “write once, run anywhere” Isolation All software running on the virtual machine is contained within it and can’t affect other VM’s or processes

26. ATTRIBUTES OF ALL VIRTUAL MACHINES (2) Encapsulation Virtual machines provide a level of indirection. Any software running within them can be controlled and manipulated. Can act like putting a filter on a print service to monitor content or perform additional book keeping. Java VM for example can perform run time error checking and garbage collection that C++ compiled code can’t do running directly on the hardware Performance Any new software layer adds overhead to system

27. IMPORTANT USES OF VMs (1) Multiple OSes No more dual boot! Can even transfer data (e.g., cut-and-paste) between VMs Protection Crash or intrusion in one OS doesn’t affect others Easy to replace failed OS with fresh, clean one

28. IMPORTANT USES OF VMs (2) 3. Software Management VMs can run complete SW stack, even old OSes like DOS Run legacy OS, stable current, test release on same HW 4. Hardware Management Independent SW stacks can share HW Run application on own OS (helps dependability) Migrate running VM to different computer To balance load or to evacuate from failing HW

29. To Sum Up… Virtual machines are a number of discrete identical execution environments on a single computer, each of which runs an operating system. This can allow applications written for one OS to be executed on a machine which runs a different OS which provide a greater level of isolation between processes than is achieved when running multiple processes on the same instance of an OS.