1. Lecture 13: Virtualization
COSC6376 Cloud Computing
Lecture 13: Virtualization
Instructor: Weidong Shi (Larry), PhD
Computer Science Department
University of Houston

2. Outline Project description Today Some teams have not submitted yet
Virtualization

3. Two technologies for agility
Virtualization:
The ability to run multiple operating systems on a single physical system and share the underlying hardware resources*
Cloud Computing:
“The provisioning of services in a timely (near on instant), on-demand manner, to allow the scaling up and down of resources”**
* VMware white paper, Virtualization Overview
** Alan Williamson, quoted in Cloud BootCamp March 2009

4. The traditional server concept
Web Server
Windows
IIS
App Server
Linux
Glassfish
DB Server
Linux
MySQL
Windows
Exchange

5. The virtual server concept
Virtual Machine Monitor (VMM) layer between Guest OS and hardware

6. Hardware virtual machines (VMs)
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Hardware virtual machines (VMs)
...
App
App
App
VM0
VM1
...
...
App
App
App
App
App
App
Operating System
A new
layer of
software...
Guest OS0
...
Guest OS1
GFX
Physical Host Hardware
VM Monitor (VMM)
Processors
Memory
Graphics
Physical Host Hardware
Network
Storage
Keyboard / Mouse
Without VMs: Single OS owns all hardware resources
With VMs: Multiple OSes share hardware resources
Virtualization enables multiple operating systems to run on the same platform
© 2006 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

7. The virtual server concept
Virtual servers seek to encapsulate the server software away from the hardware
This includes the OS, the applications, and the storage for that server.
Servers end up as mere files stored on a physical box, or in enterprise storage.
A virtual server can be serviced by one or more hosts, and one host may house more than one virtual server.

8. Virtual server migration

9. The virtual server concept
Virtual servers can be scaled out easily.
If the administrators find that the resources supporting a virtual server are being taxed too much, they can adjust the amount of resources allocated to that virtual server
Server templates can be created in a virtual environment to be used to create multiple, identical virtual servers
Virtual servers themselves can be migrated from host to host almost at will.

10. Would you believe ~45 - 50 years?
4/23/2018 1:45 AM
How long has virtualization been around?
Recent development: ~5 years
A while: 10 years
Older than Microsoft: 30 years
A lot longer…..>40 years
Would you believe ~ years?
© 2006 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

11. Intel introduces Intel Virtualization Technology
Strachey: Time Sharing in Large Fast Computers
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Virtualization
Open source Xen
is released
MIT: Project MAC
Connectix is founded
Intel introduces Intel Virtualization Technology
VMWare
is founded
Goldberg: Survey of Virtual Machines Research
Microsoft acquires Connectix
1950
1960
1970
1980
1990
2000
2006
IBM: M44/44X Project
1950’s
IBM & MIT collaborate on the Compatible Time Sharing System (CTSS)
Christopher Strachey publishes a paper titled Time Sharing in Large Fast Computers in the Int’l Conference on Information Processing
1960’s
IBM works on the M44/44X the IBM Watson Research Center evaluating time sharing system concepts based on virtual machines
MIT’s Project MAC begins with a focus on the design and implementation of a better time sharing system
1970’s
Robert P Goldberg authors a paper titled Survey of Virtual Machines Research that describes the shortcomings of typical 3rd generation architectures and multi-programming operating systems
1988
Connectix is founded
1998
VMware is founded
1999
VMware delivers VMware Workstation
2001
VMware delivers VMware GSX Server & VMware ESX Server
2003
Microsoft acquires Connectix to offer virtualization solutions
VMware offers VMware VirtualCenter with VMmotion
University of Cambridge describes Xen in a paper and provides first public release
2004
Intel introduces Intel Virtualization Technology on client & server platforms
2005
IBM & MIT: Compatible Time
Sharing System
© 2006 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

12. Virtualization status
Offerings from many companies
e.g. VMware, Microsoft, Citrix, Oracle ...
Hardware support
Fits well with the move to 64 bit (very large memories) multi-core (concurrency) processors.
Intel VT (Virtualization Technology) provides hardware to support the Virtual Machine Monitor layer
Virtualization is now a well-established technology

13. Virtualization challenges
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Virtualization challenges
Complexity
CPU virtualization requires binary translation or paravirtualization
Must emulate I/O devices in software
Functionality
Paravirtualization may limit supported guest OSes
Guest OSes “see” only simulated platform and I/O devices
Reliability and Security
I/O device drivers run as part of host OS or hypervisor
No protection from errant DMA that can corrupt memory
Performance
Overheads of address translation in software
Extra memory required (e.g., translated code, shadow tables)
© 2006 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

14. Types of virtualization
Container virtualization
Para-virtualization
Full-virtualization

15. Container virtualization
User-space virtual machines
All guests share the same filesystem tree.
Same kernel on all virtual machines
Unprivileged VMs can’t mount drives or change network settings
Provide extra-level of security
Native Speeds, no emulation overhead
OpenVZ, Virtuozzo, Solaris Containers, FreeBSD Jails, Linux-Vserver

16. Paravirtualization Do not try to emulate everything Work as a guard
Pass safe instructions directly to CPU and device
Guests have some exposure to the hardware
Better performance
Need to slightly modify guest OS, but no need to modify applications
Xen, Sun Logical Domains

17. Full virtualization Runs unmodified guests
Simulates bios, communicates with VMs through ACPI emulation, BIOS emulation, sometimes custom drivers
Hardware assisted virtualization

18. Hypervisor-based virtualization
A small virtual machine monitor (known as a hypervisor or VMM) runs on top of machine’s hardware and provides two basic functions.
it identifies, traps, and responds to protected or privileged CPU operations made by each virtual machine.
It handles queuing, dispatching, and returning the results of hardware requests from your virtual machines.
Two type of Hypervisor:
Type 1: native, bare metal
Xen, VMWare ESXi, Hyper-V
Type 2: hosted
VirtualBox, VirtualPC, VMWare Workstation

19. IA32 Protection Rings

20. SW Solution: guest ring deprivileging
Run Guest OS above Ring-0 and have privileged instructions generate faults...
Run VMM in Ring-0 as a collection of fault handlers
Top IA Virtualization Holes :
Ring Aliasing
Running software at a privilege
level other than the level for which
it was written.
Non-trapping instructions
Excessive Faulting
Interrupt Virtualization Issues
Addr Space Compression
Complex Software Techniques :
Source guest OS Modifications
Binary guest OS Modifications
VM0
VM1
...
...
App
App
App
App
App
App
Guest OS0
...
Guest OS1
VM Monitor
Platform Hardware
Virtualization of current IA CPUs
requires complex software workarounds

21. 4/23/2018 1:45 AM
Xen
© 2006 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

22. Reading assignment
Due next Tuesday

23. Xen: introduction Paravirtualization
Need to slightly change some guest OS
Domain (1-) : guest OS

24. Xen: CPU scheduling Guest OS runs at a lower privilege level than Xen
Guest OS must register exception (trap) handlers with Xen
Xen will check the handler
Page fault is handled differently
System calls : no Xen intervention
Use a lightweight event system to handle hardware interrupts

25. Xen: virtual memory management
Paging:
Guest OS has direct read access to hardware page tables.
Updates are batched and validated by the hypervisor
TLB(translation lookaside buffer) flushing
CPU cache of page table entries
Page table
Virtual
Address
Physical
Memory
Address

26. Xen: memory allocation
At the beginning of creating guest OS
A fixed amount of physical memory is allocated (reservation)
Claim additional memory from Xen, when needed; release memory to Xen
Allocated memory are not contiguous
“Physical memory” a virtual view of contiguous memory by guest OS
“hardware memory”: real physical memory

27. Xen: device I/O Only Domain0 has direct access to disks
Other domains need to use virtual block devices
Use the I/O ring
Reorder requests prior to enqueuing them on the ring

28. Xen: network Virtual firewall-router attached to all domains
To send a packet, enqueue a buffer descriptor into the I/O ring

29. Partitioning resources between guest OSes
Memory- preallocated physical memory
Disk – quota
CPU and network
Involves more complicated procedures

30. Domain 0 The representative to the Xen hypervisor
Provide bootstrap code for different types of VMs
Creating/deleting virtual network interfaces and virtual block devices for other domains

31. System looks like