The Definitive Guide to the Xen Hypervisor

by Chisnall, David

• ISBN13: 9780133582499
• ISBN10: 0133582493
• Edition: 1st
• Format: Paperback
• Copyright: 2007-11-09
• Publisher: PEARSO

Summary

“The Xen hypervisor has become an incredibly strategic resource for the industry, as the focal point of innovation in cross-platform virtualization technology. David’s book will play a key role in helping the Xen community and ecosystem to grow.”

–Simon Crosby, CTO, XenSource

 

An Under-the-Hood Guide to the Power of Xen Hypervisor Internals

 

The Definitive Guide to the Xen Hypervisor  is a comprehensive handbook on the inner workings of XenSource’s powerful open source paravirtualization solution. From architecture to kernel internals, author David Chisnall exposes key code components and shows you how the technology works, providing the essential information you need to fully harness and exploit the Xen hypervisor to develop cost-effective, highperformance Linux and Windows virtual environments.

 

Granted exclusive access to the XenSource team, Chisnall lays down a solid framework with overviews of virtualization and the design philosophy behind the Xen hypervisor. Next, Chisnall takes you on an in-depth exploration of the hypervisor’s architecture, interfaces, device support, management tools, and internals—including key information for developers who want to optimize applications for virtual environments. He reveals the power and pitfalls of Xen in real-world examples and includes hands-on exercises, so you gain valuable experience as you learn.

 

This insightful resource gives you a detailed picture of how all the pieces of the Xen hypervisor fit and work together, setting you on the path to building and implementing a streamlined, cost-efficient virtual enterprise.

 

Coverage includes

·         Understanding the Xen virtual architecture

·         Using shared info pages, grant tables, and the memory management subsystem

·         Interpreting Xen’s abstract device interfaces

·         Configuring and managing device support, including event channels, monitoring with XenStore, supporting core devices, and adding new device types

·         Navigating the inner workings of the Xen API and userspace tools

·         Coordinating virtual machines with the Scheduler Interface and API, and adding a new scheduler

·         Securing near-native speed on guest machines using HVM

·         Planning for future needs, including porting, power management, new devices, and unusual architectures

 

Author Biography

David Chisnall is a regular columnist for InformIT and is nearing completion of a Ph.D. in computer science from the University of Wales. He cofounded and actively contributes to the open source Étoilé desktop environment, participated in a Knowledge Transfer Project, and has jumped enthusiastically into numerous other in-the trenches tech adventures.

Table of Contents

>List of Figures xi

List of Tables xiii

Foreword xv

Preface xvii

 

Part I: The Xen Virtual Machine 1

 

Chapter 1: The State of Virtualization 3

1.1 What Is Virtualization? 3

1.2 Why Virtualize? 7

1.3 The First Virtual Machine 8

1.4 The Problem of x86 9

1.5 Some Solutions 9

1.6 The Xen Philosophy 15

1.7 The Xen Architecture 16

 

Chapter 2: Exploring the Xen Virtual Architecture 27

2.1 Booting as a Paravirtualized Guest 27

2.2 Restricting Operations with Privilege Rings 28

2.3 Replacing Privileged Instructions with Hypercalls 30

2.4 Exploring the Xen Event Model 33

2.5 Communicating with Shared Memory 34

2.6 Split Device Driver Model 35

2.7 The VM Lifecycle 37

2.8 Exercise: The Simplest Xen Kernel 38

 

Chapter 3: Understanding Shared Info Pages 47

3.1 Retrieving Boot Time Info 47

3.2 The Shared Info Page 51

3.3 Time Keeping in Xen 53

3.4 Exercise: Implementing gettimeofday() 54

 

Chapter 4: Using Grant Tables 59

4.1 Sharing Memory 59

4.2 Device I/O Rings 65

4.3 Granting and Revoking Permissions 66

4.4 Exercise: Mapping a Granted Page 69

4.5 Exercise: Sharing Memory between VMs 71

 

Chapter 5: Understanding Xen Memory Management 75

5.1 Managing Memory with x86 75

5.2 Pseudo-Physical Memory Model 78

5.3 Segmenting on 32-bit x86 80

5.4 Using Xen Memory Assists 82

5.5 Controlling Memory Usage with the Balloon Driver 84

5.6 Other Memory Operations 86

5.7 Updating the Page Tables 89

5.8 Exercise: Mapping the Shared Info Page 95

 

Part II: Device I/O 97

 

Chapter 6: Understanding Device Drivers 99

6.1 The Split Driver Model 100

6.2 Moving Drivers out of Domain 0 102

6.3 Understanding Shared Memory Ring Buffers 103

6.4 Connecting Devices with XenBus 109

6.5 Handling Notifications from Events 111

6.6 Configuring via the XenStore 112

6.7 Exercise: The Console Device 112

 

Chapter 7: Using Event Channels 119

7.1 Events and Interrupts 119

7.2 Handling Traps 120

7.3 Event Types 123

7.4 Requesting Events 124

7.5 Binding an Event Channel to a VCPU 127

7.6 Operations on Bound Channels 128

7.7 Getting a Channel’s Status 129

7.8 Masking Events 130

7.9 Events and Scheduling 132

7.10 Exercise: A Full Console Driver 133

 

Chapter 8: Looking through the XenStore 141

8.1 The XenStore Interface 141

8.2 Navigating the XenStore 142

8.3 The XenStore Device 145

8.4 Reading and Writing a Key 147

8.5 Other Operations 158

 

Chapter 9: Supporting the Core Devices 161

9.1 The Virtual Block Device Driver 161

9.2 Using Xen Networking 169

 

Chapter 10: Other Xen Devices 177

10.1 CD Support 177

10.2 Virtual Frame Buffer 178

10.3 The TPM Driver 183

10.4 Native Hardware 184

10.5 Adding a New Device Type 187

 

Part III: Xen Internals 195

 

Chapter 11: The Xen API 197

11.1 XML-RPC 198

11.2 Exploring the Xen Interface Hierarchy 200

11.3 The Xen API Classes 201

11.4 The Function of Xend 206

11.5 Xm Command Line 208

11.6 Xen CIM Providers 209

11.7 Exercise: Enumerating Running VMs 210

11.8 Summary 215

 

Chapter 12: Virtual Machine Scheduling 217

12.1 Overview of the Scheduler Interface 218

12.2 Historical Schedulers 219

12.3 Using the Scheduler API 224

12.4 Exercise: Adding a New Scheduler 229

12.5 Summary 233

 

Chapter 13: HVM Support 235

13.1 Running Unmodified Operating Systems 235

13.2 Intel VT-x and AMD SVM 237

13.3 HVM Device Support 239

13.4 Hybrid Virtualization 240

13.5 Emulated BIOS 244

13.6 Device Models and Legacy I/O Emulation 245

13.7 Paravirtualized I/O 246

13.8 HVM Support in Xen 248

 

Chapter 14: Future Directions 253

14.1 Real to Virtual, and Back Again 253

14.2 Emulation and Virtualization 254

14.3 Porting Efforts 255

14.4 The Desktop 257

14.5 Power Management 259

14.6 The Domain 0 Question 261

14.7 Stub Domains 263

14.8 New Devices 264

14.9 Unusual Architectures 265

14.10 The Big Picture 267

 

Part IV: Appendix 271

 

Appendix: PV Guest Porting Cheat Sheet 273

A.1 Domain Builder 273

A.2 Boot Environment 274

A.3 Setting Up the Virtual IDT 274

A.4 Page Table Management 275

A.5 Drivers 276

A.6 Domain 0 Responsibilities 276

A.7 Efficiency 277

A.8 Summary 278

 

Index 279