kvm主要包括kvm、kmod-kvm、etherboot-zroms-kvm三个包，下面是对各个包的研究，通过研究这些文件，可以了解kvm的构成结构。
一、包内容分析
1、kvm 包 1）概要说明
------------------------------------------------------------------------------------------------ Name : kvm Relocations: (not relocatable) Version : 83 Vendor: CentOS Release : 239.el5.centos Build Date: Fri 22 Jul 2011 09:52:35 PM CST Install Date: Mon 21 Nov 2011 02:47:25 PM CST Build Host: builder10.centos.org Group : Development/Tools Source RPM: kvm-83-239.el5.centos.src.rpm Size : 2126435 License: GPLv2 Signature : DSA/SHA1, Sat 13 Aug 2011 05:26:42 AM CST, Key ID a8a447dce8562897 URL : http://kvm.sf.net Summary : Kernel-based Virtual Machine Description : KVM(基于内核的虚拟机)是一个针x86平台上Linux的全虚拟化解决方案。 KVM (for Kernel-based Virtual Machine) is a full virtualization solution for Linux on x86 hardware.
利用KVM，一个机器能够运行多个之上运行未经修改linux或windows操作系统的虚拟机。每一个虚拟机拥有其专有的 虚拟硬件：如网络接口卡、显卡等。 Using KVM, one can run multiple virtual machines running unmodified Linux or Windows images. Each virtual machine has private virtualized hardware: a network card, disk, graphics adapter, etc.
2）此包在操作系统上安装的文件 /etc/sysconfig/modules/kvm.modules --kvm 模块加载配置文件 /etc/udev/rules.d/65-kvm.rules --kvm 设备的udev规则文件 /usr/bin/ksmctl --内核共享页合并程序（Kernel Sharedpage Merging） 需要在/dev下有ksm设备 /usr/libexec/qemu-kvm --基于qemu的虚拟机仿真程序，所有的虚拟机均通过此程序启动 /usr/share/kvm
--各类虚拟BIOS文件 /usr/share/kvm/bios.bin /usr/share/kvm/extboot.bin extboot is an x86 Option ROM that passes through int13 functions to a VMM which allows a VMM to expose an arbitrary block device as the primary BIOS disk. It can be used to boot SCSI or paravirtual devices. --以下为通过PXE启动用到的网卡ROM BIOS，这些文件是指向/usr/share/qemu-pxe-roms/目录下，zrom格式的文件 /usr/share/kvm/pxe-e1000.bin /usr/share/kvm/pxe-ne2k_pci.bin /usr/share/kvm/pxe-pcnet.bin /usr/share/kvm/pxe-rtl8139.bin /usr/share/kvm/pxe-virtio.bin /usr/share/kvm/vgabios-cirrus.bin /usr/share/kvm/vgabios.bin --键盘映射文件 /usr/share/kvm/keymaps /usr/share/kvm/keymaps/ar /usr/share/kvm/keymaps/common /usr/share/kvm/keymaps/da /usr/share/kvm/keymaps/de /usr/share/kvm/keymaps/de-ch /usr/share/kvm/keymaps/en-gb /usr/share/kvm/keymaps/en-us /usr/share/kvm/keymaps/es /usr/share/kvm/keymaps/et /usr/share/kvm/keymaps/fi /usr/share/kvm/keymaps/fo /usr/share/kvm/keymaps/fr /usr/share/kvm/keymaps/fr-be /usr/share/kvm/keymaps/fr-ca /usr/share/kvm/keymaps/fr-ch /usr/share/kvm/keymaps/hr /usr/share/kvm/keymaps/hu /usr/share/kvm/keymaps/is /usr/share/kvm/keymaps/it /usr/share/kvm/keymaps/ja /usr/share/kvm/keymaps/lt /usr/share/kvm/keymaps/lv /usr/share/kvm/keymaps/mk /usr/share/kvm/keymaps/modifiers /usr/share/kvm/keymaps/nl /usr/share/kvm/keymaps/nl-be /usr/share/kvm/keymaps/no /usr/share/kvm/keymaps/pl /usr/share/kvm/keymaps/pt /usr/share/kvm/keymaps/pt-br /usr/share/kvm/keymaps/ru /usr/share/kvm/keymaps/sl /usr/share/kvm/keymaps/sv /usr/share/kvm/keymaps/th /usr/share/kvm/keymaps/tr /usr/share/man/man1/qemu-kvm.1.gz --qemu-kvm 帮助文件
从上面的文件类型来看，此包只涵盖KVM管理相关的文件或程序，不包括KVM核心模块，这些模块在哪里呢？在另一个 名称为kmod-kvm的包中，将在后面进行说明。 3）kvm包依赖的其他包 >alsa-lib --分组：System Environment/Libraries --说明：The Advanced Linux Sound Architecture (ALSA) 库. ALSA向Linux操作系统提供音频和MIDI功能。
>bash --分组：System Environment/Shells --说明：The GNU Bourne Again shell (bash)
>celt051 --分组：System Environment/Libraries --说明：CELT (Constrained Energy Lapped Transform) 一个提供低延迟语音和音频通信的编解码器
>etherboot-zroms-kvm --分组：Development/Tools --说明：网络引导 KVM支持的.zrom格式的引导ROM（只读存储器）
>qcairo --分组：System Environment/Libraries --说明：一个二维图形库 This is a version of the cairo 2D graphics library, with additional features required to support the implementation of the spice protocol. Cairo is a 2D graphics library designed to provide high-quality display and print output. Currently supported output targets include the X Window System, OpenGL (via glitz), in-memory image buffers, and image files (PDF, PostScript, and SVG).
>glibc --分组：System Environment/Libraries --说明：GNU libc库， The glibc package contains standard libraries which are used by multiple programs on the system. In order to save disk space and memory, as well as to make upgrading easier, common system code is kept in one place and shared between programs. This particular package contains the most important sets of shared libraries: the standard C library and the standard math library. Without these two libraries, a Linux system will not function.
>gnutls --分组：System Environment/Libraries --说明：TLS协议实现 GnuTLS is a project that aims to develop a library which provides a secure layer, over a reliable transport layer. Currently the GnuTLS library implements the proposed standards by the IETF's TLS working group.
>initscripts --分组：System Environment/Base --说明：inittab 文件和 /etc/init.d 脚本 The initscripts package contains the basic system scripts used to boot your CentOS system, change runlevels, and shut the system down cleanly. Initscripts also contains the scripts that activate and deactivate most network interfaces.
>kmod-kvm --分组：System Environment/Kernel --说明：KVM内核模块 This package provides the kvm kernel modules built for the Linux kernel 2.6.18-274.el5 for the x86_64 family of processors.
>libgcrypt --分组：System Environment/Libraries --说明：一个通用加密库。
>libgpg-error --分组：System Environment/Libraries --说明：This is a library that defines common error values for all GnuPG components. Among these are GPG, GPGSM, GPGME, GPG-Agent, libgcrypt,pinentry, SmartCard Daemon and possibly more in the future.
>libpng --分组：System Environment/Libraries --说明：提供操作PNG格式图形文件功能的库。 he libpng package contains a library of functions for creating and manipulating PNG (Portable Network Graphics) image format files. PNG is a bit-mapped graphics format similar to the GIF format. PNG was created to replace the GIF format, since GIF uses a patented data compression algorithm. Libpng should be installed if you need to manipulate PNG format image files.
>libXrandr --分组：System Environment/Libraries --说明：X.Org X11 libXrandr运行时库
>log4cpp --分组：Development/Libraries --说明： C++ logging library
>nspr --分组：System Environment/Libraries --说明：Netscape Portable Runtime NSPR provides platform independence for non-GUI operating system facilities. These facilities include threads, thread synchronization, normal file and network I/O, interval timing and calendar time, basic memory management (malloc and free) and shared library linking.
>openssl --分组：System Environment/Libraries --说明：OpenSSL 工具包 The OpenSSL toolkit provides support for secure communications between machines. OpenSSL includes a certificate management tool and shared libraries which provide various cryptographic algorithms and protocols.
>qffmpeg-libs --分组：ystem Environment/Libraries --说明：Codec and format libraries for qffmpeg intended for use with the SPICE virtual desktop protocol.
>qspice-libs --分组：System Environment/Libraries --说明： Libraries for qspice This package contains the runtime libraries for any application that wishes to be a qspice server.
>SDL --分组：System Environment/Libraries --说明：A cross-platform multimedia library. Simple DirectMedia Layer (SDL) is a cross-platform multimedia library designed to provide fast access to the graphics frame buffer and audio device.
>shadow-utils --分组：System Environment/Base --说明：Utilities for managing accounts and shadow password files The shadow-utils package includes the necessary programs for converting UNIX password files to the shadow password format, plus programs for managing user and group accounts. The pwconv command converts passwords to the shadow password format. The pwunconv command unconverts shadow passwords and generates an npasswd file (a standard UNIX password file). The pwck command checks the integrity of password and shadow files. The lastlog command prints out the last login times for all users. The useradd, userdel, and usermod commands are used for managing user accounts. The groupadd, groupdel, and groupmod commands are used for managing group accounts.
>zlib --分组：System Environment/Libraries --说明：The zlib compression and decompression library. Zlib is a general-purpose, patent-free, lossless data compression library which is used by many different programs. ================================================================================================ 2、kmod-kvm包 1）概要说明 ------------------------------------------------------------------------------------------------ Name : kmod-kvm Relocations: (not relocatable) Version : 83 Vendor: (none) Release : 274.el5.centos.2 Build Date: Thu 17 Nov 2011 10:19:56 AM CST Install Date: Mon 21 Nov 2011 02:51:30 PM CST Build Host: localhost.localdomain Group : System Environment/Kernel Source RPM: kmod-kvm-83-274.el5.centos.2.src.rpm Size : 476848 License: GPL Signature : (none) URL : http://www.qumranet.com Summary : kvm kernel module Description : 这个内核模块提供对使用硬件虚拟化（Intel VT-x&VT-i 或 AMD SVM）的虚拟机的支持。 This kernel module provides support for virtual machines using hardware support (Intel VT-x&VT-i or AMD SVM).
2）此包在操作系统上安装的文件 /lib/modules/2.6.18-274.el5/extra/kmod-kvm /lib/modules/2.6.18-274.el5/extra/kmod-kvm/ksm.ko /lib/modules/2.6.18-274.el5/extra/kmod-kvm/kvm-amd.ko /lib/modules/2.6.18-274.el5/extra/kmod-kvm/kvm-intel.ko /lib/modules/2.6.18-274.el5/extra/kmod-kvm/kvm.ko /lib/modules/2.6.18-274.7.1.el5/extra/kvm-amd.ko /lib/modules/2.6.18-274.7.1.el5/extra/kvm-intel.ko /lib/modules/2.6.18-274.7.1.el5/extra/kvm.ko
从安装文件内容来看，kvm内核模块文件都在这个包中。
3）kmod-kvm包依赖的其他包 此包只依赖内核，不涉及其他的库或者工具包
================================================================================================ 3、etherboot-zroms-kvm包 1）概要说明 ------------------------------------------------------------------------------------------------ Name : etherboot-zroms-kvm Relocations: (not relocatable) Version : 5.4.4 Vendor: CentOS Release : 13.el5.centos Build Date: Mon 05 Apr 2010 03:05:57 AM CST Install Date: Wed 16 Nov 2011 11:04:10 AM CST Build Host: builder10.centos.org Group : Development/Tools Source RPM: etherboot-5.4.4-13.el5.centos.src.rpm Size : 196608 License: GPLv2 Signature : DSA/SHA1, Tue 27 Apr 2010 07:41:01 AM CST, Key ID a8a447dce8562897 URL : http://etherboot.org Summary : Etherboot - boot roms supported by KVM, .zrom format Description : 此包中包含kvm仿真的通过网卡引导的.zrom格式的ROM文件。
2）此包在操作系统上安装的文件 /usr/share/etherboot /usr/share/etherboot/e1000-82542.zrom /usr/share/etherboot/ne.zrom /usr/share/etherboot/pcnet32.zrom /usr/share/etherboot/rtl8029.zrom /usr/share/etherboot/rtl8139.zrom /usr/share/etherboot/virtio-net.zrom /usr/share/qemu-pxe-roms
3）etherboot-zroms-kvm包依赖的其他包 bash 只需要有shell支持即可。 ================================================================================================ 三、kvm模块配置文件
配置文件位置：/etc/sysconfig/modules/kvm.modules
文件内容如下： ---------------------------------------------------------------------------------------------- if [ $(grep -c vmx /proc/cpuinfo) -ne 0 ]; then --判断是否为Intel CPU modprobe kvm-intel >/dev/null 2>&1 fi
if [ $(grep -c svm /proc/cpuinfo) -ne 0 ]; then --判断是否为AMD CPU modprobe kvm-amd >/dev/null 2>&1 fi
modprobe ksm >/dev/null 2>&1 ---------------------------------------------------------------------------------------------- 本配置前两个语句主要是检查host CPU 类型，然后加载对应的模块，Intel 为 kvm-intel\AMD 为kvm-amd 无论是Intel 还是 AMD CPU，均需要加载 ksm模块。
>/dev/null 2>&1 是指将模块加载命令的输出信息及错误信息都重定向到/dev/null设备中，默认情况下这两类 信息都输出到屏幕
================================================================================================ 四、综合分析
通过对kvm包极其涵盖的文件分析，kvm提供的程序和文件主要包括三部分： 1、内核模块：kvm.ko、kvm-amd、kvm-intel.ko、ksm.ko 2、虚拟机仿真、管理相关文件：qemu-kvm、*.bin 3、网卡仿真BIOS文件。
明确了包含哪些文件，通过分析这些文件的作用，即可对kvm的运行机制有一个概要的理解了。
本文转自 freeterman 51CTO博客，原文链接：http://blog.51cto.com/myunix/1129703，如需转载请自行联系原作者
