qemu-kvm创建参数分析
qemu的命令参数参考文档：
http://qemu.weilnetz.de/qemu-doc.html
下面是一个例子：
/usr/libexec/qemu-kvm -S -M rhel6.3.0
-cpu Westmere,+rdtscp,+pdpe1gb,+dca,+pdcm,+xtpr,+tm2,+est,+smx,+vmx,+ds_cpl,+monitor,+dtes64,+pclmuldq,+pbe,+tm,+ht,+ss,+acpi,+ds,+vme
-enable-kvm -m 2048
-smp 2,sockets=2,cores=1,threads=1
-name inst-1219 -uuid 1cf7a47c-18ec-11e2-92db-14feb5dc2c72 -nodefconfig -nodefaults
-chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/inst-1219.monitor,server,nowait
-mon chardev=charmonitor,id=monitor,mode=control
-rtc base=localtime -no-shutdown
-device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2
-drive file=/dev/drVG/lv1567,if=none,id=drive-virtio-disk0,format=raw,cache=none,aio=native
-device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x5,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1
-netdev tap,fd=22,id=hostnet0
-device e1000,netdev=hostnet0,id=net0,mac=00:16:3e:66:90:9a,bus=pci.0,addr=0x3
-netdev tap,fd=32,id=hostnet1
-device e1000,netdev=hostnet1,id=net1,mac=00:16:3e:90:70:bd,bus=pci.0,addr=0x4
-chardev pty,id=charserial0
-device isa-serial,chardev=charserial0,id=serial0
-device usb-tablet,id=input0 -vnc 0.0.0.0:9,password -vga cirrus
-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x6
下面进行详细解释：
/usr/libexec/qemu-kvm -S -M rhel6.3.0
-cpu Westmere,+rdtscp,+pdpe1gb,+dca,+pdcm,+xtpr,+tm2,+est,+smx,+vmx,+ds_cpl,+monitor,+dtes64,+pclmuldq,+pbe,+tm,+ht,+ss,+acpi,+ds,+vme
-enable-kvm （允许KVM全虚拟化支持，该选项只有在LINUX编译时就加入了KVM支持的时候才有效）
-m 2048 （RAM内存为2048MB）
-smp 2,sockets=2,cores=1,threads=1 （模拟双核的SMP，最多指定两个sockets，每个socket1个core, 每个core1个thread）
-name inst-1219
-uuid 1cf7a47c-18ec-11e2-92db-14feb5dc2c72 （ system UUID ）
-nodefconfig （默认下qemu会从sysconfdir 和 datadir 读取配置， -nodefconfig禁止qemu读取 ）
-nodefaults （默认qemu会创建serial port, parallel port, virtual console, monitor device, VGA adapter, floppy and CD-ROM drive and others， -nodefaults禁止创建这些默认的）
-chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/inst-1219.monitor,server,nowait （创建一个指定path的unix socket；server表示是一个linstening socket, nowait表示等待客户端连接的时候不应该阻塞）
-mon chardev=charmonitor,id=monitor,mode=control （把monitor重定向到宿主机设备/var/lib/libvirt/qemu/inst-1219）
-rtc base=localtime -no-shutdown
-device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 （添加piix3-usb-uhci US B驱动支持）
-drive file=/dev/drVG/lv1567,if=none,id=drive-virtio-disk0,format=raw,cache=none,aio=native （添加一个盘，ID为driver-virtio-disk0, raw格式，无cache, 使用linux native aio）
-device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x5,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 （为driver-virtio-disk0的盘添加驱动virtio-blk-pci）
-netdev tap,fd=22,id=hostnet0 (connet host tap interface to vlan n，fd表示已打开的host tap interface的句柄 ,该虚拟网卡的ID为hostnet0)
-device e1000,netdev=hostnet0,id=net0,mac=00:16:3e:66:90:9a,bus=pci.0,addr=0x3 （为hostnet0网卡添加e1000设备驱动）
-netdev tap,fd=32,id=hostnet1
-device e1000,netdev=hostnet1,id=net1,mac=00:16:3e:90:70:bd,bus=pci.0,addr=0x4
-chardev pty,id=charserial0 （添加一个ID为charserial0的pty设备）
-device isa-serial,chardev=charserial0,id=serial0 （为charserial0设备 添加isa-serial设备驱动）
-device usb-tablet,id=input0
-vnc 0.0.0.0:9,password
-vga cirrus
-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x6
最后用virsh dumpxml inst-1219
<domain type='kvm' id='99'>
<name>inst-1219</name>
<uuid>1cf7a47c-18ec-11e2-92db-14feb5dc2c72</uuid>
<memory unit='KiB'>2097152</memory>
<currentMemory unit='KiB'>2097152</currentMemory>
<vcpu placement='static'>2</vcpu>
<os>
<type arch='x86_64' machine='rhel6.3.0'>hvm</type>
<boot dev='hd'/>
</os>
<features>
<acpi/>
<apic/>
<pae/>
</features>
<cpu mode='custom' match='exact'>
<model fallback='allow'>Westmere</model>
<vendor>Intel</vendor>
<feature policy='require' name='tm2'/>
<feature policy='require' name='est'/>
<feature policy='require' name='vmx'/>
<feature policy='require' name='ds'/>
<feature policy='require' name='smx'/>
<feature policy='require' name='ss'/>
<feature policy='require' name='vme'/>
<feature policy='require' name='dtes64'/>
<feature policy='require' name='rdtscp'/>
<feature policy='require' name='ht'/>
<feature policy='require' name='dca'/>
<feature policy='require' name='pbe'/>
<feature policy='require' name='tm'/>
<feature policy='require' name='pdcm'/>
<feature policy='require' name='pdpe1gb'/>
<feature policy='require' name='ds_cpl'/>
<feature policy='require' name='pclmuldq'/>
<feature policy='require' name='xtpr'/>
<feature policy='require' name='acpi'/>
<feature policy='require' name='monitor'/>
</cpu>
<clock offset='localtime'/>
<on_poweroff>destroy</on_poweroff>
<on_reboot>restart</on_reboot>
<on_crash>restart</on_crash>
<devices>
<emulator>/usr/libexec/qemu-kvm</emulator>
<disk type='block' device='disk'>
<driver name='qemu' type='raw' cache='none' io='native'/>
<source dev='/dev/drVG/SNDACLOUD_lv1567'/>
<target dev='vda' bus='virtio'/>
<alias name='virtio-disk0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
</disk>
<controller type='usb' index='0'>
<alias name='usb0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
</controller>
<interface type='bridge'>
<mac address='00:16:3e:66:90:9a'/>
<source bridge='br1'/>
<target dev='vnet17'/>
<model type='e1000'/>
<alias name='net0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
</interface>
<interface type='bridge'>
<mac address='00:16:3e:90:70:bd'/>
<source bridge='br2.201'/>
<target dev='vnet18'/>
<model type='e1000'/>
<alias name='net1'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
</interface>
<serial type='pty'>
<source path='/dev/pts/25'/>
<target port='0'/>
<alias name='serial0'/>
</serial>
<console type='pty' tty='/dev/pts/25'>
<source path='/dev/pts/25'/>
<target type='serial' port='0'/>
<alias name='serial0'/>
</console>
<input type='tablet' bus='usb'>
<alias name='input0'/>
</input>
<input type='mouse' bus='ps2'/>
<graphics type='vnc' port='5909' autoport='yes'/>
<video>
<model type='cirrus' vram='9216' heads='1'/>
<alias name='video0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
</video>
<memballoon model='virtio'>
<alias name='balloon0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
</memballoon>
</devices>
<seclabel type='none'/>
</domain>
参考：
XML格式文档：
http://libvirt.org/format.html
qemu-kvm XML格式文档：
http://libvirt.org/drvqemu.html#xmlconfig
另外qemu参数和XML可以互转，参考：
http://libvirt.org/drvqemu.html
使用命令：
virsh domxml-from-native qemu-argv demo.args （根据参数生成XML）
virsh domxml-to-native qemu-argv demo.xml （根据XML生成参数）
Example domain XML config
QEMU emulated guest on x86_64<domain type='qemu'>
<name>QEmu-fedora-i686</name>
<uuid>c7a5fdbd-cdaf-9455-926a-d65c16db1809</uuid>
<memory>219200</memory>
<currentMemory>219200</currentMemory>
<vcpu>2</vcpu>
<os>
<type arch='i686' machine='pc'>hvm</type>
<boot dev='cdrom'/>
</os>
<devices>
<emulator>/usr/bin/qemu-system-x86_64</emulator>
<disk type='file' device='cdrom'>
<source file='/home/user/boot.iso'/>
<target dev='hdc'/>
<readonly/>
</disk>
<disk type='file' device='disk'>
<source file='/home/user/fedora.img'/>
<target dev='hda'/>
</disk>
<interface type='network'>
<source network='default'/>
</interface>
<graphics type='vnc' port='-1'/>
</devices>
</domain>
KVM hardware accelerated guest on i686
<domain type='kvm'>
<name>demo2</name>
<uuid>4dea24b3-1d52-d8f3-2516-782e98a23fa0</uuid>
<memory>131072</memory>
<vcpu>1</vcpu>
<os>
<type arch="i686">hvm</type>
</os>
<clock sync="localtime"/>
<devices>
<emulator>/usr/bin/qemu-kvm</emulator>
<disk type='file' device='disk'>
<source file='/var/lib/libvirt/images/demo2.img'/>
<target dev='hda'/>
</disk>
<interface type='network'>
<source network='default'/>
<mac address='24:42:53:21:52:45'/>
</interface>
<graphics type='vnc' port='-1' keymap='de'/>
</devices>
</domain>