Libvirt常见问题

Libvirt FAQ

  • domain xml
  • 网络 xml
  • 注意
    • uuid 和 mac 类字段如果没有,则导入的时候生成
  • 三种配置状态
    • live - 运行状态
      • 修改立即生效
    • inactive - 不活跃的状态
      • 修改需要重启后生效
    • current - 当前状态
      • 指向 live 或 inactive

CPU 资源配额

  • 参考 CPUTuning
  • shares - 每个 vCPU
  • period、quota - 每个 vCPU,但会首 quota 定义限制
  • emulator_period、emulator_quota - 每个模拟线程,主机 40-80% 性能

重启网络

NET_NAME=default
NET_HOOK=/etc/libvirt/hooks/qemu
virsh net-destroy $NET_NAME
virsh net-start $NET_NAME
VMS=$( virsh list | tail -n +3 | head -n -1 | awk '{ print $2; }' )
for m in $VMS ; do
echo "$m"
MAC_ADDR=$(virsh domiflist "$m" |grep -o -E "([0-9a-f]{2}:){5}([0-9a-f]{2})")
NET_MODEL=$(virsh domiflist "$m" | tail -n +3 | head -n -1 | awk '{ print $4; }')
set +e
virsh detach-interface "$m" network --mac "$MAC_ADDR" && sleep 3
virsh attach-interface "$m" network $NET_NAME --mac "$MAC_ADDR" --model "$NET_MODEL"
set -e
$NET_HOOK "$m" stopped && sleep 3
$NET_HOOK "$m" start
done

处理 libvirt hang 的问题

if [ "$1" = 'start' ]; then
modprobe tun
sleep 1
service virtlogd start
sleep 1
service virtqemud start
sleep 1
service virtnetworkd start
sleep 1
service virtstoraged start
sleep 1
service libvirtd start
elif [ "$1" = 'stop' ]; then
service libvirtd stop
sleep 1
service virtlogd stop
sleep 1
service virtstoraged stop
sleep 1
service virtnetworkd stop
sleep 1
service virtqemud stop
killall -9 dnsmasq
else
printf "Usage $0: start | stop\n"
fi

实时修改网络配置

# 立即生效,不需要重启
virsh net-update --config --live default add ip-dhcp-host \
"<host mac='52:54:00:01:02:03' name='xyz.example.com' ip='192.168.122.25'/>"

Refusing to undefine while domain managed save image exists

virsh managedsave-remove vm
virsh undefine vm

host-model vs host-passthrough

https://www.reddit.com/r/VFIO/comments/a20bf7/hostmodel_vs_hostpassthrough_super_poor_cache/

动态 CPU 和内存

<maxMemory slots='16' unit='GiB'>64</maxMemory>
<memory unit='GiB'>32</memory>
<currentMemory unit='GiB'>32</currentMemory>
<vcpu placement='static' current='8'>16</vcpu>
<cpu>
<numa>
<cell id='0' cpus='0-8' memory='32' unit='GiB'/>
</numa>
<!-- 其他内容 -->
</cpu>

At least one numa node has to be configured when enabling memory hotplug

配置热插拔内存后需要配置 numa

<cpu>
<numa>
<cell id='0' cpus='0-8' memory='4' unit='GiB'/>
</numa>
<!-- 其他内容 -->
</cpu>

console 没有终端

确保定义有Serial

<serial type='pty'>
<target port='0'/>
</serial>
<console type='pty'>
<target type='serial' port='0'/>
</console>

如果还是没有,则尝试添加 kernel 参数

console=tty0 console=ttyS0

console=ttyS0,19200 earlyprint=serial,ttyS0,19200

guest CPU doesn't match specification: missing features: spec-ctrl,stibp,ssbd

<!-- 最简单的修复方式是使用主机的模型 -->
<cpu mode='host-model'/>
core2duoIvyBridge-IBRSIntel

获取主机 IP

# 主机名字
HOSTNAME=base
MAC=$(virsh domiflist $HOSTNAME | awk{ print $5 }| tail -2 | head -1)
arp -a | grep $MAC | awk '{ print $2 }' | sed ‘s/[()]//g’

克隆主机的注意事项

# 持久化的网卡信息 - alpine 默认没有
rm -f /etc/udev/rules.d/70-persistent-net.rules
# 删除 ssh 的 host id
rm -rf /etc/ssh/ssh_host_*

网络

默认网络

<network>
<name>default</name>
<uuid/>
<forward mode='nat'>
<nat>
<port start='1024' end='65535'/>
</nat>
</forward>
<bridge name='virbr0' stp='on' delay='0'/>
<mac/>
<ip address='192.168.122.1' netmask='255.255.255.0'>
<dhcp>
<!-- DHCP 范围 -->
<range start='192.168.122.2' end='192.168.122.254'/>
<!-- 静态 IP -->
<!-- <host mac='52:54:00:70:d9:ee' name='myhost' ip='192.168.122.10'/> -->
</dhcp>
</ip>
</network>

基本配置

  • connections - 当前连接数 在运行中的网络看得到
  • libvirt 会维护一个 dnsmasq 实例
<network ipv6='yes' trustGuestRxFilters='no' connections='10'>
<!-- 基本元数据 -->
<name>default</name>
<uuid>3e3fce45-4f53-4fa7-bb32-11f34168b82b</uuid>
<metadata>
<app1:foo xmlns:app1="http://app1.org/app1/">..</app1:foo>
<app2:bar xmlns:app2="http://app1.org/app2/">..</app2:bar>
</metadata>
<!-- 连接性配置 -->
<mtu size="9000"/>
<!-- QoS -->
<bandwidth>
<inbound floor='500' average='1000' peak='5000' burst='5120'/>
<outbound average='128' peak='256' burst='256'/>
</bandwidth>
<!-- 静态路由 -->
<ip address="192.168.122.1" netmask="255.255.255.0">
<dhcp>
<range start="192.168.122.128" end="192.168.122.254"/>
<host mac="00:16:3e:77:e2:ed" name="foo.example.com" ip="192.168.122.10"/>
</dhcp>
<!-- tftp -->
</ip>
<route address="192.168.222.0" prefix="24" gateway="192.168.122.2"/>
<!-- 地址 - 只支持隔离 即 非 forward -->
<!-- 桥接网卡设备的 MAC -->
<mac address='00:16:3E:5D:C7:9E'/>
<domain name="example.com"/>
<!-- enable 默认开启 -->
<!-- forwardPlainNames 如果关闭则不会处理不带 . 的名字 -->
<dns enable='yes' forwardPlainNames='yes'>
<txt name="example" value="example value"/>
<forwarder addr="8.8.8.8"/>
<forwarder domain='example.com' addr="8.8.4.4"/>
<forwarder domain='www.example.com'/>
<srv service='name' protocol='tcp' domain='test-domain-name' target='.'
port='1024' priority='10' weight='10'/>
<host ip='192.168.122.2'>
<hostname>myhost</hostname>
<hostname>myhostalias</hostname>
</host>
</dns>
<!-- 自定义 dnsmasq 属性 -->
<dnsmasq:options>
<dnsmasq:option value="foo=bar"/>
<dnsmasq:option value="cname=*.foo.example.com,master.example.com"/>
</dnsmasq:options>
</network>

使用现有宿主机桥接网络

<network>
<name>host-bridge</name>
<forward mode="bridge"/>
<bridge name="br0"/>
</network>

使用 macvtap

  • 类似于桥接,但不需要主机存在桥接网卡
  • 主机该网卡与虚拟机不互通
<network>
<name>direct-macvtap</name>
<forward mode="bridge">
<interface dev="eth0"/>
<interface dev="eth1"/>
</forward>
</network>

使用主机网卡

<network>
<name>host-passthrough</name>
<!-- 设备池 -->
<forward mode='passthrough'>
<interface dev='eth10'/>
<interface dev='eth11'/>
<interface dev='eth12'/>
<interface dev='eth13'/>
<interface dev='eth14'/>
</forward>
</network>

使用主机网卡下挂载的虚拟网卡

<network>
<name>host-passthrough-vnet</name>
<forward mode='passthrough'>
<pf dev='eth0'/>
</forward>
</network>

显存调整

  • kvm 可以使用 cirrus 做更好的显示
  • 注意显存大小 - 过小会导致显示出问题
<video>
<model type='cirrus' vram='9216' heads='1'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
</video>

动态内存

<maxMemory slots='16' unit='GiB'>16</maxMemory>
<!-- memory 和 currentMemory 参数可选 -->
<!-- <memory unit='GiB'>8</memory> -->
<!-- 初始内存 -->
<!-- <currentMemory unit='GiB'>2</currentMemory> -->
<!-- 热插拔需要 numa -->
<cpu>
<numa>
<cell id='0' cpus='0-2' memory='1' unit='GiB'/>
</numa>
</cpu>

memory ballooning

<memballoon model='virtio' autodeflate='on'>