双路超线程物理服务器的QEMU CPU affinity调整

首先运行 virsh capabilities 查看物理机物理核心及其线程与逻辑处理器（线程）的关系：

...
    <topology>
      <cells num='1'>
        <cell id='0'>
          <memory unit='KiB'>24671680</memory>
          <pages unit='KiB' size='4'>6167920</pages>
          <pages unit='KiB' size='2048'>0</pages>
          <distances>
            <sibling id='0' value='10'/>
          </distances>
          <cpus num='16'>
            <cpu id='0' socket_id='0' core_id='0' siblings='0,8'/>
            <cpu id='1' socket_id='0' core_id='1' siblings='1,9'/>
            <cpu id='2' socket_id='0' core_id='2' siblings='2,10'/>
            <cpu id='3' socket_id='0' core_id='3' siblings='3,11'/>
            <cpu id='4' socket_id='1' core_id='0' siblings='4,12'/>
            <cpu id='5' socket_id='1' core_id='1' siblings='5,13'/>
            <cpu id='6' socket_id='1' core_id='2' siblings='6,14'/>
            <cpu id='7' socket_id='1' core_id='3' siblings='7,15'/>
            <cpu id='8' socket_id='0' core_id='0' siblings='0,8'/>
            <cpu id='9' socket_id='0' core_id='1' siblings='1,9'/>
            <cpu id='10' socket_id='0' core_id='2' siblings='2,10'/>
            <cpu id='11' socket_id='0' core_id='3' siblings='3,11'/>
            <cpu id='12' socket_id='1' core_id='0' siblings='4,12'/>
            <cpu id='13' socket_id='1' core_id='1' siblings='5,13'/>
            <cpu id='14' socket_id='1' core_id='2' siblings='6,14'/>
            <cpu id='15' socket_id='1' core_id='3' siblings='7,15'/>
          </cpus>
        </cell>
      </cells>
    </topology>
    <cache>
      <bank id='0' level='3' type='both' size='8' unit='MiB' cpus='0-3,8-11'/>
      <bank id='1' level='3' type='both' size='8' unit='MiB' cpus='4-7,12-15'/>
    </cache>
...

...

</distances>

</cpus>

</cell>

</cells>

</topology>

<cache>

</cache>

...

其中的socket_id代表CPU的槽位，core_id代表CPU物理核心，siblings表示哪些逻辑处理器（线程）是属于同一个物理核心的。

例如id为0以及8的逻辑处理器，都属于同一个CPU槽位且属于同一个物理核心。

在这台物理机上建立的虚拟机，想得到最佳的性能，首先不要跨CPU插槽，其次，不要让多个虚拟机CPU共享同一个物理核心。

根据上面的信息，4核心8线程的虚拟机CPU亲和度配置如下：

<domain>
...
  <vcpu placement='static'>8</vcpu>
  <cputune>
    <vcpupin vcpu='0' cpuset='0'/>
    <vcpupin vcpu='1' cpuset='8'/>
    <vcpupin vcpu='2' cpuset='1'/>
    <vcpupin vcpu='3' cpuset='9'/>
    <vcpupin vcpu='4' cpuset='2'/>
    <vcpupin vcpu='5' cpuset='10'/>
    <vcpupin vcpu='6' cpuset='3'/>
    <vcpupin vcpu='7' cpuset='11'/>
  </cputune>
...
  <cpu mode='host-passthrough' check='none'>
    <topology sockets='1' cores='4' threads='2'/>
  </cpu>
...
</domain>

...

</cputune>

...

</cpu>

...

</domain>

其中vcpu 0和1在虚拟机中对应一个物理核心的两个线程，将其亲和度设定到逻辑处理器0和8，后面vcpu 2-7，同理。

启动虚拟机，通过 virsh vcpupin 进行验证：

VCPU: CPU Affinity
----------------------------------
   0: 0
   1: 8
   2: 1
   3: 9
   4: 2
   5: 10
   6: 3
   7: 11

VCPU: CPU Affinity

----------------------------------

0: 0

1: 8

2: 1

3: 9

4: 2

5: 10

6: 3

7: 11

到虚拟机中查看/proc/cpuinfo：

# cat /proc/cpuinfo | grep "core id"
core id		: 0
core id		: 0
core id		: 1
core id		: 1
core id		: 2
core id		: 2
core id		: 3
core id		: 3

# cat /proc/cpuinfo | grep "core id"

core id : 0

core id : 1

core id : 2

core id : 3

上面输出的信息可以确定设定无误，因为第一、二个逻辑核心对应了第一个物理核心，后面第三到第八个也同理。如果输出的core id与cputune处设定时所期望的顺序不对，调整cputune中的参数即可。

Tags: affinity, CPU, hyperthreading, libvirt, libvirtd, qemu, 亲和度, 超线程

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...
kernel: [ 6551.331932] audit: type=1400 audit(1549457961.800:209): apparmor="DENIED" operation="open" profile="libvirt-5831a051-78ee-43b4-a15d-6e520b1b3ab7" name="/virt/test.qcow2" pid=27204 comm="qemu-system-x86" requested_mask="r" denied_mask="r" fsuid=0 ouid=0
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...

kernel: [ 6551.331932] audit: type=1400 audit(1549457961.800:209): apparmor="DENIED" operation="open" profile="libvirt-5831a051-78ee-43b4-a15d-6e520b1b3ab7" name="/virt/test.qcow2" pid=27204 comm="qemu-system-x86" requested_mask="r" denied_mask="r" fsuid=0 ouid=0

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使用TLS连接libvirtd时，默认需要验证客户端是否拥有由CA签名的证书，详见libvirtd配置文件（/etc/libvirt/libvirtd.conf）：

# Flag to disable verification of client certificates
#
# Client certificate verification is the primary authentication mechanism.
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# Flag to disable verification of client certificates

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