Comment 38 for bug 1856335

Sanjay,

You can just increase the number of vcpus, such as:

<vcpu placement="static" current="48">64</vcpu>

then continue to define the vcpus:

    <vcpu id="32" enabled="yes" hotpluggable="yes"/>
    <vcpu id="33" enabled="yes" hotpluggable="yes"/>
    <vcpu id="34" enabled="yes" hotpluggable="yes"/>
    <vcpu id="35" enabled="yes" hotpluggable="yes"/>
    <vcpu id="36" enabled="yes" hotpluggable="yes"/>
    <vcpu id="37" enabled="yes" hotpluggable="yes"/>
    <vcpu id="38" enabled="no" hotpluggable="yes"/>
    <vcpu id="39" enabled="no" hotpluggable="yes"/>
    <vcpu id="40" enabled="yes" hotpluggable="yes"/>
    <vcpu id="41" enabled="yes" hotpluggable="yes"/>
    <vcpu id="42" enabled="yes" hotpluggable="yes"/>
    <vcpu id="43" enabled="yes" hotpluggable="yes"/>
    <vcpu id="44" enabled="yes" hotpluggable="yes"/>
    <vcpu id="45" enabled="yes" hotpluggable="yes"/>
    <vcpu id="46" enabled="no" hotpluggable="yes"/>
    <vcpu id="47" enabled="no" hotpluggable="yes"/>
    <vcpu id="48" enabled="yes" hotpluggable="yes"/>
    <vcpu id="49" enabled="yes" hotpluggable="yes"/>
    <vcpu id="50" enabled="yes" hotpluggable="yes"/>
    <vcpu id="51" enabled="yes" hotpluggable="yes"/>
    <vcpu id="52" enabled="yes" hotpluggable="yes"/>
    <vcpu id="53" enabled="yes" hotpluggable="yes"/>
    <vcpu id="54" enabled="no" hotpluggable="yes"/>
    <vcpu id="55" enabled="no" hotpluggable="yes"/>
    <vcpu id="56" enabled="yes" hotpluggable="yes"/>
    <vcpu id="57" enabled="yes" hotpluggable="yes"/>
    <vcpu id="58" enabled="yes" hotpluggable="yes"/>
    <vcpu id="59" enabled="yes" hotpluggable="yes"/>
    <vcpu id="60" enabled="yes" hotpluggable="yes"/>
    <vcpu id="61" enabled="yes" hotpluggable="yes"/>
    <vcpu id="62" enabled="no" hotpluggable="yes"/>
    <vcpu id="63" enabled="no" hotpluggable="yes"/>

(6x enabled=yes, then 2x enabled=no.)

You will get more vcpu ids than you have threads, but since you disable 16 out of 64, you will have 48 active.

vcpupin should continue as follows:

    <vcpupin vcpu="32" cpuset="24"/>
    <vcpupin vcpu="33" cpuset="36"/>
    <vcpupin vcpu="34" cpuset="25"/>
    <vcpupin vcpu="35" cpuset="37"/>
    <vcpupin vcpu="36" cpuset="26"/>
    <vcpupin vcpu="37" cpuset="38"/>
    <vcpupin vcpu="40" cpuset="27"/>
    <vcpupin vcpu="41" cpuset="39"/>
    <vcpupin vcpu="42" cpuset="28"/>
    <vcpupin vcpu="43" cpuset="40"/>
    <vcpupin vcpu="44" cpuset="29"/>
    <vcpupin vcpu="45" cpuset="41"/>
    <vcpupin vcpu="48" cpuset="30"/>
    <vcpupin vcpu="49" cpuset="42"/>
    <vcpupin vcpu="50" cpuset="31"/>
    <vcpupin vcpu="51" cpuset="43"/>
    <vcpupin vcpu="52" cpuset="32"/>
    <vcpupin vcpu="53" cpuset="44"/>
    <vcpupin vcpu="56" cpuset="33"/>
    <vcpupin vcpu="57" cpuset="45"/>
    <vcpupin vcpu="58" cpuset="34"/>
    <vcpupin vcpu="59" cpuset="46"/>
    <vcpupin vcpu="60" cpuset="35"/>
    <vcpupin vcpu="61" cpuset="47"/>

This is if you pin all vcpus to the VM, which may not be the best thing to do. The maximum number of vcpus you can pin on a Threadripper 3960X are 48.