12.9. Verifying host CPU compatibility for virtual machine migration

Procedure

1. On the source host, obtain its CPU features and paste them into a new XML file, such as domCaps-CPUs.xml.

   # virsh domcapabilities | xmllint --xpath "//cpu/mode[@name='host-model']" - > domCaps-CPUs.xml

2. In the XML file, replace the <mode> </mode> tags with <cpu> </cpu>.

3. Optional: Verify that the content of the domCaps-CPUs.xml file looks similar to the following:

   # cat domCaps-CPUs.xml
   
       <cpu>
             <model fallback="forbid">Skylake-Client-IBRS</model>
             <vendor>Intel</vendor>
             <feature policy="require" name="ss"/>
             <feature policy="require" name="vmx"/>
             <feature policy="require" name="pdcm"/>
             <feature policy="require" name="hypervisor"/>
             <feature policy="require" name="tsc_adjust"/>
             <feature policy="require" name="clflushopt"/>
             <feature policy="require" name="umip"/>
             <feature policy="require" name="md-clear"/>
             <feature policy="require" name="stibp"/>
             <feature policy="require" name="arch-capabilities"/>
             <feature policy="require" name="ssbd"/>
             <feature policy="require" name="xsaves"/>
             <feature policy="require" name="pdpe1gb"/>
             <feature policy="require" name="invtsc"/>
             <feature policy="require" name="ibpb"/>
             <feature policy="require" name="ibrs"/>
             <feature policy="require" name="amd-stibp"/>
             <feature policy="require" name="amd-ssbd"/>
             <feature policy="require" name="rsba"/>
             <feature policy="require" name="skip-l1dfl-vmentry"/>
             <feature policy="require" name="pschange-mc-no"/>
             <feature policy="disable" name="hle"/>
             <feature policy="disable" name="rtm"/>
       </cpu>

4. On the destination host, use the following command to obtain its CPU features:

   # virsh domcapabilities | xmllint --xpath "//cpu/mode[@name='host-model']" -
   
       <mode name="host-model" supported="yes">
               <model fallback="forbid">IvyBridge-IBRS</model>
               <vendor>Intel</vendor>
               <feature policy="require" name="ss"/>
               <feature policy="require" name="vmx"/>
               <feature policy="require" name="pdcm"/>
               <feature policy="require" name="pcid"/>
               <feature policy="require" name="hypervisor"/>
               <feature policy="require" name="arat"/>
               <feature policy="require" name="tsc_adjust"/>
               <feature policy="require" name="umip"/>
               <feature policy="require" name="md-clear"/>
               <feature policy="require" name="stibp"/>
               <feature policy="require" name="arch-capabilities"/>
               <feature policy="require" name="ssbd"/>
               <feature policy="require" name="xsaveopt"/>
               <feature policy="require" name="pdpe1gb"/>
               <feature policy="require" name="invtsc"/>
               <feature policy="require" name="ibpb"/>
               <feature policy="require" name="amd-ssbd"/>
               <feature policy="require" name="skip-l1dfl-vmentry"/>
               <feature policy="require" name="pschange-mc-no"/>
       </mode>

5. Add the obtained CPU features from the destination host to the domCaps-CPUs.xml file on the source host. Again, replace the <mode> </mode> tags with <cpu> </cpu> and save the file.

6. Optional: Verify that the XML file now contains the CPU features from both hosts.

   # cat domCaps-CPUs.xml
   
       <cpu>
             <model fallback="forbid">Skylake-Client-IBRS</model>
             <vendor>Intel</vendor>
             <feature policy="require" name="ss"/>
             <feature policy="require" name="vmx"/>
             <feature policy="require" name="pdcm"/>
             <feature policy="require" name="hypervisor"/>
             <feature policy="require" name="tsc_adjust"/>
             <feature policy="require" name="clflushopt"/>
             <feature policy="require" name="umip"/>
             <feature policy="require" name="md-clear"/>
             <feature policy="require" name="stibp"/>
             <feature policy="require" name="arch-capabilities"/>
             <feature policy="require" name="ssbd"/>
             <feature policy="require" name="xsaves"/>
             <feature policy="require" name="pdpe1gb"/>
             <feature policy="require" name="invtsc"/>
             <feature policy="require" name="ibpb"/>
             <feature policy="require" name="ibrs"/>
             <feature policy="require" name="amd-stibp"/>
             <feature policy="require" name="amd-ssbd"/>
             <feature policy="require" name="rsba"/>
             <feature policy="require" name="skip-l1dfl-vmentry"/>
             <feature policy="require" name="pschange-mc-no"/>
             <feature policy="disable" name="hle"/>
             <feature policy="disable" name="rtm"/>
       </cpu>
       <cpu>
             <model fallback="forbid">IvyBridge-IBRS</model>
             <vendor>Intel</vendor>
             <feature policy="require" name="ss"/>
             <feature policy="require" name="vmx"/>
             <feature policy="require" name="pdcm"/>
             <feature policy="require" name="pcid"/>
             <feature policy="require" name="hypervisor"/>
             <feature policy="require" name="arat"/>
             <feature policy="require" name="tsc_adjust"/>
             <feature policy="require" name="umip"/>
             <feature policy="require" name="md-clear"/>
             <feature policy="require" name="stibp"/>
             <feature policy="require" name="arch-capabilities"/>
             <feature policy="require" name="ssbd"/>
             <feature policy="require" name="xsaveopt"/>
             <feature policy="require" name="pdpe1gb"/>
             <feature policy="require" name="invtsc"/>
             <feature policy="require" name="ibpb"/>
             <feature policy="require" name="amd-ssbd"/>
             <feature policy="require" name="skip-l1dfl-vmentry"/>
             <feature policy="require" name="pschange-mc-no"/>
       </cpu>

7. Use the XML file to calculate the CPU feature baseline for the VM you intend to migrate.

   # virsh hypervisor-cpu-baseline domCaps-CPUs.xml
   
       <cpu mode='custom' match='exact'>
         <model fallback='forbid'>IvyBridge-IBRS</model>
         <vendor>Intel</vendor>
         <feature policy='require' name='ss'/>
         <feature policy='require' name='vmx'/>
         <feature policy='require' name='pdcm'/>
         <feature policy='require' name='pcid'/>
         <feature policy='require' name='hypervisor'/>
         <feature policy='require' name='arat'/>
         <feature policy='require' name='tsc_adjust'/>
         <feature policy='require' name='umip'/>
         <feature policy='require' name='md-clear'/>
         <feature policy='require' name='stibp'/>
         <feature policy='require' name='arch-capabilities'/>
         <feature policy='require' name='ssbd'/>
         <feature policy='require' name='xsaveopt'/>
         <feature policy='require' name='pdpe1gb'/>
         <feature policy='require' name='invtsc'/>
         <feature policy='require' name='ibpb'/>
         <feature policy='require' name='amd-ssbd'/>
         <feature policy='require' name='skip-l1dfl-vmentry'/>
         <feature policy='require' name='pschange-mc-no'/>
       </cpu>

8. Open the XML configuration of the VM you intend to migrate, and replace the contents of the <cpu> section with the settings obtained in the previous step.

   # virsh edit <vm_name>

9. If the VM is running, shut down the VM and start it again.

   # virsh shutdown <vm_name>
   
   # virsh start <vm_name>