I tried to follow this guide https://www.berrange.com/posts/2010/02/15/guest-cpu-model-configuration-in-l... I found that the host that has the proble has no pbe|tm|ht||acpi|ds flags in output of " cat /proc/cpuinfo" In the Ovirt-Engine server I run the below #virsh -r cpu-compare ./cpu-server.xml CPU described in ./cpu-server.xml is incompatible with host CPU #virsh -r cpu-baseline ./cpu-server.xml <cpu mode='custom' match='exact'> <model fallback='allow'>cpu64-rhel6</model> <vendor>Intel</vendor> <feature policy='require' name='xtpr'/> <feature policy='require' name='cid'/> <feature policy='require' name='est'/> <feature policy='require' name='vmx'/> <feature policy='require' name='ds_cpl'/> <feature policy='require' name='monitor'/> <feature policy='require' name='dtes64'/> <feature policy='require' name='pbe'/> <feature policy='require' name='tm'/> <feature policy='require' name='ht'/> <feature policy='require' name='ss'/> <feature policy='require' name='acpi'/> <feature policy='require' name='ds'/> <feature policy='require' name='vme'/> </cpu>