You can list the available groups for virtualization from all yum repos with using the following yum command:
# yum grouplist|grep -i virtualization
This command lists the package group that has 'virtualization' as a substring in the group name among the list of all group names and does not install the virtualization RPM.
Subsequently, you can install the virtualization RPM with the following command:
# yum groupinstall "Virtualization"