I just tried to create a CentOS 7 VM on a CentOS 6 host, but it crashes to the dracut prompt. I am using the PXEBoot installer. I *think* it is unhappy with the (virtual) graphics controller, but I am not sure.
The rdsosreport.txt file is available here: https://www.deepsoft.com/wp-content/uploads/2018/09/rdsosreport.txt