Check if the cpu virtualization support is enabled on BIOS.

You can also check if the cpu supports the virtualization linux command - egrep -c '(vmx|svm)' /proc/cpuinfo

If the output is 0 , that means the virtualization is not supported , 1 or greater than 1 means its good to go.

It means that the server on which you run the virt-install command is unable to use CPU virtualization extensions and is therefore emulating the CPU in software, using qemu.

This has nothing to do with OpenStack. It's also not an error but a warning, as the message says. The virtual machine will be rather slow but should be functional.