$ sudo pacman -S qemu
$ qemu-image create -f raw new_qemu_image 20G
OR
$ qemu-image create -f qcow2 new_qemu_image 20G
$ qemu-system-x86_64 -smp 2 -m 2G -enable-kvm -cdrom CentOS-7-x86_64-DVD-1708.iso -boot order=d new_qemu_image
# Installing CentOs...
$ qemu-system-x86_64 -k en-us -vga std -enable-kvm -m 2G -smp 2 -boot c new_qemu_image
# Running CentOs...
Ctrl+Alt+G (when you want to exit qemu gui) -k en-us (keymap) -smp 2 (number of cores)