qemu-img create -f raw image_file 4G

qemu-system-x86_64 -enable-kvm -m 4G -cdrom "OS.iso" -boot order=c -drive file=image_file,if=virtio

qemu-system-x86_64 -enable-kvm -m 4G -cdrom "OS.iso" -boot order=d -drive file=image_file,format=raw

order=c vs order=d

if=virtio vs format=raw

qemu-system-x86_64 -enable-kvm -m 4G -cdrom "OS.iso" -boot order=c -drive file=image_file,if=virtio -device VGA,vgamem_mb=256

qemu-system-x86_64 -device help

qemu-system-x86_64 -device device_name,help

qemu-system-z86_64 -device VGA,help