Run the emulation with:

qemu-system-ppc64 \
    -M powernv11 \
    -kernel output/images/vmlinux \
    -append "console=hvc0 rootwait root=/dev/nvme0n1" \
    -device nvme,bus=pcie.3,addr=0x0,drive=drive0,serial=1234 \
    -drive file=output/images/rootfs.ext2,if=none,id=drive0,format=raw,cache=none \
    -device e1000e,netdev=net0,mac=C0:FF:EE:00:01:03,bus=pcie.1,addr=0x0 \
    -netdev user,id=net0 \
    -serial mon:stdio \
    -nographic # qemu_ppc64le_powernv11_defconfig

The login prompt will appear in the terminal window.
