Run the emulation with:

 qemu-system-mips64 -M malta -kernel output/images/vmlinux -serial stdio -hda output/images/rootfs.ext2 -append "root=/dev/hda"

The login prompt will appear in the terminal that started Qemu. The
graphical window is the framebuffer. No keyboard support has been
enabled.

This configuration is known to be flaky.

Tested with QEMU 1.6.1
