Known issue. Use 3.8.3 and higher with qemu 1.4+. There's a known
issue with qemu 1.3 with newer kernels (>3.7).
You'll also need to adjust the boot script to include the DTB, eg:
qemu-system-arm -machine vexpress-a9 -m 1024 -nographic -net nic -net user \
-append "console=ttyAMA0,115200n8 rw root=/dev/mmcblk0p2 rootwait
-kernel "$KERN" \
-initrd "$RAMFS" \
-sd "$IMAGE" \
The F18 Vexpress image includes the DTB option in the boot script already.
Should work after that, let us know if you have any further issues.