To use the images built by OpenWrt with qemu, use the following commands:
For the little-endian image:
-qemu-system-mipsel -kernel bin/malta/openwrt-malta-le-vmlinux.elf -nographic
+qemu-system-mipsel -kernel bin/malta/openwrt-malta-le-vmlinux.elf -nographic -m 256
For the big-endian image:
-qemu-system-mips -kernel bin/malta/openwrt-malta-be-vmlinux.elf -nographic
+qemu-system-mips -kernel bin/malta/openwrt-malta-be-vmlinux.elf -nographic -m 256
and enjoy the system bootin.