about build failed

[xcc-123]

i want to create linuxboot.rom for qemu,so
first run
make KERNEL = path/to/bzImage INITRD= path/to/initrd.cpio.xz config
then run
make
when create merged.vol,it failed as below:

./bin/create-ffs
--compress
--type FIRMWARE_VOLUME_IMAGE
build/qemu/rom/0x00084000/9e21fd93-9c72-4c15-8c4b-e77f1db2d792/0.fv build/qemu/dxe.vol build/qemu/qemu.txt
| ./bin/create-fv
--size 0x748000
-o build/qemu/merged.vol
alignment attribute 05
FV pad failed
build/qemu/merged.vol: Unable to create FV
boards/qemu/Makefile.board:43: recipe for target 'build/qemu/merged.vol' failed
make: *** [build/qemu/merged.vol] Error 255

Is there anyone know what the possible reason is ? thanks