kernel boot failure with ipxe on uefi mode

[birkhoff]

Hello, I've been trying to load linux kernel and initrd directly with ipxe on uefi mode. The kernel and initrd I have tried are from hp scripting toolkit linux 10.02-1. The ipxe command I've tried as follows:

iPXE>kernel http://10.4.16.100/vmlinuz initrd=initrd.img
http://10.4.16.100/vmlinuz...ok
iPXE>initrd http://10.4.16.100/initrd.img
http://10.4.16.100/initrd.img...ok
iPXE>boot

then it output:
VFS: Cannot open root device "(null)" or unknown-block(0,0)
Please append a correct "root=" boot option; here are the available partitions:
kernel pannic - not syncing:VFS: Unable to mount root fs on unknown-block(0,0)

While I used the same kernel and another initrd from fedora, it worked fine.
I also tried to boot the kernel with pxe directly using bootx64.efi and elilo.conf, it worked fine too. And If I chain bootx64.efi in ipxe command line, it would boot into grub2 command line and then I don't know what to do.
Since I need use the tools in the hp scripting toolkits linux, i have to load the kernel and initrd.img from hp scripting toolkits linux directly.

Is there anyone can help me with this problem?