[CentOS-virt] Unknown boot option `pciback.hide=(09:04.0)': ignoring

Good morning,

I need to use pciback.hide to hide a pci card because I want to pci
passthrough that card to a domU. My hardware neither supports Intel-Vt-d
nor AMD's IOMMU. Unfortunately this doesn't seem to work in Centos 54
anymore. I guess it doesn't work because it is not compiled into the
kernel, but as a module. I got the following error in dmesg and the pci
device is still listed in dom0 in lspci.

Bootdata ok (command line is ro root=/dev/dom0/root pciback.hide=(09:04.0))
Kernel command line: ro root=/dev/dom0/root pciback.hide=(09:04.0)
Unknown boot option `pciback.hide=(09:04.0)': ignoring

I also tried to update initrd to include the module but got the same
error message as above.

mkinitrd --with=pciback /boot/initrd-2.6.18-164.6.1.el5xen_pcipt
2.6.18-164.6.1.el5xen
title CentOS (2.6.18-164.6.1.el5xen PCI PT)
    root (hd1,0)
    kernel /xen.gz-2.6.18-164.6.1.el5
    module /vmlinuz-2.6.18-164.6.1.el5xen ro root=/dev/dom0/root
pciback.hide=(09:04.0)
    module /boot/initrd-2.6.18-164.6.1.el5xen_pcipt

Is there any option to use pciback.hide kernel parameter without
compiling a custom kernel?

Thanks in advance
Günter Zimmermann