Systemd and Custom Early Init Script

[Gordan Bobic]

I'm a not quite up to speed on systemd, so I'm hoping somebody here 
might point me in the right direction WRT the Fedora systemd init 
process flow.

I'm trying to work around bug 529153:
https://bugzilla.redhat.com/show_bug.cgi?id=529153

The closest to a workable solution I have come up with is:

echo -n 0000:00:1c.0:pcie04 > /sys/bus/pci_express/drivers/pciehp/unbind

So I need this to run as early as possible during the init sequence, as 
soon as /sys is mounted.

Before/after which services should this be done?

Gordan