I'm not lucky enough to have a PCIe but I think that this may help:
Darwin is the kernel of Mac OS X and it's Open Source. Mac OS X support PCIe and Darwin should also support it. Since Darwin is *BSD based the drivers for PCIe (I have no idea what software is needed for using PCIe) should be easily ported to other *nix OSs. You can searh in their wikis or faqs, I think the URL is
http://opendarwin.org