For as much as it's pretty evident it's not a warning or a error, that ! still quite manage to attract attention (and it seems I'm not the only one https://bugs.launchpad.net/ubuntu/+source/linux/+bug/252354) http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/arch/x86/kernel/pci-calgary_64.c?id=f91eb62f71b31e69e405663ff8d047bc3b9f7525#n1410