Hi there, The file "include/linux/iommu.h" makes use of function ERR_PTR() but appears to not include "include/linux/err.h" directly or indirectly (where ERR_PTR() is defined). I ran into this issue while trying to build virtualbox-modules on Gentoo Linux with kernel version 3.6.11, but it looks like there is still no reference in kernel 3.7.1 either. I was asked to forward this for clarification here, so here i am.. :P Cheers, Oliver.
Downstream bug at https://bugs.gentoo.org/show_bug.cgi?id=448784
So virtualbox should include both files