[ofa-general] mmap() and ibv_reg_mr() and RDMA

[Roland Dreier]

 > this area is mapped via the character device and with
 > the help of remap_pfn_range() into userspace... this works fine i can
 > access it from userspace and write/read from it:

I think that's the problem.  remap_pfn_range() sets VM_PFNMAP on the
vma used to map the pfns.  When ibv_reg_mr() calls into the kernel to
do the actual mapping, it ends up doing get_user_pages() which fails
in vm_normal_page() for such a vma.

I don't immediately see a good way to handle this.

 - R.