[seL4] vspace_reserve_range_at

Hello, I am trying to map a device 1:1 in my root thread. When I try to reserve a range at the specific location, using the vspace_reserve_range_at() function I get the following error: ERROR:sel4utils_reserve_range_at_no_alloc:585: Range not available at 0xf8f00000, size 0x64000. Is there something that the kernel or the root task needs to do before this to make this range available for reservation? BTW, I am still using seL4 1.0. Thanks, Robbie VanVossen DornerWorks