cbmem utility fails on newer linux kernels "Failed to mmap /dev/mem: Resource temporarily unavailable"
This has been going on for a while. Paul mentioned it here:
#1 Updated by Aaron Durbin over 4 years ago
This has a little more succinct issue as to what is going on:
In short, smbios and ACPI memory both live in cbmem. However, the two drivers use 2 different map() attributes covering sub regions within cbmem. The cbmem utility currently assumes a cacheable mapping attribute which is in conflict w/ the persistent uncacheable smbios mapping.