Incorrect MTRR setup made by buggy BIOS results in losing RAM in RHEL6

Issue

RHEL6 has an issue with detecting full amount of memory on some hardware or as a guest system under some hypervisors.

Typically it happens while running RHEL6 kernel under Microsoft Hyper-V hypervisor. In this case kernel cannot address more than 64 GiB of RAM.

This issue is also seen on VMware ESXi hypervisor, where the limit of 1 TiB of RAM applies.

If the warning mentioned above is seen on a hardware platform, the amount of lost memory is usually insignificantly small.