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.
Environment
- Red Hat Enterprise Linux 6
- Microsoft Hyper-V hypervisor
- also seen with VMware ESXi hypervisor
- can be also seen on some hardware configurations
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