On Sat, 13 Feb 2021, Charlie Gibbs wrote:
> [This would probably be an FAQ if I knew the proper incantation...]
Well, sorta....
> I realized recently that a box I've been running for a while isn't seeing
> all of its installed memory. The BIOS screens indicate that 8GB is
> installed, but Debian (recently upgraded to Buster) only sees a bit over
> 3GB.
>
> cjg@dragon:~$ head -1 /proc/meminfo
> MemTotal: 3331096 kB
>
> During boot I noticed the following message:
>
> [ 0.012080] WARNING: BIOS bug: CPU MTRRs don't cover all of memory,
> losing 4800MB of RAM.
1. UPDATE THE BIOS (UEFI), really.
2. Once it is up-to-date, review BIOS settings. You might have
something strange in there. Check stuff like "memory window", anything
that make mentions to "hole" (PCI, memory, etc), and memory set aside
for GPUs, etc.
Maybe reset BIOS/UEFI to defaults, and change one setting at a time
until it is back the way you want it, to isolate what setting might be
causing it. -- be careful to ensure the boot stuff is correct for what
you need, though. Copy the settings you have to paper before you reset.
Only if all else fails, you try the kernel command line switches to mess
with this :-(
> Is there some sort of HOWTO that covers this stuff? Where do I go from
> here?
Try fixing the real problem first (whatever is making your BIOS set
these incorrectly). Your system might become quite unpredictable
otherwise, depending on the reason these MTRRs are set like that.
--
Henrique Holschuh
Paul Duncan
Lead Marine Technician, RV Falkor
SCHMIDT OCEAN INSTITUTE
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