Re: memory beyond4GB invisible to the system even though CONFIG_HIGHMEM64G=y

From: Roland Dreier
Date: Tue Jan 13 2009 - 21:22:33 EST


> I am running kernel 2.6.28 on a computer with 8GB RAM. The BIOS
> detects all 8GB, yet
>
> jk@as12:~$ free
> total used free shared buffers cached
> Mem: 3622504 799696 2822808 0 90936 369604
> -/+ buffers/cache: 339156 3283348
> Swap: 6867776 0 6867776

The message in your kernel log:

[ 0.000000] WARNING: BIOS bug: CPU MTRRs don't cover all of memory, losing 4096MB of RAM.
[ 0.000000] ------------[ cut here ]------------
[ 0.000000] WARNING: at arch/x86/kernel/cpu/mtrr/main.c:1662 mtrr_trim_uncached_memory+0x283/0x2a4()

is a clue. You might want to look for a BIOS update for your
motherboard.

- R.
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