linux-kernel - Re: memory beyond4GB invisible to the system even though CONFIG

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Date:	Tue, 13 Jan 2009 22:10:18 -0500
From:	"James Kirin" <james.kirin40@...il.com>
To:	"Roland Dreier" <rdreier@...co.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: memory beyond4GB invisible to the system even though CONFIG_HIGHMEM64G=y

Thank you for your reply, Roland. Unfortunately, this continues
happening after having installed the most recent version of the BIOS
available from Dell.

I understand this is a problem in the BIOS and not the kernel, but is
there a way to have the kernel work around this bug in the BIOS and
make that memory accessible? Eg,

http://www.gossamer-threads.com/lists/linux/kernel/991748#991748

The difference seems to be that the BIOS on this machine I am using
does list 8GB memory available.

Thanks for any help,

James

On Tue, Jan 13, 2009 at 9:22 PM, Roland Dreier <rdreier@...co.com> wrote:
>  > I am running kernel 2.6.28 on a computer with 8GB RAM. The BIOS
>  > detects all 8GB, yet
>  >
>  > jk@...2:~$ 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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