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SubjectRe: Does Linux have plan to support memory hole remapping?

* Matti Aarnio <> wrote:

> On Wed, Apr 09, 2008 at 10:01:59AM +0200, Andi Kleen wrote:
> > "Zhao Forrest" <> writes:
> > >
> > > As we can see from above information that the physical memory in system
> > > is 32768MB(32GB). However OS is only using about
> > > (32768-512)MB(MemTotal: 33010240 kB). Does this mean that this
> > > linux kernel can't use the physical memory remapped
> > > from (4G-512M, 4G) to (32G, 32G+512M)?
> >
> > The linux kernel can only use the memory passed to it by the BIOS.
> > Sometimes they need special BIOS setup options to enable remapping. If
> > there are no such options and you can't upgrade it you're out of luck
> >
> > I would suggest you contact your system vendor.
> I second that. On my home machine I have early ASUS AMD x64 board
> from a few years ago. For it I did buy CPU with this memory mapping
> hardware inside, but the BIOS did not support it correctly until a
> year or two latter, thus I was not able to use all of 4 GB of memory I
> had installed there. There was support in BIOS from start, but it did
> things wrong.

having said that - but we'll still consider sane looking patches that
allow the remapping of otherwise inactive RAM. [ We might not even have
to touch the system chipset beyond what Linux already knows about it: in
theory someone might want to try a hack to GART remap such RAM areas and
use a sparse mem map entry to map it to Linux - if the identity of that
RAM is crystal-clear and there's enough GART space available. But even
then it's probably still at best a dangerous and fragile hack. ]


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