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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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