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    SubjectRe: Reserving physical memory at boot time
    At 07:15 AM 12/4/2002 +0100, Duncan Sands wrote:
    >On Wednesday 04 December 2002 17:44, Mike Galbraith wrote:
    > > At 08:25 AM 12/4/2002 -0500, Richard B. Johnson wrote:
    > > >On 3 Dec 2002, Alan Cox wrote:
    > > > > On Tue, 2002-12-03 at 21:11, Richard B. Johnson wrote:
    > > > > > If you need a certain page reserved at boot-time you are out-of-luck.
    > > > >
    > > > > Wrong - you can specify the precise memory map of a box as well as use
    > > > > mem= to set the top of used memory. Its a painful way of marking a page
    > > > > and it only works for a page the kernel isnt loaded into.
    > > >
    > > >If you are refering to the "reserve=" kernel parameter, I don't
    > > >think it works for memory addresses that are inside existing RAM.
    > > >I guess if you used the "mem=" parameter to keep the kernel from
    > > >using that RAM, the combination might work, but I have never
    > > >tried it.
    > >
    > > reserve= is for IO ports (kernel/resource.c). I think Alan was referring to
    > > mem=exactmap.
    > >
    > > If Duncan didn't have the pesky requirement that his module work in an
    > > unmodified kernel, it would be easy to use __alloc_bootmem() to reserve an
    > > address range and expose via /proc. But alas...
    >
    >I actually said I was happy to modify the kernel! As for __alloc_bootmem(),
    >based on my quick reading of the implementation in 2.5.50, I don't see how
    >you can be sure it will give you a particular physical page. I would like to
    >either get the page I want, or fail.

    Sorry, mixed you up with someone else. Seems to me you could just create a
    new __setup("reservepage=", gimme_page) where gimme_page() allocates with
    goal set, and frees/aborts if what it gets back isn't exactly what you
    asked for.

    -Mike

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