Re: Reserving physical memory at boot time

Richard B. Johnson (root@chaos.analogic.com)
Wed, 4 Dec 2002 12:01:44 -0500 (EST)


On Wed, 4 Dec 2002, 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...
>
> -Mike
>

Well that parameter is not documented in:

.../linux-2.4.18/Documentation/kernel-parameters.txt.

Perhaps it's a 2.5.++ thing.

Cheers,
Dick Johnson
Penguin : Linux version 2.4.18 on an i686 machine (797.90 BogoMips).
Bush : The Fourth Reich of America

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