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SubjectRe: HIGH MEMORY access
Date
Hello
>I don't think (2) is true. All set_fixmap does is to set a PTE into
>the kernel map, and PTEs point to physical addresses. The 1GB limitation
>is a virtual address mapping limitation, not physical.
>
set_fixmap relies on __end_of_fixed_addresses which is set to 1GB, correct?
The code checks for the address being less than __end_of_fixed_addresses. I
beleive this is the highest memory upto which the kernel has page
translations.

Please correct me if this is not the case and I can debug further where my
code is breaking.

Best Wishes :)
Lyle

>From: Andi Kleen <ak@muc.de>
>To: Lyle Coder <x_coder@hotmail.com>
>CC: ak@muc.de, mingo@chiara.csoma.elte.hu, linux-kernel@vger.rutgers.edu
>Subject: Re: HIGH MEMORY access
>Date: Sat, 4 Mar 2000 12:30:50 +0100
>
>On Sat, Mar 04, 2000 at 03:27:49AM +0100, Lyle Coder wrote:
> > Hi,
> > The function in question is get_smp_config
> >
> > 1) No it doesent call set_fixmap
> > 2) Even if it did, it wont be able to see > 1GB
>
>I don't think (2) is true. All set_fixmap does is to set a PTE into
>the kernel map, and PTEs point to physical addresses. The 1GB limitation
>is a virtual address mapping limitation, not physical.
>
>
>-Andi
>
> >
> > Ingo, am I correct?
> >
> > Best Wishes,
> > Lyle
> >
> >
> > >From: Andi Kleen <ak@muc.de>
> > >To: x_coder@hotmail.com (Lyle Coder)
> > >CC: linux-kernel@vger.rutgers.edu
> > >Subject: Re: HIGH MEMORY access
> > >Date: 04 Mar 2000 02:30:07 +0100
> > >
> > >x_coder@hotmail.com (Lyle Coder) writes:
> > >
> > > > Hello All,
> > > > I have a question. The BIOS engineers said that the MPS tables will
>be
> > >in
> > > > the highest region of the available RAM... greater than 1 GB if so
>much
> > > > memory is available.
> > > > Further more, the MPS tables will be in a region reported "unusable"
>by
> > >E820
> > > > (Thats mentioned in the E820 spec).
> > > >
> > > > So my question is this...
> > > > 1) How should we initialize mappings for arbitrary RAM above 1GB so
> > >early
> > > > on? Should we just set aside a page directory for temporary
> > >installation of
> > > > translations and provide a clean API to do so? We will need this
>for
> > >ACPI
> > > > and PAE too.
> > >
> > >Can't you just use set_fixmap, like the current smp code already does
>for
> > >MP bios tables ?
> > >
> > >
> > >-Andi
> > >
> > >--
> > >This is like TV. I don't like TV.
> >
> > ______________________________________________________
> > Get Your Private, Free Email at http://www.hotmail.com
> >
>
>--
>This is like TV. I don't like TV.

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