linux-kernel - Re: Reserving a fixed physical address page of RAM.

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Message-ID: <1e62d1370611301056h155cd7bfydb437b8248d7844e@mail.gmail.com>
Date:	Thu, 30 Nov 2006 23:56:46 +0500
From:	"Fawad Lateef" <fawadlateef@...il.com>
To:	"Jon Ringle" <JRingle@...tical.com>
Cc:	"Dave Airlie" <airlied@...il.com>,
	"Robert Hancock" <hancockr@...w.ca>, linux-kernel@...r.kernel.org
Subject: Re: Reserving a fixed physical address page of RAM.

On 11/30/06, Jon Ringle <JRingle@...tical.com> wrote:
> Jon Ringle wrote:
> > Fawad Lateef wrote:
<snip>
> > > >
> > > > Index: linux/arch/arm/mm/init.c
> > > >
> > ===================================================================
> > > > --- linux.orig/arch/arm/mm/init.c       2006-11-30
> > > 11:03:00.000000000
> > > > -0500
> > > > +++ linux/arch/arm/mm/init.c    2006-11-30
> > 11:09:09.000000000 -0500
> > > > @@ -429,6 +429,10 @@
> > > >         unsigned long addr;
> > > >         void *vectors;
> > > >
> > > > +#ifdef CONFIG_MACH_VERTICAL_RSC4
> > > > +       reserve_bootmem (0x0ffff000, 0x1000); #endif
> > > > +
> > > >         /*
> > > >          * Allocate the vector page early.
> > > >          */
> > > >
> > > >
> > >
> > > I think you can do like this but can't say accurately
> > because I havn't
> > > worked on arm architecture and also you havn't mentioned your
> > > kernel-version or function (in file
> > > arch/arm/mm/init.c) which you are going to do call reserve_bootmem !
> >
> > Kernel version is 2.6.16.29 and the reserve_bootmem() call
> > above is at the top of the function devicemaps_init().
>
> Is there some way I can verify that the above works? I've tried the
> following to try to get info on the reservation:
>         # cat /proc/iomem
>         # cat /proc/meminfo
>         # cat /proc/slabinfo
>         # echo m > /proc/sysrq-trigger
>
> The only one that hints that this might have worked is the `echo m >
> /proc/sysrq-trigger` in that I see the reserved pages count one larger
> than using a kernel without this patch. Does this mean that the page I
> reserved won't get used by Linux for any purpose?
>

I havn't looked at " # echo m /proc/sysrq-trigger" till now but I am
almost sure that it will reserve/work because calling reserve_bootmem
internally sets the bit representing physical memory page (CMIIW).


-- 
Fawad Lateef
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