1 GB lowmem

[Benjamin Herrenschmidt]

On Wed, 2008-05-21 at 13:00 -0500, Rune Torgersen wrote:
> Hi
> 
> I am trying to enable 1 GB of lowmem on a Freescale 8280.
> In arch/ppc this was easilly done by:
> CONFIG_ADVANCED_OPTIONS=y
> CONFIG_HIGHMEM_START=0xfe000000
> CONFIG_LOWMEM_SIZE_BOOL=y
> CONFIG_LOWMEM_SIZE=0x40000000
> CONFIG_KERNEL_START_BOOL=y
> CONFIG_KERNEL_START=0xa0000000
> 
> This does not work in arch/powerpc. CPU hangs as soon as init starts.
> Any ideas what to look at, what to change?

You probably need to lower TASK_SIZE too.

> The reason I want to do this is because I cannot get highmem support to
> work when using CONFIG_PREEMPT_RT.
> (hitting a bug_on in kmap_atomic)

We should look into fixing that :-)

Ben.