2GB address space limit on 32-bit PowerPC Macintosh

Kumar Gala kumar.gala at freescale.com
Mon May 16 16:21:13 EST 2005

On May 16, 2005, at 12:52 AM, Benjamin Herrenschmidt wrote:

> > >
>  > > We need to fix that too :) Though I suppose we can just switch 
> that to
>  > >  page tables, I don't really see the point of using a BAT here...
>  >
> > Are the embedded board ports broken because of similar
> > io_block_mapping() calls or for some other reason?
>  Mostly because of the above, though some embedded ports may do even 
> more
>  horrible things for what i know :) The problem with io_block_mapping()
> is that 1) it lets you put those BARs or mappings where you want, and 
> 2)
>  you end up with plenty of code hard-coding this virtual address here 
> or
>  there that need to be fixed.

I'm interested to see if Paul is aware of any other embedded port 
issues, since he mentioned the problem there.

Agreed, the other problem that comes up from time to time due to 
io_block_mapping() that I've see is problem with modules not working 
because the kernel doesn't think it has any vmalloc() space left.

> > I'm in agreement that we should bump TASK_SIZE to 3GB and fix things,
> > how about after 2.6.12 is out?
> Agreed. I'll fix PReP/CHRP/pmac & defconfig. Every embedded board
>  vendor/maintainer will be responsible for fixing his/her boards 
> support.

Agreed.  We should probably send an email to linuxppc-embedded with a 
more proper subject line to let people know.

- kumar

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