Re: memory management issue (Re: another regression on Efika)

[Robert Millan <rmh@aybabtu.com>]

On Wed, Jul 25, 2007 at 06:25:24PM -0500, Hollis Blanchard wrote:
> On 7/25/07, Robert Millan <rmh@aybabtu.com> wrote:
> >On Wed, Jul 25, 2007 at 12:51:27PM -0500, Hollis Blanchard wrote:
> >>
> >> I was indeed trying to make it absolute. GRUB is linked at 0x10000, or
> >> 64KB. Add in all the modules and you still are only using a couple
> >> hundred KB.
> >
> >But if GRUB is linked at 0x10000, how come the firmware loads it since
> >that's below the 0x19111e4 limit?  (or am I missing some physical vs 
> >logical
> >issue here?)
> 
> No, you are correct; obviously firmware is doing something wrong. The
> question is can we accommodate it, and if so, how?
>
> [...]
>
> 25MB; we know this because we managed to load grub there. This
> undoubtedly an Efika firmware bug, but as I described earlier I think
> we can devise another workaround for it without hurting the common
> case.

I contacted Sven Luther (CCed) about it.  This is what he said:

  17:19 <svenl> nyu: this is another not really bug but ugly feature of the efika firmware, not present in the pegasos branch.
  17:19 <svenl> the problem is that the graphic memory is mapped at the start, and the firmware is located from 16MB to 24MB or so, maybe a bit more with the
                stack.
  17:20 <svenl> normally; the area between 0 and 16MB, except for the interrupt vectors, should be available.

So we could do as you suggested before, and only claim memory below heaplimit
when possible, or we could register the area between end of grub image and
16MB as claimed.  That is, assuming 0x1000000 (or whatever the exact address
is) is exactly the last unused address in that region.

Though, the idea of registering an area as claimed without telling the firmware
about it sounds like a no-no to me.  What do you think?  Is it really worth it?

-- 
Robert Millan

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