Can Linux live without DMA zone?

[Jun Sun]

I am trying to reserve a block of memory (>16MB) starting from 0 and hide it 
from kernel.  A consequence is that DMA zone now has size 0.  That causes
many drivers to grief (OOMs).

I see two ways out:

1. Modify individual drivers and convince them not to alloc with GFP_DMA.
   I have been trying to do this but do not seem to see an end of it.  :)

2. Simply lie and increase MAX_DMA_ADDRESS to really big (like 1GB) so that
   the whole memory region belongs to DMA zone.

#2 sounds pretty hackish.  I am sure something bad will happen
sooner or later (like what?). But so far it appears to be working fine.

The fundamental question is: Has anybody tried to run Linux without 0 sized
DMA zone before?  Am I doing something that nobody has done before (which is
something really hard to believe these days with Linux :P)?

Cheers.

Jun
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