How to alloc highmem page below 4GB on i386?

From: Pierre Ossman
Date: Mon Jun 30 2008 - 14:03:42 EST


Simple question. How do I allocate a page from highmem, that's still
within 32 bits? x86_64 has the DMA32 zone, but i386 has just HIGHMEM.
As most devices can't DMA above 32 bit, I have 3 GB of memory that's
not getting decent usage (or results in needless bouncing). What to do?

I tried just enabling CONFIG_DMA32 for i386, but there is some guard
against too many memory zones. I'm assuming this is there for a good
reason?

--
-- Pierre Ossman

Linux kernel, MMC maintainer http://www.kernel.org
rdesktop, core developer http://www.rdesktop.org

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