How to alloc highmem page below 4GB on i386?

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To: LKML <linux-kernel@...>, <linux-mm@...>
Date: Monday, June 30, 2008 - 2:03 pm

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?

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     -- Pierre Ossman

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  rdesktop, core developer          http://www.rdesktop.org

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Messages in current thread:
How to alloc highmem page below 4GB on i386?, Pierre Ossman, (Mon Jun 30, 2:03 pm)
Re: How to alloc highmem page below 4GB on i386?, Pierre Ossman, (Fri Jul 4, 1:58 pm)
Re: How to alloc highmem page below 4GB on i386?, Arjan van de Ven, (Fri Jul 4, 2:12 pm)
Re: How to alloc highmem page below 4GB on i386?, Pierre Ossman, (Fri Jul 4, 4:23 pm)
Re: How to alloc highmem page below 4GB on i386?, Arjan van de Ven, (Fri Jul 4, 4:37 pm)
Re: How to alloc highmem page below 4GB on i386?, Pierre Ossman, (Fri Jul 4, 6:02 pm)
Re: How to alloc highmem page below 4GB on i386?, Arjan van de Ven, (Fri Jul 4, 6:24 pm)