linux-kernel - Re: How to guarantee that kmalloc returns an address below 4GB

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Date:	Thu, 17 May 2007 11:46:58 -0700 (PDT)
From:	Christoph Lameter <clameter@....com>
To:	Stefan Richter <stefanr@...6.in-berlin.de>
cc:	"Cestonaro, Thilo (external)" 
	<Thilo.Cestonaro.external@...itsu-siemens.com>,
	linux-kernel@...r.kernel.org
Subject: Re: How to guarantee that kmalloc returns an address below 4GB

On Wed, 16 May 2007, Stefan Richter wrote:

> Cestonaro, Thilo (external) wrote:
> > is there an option for kmalloc, which I can use to allocate
> > a buffer which is in physical memory placed below 4GB?
> > Not in a remapped area.
> 
> GFP_DMA32

Nope. There are no general slabs available for DMA32.

You could use a dma slab by specifying GFP_DMA. However, on i386 and 
x86_64 this will get you memory in the precious first 16MB. On IA64 and 
other platforms you will get memory < 4GB.

Another option is to use the page allocator and specify GFP_DMA32.

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