Re: [Q] Why does dma_alloc_coherent() of ia64 GFP_DMA?

[FUJITA Tomonori]

On Mon, 10 Nov 2008 16:06:52 -0600 (CST)
Christoph Lameter <cl@xxxxxxxxxxxxxxxxxxxx> wrote:

> On Mon, 10 Nov 2008, Yasunori Goto wrote:
> 
> > Even if a device allows over 4G access and the driver doesn't specify
> > GFP_DMA, dma_alloc_coherent() returns under 4G area.
> 
> GFP_DMA can become 0 for configurations that have
> !CONFIG_ZONE_DMA. Then all of memory is available.
> 
> The call is subarch specific. So f.e. Altix sn_dma_alloc_coherent does
> not set __GFP_DMA.

Is it because it does some kinda address translation
(provider->dma_map_consistent) later? The zone flag is meaningless if
you do sorta address translation (e.g. hardware IOMMU like VT-d).
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