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Date: Tue, 11 Nov 2008 14:32:46 -0600 (CST)
From: Christoph Lameter <cl@...ux-foundation.org>
To: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
cc: y-goto@...fujitsu.com, tony.luck@...el.com,
linux-ia64@...r.kernel.org, linux-kernel@...r.kernel.org,
joerg.roedel@....com
Subject: Re: [Q] Why does dma_alloc_coherent() of ia64 GFP_DMA?
On Tue, 11 Nov 2008, FUJITA Tomonori wrote:
> 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).
Yes it can do address translation. Therefore a < 4G address can show up at
any 64 bit address. So no need for a special DMA zone. The same is true
for more x86_64 platforms that have an IOMMU.
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