From: Christoph Lameter <cl@linux-foundation.org>
To: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: y-goto@jp.fujitsu.com, tony.luck@intel.com,
linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org,
joerg.roedel@amd.com
Subject: Re: [Q] Why does dma_alloc_coherent() of ia64 GFP_DMA?
Date: Tue, 11 Nov 2008 20:32:46 +0000 [thread overview]
Message-ID: <Pine.LNX.4.64.0811111431440.26610@quilx.com> (raw)
In-Reply-To: <20081111145418P.fujita.tomonori@lab.ntt.co.jp>
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.
next prev parent reply other threads:[~2008-11-11 20:32 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-11-10 4:47 [Q] Why does dma_alloc_coherent() of ia64 GFP_DMA? Yasunori Goto
2008-11-10 12:59 ` Andi Kleen
2008-11-10 19:07 ` Robin Holt
2008-11-10 21:57 ` Christoph Lameter
2008-11-11 5:14 ` Yasunori Goto
2008-11-11 5:48 ` FUJITA Tomonori
2008-11-10 22:06 ` Christoph Lameter
2008-11-11 5:39 ` Yasunori Goto
2008-11-11 20:34 ` Christoph Lameter
2008-11-11 5:53 ` FUJITA Tomonori
2008-11-11 20:32 ` Christoph Lameter [this message]
2008-11-12 1:40 ` FUJITA Tomonori
2008-11-11 5:41 ` FUJITA Tomonori
2008-11-11 6:21 ` Yasunori Goto
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