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Re: [Xen-devel] Re: [RFC] Make AGP work with IOMMU

To: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Re: [RFC] Make AGP work with IOMMU
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Tue, 04 Aug 2009 16:52:38 -0700
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, Zhenyu Wang <zhenyu.z.wang@xxxxxxxxx>, Joerg Roedel <joerg.roedel@xxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx, Dave Airlie <airlied@xxxxxxxxx>, Keir Fraser <kier.fraser@xxxxxxxxxxxxx>
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On 07/29/09 02:36, David Woodhouse wrote:
> On Wed, 2009-07-29 at 18:43 +1000, Dave Airlie wrote:
>>>> don't suppose we want page_to_gart or is the double function nicer?
>>> I pondered that briefly. But then observed that phys_to_gart() and
>>> gart_to_phys() _always_ describe an identity mapping, so perhaps they
>>> could just be ditched completely?
>> Yeah that could work too, no idea why they were introduced, well before my 
>> time.
> http://git.infradead.org/users/dwmw2/iommu-agp.git?a=commitdiff;h=8bf2f3a9
> It was introduced by Keir in 2005 for Xen (commit 07eee78e). I suspect
> it can die though, and that the right answer there is also to use the
> DMA API correctly.

And just when I have patches to use them for their original purpose...

Looking back over the thread, are you saying that most users are already
using the DMA API correctly for AGP accesses?  If that's true then we
should be just fine.


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