Messages in this thread | | | Subject | Re: [Xen-devel] Re: [RFC] Make AGP work with IOMMU | From | David Woodhouse <> | Date | Wed, 05 Aug 2009 08:08:51 +0100 |
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On Wed, 2009-08-05 at 16:57 +1000, Dave Airlie wrote: > On Wed, Aug 5, 2009 at 4:44 PM, David Woodhouse<dwmw2@infradead.org> wrote: > > On Tue, 2009-08-04 at 16:52 -0700, Jeremy Fitzhardinge wrote: > >> 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. > > > > No, not 'most users'. But perhaps we should. > > > > All we've done so far is make intel-agp use the DMA API correctly. And > > that's conditional on CONFIG_DMAR. But we could make it unconditional, > > and make the other drivers do it too. The code is all fairly generic. > > > > Without an IOMMU, the overhead would be fairly minimal. > > > > I'm not sure how prevalent Xen is on AGP systems, I'm going to guess > not enough that anyone cares. Intel integrated chips are the only AGP > codebase user that are made any more, and they don't really use AGP > its just a legacy of the previous designs.
On the other hand, extending the existing code so that it uses the DMA API correctly _unconditionally_ rather than only for the Intel driver would be fairly simple and should be harmless...
-- dwmw2
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