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SubjectRe: [PATCH] x86: fix gart iommu using for amd 64 bit system
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On Wed, 25 Nov 2009 08:25:04 +0100
Ingo Molnar <mingo@elte.hu> wrote:

>
> * FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> wrote:
>
> > On Tue, 24 Nov 2009 16:26:45 +0100
> > Ingo Molnar <mingo@elte.hu> wrote:
> >
> > >
> > > * FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> wrote:
> > >
> > > > > don't think user will like to use SWIOTLB instead of swiotlb.
> > > >
> > > > I doubt that users care about a way to fix their problems.
> > >
> > > As far as swiotlb vs. GART goes, arguably a non-bouncing hw based
> > > solution (GART) is superior to a bouncing one (swiotlb), right?
> >
> > Yeah, but GART is not a real IOMMU that always does address
> > translation. If users want performance, they need 64bit DMA capable
> > devices to skip GART. With such devices, GART and SWIOTLB are same.
> >
> > So this hacky GART workaround is useful for only people who use non
> > 64bit DMA devices and broken BIOS with GART. IMO, it's not worth
> > having the workaround.
>
> Well, what Yinghai is saying that for that (nonzero) subset of people
> this change is a regression, and his patch fixes that. We dont do
> regressions so this needs to be addressed.

OK, I guess that I have to wait until nobody cares about GART.

Anyway, my patch fixes his issue without any regression:

http://marc.info/?l=linux-kernel&m=125907069703595&w=2

I'll post the second version of it after you merge the following fix:

http://marc.info/?l=linux-kernel&m=125910650500523&w=2


Thanks,


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