Messages in this thread | | | Date | Wed, 25 Nov 2009 08:25:04 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] x86: fix gart iommu using for amd 64 bit system |
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* 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.
Thanks,
Ingo
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