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Date: Fri, 6 Nov 2009 12:34:22 +0900 From: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp> To: alex.williamson@...com Cc: fujita.tomonori@....ntt.co.jp, dwmw2@...radead.org, iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org, akpm@...ux-foundation.org Subject: Re: [PATCH] intel-iommu: Obey coherent_dma_mask for alloc_coherent on passthrough On Thu, 05 Nov 2009 20:19:52 -0700 Alex Williamson <alex.williamson@...com> wrote: > On Fri, 2009-11-06 at 11:41 +0900, FUJITA Tomonori wrote: > > On Wed, 04 Nov 2009 15:59:34 -0700 > > Alex Williamson <alex.williamson@...com> wrote: > > > @@ -2582,7 +2582,7 @@ static dma_addr_t __intel_map_single(struct device *hwdev, phys_addr_t paddr, > > > BUG_ON(dir == DMA_NONE); > > > > > > if (iommu_no_mapping(hwdev)) > > > - return paddr; > > > + return paddr + size > dma_mask ? 0 : paddr; > > > > You can use dma_capable(hwdev, paddr, size) here. > > Good thought, however __intel_map_single() gets called with either the > dma_mask or the coherent_dma_mask. dma_capable() only checks dma_mask, > so would only work for one of the callers. Oops, you are right. > > > domain = get_valid_domain_for_dev(pdev); > > > if (!domain) > > > @@ -2767,7 +2767,15 @@ static void *intel_alloc_coherent(struct device *hwdev, size_t size, > > > > > > size = PAGE_ALIGN(size); > > > order = get_order(size); > > > - flags &= ~(GFP_DMA | GFP_DMA32); > > > + > > > + if (!iommu_no_mapping(hwdev)) > > > + flags &= ~(GFP_DMA | GFP_DMA32); > > > + else if (hwdev->coherent_dma_mask != DMA_BIT_MASK(64)) { > > > + if (hwdev->coherent_dma_mask < DMA_BIT_MASK(32)) > > > + flags |= GFP_DMA; > > > + else > > > + flags |= GFP_DMA32; > > > + } > > > > This is fine for 2.6.32 but we'll cleanly fix this by using > > swiotlb_dma_ops later, right? > > I'm open to suggestions. I don't really understand why we dropped > swiotlb for passthrough mode in 2.6.32 to start with. It seems like we > now have a couple corner cases where we have to either hope for the best > or effectively ignore the request to use passthrough. Thanks, I think that the cleanest solution is setting up swiotlb_dma_ops for passthrough devices (and devices not behind pci, etc). Calgary IOMMU does the same for years. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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