Messages in this thread | | | Subject | Re: [PATCH v6 7/7] dma-iommu: account for min_align_mask | From | Robin Murphy <> | Date | Thu, 19 Aug 2021 10:03:09 +0100 |
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On 2021-08-17 02:38, David Stevens wrote: > From: David Stevens <stevensd@chromium.org> > > For devices which set min_align_mask, swiotlb preserves the offset of > the original physical address within that mask. Since __iommu_dma_map > accounts for non-aligned addresses, passing a non-aligned swiotlb > address with the swiotlb aligned size results in the offset being > accounted for twice in the size passed to iommu_map_atomic. The extra > page exposed to DMA is also not cleaned up by __iommu_dma_unmap, since > that function unmaps with the correct size. This causes mapping failures > if the iova gets reused, due to collisions in the iommu page tables. > > To fix this, pass the original size to __iommu_dma_map, since that > function already handles alignment. > > Additionally, when swiotlb returns non-aligned addresses, there is > padding at the start of the bounce buffer that needs to be cleared. > > Fixes: 1f221a0d0dbf ("swiotlb: respect min_align_mask") > Signed-off-by: David Stevens <stevensd@chromium.org> > --- > drivers/iommu/dma-iommu.c | 24 +++++++++++++----------- > 1 file changed, 13 insertions(+), 11 deletions(-) > > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c > index 6738420fc081..f2fb360c2907 100644 > --- a/drivers/iommu/dma-iommu.c > +++ b/drivers/iommu/dma-iommu.c > @@ -788,7 +788,6 @@ static dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page, > struct iommu_domain *domain = iommu_get_dma_domain(dev); > struct iommu_dma_cookie *cookie = domain->iova_cookie; > struct iova_domain *iovad = &cookie->iovad; > - size_t aligned_size = size; > dma_addr_t iova, dma_mask = dma_get_mask(dev); > > /* > @@ -796,8 +795,8 @@ static dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page, > * page aligned, we don't need to use a bounce page. > */ > if (dev_use_swiotlb(dev) && iova_offset(iovad, phys | size)) { > - void *padding_start; > - size_t padding_size; > + void *tlb_start; > + size_t aligned_size, iova_off, mapping_end_off; > > aligned_size = iova_align(iovad, size); > phys = swiotlb_tbl_map_single(dev, phys, size, aligned_size, > @@ -806,23 +805,26 @@ static dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page, > if (phys == DMA_MAPPING_ERROR) > return DMA_MAPPING_ERROR; > > - /* Cleanup the padding area. */ > - padding_start = phys_to_virt(phys); > - padding_size = aligned_size; > + iova_off = iova_offset(iovad, phys); > + tlb_start = phys_to_virt(phys - iova_off); > > if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) && > (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL)) { > - padding_start += size; > - padding_size -= size; > + /* Cleanup the padding area. */ > + mapping_end_off = iova_off + size; > + memset(tlb_start, 0, iova_off); > + memset(tlb_start + mapping_end_off, 0, > + aligned_size - mapping_end_off); > + } else { > + /* Nothing was sync'ed, so clear the whole buffer. */ > + memset(tlb_start, 0, aligned_size); > } > - > - memset(padding_start, 0, padding_size); > } > > if (!coherent && !(attrs & DMA_ATTR_SKIP_CPU_SYNC)) > arch_sync_dma_for_device(phys, size, dir); > > - iova = __iommu_dma_map(dev, phys, aligned_size, prot, dma_mask); > + iova = __iommu_dma_map(dev, phys, size, prot, dma_mask);
I still don't see how this preserves min_align_mask if it is larger than the IOVA granule (either way this change here does nothing since the first thing __iommu_dma_map() does is iova_align() the size right back anyway).
Robin.
> if (iova == DMA_MAPPING_ERROR && is_swiotlb_buffer(phys)) > swiotlb_tbl_unmap_single(dev, phys, size, dir, attrs); > return iova; >
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