Messages in this thread | | | Subject | Re: [PATCH v6 3/7] dma-iommu: skip extra sync during unmap w/swiotlb | From | Robin Murphy <> | Date | Thu, 19 Aug 2021 09:59:47 +0100 |
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On 2021-08-17 02:38, David Stevens wrote: > From: David Stevens <stevensd@chromium.org> > > Calling the iommu_dma_sync_*_for_cpu functions during unmap can cause > two copies out of the swiotlb buffer. Do the arch sync directly in > __iommu_dma_unmap_swiotlb instead to avoid this. This makes the call to > iommu_dma_sync_sg_for_cpu for untrusted devices in iommu_dma_unmap_sg no > longer necessary, so move that invocation later in the function.
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
> Signed-off-by: David Stevens <stevensd@chromium.org> > Reviewed-by: Christoph Hellwig <hch@lst.de> > --- > drivers/iommu/dma-iommu.c | 11 ++++++----- > 1 file changed, 6 insertions(+), 5 deletions(-) > > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c > index 8098ce593640..5dd2c517dbf5 100644 > --- a/drivers/iommu/dma-iommu.c > +++ b/drivers/iommu/dma-iommu.c > @@ -504,6 +504,9 @@ static void __iommu_dma_unmap_swiotlb(struct device *dev, dma_addr_t dma_addr, > if (WARN_ON(!phys)) > return; > > + if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) && !dev_is_dma_coherent(dev)) > + arch_sync_dma_for_cpu(phys, size, dir); > + > __iommu_dma_unmap(dev, dma_addr, size); > > if (unlikely(is_swiotlb_buffer(phys))) > @@ -853,8 +856,6 @@ static dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page, > static void iommu_dma_unmap_page(struct device *dev, dma_addr_t dma_handle, > size_t size, enum dma_data_direction dir, unsigned long attrs) > { > - if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) > - iommu_dma_sync_single_for_cpu(dev, dma_handle, size, dir); > __iommu_dma_unmap_swiotlb(dev, dma_handle, size, dir, attrs); > } > > @@ -1062,14 +1063,14 @@ static void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sg, > struct scatterlist *tmp; > int i; > > - if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) > - iommu_dma_sync_sg_for_cpu(dev, sg, nents, dir); > - > if (dev_is_untrusted(dev)) { > iommu_dma_unmap_sg_swiotlb(dev, sg, nents, dir, attrs); > return; > } > > + if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) > + iommu_dma_sync_sg_for_cpu(dev, sg, nents, dir); > + > /* > * The scatterlist segments are mapped into a single > * contiguous IOVA allocation, so this is incredibly easy. >
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