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    Subject[PATCH 5.15 601/917] iommu/dma: Fix sync_sg with swiotlb
    Date
    From: David Stevens <stevensd@chromium.org>

    [ Upstream commit 08ae5d4a1ae96b72222e7b02d072bb997ff29dac ]

    The is_swiotlb_buffer function takes the physical address of the swiotlb
    buffer, not the physical address of the original buffer. The sglist
    contains the physical addresses of the original buffer, so for the
    sync_sg functions to work properly when a bounce buffer might have been
    used, we need to use iommu_iova_to_phys to look up the physical address.
    This is what sync_single does, so call that function on each sglist
    segment.

    The previous code mostly worked because swiotlb does the transfer on map
    and unmap. However, any callers which use DMA_ATTR_SKIP_CPU_SYNC with
    sglists or which call sync_sg would not have had anything copied to the
    bounce buffer.

    Fixes: 82612d66d51d ("iommu: Allow the iommu/dma api to use bounce buffers")
    Signed-off-by: David Stevens <stevensd@chromium.org>
    Reviewed-by: Robin Murphy <robin.murphy@arm.com>
    Reviewed-by: Christoph Hellwig <hch@lst.de>
    Link: https://lore.kernel.org/r/20210929023300.335969-2-stevensd@google.com
    Signed-off-by: Joerg Roedel <jroedel@suse.de>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/iommu/dma-iommu.c | 33 +++++++++++++--------------------
    1 file changed, 13 insertions(+), 20 deletions(-)

    diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
    index 896bea04c347e..c4d205b63c582 100644
    --- a/drivers/iommu/dma-iommu.c
    +++ b/drivers/iommu/dma-iommu.c
    @@ -828,17 +828,13 @@ static void iommu_dma_sync_sg_for_cpu(struct device *dev,
    struct scatterlist *sg;
    int i;

    - if (dev_is_dma_coherent(dev) && !dev_is_untrusted(dev))
    - return;
    -
    - for_each_sg(sgl, sg, nelems, i) {
    - if (!dev_is_dma_coherent(dev))
    + if (dev_is_untrusted(dev))
    + for_each_sg(sgl, sg, nelems, i)
    + iommu_dma_sync_single_for_cpu(dev, sg_dma_address(sg),
    + sg->length, dir);
    + else if (!dev_is_dma_coherent(dev))
    + for_each_sg(sgl, sg, nelems, i)
    arch_sync_dma_for_cpu(sg_phys(sg), sg->length, dir);
    -
    - if (is_swiotlb_buffer(dev, sg_phys(sg)))
    - swiotlb_sync_single_for_cpu(dev, sg_phys(sg),
    - sg->length, dir);
    - }
    }

    static void iommu_dma_sync_sg_for_device(struct device *dev,
    @@ -848,17 +844,14 @@ static void iommu_dma_sync_sg_for_device(struct device *dev,
    struct scatterlist *sg;
    int i;

    - if (dev_is_dma_coherent(dev) && !dev_is_untrusted(dev))
    - return;
    -
    - for_each_sg(sgl, sg, nelems, i) {
    - if (is_swiotlb_buffer(dev, sg_phys(sg)))
    - swiotlb_sync_single_for_device(dev, sg_phys(sg),
    - sg->length, dir);
    -
    - if (!dev_is_dma_coherent(dev))
    + if (dev_is_untrusted(dev))
    + for_each_sg(sgl, sg, nelems, i)
    + iommu_dma_sync_single_for_device(dev,
    + sg_dma_address(sg),
    + sg->length, dir);
    + else if (!dev_is_dma_coherent(dev))
    + for_each_sg(sgl, sg, nelems, i)
    arch_sync_dma_for_device(sg_phys(sg), sg->length, dir);
    - }
    }

    static dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
    --
    2.33.0


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