linux-kernel - [PATCH v2 2/4] dma-iommu: fix arch_sync

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Message-Id: <20210709033502.3545820-3-stevensd@google.com>
Date:   Fri,  9 Jul 2021 12:35:00 +0900
From:   David Stevens <stevensd@...omium.org>
To:     Robin Murphy <robin.murphy@....com>
Cc:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Tom Murphy <murphyt7@....ie>, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, David Stevens <stevensd@...omium.org>
Subject: [PATCH v2 2/4] dma-iommu: fix arch_sync_dma for map with swiotlb

From: David Stevens <stevensd@...omium.org>

When calling arch_sync_dma, we need to pass it the memory that's
actually being used for dma. When using swiotlb bounce buffers, this is
the bounce buffer. Move arch_sync_dma into the __iommu_dma_map_swiotlb
helper, so it can use the bounce buffer address if necessary. This also
means it is no longer necessary to call iommu_dma_sync_sg_for_device in
iommu_dma_map_sg for untrusted devices.

Fixes: 82612d66d51d ("iommu: Allow the dma-iommu api to use bounce buffers")
Signed-off-by: David Stevens <stevensd@...omium.org>
---
 drivers/iommu/dma-iommu.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index eac65302439e..e79e274d2dc5 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -574,6 +574,9 @@ static dma_addr_t __iommu_dma_map_swiotlb(struct device *dev, phys_addr_t phys,
 		memset(padding_start, 0, padding_size);
 	}
 
+	if (!coherent && !(attrs & DMA_ATTR_SKIP_CPU_SYNC))
+		arch_sync_dma_for_device(phys, org_size, dir);
+
 	iova = __iommu_dma_map(dev, phys, aligned_size, prot, dma_mask);
 	if (iova == DMA_MAPPING_ERROR && is_swiotlb_buffer(phys))
 		swiotlb_tbl_unmap_single(dev, phys, org_size, dir, attrs);
@@ -847,14 +850,9 @@ static dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
 {
 	phys_addr_t phys = page_to_phys(page) + offset;
 	bool coherent = dev_is_dma_coherent(dev);
-	dma_addr_t dma_handle;
 
-	dma_handle = __iommu_dma_map_swiotlb(dev, phys, size, dma_get_mask(dev),
+	return __iommu_dma_map_swiotlb(dev, phys, size, dma_get_mask(dev),
 			coherent, dir, attrs);
-	if (!coherent && !(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
-	    dma_handle != DMA_MAPPING_ERROR)
-		arch_sync_dma_for_device(phys, size, dir);
-	return dma_handle;
 }
 
 static void iommu_dma_unmap_page(struct device *dev, dma_addr_t dma_handle,
@@ -997,12 +995,12 @@ static int iommu_dma_map_sg(struct device *dev, struct scatterlist *sg,
 	    iommu_deferred_attach(dev, domain))
 		return 0;
 
-	if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
-		iommu_dma_sync_sg_for_device(dev, sg, nents, dir);
-
 	if (dev_is_untrusted(dev))
 		return iommu_dma_map_sg_swiotlb(dev, sg, nents, dir, attrs);
 
+	if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
+		iommu_dma_sync_sg_for_device(dev, sg, nents, dir);
+
 	/*
 	 * Work out how much IOVA space we need, and align the segments to
 	 * IOVA granules for the IOMMU driver to handle. With some clever
-- 
2.32.0.93.g670b81a890-goog