linux-kernel - [PATCH] iommu/dma: add missing support for DMA_ATTR_MMIO for dma_iova

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Message-Id: <20251124170955.3884351-1-m.szyprowski@samsung.com>
Date: Mon, 24 Nov 2025 18:09:55 +0100
From: Marek Szyprowski <m.szyprowski@...sung.com>
To: iommu@...ts.linux.dev, linux-kernel@...r.kernel.org
Cc: Marek Szyprowski <m.szyprowski@...sung.com>, Robin Murphy
	<robin.murphy@....com>, Joerg Roedel <joro@...tes.org>, Will Deacon
	<will@...nel.org>, Leon Romanovsky <leon@...nel.org>, Jason Gunthorpe
	<jgg@...pe.ca>
Subject: [PATCH] iommu/dma: add missing support for DMA_ATTR_MMIO for
 dma_iova_unlink()

Commit c288d657dd51 added support for DMA_ATTR_MMIO attribute in the
dma_iova_link() code path, but missed that the CPU cache is being also
touched in the dma_iova_unlink() path. Fix this.

Fixes: c288d657dd51 ("iommu/dma: implement DMA_ATTR_MMIO for dma_iova_link().")
Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
---
 drivers/iommu/dma-iommu.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index e52d19d2e833..c92088855450 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -2008,7 +2008,7 @@ static void iommu_dma_iova_unlink_range_slow(struct device *dev,
 			end - addr, iovad->granule - iova_start_pad);
 
 		if (!dev_is_dma_coherent(dev) &&
-		    !(attrs & DMA_ATTR_SKIP_CPU_SYNC))
+		    !(attrs & (DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_MMIO)))
 			arch_sync_dma_for_cpu(phys, len, dir);
 
 		swiotlb_tbl_unmap_single(dev, phys, len, dir, attrs);
@@ -2032,7 +2032,8 @@ static void __iommu_dma_iova_unlink(struct device *dev,
 	size_t unmapped;
 
 	if ((state->__size & DMA_IOVA_USE_SWIOTLB) ||
-	    (!dev_is_dma_coherent(dev) && !(attrs & DMA_ATTR_SKIP_CPU_SYNC)))
+	    (!dev_is_dma_coherent(dev) &&
+	     !(attrs & (DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_MMIO))))
 		iommu_dma_iova_unlink_range_slow(dev, addr, size, dir, attrs);
 
 	iommu_iotlb_gather_init(&iotlb_gather);
-- 
2.34.1