linux-kernel - [PATCH v2 4/8] iommu/dma: Support granule > PAGE_SIZE in dma_map

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Date:   Sat, 28 Aug 2021 17:36:38 +0200
From:   Sven Peter <sven@...npeter.dev>
To:     iommu@...ts.linux-foundation.org
Cc:     Sven Peter <sven@...npeter.dev>, Joerg Roedel <joro@...tes.org>,
        Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Arnd Bergmann <arnd@...nel.org>,
        Mohamed Mediouni <mohamed.mediouni@...amail.com>,
        Alexander Graf <graf@...zon.com>,
        Hector Martin <marcan@...can.st>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 4/8] iommu/dma: Support granule > PAGE_SIZE in dma_map_sg

Add support to iommu_dma_map_sg's impedance matching to also align
sg_lists correctly when the IOMMU granule is larger than PAGE_SIZE.

Co-developed-by: Robin Murphy <robin.murphy@....com>
Signed-off-by: Robin Murphy <robin.murphy@....com>
Signed-off-by: Sven Peter <sven@...npeter.dev>
---
 drivers/iommu/dma-iommu.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 64fbd9236820..a091cff5829d 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -932,8 +932,8 @@ static int __finalise_sg(struct device *dev, struct scatterlist *sg, int nents,
 		unsigned int s_length = sg_dma_len(s);
 		unsigned int s_iova_len = s->length;
 
-		s->offset += s_iova_off;
-		s->length = s_length;
+		sg_set_page(s, phys_to_page(sg_phys(s) + s_iova_off), s_length,
+			    s_iova_off & ~PAGE_MASK);
 		sg_dma_address(s) = DMA_MAPPING_ERROR;
 		sg_dma_len(s) = 0;
 
@@ -977,10 +977,11 @@ static void __invalidate_sg(struct scatterlist *sg, int nents)
 	int i;
 
 	for_each_sg(sg, s, nents, i) {
-		if (sg_dma_address(s) != DMA_MAPPING_ERROR)
-			s->offset += sg_dma_address(s);
 		if (sg_dma_len(s))
-			s->length = sg_dma_len(s);
+			sg_set_page(s,
+				    phys_to_page(sg_phys(s) + sg_dma_address(s)),
+				    sg_dma_len(s),
+				    sg_dma_address(s) & ~PAGE_MASK);
 		sg_dma_address(s) = DMA_MAPPING_ERROR;
 		sg_dma_len(s) = 0;
 	}
@@ -1056,15 +1057,16 @@ static int iommu_dma_map_sg(struct device *dev, struct scatterlist *sg,
 	 * stashing the unaligned parts in the as-yet-unused DMA fields.
 	 */
 	for_each_sg(sg, s, nents, i) {
-		size_t s_iova_off = iova_offset(iovad, s->offset);
+		phys_addr_t s_phys = sg_phys(s);
+		size_t s_iova_off = iova_offset(iovad, s_phys);
 		size_t s_length = s->length;
 		size_t pad_len = (mask - iova_len + 1) & mask;
 
 		sg_dma_address(s) = s_iova_off;
 		sg_dma_len(s) = s_length;
-		s->offset -= s_iova_off;
 		s_length = iova_align(iovad, s_length + s_iova_off);
-		s->length = s_length;
+		sg_set_page(s, phys_to_page(s_phys - s_iova_off),
+			    s_length, s->offset & ~s_iova_off);
 
 		/*
 		 * Due to the alignment of our single IOVA allocation, we can
-- 
2.25.1