linux-kernel - [PATCH] dma-direct: Set SG_DMA

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Date: Fri,  3 May 2024 18:37:12 +0000
From: "T.J. Mercier" <tjmercier@...gle.com>
To: tjmercier@...gle.com, Christoph Hellwig <hch@....de>, 
	Marek Szyprowski <m.szyprowski@...sung.com>, Robin Murphy <robin.murphy@....com>
Cc: isaacmanjarres@...gle.com, iommu@...ts.linux.dev, 
	linux-kernel@...r.kernel.org
Subject: [PATCH] dma-direct: Set SG_DMA_SWIOTLB flag for dma-direct

As of commit 861370f49ce4 ("iommu/dma: force bouncing if the size is
not cacheline-aligned") sg_dma_mark_swiotlb is called when
dma_map_sgtable takes the IOMMU path and uses SWIOTLB for some portion
of a scatterlist. It is never set for the direct path, so drivers
cannot always rely on sg_dma_is_swiotlb to return correctly after
calling dma_map_sgtable. Fix this by calling sg_dma_mark_swiotlb in the
direct path like it is in the IOMMU path.

Signed-off-by: T.J. Mercier <tjmercier@...gle.com>
---
 kernel/dma/direct.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 4d543b1e9d57..52f0dcb25ca2 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -12,7 +12,7 @@
 #include <linux/pfn.h>
 #include <linux/vmalloc.h>
 #include <linux/set_memory.h>
-#include <linux/slab.h>
+#include <linux/swiotlb.h>
 #include "direct.h"
 
 /*
@@ -497,6 +497,8 @@ int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
 			goto out_unmap;
 		}
 		sg_dma_len(sg) = sg->length;
+		if (is_swiotlb_buffer(dev, dma_to_phys(dev, sg->dma_address)))
+			sg_dma_mark_swiotlb(sg);
 	}
 
 	return nents;
-- 
2.45.0.rc1.225.g2a3ae87e7f-goog