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From:   Marek Szyprowski <m.szyprowski@samsung.com>
To:     dri-devel@lists.freedesktop.org, iommu@lists.linux-foundation.org,
        linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org
Cc:     Marek Szyprowski <m.szyprowski@samsung.com>,
        Christoph Hellwig <hch@lst.de>,
        Robin Murphy <robin.murphy@arm.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        linux-arm-kernel@lists.infradead.org,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Rob Clark <robdclark@gmail.com>, Sean Paul <sean@poorly.run>,
        linux-arm-msm@vger.kernel.org, freedreno@lists.freedesktop.org
Subject: [PATCH v2 08/21] drm: msm: fix sg_table nents vs. orig_nents misuse
Date:   Mon,  4 May 2020 14:53:46 +0200
Message-Id: <20200504125359.5678-8-m.szyprowski@samsung.com>
In-Reply-To: <20200504125359.5678-1-m.szyprowski@samsung.com>
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References: <20200504125017.5494-1-m.szyprowski@samsung.com>
        <20200504125359.5678-1-m.szyprowski@samsung.com>
        <CGME20200504125415eucas1p2757f9a71add8c7547bc8f85906468113@eucas1p2.samsung.com>
Sender: linux-kernel-owner@vger.kernel.org
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The Documentation/DMA-API-HOWTO.txt states that dma_map_sg returns the
numer of the created entries in the DMA address space. However the
subsequent calls to dma_sync_sg_for_{device,cpu} and dma_unmap_sg must be
called with the original number of entries passed to dma_map_sg. The
sg_table->nents in turn holds the result of the dma_map_sg call as stated
in include/linux/scatterlist.h. Adapt the code to obey those rules.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
---
For more information, see '[PATCH v2 00/21] DRM: fix struct sg_table nents
vs. orig_nents misuse' thread: https://lkml.org/lkml/2020/5/4/373
---
 drivers/gpu/drm/msm/msm_gem.c   | 8 ++++----
 drivers/gpu/drm/msm/msm_iommu.c | 3 ++-
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
index 5a6a79f..54c3bbb 100644
--- a/drivers/gpu/drm/msm/msm_gem.c
+++ b/drivers/gpu/drm/msm/msm_gem.c
@@ -54,10 +54,10 @@ static void sync_for_device(struct msm_gem_object *msm_obj)
 
 	if (get_dma_ops(dev) && IS_ENABLED(CONFIG_ARM64)) {
 		dma_sync_sg_for_device(dev, msm_obj->sgt->sgl,
-			msm_obj->sgt->nents, DMA_BIDIRECTIONAL);
+			msm_obj->sgt->orig_nents, DMA_BIDIRECTIONAL);
 	} else {
 		dma_map_sg(dev, msm_obj->sgt->sgl,
-			msm_obj->sgt->nents, DMA_BIDIRECTIONAL);
+			msm_obj->sgt->orig_nents, DMA_BIDIRECTIONAL);
 	}
 }
 
@@ -67,10 +67,10 @@ static void sync_for_cpu(struct msm_gem_object *msm_obj)
 
 	if (get_dma_ops(dev) && IS_ENABLED(CONFIG_ARM64)) {
 		dma_sync_sg_for_cpu(dev, msm_obj->sgt->sgl,
-			msm_obj->sgt->nents, DMA_BIDIRECTIONAL);
+			msm_obj->sgt->orig_nents, DMA_BIDIRECTIONAL);
 	} else {
 		dma_unmap_sg(dev, msm_obj->sgt->sgl,
-			msm_obj->sgt->nents, DMA_BIDIRECTIONAL);
+			msm_obj->sgt->orig_nents, DMA_BIDIRECTIONAL);
 	}
 }
 
diff --git a/drivers/gpu/drm/msm/msm_iommu.c b/drivers/gpu/drm/msm/msm_iommu.c
index ad58cfe..b0ca084 100644
--- a/drivers/gpu/drm/msm/msm_iommu.c
+++ b/drivers/gpu/drm/msm/msm_iommu.c
@@ -43,7 +43,8 @@ static int msm_iommu_map(struct msm_mmu *mmu, uint64_t iova,
 	struct msm_iommu *iommu = to_msm_iommu(mmu);
 	size_t ret;
 
-	ret = iommu_map_sg(iommu->domain, iova, sgt->sgl, sgt->nents, prot);
+	ret = iommu_map_sg(iommu->domain, iova, sgt->sgl, sgt->orig_nents,
+			   prot);
 	WARN_ON(!ret);
 
 	return (ret == len) ? 0 : -EINVAL;
-- 
1.9.1