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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>,
        Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>,
        xen-devel@lists.xenproject.org
Subject: [PATCH v2 15/21] drm: xen: fix sg_table nents vs. orig_nents misuse
Date:   Mon,  4 May 2020 14:53:53 +0200
Message-Id: <20200504125359.5678-15-m.szyprowski@samsung.com>
In-Reply-To: <20200504125359.5678-1-m.szyprowski@samsung.com>
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        <20200504125359.5678-1-m.szyprowski@samsung.com>
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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/xen/xen_drm_front_gem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/xen/xen_drm_front_gem.c b/drivers/gpu/drm/xen/xen_drm_front_gem.c
index f0b85e0..ba4bdc5 100644
--- a/drivers/gpu/drm/xen/xen_drm_front_gem.c
+++ b/drivers/gpu/drm/xen/xen_drm_front_gem.c
@@ -215,7 +215,7 @@ struct drm_gem_object *
 		return ERR_PTR(ret);
 
 	DRM_DEBUG("Imported buffer of size %zu with nents %u\n",
-		  size, sgt->nents);
+		  size, sgt->orig_nents);
 
 	return &xen_obj->base;
 }
-- 
1.9.1