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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: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
	David Airlie <airlied@linux.ie>,
	Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>,
	Daniel Vetter <daniel@ffwll.ch>,
	xen-devel@lists.xenproject.org,
	Robin Murphy <robin.murphy@arm.com>,
	Christoph Hellwig <hch@lst.de>,
	linux-arm-kernel@lists.infradead.org
Subject: [PATCH v5 39/38] drm: xen: fix common struct sg_table related issues
Date: Fri, 22 May 2020 14:56:52 +0200
Message-ID: <20200522125652.18435-1-m.szyprowski@samsung.com> (raw)
In-Reply-To: <20200513132114.6046-1-m.szyprowski@samsung.com>

The Documentation/DMA-API-HOWTO.txt states that the dma_map_sg() function
returns the number of the created entries in the DMA address space.
However the subsequent calls to the dma_sync_sg_for_{device,cpu}() and
dma_unmap_sg must be called with the original number of the entries
passed to the dma_map_sg().

struct sg_table is a common structure used for describing a non-contiguous
memory buffer, used commonly in the DRM and graphics subsystems. It
consists of a scatterlist with memory pages and DMA addresses (sgl entry),
as well as the number of scatterlist entries: CPU pages (orig_nents entry)
and DMA mapped pages (nents entry).

It turned out that it was a common mistake to misuse nents and orig_nents
entries, calling DMA-mapping functions with a wrong number of entries or
ignoring the number of mapped entries returned by the dma_map_sg()
function.

Fix the code to refer to proper nents or orig_nents entries. This driver
reports the number of the pages in the imported scatterlist, so it should
refer to sg_table->orig_nents entry.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
---
For more information, see '[PATCH v5 00/38] DRM: fix struct sg_table nents
vs. orig_nents misuse' thread:
https://lore.kernel.org/linux-iommu/20200513132114.6046-1-m.szyprowski@samsung.com/T/

This patch has been resurrected on Oleksandr Andrushchenko request. The
patch was a part of v2 patchset, but then I've dropped it as it only
fixes the debug output, thus I didn't consider it so critical.
---
 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

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      parent reply index

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20200513132127eucas1p23f6be10bbd627e69e36d2451068b3204@eucas1p2.samsung.com>
2020-05-13 13:21 ` [PATCH v5 00/38] DRM: fix struct sg_table nents vs. orig_nents misuse Marek Szyprowski
     [not found]   ` <CGME20200513133256eucas1p273110d0c8f67e52fc7385acef776efaa@eucas1p2.samsung.com>
2020-05-13 13:32     ` [PATCH v5 01/38] dma-mapping: add generic helpers for mapping sgtable objects Marek Szyprowski
     [not found]       ` <CGME20200513133257eucas1p1613a28a71a6c328c406397f7094534d1@eucas1p1.samsung.com>
2020-05-13 13:32         ` [PATCH v5 02/38] scatterlist: add generic wrappers for iterating over " Marek Szyprowski
     [not found]       ` <CGME20200513133258eucas1p2e8ffb90e5553c12419a5af5261b48f5e@eucas1p2.samsung.com>
2020-05-13 13:32         ` [PATCH v5 03/38] iommu: add generic helper for mapping " Marek Szyprowski
     [not found]       ` <CGME20200513133258eucas1p1eba6e0ced0c749655f028206d5f84b7a@eucas1p1.samsung.com>
2020-05-13 13:32         ` [PATCH v5 04/38] drm: prime: add common helper to check scatterlist contiguity Marek Szyprowski
     [not found]       ` <CGME20200513133259eucas1p273f0e05005b7b1158d884295d35745fd@eucas1p2.samsung.com>
2020-05-13 13:32         ` [PATCH v5 05/38] drm: prime: use sgtable iterators in drm_prime_sg_to_page_addr_arrays() Marek Szyprowski
     [not found]       ` <CGME20200513133300eucas1p2fced04876641789a0f5623e70c910690@eucas1p2.samsung.com>
2020-05-13 13:32         ` [PATCH v5 06/38] drm: core: fix common struct sg_table related issues Marek Szyprowski
     [not found]       ` <CGME20200513133301eucas1p244d094c774ad0efd5ea9125747d5cb1b@eucas1p2.samsung.com>
2020-05-13 13:32         ` [PATCH v5 07/38] drm: amdgpu: " Marek Szyprowski
     [not found]       ` <CGME20200513133301eucas1p28c059d25e488ed5ec10feb8f414a1af2@eucas1p2.samsung.com>
2020-05-13 13:32         ` [PATCH v5 08/38] drm: armada: " Marek Szyprowski
     [not found]       ` <CGME20200513133302eucas1p1edbd033e0137d0c973f82c409d3a4e5d@eucas1p1.samsung.com>
2020-05-13 13:32         ` [PATCH v5 09/38] drm: etnaviv: " Marek Szyprowski
     [not found]       ` <CGME20200513133303eucas1p1e3ede8aa38f730d2be317dff27c03019@eucas1p1.samsung.com>
2020-05-13 13:32         ` [PATCH v5 10/38] drm: exynos: use common helper for a scatterlist contiguity check Marek Szyprowski
     [not found]       ` <CGME20200513133304eucas1p1114334ce7250cf8189553a22080b69f4@eucas1p1.samsung.com>
2020-05-13 13:32         ` [PATCH v5 11/38] drm: exynos: fix common struct sg_table related issues Marek Szyprowski
     [not found]       ` <CGME20200513133304eucas1p2d24ddf9d7d60aad254486010db86e6bc@eucas1p2.samsung.com>
2020-05-13 13:32         ` [PATCH v5 12/38] drm: i915: " Marek Szyprowski
     [not found]       ` <CGME20200513133305eucas1p15187ed8fa1e4af181cafa5c65ddab4cd@eucas1p1.samsung.com>
2020-05-13 13:32         ` [PATCH v5 13/38] drm: lima: " Marek Szyprowski
2020-05-18  1:27           ` Qiang Yu
     [not found]       ` <CGME20200513133306eucas1p1ab15386cc4bbcf09052a8175d3660997@eucas1p1.samsung.com>
2020-05-13 13:32         ` [PATCH v5 14/38] drm: mediatek: use common helper for a scatterlist contiguity check Marek Szyprowski
     [not found]       ` <CGME20200513133307eucas1p1da70ed30775467792f4898ccce829d02@eucas1p1.samsung.com>
2020-05-13 13:32         ` [PATCH v5 15/38] drm: mediatek: use common helper for extracting pages array Marek Szyprowski
     [not found]       ` <CGME20200513133308eucas1p205607f34ec3d6df747e21c9b27204ca3@eucas1p2.samsung.com>
2020-05-13 13:32         ` [PATCH v5 16/38] drm: msm: fix common struct sg_table related issues Marek Szyprowski
     [not found]       ` <CGME20200513133308eucas1p248892466634483dfa3b23f11e4da0e68@eucas1p2.samsung.com>
2020-05-13 13:32         ` [PATCH v5 17/38] drm: omapdrm: use common helper for extracting pages array Marek Szyprowski
     [not found]       ` <CGME20200513133309eucas1p1b5b2505556566570e6fb3433397c6168@eucas1p1.samsung.com>
2020-05-13 13:32         ` [PATCH v5 18/38] drm: omapdrm: fix common struct sg_table related issues Marek Szyprowski
     [not found]       ` <CGME20200513133310eucas1p176c920345e7f05f670e26e330b358d7f@eucas1p1.samsung.com>
2020-05-13 13:32         ` [PATCH v5 19/38] drm: panfrost: " Marek Szyprowski
2020-05-14 13:51           ` Rob Herring
     [not found]       ` <CGME20200513133311eucas1p261d84f947b03e4fc733137048aab55fb@eucas1p2.samsung.com>
2020-05-13 13:32         ` [PATCH v5 20/38] drm: radeon: " Marek Szyprowski
     [not found]       ` <CGME20200513133312eucas1p15e5e3bb3ba8e74b923fdccc7decab375@eucas1p1.samsung.com>
2020-05-13 13:32         ` [PATCH v5 21/38] drm: rockchip: use common helper for a scatterlist contiguity check Marek Szyprowski
     [not found]       ` <CGME20200513133312eucas1p2fc1186c0aeee2367898fc0c146f1ed52@eucas1p2.samsung.com>
2020-05-13 13:32         ` [PATCH v5 22/38] drm: rockchip: fix common struct sg_table related issues Marek Szyprowski
     [not found]       ` <CGME20200513133313eucas1p1fa06e23680b6d983578f598166e64cd0@eucas1p1.samsung.com>
2020-05-13 13:32         ` [PATCH v5 23/38] drm: tegra: " Marek Szyprowski
     [not found]       ` <CGME20200513133314eucas1p1a607b556e32887e7f5ca60eb09a476c6@eucas1p1.samsung.com>
2020-05-13 13:32         ` [PATCH v5 24/38] drm: v3d: " Marek Szyprowski
2020-05-13 21:51           ` Eric Anholt
     [not found]       ` <CGME20200513133314eucas1p2f04e32d65e71c613a2a9aacb29064a7d@eucas1p2.samsung.com>
2020-05-13 13:32         ` [PATCH v5 25/38] drm: virtio: " Marek Szyprowski
2020-05-15 10:12           ` Gerd Hoffmann
     [not found]       ` <CGME20200513133315eucas1p17499a099b78c332b30911345c3963368@eucas1p1.samsung.com>
2020-05-13 13:32         ` [PATCH v5 26/38] drm: vmwgfx: " Marek Szyprowski
     [not found]       ` <CGME20200513133316eucas1p2ad01d27ea4388cb50424bcf112d710ef@eucas1p2.samsung.com>
2020-05-13 13:32         ` [PATCH v5 27/38] xen: gntdev: " Marek Szyprowski
2020-05-18  5:17           ` Jürgen Groß
     [not found]       ` <CGME20200513133317eucas1p25446bcdce5220030c16477e1992385ff@eucas1p2.samsung.com>
2020-05-13 13:32         ` [PATCH v5 28/38] drm: host1x: " Marek Szyprowski
     [not found]       ` <CGME20200513133317eucas1p27aead4025db2da13e5b7c3e14a7cd79d@eucas1p2.samsung.com>
2020-05-13 13:32         ` [PATCH v5 29/38] drm: rcar-du: " Marek Szyprowski
2020-05-13 14:23           ` Laurent Pinchart
     [not found]       ` <CGME20200513133318eucas1p1dd6c1ac6a777874c115070d8b5197f34@eucas1p1.samsung.com>
2020-05-13 13:32         ` [PATCH v5 30/38] dmabuf: " Marek Szyprowski
2020-05-15 10:13           ` Gerd Hoffmann
     [not found]       ` <CGME20200513133319eucas1p2eaae7e606163ec1b211a07a80a52655d@eucas1p2.samsung.com>
2020-05-13 13:32         ` [PATCH v5 31/38] staging: ion: remove dead code Marek Szyprowski
     [not found]       ` <CGME20200513133320eucas1p14cc8a7155b3d9ac2e0e30db2128c1477@eucas1p1.samsung.com>
2020-05-13 13:32         ` [PATCH v5 32/38] staging: ion: fix common struct sg_table related issues Marek Szyprowski
     [not found]       ` <CGME20200513133321eucas1p13acea3aa6219ce5f7076c7677ef9eae3@eucas1p1.samsung.com>
2020-05-13 13:32         ` [PATCH v5 33/38] staging: tegra-vde: " Marek Szyprowski
2020-05-14 20:07           ` Dmitry Osipenko
     [not found]       ` <CGME20200513133322eucas1p19b55463a3926b7c1459034f2b02969f8@eucas1p1.samsung.com>
2020-05-13 13:32         ` [PATCH v5 34/38] misc: fastrpc: " Marek Szyprowski
     [not found]       ` <CGME20200513133323eucas1p1344fe42c8710f0ed84cf3c9fdb5ca515@eucas1p1.samsung.com>
2020-05-13 13:32         ` [PATCH v5 35/38] rapidio: " Marek Szyprowski
     [not found]       ` <CGME20200513133323eucas1p1519f5901d2a4ee85b781fcc36e9601f7@eucas1p1.samsung.com>
2020-05-13 13:32         ` [PATCH v5 36/38] samples: vfio-mdev/mbochs: " Marek Szyprowski
     [not found]       ` <CGME20200513133324eucas1p25dc380046c516ca8f07677ed14f93e63@eucas1p2.samsung.com>
2020-05-13 13:32         ` [PATCH v5 37/38] media: pci: fix common ALSA DMA-mapping related codes Marek Szyprowski
     [not found]       ` <CGME20200513133325eucas1p1c8faf557b23b5d171b7c328eca5f6482@eucas1p1.samsung.com>
2020-05-13 13:32         ` [PATCH v5 38/38] videobuf2: use sgtable-based scatterlist wrappers Marek Szyprowski
2020-05-13 13:47   ` [PATCH v5 00/38] DRM: fix struct sg_table nents vs. orig_nents misuse Christoph Hellwig
2020-05-26  7:01     ` Marek Szyprowski
2020-05-26 11:31       ` Daniel Vetter
     [not found]   ` <CGME20200522125708eucas1p233b80b0741f087a84d47f24b6d91985f@eucas1p2.samsung.com>
2020-05-22 12:56     ` Marek Szyprowski [this message]

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