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Tue, 12 May 2020 09:01:27 +0000 (GMT) From: Marek Szyprowski 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 , Christoph Hellwig , Robin Murphy , Bartlomiej Zolnierkiewicz , linux-arm-kernel@lists.infradead.org, David Airlie , Daniel Vetter , Matt Porter , Alexandre Bounine Subject: [PATCH v4 35/38] rapidio: fix common struct sg_table related issues Date: Tue, 12 May 2020 11:00:55 +0200 Message-Id: <20200512090058.14910-35-m.szyprowski@samsung.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200512090058.14910-1-m.szyprowski@samsung.com> X-Brightmail-Tracker: H4sIAAAAAAAAA0VSeUgUURzm7ezMjuLauBq+zLKWihTStaIGDCkSnChQAqOErDEnlbzYUcsQ 2tQs1qPUQrPQRbT1Nm93vfJWrK1cC0/UTMFzpVW7PNp1rP77jt/3vvd7PBwR1aM2eGBIOCMN oYPEmCm/pvOn5sgMo/aRKNJxMknTwyO/FA4gZHlGGUpu1qQgZP+KDiMLijp4pKLZhVzun+CR FZOfUVKrfomRJe2jAvLZ++8I2bL0FT0tpIqzigHVuKrgU6rMUQGVOB+HUrWr4yg1ltDFoypz 71HDG5MIlTagBFT9oAyjkqsKAaWv2Otp5m16yo8JCoxkpE6u100DviV0oGFrlneqK9sEMjBI yIEJDonjsHY8F8iBKS4i8gHUlw8JOLIM4POGLIwjegBrtcPgb2SgLQfhDCWAyrxUntHYikwv IUaMEc5QviDHjNiKeABgd5KZESPEIg+26x2M2JK4AOdn07ayfOIg7CuY3CoQEq6wOnYS5crs YNHrN1tnmhj0sew1vrEYEhoBVMm1Am7IDc5qBjEOW8LZrqpt3RZuqrJ5XCAWwAlNiYAjiQBq YzK293GBI5pfhjRuuJ49LFM7cfIZ2PnqPjDKkDCHAwsW3ALmMLUmHeFkIXwUL+KmD8HMrtJ/ tS0f+hAOU/BjU8P2K3YAmDsyJXgC7DL/lykAKATWTAQb7M+wR0OY244sHcxGhPg73ggNrgCG L9W70bVcB9Rrvq2AwIHYTCiRqHxEKB3JRgW3AogjYithXKBBEvrRUXcZaeg1aUQQw7aC3Thf bC08ljNzVUT40+HMLYYJY6R/XR5uYiMDT5eGJLqTM7E7Ljfr3ao9vKxjg/YkF8XnelmWeujm 8nRYvoU3veh7+K2mMbpb53Bp2qbUf5fzi3SvAzNVP+ZOjO+0nc7pAVptjOTTys397Hrnxd8j nXGDqizbqboI+17Ppnf6qr5Gdyt3W6XTuX3rKVdWz8rIx+c3oj0fKumygkAxnw2gnR0QKUv/ AXRmaSZOAwAA X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFprHIsWRmVeSWpSXmKPExsVy+t/xu7ovUnfFGSxs07DoPXeSyeLRqhvM FhtnrGe1+L9tIrPFla/v2SxWrj7KZLFgv7XFlysPmSw2Pb7GanF51xw2i7VH7rJbTD3/ndni 4IcnrA68HmvmrWH02PttAYvHzll32T163rSwemz/9oDV4373cSaPzUvqPW7/e8zsMfnGckaP 3Tcb2Dz6tqxi9Pi8SS6AJ0rPpii/tCRVISO/uMRWKdrQwkjP0NJCz8jEUs/Q2DzWyshUSd/O JiU1J7MstUjfLkEv41P3UdaCP8IVWzcfZm9gvCnQxcjJISFgInHj8CLmLkYuDiGBpYwSy74s ZIRIyEicnNbACmELS/y51sUGUfSJUWLh7WVMIAk2AUOJrrcQCRGBTkaJad0f2UEcZoFvTBKT lt5iA6kSFvCRePNqMlgHi4CqxKWVj8FW8ArYSWxtfgy1Ql5i9YYDzCA2J1D8/vw/LCC2kECh xKOrb1kmMPItYGRYxSiSWlqcm55bbKhXnJhbXJqXrpecn7uJERg324793LyD8dLG4EOMAhyM Sjy8HUY744RYE8uKK3MPMUpwMCuJ8LZkAoV4UxIrq1KL8uOLSnNSiw8xmgIdNZFZSjQ5HxjT eSXxhqaG5haWhubG5sZmFkrivB0CB2OEBNITS1KzU1MLUotg+pg4OKUaGCuqJl6ZsD4idLut 8wIfm538E1b6vdabIryozena/8pd/m2ro6Zrf7m15+yW5wcnulnaNc16lP3twQq3ph+Jb4S+ +cz2XmzZcCLTYdq96PPqAX9/nLdf96Pn8fc/Qnk65d+eTDao2ODA1By069mxHTK7ywJUPzdV dWR+OFUkwl992uzzkbn/5W8psRRnJBpqMRcVJwIAQ0ag5LECAAA= X-CMS-MailID: 20200512090128eucas1p11ee8a5e72ca37dc6b3e8a07ea094bab6 X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-RootMTR: 20200512090128eucas1p11ee8a5e72ca37dc6b3e8a07ea094bab6 X-EPHeader: CA CMS-TYPE: 201P X-CMS-RootMailID: 20200512090128eucas1p11ee8a5e72ca37dc6b3e8a07ea094bab6 References: <20200512085710.14688-1-m.szyprowski@samsung.com> <20200512090058.14910-1-m.szyprowski@samsung.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. To avoid such issues, lets use a common dma-mapping wrappers operating directly on the struct sg_table objects and use scatterlist page iterators where possible. This, almost always, hides references to the nents and orig_nents entries, making the code robust, easier to follow and copy/paste safe. Signed-off-by: Marek Szyprowski --- For more information, see '[PATCH v4 00/38] DRM: fix struct sg_table nents vs. orig_nents misuse' thread: https://lore.kernel.org/dri-devel/20200512085710.14688-1-m.szyprowski@samsung.com/T/ --- drivers/rapidio/devices/rio_mport_cdev.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/drivers/rapidio/devices/rio_mport_cdev.c b/drivers/rapidio/devices/rio_mport_cdev.c index 4029637..df7dba8 100644 --- a/drivers/rapidio/devices/rio_mport_cdev.c +++ b/drivers/rapidio/devices/rio_mport_cdev.c @@ -574,8 +574,7 @@ static void dma_req_free(struct kref *ref) struct mport_cdev_priv *priv = req->priv; unsigned int i; - dma_unmap_sg(req->dmach->device->dev, - req->sgt.sgl, req->sgt.nents, req->dir); + dma_unmap_sgtable(req->dmach->device->dev, req->sgt, req->dir); sg_free_table(&req->sgt); if (req->page_list) { for (i = 0; i < req->nr_pages; i++) @@ -927,9 +926,8 @@ static int do_dma_request(struct mport_dma_req *req, xfer->offset, xfer->length); } - nents = dma_map_sg(chan->device->dev, - req->sgt.sgl, req->sgt.nents, dir); - if (nents == 0) { + ret = dma_map_sgtable(chan->device->dev, req->sgt, dir); + if (ret) { rmcd_error("Failed to map SG list"); ret = -EFAULT; goto err_pg; -- 1.9.1