From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.6 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 88B17C433E2 for ; Tue, 1 Sep 2020 19:33:38 +0000 (UTC) Received: from fraxinus.osuosl.org (smtp4.osuosl.org [140.211.166.137]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6258C2087D for ; Tue, 1 Sep 2020 19:33:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6258C2087D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by fraxinus.osuosl.org (Postfix) with ESMTP id 41C9A85BD3; Tue, 1 Sep 2020 19:33:38 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from fraxinus.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Fqva_ip55F9U; Tue, 1 Sep 2020 19:33:37 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by fraxinus.osuosl.org (Postfix) with ESMTP id 769C185082; Tue, 1 Sep 2020 19:33:37 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 5BB99C07FF; Tue, 1 Sep 2020 19:33:37 +0000 (UTC) Received: from silver.osuosl.org (smtp3.osuosl.org [140.211.166.136]) by lists.linuxfoundation.org (Postfix) with ESMTP id A82A0C0051 for ; Tue, 1 Sep 2020 19:33:36 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by silver.osuosl.org (Postfix) with ESMTP id 81A1120425 for ; Tue, 1 Sep 2020 19:33:36 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from silver.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id wZ3-cfdFMwAD for ; Tue, 1 Sep 2020 19:33:33 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by silver.osuosl.org (Postfix) with ESMTP id 3FBA9204FD for ; Tue, 1 Sep 2020 19:33:33 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 67D051FB; Tue, 1 Sep 2020 12:33:32 -0700 (PDT) Received: from [10.57.40.122] (unknown [10.57.40.122]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id ABCE13F71F; Tue, 1 Sep 2020 12:33:30 -0700 (PDT) Subject: Re: [PATCH v9 14/32] drm: omapdrm: fix common struct sg_table related issues To: Marek Szyprowski , dri-devel@lists.freedesktop.org, iommu@lists.linux-foundation.org, linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org References: <20200826063316.23486-1-m.szyprowski@samsung.com> <20200826063316.23486-15-m.szyprowski@samsung.com> From: Robin Murphy Message-ID: <7298cc55-c550-0b41-3f3c-8eebed845848@arm.com> Date: Tue, 1 Sep 2020 20:33:29 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <20200826063316.23486-15-m.szyprowski@samsung.com> Content-Language: en-GB Cc: Bartlomiej Zolnierkiewicz , David Airlie , Tomi Valkeinen , Daniel Vetter , Christoph Hellwig , linux-arm-kernel@lists.infradead.org X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On 2020-08-26 07:32, Marek Szyprowski wrote: > 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 > checks for a buffer contiguity in DMA address space, so it should test > sg_table->nents entry. > > Signed-off-by: Marek Szyprowski > --- > drivers/gpu/drm/omapdrm/omap_gem.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/omapdrm/omap_gem.c b/drivers/gpu/drm/omapdrm/omap_gem.c > index ff0c4b0c3fd0..a7a9a0afe2b6 100644 > --- a/drivers/gpu/drm/omapdrm/omap_gem.c > +++ b/drivers/gpu/drm/omapdrm/omap_gem.c > @@ -48,7 +48,7 @@ struct omap_gem_object { > * OMAP_BO_MEM_DMA_API flag set) > * > * - buffers imported from dmabuf (with the OMAP_BO_MEM_DMABUF flag set) > - * if they are physically contiguous (when sgt->orig_nents == 1) > + * if they are physically contiguous (when sgt->nents == 1) Hmm, if this really does mean *physically* contiguous - i.e. if buffers might be shared between DMA-translatable and non-DMA-translatable devices - then these changes might not be appropriate. If not and it only actually means DMA-contiguous, then it would be good to clarify the comments to that effect. Can anyone familiar with omapdrm clarify what exactly the case is here? I know that IOMMUs might be involved to some degree, and I've skimmed the interconnect chapters of enough OMAP TRMs to be scared by the reference to the tiler aperture in the context below :) Robin. > * > * - buffers mapped through the TILER when dma_addr_cnt is not zero, in > * which case the DMA address points to the TILER aperture > @@ -1279,7 +1279,7 @@ struct drm_gem_object *omap_gem_new_dmabuf(struct drm_device *dev, size_t size, > union omap_gem_size gsize; > > /* Without a DMM only physically contiguous buffers can be supported. */ > - if (sgt->orig_nents != 1 && !priv->has_dmm) > + if (sgt->nents != 1 && !priv->has_dmm) > return ERR_PTR(-EINVAL); > > gsize.bytes = PAGE_ALIGN(size); > @@ -1293,7 +1293,7 @@ struct drm_gem_object *omap_gem_new_dmabuf(struct drm_device *dev, size_t size, > > omap_obj->sgt = sgt; > > - if (sgt->orig_nents == 1) { > + if (sgt->nents == 1) { > omap_obj->dma_addr = sg_dma_address(sgt->sgl); > } else { > /* Create pages list from sgt */ > _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu