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=ham 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 0F458C433E6 for ; Tue, 1 Sep 2020 18:42:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EC9732078B for ; Tue, 1 Sep 2020 18:42:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730512AbgIASmj (ORCPT ); Tue, 1 Sep 2020 14:42:39 -0400 Received: from foss.arm.com ([217.140.110.172]:48186 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726140AbgIASmi (ORCPT ); Tue, 1 Sep 2020 14:42:38 -0400 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 272A71FB; Tue, 1 Sep 2020 11:42:37 -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 C9B773F71F; Tue, 1 Sep 2020 11:42:34 -0700 (PDT) Subject: Re: [PATCH v9 08/32] drm: i915: 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 Cc: Christoph Hellwig , Bartlomiej Zolnierkiewicz , linux-arm-kernel@lists.infradead.org, David Airlie , Daniel Vetter , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , intel-gfx@lists.freedesktop.org References: <20200826063316.23486-1-m.szyprowski@samsung.com> <20200826063316.23486-9-m.szyprowski@samsung.com> From: Robin Murphy Message-ID: <38960f66-aab6-8615-9187-b85cf628a4fd@arm.com> Date: Tue, 1 Sep 2020 19:42:32 +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: <20200826063316.23486-9-m.szyprowski@samsung.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. > > This driver creatively uses sg_table->orig_nents to store the size of the > allocated scatterlist and ignores the number of the entries returned by > dma_map_sg function. The sg_table->orig_nents is (mis)used to properly > free the (over)allocated scatterlist. > > This patch only introduces the common DMA-mapping wrappers operating > directly on the struct sg_table objects to the dmabuf related functions, > so the other drivers, which might share buffers with i915 could rely on > the properly set nents and orig_nents values. This one looks mechanical enough :) Reviewed-by: Robin Murphy > Signed-off-by: Marek Szyprowski > --- > drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c | 11 +++-------- > drivers/gpu/drm/i915/gem/selftests/mock_dmabuf.c | 7 +++---- > 2 files changed, 6 insertions(+), 12 deletions(-) > > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c > index 2679380159fc..8a988592715b 100644 > --- a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c > +++ b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c > @@ -48,12 +48,9 @@ static struct sg_table *i915_gem_map_dma_buf(struct dma_buf_attachment *attachme > src = sg_next(src); > } > > - if (!dma_map_sg_attrs(attachment->dev, > - st->sgl, st->nents, dir, > - DMA_ATTR_SKIP_CPU_SYNC)) { > - ret = -ENOMEM; > + ret = dma_map_sgtable(attachment->dev, st, dir, DMA_ATTR_SKIP_CPU_SYNC); > + if (ret) > goto err_free_sg; > - } > > return st; > > @@ -73,9 +70,7 @@ static void i915_gem_unmap_dma_buf(struct dma_buf_attachment *attachment, > { > struct drm_i915_gem_object *obj = dma_buf_to_obj(attachment->dmabuf); > > - dma_unmap_sg_attrs(attachment->dev, > - sg->sgl, sg->nents, dir, > - DMA_ATTR_SKIP_CPU_SYNC); > + dma_unmap_sgtable(attachment->dev, sg, dir, DMA_ATTR_SKIP_CPU_SYNC); > sg_free_table(sg); > kfree(sg); > > diff --git a/drivers/gpu/drm/i915/gem/selftests/mock_dmabuf.c b/drivers/gpu/drm/i915/gem/selftests/mock_dmabuf.c > index debaf7b18ab5..be30b27e2926 100644 > --- a/drivers/gpu/drm/i915/gem/selftests/mock_dmabuf.c > +++ b/drivers/gpu/drm/i915/gem/selftests/mock_dmabuf.c > @@ -28,10 +28,9 @@ static struct sg_table *mock_map_dma_buf(struct dma_buf_attachment *attachment, > sg = sg_next(sg); > } > > - if (!dma_map_sg(attachment->dev, st->sgl, st->nents, dir)) { > - err = -ENOMEM; > + err = dma_map_sgtable(attachment->dev, st, dir, 0); > + if (err) > goto err_st; > - } > > return st; > > @@ -46,7 +45,7 @@ static void mock_unmap_dma_buf(struct dma_buf_attachment *attachment, > struct sg_table *st, > enum dma_data_direction dir) > { > - dma_unmap_sg(attachment->dev, st->sgl, st->nents, dir); > + dma_unmap_sgtable(attachment->dev, st, dir, 0); > sg_free_table(st); > kfree(st); > } >