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 9B138C433E7 for ; Tue, 1 Sep 2020 17:46:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 88D84207D3 for ; Tue, 1 Sep 2020 17:46:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729143AbgIARqq (ORCPT ); Tue, 1 Sep 2020 13:46:46 -0400 Received: from foss.arm.com ([217.140.110.172]:47622 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726102AbgIARqp (ORCPT ); Tue, 1 Sep 2020 13:46:45 -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 679CC1FB; Tue, 1 Sep 2020 10:46:44 -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 6A5AC3F71F; Tue, 1 Sep 2020 10:46:37 -0700 (PDT) Subject: Re: [PATCH v9 03/32] drm: core: 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 , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann References: <20200826063316.23486-1-m.szyprowski@samsung.com> <20200826063316.23486-4-m.szyprowski@samsung.com> From: Robin Murphy Message-ID: Date: Tue, 1 Sep 2020 18:46:33 +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: <20200826063316.23486-4-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. > > 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 > Reviewed-by: Andrzej Hajda > --- > drivers/gpu/drm/drm_cache.c | 2 +- > drivers/gpu/drm/drm_gem_shmem_helper.c | 14 +++++++++----- > drivers/gpu/drm/drm_prime.c | 11 ++++++----- > 3 files changed, 16 insertions(+), 11 deletions(-) > > diff --git a/drivers/gpu/drm/drm_cache.c b/drivers/gpu/drm/drm_cache.c > index 03e01b000f7a..0fe3c496002a 100644 > --- a/drivers/gpu/drm/drm_cache.c > +++ b/drivers/gpu/drm/drm_cache.c > @@ -127,7 +127,7 @@ drm_clflush_sg(struct sg_table *st) > struct sg_page_iter sg_iter; > > mb(); /*CLFLUSH is ordered only by using memory barriers*/ > - for_each_sg_page(st->sgl, &sg_iter, st->nents, 0) > + for_each_sgtable_page(st, &sg_iter, 0) > drm_clflush_page(sg_page_iter_page(&sg_iter)); > mb(); /*Make sure that all cache line entry is flushed*/ > > diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c > index 4b7cfbac4daa..47d8211221f2 100644 > --- a/drivers/gpu/drm/drm_gem_shmem_helper.c > +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c > @@ -126,8 +126,8 @@ void drm_gem_shmem_free_object(struct drm_gem_object *obj) > drm_prime_gem_destroy(obj, shmem->sgt); > } else { > if (shmem->sgt) { > - dma_unmap_sg(obj->dev->dev, shmem->sgt->sgl, > - shmem->sgt->nents, DMA_BIDIRECTIONAL); > + dma_unmap_sgtable(obj->dev->dev, shmem->sgt, > + DMA_BIDIRECTIONAL, 0); > sg_free_table(shmem->sgt); > kfree(shmem->sgt); > } > @@ -424,8 +424,7 @@ void drm_gem_shmem_purge_locked(struct drm_gem_object *obj) > > WARN_ON(!drm_gem_shmem_is_purgeable(shmem)); > > - dma_unmap_sg(obj->dev->dev, shmem->sgt->sgl, > - shmem->sgt->nents, DMA_BIDIRECTIONAL); > + dma_unmap_sgtable(obj->dev->dev, shmem->sgt, DMA_BIDIRECTIONAL, 0); > sg_free_table(shmem->sgt); > kfree(shmem->sgt); > shmem->sgt = NULL; > @@ -697,12 +696,17 @@ struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_object *obj) > goto err_put_pages; > } > /* Map the pages for use by the h/w. */ > - dma_map_sg(obj->dev->dev, sgt->sgl, sgt->nents, DMA_BIDIRECTIONAL); > + ret = dma_map_sgtable(obj->dev->dev, sgt, DMA_BIDIRECTIONAL, 0); > + if (ret) > + goto err_free_sgt; > > shmem->sgt = sgt; > > return sgt; > > +err_free_sgt: > + sg_free_table(sgt); > + kfree(sgt); Should this be a separate patch to add the missing error handling to the existing code first? Otherwise the rest of the mechanical conversion looks straightforward enough, and I'm not the separation-of-concerns police (for this subsystem, at least), so either way, Reviewed-by: Robin Murphy > err_put_pages: > drm_gem_shmem_put_pages(shmem); > return ERR_PTR(ret); > diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c > index 5d181bf60a44..c45b0cc6e31d 100644 > --- a/drivers/gpu/drm/drm_prime.c > +++ b/drivers/gpu/drm/drm_prime.c > @@ -617,6 +617,7 @@ struct sg_table *drm_gem_map_dma_buf(struct dma_buf_attachment *attach, > { > struct drm_gem_object *obj = attach->dmabuf->priv; > struct sg_table *sgt; > + int ret; > > if (WARN_ON(dir == DMA_NONE)) > return ERR_PTR(-EINVAL); > @@ -626,11 +627,12 @@ struct sg_table *drm_gem_map_dma_buf(struct dma_buf_attachment *attach, > else > sgt = obj->dev->driver->gem_prime_get_sg_table(obj); > > - if (!dma_map_sg_attrs(attach->dev, sgt->sgl, sgt->nents, dir, > - DMA_ATTR_SKIP_CPU_SYNC)) { > + ret = dma_map_sgtable(attach->dev, sgt, dir, > + DMA_ATTR_SKIP_CPU_SYNC); > + if (ret) { > sg_free_table(sgt); > kfree(sgt); > - sgt = ERR_PTR(-ENOMEM); > + sgt = ERR_PTR(ret); > } > > return sgt; > @@ -652,8 +654,7 @@ void drm_gem_unmap_dma_buf(struct dma_buf_attachment *attach, > if (!sgt) > return; > > - dma_unmap_sg_attrs(attach->dev, sgt->sgl, sgt->nents, dir, > - DMA_ATTR_SKIP_CPU_SYNC); > + dma_unmap_sgtable(attach->dev, sgt, dir, DMA_ATTR_SKIP_CPU_SYNC); > sg_free_table(sgt); > kfree(sgt); > } >