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([2a02:908:1252:fb60:be8a:bd56:1f94:86e7]) by smtp.gmail.com with ESMTPSA id s8sm25807970wru.38.2020.04.28.08.14.41 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Tue, 28 Apr 2020 08:14:42 -0700 (PDT) Reply-To: christian.koenig@amd.com Subject: Re: [RFC 02/17] drm: amdgpu: fix sg_table nents vs. orig_nents misuse 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: Daniel Vetter , Bartlomiej Zolnierkiewicz , David Airlie , intel-gfx@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, Christoph Hellwig , Benjamin Gaignard , Robin Murphy , Sumit Semwal , linux-arm-kernel@lists.infradead.org References: <20200428132005.21424-1-m.szyprowski@samsung.com> <20200428132005.21424-3-m.szyprowski@samsung.com> From: =?UTF-8?Q?Christian_K=c3=b6nig?= Message-ID: Date: Tue, 28 Apr 2020 17:14:40 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20200428132005.21424-3-m.szyprowski@samsung.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 28.04.20 um 15:19 schrieb Marek Szyprowski: > The Documentation/DMA-API-HOWTO.txt states that dma_map_sg returns the > numer of the created entries in the DMA address space. However the > subsequent calls to dma_sync_sg_for_{device,cpu} and dma_unmap_sg must be > called with the original number of entries passed to dma_map_sg. The > sg_table->nents in turn holds the result of the dma_map_sg call as stated > in include/linux/scatterlist.h. Adapt the code to obey those rules. > > Signed-off-by: Marek Szyprowski Reviewed-by: Christian König > --- > drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c | 7 ++++--- > drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 8 ++++---- > 2 files changed, 8 insertions(+), 7 deletions(-) > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c > index 43d8ed7..4df813e 100644 > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c > @@ -307,8 +307,9 @@ static struct sg_table *amdgpu_dma_buf_map(struct dma_buf_attachment *attach, > if (IS_ERR(sgt)) > return sgt; > > - if (!dma_map_sg_attrs(attach->dev, sgt->sgl, sgt->nents, dir, > - DMA_ATTR_SKIP_CPU_SYNC)) > + sgt->nents = dma_map_sg_attrs(attach->dev, sgt->sgl, sgt->orig_nents, > + dir, DMA_ATTR_SKIP_CPU_SYNC); > + if (!sgt->nents) > goto error_free; > break; > > @@ -349,7 +350,7 @@ static void amdgpu_dma_buf_unmap(struct dma_buf_attachment *attach, > struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev); > > if (sgt->sgl->page_link) { > - dma_unmap_sg(attach->dev, sgt->sgl, sgt->nents, dir); > + dma_unmap_sg(attach->dev, sgt->sgl, sgt->orig_nents, dir); > sg_free_table(sgt); > kfree(sgt); > } else { > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c > index d5543c2..5f31585 100644 > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c > @@ -1043,7 +1043,6 @@ static int amdgpu_ttm_tt_pin_userptr(struct ttm_tt *ttm) > { > struct amdgpu_device *adev = amdgpu_ttm_adev(ttm->bdev); > struct amdgpu_ttm_tt *gtt = (void *)ttm; > - unsigned nents; > int r; > > int write = !(gtt->userflags & AMDGPU_GEM_USERPTR_READONLY); > @@ -1059,8 +1058,9 @@ static int amdgpu_ttm_tt_pin_userptr(struct ttm_tt *ttm) > > /* Map SG to device */ > r = -ENOMEM; > - nents = dma_map_sg(adev->dev, ttm->sg->sgl, ttm->sg->nents, direction); > - if (nents == 0) > + ttm->sg->nents = dma_map_sg(adev->dev, ttm->sg->sgl, > + ttm->sg->orig_nents, direction); > + if (ttm->sg->nents == 0) > goto release_sg; > > /* convert SG to linear array of pages and dma addresses */ > @@ -1091,7 +1091,7 @@ static void amdgpu_ttm_tt_unpin_userptr(struct ttm_tt *ttm) > return; > > /* unmap the pages mapped to the device */ > - dma_unmap_sg(adev->dev, ttm->sg->sgl, ttm->sg->nents, direction); > + dma_unmap_sg(adev->dev, ttm->sg->sgl, ttm->sg->orig_nents, direction); > > sg_free_table(ttm->sg); >