Re: [RFC 02/17] drm: amdgpu: fix sg_table nents vs. orig_nents misuse

Christian König
2020-04-28T15:14:49Z

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 <m.szyprowski@samsung.com>

Reviewed-by: Christian König <christian.koenig@amd.com>

> ---
> 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);
>