[v3,10/25] drm: panfrost: fix common struct sg_table related issues

Message ID 20200505084614.30424-10-m.szyprowski@samsung.com
State New
Headers show
Series
  • DRM: fix struct sg_table nents vs. orig_nents misuse
Related show

Commit Message

Marek Szyprowski May 5, 2020, 8:45 a.m.
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 the 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. A common mistake was to ignore a result
of the dma_map_sg function and don't use the sg_table->orig_nents at all.

To avoid such issues, lets use common dma-mapping wrappers operating
directly on the struct sg_table objects and adjust references to the
nents and orig_nents respectively.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

---
For more information, see '[PATCH v3 00/25] DRM: fix struct sg_table nents
vs. orig_nents misuse' thread: https://lkml.org/lkml/2020/5/5/187
---
 drivers/gpu/drm/panfrost/panfrost_gem.c | 4 ++--
 drivers/gpu/drm/panfrost/panfrost_mmu.c | 5 ++---
 2 files changed, 4 insertions(+), 5 deletions(-)

-- 
1.9.1

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Comments

Steven Price May 11, 2020, 3:51 p.m. | #1
On 05/05/2020 09:45, Marek Szyprowski wrote:
> 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 the 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. A common mistake was to ignore a result

> of the dma_map_sg function and don't use the sg_table->orig_nents at all.

> 

> To avoid such issues, lets use common dma-mapping wrappers operating

> directly on the struct sg_table objects and adjust references to the

> nents and orig_nents respectively.

> 

> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>


The change looks good to me:

Reviewed-by: Steven Price <steven.price@arm.com>


Although I would have appreciated the commit message being modified to 
match the specifics of Panfrost - the return of dma_mpa_sg() wasn't 
being ignored, but the use of orig_nents/nents was indeed wrong.

Steve

> ---

> For more information, see '[PATCH v3 00/25] DRM: fix struct sg_table nents

> vs. orig_nents misuse' thread: https://lkml.org/lkml/2020/5/5/187

> ---

>   drivers/gpu/drm/panfrost/panfrost_gem.c | 4 ++--

>   drivers/gpu/drm/panfrost/panfrost_mmu.c | 5 ++---

>   2 files changed, 4 insertions(+), 5 deletions(-)

> 

> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/panfrost/panfrost_gem.c

> index 17b654e..95d7e80 100644

> --- a/drivers/gpu/drm/panfrost/panfrost_gem.c

> +++ b/drivers/gpu/drm/panfrost/panfrost_gem.c

> @@ -41,8 +41,8 @@ static void panfrost_gem_free_object(struct drm_gem_object *obj)

>   

>   		for (i = 0; i < n_sgt; i++) {

>   			if (bo->sgts[i].sgl) {

> -				dma_unmap_sg(pfdev->dev, bo->sgts[i].sgl,

> -					     bo->sgts[i].nents, DMA_BIDIRECTIONAL);

> +				dma_unmap_sgtable(pfdev->dev, &bo->sgts[i],

> +						  DMA_BIDIRECTIONAL);

>   				sg_free_table(&bo->sgts[i]);

>   			}

>   		}

> diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c

> index ed28aeb..9926111 100644

> --- a/drivers/gpu/drm/panfrost/panfrost_mmu.c

> +++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c

> @@ -517,10 +517,9 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,

>   	if (ret)

>   		goto err_pages;

>   

> -	if (!dma_map_sg(pfdev->dev, sgt->sgl, sgt->nents, DMA_BIDIRECTIONAL)) {

> -		ret = -EINVAL;

> +	ret = dma_map_sgtable(pfdev->dev, sgt, DMA_BIDIRECTIONAL);

> +	if (ret)

>   		goto err_map;

> -	}

>   

>   	mmu_map_sg(pfdev, bomapping->mmu, addr,

>   		   IOMMU_WRITE | IOMMU_READ | IOMMU_NOEXEC, sgt);

> 


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Patch

diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/panfrost/panfrost_gem.c
index 17b654e..95d7e80 100644
--- a/drivers/gpu/drm/panfrost/panfrost_gem.c
+++ b/drivers/gpu/drm/panfrost/panfrost_gem.c
@@ -41,8 +41,8 @@  static void panfrost_gem_free_object(struct drm_gem_object *obj)
 
 		for (i = 0; i < n_sgt; i++) {
 			if (bo->sgts[i].sgl) {
-				dma_unmap_sg(pfdev->dev, bo->sgts[i].sgl,
-					     bo->sgts[i].nents, DMA_BIDIRECTIONAL);
+				dma_unmap_sgtable(pfdev->dev, &bo->sgts[i],
+						  DMA_BIDIRECTIONAL);
 				sg_free_table(&bo->sgts[i]);
 			}
 		}
diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c
index ed28aeb..9926111 100644
--- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
+++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
@@ -517,10 +517,9 @@  static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
 	if (ret)
 		goto err_pages;
 
-	if (!dma_map_sg(pfdev->dev, sgt->sgl, sgt->nents, DMA_BIDIRECTIONAL)) {
-		ret = -EINVAL;
+	ret = dma_map_sgtable(pfdev->dev, sgt, DMA_BIDIRECTIONAL);
+	if (ret)
 		goto err_map;
-	}
 
 	mmu_map_sg(pfdev, bomapping->mmu, addr,
 		   IOMMU_WRITE | IOMMU_READ | IOMMU_NOEXEC, sgt);