[v7,04/36] drm: amdgpu: fix common struct sg_table related issues

Message ID 20200619103636.11974-5-m.szyprowski@samsung.com
State Accepted
Commit 39913934e67cab214480cc95a3632696aeb8e71a
Headers show
Series
  • DRM: fix struct sg_table nents vs. orig_nents misuse
Related show

Commit Message

Marek Szyprowski June 19, 2020, 10:36 a.m.
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 <m.szyprowski@samsung.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c  | 6 +++---
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c      | 9 +++------
 drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c | 8 ++++----
 3 files changed, 10 insertions(+), 13 deletions(-)

Comments

Christian König June 22, 2020, 1:27 p.m. | #1
Am 19.06.20 um 12:36 schrieb Marek Szyprowski:
> 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 <m.szyprowski@samsung.com>
> Reviewed-by: Christian König <christian.koenig@amd.com>

Any objection that we pick this one and the radeon up into our branches 
for upstreaming?

That should about clashes with other driver changes.

Thanks,
Christian.

> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c  | 6 +++---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c      | 9 +++------
>   drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c | 8 ++++----
>   3 files changed, 10 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> index 43d8ed7dbd00..519ce4427fce 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> @@ -307,8 +307,8 @@ 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))
> +		if (dma_map_sgtable(attach->dev, sgt, dir,
> +				    DMA_ATTR_SKIP_CPU_SYNC))
>   			goto error_free;
>   		break;
>   
> @@ -349,7 +349,7 @@ 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_sgtable(attach->dev, sgt, dir, 0);
>   		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 5129a996e941..97fb73e5a6ae 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -1025,7 +1025,6 @@ 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);
> @@ -1040,9 +1039,8 @@ static int amdgpu_ttm_tt_pin_userptr(struct ttm_tt *ttm)
>   		goto release_sg;
>   
>   	/* Map SG to device */
> -	r = -ENOMEM;
> -	nents = dma_map_sg(adev->dev, ttm->sg->sgl, ttm->sg->nents, direction);
> -	if (nents == 0)
> +	r = dma_map_sgtable(adev->dev, ttm->sg, direction, 0);
> +	if (r)
>   		goto release_sg;
>   
>   	/* convert SG to linear array of pages and dma addresses */
> @@ -1073,8 +1071,7 @@ 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_sgtable(adev->dev, ttm->sg, direction, 0);
>   	sg_free_table(ttm->sg);
>   
>   #if IS_ENABLED(CONFIG_DRM_AMDGPU_USERPTR)
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
> index d399e5893170..c281aa13f5ec 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
> @@ -477,11 +477,11 @@ int amdgpu_vram_mgr_alloc_sgt(struct amdgpu_device *adev,
>   	if (r)
>   		goto error_free;
>   
> -	for_each_sg((*sgt)->sgl, sg, num_entries, i)
> +	for_each_sgtable_sg((*sgt), sg, i)
>   		sg->length = 0;
>   
>   	node = mem->mm_node;
> -	for_each_sg((*sgt)->sgl, sg, num_entries, i) {
> +	for_each_sgtable_sg((*sgt), sg, i) {
>   		phys_addr_t phys = (node->start << PAGE_SHIFT) +
>   			adev->gmc.aper_base;
>   		size_t size = node->size << PAGE_SHIFT;
> @@ -501,7 +501,7 @@ int amdgpu_vram_mgr_alloc_sgt(struct amdgpu_device *adev,
>   	return 0;
>   
>   error_unmap:
> -	for_each_sg((*sgt)->sgl, sg, num_entries, i) {
> +	for_each_sgtable_sg((*sgt), sg, i) {
>   		if (!sg->length)
>   			continue;
>   
> @@ -532,7 +532,7 @@ void amdgpu_vram_mgr_free_sgt(struct amdgpu_device *adev,
>   	struct scatterlist *sg;
>   	int i;
>   
> -	for_each_sg(sgt->sgl, sg, sgt->nents, i)
> +	for_each_sgtable_sg(sgt, sg, i)
>   		dma_unmap_resource(dev, sg->dma_address,
>   				   sg->length, dir,
>   				   DMA_ATTR_SKIP_CPU_SYNC);
Marek Szyprowski July 7, 2020, 1:06 p.m. | #2
Hi Christian,

On 22.06.2020 15:27, Christian König wrote:
> Am 19.06.20 um 12:36 schrieb Marek Szyprowski:
>> 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 <m.szyprowski@samsung.com>
>> Reviewed-by: Christian König <christian.koenig@amd.com>
>
> Any objection that we pick this one and the radeon up into our 
> branches for upstreaming?
>
> That should about clashes with other driver changes.

I'm fine. This one and radeon doesn't depend on the prime changes, so it 
should merge fine via your tree. I will try to ask for more review of 
the remaining patches and then try merging via drm-misc.

Best regards

Patch

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
index 43d8ed7dbd00..519ce4427fce 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
@@ -307,8 +307,8 @@  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))
+		if (dma_map_sgtable(attach->dev, sgt, dir,
+				    DMA_ATTR_SKIP_CPU_SYNC))
 			goto error_free;
 		break;
 
@@ -349,7 +349,7 @@  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_sgtable(attach->dev, sgt, dir, 0);
 		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 5129a996e941..97fb73e5a6ae 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -1025,7 +1025,6 @@  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);
@@ -1040,9 +1039,8 @@  static int amdgpu_ttm_tt_pin_userptr(struct ttm_tt *ttm)
 		goto release_sg;
 
 	/* Map SG to device */
-	r = -ENOMEM;
-	nents = dma_map_sg(adev->dev, ttm->sg->sgl, ttm->sg->nents, direction);
-	if (nents == 0)
+	r = dma_map_sgtable(adev->dev, ttm->sg, direction, 0);
+	if (r)
 		goto release_sg;
 
 	/* convert SG to linear array of pages and dma addresses */
@@ -1073,8 +1071,7 @@  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_sgtable(adev->dev, ttm->sg, direction, 0);
 	sg_free_table(ttm->sg);
 
 #if IS_ENABLED(CONFIG_DRM_AMDGPU_USERPTR)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
index d399e5893170..c281aa13f5ec 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
@@ -477,11 +477,11 @@  int amdgpu_vram_mgr_alloc_sgt(struct amdgpu_device *adev,
 	if (r)
 		goto error_free;
 
-	for_each_sg((*sgt)->sgl, sg, num_entries, i)
+	for_each_sgtable_sg((*sgt), sg, i)
 		sg->length = 0;
 
 	node = mem->mm_node;
-	for_each_sg((*sgt)->sgl, sg, num_entries, i) {
+	for_each_sgtable_sg((*sgt), sg, i) {
 		phys_addr_t phys = (node->start << PAGE_SHIFT) +
 			adev->gmc.aper_base;
 		size_t size = node->size << PAGE_SHIFT;
@@ -501,7 +501,7 @@  int amdgpu_vram_mgr_alloc_sgt(struct amdgpu_device *adev,
 	return 0;
 
 error_unmap:
-	for_each_sg((*sgt)->sgl, sg, num_entries, i) {
+	for_each_sgtable_sg((*sgt), sg, i) {
 		if (!sg->length)
 			continue;
 
@@ -532,7 +532,7 @@  void amdgpu_vram_mgr_free_sgt(struct amdgpu_device *adev,
 	struct scatterlist *sg;
 	int i;
 
-	for_each_sg(sgt->sgl, sg, sgt->nents, i)
+	for_each_sgtable_sg(sgt, sg, i)
 		dma_unmap_resource(dev, sg->dma_address,
 				   sg->length, dir,
 				   DMA_ATTR_SKIP_CPU_SYNC);