[v7,13/36] drm: msm: fix common struct sg_table related issues

Message ID 20200619103636.11974-14-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 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>

---
 drivers/gpu/drm/msm/msm_gem.c    | 13 +++++--------
 drivers/gpu/drm/msm/msm_gpummu.c | 14 ++++++--------
 drivers/gpu/drm/msm/msm_iommu.c  |  2 +-
 3 files changed, 12 insertions(+), 17 deletions(-)

-- 
2.17.1

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Comments

Rob Clark June 19, 2020, 2:45 p.m. | #1
On Fri, Jun 19, 2020 at 3:37 AM Marek Szyprowski
<m.szyprowski@samsung.com> 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 <m.szyprowski@samsung.com>


Acked-by: Rob Clark <robdclark@gmail.com>


(let me know if you want me to take this one in via msm-next or if the
plan is to take the series via drm-misc)


> ---

>  drivers/gpu/drm/msm/msm_gem.c    | 13 +++++--------

>  drivers/gpu/drm/msm/msm_gpummu.c | 14 ++++++--------

>  drivers/gpu/drm/msm/msm_iommu.c  |  2 +-

>  3 files changed, 12 insertions(+), 17 deletions(-)

>

> diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c

> index 38b0c0e1f83e..e0d5fd36ea8f 100644

> --- a/drivers/gpu/drm/msm/msm_gem.c

> +++ b/drivers/gpu/drm/msm/msm_gem.c

> @@ -53,11 +53,10 @@ static void sync_for_device(struct msm_gem_object *msm_obj)

>         struct device *dev = msm_obj->base.dev->dev;

>

>         if (get_dma_ops(dev) && IS_ENABLED(CONFIG_ARM64)) {

> -               dma_sync_sg_for_device(dev, msm_obj->sgt->sgl,

> -                       msm_obj->sgt->nents, DMA_BIDIRECTIONAL);

> +               dma_sync_sgtable_for_device(dev, msm_obj->sgt,

> +                                           DMA_BIDIRECTIONAL);

>         } else {

> -               dma_map_sg(dev, msm_obj->sgt->sgl,

> -                       msm_obj->sgt->nents, DMA_BIDIRECTIONAL);

> +               dma_map_sgtable(dev, msm_obj->sgt, DMA_BIDIRECTIONAL, 0);

>         }

>  }

>

> @@ -66,11 +65,9 @@ static void sync_for_cpu(struct msm_gem_object *msm_obj)

>         struct device *dev = msm_obj->base.dev->dev;

>

>         if (get_dma_ops(dev) && IS_ENABLED(CONFIG_ARM64)) {

> -               dma_sync_sg_for_cpu(dev, msm_obj->sgt->sgl,

> -                       msm_obj->sgt->nents, DMA_BIDIRECTIONAL);

> +               dma_sync_sgtable_for_cpu(dev, msm_obj->sgt, DMA_BIDIRECTIONAL);

>         } else {

> -               dma_unmap_sg(dev, msm_obj->sgt->sgl,

> -                       msm_obj->sgt->nents, DMA_BIDIRECTIONAL);

> +               dma_unmap_sgtable(dev, msm_obj->sgt, DMA_BIDIRECTIONAL, 0);

>         }

>  }

>

> diff --git a/drivers/gpu/drm/msm/msm_gpummu.c b/drivers/gpu/drm/msm/msm_gpummu.c

> index 310a31b05faa..319f06c28235 100644

> --- a/drivers/gpu/drm/msm/msm_gpummu.c

> +++ b/drivers/gpu/drm/msm/msm_gpummu.c

> @@ -30,21 +30,19 @@ static int msm_gpummu_map(struct msm_mmu *mmu, uint64_t iova,

>  {

>         struct msm_gpummu *gpummu = to_msm_gpummu(mmu);

>         unsigned idx = (iova - GPUMMU_VA_START) / GPUMMU_PAGE_SIZE;

> -       struct scatterlist *sg;

> +       struct sg_dma_page_iter dma_iter;

>         unsigned prot_bits = 0;

> -       unsigned i, j;

>

>         if (prot & IOMMU_WRITE)

>                 prot_bits |= 1;

>         if (prot & IOMMU_READ)

>                 prot_bits |= 2;

>

> -       for_each_sg(sgt->sgl, sg, sgt->nents, i) {

> -               dma_addr_t addr = sg->dma_address;

> -               for (j = 0; j < sg->length / GPUMMU_PAGE_SIZE; j++, idx++) {

> -                       gpummu->table[idx] = addr | prot_bits;

> -                       addr += GPUMMU_PAGE_SIZE;

> -               }

> +       for_each_sgtable_dma_page(sgt, &dma_iter, 0) {

> +               dma_addr_t addr = sg_page_iter_dma_address(&dma_iter);

> +

> +               BUILD_BUG_ON(GPUMMU_PAGE_SIZE != PAGE_SIZE);

> +               gpummu->table[idx++] = addr | prot_bits;

>         }

>

>         /* we can improve by deferring flush for multiple map() */

> diff --git a/drivers/gpu/drm/msm/msm_iommu.c b/drivers/gpu/drm/msm/msm_iommu.c

> index 3a381a9674c9..6c31e65834c6 100644

> --- a/drivers/gpu/drm/msm/msm_iommu.c

> +++ b/drivers/gpu/drm/msm/msm_iommu.c

> @@ -36,7 +36,7 @@ static int msm_iommu_map(struct msm_mmu *mmu, uint64_t iova,

>         struct msm_iommu *iommu = to_msm_iommu(mmu);

>         size_t ret;

>

> -       ret = iommu_map_sg(iommu->domain, iova, sgt->sgl, sgt->nents, prot);

> +       ret = iommu_map_sgtable(iommu->domain, iova, sgt, prot);

>         WARN_ON(!ret);

>

>         return (ret == len) ? 0 : -EINVAL;

> --

> 2.17.1

>

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Patch

diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
index 38b0c0e1f83e..e0d5fd36ea8f 100644
--- a/drivers/gpu/drm/msm/msm_gem.c
+++ b/drivers/gpu/drm/msm/msm_gem.c
@@ -53,11 +53,10 @@  static void sync_for_device(struct msm_gem_object *msm_obj)
 	struct device *dev = msm_obj->base.dev->dev;
 
 	if (get_dma_ops(dev) && IS_ENABLED(CONFIG_ARM64)) {
-		dma_sync_sg_for_device(dev, msm_obj->sgt->sgl,
-			msm_obj->sgt->nents, DMA_BIDIRECTIONAL);
+		dma_sync_sgtable_for_device(dev, msm_obj->sgt,
+					    DMA_BIDIRECTIONAL);
 	} else {
-		dma_map_sg(dev, msm_obj->sgt->sgl,
-			msm_obj->sgt->nents, DMA_BIDIRECTIONAL);
+		dma_map_sgtable(dev, msm_obj->sgt, DMA_BIDIRECTIONAL, 0);
 	}
 }
 
@@ -66,11 +65,9 @@  static void sync_for_cpu(struct msm_gem_object *msm_obj)
 	struct device *dev = msm_obj->base.dev->dev;
 
 	if (get_dma_ops(dev) && IS_ENABLED(CONFIG_ARM64)) {
-		dma_sync_sg_for_cpu(dev, msm_obj->sgt->sgl,
-			msm_obj->sgt->nents, DMA_BIDIRECTIONAL);
+		dma_sync_sgtable_for_cpu(dev, msm_obj->sgt, DMA_BIDIRECTIONAL);
 	} else {
-		dma_unmap_sg(dev, msm_obj->sgt->sgl,
-			msm_obj->sgt->nents, DMA_BIDIRECTIONAL);
+		dma_unmap_sgtable(dev, msm_obj->sgt, DMA_BIDIRECTIONAL, 0);
 	}
 }
 
diff --git a/drivers/gpu/drm/msm/msm_gpummu.c b/drivers/gpu/drm/msm/msm_gpummu.c
index 310a31b05faa..319f06c28235 100644
--- a/drivers/gpu/drm/msm/msm_gpummu.c
+++ b/drivers/gpu/drm/msm/msm_gpummu.c
@@ -30,21 +30,19 @@  static int msm_gpummu_map(struct msm_mmu *mmu, uint64_t iova,
 {
 	struct msm_gpummu *gpummu = to_msm_gpummu(mmu);
 	unsigned idx = (iova - GPUMMU_VA_START) / GPUMMU_PAGE_SIZE;
-	struct scatterlist *sg;
+	struct sg_dma_page_iter dma_iter;
 	unsigned prot_bits = 0;
-	unsigned i, j;
 
 	if (prot & IOMMU_WRITE)
 		prot_bits |= 1;
 	if (prot & IOMMU_READ)
 		prot_bits |= 2;
 
-	for_each_sg(sgt->sgl, sg, sgt->nents, i) {
-		dma_addr_t addr = sg->dma_address;
-		for (j = 0; j < sg->length / GPUMMU_PAGE_SIZE; j++, idx++) {
-			gpummu->table[idx] = addr | prot_bits;
-			addr += GPUMMU_PAGE_SIZE;
-		}
+	for_each_sgtable_dma_page(sgt, &dma_iter, 0) {
+		dma_addr_t addr = sg_page_iter_dma_address(&dma_iter);
+
+		BUILD_BUG_ON(GPUMMU_PAGE_SIZE != PAGE_SIZE);
+		gpummu->table[idx++] = addr | prot_bits;
 	}
 
 	/* we can improve by deferring flush for multiple map() */
diff --git a/drivers/gpu/drm/msm/msm_iommu.c b/drivers/gpu/drm/msm/msm_iommu.c
index 3a381a9674c9..6c31e65834c6 100644
--- a/drivers/gpu/drm/msm/msm_iommu.c
+++ b/drivers/gpu/drm/msm/msm_iommu.c
@@ -36,7 +36,7 @@  static int msm_iommu_map(struct msm_mmu *mmu, uint64_t iova,
 	struct msm_iommu *iommu = to_msm_iommu(mmu);
 	size_t ret;
 
-	ret = iommu_map_sg(iommu->domain, iova, sgt->sgl, sgt->nents, prot);
+	ret = iommu_map_sgtable(iommu->domain, iova, sgt, prot);
 	WARN_ON(!ret);
 
 	return (ret == len) ? 0 : -EINVAL;