[v5,13/38] drm: lima: fix common struct sg_table related issues

Message ID 20200513133245.6408-13-m.szyprowski@samsung.com
State Superseded
Headers show
Series
  • DRM: fix struct sg_table nents vs. orig_nents misuse
Related show

Commit Message

Marek Szyprowski May 13, 2020, 1:32 p.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>

---
For more information, see '[PATCH v5 00/38] DRM: fix struct sg_table nents
vs. orig_nents misuse' thread:
https://lore.kernel.org/linux-iommu/20200513132114.6046-1-m.szyprowski@samsung.com/T/
---
 drivers/gpu/drm/lima/lima_gem.c | 11 ++++++++---
 drivers/gpu/drm/lima/lima_vm.c  |  5 ++---
 2 files changed, 10 insertions(+), 6 deletions(-)

-- 
1.9.1

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Comments

Qiang Yu May 18, 2020, 1:27 a.m. | #1
Looks good for me, patch is:
Reviewed-by: Qiang Yu <yuq825@gmail.com>


Regards,
Qiang

On Wed, May 13, 2020 at 9:33 PM 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>

> ---

> For more information, see '[PATCH v5 00/38] DRM: fix struct sg_table nents

> vs. orig_nents misuse' thread:

> https://lore.kernel.org/linux-iommu/20200513132114.6046-1-m.szyprowski@samsung.com/T/

> ---

>  drivers/gpu/drm/lima/lima_gem.c | 11 ++++++++---

>  drivers/gpu/drm/lima/lima_vm.c  |  5 ++---

>  2 files changed, 10 insertions(+), 6 deletions(-)

>

> diff --git a/drivers/gpu/drm/lima/lima_gem.c b/drivers/gpu/drm/lima/lima_gem.c

> index 5404e0d..cda43f6 100644

> --- a/drivers/gpu/drm/lima/lima_gem.c

> +++ b/drivers/gpu/drm/lima/lima_gem.c

> @@ -69,8 +69,7 @@ int lima_heap_alloc(struct lima_bo *bo, struct lima_vm *vm)

>                 return ret;

>

>         if (bo->base.sgt) {

> -               dma_unmap_sg(dev, bo->base.sgt->sgl,

> -                            bo->base.sgt->nents, DMA_BIDIRECTIONAL);

> +               dma_unmap_sgtable(dev, bo->base.sgt, DMA_BIDIRECTIONAL, 0);

>                 sg_free_table(bo->base.sgt);

>         } else {

>                 bo->base.sgt = kmalloc(sizeof(*bo->base.sgt), GFP_KERNEL);

> @@ -80,7 +79,13 @@ int lima_heap_alloc(struct lima_bo *bo, struct lima_vm *vm)

>                 }

>         }

>

> -       dma_map_sg(dev, sgt.sgl, sgt.nents, DMA_BIDIRECTIONAL);

> +       ret = dma_map_sgtable(dev, &sgt, DMA_BIDIRECTIONAL, 0);

> +       if (ret) {

> +               sg_free_table(&sgt);

> +               kfree(bo->base.sgt);

> +               bo->base.sgt = NULL;

> +               return ret;

> +       }

>

>         *bo->base.sgt = sgt;

>

> diff --git a/drivers/gpu/drm/lima/lima_vm.c b/drivers/gpu/drm/lima/lima_vm.c

> index 5b92fb8..2b2739a 100644

> --- a/drivers/gpu/drm/lima/lima_vm.c

> +++ b/drivers/gpu/drm/lima/lima_vm.c

> @@ -124,7 +124,7 @@ int lima_vm_bo_add(struct lima_vm *vm, struct lima_bo *bo, bool create)

>         if (err)

>                 goto err_out1;

>

> -       for_each_sg_dma_page(bo->base.sgt->sgl, &sg_iter, bo->base.sgt->nents, 0) {

> +       for_each_sgtable_dma_page(bo->base.sgt, &sg_iter, 0) {

>                 err = lima_vm_map_page(vm, sg_page_iter_dma_address(&sg_iter),

>                                        bo_va->node.start + offset);

>                 if (err)

> @@ -298,8 +298,7 @@ int lima_vm_map_bo(struct lima_vm *vm, struct lima_bo *bo, int pageoff)

>         mutex_lock(&vm->lock);

>

>         base = bo_va->node.start + (pageoff << PAGE_SHIFT);

> -       for_each_sg_dma_page(bo->base.sgt->sgl, &sg_iter,

> -                            bo->base.sgt->nents, pageoff) {

> +       for_each_sgtable_dma_page(bo->base.sgt, &sg_iter, pageoff) {

>                 err = lima_vm_map_page(vm, sg_page_iter_dma_address(&sg_iter),

>                                        base + offset);

>                 if (err)

> --

> 1.9.1

>

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Patch

diff --git a/drivers/gpu/drm/lima/lima_gem.c b/drivers/gpu/drm/lima/lima_gem.c
index 5404e0d..cda43f6 100644
--- a/drivers/gpu/drm/lima/lima_gem.c
+++ b/drivers/gpu/drm/lima/lima_gem.c
@@ -69,8 +69,7 @@  int lima_heap_alloc(struct lima_bo *bo, struct lima_vm *vm)
 		return ret;
 
 	if (bo->base.sgt) {
-		dma_unmap_sg(dev, bo->base.sgt->sgl,
-			     bo->base.sgt->nents, DMA_BIDIRECTIONAL);
+		dma_unmap_sgtable(dev, bo->base.sgt, DMA_BIDIRECTIONAL, 0);
 		sg_free_table(bo->base.sgt);
 	} else {
 		bo->base.sgt = kmalloc(sizeof(*bo->base.sgt), GFP_KERNEL);
@@ -80,7 +79,13 @@  int lima_heap_alloc(struct lima_bo *bo, struct lima_vm *vm)
 		}
 	}
 
-	dma_map_sg(dev, sgt.sgl, sgt.nents, DMA_BIDIRECTIONAL);
+	ret = dma_map_sgtable(dev, &sgt, DMA_BIDIRECTIONAL, 0);
+	if (ret) {
+		sg_free_table(&sgt);
+		kfree(bo->base.sgt);
+		bo->base.sgt = NULL;
+		return ret;
+	}
 
 	*bo->base.sgt = sgt;
 
diff --git a/drivers/gpu/drm/lima/lima_vm.c b/drivers/gpu/drm/lima/lima_vm.c
index 5b92fb8..2b2739a 100644
--- a/drivers/gpu/drm/lima/lima_vm.c
+++ b/drivers/gpu/drm/lima/lima_vm.c
@@ -124,7 +124,7 @@  int lima_vm_bo_add(struct lima_vm *vm, struct lima_bo *bo, bool create)
 	if (err)
 		goto err_out1;
 
-	for_each_sg_dma_page(bo->base.sgt->sgl, &sg_iter, bo->base.sgt->nents, 0) {
+	for_each_sgtable_dma_page(bo->base.sgt, &sg_iter, 0) {
 		err = lima_vm_map_page(vm, sg_page_iter_dma_address(&sg_iter),
 				       bo_va->node.start + offset);
 		if (err)
@@ -298,8 +298,7 @@  int lima_vm_map_bo(struct lima_vm *vm, struct lima_bo *bo, int pageoff)
 	mutex_lock(&vm->lock);
 
 	base = bo_va->node.start + (pageoff << PAGE_SHIFT);
-	for_each_sg_dma_page(bo->base.sgt->sgl, &sg_iter,
-			     bo->base.sgt->nents, pageoff) {
+	for_each_sgtable_dma_page(bo->base.sgt, &sg_iter, pageoff) {
 		err = lima_vm_map_page(vm, sg_page_iter_dma_address(&sg_iter),
 				       base + offset);
 		if (err)