Re: [RFC PATCH 1/4] dma-buf: heaps: restricted_heap: add no_map attribute

On Fri, Aug 30, 2024 at 10:47 AM Christian König christian.koenig@amd.com wrote:

Am 30.08.24 um 09:03 schrieb Jens Wiklander:

...

Add a no_map attribute to struct restricted_heap_attachment and struct restricted_heap to skip the call to dma_map_sgtable() if set. This avoids trying to map a dma-buf that doens't refer to memory accessible by the kernel.

You seem to have a misunderstanding here dma_map_sgtable() is called to map a table into IOMMU and not any kernel address space.

So please explain why you need that?

You're right, I had misunderstood dma_map_sgtable(). There's no need for the no_map attribute, so I'll remove it.

Perhaps you have a suggestion on how to fix a problem when using dma_map_sgtable()?

Without it, I'll have to assign a pointer to teedev->dev.dma_mask when using the restricted heap with the OP-TEE driver or there will be a warning in __dma_map_sg_attrs() ending with a failure when trying to register the dma-buf fd. OP-TEE is probed with a platform device, and taking the dma_mask pointer from that device works. Is that a good approach or is there a better way of assigning dma_mask?

Thanks, Jens

Regards, Christian.

...

Signed-off-by: Jens Wiklander jens.wiklander@linaro.org

drivers/dma-buf/heaps/restricted_heap.c | 17 +++++++++++++---- drivers/dma-buf/heaps/restricted_heap.h | 2 ++ 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/dma-buf/heaps/restricted_heap.c b/drivers/dma-buf/heaps/restricted_heap.c index 8bc8a5e3f969..4bf28e3727ca 100644 --- a/drivers/dma-buf/heaps/restricted_heap.c +++ b/drivers/dma-buf/heaps/restricted_heap.c @@ -16,6 +16,7 @@ struct restricted_heap_attachment { struct sg_table *table; struct device *dev;

• bool no_map;
  

  };

  static int

@@ -54,6 +55,8 @@ restricted_heap_memory_free(struct restricted_heap *rheap, struct restricted_buf static int restricted_heap_attach(struct dma_buf *dmabuf, struct dma_buf_attachment *attachment) { struct restricted_buffer *restricted_buf = dmabuf->priv;

• struct dma_heap *heap = restricted_buf->heap;
  

• struct restricted_heap *rheap = dma_heap_get_drvdata(heap);
  struct restricted_heap_attachment *a;
  struct sg_table *table;
  
  

@@ -70,6 +73,7 @@ static int restricted_heap_attach(struct dma_buf *dmabuf, struct dma_buf_attachm sg_dma_mark_restricted(table->sgl); a->table = table; a->dev = attachment->dev;

• a->no_map = rheap->no_map;
  attachment->priv = a;
  
  return 0;
  

@@ -92,9 +96,12 @@ restricted_heap_map_dma_buf(struct dma_buf_attachment *attachment, struct sg_table *table = a->table; int ret;

• ret = dma_map_sgtable(attachment->dev, table, direction, DMA_ATTR_SKIP_CPU_SYNC);
  

• if (ret)
  

•         return ERR_PTR(ret);
  

• if (!a->no_map) {
  

•         ret = dma_map_sgtable(attachment->dev, table, direction,
  

•                               DMA_ATTR_SKIP_CPU_SYNC);
  

•         if (ret)
  

•                 return ERR_PTR(ret);
  

• }
  return table;
  

  }

@@ -106,7 +113,9 @@ restricted_heap_unmap_dma_buf(struct dma_buf_attachment *attachment, struct sg_t

  WARN_ON(a->table != table);

• dma_unmap_sgtable(attachment->dev, table, direction, DMA_ATTR_SKIP_CPU_SYNC);
  

• if (!a->no_map)
  

•         dma_unmap_sgtable(attachment->dev, table, direction,
  

•                           DMA_ATTR_SKIP_CPU_SYNC);
  

  }

  static int

diff --git a/drivers/dma-buf/heaps/restricted_heap.h b/drivers/dma-buf/heaps/restricted_heap.h index 7dec4b8a471b..94cc0842f70d 100644 --- a/drivers/dma-buf/heaps/restricted_heap.h +++ b/drivers/dma-buf/heaps/restricted_heap.h @@ -27,6 +27,8 @@ struct restricted_heap { unsigned long cma_paddr; unsigned long cma_size;

• bool                    no_map;
  

• void                    *priv_data;
  

  };