Re: [Linaro-mm-sig] [PATCH 05/12] dma-buf: add explicit buffer pinning

On Tue, Apr 16, 2019 at 2:39 PM Christian König ckoenig.leichtzumerken@gmail.com wrote:

Add optional explicit pinning callbacks instead of implicitly assume the exporter pins the buffer when a mapping is created.

Signed-off-by: Christian König christian.koenig@amd.com

drivers/dma-buf/dma-buf.c | 39 +++++++++++++++++++++++++++++++++++++++ include/linux/dma-buf.h | 37 +++++++++++++++++++++++++++++++------ 2 files changed, 70 insertions(+), 6 deletions(-)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index a3738fab3927..f23ff8355505 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -630,6 +630,41 @@ void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach) } EXPORT_SYMBOL_GPL(dma_buf_detach);

+/**

• • dma_buf_pin - Lock down the DMA-buf
• • @dmabuf: [in] DMA-buf to lock down.
• • Returns:
• • 0 on success, negative error code on failure.
• */

+int dma_buf_pin(struct dma_buf *dmabuf) +{

•   int ret = 0;
  

•   reservation_object_assert_held(dmabuf->resv);
  

•   if (dmabuf->ops->pin)
  

•           ret = dmabuf->ops->pin(dmabuf);
  

•   return ret;
  

+} +EXPORT_SYMBOL_GPL(dma_buf_pin);

+/**

• • dma_buf_unpin - Remove lock from DMA-buf
• • @dmabuf: [in] DMA-buf to unlock.
• */

+void dma_buf_unpin(struct dma_buf *dmabuf) +{

•   reservation_object_assert_held(dmabuf->resv);
  

•   if (dmabuf->ops->unpin)
  

•           dmabuf->ops->unpin(dmabuf);
  

+} +EXPORT_SYMBOL_GPL(dma_buf_unpin);

/**

• dma_buf_map_attachment_locked - Maps the buffer into _device_ address space
• with the reservation lock held. Is a wrapper for map_dma_buf() of the

@@ -666,6 +701,8 @@ dma_buf_map_attachment_locked(struct dma_buf_attachment *attach, */ if (attach->invalidate) list_del(&attach->node);

•   else
  

•           dma_buf_pin(attach->dmabuf);
    sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
    if (attach->invalidate)
            list_add(&attach->node, &attach->dmabuf->attachments);
  

@@ -735,6 +772,8 @@ void dma_buf_unmap_attachment_locked(struct dma_buf_attachment *attach,

    attach->dmabuf->ops->unmap_dma_buf(attach, sg_table,
                                            direction);

•   if (!attach->invalidate)
  

•           dma_buf_unpin(attach->dmabuf);
  

} EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment_locked);

diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index ece4638359a8..a615b74e5894 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -100,14 +100,40 @@ struct dma_buf_ops { */ void (*detach)(struct dma_buf *, struct dma_buf_attachment *);

•   /**
  

•    * @pin_dma_buf:
  

•    *
  

•    * This is called by dma_buf_pin and lets the exporter know that an
  

•    * importer assumes that the DMA-buf can't be invalidated any more.
  

•    *
  

•    * This is called with the dmabuf->resv object locked.
  

•    *
  

•    * This callback is optional.
  

•    *
  

•    * Returns:
  

•    *
  

•    * 0 on success, negative error code on failure.
  

•    */
  

•   int (*pin)(struct dma_buf *);
  

•   /**
  

•    * @unpin_dma_buf:
  

•    *
  

•    * This is called by dma_buf_unpin and lets the exporter know that an
  

•   * importer doesn't need to the DMA-buf to stay were it is any more.
  

This should read: * importer doesn't need the DMA-buf to stay were it is anymore.

•    *
  

•    * This is called with the dmabuf->resv object locked.
  

•    *
  

•    * This callback is optional.
  

•    */
  

•   void (*unpin)(struct dma_buf *);
  

•   /**
     * @map_dma_buf:
     *
     * This is called by dma_buf_map_attachment() and is used to map a
     * shared &dma_buf into device address space, and it is mandatory. It
  

•    * can only be called if @attach has been called successfully. This
  

•    * essentially pins the DMA buffer into place, and it cannot be moved
  

•    * any more
  

•    * can only be called if @attach has been called successfully.
     *
     * This call may sleep, e.g. when the backing storage first needs to be
     * allocated, or moved to a location suitable for all currently attached
  

@@ -148,9 +174,6 @@ struct dma_buf_ops { * * This is called by dma_buf_unmap_attachment() and should unmap and * release the &sg_table allocated in @map_dma_buf, and it is mandatory.

•    * It should also unpin the backing storage if this is the last mapping
  

•    * of the DMA buffer, it the exporter supports backing storage
  

•    * migration.
     *
     * This is always called with the dmabuf->resv object locked when
     * no_sgt_cache is true.
  

@@ -442,6 +465,8 @@ int dma_buf_fd(struct dma_buf *dmabuf, int flags); struct dma_buf *dma_buf_get(int fd); void dma_buf_put(struct dma_buf *dmabuf);

+int dma_buf_pin(struct dma_buf *dmabuf); +void dma_buf_unpin(struct dma_buf *dmabuf); struct sg_table *dma_buf_map_attachment_locked(struct dma_buf_attachment *, enum dma_data_direction); struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *, -- 2.17.1

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