Re: [Linaro-mm-sig] [PATCH 04/12] dma-buf: add optional invalidate_mappings callback v5

On Tue, Apr 16, 2019 at 08:38:33PM +0200, Christian König wrote:

Each importer can now provide an invalidate_mappings callback.

This allows the exporter to provide the mappings without the need to pin the backing store.

v2: don't try to invalidate mappings when the callback is NULL, lock the reservation obj while using the attachments, add helper to set the callback v3: move flag for invalidation support into the DMA-buf, use new attach_info structure to set the callback v4: use importer_priv field instead of mangling exporter priv. v5: drop invalidation_supported flag

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

drivers/dma-buf/dma-buf.c | 37 +++++++++++++++++++++++++++++++++++++ include/linux/dma-buf.h | 33 +++++++++++++++++++++++++++++++-- 2 files changed, 68 insertions(+), 2 deletions(-)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 83c92bfd964c..a3738fab3927 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -563,6 +563,8 @@ struct dma_buf_attachment *dma_buf_attach(const struct dma_buf_attach_info *info attach->dev = info->dev; attach->dmabuf = dmabuf;

• attach->importer_priv = info->importer_priv;
• attach->invalidate = info->invalidate;

mutex_lock(&dmabuf->lock); @@ -571,7 +573,9 @@ struct dma_buf_attachment *dma_buf_attach(const struct dma_buf_attach_info *info if (ret) goto err_attach; }

• reservation_object_lock(dmabuf->resv, NULL); list_add(&attach->node, &dmabuf->attachments);
• reservation_object_unlock(dmabuf->resv);

mutex_unlock(&dmabuf->lock); @@ -615,7 +619,9 @@ void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach) DMA_BIDIRECTIONAL); mutex_lock(&dmabuf->lock);

• reservation_object_lock(dmabuf->resv, NULL); list_del(&attach->node);
• reservation_object_unlock(dmabuf->resv); if (dmabuf->ops->detach) dmabuf->ops->detach(dmabuf, attach);

@@ -653,7 +659,16 @@ dma_buf_map_attachment_locked(struct dma_buf_attachment *attach, if (attach->sgt) return attach->sgt;

• /*

• * Mapping a DMA-buf can trigger its invalidation, prevent sending this
  

• * event to the caller by temporary removing this attachment from the
  

• * list.
  

• */
  

• if (attach->invalidate)

• list_del(&attach->node);
  

  sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
• if (attach->invalidate)

• list_add(&attach->node, &attach->dmabuf->attachments);
  

  if (!sg_table) sg_table = ERR_PTR(-ENOMEM);

@@ -751,6 +766,26 @@ void dma_buf_unmap_attachment(struct dma_buf_attachment *attach, } EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment); +/**

• • dma_buf_invalidate_mappings - invalidate all mappings of this dma_buf
• • @dmabuf: [in] buffer which mappings should be invalidated
• • Informs all attachmenst that they need to destroy and recreated all their
• • mappings.
• */

+void dma_buf_invalidate_mappings(struct dma_buf *dmabuf) +{

• struct dma_buf_attachment *attach;
• reservation_object_assert_held(dmabuf->resv);
• list_for_each_entry(attach, &dmabuf->attachments, node)

• if (attach->invalidate)
  

• 	attach->invalidate(attach);
  

+} +EXPORT_SYMBOL_GPL(dma_buf_invalidate_mappings);

/**

• DOC: cpu access

@@ -1163,10 +1198,12 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused) seq_puts(s, "\tAttached Devices:\n"); attach_count = 0;

• reservation_object_lock(buf_obj->resv, NULL);
  

  list_for_each_entry(attach_obj, &buf_obj->attachments, node) { seq_printf(s, "\t%s\n", dev_name(attach_obj->dev)); attach_count++; }

• reservation_object_unlock(buf_obj->resv);
  

seq_printf(s, "Total %d devices attached\n\n", attach_count); diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index 7e23758db3a4..ece4638359a8 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -324,6 +324,7 @@ struct dma_buf {

• @dev: device attached to the buffer.
• @node: list of dma_buf_attachment.
• @priv: exporter specific attachment data.

• • @importer_priv: importer specific attachment data.
  • This structure holds the attachment information between the dma_buf buffer
  • and its user device(s). The list contains one attachment struct per device

@@ -340,6 +341,29 @@ struct dma_buf_attachment { struct list_head node; void *priv; struct sg_table *sgt;

• void *importer_priv;
• /**

• * @invalidate:
  

• *
  

• * Optional callback provided by the importer of the dma-buf.
  

• *
  

• * If provided the exporter can avoid pinning the backing store while
  

• * mappings exists.
  

• *
  

• * The function is called with the lock of the reservation object
  

• * associated with the dma_buf held and the mapping function must be
  

• * called with this lock held as well. This makes sure that no mapping
  

• * is created concurrently with an ongoing invalidation.
  

• *
  

• * After the callback all existing mappings are still valid until all
  

• * fences in the dma_bufs reservation object are signaled, but should be
  

• * destroyed by the importer as soon as possible.
  

• *
  

• * New mappings can be created immediately, but can't be used before the
  

• * exclusive fence in the dma_bufs reservation object is signaled.
  

• */
  

• void (*invalidate)(struct dma_buf_attachment *attach);

I would put the long kerneldoc into dma_buf_attach_info (as an inline comment, you can mix the styles). And reference it from here with something like

"Set from &dma_buf_attach_info.invalidate in dma_buf_attach(), see there for more information."

This here feels a bit too much hidden. -Daniel

}; /** @@ -378,8 +402,10 @@ struct dma_buf_export_info { /**

• struct dma_buf_attach_info - holds information needed to attach to a dma_buf

• • @dmabuf: the exported dma_buf
• • @dev: the device which wants to import the attachment

• • @dmabuf: the exported dma_buf
• • @dev: the device which wants to import the attachment
• • @importer_priv: private data of importer to this attachment
• • @invalidate: callback to use for invalidating mappings
  • This structure holds the information required to attach to a buffer. Used
  • with dma_buf_attach() only.

@@ -387,6 +413,8 @@ struct dma_buf_export_info { struct dma_buf_attach_info { struct dma_buf *dmabuf; struct device *dev;

• void *importer_priv;
• void (*invalidate)(struct dma_buf_attachment *attach);

}; /** @@ -423,6 +451,7 @@ void dma_buf_unmap_attachment_locked(struct dma_buf_attachment *, enum dma_data_direction); void dma_buf_unmap_attachment(struct dma_buf_attachment *, struct sg_table *, enum dma_data_direction); +void dma_buf_invalidate_mappings(struct dma_buf *dma_buf); int dma_buf_begin_cpu_access(struct dma_buf *dma_buf, enum dma_data_direction dir); int dma_buf_end_cpu_access(struct dma_buf *dma_buf, -- 2.17.1

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