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@xxxxxxx>
---
drivers/dma-buf/dma-buf.c | 51 +++++++++++++++++++++++++++++++++------
include/linux/dma-buf.h | 30 +++++++++++++++++++++--
2 files changed, 71 insertions(+), 10 deletions(-)
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 95bcd2ed795b..1b5cdae68cd6 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -607,7 +607,9 @@ 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);
@@ -651,7 +653,9 @@ 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);
@@ -672,10 +676,7 @@ EXPORT_SYMBOL_GPL(dma_buf_detach);
* Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
* on error. May return -EINTR if it is interrupted by a signal.
*
- * A mapping must be unmapped by using dma_buf_unmap_attachment(). Note that
- * the underlying backing storage is pinned for as long as a mapping exists,
- * therefore users/importers should not hold onto a mapping for undue amounts of
- * time.
+ * A mapping must be unmapped by using dma_buf_unmap_attachment().
*/
struct sg_table *
dma_buf_map_attachment_locked(struct dma_buf_attachment *attach,
@@ -690,11 +691,22 @@ dma_buf_map_attachment_locked(struct dma_buf_attachment *attach,
if (attach->sgt)
return attach->sgt;
- r = dma_buf_pin(attach->dmabuf);
- if (r)
- return ERR_PTR(r);
+ if (attach->invalidate) {
+ /*
+ * Mapping a DMA-buf can trigger its invalidation, prevent
+ * sending this event to the caller by temporary removing
+ * this attachment from the list.
+ */
+ list_del(&attach->node);
+ } else {
+ r = dma_buf_pin(attach->dmabuf);
+ if (r)
+ return ERR_PTR(r);
+ }
sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
+ if (attach->invalidate)
+ list_add(&attach->node, &attach->dmabuf->attachments);
if (!sg_table)
return ERR_PTR(-ENOMEM);
@@ -761,7 +773,8 @@ void dma_buf_unmap_attachment_locked(struct dma_buf_attachment *attach,
attach->dmabuf->ops->unmap_dma_buf(attach, sg_table,
direction);
- dma_buf_unpin(attach->dmabuf);
+ if (!attach->invalidate)
+ dma_buf_unpin(attach->dmabuf);
}
EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment_locked);
@@ -793,6 +806,26 @@ 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
*
@@ -1205,10 +1238,12 @@ 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 f7d6fc049b39..d27e91bbd796 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -334,6 +334,9 @@ 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.
+ * @invalidate: invalidate callback, see &dma_buf_attach_info.invalidate for
+ * more information.
*
* This structure holds the attachment information between the dma_buf buffer
* and its user device(s). The list contains one attachment struct per device
@@ -350,6 +353,8 @@ struct dma_buf_attachment {
struct list_head node;
struct sg_table *sgt;
void *priv;
+ void *importer_priv;
+ void (*invalidate)(struct dma_buf_attachment *attach);
};
/**
@@ -388,15 +393,35 @@ 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: optional callback provided by the importer
*
* This structure holds the information required to attach to a buffer. Used
* with dma_buf_attach() only.
+ *
+ * Only if the invalidate callback is provided the framework can avoid pinning
+ * the backing store while mappings exists.
+ *
+ * This callback 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. After getting an
+ * invalidation callback all mappings should be destroyed by the importer using
+ * the normal dma_buf_unmap_attachment() function 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.
*/
struct dma_buf_attach_info {
struct dma_buf *dmabuf;
struct device *dev;
+ void *importer_priv;
+ void (*invalidate)(struct dma_buf_attachment *attach);
};
/**
@@ -436,6 +461,7 @@ 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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