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
Signed-off-by: Christian König <christian.koenig@xxxxxxx>
---
drivers/dma-buf/dma-buf.c | 43 +++++++++++++++++++++++++++++++++++++++++++
include/linux/dma-buf.h | 28 ++++++++++++++++++++++++++++
2 files changed, 71 insertions(+)
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index d2e8ca0d9427..ffaa2f9a9c2c 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -566,6 +566,7 @@ struct dma_buf_attachment *dma_buf_attach(const struct dma_buf_attach_info *info
attach->dev = info->dev;
attach->dmabuf = dmabuf;
attach->priv = info->priv;
+ attach->invalidate = info->invalidate;
mutex_lock(&dmabuf->lock);
@@ -574,7 +575,9 @@ 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);
return attach;
@@ -600,7 +603,9 @@ void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
return;
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);
@@ -634,10 +639,23 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
if (WARN_ON(!attach || !attach->dmabuf))
return ERR_PTR(-EINVAL);
+ /*
+ * 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) {
+ reservation_object_assert_held(attach->dmabuf->resv);
+ list_del(&attach->node);
+ }
+
sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
if (!sg_table)
sg_table = ERR_PTR(-ENOMEM);
+ if (attach->invalidate)
+ list_add(&attach->node, &attach->dmabuf->attachments);
+
return sg_table;
}
EXPORT_SYMBOL_GPL(dma_buf_map_attachment);
@@ -658,6 +676,9 @@ void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
{
might_sleep();
+ if (attach->invalidate)
+ reservation_object_assert_held(attach->dmabuf->resv);
+
if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
return;
@@ -666,6 +687,26 @@ 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
*
@@ -1123,10 +1164,12 @@ 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 2c27568d44af..15dd8598bff1 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -270,6 +270,8 @@ struct dma_buf_ops {
* @poll: for userspace poll support
* @cb_excl: for userspace poll support
* @cb_shared: for userspace poll support
+ * @invalidation_supported: True when the exporter supports unpinned operation
+ * using the reservation lock.
*
* This represents a shared buffer, created by calling dma_buf_export(). The
* userspace representation is a normal file descriptor, which can be created by
@@ -293,6 +295,7 @@ struct dma_buf {
struct list_head list_node;
void *priv;
struct reservation_object *resv;
+ bool invalidation_supported;
/* poll support */
wait_queue_head_t poll;
@@ -326,6 +329,28 @@ struct dma_buf_attachment {
struct device *dev;
struct list_head node;
void *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);
};
/**
@@ -367,6 +392,7 @@ struct dma_buf_export_info {
* @dmabuf: the exported dma_buf
* @dev: the device which wants to import the attachment
* @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.
@@ -375,6 +401,7 @@ struct dma_buf_attach_info {
struct dma_buf *dmabuf;
struct device *dev;
void *priv;
+ void (*invalidate)(struct dma_buf_attachment *attach);
};
/**
@@ -406,6 +433,7 @@ struct sg_table *dma_buf_map_attachment(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,
--
2.14.1
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