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Subject[PATCH 04/12] dma-buf: add optional invalidate_mappings callback v5
Date
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);
};

/**
@@ -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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