Am 25.06.19 um 17:07 schrieb Daniel Vetter:
On Tue, Jun 25, 2019 at 4:45 PM Christian König
<ckoenig.leichtzumerken@xxxxxxxxx> wrote:
Am 25.06.19 um 16:35 schrieb Daniel Vetter:
Hi Christian,
On Tue, Jun 25, 2019 at 02:46:49PM +0200, Christian König wrote:
On the exporter side we add optional explicit pinning callbacks. If those
callbacks are implemented the framework no longer caches sg tables and the
map/unmap callbacks are always called with the lock of the reservation object
held.
On the importer side we add an optional invalidate callback. This callback is
used by the exporter to inform the importers that their mappings should be
destroyed as soon as possible.
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
v6: squash together with pin/unpin changes
v7: pin/unpin takes an attachment now
v8: nuke dma_buf_attachment_(map|unmap)_locked,
everything is now handled backward compatible
v9: always cache when export/importer don't agree on dynamic handling
v10: minimal style cleanup
v11: drop automatically re-entry avoidance
v12: rename callback to move_notify
Signed-off-by: Christian König <christian.koenig@xxxxxxx>
---
drivers/dma-buf/dma-buf.c | 179 ++++++++++++++++++++++++++++++++++++--
include/linux/dma-buf.h | 108 +++++++++++++++++++++--
2 files changed, 273 insertions(+), 14 deletions(-)
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 6c15deb5d4ad..216f76109f3f 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -531,6 +531,9 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
return ERR_PTR(-EINVAL);
}
+ if (WARN_ON(exp_info->ops->cache_sgt_mapping && exp_info->ops->pin))
+ return ERR_PTR(-EINVAL);
+
if (!try_module_get(exp_info->owner))
return ERR_PTR(-ENOENT);
@@ -651,10 +654,12 @@ void dma_buf_put(struct dma_buf *dmabuf)
EXPORT_SYMBOL_GPL(dma_buf_put);
/**
- * dma_buf_attach - Add the device to dma_buf's attachments list; optionally,
+ * dma_buf_dynamic_attach - Add the device to dma_buf's attachments list; optionally,
* calls attach() of dma_buf_ops to allow device-specific attach functionality
- * @dmabuf: [in] buffer to attach device to.
- * @dev: [in] device to be attached.
+ * @dmabuf: [in] buffer to attach device to.
+ * @dev: [in] device to be attached.
+ * @importer_ops [in] importer operations for the attachment
+ * @importer_priv [in] importer private pointer for the attachment
*
* Returns struct dma_buf_attachment pointer for this attachment. Attachments
* must be cleaned up by calling dma_buf_detach().
@@ -668,8 +673,10 @@ EXPORT_SYMBOL_GPL(dma_buf_put);
* accessible to @dev, and cannot be moved to a more suitable place. This is
* indicated with the error code -EBUSY.
*/
-struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
- struct device *dev)
+struct dma_buf_attachment *
+dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
+ const struct dma_buf_attach_ops *importer_ops,
+ void *importer_priv)
{
struct dma_buf_attachment *attach;
int ret;
@@ -683,6 +690,8 @@ struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
attach->dev = dev;
attach->dmabuf = dmabuf;
+ attach->importer_ops = importer_ops;
+ attach->importer_priv = importer_priv;
mutex_lock(&dmabuf->lock);
@@ -691,16 +700,72 @@ struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
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);
+ /* When either the importer or the exporter can't handle dynamic
+ * mappings we cache the mapping here to avoid issues with the
+ * reservation object lock.
+ */
+ if (dma_buf_attachment_is_dynamic(attach) !=
+ dma_buf_is_dynamic(dmabuf)) {
+ struct sg_table *sgt;
+
+ if (dma_buf_is_dynamic(attach->dmabuf)) {
+ reservation_object_lock(attach->dmabuf->resv, NULL);
+ ret = dma_buf_pin(attach);
+ if (ret)
+ goto err_unlock;
+ }
+
+ sgt = dmabuf->ops->map_dma_buf(attach, DMA_BIDIRECTIONAL);
+ if (!sgt)
+ sgt = ERR_PTR(-ENOMEM);
+ if (IS_ERR(sgt)) {
+ ret = PTR_ERR(sgt);
+ goto err_unpin;
+ }
+ if (dma_buf_is_dynamic(attach->dmabuf))
+ reservation_object_unlock(attach->dmabuf->resv);
+ attach->sgt = sgt;
+ attach->dir = DMA_BIDIRECTIONAL;
+ }
+
return attach;
err_attach:
kfree(attach);
mutex_unlock(&dmabuf->lock);
return ERR_PTR(ret);
+
+err_unpin:
+ if (dma_buf_is_dynamic(attach->dmabuf))
+ dma_buf_unpin(attach);
+
+err_unlock:
+ if (dma_buf_is_dynamic(attach->dmabuf))
+ reservation_object_unlock(attach->dmabuf->resv);
+
+ dma_buf_detach(dmabuf, attach);
+ return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(dma_buf_dynamic_attach);
+
+/**
+ * dma_buf_attach - Wrapper for dma_buf_dynamic_attach
+ * @dmabuf: [in] buffer to attach device to.
+ * @dev: [in] device to be attached.
+ *
+ * Wrapper to call dma_buf_dynamic_attach() for drivers which still use a static
+ * mapping.
+ */
+struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
+ struct device *dev)
+{
+ return dma_buf_dynamic_attach(dmabuf, dev, NULL, NULL);
}
EXPORT_SYMBOL_GPL(dma_buf_attach);
@@ -717,11 +782,22 @@ void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
if (WARN_ON(!dmabuf || !attach))
return;
- if (attach->sgt)
+ if (attach->sgt) {
+ if (dma_buf_is_dynamic(attach->dmabuf))
+ reservation_object_lock(attach->dmabuf->resv, NULL);
+
dmabuf->ops->unmap_dma_buf(attach, attach->sgt, attach->dir);
+ if (dma_buf_is_dynamic(attach->dmabuf)) {
+ dma_buf_unpin(attach);
+ reservation_object_unlock(attach->dmabuf->resv);
+ }
+ }
+
mutex_lock(&dmabuf->lock);
Time to ditch dmabuf->lock in favour of the reservation obj? We have a
fallback resv_obj in struct dma_buf already, so this is never null, and I
think would clean up the code a bit.
Yeah, thought about that as well. But then decided against it for now.
Key point is that exporters currently doesn't care about dmabuf->lock,
but they do care about the reservation lock.
So we will probably have a bunch of cases where we have to fix up
exporters because they will try to grab the reservation lock as well.
On the other hand we maybe not need a lock at all here if we just can
live with multiple attach/detach callbacks running in parallel.
Well looking through the code I thought that all the places you grab
dmabuf->resv we also grab dmabuf->lock, so seemed fully redundant. But
I didn't check completely.
The difference is that I didn't call attach/detach with the lock held yet.
And we could actually drop locking the reservation object while
manipulating the list of attachments since we no longer use that workaround.
Going to fix that up tomorrow as well,
Christian.
+ reservation_object_lock(dmabuf->resv, NULL);
list_del(&attach->node);
+ reservation_object_unlock(dmabuf->resv);
if (dmabuf->ops->detach)
dmabuf->ops->detach(dmabuf, attach);
@@ -730,6 +806,44 @@ 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
+ *
+ * @attach: [in] attachment which should be pinned
+ *
+ * Returns:
+ * 0 on success, negative error code on failure.
+ */
+int dma_buf_pin(struct dma_buf_attachment *attach)
+{
+ struct dma_buf *dmabuf = attach->dmabuf;
+ int ret = 0;
+
+ reservation_object_assert_held(dmabuf->resv);
+
+ if (dmabuf->ops->pin)
+ ret = dmabuf->ops->pin(attach);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(dma_buf_pin);
+
+/**
+ * dma_buf_unpin - Remove lock from DMA-buf
+ *
+ * @attach: [in] attachment which should be unpinned
+ */
+void dma_buf_unpin(struct dma_buf_attachment *attach)
+{
+ struct dma_buf *dmabuf = attach->dmabuf;
+
+ reservation_object_assert_held(dmabuf->resv);
+
+ if (dmabuf->ops->unpin)
+ dmabuf->ops->unpin(attach);
+}
+EXPORT_SYMBOL_GPL(dma_buf_unpin);
+
/**
* dma_buf_map_attachment - Returns the scatterlist table of the attachment;
* mapped into _device_ address space. Is a wrapper for map_dma_buf() of the
@@ -749,6 +863,7 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
enum dma_data_direction direction)
{
struct sg_table *sg_table;
+ int r;
might_sleep();
@@ -767,10 +882,29 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
return attach->sgt;
}
+ if (dma_buf_attachment_is_dynamic(attach)) {
+ reservation_object_assert_held(attach->dmabuf->resv);
+
+ } else if (dma_buf_is_dynamic(attach->dmabuf)) {
+ reservation_object_lock(attach->dmabuf->resv, NULL);
+ r = dma_buf_pin(attach);
+ if (r) {
+ reservation_object_unlock(attach->dmabuf->resv);
+ return ERR_PTR(r);
+ }
+ }
With this design (because we can't cache at attach time unconditionally)
we inflict the reservation lock on all importers. So needs:
} else {
/* neither importer nor exporter are dynamice */
might_lock(dmabuf->resv->ww_mutex);
}
Same for dma_buf_unmap_attachment.
Good idea.
I also expect that this will blow up in intel-gfx-ci :-/ I did look at
previous intel-gfx-ci runs of your series, and the last one that did pass
was the one that still had the caching in _attach():
Well as far as I can see the current one passes as well. Actually just
recently found a typo because of this.
Hm indeed the amd/i915 prime tests are still in BAT and that passed.
I'm surprised. Maybe Chris Wilson moved along quite a lot with our
locking rework and i915 isn't the bad one out anymore.
Geez I was sooooooooo locking forward to slapping an r-b on this and
volunteering myself to polish the kerneldoc (which isn't great, but also
pre-existing condition plus on my todo list anyway) :-(
Going to add the might_lock and send again, let's see what intel-gfx-ci
has say to this.
Yeah that should at least increase the chances we're seeing something.
Ofc intel-gfx-ci doesn't test everything :-)
-Daniel
Christian.
+
sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
if (!sg_table)
sg_table = ERR_PTR(-ENOMEM);
+ if (!dma_buf_attachment_is_dynamic(attach) &&
+ dma_buf_is_dynamic(attach->dmabuf)) {
+ if (IS_ERR(sg_table))
+ dma_buf_unpin(attach);
+ reservation_object_unlock(attach->dmabuf->resv);
+ }
+
if (!IS_ERR(sg_table) && attach->dmabuf->ops->cache_sgt_mapping) {
attach->sgt = sg_table;
attach->dir = direction;
@@ -802,10 +936,41 @@ void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
if (attach->sgt == sg_table)
return;
+ if (dma_buf_attachment_is_dynamic(attach))
+ reservation_object_assert_held(attach->dmabuf->resv);
+ else if (dma_buf_is_dynamic(attach->dmabuf))
+ reservation_object_lock(attach->dmabuf->resv, NULL);
+
attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, direction);
+
+ if (dma_buf_is_dynamic(attach->dmabuf) &&
+ !dma_buf_attachment_is_dynamic(attach)) {
+ dma_buf_unpin(attach);
+ reservation_object_unlock(attach->dmabuf->resv);
+ }
}
EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment);
+/**
+ * dma_buf_move_notify - notify attachments that DMA-buf is moving
+ *
+ * @dmabuf: [in] buffer which is moving
+ *
+ * Informs all attachmenst that they need to destroy and recreated all their
+ * mappings.
+ */
+void dma_buf_move_notify(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->importer_ops && attach->importer_ops->move_notify)
+ attach->importer_ops->move_notify(attach);
+}
+EXPORT_SYMBOL_GPL(dma_buf_move_notify);
+
/**
* DOC: cpu access
*
@@ -1225,10 +1390,12 @@ 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);
Yeah definitely time to retire dmabuf->lock I think.
Cheers, Daniel
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 01ad5b942a6f..ccad2fc1f640 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -92,14 +92,40 @@ struct dma_buf_ops {
*/
void (*detach)(struct dma_buf *, struct dma_buf_attachment *);
+ /**
+ * @pin:
+ *
+ * This is called by dma_buf_pin and lets the exporter know that the
+ * DMA-buf can't be moved 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_attachment *attach);
+
+ /**
+ * @unpin:
+ *
+ * This is called by dma_buf_unpin and lets the exporter know that the
+ * DMA-buf can be moved again.
+ *
+ * This is called with the dmabuf->resv object locked.
+ *
+ * This callback is optional.
+ */
+ void (*unpin)(struct dma_buf_attachment *attach);
+
/**
* @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
@@ -120,6 +146,9 @@ struct dma_buf_ops {
* any other kind of sharing that the exporter might wish to make
* available to buffer-users.
*
+ * This is always called with the dmabuf->resv object locked when
+ * the pin/unpin callbacks are implemented.
+ *
* Returns:
*
* A &sg_table scatter list of or the backing storage of the DMA buffer,
@@ -137,9 +166,6 @@ 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.
*/
void (*unmap_dma_buf)(struct dma_buf_attachment *,
struct sg_table *,
@@ -330,6 +356,34 @@ struct dma_buf {
} cb_excl, cb_shared;
};
+/**
+ * struct dma_buf_attach_ops - importer operations for an attachment
+ * @move_notify: [optional] notification that the DMA-buf is moving
+ *
+ * Attachment operations implemented by the importer.
+ */
+struct dma_buf_attach_ops {
+ /**
+ * @move_notify
+ *
+ * If this 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 move operation.
+ *
+ * Mappings stay valid and are not directly affected by this callback.
+ * But the DMA-buf can now be in a different physical location, so all
+ * mappings should be destroyed and re-created as soon as possible.
+ *
+ * New mappings can be created after this callback returns, and will
+ * point to the new location of the DMA-buf.
+ */
+ void (*move_notify)(struct dma_buf_attachment *attach);
+};
+
/**
* struct dma_buf_attachment - holds device-buffer attachment data
* @dmabuf: buffer for this attachment.
@@ -338,6 +392,8 @@ struct dma_buf {
* @sgt: cached mapping.
* @dir: direction of cached mapping.
* @priv: exporter specific attachment data.
+ * @importer_ops: importer operations for this attachment.
+ * @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
@@ -355,6 +411,9 @@ struct dma_buf_attachment {
struct sg_table *sgt;
enum dma_data_direction dir;
void *priv;
+
+ const struct dma_buf_attach_ops *importer_ops;
+ void *importer_priv;
};
/**
@@ -405,10 +464,42 @@ static inline void get_dma_buf(struct dma_buf *dmabuf)
get_file(dmabuf->file);
}
+/**
+ * dma_buf_is_dynamic - check if a DMA-buf uses dynamic mappings.
+ * @dmabuf: the DMA-buf to check
+ *
+ * Returns true if a DMA-buf exporter wants to create dynamic sg table mappings
+ * for each attachment. False if only a single static sg table should be used.
+ */
+static inline bool dma_buf_is_dynamic(struct dma_buf *dmabuf)
+{
+ return !!dmabuf->ops->pin;
+}
+
+/**
+ * dma_buf_attachment_is_dynamic - check if a DMA-buf attachment uses dynamic
+ * mappinsg
+ * @attach: the DMA-buf attachment to check
+ *
+ * Returns true if a DMA-buf importer wants to use dynamic sg table mappings and
+ * calls the map/unmap functions with the reservation object locked.
+ */
+static inline bool
+dma_buf_attachment_is_dynamic(struct dma_buf_attachment *attach)
+{
+ return attach->importer_ops && attach->importer_ops->move_notify;
+}
+
struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
- struct device *dev);
+ struct device *dev);
+struct dma_buf_attachment *
+dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
+ const struct dma_buf_attach_ops *importer_ops,
+ void *importer_priv);
void dma_buf_detach(struct dma_buf *dmabuf,
- struct dma_buf_attachment *dmabuf_attach);
+ struct dma_buf_attachment *attach);
+int dma_buf_pin(struct dma_buf_attachment *attach);
+void dma_buf_unpin(struct dma_buf_attachment *attach);
struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info);
@@ -420,6 +511,7 @@ 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_move_notify(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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