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@xxxxxxx>
> ---
> 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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--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
