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SubjectRe: [PATCH 04/12] dma-buf: add optional invalidate_mappings callback v5
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Am 17.04.19 um 21:07 schrieb Daniel Vetter:
> 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@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);
> Just noticed this: Why do we need this? invalidate needs the reservation
> lock, as does map_attachment. It should be impssoble to have someone else
> sneak in here.

I was having problems with self triggered invalidations.

E.g. client A tries to map an attachment, that in turn causes the buffer
to move to a new place and client A is informed about that movement with
an invalidation.

Christian.

> -Daniel
>
>> 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
>>
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel

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