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SubjectRe: [PATCH 04/12] dma-buf: add optional invalidate_mappings callback v5
On Wed, Apr 17, 2019 at 09:13:22PM +0200, Christian König wrote:
> 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.

Uh, that sounds like a bug in ttm or somewhere else in the exporter. If
you evict the bo that you're trying to map, that's bad.

Or maybe it's a framework bug, and we need to track whether an attachment
has a map or not. That would make more sense ...
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

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