On Tue, Jan 20, 2026 at 04:07:06PM +0200, Leon Romanovsky wrote:
> From: Leon Romanovsky <[email protected]>
>
> dma-buf invalidation is performed asynchronously by hardware, so VFIO must
> wait until all affected objects have been fully invalidated.
>
> Fixes: 5d74781ebc86 ("vfio/pci: Add dma-buf export support for MMIO regions")
> Signed-off-by: Leon Romanovsky <[email protected]>
> ---
> drivers/vfio/pci/vfio_pci_dmabuf.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/vfio/pci/vfio_pci_dmabuf.c
> b/drivers/vfio/pci/vfio_pci_dmabuf.c
> index d4d0f7d08c53..33bc6a1909dd 100644
> --- a/drivers/vfio/pci/vfio_pci_dmabuf.c
> +++ b/drivers/vfio/pci/vfio_pci_dmabuf.c
> @@ -321,6 +321,9 @@ void vfio_pci_dma_buf_move(struct vfio_pci_core_device
> *vdev, bool revoked)
> dma_resv_lock(priv->dmabuf->resv, NULL);
> priv->revoked = revoked;
> dma_buf_move_notify(priv->dmabuf);
> + dma_resv_wait_timeout(priv->dmabuf->resv,
> + DMA_RESV_USAGE_KERNEL, false,
> + MAX_SCHEDULE_TIMEOUT);
Should we explicitly call out in the dma_buf_move_notify() /
invalidate_mappings kernel-doc that KERNEL slots are the mechanism
for communicating asynchronous dma_buf_move_notify /
invalidate_mappings events via fences?
Yes, this is probably implied, but it wouldn’t hurt to state this
explicitly as part of the cross-driver contract.
Here is what we have now:
* - Dynamic importers should set fences for any access that they can't
* disable immediately from their
&dma_buf_attach_ops.invalidate_mappings
* callback.
Matt
> dma_resv_unlock(priv->dmabuf->resv);
> }
> fput(priv->dmabuf->file);
> @@ -342,6 +345,8 @@ void vfio_pci_dma_buf_cleanup(struct vfio_pci_core_device
> *vdev)
> priv->vdev = NULL;
> priv->revoked = true;
> dma_buf_move_notify(priv->dmabuf);
> + dma_resv_wait_timeout(priv->dmabuf->resv, DMA_RESV_USAGE_KERNEL,
> + false, MAX_SCHEDULE_TIMEOUT);
> dma_resv_unlock(priv->dmabuf->resv);
> vfio_device_put_registration(&vdev->vdev);
> fput(priv->dmabuf->file);
>
> --
> 2.52.0
>
