On Wed, Jan 21, 2026 at 11:41:48AM +0100, Christian König wrote:

On 1/20/26 21:44, Matthew Brost wrote:

...

On Tue, Jan 20, 2026 at 04:07:06PM +0200, Leon Romanovsky wrote:

...

From: Leon Romanovsky leonro@nvidia.com

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 leonro@nvidia.com

---

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?

Oh, I missed that! And no that is not correct.

This should be DMA_RESV_USAGE_BOOKKEEP so that we wait for everything.

Will change.

Regards, Christian.

...

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