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 <[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?
Oh, I missed that! And no that is not correct. This should be DMA_RESV_USAGE_BOOKKEEP so that we wait for everything. 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 >>
