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The extra overhead is negligible and one way state > > > >> transmissions are usually much easier to handle. > > > > > > > > Yeah, maybe we should have done that. Might be too late now. > > > > > > It's already uAPI? > > > > Yeah, but Matt is making some changes here so maybe new stuff can > > avoid this. I'm not sure. > > Jason, the proposed semantics is not UAPI yet. What I'm talking about is, the revoke/unrevoke flow for a single FD was added from the start. For example vfio_pci_ioctl_reset() does it: + vfio_pci_dma_buf_move(vdev, true); ret = pci_try_reset_function(vdev->pdev); + if (__vfio_pci_memory_enabled(vdev)) + vfio_pci_dma_buf_move(vdev, false); up_write(&vdev->memory_lock); The false restores the exsting dmabuf fds back to normal operation. Matt's version is one that defeates the above false so once revoked it stays revoked forever. Jason