Re: [PATCH v6 9/9] vfio/pci: Permanently revoke a DMABUF on request

[Jason Gunthorpe <jgg@nvidia.com>]

On Tue, Sep 22, 2026 at 03:46:37PM +0300, Leon Romanovsky wrote:
> On Tue, Sep 22, 2026 at 09:41:37AM -0300, Jason Gunthorpe wrote:
> > On Mon, Sep 21, 2026 at 04:09:18PM +0200, Christian König wrote:
> > > >> I would avoid that and just re-create the DMA-buf fd from
> > > >> scratch. 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