Hi, Christian, On Wed, 2026-01-21 at 10:20 +0100, Christian König wrote: > On 1/20/26 15:07, 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]> > > Reviewed-by: Christian König <[email protected]> > > Please also keep in mind that the while this wait for all fences for > correctness you also need to keep the mapping valid until > dma_buf_unmap_attachment() was called.
I'm wondering shouldn't we require DMA_RESV_USAGE_BOOKKEEP here, as *any* unsignaled fence could indicate access through the map? /Thomas > > In other words you can only redirect the DMA-addresses previously > given out into nirvana (or a dummy memory or similar), but you still > need to avoid re-using them for something else. > > Regards, > Christian. > > > --- > > 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); > > 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); > >
