On Wed, Jan 21, 2026 at 12:44:51PM +0200, Leon Romanovsky wrote: > 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 <[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. > >
+1 on DMA_RESV_USAGE_BOOKKEEP, I reasoned we have to wait for all fences after I typed the original response. For example preempt fences GPU drivers are in BOOKKEEP which you'd certainly have to wait on for move notify to called complete. Likewise a user issued unbind or TLB invalidation fence would typically be in BOOKKEEP as well, which again would need to be waited on. Matt > > 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 > > >> > > > >
