On Tue, Jan 20, 2026 at 12:44:50PM -0800, 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? > > 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.
I believe I documented this in patch 4: https://lore.kernel.org/all/[email protected]/"; Is there anything else that should be added? 1275 /** 1276 * dma_buf_move_notify - notify attachments that DMA-buf is moving 1277 * 1278 * @dmabuf: [in] buffer which is moving 1279 * 1280 * Informs all attachments that they need to destroy and recreate all their 1281 * mappings. If the attachment is dynamic then the dynamic importer is expected 1282 * to invalidate any caches it has of the mapping result and perform a new 1283 * mapping request before allowing HW to do any further DMA. 1284 * 1285 * If the attachment is pinned then this informs the pinned importer that 1286 * the underlying mapping is no longer available. Pinned importers may take 1287 * this is as a permanent revocation so exporters should not trigger it 1288 * lightly. 1289 * 1290 * For legacy pinned importers that cannot support invalidation this is a NOP. 1291 * Drivers can call dma_buf_attach_revocable() to determine if the importer 1292 * supports this. 1293 * 1294 * NOTE: The invalidation triggers asynchronous HW operation and the callers 1295 * need to wait for this operation to complete by calling 1296 * to dma_resv_wait_timeout(). 1297 */ Thanks > > 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 > >
