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 leonro@nvidia.com

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 leonro@nvidia.com

---

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/20260120-dmabuf-revoke-v3-4-b7e0b07b8214@nvidia...." 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