[PATCH vfio-rc] vfio: Prevent from pinned DMABUF importers to attach to VFIO DMABUF

[Leon Romanovsky]

From: Leon Romanovsky <leonro@xxxxxxxxxx>

Some pinned importers, such as non-ODP RDMA ones, cannot invalidate their
mappings and therefore must be prevented from attaching to this exporter.

Fixes: 5d74781ebc86 ("vfio/pci: Add dma-buf export support for MMIO regions")
Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxx>
---
This is an outcome of this discussion about revoke functionality.
https://lore.kernel.org/all/20260121134712.GZ961572@xxxxxxxx

Thanks
---
 drivers/vfio/pci/vfio_pci_dmabuf.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/vfio/pci/vfio_pci_dmabuf.c b/drivers/vfio/pci/vfio_pci_dmabuf.c
index d4d0f7d08c53..4be4a85005cb 100644
--- a/drivers/vfio/pci/vfio_pci_dmabuf.c
+++ b/drivers/vfio/pci/vfio_pci_dmabuf.c
@@ -20,6 +20,16 @@ struct vfio_pci_dma_buf {
 	u8 revoked : 1;
 };
 
+static int vfio_pci_dma_buf_pin(struct dma_buf_attachment *attachment)
+{
+	return -EOPNOTSUPP;
+}
+
+static void vfio_pci_dma_buf_unpin(struct dma_buf_attachment *attachment)
+{
+	/* Do nothing */
+}
+
 static int vfio_pci_dma_buf_attach(struct dma_buf *dmabuf,
 				   struct dma_buf_attachment *attachment)
 {
@@ -76,6 +86,8 @@ static void vfio_pci_dma_buf_release(struct dma_buf *dmabuf)
 }
 
 static const struct dma_buf_ops vfio_pci_dmabuf_ops = {
+	.pin = vfio_pci_dma_buf_pin,
+	.unpin = vfio_pci_dma_buf_unpin,
 	.attach = vfio_pci_dma_buf_attach,
 	.map_dma_buf = vfio_pci_dma_buf_map,
 	.unmap_dma_buf = vfio_pci_dma_buf_unmap,

---
base-commit: acf44a2361b8d6356b71a970ab016065b5123b0e
change-id: 20260121-vfio-add-pin-2229148da56e

Best regards,
--  
Leon Romanovsky <leonro@xxxxxxxxxx>