[PATCH 1/2] vfio/pci: Set up VFIO barmap before creating a DMABUF

[Matt Evans]

A DMABUF exports access to BAR resources which need to be requested
before the DMABUF is handed out.  Usually the resources are requested
when setting up the barmap when the VFIO device fd is mmap()ed, but
there's no guarantee that's done before a DMABUF is created.

Set up the barmap (and so request resources) in the DMABUF-creation
path.

Fixes: 5d74781ebc86c ("vfio/pci: Add dma-buf export support for MMIO regions")
Signed-off-by: Matt Evans <mattev@xxxxxxxx>
---
 drivers/vfio/pci/vfio_pci_dmabuf.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/vfio/pci/vfio_pci_dmabuf.c b/drivers/vfio/pci/vfio_pci_dmabuf.c
index 4ccaf3531e02..fefe7cf4256b 100644
--- a/drivers/vfio/pci/vfio_pci_dmabuf.c
+++ b/drivers/vfio/pci/vfio_pci_dmabuf.c
@@ -272,6 +272,15 @@ int vfio_pci_core_feature_dma_buf(struct vfio_pci_core_device *vdev, u32 flags,
 		goto err_free_priv;
 	}
 
+	/*
+	 * See comment in vfio_pci_core_mmap(); ensure PCI regions
+	 * were requested before returning DMABUFs that reference
+	 * them.  Barmap setup does this:
+	 */
+	ret = vfio_pci_core_setup_barmap(vdev, get_dma_buf.region_index);
+	if (ret)
+		goto err_free_phys;
+
 	priv->vdev = vdev;
 	priv->nr_ranges = get_dma_buf.nr_ranges;
 	priv->size = length;
-- 
2.47.3