[PATCH RFC 12/26] vfio/pci: Change the DMA-buf exporter to use mapping_type

Jason Gunthorpe
2026-02-18T00:12:18Z

Simple conversion to add a match_mapping() callback that offers an
exporter SGT mapping type. Later patches will add a physical address
exporter so go straight to adding the match_mapping() function.

The check for attachment->peer2peer is replaced with setting
exporter_requires_p2p=true. VFIO always uses MMIO memory.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
drivers/vfio/pci/vfio_pci_dmabuf.c | 31 +++++++++++++++++++++++++-----
1 file changed, 26 insertions(+), 5 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci_dmabuf.c b/drivers/vfio/pci/vfio_pci_dmabuf.c
index d4d0f7d08c53e2..c7addef5794abf 100644
--- a/drivers/vfio/pci/vfio_pci_dmabuf.c
+++ b/drivers/vfio/pci/vfio_pci_dmabuf.c
@@ -25,9 +25,6 @@ static int vfio_pci_dma_buf_attach(struct dma_buf *dmabuf,
{
struct vfio_pci_dma_buf *priv = dmabuf->priv;

- if (!attachment->peer2peer)
- return -EOPNOTSUPP;
-
if (priv->revoked)
return -ENODEV;

@@ -75,11 +72,35 @@ static void vfio_pci_dma_buf_release(struct dma_buf *dmabuf)
kfree(priv);
}

-static const struct dma_buf_ops vfio_pci_dmabuf_ops = {
- .attach = vfio_pci_dma_buf_attach,
+static const struct dma_buf_mapping_sgt_exp_ops vfio_pci_dma_buf_sgt_ops = {
.map_dma_buf = vfio_pci_dma_buf_map,
.unmap_dma_buf = vfio_pci_dma_buf_unmap,
+};
+
+static int vfio_pci_dma_buf_match_mapping(struct dma_buf_match_args *args)
+{
+ struct vfio_pci_dma_buf *priv = args->dmabuf->priv;
+ struct dma_buf_mapping_match sgt_match[1];
+
+ dma_resv_assert_held(priv->dmabuf->resv);
+
+ /*
+ * Once we pass vfio_pci_dma_buf_cleanup() the dmabuf will never be
+ * usable again.
+ */
+ if (!priv->vdev)
+ return -ENODEV;
+
+ sgt_match[0] = DMA_BUF_EMAPPING_SGT_P2P(&vfio_pci_dma_buf_sgt_ops,
+ priv->vdev->pdev);
+
+ return dma_buf_match_mapping(args, sgt_match, ARRAY_SIZE(sgt_match));
+}
+
+static const struct dma_buf_ops vfio_pci_dmabuf_ops = {
+ .attach = vfio_pci_dma_buf_attach,
.release = vfio_pci_dma_buf_release,
+ .match_mapping = vfio_pci_dma_buf_match_mapping,
};

/*
--
2.43.0