[PATCH v7 17/19] vfio/pci: Hand out the P2PDMA provider behind a dma-buf

[Leon Romanovsky]

From: Leon Romanovsky <leonro@xxxxxxxxxx>

An importer attached to a VFIO dma-buf cannot tell whether its peer-to-peer
traffic would reach the exported BAR directly, because the
&struct p2pdma_provider describing it stays in vfio_pci_dma_buf.

Implement @p2pdma_provider so dma_buf_p2pdma_map_type() can reach it.
Refuse once the buffer is revoked: vfio_pci_dma_buf_cleanup() revokes
before it drops the device registration that keeps the provider allocated,
so a revoked buffer has nothing left to describe.

Tested-by: Tushar Dave <tdave@xxxxxxxxxx>
Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxx>
---
 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 c16f460c01d6..fcf392cfc3c5 100644
--- a/drivers/vfio/pci/vfio_pci_dmabuf.c
+++ b/drivers/vfio/pci/vfio_pci_dmabuf.c
@@ -99,11 +99,23 @@ static void vfio_pci_dma_buf_release(struct dma_buf *dmabuf)
 	kfree(priv);
 }
 
+static struct p2pdma_provider *
+vfio_pci_dma_buf_provider(struct dma_buf *dmabuf)
+{
+	struct vfio_pci_dma_buf *priv = dmabuf->priv;
+
+	if (priv->revoked)
+		return NULL;
+
+	return priv->provider;
+}
+
 static const struct dma_buf_ops vfio_pci_dmabuf_ops = {
 	.attach = vfio_pci_dma_buf_attach,
 	.map_dma_buf = vfio_pci_dma_buf_map,
 	.unmap_dma_buf = vfio_pci_dma_buf_unmap,
 	.release = vfio_pci_dma_buf_release,
+	.p2pdma_provider = vfio_pci_dma_buf_provider,
 };
 
 /*

-- 
2.55.0