[RFC PATCH 05/12] vfio/pci: Support get_pfn() callback for dma-buf

[Xu Yilun]

Implement get_pfn() callback for exported MMIO resources.

Signed-off-by: Xu Yilun <yilun.xu at linux.intel.com>
---
 drivers/vfio/pci/dma_buf.c | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/drivers/vfio/pci/dma_buf.c b/drivers/vfio/pci/dma_buf.c
index 1d5f46744922..ad12cfb85099 100644
--- a/drivers/vfio/pci/dma_buf.c
+++ b/drivers/vfio/pci/dma_buf.c
@@ -33,8 +33,34 @@ static int vfio_pci_dma_buf_pin(struct dma_buf_attachment *attachment)
 static int vfio_pci_dma_buf_get_pfn(struct dma_buf_attachment *attachment,
 				    pgoff_t pgoff, u64 *pfn, int *max_order)
 {
-	/* TODO */
-	return -EOPNOTSUPP;
+	struct vfio_pci_dma_buf *priv = attachment->dmabuf->priv;
+	struct vfio_region_dma_range *dma_ranges = priv->dma_ranges;
+	u64 offset = pgoff << PAGE_SHIFT;
+	int i;
+
+	dma_resv_assert_held(priv->dmabuf->resv);
+
+	if (priv->revoked)
+		return -ENODEV;
+
+	if (offset >= priv->dmabuf->size)
+		return -EINVAL;
+
+	for (i = 0; i < priv->nr_ranges; i++) {
+		if (offset < dma_ranges[i].length)
+			break;
+
+		offset -= dma_ranges[i].length;
+	}
+
+	*pfn = PHYS_PFN(pci_resource_start(priv->vdev->pdev, dma_ranges[i].region_index) +
+			dma_ranges[i].offset + offset);
+
+	/* TODO: large page mapping is yet to be supported */
+	if (max_order)
+		*max_order = 0;
+
+	return 0;
 }
 
 static void vfio_pci_dma_buf_release(struct dma_buf *dmabuf)
-- 
2.25.1