Add a new vfio_device_ops callback to allow the bus driver to
translate a vma mapping of a vfio device fd to a pfn.  Plumb through
vfio-core.  Implemented for vfio-pci.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Alex Williamson <redacted>
 drivers/vfio/pci/vfio_pci.c |    1 +
 drivers/vfio/vfio.c         |   16 ++++++++++++++++
 include/linux/vfio.h        |    3 +++
 3 files changed, 20 insertions(+)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 415b5109da9b..585895970e9c 100644
+++ b/drivers/vfio/pci/vfio_pci.c

@@ -1756,6 +1756,7 @@ static const struct vfio_device_ops vfio_pci_ops = {
 	.mmap		= vfio_pci_mmap,
 	.request	= vfio_pci_request,
 	.match		= vfio_pci_match,
+	.vma_to_pfn	= vfio_pci_bar_vma_to_pfn,
 };
 
 static int vfio_pci_reflck_attach(struct vfio_pci_device *vdev);

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 3a3e85a0dc3e..c47895539a1a 100644
+++ b/drivers/vfio/vfio.c

@@ -944,6 +944,22 @@ struct vfio_device *vfio_device_get_from_vma(struct vm_area_struct *vma)
 }
 EXPORT_SYMBOL_GPL(vfio_device_get_from_vma);
 
+int vfio_vma_to_pfn(struct vm_area_struct *vma, unsigned long *pfn)
+{
+	struct vfio_device *device;
+
+	if (!vma->vm_file || vma->vm_file->f_op != &vfio_device_fops)
+		return -EINVAL;
+
+	device = vma->vm_file->private_data;