[PATCH v2 4/5] vfio/mdev: Uses the vfio emulated iommufd ops set in the mdev sample drivers

[Yi Liu <yi.l.liu@xxxxxxxxx>]

This harmonizes the no-DMA devices (the vfio-mdev sample drivers) with
the emulated devices (gvt-g, vfio-ap etc.). It makes it easier to add
BIND_IOMMUFD user interface which requires to return an iommufd ID to
represent the device/iommufd bond.

Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx>
---
 drivers/vfio/iommufd.c     | 14 ++++++--------
 samples/vfio-mdev/mbochs.c |  3 +++
 samples/vfio-mdev/mdpy.c   |  3 +++
 samples/vfio-mdev/mtty.c   |  3 +++
 4 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/drivers/vfio/iommufd.c b/drivers/vfio/iommufd.c
index e40c0e9fea30..345ff8cf29e7 100644
--- a/drivers/vfio/iommufd.c
+++ b/drivers/vfio/iommufd.c
@@ -32,12 +32,8 @@ int vfio_iommufd_bind(struct vfio_device *vdev, struct iommufd_ctx *ictx)
 		return 0;
 	}
 
-	/*
-	 * If the driver doesn't provide this op then it means the device does
-	 * not do DMA at all. So nothing to do.
-	 */
-	if (!vdev->ops->bind_iommufd)
-		return 0;
+	if (WARN_ON(!vdev->ops->bind_iommufd))
+		return -ENODEV;
 
 	ret = vdev->ops->bind_iommufd(vdev, ictx, &device_id);
 	if (ret)
@@ -119,7 +115,8 @@ EXPORT_SYMBOL_GPL(vfio_iommufd_physical_attach_ioas);
 /*
  * The emulated standard ops mean that vfio_device is going to use the
  * "mdev path" and will call vfio_pin_pages()/vfio_dma_rw(). Drivers using this
- * ops set should call vfio_register_emulated_iommu_dev().
+ * ops set should call vfio_register_emulated_iommu_dev(). Drivers that do
+ * not call vfio_pin_pages()/vfio_dma_rw() have no need to provide dma_unmap.
  */
 
 static void vfio_emulated_unmap(void *data, unsigned long iova,
@@ -127,7 +124,8 @@ static void vfio_emulated_unmap(void *data, unsigned long iova,
 {
 	struct vfio_device *vdev = data;
 
-	vdev->ops->dma_unmap(vdev, iova, length);
+	if (vdev->ops->dma_unmap)
+		vdev->ops->dma_unmap(vdev, iova, length);
 }
 
 static const struct iommufd_access_ops vfio_user_ops = {
diff --git a/samples/vfio-mdev/mbochs.c b/samples/vfio-mdev/mbochs.c
index e54eb752e1ba..19391dda5fba 100644
--- a/samples/vfio-mdev/mbochs.c
+++ b/samples/vfio-mdev/mbochs.c
@@ -1374,6 +1374,9 @@ static const struct vfio_device_ops mbochs_dev_ops = {
 	.write = mbochs_write,
 	.ioctl = mbochs_ioctl,
 	.mmap = mbochs_mmap,
+	.bind_iommufd	= vfio_iommufd_emulated_bind,
+	.unbind_iommufd	= vfio_iommufd_emulated_unbind,
+	.attach_ioas	= vfio_iommufd_emulated_attach_ioas,
 };
 
 static struct mdev_driver mbochs_driver = {
diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c
index e8400fdab71d..5f48aef36995 100644
--- a/samples/vfio-mdev/mdpy.c
+++ b/samples/vfio-mdev/mdpy.c
@@ -663,6 +663,9 @@ static const struct vfio_device_ops mdpy_dev_ops = {
 	.write = mdpy_write,
 	.ioctl = mdpy_ioctl,
 	.mmap = mdpy_mmap,
+	.bind_iommufd	= vfio_iommufd_emulated_bind,
+	.unbind_iommufd	= vfio_iommufd_emulated_unbind,
+	.attach_ioas	= vfio_iommufd_emulated_attach_ioas,
 };
 
 static struct mdev_driver mdpy_driver = {
diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c
index e887de672c52..35460901b9f7 100644
--- a/samples/vfio-mdev/mtty.c
+++ b/samples/vfio-mdev/mtty.c
@@ -1269,6 +1269,9 @@ static const struct vfio_device_ops mtty_dev_ops = {
 	.read = mtty_read,
 	.write = mtty_write,
 	.ioctl = mtty_ioctl,
+	.bind_iommufd	= vfio_iommufd_emulated_bind,
+	.unbind_iommufd	= vfio_iommufd_emulated_unbind,
+	.attach_ioas	= vfio_iommufd_emulated_attach_ioas,
 };
 
 static struct mdev_driver mtty_driver = {
-- 
2.34.1