[PATCH] vdpa: mandate 1.0 device

[Jason Wang <jasowang@redhat.com>]

This patch mandates 1.0 for vDPA devices. The plan is never to support
transitional devices for vDPA devices in the future.

The reasons are:

- To have the semantic of normative statement in the virtio spec and
  eliminate the burden of transitional device for both vDPA bus and
  vDPA parent
- Eliminate the efforts for dealing with endian conversion in the
  management tool
- Mandate vDPA vendor to ship modern device instead of transitional
  device which is easily broken and unsafe
- Transitional device never work since the first day of vDPA

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 include/linux/vdpa.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h
index f311d227aa1b..11dd05b805a7 100644
--- a/include/linux/vdpa.h
+++ b/include/linux/vdpa.h
@@ -6,6 +6,7 @@
 #include <linux/device.h>
 #include <linux/interrupt.h>
 #include <linux/vhost_iotlb.h>
+#include <uapi/linux/virtio_config.h>
 
 /**
  * struct vdpa_calllback - vDPA callback definition.
@@ -328,6 +329,11 @@ static inline int vdpa_set_features(struct vdpa_device *vdev, u64 features)
 {
         const struct vdpa_config_ops *ops = vdev->config;
 
+        /* Mandating 1.0 to have semantics of normative statements in
+         * the spec. */
+        if (!(features & BIT_ULL(VIRTIO_F_VERSION_1)))
+		return -EINVAL;
+
 	vdev->features_valid = true;
         return ops->set_features(vdev, features);
 }
-- 
2.25.1