[PATCH RFC 3/5] vhost-vdpa: support get/set backend features

[Jason Wang <jasowang@redhat.com>]

This patch makes userspace can get and set backend features to
vhost-vdpa.

Signed-off-by: Cindy Lu <lulu@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 drivers/vhost/vdpa.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index db4c9cb44c61..453057421f80 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -55,6 +55,10 @@ enum {
 		(1ULL << VIRTIO_NET_F_SPEED_DUPLEX),
 };
 
+enum {
+	VHOST_VDPA_BACKEND_FEATURES = (1ULL << VHOST_BACKEND_F_IOTLB_MSG_V2)
+};
+
 /* Currently, only network backend w/o multiqueue is supported. */
 #define VHOST_VDPA_VQ_MAX	2
 
@@ -340,6 +344,8 @@ static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
 	struct vdpa_callback cb;
 	struct vhost_virtqueue *vq;
 	struct vhost_vring_state s;
+	u64 __user *featurep = argp;
+	u64 features;
 	u32 idx;
 	long r;
 
@@ -362,6 +368,18 @@ static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
 	case VHOST_GET_VRING_BASE:
 		vq->last_avail_idx = ops->get_vq_state(v->vdpa, idx);
 		break;
+	case VHOST_GET_BACKEND_FEATURES:
+		features = VHOST_VDPA_BACKEND_FEATURES;
+		if (copy_to_user(featurep, &features, sizeof(features)))
+			return -EFAULT;
+		return 0;
+	case VHOST_SET_BACKEND_FEATURES:
+		if (copy_from_user(&features, featurep, sizeof(features)))
+			return -EFAULT;
+		if (features & ~VHOST_VDPA_BACKEND_FEATURES)
+			return -EOPNOTSUPP;
+		vhost_set_backend_features(&v->vdev, features);
+		return 0;
 	}
 
 	r = vhost_vring_ioctl(&v->vdev, cmd, argp);
-- 
2.20.1