+static void
+vhost_user_get_protocol_features(struct virtio_net *dev,
+ struct VhostUserMsg *msg)
+{
+ uint64_t features, protocol_features = VHOST_USER_PROTOCOL_FEATURES;
+
+ rte_vhost_driver_get_features(dev->ifname, &features);
+
+ /*
+ * REPLY_ACK protocol feature is only mandatory for now
+ * for IOMMU feature. If IOMMU is explicitly disabled by the
+ * application, disable also REPLY_ACK feature for older buggy
+ * Qemu versions (from v2.7.0 to v2.9.0).
+ */
+ if (!(features & (1ULL << VIRTIO_F_IOMMU_PLATFORM)))
+ protocol_features &= ~(1ULL << VHOST_USER_PROTOCOL_F_REPLY_ACK);
+
+ msg->payload.u64 = protocol_features;
+ msg->size = sizeof(msg->payload.u64);
+}
+