vhost: introduce driver features related APIs

Introduce few APIs to set/get/enable/disable driver features.

Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

doc/guides/prog_guide/vhost_lib.rst

@@ -53,7 +53,7 @@ vhost library should be able to:
 Vhost API Overview
 ------------------
 
-The following is an overview of the Vhost API functions:
+The following is an overview of some key Vhost API functions:
 
 * ``rte_vhost_driver_register(path, flags)``
 
@@ -110,6 +110,12 @@ The following is an overview of the Vhost API functions:
       of those segments, thus the fewer the segments, the quicker we will get
       the mapping. NOTE: we may speed it by using tree searching in future.
 
+* ``rte_vhost_driver_set_features(path, features)``
+
+  This function sets the feature bits the vhost-user driver supports. The
+  vhost-user driver could be vhost-user net, yet it could be something else,
+  say, vhost-user SCSI.
+
 * ``rte_vhost_driver_session_start()``
 
   This function starts the vhost session loop to handle vhost messages. It
@@ -145,7 +151,7 @@ The following is an overview of the Vhost API functions:
 
   Receives (dequeues) ``count`` packets from guest, and stored them at ``pkts``.
 
-* ``rte_vhost_feature_disable/rte_vhost_feature_enable(feature_mask)``
+* ``rte_vhost_driver_disable/enable_features(path, features))``
 
   This function disables/enables some features. For example, it can be used to
   disable mergeable buffers and TSO features, which both are enabled by

lib/librte_vhost/rte_vhost_version.map

@@ -34,6 +34,10 @@ DPDK_16.07 {
 DPDK_17.05 {
 	global:
 
+	rte_vhost_driver_disable_features;
+	rte_vhost_driver_enable_features;
+	rte_vhost_driver_get_features;
+	rte_vhost_driver_set_features;
 	rte_vhost_get_mtu;
 
 } DPDK_16.07;

lib/librte_vhost/rte_virtio_net.h

@@ -94,6 +94,61 @@ int rte_vhost_driver_register(const char *path, uint64_t flags);
 /* Unregister vhost driver. This is only meaningful to vhost user. */
 int rte_vhost_driver_unregister(const char *path);
 
+/**
+ * Set the feature bits the vhost-user driver supports.
+ *
+ * @param path
+ *  The vhost-user socket file path
+ * @param features
+ *  Supported features
+ * @return
+ *  0 on success, -1 on failure
+ */
+int rte_vhost_driver_set_features(const char *path, uint64_t features);
+
+/**
+ * Enable vhost-user driver features.
+ *
+ * Note that
+ * - the param features should be a subset of the feature bits provided
+ *   by rte_vhost_driver_set_features().
+ * - it must be invoked before vhost-user negotiation starts.
+ *
+ * @param path
+ *  The vhost-user socket file path
+ * @param features
+ *  Features to enable
+ * @return
+ *  0 on success, -1 on failure
+ */
+int rte_vhost_driver_enable_features(const char *path, uint64_t features);
+
+/**
+ * Disable vhost-user driver features.
+ *
+ * The two notes at rte_vhost_driver_enable_features() also apply here.
+ *
+ * @param path
+ *  The vhost-user socket file path
+ * @param features
+ *  Features to disable
+ * @return
+ *  0 on success, -1 on failure
+ */
+int rte_vhost_driver_disable_features(const char *path, uint64_t features);
+
+/**
+ * Get the feature bits before feature negotiation.
+ *
+ * @param path
+ *  The vhost-user socket file path
+ * @param features
+ *  A pointer to store the queried feature bits
+ * @return
+ *  0 on success, -1 on failure
+ */
+int rte_vhost_driver_get_features(const char *path, uint64_t *features);
+
 /* Register callbacks. */
 int rte_vhost_driver_callback_register(struct virtio_net_device_ops const * const);
 /* Start vhost driver session blocking loop. */

lib/librte_vhost/socket.c

@@ -67,6 +67,16 @@ struct vhost_user_socket {
 	bool is_server;
 	bool reconnect;
 	bool dequeue_zero_copy;
+
+	/*
+	 * The "supported_features" indicates the feature bits the
+	 * vhost driver supports. The "features" indicates the feature
+	 * bits after the rte_vhost_driver_features_disable/enable().
+	 * It is also the final feature bits used for vhost-user
+	 * features negotiation.
+	 */
+	uint64_t supported_features;
+	uint64_t features;
 };
 
 struct vhost_user_connection {
@@ -490,6 +500,88 @@ vhost_user_create_client(struct vhost_user_socket *vsocket)
 	return 0;
 }
 
+static struct vhost_user_socket *
+find_vhost_user_socket(const char *path)
+{
+	int i;
+
+	for (i = 0; i < vhost_user.vsocket_cnt; i++) {
+		struct vhost_user_socket *vsocket = vhost_user.vsockets[i];
+
+		if (!strcmp(vsocket->path, path))
+			return vsocket;
+	}
+
+	return NULL;
+}
+
+int
+rte_vhost_driver_disable_features(const char *path, uint64_t features)
+{
+	struct vhost_user_socket *vsocket;
+
+	pthread_mutex_lock(&vhost_user.mutex);
+	vsocket = find_vhost_user_socket(path);
+	if (vsocket)
+		vsocket->features &= ~features;
+	pthread_mutex_unlock(&vhost_user.mutex);
+
+	return vsocket ? 0 : -1;
+}
+
+int
+rte_vhost_driver_enable_features(const char *path, uint64_t features)
+{
+	struct vhost_user_socket *vsocket;
+
+	pthread_mutex_lock(&vhost_user.mutex);
+	vsocket = find_vhost_user_socket(path);
+	if (vsocket) {
+		if ((vsocket->supported_features & features) != features) {
+			/*
+			 * trying to enable features the driver doesn't
+			 * support.
+			 */
+			pthread_mutex_unlock(&vhost_user.mutex);
+			return -1;
+		}
+		vsocket->features |= features;
+	}
+	pthread_mutex_unlock(&vhost_user.mutex);
+
+	return vsocket ? 0 : -1;
+}
+
+int
+rte_vhost_driver_set_features(const char *path, uint64_t features)
+{
+	struct vhost_user_socket *vsocket;
+
+	pthread_mutex_lock(&vhost_user.mutex);
+	vsocket = find_vhost_user_socket(path);
+	if (vsocket) {
+		vsocket->supported_features = features;
+		vsocket->features = features;
+	}
+	pthread_mutex_unlock(&vhost_user.mutex);
+
+	return vsocket ? 0 : -1;
+}
+
+int
+rte_vhost_driver_get_features(const char *path, uint64_t *features)
+{
+	struct vhost_user_socket *vsocket;
+
+	pthread_mutex_lock(&vhost_user.mutex);
+	vsocket = find_vhost_user_socket(path);
+	if (vsocket)
+		*features = vsocket->features;
+	pthread_mutex_unlock(&vhost_user.mutex);
+
+	return vsocket ? 0 : -1;
+}
+
 /*
  * Register a new vhost-user socket; here we could act as server
  * (the default case), or client (when RTE_VHOST_USER_CLIENT) flag