[dpdk-dev] [RFC 10/24] vhost: embed struct virtio_net inside struct vhost_user_connection

[Stefan Hajnoczi]

There is a 1:1 relationship between struct virtio_net and struct
vhost_user_connection.  They share the same lifetime.  struct virtio_net
is the per-device state that is part of the vhost.h API.  struct
vhost_user_connection is the AF_UNIX-specific per-device state and is
private to trans_af_unix.c.  It will be necessary to go between these
two structs.

This patch embeds struct virtio_net within struct vhost_user_connection
so that AF_UNIX transport code can convert a struct virtio_net pointer
into a struct vhost_user_connection pointer.  There is now just a single
malloc/free for both of these structs together.

Signed-off-by: Stefan Hajnoczi <stefanha at redhat.com>
---
 lib/librte_vhost/vhost.h         | 11 +++++++++-
 lib/librte_vhost/trans_af_unix.c | 44 +++++++++++++++++-----------------------
 lib/librte_vhost/vhost.c         | 10 ++++-----
 3 files changed, 34 insertions(+), 31 deletions(-)

diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
index ca7507284..757e18391 100644
--- a/lib/librte_vhost/vhost.h
+++ b/lib/librte_vhost/vhost.h
@@ -211,6 +211,9 @@ struct vhost_transport_ops {
 	/** Size of struct vhost_user_socket-derived per-socket state */
 	size_t socket_size;
 
+	/** Size of struct virtio_net-derived per-device state */
+	size_t device_size;
+
 	/**
 	 * Initialize a vhost-user socket that is being created by
 	 * rte_vhost_driver_register().  This function checks that the flags
@@ -269,6 +272,11 @@ extern const struct vhost_transport_ops af_unix_trans_ops;
 /**
  * Device structure contains all configuration information relating
  * to the device.
+ *
+ * Transport-specific per-device state can be kept by embedding this struct at
+ * the beginning of a transport-specific struct.  Set
+ * vhost_transport_ops->device_size to the size of the transport-specific
+ * struct.
  */
 struct virtio_net {
 	/* Frontend (QEMU) memory and memory region information */
@@ -434,7 +442,8 @@ gpa_to_hpa(struct virtio_net *dev, uint64_t gpa, uint64_t size)
 
 struct virtio_net *get_device(int vid);
 
-int vhost_new_device(const struct vhost_transport_ops *trans_ops);
+struct virtio_net *
+vhost_new_device(const struct vhost_transport_ops *trans_ops);
 void cleanup_device(struct virtio_net *dev, int destroy);
 void reset_device(struct virtio_net *dev);
 void vhost_destroy_device(int);
diff --git a/lib/librte_vhost/trans_af_unix.c b/lib/librte_vhost/trans_af_unix.c
index c85a162e8..dde3e76cd 100644
--- a/lib/librte_vhost/trans_af_unix.c
+++ b/lib/librte_vhost/trans_af_unix.c
@@ -54,9 +54,9 @@ static struct fdset af_unix_fdset = {
 TAILQ_HEAD(vhost_user_connection_list, vhost_user_connection);
 
 struct vhost_user_connection {
+	struct virtio_net device; /* must be the first field! */
 	struct vhost_user_socket *vsocket;
 	int connfd;
-	int vid;
 
 	TAILQ_ENTRY(vhost_user_connection) next;
 };
@@ -165,32 +165,30 @@ vhost_user_add_connection(int fd, struct vhost_user_socket *vsocket)
 {
 	struct af_unix_socket *s =
 		container_of(vsocket, struct af_unix_socket, socket);
-	int vid;
 	size_t size;
+	struct virtio_net *dev;
 	struct vhost_user_connection *conn;
 	int ret;
 
-	conn = malloc(sizeof(*conn));
-	if (conn == NULL) {
-		close(fd);
+	dev = vhost_new_device(vsocket->trans_ops);
+	if (!dev) {
 		return;
 	}
 
-	vid = vhost_new_device(vsocket->trans_ops);
-	if (vid == -1) {
-		goto err;
-	}
+	conn = container_of(dev, struct vhost_user_connection, device);
+	conn->connfd = fd;
+	conn->vsocket = vsocket;
 
 	size = strnlen(vsocket->path, PATH_MAX);
-	vhost_set_ifname(vid, vsocket->path, size);
+	vhost_set_ifname(dev->vid, vsocket->path, size);
 
 	if (vsocket->dequeue_zero_copy)
-		vhost_enable_dequeue_zero_copy(vid);
+		vhost_enable_dequeue_zero_copy(dev->vid);
 
-	RTE_LOG(INFO, VHOST_CONFIG, "new device, handle is %d\n", vid);
+	RTE_LOG(INFO, VHOST_CONFIG, "new device, handle is %d\n", dev->vid);
 
 	if (vsocket->notify_ops->new_connection) {
-		ret = vsocket->notify_ops->new_connection(vid);
+		ret = vsocket->notify_ops->new_connection(dev->vid);
 		if (ret < 0) {
 			RTE_LOG(ERR, VHOST_CONFIG,
 				"failed to add vhost user connection with fd %d\n",
@@ -199,9 +197,6 @@ vhost_user_add_connection(int fd, struct vhost_user_socket *vsocket)
 		}
 	}
 
-	conn->connfd = fd;
-	conn->vsocket = vsocket;
-	conn->vid = vid;
 	ret = fdset_add(&af_unix_fdset, fd, vhost_user_read_cb,
 			NULL, conn);
 	if (ret < 0) {
@@ -210,7 +205,7 @@ vhost_user_add_connection(int fd, struct vhost_user_socket *vsocket)
 			fd);
 
 		if (vsocket->notify_ops->destroy_connection)
-			vsocket->notify_ops->destroy_connection(conn->vid);
+			vsocket->notify_ops->destroy_connection(dev->vid);
 
 		goto err;
 	}
@@ -221,8 +216,8 @@ vhost_user_add_connection(int fd, struct vhost_user_socket *vsocket)
 	return;
 
 err:
-	free(conn);
-	close(fd);
+	close(conn->connfd);
+	vhost_destroy_device(dev->vid);
 }
 
 /* call back when there is new vhost-user connection from client  */
@@ -248,20 +243,19 @@ vhost_user_read_cb(int connfd, void *dat, int *remove)
 		container_of(vsocket, struct af_unix_socket, socket);
 	int ret;
 
-	ret = vhost_user_msg_handler(conn->vid, connfd);
+	ret = vhost_user_msg_handler(conn->device.vid, connfd);
 	if (ret < 0) {
 		close(connfd);
 		*remove = 1;
-		vhost_destroy_device(conn->vid);
 
 		if (vsocket->notify_ops->destroy_connection)
-			vsocket->notify_ops->destroy_connection(conn->vid);
+			vsocket->notify_ops->destroy_connection(conn->device.vid);
 
 		pthread_mutex_lock(&s->conn_mutex);
 		TAILQ_REMOVE(&s->conn_list, conn, next);
 		pthread_mutex_unlock(&s->conn_mutex);
 
-		free(conn);
+		vhost_destroy_device(conn->device.vid);
 
 		if (vsocket->reconnect) {
 			create_unix_socket(vsocket);
@@ -576,9 +570,8 @@ af_unix_socket_cleanup(struct vhost_user_socket *vsocket)
 			"free connfd = %d for device '%s'\n",
 			conn->connfd, vsocket->path);
 		close(conn->connfd);
-		vhost_destroy_device(conn->vid);
 		TAILQ_REMOVE(&s->conn_list, conn, next);
-		free(conn);
+		vhost_destroy_device(conn->device.vid);
 	}
 	pthread_mutex_unlock(&s->conn_mutex);
 
@@ -615,6 +608,7 @@ af_unix_vring_call(struct virtio_net *dev __rte_unused,
 
 const struct vhost_transport_ops af_unix_trans_ops = {
 	.socket_size = sizeof(struct af_unix_socket),
+	.device_size = sizeof(struct vhost_user_connection),
 	.socket_init = af_unix_socket_init,
 	.socket_cleanup = af_unix_socket_cleanup,
 	.socket_start = af_unix_socket_start,
diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c
index f8754e261..1168e137e 100644
--- a/lib/librte_vhost/vhost.c
+++ b/lib/librte_vhost/vhost.c
@@ -260,17 +260,17 @@ reset_device(struct virtio_net *dev)
  * Invoked when there is a new vhost-user connection established (when
  * there is a new virtio device being attached).
  */
-int
+struct virtio_net *
 vhost_new_device(const struct vhost_transport_ops *trans_ops)
 {
 	struct virtio_net *dev;
 	int i;
 
-	dev = rte_zmalloc(NULL, sizeof(struct virtio_net), 0);
+	dev = rte_zmalloc(NULL, trans_ops->device_size, 0);
 	if (dev == NULL) {
 		RTE_LOG(ERR, VHOST_CONFIG,
 			"Failed to allocate memory for new dev.\n");
-		return -1;
+		return NULL;
 	}
 
 	for (i = 0; i < MAX_VHOST_DEVICE; i++) {
@@ -281,7 +281,7 @@ vhost_new_device(const struct vhost_transport_ops *trans_ops)
 		RTE_LOG(ERR, VHOST_CONFIG,
 			"Failed to find a free slot for new device.\n");
 		rte_free(dev);
-		return -1;
+		return NULL;
 	}
 
 	vhost_devices[i] = dev;
@@ -289,7 +289,7 @@ vhost_new_device(const struct vhost_transport_ops *trans_ops)
 	dev->slave_req_fd = -1;
 	dev->trans_ops = trans_ops;
 
-	return i;
+	return dev;
 }
 
 /*
-- 
2.14.3