-----Original Message-----
From: Maxime Coquelin <redacted>
Sent: Monday, December 21, 2020 5:14 AM
To: dev@dpdk.org; Xia, Chenbo <redacted>; olivier.matz@6wind.com;
amorenoz@redhat.com; david.marchand@redhat.com
Cc: Maxime Coquelin <redacted>
Subject: [PATCH 35/40] net/virtio: make server mode blocking

This patch makes the Vhost-user backend server mode
blocking at init, waiting for the client connection.

The goal is to make the driver more reliable, as without
waiting for client connection, the Virtio driver has to
assume the Vhost-user backend will support all the
features it has advertized, which could lead to undefined
behaviour.

For example, without this patch, if the user enables packed
ring Virtio feature but the backend does not support it,
the ring initialized by the driver will not be compatible
with the backend.

Signed-off-by: Maxime Coquelin <redacted>
---
 drivers/net/virtio/virtio_user/vhost_user.c   |   9 +-
 .../net/virtio/virtio_user/virtio_user_dev.c  | 118 +++++++-----------
 drivers/net/virtio/virtio_user_ethdev.c       |   5 -
 3 files changed, 54 insertions(+), 78 deletions(-)

diff --git a/drivers/net/virtio/virtio_user/vhost_user.c

b/drivers/net/virtio/virtio_user/vhost_user.c
index a57106a468..94a33326ae 100644

--- a/drivers/net/virtio/virtio_user/vhost_user.c
+++ b/drivers/net/virtio/virtio_user/vhost_user.c

@@ -677,6 +677,14 @@ virtio_user_start_server(struct virtio_user_dev *dev,

struct sockaddr_un *un)
 	if (ret < 0)
 		return -1;

+	PMD_DRV_LOG(NOTICE, "(%s) waiting for client connection...", dev->path);
+	dev->vhostfd = accept(fd, NULL, NULL);
+	if (dev->vhostfd < 0) {
+		PMD_DRV_LOG(ERR, "Failed to accept initial client connection (%s)",
+				strerror(errno));
+		return -1;
+	}
+
 	flag = fcntl(fd, F_GETFL);
 	if (fcntl(fd, F_SETFL, flag | O_NONBLOCK) < 0) {
 		PMD_DRV_LOG(ERR, "fcntl failed, %s", strerror(errno));

@@ -721,7 +729,6 @@ vhost_user_setup(struct virtio_user_dev *dev)
 			close(fd);
 			return -1;
 		}
-		dev->vhostfd = -1;
 	} else {
 		if (connect(fd, (struct sockaddr *)&un, sizeof(un)) < 0) {
 			PMD_DRV_LOG(ERR, "connect error, %s", strerror(errno));

diff --git a/drivers/net/virtio/virtio_user/virtio_user_dev.c

b/drivers/net/virtio/virtio_user/virtio_user_dev.c
index b92b7f7aae..19d59d401e 100644

--- a/drivers/net/virtio/virtio_user/virtio_user_dev.c
+++ b/drivers/net/virtio/virtio_user/virtio_user_dev.c

@@ -144,10 +144,6 @@ virtio_user_dev_set_features(struct virtio_user_dev *dev)

 	pthread_mutex_lock(&dev->mutex);

-	if (dev->backend_type == VIRTIO_USER_BACKEND_VHOST_USER &&
-			dev->vhostfd < 0)
-		goto error;
-
 	/* Step 0: tell vhost to create queues */
 	if (virtio_user_queue_setup(dev, virtio_user_create_queue) < 0)
 		goto error;

@@ -190,11 +186,6 @@ virtio_user_start_device(struct virtio_user_dev *dev)
 	rte_mcfg_mem_read_lock();
 	pthread_mutex_lock(&dev->mutex);

-	/* Vhost-user client not connected yet, will start later */
-	if (dev->backend_type == VIRTIO_USER_BACKEND_VHOST_USER &&
-			dev->vhostfd < 0)
-		goto out;
-
 	/* Step 2: share memory regions */
 	ret = dev->ops->set_memory_table(dev);
 	if (ret < 0)

@@ -213,7 +204,7 @@ virtio_user_start_device(struct virtio_user_dev *dev)
 		goto error;

 	dev->started = true;
-out:
+
 	pthread_mutex_unlock(&dev->mutex);
 	rte_mcfg_mem_read_unlock();

@@ -421,36 +412,36 @@ virtio_user_dev_setup(struct virtio_user_dev *dev)
 			PMD_DRV_LOG(ERR, "Server mode only supports vhost-user!");
 			return -1;
 		}
+	}
+
+	if (dev->backend_type == VIRTIO_USER_BACKEND_VHOST_USER) {
 		dev->ops = &virtio_ops_user;
-	} else {
-		if (dev->backend_type == VIRTIO_USER_BACKEND_VHOST_USER) {
-			dev->ops = &virtio_ops_user;
-		} else if (dev->backend_type ==
-					VIRTIO_USER_BACKEND_VHOST_KERNEL) {
-			dev->ops = &virtio_ops_kernel;
-
-			dev->vhostfds = malloc(dev->max_queue_pairs *
-					       sizeof(int));
-			dev->tapfds = malloc(dev->max_queue_pairs *
-					     sizeof(int));
-			if (!dev->vhostfds || !dev->tapfds) {
-				PMD_INIT_LOG(ERR, "(%s) Failed to allocate FDs", dev-

quoted

path);

-				return -1;