[PATCH v1 15/21] net/virtio-user: get max number of queue pairs from device

[Maxime Coquelin <maxime.coquelin@redhat.com>]

When supported by the backend (only vDPA for now), this
patch gets the maximum number of queue pairs supported by
the device by querying it in its config space.

This is required for adding backend control queue support,
as is index equals the maximum number of queues supported
by the device as described by the Virtio specification.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 .../net/virtio/virtio_user/virtio_user_dev.c  | 93 ++++++++++++++-----
 drivers/net/virtio/virtio_user_ethdev.c       |  7 --
 2 files changed, 71 insertions(+), 29 deletions(-)

diff --git a/drivers/net/virtio/virtio_user/virtio_user_dev.c b/drivers/net/virtio/virtio_user/virtio_user_dev.c
index 809c9ef442..a3584e7735 100644
--- a/drivers/net/virtio/virtio_user/virtio_user_dev.c
+++ b/drivers/net/virtio/virtio_user/virtio_user_dev.c
@@ -253,6 +253,50 @@ int virtio_user_stop_device(struct virtio_user_dev *dev)
 	return -1;
 }
 
+static int
+virtio_user_dev_init_max_queue_pairs(struct virtio_user_dev *dev, uint32_t user_max_qp)
+{
+	int ret;
+
+	if (!(dev->device_features & (1ULL << VIRTIO_NET_F_MQ))) {
+		dev->max_queue_pairs = 1;
+		return 0;
+	}
+
+	if (!dev->ops->get_config) {
+		dev->max_queue_pairs = user_max_qp;
+		return 0;
+	}
+
+	ret = dev->ops->get_config(dev, (uint8_t *)&dev->max_queue_pairs,
+			offsetof(struct virtio_net_config, max_virtqueue_pairs),
+			sizeof(uint16_t));
+	if (ret) {
+		/*
+		 * We need to know the max queue pair from the device so that
+		 * the control queue gets the right index.
+		 */
+		dev->max_queue_pairs = 1;
+		PMD_DRV_LOG(ERR, "(%s) Failed to get max queue pairs from device", dev->path);
+
+		return ret;
+	}
+
+	if (dev->max_queue_pairs > VIRTIO_MAX_VIRTQUEUE_PAIRS) {
+		/*
+		 * If the device supports control queue, the control queue
+		 * index is max_virtqueue_pairs * 2. Disable MQ if it happens.
+		 */
+		PMD_DRV_LOG(ERR, "(%s) Device advertises too many queues (%u, max supported %u)",
+				dev->path, dev->max_queue_pairs, VIRTIO_MAX_VIRTQUEUE_PAIRS);
+		dev->max_queue_pairs = 1;
+
+		return -1;
+	}
+
+	return 0;
+}
+
 int
 virtio_user_dev_set_mac(struct virtio_user_dev *dev)
 {
@@ -511,24 +555,7 @@ virtio_user_dev_setup(struct virtio_user_dev *dev)
 		return -1;
 	}
 
-	if (virtio_user_dev_init_notify(dev) < 0) {
-		PMD_INIT_LOG(ERR, "(%s) Failed to init notifiers", dev->path);
-		goto destroy;
-	}
-
-	if (virtio_user_fill_intr_handle(dev) < 0) {
-		PMD_INIT_LOG(ERR, "(%s) Failed to init interrupt handler", dev->path);
-		goto uninit;
-	}
-
 	return 0;
-
-uninit:
-	virtio_user_dev_uninit_notify(dev);
-destroy:
-	dev->ops->destroy(dev);
-
-	return -1;
 }
 
 /* Use below macro to filter features from vhost backend */
@@ -570,7 +597,6 @@ virtio_user_dev_init(struct virtio_user_dev *dev, char *path, uint16_t queues,
 	}
 
 	dev->started = 0;
-	dev->max_queue_pairs = queues;
 	dev->queue_pairs = 1; /* mq disabled by default */
 	dev->queue_size = queue_size;
 	dev->is_server = server;
@@ -591,23 +617,39 @@ virtio_user_dev_init(struct virtio_user_dev *dev, char *path, uint16_t queues,
 
 	if (dev->ops->set_owner(dev) < 0) {
 		PMD_INIT_LOG(ERR, "(%s) Failed to set backend owner", dev->path);
-		return -1;
+		goto destroy;
 	}
 
 	if (dev->ops->get_backend_features(&backend_features) < 0) {
 		PMD_INIT_LOG(ERR, "(%s) Failed to get backend features", dev->path);
-		return -1;
+		goto destroy;
 	}
 
 	dev->unsupported_features = ~(VIRTIO_USER_SUPPORTED_FEATURES | backend_features);
 
 	if (dev->ops->get_features(dev, &dev->device_features) < 0) {
 		PMD_INIT_LOG(ERR, "(%s) Failed to get device features", dev->path);
-		return -1;
+		goto destroy;
 	}
 
 	virtio_user_dev_init_mac(dev, mac);
 
+	if (virtio_user_dev_init_max_queue_pairs(dev, queues))
+		dev->unsupported_features |= (1ull << VIRTIO_NET_F_MQ);
+
+	if (dev->max_queue_pairs > 1)
+		cq = 1;
+
+	if (virtio_user_dev_init_notify(dev) < 0) {
+		PMD_INIT_LOG(ERR, "(%s) Failed to init notifiers", dev->path);
+		goto destroy;
+	}
+
+	if (virtio_user_fill_intr_handle(dev) < 0) {
+		PMD_INIT_LOG(ERR, "(%s) Failed to init interrupt handler", dev->path);
+		goto notify_uninit;
+	}
+
 	if (!mrg_rxbuf)
 		dev->unsupported_features |= (1ull << VIRTIO_NET_F_MRG_RXBUF);
 
@@ -651,11 +693,18 @@ virtio_user_dev_init(struct virtio_user_dev *dev, char *path, uint16_t queues,
 		if (rte_errno != ENOTSUP) {
 			PMD_INIT_LOG(ERR, "(%s) Failed to register mem event callback",
 					dev->path);
-			return -1;
+			goto notify_uninit;
 		}
 	}
 
 	return 0;
+
+notify_uninit:
+	virtio_user_dev_uninit_notify(dev);
+destroy:
+	dev->ops->destroy(dev);
+
+	return -1;
 }
 
 void
diff --git a/drivers/net/virtio/virtio_user_ethdev.c b/drivers/net/virtio/virtio_user_ethdev.c
index 6ad5896378..6c3e875793 100644
--- a/drivers/net/virtio/virtio_user_ethdev.c
+++ b/drivers/net/virtio/virtio_user_ethdev.c
@@ -595,8 +595,6 @@ virtio_user_pmd_probe(struct rte_vdev_device *vdev)
 				     VIRTIO_USER_ARG_CQ_NUM);
 			goto end;
 		}
-	} else if (queues > 1) {
-		cq = 1;
 	}
 
 	if (rte_kvargs_count(kvlist, VIRTIO_USER_ARG_PACKED_VQ) == 1) {
@@ -617,11 +615,6 @@ virtio_user_pmd_probe(struct rte_vdev_device *vdev)
 		}
 	}
 
-	if (queues > 1 && cq == 0) {
-		PMD_INIT_LOG(ERR, "multi-q requires ctrl-q");
-		goto end;
-	}
-
 	if (queues > VIRTIO_MAX_VIRTQUEUE_PAIRS) {
 		PMD_INIT_LOG(ERR, "arg %s %" PRIu64 " exceeds the limit %u",
 			VIRTIO_USER_ARG_QUEUES_NUM, queues,
-- 
2.38.1