[dpdk-dev] [PATCH v6 1/2] vhost: add support for interrupt mode

[Junjie Chen]

In some cases we want vhost dequeue work in interrupt mode to
release cpus to others when no data to transmit. So we install
interrupt handler of vhost device and interrupt vectors for each
rx queue when creating new backend according to vhost intrerupt
configuration. Thus, applications could register a epoll event fd
to associate rx queues with interrupt vectors.

Signed-off-by: Junjie Chen <junjie.j.chen at intel.com>
---
Changes in v6:
- rebase code to master
Changes in v5:
- update license to DPDK new license format
- rebase code to master 
Changes in v4:
- revert back license change
Changes in v3:
- handle failure in the middle of intr setup.
- use vhost API to enable interrupt.
- rebase to check rxq existence.
- update vhost API to support guest notification.
Changes in v2:
- update rx queue index.
- fill efd_counter_size for intr handler.
- update log.
 drivers/net/vhost/rte_eth_vhost.c | 158 +++++++++++++++++++++++++++++++++++++-
 lib/librte_vhost/vhost.c          |  14 ++--
 2 files changed, 163 insertions(+), 9 deletions(-)

diff --git a/drivers/net/vhost/rte_eth_vhost.c b/drivers/net/vhost/rte_eth_vhost.c
index e392d71..8b4b716 100644
--- a/drivers/net/vhost/rte_eth_vhost.c
+++ b/drivers/net/vhost/rte_eth_vhost.c
@@ -520,6 +520,136 @@ find_internal_resource(char *ifname)
 	return list;
 }
 
+static int
+eth_rxq_intr_enable(struct rte_eth_dev *dev, uint16_t qid)
+{
+	struct rte_vhost_vring vring;
+	struct vhost_queue *vq;
+	int ret = 0;
+
+	vq = dev->data->rx_queues[qid];
+	if (!vq) {
+		RTE_LOG(ERR, PMD, "rxq%d is not setup yet\n", qid);
+		return -1;
+	}
+
+	ret = rte_vhost_get_vhost_vring(vq->vid, (qid << 1) + 1, &vring);
+	if (ret < 0) {
+		RTE_LOG(ERR, PMD, "Failed to get rxq%d's vring\n", qid);
+		return ret;
+	}
+	RTE_LOG(INFO, PMD, "Enable interrupt for rxq%d\n", qid);
+	rte_vhost_enable_guest_notification(vq->vid, (qid << 1) + 1, 1);
+	rte_wmb();
+
+	return ret;
+}
+
+static int
+eth_rxq_intr_disable(struct rte_eth_dev *dev, uint16_t qid)
+{
+	struct rte_vhost_vring vring;
+	struct vhost_queue *vq;
+	int ret = 0;
+
+	vq = dev->data->rx_queues[qid];
+	if (!vq) {
+		RTE_LOG(ERR, PMD, "rxq%d is not setup yet\n", qid);
+		return -1;
+	}
+
+	ret = rte_vhost_get_vhost_vring(vq->vid, (qid << 1) + 1, &vring);
+	if (ret < 0) {
+		RTE_LOG(ERR, PMD, "Failed to get rxq%d's vring", qid);
+		return ret;
+	}
+	RTE_LOG(INFO, PMD, "Disable interrupt for rxq%d\n", qid);
+	rte_vhost_enable_guest_notification(vq->vid, (qid << 1) + 1, 0);
+	rte_wmb();
+
+	return 0;
+}
+
+static void
+eth_vhost_uninstall_intr(struct rte_eth_dev *dev)
+{
+	struct rte_intr_handle *intr_handle = dev->intr_handle;
+
+	if (intr_handle) {
+		if (intr_handle->intr_vec)
+			free(intr_handle->intr_vec);
+		free(intr_handle);
+	}
+
+	dev->intr_handle = NULL;
+}
+
+static int
+eth_vhost_install_intr(struct rte_eth_dev *dev)
+{
+	struct rte_vhost_vring vring;
+	struct vhost_queue *vq;
+	int count = 0;
+	int nb_rxq = dev->data->nb_rx_queues;
+	int i;
+	int ret;
+
+	/* uninstall firstly if we are reconnecting */
+	if (dev->intr_handle)
+		eth_vhost_uninstall_intr(dev);
+
+	dev->intr_handle = malloc(sizeof(*dev->intr_handle));
+	if (!dev->intr_handle) {
+		RTE_LOG(ERR, PMD, "Fail to allocate intr_handle\n");
+		return -ENOMEM;
+	}
+	memset(dev->intr_handle, 0, sizeof(*dev->intr_handle));
+
+	dev->intr_handle->efd_counter_size = sizeof(uint64_t);
+
+	dev->intr_handle->intr_vec =
+		malloc(nb_rxq * sizeof(dev->intr_handle->intr_vec[0]));
+
+	if (!dev->intr_handle->intr_vec) {
+		RTE_LOG(ERR, PMD,
+			"Failed to allocate memory for interrupt vector\n");
+		free(dev->intr_handle);
+		return -ENOMEM;
+	}
+
+	RTE_LOG(INFO, PMD, "Prepare intr vec\n");
+	for (i = 0; i < nb_rxq; i++) {
+		vq = dev->data->rx_queues[i];
+		if (!vq) {
+			RTE_LOG(INFO, PMD, "rxq-%d not setup yet, skip!\n", i);
+			continue;
+		}
+
+		ret = rte_vhost_get_vhost_vring(vq->vid, (i << 1) + 1, &vring);
+		if (ret < 0) {
+			RTE_LOG(INFO, PMD,
+				"Failed to get rxq-%d's vring, skip!\n", i);
+			continue;
+		}
+
+		if (vring.kickfd < 0) {
+			RTE_LOG(INFO, PMD,
+				"rxq-%d's kickfd is invalid, skip!\n", i);
+			continue;
+		}
+		dev->intr_handle->intr_vec[i] = RTE_INTR_VEC_RXTX_OFFSET + i;
+		dev->intr_handle->efds[i] = vring.kickfd;
+		count++;
+		RTE_LOG(INFO, PMD, "Installed intr vec for rxq-%d\n", i);
+	}
+
+	dev->intr_handle->nb_efd = count;
+	dev->intr_handle->max_intr = count + 1;
+	dev->intr_handle->type = RTE_INTR_HANDLE_VDEV;
+
+	return 0;
+}
+
 static void
 update_queuing_status(struct rte_eth_dev *dev)
 {
@@ -585,6 +715,7 @@ new_device(int vid)
 	struct rte_eth_dev *eth_dev;
 	struct internal_list *list;
 	struct pmd_internal *internal;
+	struct rte_eth_conf *dev_conf;
 	unsigned i;
 	char ifname[PATH_MAX];
 #ifdef RTE_LIBRTE_VHOST_NUMA
@@ -600,6 +731,7 @@ new_device(int vid)
 
 	eth_dev = list->eth_dev;
 	internal = eth_dev->data->dev_private;
+	dev_conf = &eth_dev->data->dev_conf;
 
 #ifdef RTE_LIBRTE_VHOST_NUMA
 	newnode = rte_vhost_get_numa_node(vid);
@@ -608,8 +740,17 @@ new_device(int vid)
 #endif
 
 	internal->vid = vid;
-	if (rte_atomic32_read(&internal->started) == 1)
+	if (rte_atomic32_read(&internal->started) == 1) {
 		queue_setup(eth_dev, internal);
+
+		if (dev_conf->intr_conf.rxq) {
+			if (eth_vhost_install_intr(eth_dev) < 0) {
+				RTE_LOG(INFO, PMD,
+					"Failed to install interrupt handler.");
+					return -1;
+			}
+		}
+	}
 	else
 		RTE_LOG(INFO, PMD, "RX/TX queues not exist yet\n");
 
@@ -680,6 +821,7 @@ destroy_device(int vid)
 	rte_spinlock_unlock(&state->lock);
 
 	RTE_LOG(INFO, PMD, "Vhost device %d destroyed\n", vid);
+	eth_vhost_uninstall_intr(eth_dev);
 
 	_rte_eth_dev_callback_process(eth_dev, RTE_ETH_EVENT_INTR_LSC, NULL);
 }
@@ -791,8 +933,20 @@ static int
 eth_dev_start(struct rte_eth_dev *eth_dev)
 {
 	struct pmd_internal *internal = eth_dev->data->dev_private;
+	struct rte_eth_conf *dev_conf = &eth_dev->data->dev_conf;
 
 	queue_setup(eth_dev, internal);
+	
+	if (rte_atomic32_read(&internal->dev_attached) == 1) {
+		if (dev_conf->intr_conf.rxq) {
+			if (eth_vhost_install_intr(eth_dev) < 0) {
+				RTE_LOG(INFO, PMD,
+					"Failed to install interrupt handler.");
+					return -1;
+			}
+		}
+	}
+
 	rte_atomic32_set(&internal->started, 1);
 	update_queuing_status(eth_dev);
 
@@ -1029,6 +1183,8 @@ static const struct eth_dev_ops ops = {
 	.xstats_reset = vhost_dev_xstats_reset,
 	.xstats_get = vhost_dev_xstats_get,
 	.xstats_get_names = vhost_dev_xstats_get_names,
+	.rx_queue_intr_enable = eth_rxq_intr_enable,
+	.rx_queue_intr_disable = eth_rxq_intr_disable,
 };
 
 static struct rte_vdev_driver pmd_vhost_drv;
diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c
index f6f12a0..10f795f 100644
--- a/lib/librte_vhost/vhost.c
+++ b/lib/librte_vhost/vhost.c
@@ -545,16 +545,14 @@ rte_vhost_enable_guest_notification(int vid, uint16_t queue_id, int enable)
 {
 	struct virtio_net *dev = get_device(vid);
 
-	if (dev == NULL)
-		return -1;
-
-	if (enable) {
-		RTE_LOG(ERR, VHOST_CONFIG,
-			"guest notification isn't supported.\n");
+	if (!dev)
 		return -1;
-	}
 
-	dev->virtqueue[queue_id]->used->flags = VRING_USED_F_NO_NOTIFY;
+	if (enable)
+		dev->virtqueue[queue_id]->used->flags &=
+			~VRING_USED_F_NO_NOTIFY;
+	else	
+		dev->virtqueue[queue_id]->used->flags |= VRING_USED_F_NO_NOTIFY;
 	return 0;
 }
 
-- 
2.0.1