Re: [dpdk-dev] [PATCH v2] vhost: add support for interrupt mode

["Tan, Jianfeng" <jianfeng.tan@intel.com>]

On 3/29/2018 10:37 PM, Junjie Chen wrote:
> 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@intel.com>
> ---
> Changes in v2:
> - update rx queue index
> - fill efd_counter_size for intr handler
> - update log
>
>   drivers/net/vhost/rte_eth_vhost.c | 130 ++++++++++++++++++++++++++++++++++++++
>   1 file changed, 130 insertions(+)
>
> diff --git a/drivers/net/vhost/rte_eth_vhost.c b/drivers/net/vhost/rte_eth_vhost.c
> index 3aae01c..b2d925e 100644
> --- a/drivers/net/vhost/rte_eth_vhost.c
> +++ b/drivers/net/vhost/rte_eth_vhost.c
> @@ -552,12 +552,129 @@ update_queuing_status(struct rte_eth_dev *dev)
>   }
>   
>   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);
> +	vring.used->flags &= (~VRING_USED_F_NO_NOTIFY);

Instead, you might want to use the API, rte_vhost_enable_guest_notification.

> +	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);
> +	vring.used->flags |= VRING_USED_F_NO_NOTIFY;
> +	rte_wmb();

Ditto.

> +
> +	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);

I did not read-clean this for virtio-user. But we'd better keep 
consistent, to avoid confusion. If we need read-clean this, we could fix 
virtio-user.

> +
> +	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");

For completeness, we need to uninstall before return.

> +		return -ENOMEM;
> +	}
> +
> +	for (i = 0; i < nb_rxq; i++) {
> +		vq = dev->data->rx_queues[i];
> +		if (!vq)
> +			continue;

Put such check at the entry of this function?

> +		ret = rte_vhost_get_vhost_vring(vq->vid, (i << 1) + 1, &vring);
> +		if (ret < 0)

Does that mean we shall take care of this failure?

> +			continue;
> +		RTE_LOG(INFO, PMD, "Install intr vec for rxq%d\n", i);
> +		dev->intr_handle->intr_vec[i] = RTE_INTR_VEC_RXTX_OFFSET + i;
> +		dev->intr_handle->efds[i] = vring.kickfd;

Before use of the kickfd, we need to check the validation?

> +		count++;
> +	}
> +
> +	dev->intr_handle->nb_efd = count;
> +	dev->intr_handle->max_intr = count + 1;
> +	dev->intr_handle->type = RTE_INTR_HANDLE_VDEV;
> +
> +	return 0;
> +}
> +
> +static int
>   new_device(int vid)
>   {
>   	struct rte_eth_dev *eth_dev;
>   	struct internal_list *list;
>   	struct pmd_internal *internal;
>   	struct vhost_queue *vq;
> +	struct rte_eth_conf *dev_conf;
>   	unsigned i;
>   	char ifname[PATH_MAX];
>   #ifdef RTE_LIBRTE_VHOST_NUMA
> @@ -609,6 +726,15 @@ new_device(int vid)
>   
>   	RTE_LOG(INFO, PMD, "Vhost device %d created\n", vid);
>   
> +	dev_conf = &eth_dev->data->dev_conf;
> +
> +	if (dev_conf->intr_conf.rxq) {
> +		if (eth_vhost_install_intr(eth_dev) < 0) {
> +			RTE_LOG(INFO, PMD, "Failed to prepare intr handler.");
> +			return -1;
> +		}
> +	}
> +
>   	_rte_eth_dev_callback_process(eth_dev, RTE_ETH_EVENT_INTR_LSC, NULL);
>   
>   	return 0;
> @@ -663,6 +789,8 @@ destroy_device(int vid)
>   
>   	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);
>   }
>   
> @@ -1007,6 +1135,8 @@ 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;