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

["Chen, Junjie J" <junjie.j.chen@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.
Will do.
> 
> > +	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.
Will do.
> 
> > +
> > +	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.
So, do you want to change this in this patch? Or in other separated one?
> 
> > +
> > +	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.
Will do.
> 
> > +		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?

For above two checks, I had a fix to check overall queue setup in patch: https://dpdk.org/dev/patchwork/patch/36766/ recently.
So I would like to put install_intr function into queue_setup helper function in patch 36766, and for internal vq, vring, and kickfd check of install_intr, I'd like to skip setup if check fail. How do you think? 

> 
> > +			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?
Will do.
> 
> > +		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;