Re: [dpdk-dev] [PATCH v3 3/3] net/vhost: fix interrupt mode

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

On 7/29/20 11:20 AM, Maxime Coquelin wrote:
> At .new_device() time, only the first vring pair is
> now ready, other vrings are consfigured later.
> 
> Problem is that when application will setup and enable
> interrupts, only the first queue pair Rx interrupt will
> be enabled.
> 
> This patches fixes the issue by setting the number of
> max interrupts to the number of Rx queues that will be
> later initialized. Then, as soon as a Rx vring is ready
> and interrupt enabled by the application, it removes the
> corresponding uninitialized epoll event, and install a
> new one with the valid FD.
> 
> Fixes: 604052ae5395 ("net/vhost: support queue update")
> 
> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> ---
>  drivers/net/vhost/rte_eth_vhost.c | 75 +++++++++++++++++++++++++++----
>  1 file changed, 66 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/net/vhost/rte_eth_vhost.c b/drivers/net/vhost/rte_eth_vhost.c
> index 951929c663..237785dd66 100644
> --- a/drivers/net/vhost/rte_eth_vhost.c
> +++ b/drivers/net/vhost/rte_eth_vhost.c
> @@ -5,6 +5,7 @@
>  #include <unistd.h>
>  #include <pthread.h>
>  #include <stdbool.h>
> +#include <sys/epoll.h>
>  
>  #include <rte_mbuf.h>
>  #include <rte_ethdev_driver.h>
> @@ -95,6 +96,8 @@ struct vhost_queue {
>  	uint16_t port;
>  	uint16_t virtqueue_id;
>  	struct vhost_stats stats;
> +	int intr_enable;
> +	rte_spinlock_t intr_lock;
>  };
>  
>  struct pmd_internal {
> @@ -524,6 +527,45 @@ find_internal_resource(char *ifname)
>  	return list;
>  }
>  
> +static int
> +eth_vhost_update_intr(struct rte_eth_dev *eth_dev, uint16_t rxq_idx)
> +{
> +	struct rte_intr_handle *handle = eth_dev->intr_handle;
> +	struct rte_epoll_event rev;
> +	int epfd, ret;
> +

Chenbo reported that we can have a NULL pointer dereference on handle
when using Virtio-user on the other end and quitting.



> +	if (handle->efds[rxq_idx] == handle->elist[rxq_idx].fd)
> +		return 0;
> +
> +	VHOST_LOG(INFO, "kickfd for rxq-%d was changed, updating handler.\n",
> +			rxq_idx);
> +
> +	/*
> +	 * First remove invalid epoll event, and then isntall
> +	 * the new one. May be solved with a proper API in the
> +	 * future.
> +	 */
> +	epfd = handle->elist[rxq_idx].epfd;
> +	rev = handle->elist[rxq_idx];
> +	ret = rte_epoll_ctl(epfd, EPOLL_CTL_DEL, rev.fd,
> +			&handle->elist[rxq_idx]);
> +	if (ret) {
> +		VHOST_LOG(ERR, "Delete epoll event failed.\n");
> +		return ret;
> +	}
> +
> +	rev.fd = handle->efds[rxq_idx];
> +	handle->elist[rxq_idx] = rev;
> +	ret = rte_epoll_ctl(epfd, EPOLL_CTL_ADD, rev.fd,
> +			&handle->elist[rxq_idx]);
> +	if (ret) {
> +		VHOST_LOG(ERR, "Add epoll event failed.\n");
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
>  static int
>  eth_rxq_intr_enable(struct rte_eth_dev *dev, uint16_t qid)
>  {
> @@ -537,6 +579,11 @@ eth_rxq_intr_enable(struct rte_eth_dev *dev, uint16_t qid)
>  		return -1;
>  	}
>  
> +	rte_spinlock_lock(&vq->intr_lock);
> +	vq->intr_enable = 1;
> +	ret = eth_vhost_update_intr(dev, qid);
> +	rte_spinlock_unlock(&vq->intr_lock);
> +

I missed to check ret value here, will add it in v4.

>  	ret = rte_vhost_get_vhost_vring(vq->vid, (qid << 1) + 1, &vring);
>  	if (ret < 0) {
>  		VHOST_LOG(ERR, "Failed to get rxq%d's vring\n", qid);