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

["Xia, Chenbo" <chenbo.xia@intel.com>]

Hi Maxime,

> -----Original Message-----
> From: Maxime Coquelin <maxime.coquelin@redhat.com>
> Sent: Wednesday, July 29, 2020 8:54 PM
> To: dev@dpdk.org; matan@mellanox.com; Xia, Chenbo
> <chenbo.xia@intel.com>; Liu, Yong <yong.liu@intel.com>; Wang, Yinan
> <yinan.wang@intel.com>
> Cc: thomas@monjalon.net; Yigit, Ferruh <ferruh.yigit@intel.com>;
> david.marchand@redhat.com
> Subject: Re: [PATCH v3 3/3] net/vhost: fix interrupt mode
> 
> 
> 
> 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.

To clarity the root cause, it's because 'destroy_device' calls 'eth_vhost_uninstall_intr'
when connection lost but l3fwd-power APP are still enabling intr.

Thanks,
Chenbo

> 
> 
> 
> > +	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);