[dpdk-users] Why kickfd from qemu is zero in qemu-dpdk vhost-user architecture?

[杨晔]

Sure.

Here is my code. In virtio_net.c of dpdk.

uint16_t
rte_vhost_dequeue_burst(int vid, uint16_t queue_id,
        struct rte_mempool *mbuf_pool, struct rte_mbuf **pkts, uint16_t count)
{
      ...
        struct virtio_net *dev;
        struct rte_mbuf *rarp_mbuf = NULL;
        struct vhost_virtqueue *vq; 
        uint32_t desc_indexes[MAX_PKT_BURST];
        uint32_t used_idx;
        uint32_t i = 0; 
        uint16_t free_entries;
        uint16_t avail_idx;

        dev = get_device(vid);
        if (!dev)
                return 0;

        if (unlikely(!is_valid_virt_queue_idx(queue_id, 1, dev->nr_vring))) {
                RTE_LOG(ERR, VHOST_DATA, "(%d) %s: invalid virtqueue idx %d.\n",
                        dev->vid, __func__, queue_id);
                return 0;
        }    

        vq = dev->virtqueue[queue_id];
     
        uint64_t val = 0; 
        int res = eventfd_read(vq->kickfd,&val);
        if(res != 0)
        {    
            RTE_LOG(INFO, VHOST_DATA, "res:(%d)\n", res);
            return 0;
        }    
        if(val > 0) 
            RTE_LOG(INFO, VHOST_DATA, "(%llu)\n", val);
        else 
            return 0;

}

I just want to use the kickfd from qemu and guest kernel, and change backend DPDK'mode from polling to interrupt.


-----Original Messages-----
From:"Li Feng" <fengli at smartx.com>
Sent Time:2018-07-15 15:57:16 (Sunday)
To: "杨晔" <yangye at ict.ac.cn>
Cc: "users at dpdk.org" <users at dpdk.org>
Subject: Re: [dpdk-users] Why kickfd from qemu is zero in qemu-dpdk vhost-user architecture?


You could paste some code here.


Is the eventfd is valid when passing to vhost?



Maybe the eventfd is bad.





Thanks,

Feng Li

  


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2018-07-15 15:27 GMT+08:00 杨晔 <yangye at ict.ac.cn>:
Hello,

I use the "vhost-user" mode in the qemu, and the backend is the dpdk-vhost.

But when I use the eventfd_read(vq->kickfd,&val) function. It always return an error, and the val has always been 0.

The kickfd is the eventfd that passing from qemu to vhost when the vring is set up and calling the vhost_user_set_vring_kick function.

It should be a none-zero value when there are packets in the sending queue.

The virtio-frontend should notify the backend then do the dequeue operation.

Does anyone know about this? I am looking forward to your reply.


Thank you.




--


Yang Ye

Network Research Center, Institute of Computing Technology, Chinese Academy of Sciences,

NO.6 Kexueyuan South Road, Zhongguancun, Haidian District, Beijing, China (100190)




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--


Yang Ye

Network Research Center, Institute of Computing Technology, Chinese Academy of Sciences,

NO.6 Kexueyuan South Road, Zhongguancun, Haidian District, Beijing, China (100190)