Re: [dpdk-dev] [PATCH v3] net/tap: add queues when attaching from secondary process

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 7/20/2018 12:15 PM, Thomas Monjalon wrote:
> From: Raslan Darawsheh <rasland@mellanox.com>
> 
> In the case the device is created by the primary process,
> the secondary must request some file descriptors to attach the queues.
> The file descriptors are shared via IPC Unix socket.
> 
> Thanks to the IPC synchronization, the secondary process
> is now able to do Rx/Tx on a TAP created by the primary process.
> 
> Signed-off-by: Raslan Darawsheh <rasland@mellanox.com>
> Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
> ---
> Note: there is a bug in EAL IPC regarding fd translation.
> A fix will be sent later for EAL.
> 
> v3:
>    - split some long lines
> v2:
>    - translate file descriptors via IPC API
>    - add documentation
> ---
>  doc/guides/nics/tap.rst                |  16 +++
>  doc/guides/rel_notes/release_18_08.rst |   5 +

Needs to be 18.11 release notes now.

<...>

> @@ -1946,8 +2056,18 @@ rte_pmd_tap_probe(struct rte_vdev_device *dev)
>  			TAP_LOG(ERR, "Failed to probe %s", name);
>  			return -1;
>  		}
> -		/* TODO: request info from primary to set up Rx and Tx */
>  		eth_dev->dev_ops = &ops;
> +		eth_dev->rx_pkt_burst = pmd_rx_burst;
> +		eth_dev->tx_pkt_burst = pmd_tx_burst;
> +
> +		if (!rte_eal_primary_proc_alive(NULL)) {
> +			TAP_LOG(ERR, "Primary process is missing");
> +			return -1;
> +		}
> +		ret = tap_mp_attach_queues(name, eth_dev);
> +		if (ret != 0)
> +			return -1;
> +

Should update rte_pmd_tun_probe() too?

>  		rte_eth_dev_probing_finish(eth_dev);
>  		return 0;
>  	}
> @@ -1998,10 +2118,19 @@ rte_pmd_tap_probe(struct rte_vdev_device *dev)
>  	ret = eth_dev_tap_create(dev, tap_name, remote_iface, &user_mac,
>  		ETH_TUNTAP_TYPE_TAP);
>  
> +	/* Register IPC feed callback */
> +	ret = rte_mp_action_register(TAP_MP_KEY, tap_mp_sync_queues);
> +	if (ret < 0 && rte_errno != EEXIST) {
> +		TAP_LOG(ERR, "%s: Failed to register IPC callback: %s",
> +			tuntap_name, strerror(rte_errno));
> +		goto leave;
> +	}

This is causing an error if there are multiple tap devices, since it tries to
register multiple times.