In general, I have no objections to return 'detach' appctl command.

Comments inline.

On 26.07.2017 08:09, Darrell Ball wrote:
> Commit 5dcde09c80a8 was introduced to make detaching more
> automatic without using an additional command.
> 
> Sometimes, since commit 5dcde09c80a8, dpdk devices are
> not detached when del-port is issued; command example:
> 
> sudo ovs-vsctl del-port br0 dpdk1
> 
> This can happen when vswitchd is (re)started with an existing
> database and devices are already bound to dpdk.
> 
> A discussion is here:
> https://mail.openvswitch.org/pipermail/ovs-dev/2017-June/333462.html
> along with a possible solution.
> 
> Since we are nearing the end of a release, a safe approach is needed,
> at this time.
> One approach is to revert 5dcde09c80a8.  This patch does not do that
> but reinstates the command ovs-appctl netdev-dpdk/detach to handle
> cases when del-port will not work.
> 
> Fixes: 5dcde09c80a8 ("netdev-dpdk: Fix device leak on port deletion.")
> CC: Ilya Maximets <[email protected]>
> Signed-off-by: Darrell Ball <[email protected]>
> ---
>  Documentation/howto/dpdk.rst | 12 ++++++++++
>  lib/netdev-dpdk.c            | 52 
> +++++++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 63 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/howto/dpdk.rst b/Documentation/howto/dpdk.rst
> index af01d3e..3c198a2 100644
> --- a/Documentation/howto/dpdk.rst
> +++ b/Documentation/howto/dpdk.rst
> @@ -331,6 +331,18 @@ Detaching will be performed while processing del-port 
> command::
>  
>      $ ovs-vsctl del-port dpdkx
>  
> +Sometimes, the del-port command may not detach the device.
> +Detaching can be confirmed by the appearance of an INFO log.
> +For example::
> +
> +    Device '0000:04:00.0' has been detached
> +
> +If the log is not seen, then the port can be detached using::
> +
> +$ ovs-appctl netdev-dpdk/detach 0000:01:00.0
> +
> +Again, detaching can be confirmed by the above INFO log.
> +
>  This feature is not supported with VFIO and does not work with some NICs.

I think, we need to clarify here that attempt to detach of not detachable
device will lead to closing that device and possible inability to re-add it
back to OVS. Even if this device will be added successfully after execution
of 'ovs-vsctl add-port' it may not work properly (possible crashes or HW 
faults).

For example, 'cxgbe' DPDK driver can not be restored after the 
rte_eth_dev_close().

>  For more information please refer to the `DPDK Port Hotplug Framework
>  
> <http://dpdk.org/doc/guides/prog_guide/port_hotplug_framework.html#hotplug>`__.
> diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c
> index ea17b97..812d262 100644
> --- a/lib/netdev-dpdk.c
> +++ b/lib/netdev-dpdk.c
> @@ -1013,7 +1013,7 @@ netdev_dpdk_destruct(struct netdev *netdev)
>          if (rte_eth_dev_detach(dev->port_id, devname) < 0) {
>              VLOG_ERR("Device '%s' can not be detached", dev->devargs);
>          } else {
> -            VLOG_INFO("Device '%s' detached", devname);
> +            VLOG_INFO("Device '%s' has been detached", devname);
>          }
>      }
>  
> @@ -2449,6 +2449,53 @@ netdev_dpdk_set_admin_state(struct unixctl_conn *conn, 
> int argc,
>      unixctl_command_reply(conn, "OK");
>  }
>  
> +static void
> +netdev_dpdk_detach(struct unixctl_conn *conn, int argc OVS_UNUSED,
> +                   const char *argv[], void *aux OVS_UNUSED)
> +{
> +    int ret;
> +    char *response;
> +    uint8_t port_id;
> +    char devname[RTE_ETH_NAME_MAX_LEN];
> +    struct netdev_dpdk *dev;
> +
> +    ovs_mutex_lock(&dpdk_mutex);
> +
> +    if (!rte_eth_dev_count() || rte_eth_dev_get_port_by_name(argv[1],
> +                                                             &port_id)) {
> +        response = xasprintf("Device '%s' not found in DPDK", argv[1]);
> +        goto error;
> +    }
> +
> +    dev = netdev_dpdk_lookup_by_port_id(port_id);
> +    if (dev) {
> +        response = xasprintf("Device '%s' is being used by interface '%s'. "
> +                             "Remove it before detaching",
> +                             argv[1], netdev_get_name(&dev->up));
> +        goto error;
> +    }
> +
> +    rte_eth_dev_close(port_id);
> +
> +    ret = rte_eth_dev_detach(port_id, devname);
> +    if (ret < 0) {
> +        response = xasprintf("Device '%s' can not be detached", argv[1]);
> +        goto error;
> +    }
> +
> +    response = xasprintf("Device '%s' has been detached", argv[1]);
> +
> +    ovs_mutex_unlock(&dpdk_mutex);
> +    unixctl_command_reply(conn, response);
> +    free(response);
> +    return;
> +
> +error:
> +    ovs_mutex_unlock(&dpdk_mutex);
> +    unixctl_command_reply_error(conn, response);
> +    free(response);
> +}
> +
>  /*
>   * Set virtqueue flags so that we do not receive interrupts.
>   */
> @@ -2724,6 +2771,9 @@ netdev_dpdk_class_init(void)
>          unixctl_command_register("netdev-dpdk/set-admin-state",
>                                   "[netdev] up|down", 1, 2,
>                                   netdev_dpdk_set_admin_state, NULL);
> +        unixctl_command_register("netdev-dpdk/detach",
> +                                 "pci address of device", 1, 1,
> +                                 netdev_dpdk_detach, NULL);
>  
>          ovsthread_once_done(&once);
>      }
> 
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