Re: [PATCH v2 2/3] net/mlx5: fix link status behavior

[Yongseok Koh <yskoh@mellanox.com>]

> On Mar 12, 2018, at 6:43 AM, Nelio Laranjeiro <nelio.laranjeiro@6wind.com> wrote:
> 
> This behavior is mixed between what should be handled by the application
> and what is under PMD responsibility.
> 
> According to DPDK API:
> - link_update() should only query the link status [1]
> - link_set_{up,down}() should only set the link to the according status [1]
> - dev_{start,stop}() should enable/disable traffic reception/emission [2]
> 
> On this PMD, the link status is retrieved from the net device associated
> owned by the Linux Kernel, it does not means that even when this interface
> is down, the PMD cannot send/receive traffic from the NIC those two
> information are unrelated, until the physical port is active and has a
> link, the PMD can receive/send traffic on the wire.
> 
> According to DPDK API, calling the rte_eth_dev_start() even when the Linux
> interface link is down is then possible and allowed, as the traffic will
> flow between the DPDK application and the Physical port.
> 
> This also means that a synchronisation between the Linux interface and the
> DPDK application remains under the DPDK application responsibility.
> 
> To handle such synchronisation the application should behave as the
> following scheme, to start:
> 
> rte_eth_get_link(port_id, &link);
> if (link.link_status == ETH_DOWN)
> 	rte_eth_dev_set_link_up(port_id);
> rte_eth_dev_start(port_id);
> 
> Taking in account the possible returned values fro each function.
> 
> and to stop:
> 
> rte_eth_dev_stop(port_id);
> rte_eth_dev_set_link_down(port_id);
> 
> The application should also set the LSC interrupt callbacks to catch and
> behave accordingly when the administrator set the Linux device down/up.
> The same callbacks are called when the link on the medium falls/raise.
> 
> Fixes: c7bf62255edf ("net/mlx5: fix handling link status event")
> Fixes: e313ef4c2fe8 ("net/mlx5: fix link state on device start")
> Cc: yskoh@mellanox.com
> Cc: shahafs@mellanox.com
> Cc: stable@dpdk.org
> 
> [1] https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdpdk.org%2Fbrowse%2Fdpdk%2Ftree%2Flib%2Flibrte_ether%2Frte_ethdev_core.h&data=02%7C01%7Cyskoh%40mellanox.com%7Cf3d27421af9541c0d74608d5881f67af%7Ca652971c7d2e4d9ba6a4d149256f461b%7C0%7C0%7C636564590830553144&sdata=dn%2BQOq9IG2O4eYC7aSAMjvQ%2BT9rkVW%2BRo7t9RxLODTk%3D&reserved=0
> [2] https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdpdk.org%2Fbrowse%2Fdpdk%2Ftree%2Flib%2Flibrte_ether%2Frte_ethdev.h%23n1677&data=02%7C01%7Cyskoh%40mellanox.com%7Cf3d27421af9541c0d74608d5881f67af%7Ca652971c7d2e4d9ba6a4d149256f461b%7C0%7C0%7C636564590830553144&sdata=2zY%2F9gpIRcjz1mo4442u9uHTJPj5GVRftxHW8oVi6Ug%3D&reserved=0
> 
> Signed-off-by: Nelio Laranjeiro <nelio.laranjeiro@6wind.com>
> Acked-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>
> ---
Acked-by: Yongseok Koh <yskoh@mellanox.com>
 
Thanks