[dpdk-dev] [RFC] ether: support deferred queue setup

[Andrew Rybchenko]

On 01/15/2018 04:57 AM, Qi Zhang wrote:
> According to exist implementation, rte_eth_[rx|tx]_queue_setup will
> always return fail if device is already started(rte_eth_dev_start).
>
> This can't satisfied the usage when application want to deferred setup
> part of the queues while keep traffic running on those queues already
> be setup.
>
> example:
> rte_eth_dev_config(nb_rxq = 2, nb_txq =2)
> rte_eth_rx_queue_setup(idx = 0 ...)
> rte_eth_rx_queue_setup(idx = 0 ...)
> rte_eth_dev_start(...) /* [rx|tx]_burst is ready to start on queue 0 */
> rte_eth_rx_queue_setup(idx=1 ...) /* fail*/
>
> Basically this is not a general hardware limitation, because for NIC like
> i40e, ixgbe, it is not necessary to stop the whole device before configure
> a fresh queue or reconfigure an exist queue with traffic on it.
>
> The patch add new eth_dev_ops: [rx|tx]_queue_hot_[setup|release] and
> internal logic of rte_eth_[rx|tx]_queue_setup is changed, so application
> is allowed to setup queue after device start if the driver is implemented
> properly.

I see no point to introduce a new eth_dev_ops. It is possible to simply
allow setup/release operations when the device is started.
If it is desirable to make it controllable and have checks in generic code,
it is possible to have capability bits in dev_info to say that device
supports hot setup/release of Tx/Rx queues.

> The typical implementation of [rx|tx]_queue_hot_setup could be:
> 1. do the same thing in [rx|tx]_queue_setup.
> 2. perform per queue start logic from [rx|tx]_queue_start.
>
> The typical implementation of [rx|tx]_queue_hot_release could be:
> 1. perform per queue stop logic from [rx|tx]_queue_stop.
> 2. do the same thing in [rx|tx]_queue_release.
>
> Signed-off-by: Qi Zhang <qi.z.zhang at intel.com>
> ---
>   lib/librte_ether/rte_ethdev.c | 54 ++++++++++++++++++++++++-------------------
>   lib/librte_ether/rte_ethdev.h |  8 +++++++
>   2 files changed, 38 insertions(+), 24 deletions(-)

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