Re: [dpdk-dev] [PATCH v3 3/7] ethdev: copy ethdev 'fast' API into separate structure

[Pavan Nikhilesh Bhagavatula <pbhagavatula@marvell.com>]

>
>> >Copy public function pointers (rx_pkt_burst(), etc.) and related
>> >pointers to internal data from rte_eth_dev structure into a
>> >separate flat array. That array will remain in a public header.
>> >The intention here is to make rte_eth_dev and related structures
>> >internal.
>> >That should allow future possible changes to core eth_dev
>structures
>> >to be transparent to the user and help to avoid ABI/API breakages.
>> >The plan is to keep minimal part of data from rte_eth_dev public,
>> >so we still can use inline functions for 'fast' calls
>> >(like rte_eth_rx_burst(), etc.) to avoid/minimize slowdown.
>> >
>> >Signed-off-by: Konstantin Ananyev
><konstantin.ananyev@intel.com>
>> >---
>> > lib/ethdev/ethdev_private.c  | 52
>> >++++++++++++++++++++++++++++++++++++
>> > lib/ethdev/ethdev_private.h  |  7 +++++
>> > lib/ethdev/rte_ethdev.c      | 17 ++++++++++++
>> > lib/ethdev/rte_ethdev_core.h | 45
>> >+++++++++++++++++++++++++++++++
>> > 4 files changed, 121 insertions(+)
>> >
>>
>> <snip>
>>
>> >+void
>> >+eth_dev_fp_ops_reset(struct rte_eth_fp_ops *fpo)
>> >+{
>> >+	static void *dummy_data[RTE_MAX_QUEUES_PER_PORT];
>> >+	static const struct rte_eth_fp_ops dummy_ops = {
>> >+		.rx_pkt_burst = dummy_eth_rx_burst,
>> >+		.tx_pkt_burst = dummy_eth_tx_burst,
>> >+		.rxq = {.data = dummy_data, .clbk = dummy_data,},
>> >+		.txq = {.data = dummy_data, .clbk = dummy_data,},
>> >+	};
>> >+
>> >+	*fpo = dummy_ops;
>> >+}
>> >+
>> >+void
>> >+eth_dev_fp_ops_setup(struct rte_eth_fp_ops *fpo,
>> >+		const struct rte_eth_dev *dev)
>> >+{
>> >+	fpo->rx_pkt_burst = dev->rx_pkt_burst;
>> >+	fpo->tx_pkt_burst = dev->tx_pkt_burst;
>> >+	fpo->tx_pkt_prepare = dev->tx_pkt_prepare;
>> >+	fpo->rx_queue_count = dev->rx_queue_count;
>> >+	fpo->rx_descriptor_status = dev->rx_descriptor_status;
>> >+	fpo->tx_descriptor_status = dev->tx_descriptor_status;
>> >+
>> >+	fpo->rxq.data = dev->data->rx_queues;
>> >+	fpo->rxq.clbk = (void **)(uintptr_t)dev->post_rx_burst_cbs;
>> >+
>> >+	fpo->txq.data = dev->data->tx_queues;
>> >+	fpo->txq.clbk = (void **)(uintptr_t)dev->pre_tx_burst_cbs;
>> >+}
>> >diff --git a/lib/ethdev/ethdev_private.h
>b/lib/ethdev/ethdev_private.h
>> >index 3724429577..40333e7651 100644
>> >--- a/lib/ethdev/ethdev_private.h
>> >+++ b/lib/ethdev/ethdev_private.h
>> >@@ -26,4 +26,11 @@ eth_find_device(const struct rte_eth_dev
>> >*_start, rte_eth_cmp_t cmp,
>> > /* Parse devargs value for representor parameter. */
>> > int rte_eth_devargs_parse_representor_ports(char *str, void
>*data);
>> >
>> >+/* reset eth 'fast' API to dummy values */
>> >+void eth_dev_fp_ops_reset(struct rte_eth_fp_ops *fpo);
>> >+
>> >+/* setup eth 'fast' API to ethdev values */
>> >+void eth_dev_fp_ops_setup(struct rte_eth_fp_ops *fpo,
>> >+		const struct rte_eth_dev *dev);
>> >+
>> > #endif /* _ETH_PRIVATE_H_ */
>> >diff --git a/lib/ethdev/rte_ethdev.c b/lib/ethdev/rte_ethdev.c
>> >index 424bc260fa..9fbb1bc3db 100644
>> >--- a/lib/ethdev/rte_ethdev.c
>> >+++ b/lib/ethdev/rte_ethdev.c
>> >@@ -44,6 +44,9 @@
>> > static const char *MZ_RTE_ETH_DEV_DATA = "rte_eth_dev_data";
>> > struct rte_eth_dev rte_eth_devices[RTE_MAX_ETHPORTS];
>> >
>> >+/* public 'fast' API */
>> >+struct rte_eth_fp_ops rte_eth_fp_ops[RTE_MAX_ETHPORTS];
>> >+
>> > /* spinlock for eth device callbacks */
>> > static rte_spinlock_t eth_dev_cb_lock =
>RTE_SPINLOCK_INITIALIZER;
>> >
>> >@@ -1788,6 +1791,9 @@ rte_eth_dev_start(uint16_t port_id)
>> > 		(*dev->dev_ops->link_update)(dev, 0);
>> > 	}
>> >
>> >+	/* expose selection of PMD rx/tx function */
>> >+	eth_dev_fp_ops_setup(rte_eth_fp_ops + port_id, dev);
>> >+
>>
>> Secondary process will not set these properly I believe as it might not
>> call start() if it does primary process ops will not be set.
>
>That's a very good point, have to admit - I missed that part.
>
>>
>> One simple solution is to call ops_setup() around
>rte_eth_dev_attach_secondary()
>> but if application doesn't invoke start() on Primary the ops will not be
>set for it.
>
>I think rte_eth_dev_attach_secondary() wouldn't work, as majority of
>the PMDs setup
>fast ops function pointers after it.
>From reading the code rte_eth_dev_probing_finish() seems like a good
>choice -
>as it is always the final point in device initialization for secondary
>process.

Ack, make sense to me, I did a similar thing for event device in
http://patches.dpdk.org/project/dpdk/patch/20211003082710.8398-4-pbhagavatula@marvell.com/

>
>BTW, we also need something similar at de-init phase.
>rte_eth_dev_release_port() seems like a good candidate for it.
>

Hindsight I should have added reset to rte_event_pmd_pci_remove(), I will add it in next version.

>
>>
>> > 	rte_ethdev_trace_start(port_id);
>> > 	return 0;
>> > }
>> >@@ -1810,6 +1816,9 @@ rte_eth_dev_stop(uint16_t port_id)
>> > 		return 0;
>> > 	}
>> >
>> >+	/* point rx/tx functions to dummy ones */
>> >+	eth_dev_fp_ops_reset(rte_eth_fp_ops + port_id);
>> >+
>> > 	dev->data->dev_started = 0;
>> > 	ret = (*dev->dev_ops->dev_stop)(dev);
>> > 	rte_ethdev_trace_stop(port_id, ret);
>> >2.26.3