Re: [PATCH iwl-next v5 2/2] igc: Link queues to NAPI instances

[Joe Damato <jdamato@fastly.com>]

On Tue, Oct 29, 2024 at 11:49:03AM +0200, Lifshits, Vitaly wrote:
> 
> 
> On 10/28/2024 9:52 PM, Joe Damato wrote:
> > Link queues to NAPI instances via netdev-genl API so that users can
> > query this information with netlink. Handle a few cases in the driver:
> >    1. Link/unlink the NAPIs when XDP is enabled/disabled
> >    2. Handle IGC_FLAG_QUEUE_PAIRS enabled and disabled
> > 
> > Example output when IGC_FLAG_QUEUE_PAIRS is enabled:
> > 
> > $ ./tools/net/ynl/cli.py --spec Documentation/netlink/specs/netdev.yaml \
> >                           --dump queue-get --json='{"ifindex": 2}'
> > 
> > [{'id': 0, 'ifindex': 2, 'napi-id': 8193, 'type': 'rx'},
> >   {'id': 1, 'ifindex': 2, 'napi-id': 8194, 'type': 'rx'},
> >   {'id': 2, 'ifindex': 2, 'napi-id': 8195, 'type': 'rx'},
> >   {'id': 3, 'ifindex': 2, 'napi-id': 8196, 'type': 'rx'},
> >   {'id': 0, 'ifindex': 2, 'napi-id': 8193, 'type': 'tx'},
> >   {'id': 1, 'ifindex': 2, 'napi-id': 8194, 'type': 'tx'},
> >   {'id': 2, 'ifindex': 2, 'napi-id': 8195, 'type': 'tx'},
> >   {'id': 3, 'ifindex': 2, 'napi-id': 8196, 'type': 'tx'}]
> > 
> > Since IGC_FLAG_QUEUE_PAIRS is enabled, you'll note that the same NAPI ID
> > is present for both rx and tx queues at the same index, for example
> > index 0:
> > 
> > {'id': 0, 'ifindex': 2, 'napi-id': 8193, 'type': 'rx'},
> > {'id': 0, 'ifindex': 2, 'napi-id': 8193, 'type': 'tx'},
> > 
> > To test IGC_FLAG_QUEUE_PAIRS disabled, a test system was booted using
> > the grub command line option "maxcpus=2" to force
> > igc_set_interrupt_capability to disable IGC_FLAG_QUEUE_PAIRS.
> > 
> > Example output when IGC_FLAG_QUEUE_PAIRS is disabled:
> > 
> > $ lscpu | grep "On-line CPU"
> > On-line CPU(s) list:      0,2
> > 
> > $ ethtool -l enp86s0  | tail -5
> > Current hardware settings:
> > RX:		n/a
> > TX:		n/a
> > Other:		1
> > Combined:	2
> > 
> > $ cat /proc/interrupts  | grep enp
> >   144: [...] enp86s0
> >   145: [...] enp86s0-rx-0
> >   146: [...] enp86s0-rx-1
> >   147: [...] enp86s0-tx-0
> >   148: [...] enp86s0-tx-1
> > 
> > 1 "other" IRQ, and 2 IRQs for each of RX and Tx, so we expect netlink to
> > report 4 IRQs with unique NAPI IDs:
> > 
> > $ ./tools/net/ynl/cli.py --spec Documentation/netlink/specs/netdev.yaml \
> >                           --dump napi-get --json='{"ifindex": 2}'
> > [{'id': 8196, 'ifindex': 2, 'irq': 148},
> >   {'id': 8195, 'ifindex': 2, 'irq': 147},
> >   {'id': 8194, 'ifindex': 2, 'irq': 146},
> >   {'id': 8193, 'ifindex': 2, 'irq': 145}]
> > 
> > Now we examine which queues these NAPIs are associated with, expecting
> > that since IGC_FLAG_QUEUE_PAIRS is disabled each RX and TX queue will
> > have its own NAPI instance:
> > 
> > $ ./tools/net/ynl/cli.py --spec Documentation/netlink/specs/netdev.yaml \
> >                           --dump queue-get --json='{"ifindex": 2}'
> > [{'id': 0, 'ifindex': 2, 'napi-id': 8193, 'type': 'rx'},
> >   {'id': 1, 'ifindex': 2, 'napi-id': 8194, 'type': 'rx'},
> >   {'id': 0, 'ifindex': 2, 'napi-id': 8195, 'type': 'tx'},
> >   {'id': 1, 'ifindex': 2, 'napi-id': 8196, 'type': 'tx'}]
> > 
> > Signed-off-by: Joe Damato <jdamato@fastly.com>
> > ---
> >   v5:
> >     - Rename igc_resume to __igc_do_resume and pass in a boolean
> >       "need_rtnl" to signal whether or not rtnl should be held before
> >       caling __igc_open. Call this new function from igc_runtime_resume
> >       and igc_resume passing in false (for igc_runtime_resume) and true
> >       (igc_resume), respectively. This is done to avoid reintroducing a
> >       bug fixed in commit: 6f31d6b: "igc: Refactor runtime power
> >       management flow" where rtnl is held in runtime_resume causing a
> >       deadlock.
> > 
> >   v4:
> >     - Add rtnl_lock/rtnl_unlock in two paths: igc_resume and
> >       igc_io_error_detected. The code added to the latter is inspired by
> >       a similar implementation in ixgbe's ixgbe_io_error_detected.
> > 
> >   v3:
> >     - Replace igc_unset_queue_napi with igc_set_queue_napi(adapater, i,
> >       NULL), as suggested by Vinicius Costa Gomes
> >     - Simplify implemention of igc_set_queue_napi as suggested by Kurt
> >       Kanzenbach, with a tweak to use ring->queue_index
> > 
> >   v2:
> >     - Update commit message to include tests for IGC_FLAG_QUEUE_PAIRS
> >       disabled
> >     - Refactored code to move napi queue mapping and unmapping to helper
> >       functions igc_set_queue_napi and igc_unset_queue_napi
> >     - Adjust the code to handle IGC_FLAG_QUEUE_PAIRS disabled
> >     - Call helpers to map/unmap queues to NAPIs in igc_up, __igc_open,
> >       igc_xdp_enable_pool, and igc_xdp_disable_pool
> > 
> >   drivers/net/ethernet/intel/igc/igc.h      |  2 +
> >   drivers/net/ethernet/intel/igc/igc_main.c | 52 ++++++++++++++++++++---
> >   drivers/net/ethernet/intel/igc/igc_xdp.c  |  2 +
> >   3 files changed, 49 insertions(+), 7 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/intel/igc/igc.h b/drivers/net/ethernet/intel/igc/igc.h
> > index eac0f966e0e4..b8111ad9a9a8 100644
> > --- a/drivers/net/ethernet/intel/igc/igc.h
> > +++ b/drivers/net/ethernet/intel/igc/igc.h
> > @@ -337,6 +337,8 @@ struct igc_adapter {
> >   	struct igc_led_classdev *leds;
> >   };
> > +void igc_set_queue_napi(struct igc_adapter *adapter, int q_idx,
> > +			struct napi_struct *napi);
> >   void igc_up(struct igc_adapter *adapter);
> >   void igc_down(struct igc_adapter *adapter);
> >   int igc_open(struct net_device *netdev);
> > diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
> > index 7964bbedb16c..051a0cdb1143 100644
> > --- a/drivers/net/ethernet/intel/igc/igc_main.c
> > +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> > @@ -4948,6 +4948,22 @@ static int igc_sw_init(struct igc_adapter *adapter)
> >   	return 0;
> >   }
> > +void igc_set_queue_napi(struct igc_adapter *adapter, int vector,
> > +			struct napi_struct *napi)
> > +{
> > +	struct igc_q_vector *q_vector = adapter->q_vector[vector];
> > +
> > +	if (q_vector->rx.ring)
> > +		netif_queue_set_napi(adapter->netdev,
> > +				     q_vector->rx.ring->queue_index,
> > +				     NETDEV_QUEUE_TYPE_RX, napi);
> > +
> > +	if (q_vector->tx.ring)
> > +		netif_queue_set_napi(adapter->netdev,
> > +				     q_vector->tx.ring->queue_index,
> > +				     NETDEV_QUEUE_TYPE_TX, napi);
> > +}
> > +
> >   /**
> >    * igc_up - Open the interface and prepare it to handle traffic
> >    * @adapter: board private structure
> > @@ -4955,6 +4971,7 @@ static int igc_sw_init(struct igc_adapter *adapter)
> >   void igc_up(struct igc_adapter *adapter)
> >   {
> >   	struct igc_hw *hw = &adapter->hw;
> > +	struct napi_struct *napi;
> >   	int i = 0;
> >   	/* hardware has been reset, we need to reload some things */
> > @@ -4962,8 +4979,11 @@ void igc_up(struct igc_adapter *adapter)
> >   	clear_bit(__IGC_DOWN, &adapter->state);
> > -	for (i = 0; i < adapter->num_q_vectors; i++)
> > -		napi_enable(&adapter->q_vector[i]->napi);
> > +	for (i = 0; i < adapter->num_q_vectors; i++) {
> > +		napi = &adapter->q_vector[i]->napi;
> > +		napi_enable(napi);
> > +		igc_set_queue_napi(adapter, i, napi);
> > +	}
> >   	if (adapter->msix_entries)
> >   		igc_configure_msix(adapter);
> > @@ -5192,6 +5212,7 @@ void igc_down(struct igc_adapter *adapter)
> >   	for (i = 0; i < adapter->num_q_vectors; i++) {
> >   		if (adapter->q_vector[i]) {
> >   			napi_synchronize(&adapter->q_vector[i]->napi);
> > +			igc_set_queue_napi(adapter, i, NULL);
> >   			napi_disable(&adapter->q_vector[i]->napi);
> >   		}
> >   	}
> > @@ -6021,6 +6042,7 @@ static int __igc_open(struct net_device *netdev, bool resuming)
> >   	struct igc_adapter *adapter = netdev_priv(netdev);
> >   	struct pci_dev *pdev = adapter->pdev;
> >   	struct igc_hw *hw = &adapter->hw;
> > +	struct napi_struct *napi;
> >   	int err = 0;
> >   	int i = 0;
> > @@ -6056,8 +6078,11 @@ static int __igc_open(struct net_device *netdev, bool resuming)
> >   	clear_bit(__IGC_DOWN, &adapter->state);
> > -	for (i = 0; i < adapter->num_q_vectors; i++)
> > -		napi_enable(&adapter->q_vector[i]->napi);
> > +	for (i = 0; i < adapter->num_q_vectors; i++) {
> > +		napi = &adapter->q_vector[i]->napi;
> > +		napi_enable(napi);
> > +		igc_set_queue_napi(adapter, i, napi);
> > +	}
> >   	/* Clear any pending interrupts. */
> >   	rd32(IGC_ICR);
> > @@ -7342,7 +7367,7 @@ static void igc_deliver_wake_packet(struct net_device *netdev)
> >   	netif_rx(skb);
> >   }
> > -static int igc_resume(struct device *dev)
> > +static int __igc_do_resume(struct device *dev, bool need_rtnl)
> >   {
> >   	struct pci_dev *pdev = to_pci_dev(dev);
> >   	struct net_device *netdev = pci_get_drvdata(pdev);
> > @@ -7385,7 +7410,11 @@ static int igc_resume(struct device *dev)
> >   	wr32(IGC_WUS, ~0);
> >   	if (netif_running(netdev)) {
> > +		if (need_rtnl)
> > +			rtnl_lock();
> >   		err = __igc_open(netdev, true);
> > +		if (need_rtnl)
> > +			rtnl_unlock();
> >   		if (!err)
> >   			netif_device_attach(netdev);
> >   	}
> > @@ -7393,9 +7422,14 @@ static int igc_resume(struct device *dev)
> >   	return err;
> >   }
> > +static int igc_resume(struct device *dev)
> > +{
> > +	return __igc_do_resume(dev, true);
> > +}
> > +
> >   static int igc_runtime_resume(struct device *dev)
> >   {
> > -	return igc_resume(dev);
> > +	return __igc_do_resume(dev, false);
> >   }
> >   static int igc_suspend(struct device *dev)
> > @@ -7440,14 +7474,18 @@ static pci_ers_result_t igc_io_error_detected(struct pci_dev *pdev,
> >   	struct net_device *netdev = pci_get_drvdata(pdev);
> >   	struct igc_adapter *adapter = netdev_priv(netdev);
> > +	rtnl_lock();
> >   	netif_device_detach(netdev);
> > -	if (state == pci_channel_io_perm_failure)
> > +	if (state == pci_channel_io_perm_failure) {
> > +		rtnl_unlock();
> >   		return PCI_ERS_RESULT_DISCONNECT;
> > +	}
> >   	if (netif_running(netdev))
> >   		igc_down(adapter);
> >   	pci_disable_device(pdev);
> > +	rtnl_unlock();
> >   	/* Request a slot reset. */
> >   	return PCI_ERS_RESULT_NEED_RESET;
> > diff --git a/drivers/net/ethernet/intel/igc/igc_xdp.c b/drivers/net/ethernet/intel/igc/igc_xdp.c
> > index e27af72aada8..4da633430b80 100644
> > --- a/drivers/net/ethernet/intel/igc/igc_xdp.c
> > +++ b/drivers/net/ethernet/intel/igc/igc_xdp.c
> > @@ -84,6 +84,7 @@ static int igc_xdp_enable_pool(struct igc_adapter *adapter,
> >   		napi_disable(napi);
> >   	}
> > +	igc_set_queue_napi(adapter, queue_id, NULL);
> >   	set_bit(IGC_RING_FLAG_AF_XDP_ZC, &rx_ring->flags);
> >   	set_bit(IGC_RING_FLAG_AF_XDP_ZC, &tx_ring->flags);
> > @@ -133,6 +134,7 @@ static int igc_xdp_disable_pool(struct igc_adapter *adapter, u16 queue_id)
> >   	xsk_pool_dma_unmap(pool, IGC_RX_DMA_ATTR);
> >   	clear_bit(IGC_RING_FLAG_AF_XDP_ZC, &rx_ring->flags);
> >   	clear_bit(IGC_RING_FLAG_AF_XDP_ZC, &tx_ring->flags);
> > +	igc_set_queue_napi(adapter, queue_id, napi);
> >   	if (needs_reset) {
> >   		napi_enable(napi);
> 
> I believe that this fix should work on most cases. I have some concerns that
> this solution might not be 100% robust as sometimes runtime resume may be
> triggered without the rtnl being held. For example, if it is initiated by a
> network wake event. But, for the moment I think that this appoach is good
> enough.
>
> My main comment here is the naming conventions, I prefer using the original
> parameters/function names for consistency, similarly to what was done in the
> igb driver:
> https://github.com/torvalds/linux/commit/ac8c58f5b535d6272324e2b8b4a0454781c9147e

Sorry, can you be more specific on what the naming issue is?

Do you want me to resubmit this with "__igc_do_resume" renamed to
"__igc_resume" and "bool need_rtnl" renamed to "bool rpm" or
something else?