Message-ID: <d7799132-7e4a-0ac2-cbda-c919ce434fe2@intel.com>
Date: Sun, 27 Oct 2024 11:49:33 +0200
From: "Lifshits, Vitaly" <vitaly.lifshits@...el.com>
To: Joe Damato <jdamato@...tly.com>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>
CC: "Keller, Jacob E" <jacob.e.keller@...el.com>, "kurt@...utronix.de"
	<kurt@...utronix.de>, "Gomes, Vinicius" <vinicius.gomes@...el.com>, "Nguyen,
 Anthony L" <anthony.l.nguyen@...el.com>, "Kitszel, Przemyslaw"
	<przemyslaw.kitszel@...el.com>, Andrew Lunn <andrew+netdev@...n.ch>, "David
 S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, "Jakub
 Kicinski" <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, "Alexei
 Starovoitov" <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
	"Jesper Dangaard Brouer" <hawk@...nel.org>, John Fastabend
	<john.fastabend@...il.com>, "moderated list:INTEL ETHERNET DRIVERS"
	<intel-wired-lan@...ts.osuosl.org>, open list <linux-kernel@...r.kernel.org>,
	"open list:XDP (eXpress Data Path)" <bpf@...r.kernel.org>
Subject: Re: [Intel-wired-lan] [iwl-next v4 2/2] igc: Link queues to NAPI
 instances


On 10/23/2024 12:52 AM, 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@...tly.com>
> Acked-by: Vinicius Costa Gomes <vinicius.gomes@...el.com>
> ---
>   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 | 41 ++++++++++++++++++++---
>   drivers/net/ethernet/intel/igc/igc_xdp.c  |  2 ++
>   3 files changed, 40 insertions(+), 5 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..04aa216ef612 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);
> @@ -7385,7 +7410,9 @@ static int igc_resume(struct device *dev)
>   	wr32(IGC_WUS, ~0);
>   
>   	if (netif_running(netdev)) {
> +		rtnl_lock();

This change will bring back the deadlock issue that was fixed in commit:
6f31d6b: "igc: Refactor runtime power management flow".

>   		err = __igc_open(netdev, true);
> +		rtnl_unlock();
>   		if (!err)
>   			netif_device_attach(netdev);
>   	}
> @@ -7440,14 +7467,18 @@ 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);
> 



Hi Joe,


The current version will cause a regression, a possible deadlock, due to 
the addition of the rtnl_lock in igc_resume that was fixed previously.

You can refer to the following link:

https://github.com/torvalds/linux/commit/6f31d6b643a32cc126cf86093fca1ea575948bf0#diff-d5b32b873e9902b496280a5f42c246043c8f0691d8b3a6bbd56df99ce8ceb394L7190

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