netdev - Re: [PATCH iwl-next v2 2/4] igb: Link queues to NAPI instances

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Message-ID: <Z7T4Cpv80pWF45tc@LQ3V64L9R2>
Date: Tue, 18 Feb 2025 16:13:46 -0500
From: Joe Damato <jdamato@...tly.com>
To: Kurt Kanzenbach <kurt@...utronix.de>
Cc: Tony Nguyen <anthony.l.nguyen@...el.com>,
	Przemek Kitszel <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>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Gerhard Engleder <gerhard@...leder-embedded.com>,
	intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org
Subject: Re: [PATCH iwl-next v2 2/4] igb: Link queues to NAPI instances

On Mon, Feb 17, 2025 at 12:31:22PM +0100, Kurt Kanzenbach wrote:
> Link queues to NAPI instances via netdev-genl API. This is required to use
> XDP/ZC busy polling. See commit 5ef44b3cb43b ("xsk: Bring back busy polling
> support") for details.
> 
> This also allows users to query the info with netlink:
> 
> |$ ./tools/net/ynl/pyynl/cli.py --spec Documentation/netlink/specs/netdev.yaml \
> |                               --dump queue-get --json='{"ifindex": 2}'
> |[{'id': 0, 'ifindex': 2, 'napi-id': 8201, 'type': 'rx'},
> | {'id': 1, 'ifindex': 2, 'napi-id': 8202, 'type': 'rx'},
> | {'id': 2, 'ifindex': 2, 'napi-id': 8203, 'type': 'rx'},
> | {'id': 3, 'ifindex': 2, 'napi-id': 8204, 'type': 'rx'},
> | {'id': 0, 'ifindex': 2, 'napi-id': 8201, 'type': 'tx'},
> | {'id': 1, 'ifindex': 2, 'napi-id': 8202, 'type': 'tx'},
> | {'id': 2, 'ifindex': 2, 'napi-id': 8203, 'type': 'tx'},
> | {'id': 3, 'ifindex': 2, 'napi-id': 8204, 'type': 'tx'}]
> 
> Add rtnl locking to PCI error handlers, because netif_queue_set_napi()
> requires the lock held.
> 
> While at __igb_open() use RCT coding style.
> 
> Signed-off-by: Kurt Kanzenbach <kurt@...utronix.de>
> ---
>  drivers/net/ethernet/intel/igb/igb.h      |  2 ++
>  drivers/net/ethernet/intel/igb/igb_main.c | 43 +++++++++++++++++++++++++++----
>  drivers/net/ethernet/intel/igb/igb_xsk.c  |  2 ++
>  3 files changed, 42 insertions(+), 5 deletions(-)

[...]

> @@ -9737,16 +9765,21 @@ static void igb_io_resume(struct pci_dev *pdev)
>  	struct net_device *netdev = pci_get_drvdata(pdev);
>  	struct igb_adapter *adapter = netdev_priv(netdev);
>  
> +	rtnl_lock();
>  	if (netif_running(netdev)) {
>  		if (!test_bit(__IGB_DOWN, &adapter->state)) {
>  			dev_dbg(&pdev->dev, "Resuming from non-fatal error, do nothing.\n");
> +			rtnl_unlock();
>  			return;
>  		}
> +
>  		if (igb_up(adapter)) {
>  			dev_err(&pdev->dev, "igb_up failed after reset\n");
> +			rtnl_unlock();
>  			return;
>  		}
>  	}
> +	rtnl_unlock();

Does RTNL need to be held when calling netif_running()? If not, you
could probably reduce the size of the section under the lock a bit?

Otherwise, the commit looks OK to me, but I am not an IGB expert and
it is possible there is an RTNL path I missed in my review of the
previous series.