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

Joe Damato
2025-02-18T21:13:49Z

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@linutronix.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.