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

Joe Damato
2025-02-19T17:55:20Z

On Wed, Feb 19, 2025 at 08:41:01AM +0100, Kurt Kanzenbach wrote:
> On Tue Feb 18 2025, Joe Damato wrote:
> > 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?
>
> All the other instances in the driver guard the netif_running(), too.

OK, I spent a bit of time tracing through the paths in the igb
source. I think the v1 feedback I sent identified all the RTNL
paths, but:
- I am not an igb expert
- I don't have a device to test this on
- It is certainly possible I missed a path in my v1 analysis

The above said, as far as I can tell this patch seems fine, so:

Acked-by: Joe Damato <jdamato@fastly.com>