Use persistent NAPI config so that NAPI IDs are not renumbered as queue
counts change.

$ sudo ethtool -l ens4  | tail -5 | egrep -i '(current|combined)'
Current hardware settings:
Combined:       4

$ ./tools/net/ynl/pyynl/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, 'type': 'tx'},
  {'id': 1, 'ifindex': 2, 'type': 'tx'},
  {'id': 2, 'ifindex': 2, 'type': 'tx'},
  {'id': 3, 'ifindex': 2, 'type': 'tx'}]

Now adjust the queue count, note that the NAPI IDs are not renumbered:

$ sudo ethtool -L ens4 combined 1
$ ./tools/net/ynl/pyynl/cli.py \
     --spec Documentation/netlink/specs/netdev.yaml \
     --dump queue-get --json='{"ifindex": 2}'
[{'id': 0, 'ifindex': 2, 'napi-id': 8193, 'type': 'rx'},
  {'id': 0, 'ifindex': 2, 'type': 'tx'}]

$ sudo ethtool -L ens4 combined 8
$ ./tools/net/ynl/pyynl/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': 4, 'ifindex': 2, 'napi-id': 8197, 'type': 'rx'},
  {'id': 5, 'ifindex': 2, 'napi-id': 8198, 'type': 'rx'},
  {'id': 6, 'ifindex': 2, 'napi-id': 8199, 'type': 'rx'},
  {'id': 7, 'ifindex': 2, 'napi-id': 8200, 'type': 'rx'},
  [...]

Signed-off-by: Joe Damato <redacted>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
---
  rfcv3:
    - Added Xuan Zhuo's Reviewed-by tag. No functional changes.

  v2:
    - Eliminate RTNL code paths using the API Jakub introduced in patch 1
      of this v2.
    - Added virtnet_napi_disable to reduce code duplication as
      suggested by Jason Wang.

  drivers/net/virtio_net.c | 5 +++--
  1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index c120cb2106c0..e0752a856adf 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c

@@ -6411,8 +6411,9 @@ static int virtnet_alloc_queues(struct virtnet_info *vi)
  	INIT_DELAYED_WORK(&vi->refill, refill_work);
  	for (i = 0; i < vi->max_queue_pairs; i++) {
  		vi->rq[i].pages = NULL;
-		netif_napi_add_weight(vi->dev, &vi->rq[i].napi, virtnet_poll,
-				      napi_weight);
+		netif_napi_add_config(vi->dev, &vi->rq[i].napi, virtnet_poll,
+				      i);
+		vi->rq[i].napi.weight = napi_weight;
  		netif_napi_add_tx_weight(vi->dev, &vi->sq[i].napi,
  					 virtnet_poll_tx,
  					 napi_tx ? napi_weight : 0);