netdev - [PATCH net-next 4/4] virtio_net: Remove rtnl lock protection of command buffers

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Message-ID: <20240325214912.323749-5-danielj@nvidia.com>
Date: Mon, 25 Mar 2024 16:49:11 -0500
From: Daniel Jurgens <danielj@...dia.com>
To: <netdev@...r.kernel.org>
CC: <mst@...hat.com>, <jasowang@...hat.com>, <xuanzhuo@...ux.alibaba.com>,
	<virtualization@...ts.linux.dev>, <davem@...emloft.net>,
	<edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>,
	<jiri@...dia.com>, Daniel Jurgens <danielj@...dia.com>
Subject: [PATCH net-next 4/4] virtio_net: Remove rtnl lock protection of command buffers

The rtnl lock is no longer needed to protect the control buffer and
command VQ.

Signed-off-by: Daniel Jurgens <danielj@...dia.com>
Reviewed-by: Jiri Pirko <jiri@...dia.com>
---
 drivers/net/virtio_net.c | 27 +++++----------------------
 1 file changed, 5 insertions(+), 22 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 41f8dc16ff38..d09ea20b16be 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -2639,14 +2639,12 @@ static void virtnet_stats(struct net_device *dev,
 
 static void virtnet_ack_link_announce(struct virtnet_info *vi)
 {
-	rtnl_lock();
 	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_ANNOUNCE,
 				  VIRTIO_NET_CTRL_ANNOUNCE_ACK, NULL))
 		dev_warn(&vi->dev->dev, "Failed to ack link announce.\n");
-	rtnl_unlock();
 }
 
-static int _virtnet_set_queues(struct virtnet_info *vi, u16 queue_pairs)
+static int virtnet_set_queues(struct virtnet_info *vi, u16 queue_pairs)
 {
 	struct virtio_net_ctrl_mq *mq __free(kfree) = NULL;
 	struct scatterlist sg;
@@ -2677,16 +2675,6 @@ static int _virtnet_set_queues(struct virtnet_info *vi, u16 queue_pairs)
 	return 0;
 }
 
-static int virtnet_set_queues(struct virtnet_info *vi, u16 queue_pairs)
-{
-	int err;
-
-	rtnl_lock();
-	err = _virtnet_set_queues(vi, queue_pairs);
-	rtnl_unlock();
-	return err;
-}
-
 static int virtnet_close(struct net_device *dev)
 {
 	struct virtnet_info *vi = netdev_priv(dev);
@@ -3268,7 +3256,7 @@ static int virtnet_set_channels(struct net_device *dev,
 		return -EINVAL;
 
 	cpus_read_lock();
-	err = _virtnet_set_queues(vi, queue_pairs);
+	err = virtnet_set_queues(vi, queue_pairs);
 	if (err) {
 		cpus_read_unlock();
 		goto err;
@@ -3558,14 +3546,11 @@ static void virtnet_rx_dim_work(struct work_struct *work)
 	struct dim_cq_moder update_moder;
 	int i, qnum, err;
 
-	if (!rtnl_trylock())
-		return;
-
 	/* Each rxq's work is queued by "net_dim()->schedule_work()"
 	 * in response to NAPI traffic changes. Note that dim->profile_ix
 	 * for each rxq is updated prior to the queuing action.
 	 * So we only need to traverse and update profiles for all rxqs
-	 * in the work which is holding rtnl_lock.
+	 * in the work.
 	 */
 	for (i = 0; i < vi->curr_queue_pairs; i++) {
 		rq = &vi->rq[i];
@@ -3587,8 +3572,6 @@ static void virtnet_rx_dim_work(struct work_struct *work)
 			dim->state = DIM_START_MEASURE;
 		}
 	}
-
-	rtnl_unlock();
 }
 
 static int virtnet_coal_params_supported(struct ethtool_coalesce *ec)
@@ -4036,7 +4019,7 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog,
 		synchronize_net();
 	}
 
-	err = _virtnet_set_queues(vi, curr_qp + xdp_qp);
+	err = virtnet_set_queues(vi, curr_qp + xdp_qp);
 	if (err)
 		goto err;
 	netif_set_real_num_rx_queues(dev, curr_qp + xdp_qp);
@@ -4852,7 +4835,7 @@ static int virtnet_probe(struct virtio_device *vdev)
 
 	virtio_device_ready(vdev);
 
-	_virtnet_set_queues(vi, vi->curr_queue_pairs);
+	virtnet_set_queues(vi, vi->curr_queue_pairs);
 
 	/* a random MAC address has been assigned, notify the device.
 	 * We don't fail probe if VIRTIO_NET_F_CTRL_MAC_ADDR is not there
-- 
2.42.0