Merge branch 'virtio-net-interrupt-moderation'

Heng Qi says:

====================
virtio-net: Fix and update interrupt moderation

The setting of virtio coalescing parameters involves all-queues and
per queue, so we must be careful to synchronize the two.

Regarding napi_tx switching, this patch set is not only
compatible with the previous way of using tx-frames to switch napi_tx,
but also improves the user experience when setting interrupt parameters.

This patch set has been tested and was part of the previous netdim patch
set[1] and is now being split to be rolled out in steps.

[1] https://lore.kernel.org/all/20230811065512.22190-1-hengqi@linux.alibaba.com/

---
v2->v3:
    1. Fix a tiny comment.

v1->v2:
    1. Fix some minor comments and add ack tags.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/virtio_net.c

@@ -2855,6 +2855,9 @@ static void virtnet_get_ringparam(struct net_device *dev,
 	ring->tx_pending = virtqueue_get_vring_size(vi->sq[0].vq);
 }
 
+static int virtnet_send_ctrl_coal_vq_cmd(struct virtnet_info *vi,
+					 u16 vqn, u32 max_usecs, u32 max_packets);
+
 static int virtnet_set_ringparam(struct net_device *dev,
 				 struct ethtool_ringparam *ring,
 				 struct kernel_ethtool_ringparam *kernel_ring,
@@ -2890,12 +2893,36 @@ static int virtnet_set_ringparam(struct net_device *dev,
 			err = virtnet_tx_resize(vi, sq, ring->tx_pending);
 			if (err)
 				return err;
+
+			/* Upon disabling and re-enabling a transmit virtqueue, the device must
+			 * set the coalescing parameters of the virtqueue to those configured
+			 * through the VIRTIO_NET_CTRL_NOTF_COAL_TX_SET command, or, if the driver
+			 * did not set any TX coalescing parameters, to 0.
+			 */
+			err = virtnet_send_ctrl_coal_vq_cmd(vi, txq2vq(i),
+							    vi->intr_coal_tx.max_usecs,
+							    vi->intr_coal_tx.max_packets);
+			if (err)
+				return err;
+
+			vi->sq[i].intr_coal.max_usecs = vi->intr_coal_tx.max_usecs;
+			vi->sq[i].intr_coal.max_packets = vi->intr_coal_tx.max_packets;
 		}
 
 		if (ring->rx_pending != rx_pending) {
 			err = virtnet_rx_resize(vi, rq, ring->rx_pending);
 			if (err)
 				return err;
+
+			/* The reason is same as the transmit virtqueue reset */
+			err = virtnet_send_ctrl_coal_vq_cmd(vi, rxq2vq(i),
+							    vi->intr_coal_rx.max_usecs,
+							    vi->intr_coal_rx.max_packets);
+			if (err)
+				return err;
+
+			vi->rq[i].intr_coal.max_usecs = vi->intr_coal_rx.max_usecs;
+			vi->rq[i].intr_coal.max_packets = vi->intr_coal_rx.max_packets;
 		}
 	}
 
@@ -3233,6 +3260,7 @@ static int virtnet_send_notf_coal_cmds(struct virtnet_info *vi,
 				       struct ethtool_coalesce *ec)
 {
 	struct scatterlist sgs_tx, sgs_rx;
+	int i;
 
 	vi->ctrl->coal_tx.tx_usecs = cpu_to_le32(ec->tx_coalesce_usecs);
 	vi->ctrl->coal_tx.tx_max_packets = cpu_to_le32(ec->tx_max_coalesced_frames);
@@ -3246,6 +3274,10 @@ static int virtnet_send_notf_coal_cmds(struct virtnet_info *vi,
 	/* Save parameters */
 	vi->intr_coal_tx.max_usecs = ec->tx_coalesce_usecs;
 	vi->intr_coal_tx.max_packets = ec->tx_max_coalesced_frames;
+	for (i = 0; i < vi->max_queue_pairs; i++) {
+		vi->sq[i].intr_coal.max_usecs = ec->tx_coalesce_usecs;
+		vi->sq[i].intr_coal.max_packets = ec->tx_max_coalesced_frames;
+	}
 
 	vi->ctrl->coal_rx.rx_usecs = cpu_to_le32(ec->rx_coalesce_usecs);
 	vi->ctrl->coal_rx.rx_max_packets = cpu_to_le32(ec->rx_max_coalesced_frames);
@@ -3259,6 +3291,10 @@ static int virtnet_send_notf_coal_cmds(struct virtnet_info *vi,
 	/* Save parameters */
 	vi->intr_coal_rx.max_usecs = ec->rx_coalesce_usecs;
 	vi->intr_coal_rx.max_packets = ec->rx_max_coalesced_frames;
+	for (i = 0; i < vi->max_queue_pairs; i++) {
+		vi->rq[i].intr_coal.max_usecs = ec->rx_coalesce_usecs;
+		vi->rq[i].intr_coal.max_packets = ec->rx_max_coalesced_frames;
+	}
 
 	return 0;
 }
@@ -3287,27 +3323,23 @@ static int virtnet_send_notf_coal_vq_cmds(struct virtnet_info *vi,
 {
 	int err;
 
-	if (ec->rx_coalesce_usecs || ec->rx_max_coalesced_frames) {
 	err = virtnet_send_ctrl_coal_vq_cmd(vi, rxq2vq(queue),
 					    ec->rx_coalesce_usecs,
 					    ec->rx_max_coalesced_frames);
 	if (err)
 		return err;
-		/* Save parameters */
+
 	vi->rq[queue].intr_coal.max_usecs = ec->rx_coalesce_usecs;
 	vi->rq[queue].intr_coal.max_packets = ec->rx_max_coalesced_frames;
-	}
 
-	if (ec->tx_coalesce_usecs || ec->tx_max_coalesced_frames) {
 	err = virtnet_send_ctrl_coal_vq_cmd(vi, txq2vq(queue),
 					    ec->tx_coalesce_usecs,
 					    ec->tx_max_coalesced_frames);
 	if (err)
 		return err;
-		/* Save parameters */
+
 	vi->sq[queue].intr_coal.max_usecs = ec->tx_coalesce_usecs;
 	vi->sq[queue].intr_coal.max_packets = ec->tx_max_coalesced_frames;
-	}
 
 	return 0;
 }
@@ -3315,7 +3347,7 @@ static int virtnet_send_notf_coal_vq_cmds(struct virtnet_info *vi,
 static int virtnet_coal_params_supported(struct ethtool_coalesce *ec)
 {
 	/* usecs coalescing is supported only if VIRTIO_NET_F_NOTF_COAL
-	 * feature is negotiated.
+	 * or VIRTIO_NET_F_VQ_NOTF_COAL feature is negotiated.
 	 */
 	if (ec->rx_coalesce_usecs || ec->tx_coalesce_usecs)
 		return -EOPNOTSUPP;
@@ -3453,7 +3485,7 @@ static int virtnet_get_per_queue_coalesce(struct net_device *dev,
 	} else {
 		ec->rx_max_coalesced_frames = 1;
 
-		if (vi->sq[0].napi.weight)
+		if (vi->sq[queue].napi.weight)
 			ec->tx_max_coalesced_frames = 1;
 	}
 
@@ -4442,13 +4474,6 @@ static int virtnet_probe(struct virtio_device *vdev)
 		dev->xdp_features |= NETDEV_XDP_ACT_RX_SG;
 	}
 
-	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_NOTF_COAL)) {
-		vi->intr_coal_rx.max_usecs = 0;
-		vi->intr_coal_tx.max_usecs = 0;
-		vi->intr_coal_tx.max_packets = 0;
-		vi->intr_coal_rx.max_packets = 0;
-	}
-
 	if (virtio_has_feature(vdev, VIRTIO_NET_F_HASH_REPORT))
 		vi->has_rss_hash_report = true;
 
@@ -4523,6 +4548,27 @@ static int virtnet_probe(struct virtio_device *vdev)
 	if (err)
 		goto free;
 
+	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_NOTF_COAL)) {
+		vi->intr_coal_rx.max_usecs = 0;
+		vi->intr_coal_tx.max_usecs = 0;
+		vi->intr_coal_rx.max_packets = 0;
+
+		/* Keep the default values of the coalescing parameters
+		 * aligned with the default napi_tx state.
+		 */
+		if (vi->sq[0].napi.weight)
+			vi->intr_coal_tx.max_packets = 1;
+		else
+			vi->intr_coal_tx.max_packets = 0;
+	}
+
+	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_VQ_NOTF_COAL)) {
+		/* The reason is the same as VIRTIO_NET_F_NOTF_COAL. */
+		for (i = 0; i < vi->max_queue_pairs; i++)
+			if (vi->sq[i].napi.weight)
+				vi->sq[i].intr_coal.max_packets = 1;
+	}
+
 #ifdef CONFIG_SYSFS
 	if (vi->mergeable_rx_bufs)
 		dev->sysfs_rx_queue_group = &virtio_net_mrg_rx_group;