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Date:   Thu, 12 May 2022 11:35:23 +0300
From:   Alvaro Karsz <alvaro.karsz@...id-run.com>
To:     netdev@...r.kernel.org
Cc:     rabeeh@...id-run.com, Alvaro Karsz <alvaro.karsz@...id-run.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Subject: [PATCH] net: virtio_net: support interrupt coalescing

Control a Virtio network device interrupt coalescing parameters
using the control virtqueue.

New VirtIO network feature: VIRTIO_NET_F_INTR_COAL.

A device that supports this fetature can receive
VIRTIO_NET_CTRL_INTR_COAL control commands.

* VIRTIO_NET_CTRL_INTR_COAL_USECS_SET:
	change the rx-usecs and tx-usecs parameters.

	rx-usecs - Time to delay an RX interrupt after packet arrival in
		microseconds.

	tx-usecs - Time to delay a TX interrupt after a sending a packet
		in microseconds.

* VIRTIO_NET_CTRL_INTR_COAL_FRAMES_SET:
	change the rx-max-frames and tx-max-frames parameters.

	rx-max-frames: Number of packets to delay an RX interrupt after
		packet arrival.

	tx-max-frames: Number of packets to delay a TX interrupt after
		sending a packet.

Signed-off-by: Alvaro Karsz <alvaro.karsz@...id-run.com>
---
 drivers/net/virtio_net.c        | 108 ++++++++++++++++++++++++++++----
 include/uapi/linux/virtio_net.h |  34 +++++++++-
 2 files changed, 128 insertions(+), 14 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index cbba9d2e8f3..4806c35ddd5 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -261,6 +261,12 @@ struct virtnet_info {
 	u8 duplex;
 	u32 speed;

+	/* Interrupt coalescing settings */
+	u32 tx_usecs;
+	u32 rx_usecs;
+	u32 tx_frames_max;
+	u32 rx_frames_max;
+
 	unsigned long guest_offloads;
 	unsigned long guest_offloads_capable;

@@ -2594,19 +2600,75 @@ static int virtnet_set_coalesce(struct net_device *dev,
 {
 	struct virtnet_info *vi = netdev_priv(dev);
 	int i, napi_weight;
+	struct scatterlist sgs_usecs, sgs_frames;
+	struct virtio_net_ctrl_coal_frames c_frames;
+	struct virtio_net_ctrl_coal_usec c_usecs;
+	bool update_napi,
+	intr_coal = virtio_has_feature(vi->vdev, VIRTIO_NET_F_INTR_COAL);
+
+	/* rx_coalesce_usecs/tx_coalesce_usecs are supported only
+	 * if VIRTIO_NET_F_INTR_COAL feature is set.
+	 */
+	if (!intr_coal && (ec->rx_coalesce_usecs || ec->tx_coalesce_usecs))
+		return -EOPNOTSUPP;
+
+	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_INTR_COAL)) {
+		/* Send usec command */
+		c_usecs.tx_usecs = ec->tx_coalesce_usecs;
+		c_usecs.rx_usecs = ec->rx_coalesce_usecs;
+		sg_init_one(&sgs_usecs, &c_usecs, sizeof(c_usecs));
+
+		if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_INTR_COAL,
+					  VIRTIO_NET_CTRL_INTR_COAL_USECS_SET,
+					  &sgs_usecs))
+			return -EINVAL;
+
+		/* Save parameters */
+		vi->tx_usecs = ec->tx_coalesce_usecs;
+		vi->rx_usecs = ec->rx_coalesce_usecs;
+
+		/* Send frames command */
+		c_frames.tx_frames_max = ec->tx_max_coalesced_frames;
+		c_frames.rx_frames_max = ec->rx_max_coalesced_frames;
+		sg_init_one(&sgs_frames, &c_frames, sizeof(c_frames));
+
+		if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_INTR_COAL,
+					  VIRTIO_NET_CTRL_INTR_COAL_FRAMES_SET,
+					  &sgs_frames))
+			return -EINVAL;
+
+		/* Save parameters */
+		vi->tx_frames_max = ec->tx_max_coalesced_frames;
+		vi->rx_frames_max = ec->rx_max_coalesced_frames;
+	}
+
+	/* Should we update NAPI? */
+	update_napi = ec->tx_max_coalesced_frames <= 1 &&
+			ec->rx_max_coalesced_frames == 1;

-	if (ec->tx_max_coalesced_frames > 1 ||
-	    ec->rx_max_coalesced_frames != 1)
+	/* If interrupt coalesing feature is not set, and we can't update NAPI, return an error */
+	if (!intr_coal && !update_napi)
 		return -EINVAL;

-	napi_weight = ec->tx_max_coalesced_frames ? NAPI_POLL_WEIGHT : 0;
-	if (napi_weight ^ vi->sq[0].napi.weight) {
-		if (dev->flags & IFF_UP)
-			return -EBUSY;
-		for (i = 0; i < vi->max_queue_pairs; i++)
-			vi->sq[i].napi.weight = napi_weight;
+	if (update_napi) {
+		napi_weight = ec->tx_max_coalesced_frames ? NAPI_POLL_WEIGHT : 0;
+		if (napi_weight ^ vi->sq[0].napi.weight) {
+			if (dev->flags & IFF_UP) {
+				/* If Interrupt coalescing feature is not set, return an error.
+				 * Otherwise exit without changing the NAPI paremeters
+				 */
+				if (!intr_coal)
+					return -EBUSY;
+
+				goto exit;
+			}
+
+			for (i = 0; i < vi->max_queue_pairs; i++)
+				vi->sq[i].napi.weight = napi_weight;
+		}
 	}

+exit:
 	return 0;
 }

@@ -2616,14 +2678,25 @@ static int virtnet_get_coalesce(struct net_device *dev,
 				struct netlink_ext_ack *extack)
 {
 	struct ethtool_coalesce ec_default = {
-		.cmd = ETHTOOL_GCOALESCE,
-		.rx_max_coalesced_frames = 1,
+		.cmd = ETHTOOL_GCOALESCE
 	};
+
 	struct virtnet_info *vi = netdev_priv(dev);
+	bool intr_coal = virtio_has_feature(vi->vdev, VIRTIO_NET_F_INTR_COAL);
+
+	/* Add Interrupt coalescing settings */
+	if (intr_coal) {
+		ec_default.rx_coalesce_usecs = vi->rx_usecs;
+		ec_default.tx_coalesce_usecs = vi->tx_usecs;
+		ec_default.tx_max_coalesced_frames = vi->tx_frames_max;
+		ec_default.rx_max_coalesced_frames = vi->rx_frames_max;
+	} else {
+		ec_default.rx_max_coalesced_frames = 1;
+	}

 	memcpy(ec, &ec_default, sizeof(ec_default));

-	if (vi->sq[0].napi.weight)
+	if (!intr_coal && vi->sq[0].napi.weight)
 		ec->tx_max_coalesced_frames = 1;

 	return 0;
@@ -2743,7 +2816,7 @@ static int virtnet_set_rxnfc(struct net_device *dev, struct ethtool_rxnfc *info)
 }

 static const struct ethtool_ops virtnet_ethtool_ops = {
-	.supported_coalesce_params = ETHTOOL_COALESCE_MAX_FRAMES,
+	.supported_coalesce_params = ETHTOOL_COALESCE_MAX_FRAMES | ETHTOOL_COALESCE_USECS,
 	.get_drvinfo = virtnet_get_drvinfo,
 	.get_link = ethtool_op_get_link,
 	.get_ringparam = virtnet_get_ringparam,
@@ -3423,6 +3496,8 @@ static bool virtnet_validate_features(struct virtio_device *vdev)
 	     VIRTNET_FAIL_ON(vdev, VIRTIO_NET_F_RSS,
 			     "VIRTIO_NET_F_CTRL_VQ") ||
 	     VIRTNET_FAIL_ON(vdev, VIRTIO_NET_F_HASH_REPORT,
+			     "VIRTIO_NET_F_CTRL_VQ") ||
+	     VIRTNET_FAIL_ON(vdev, VIRTIO_NET_F_INTR_COAL,
 			     "VIRTIO_NET_F_CTRL_VQ"))) {
 		return false;
 	}
@@ -3558,6 +3633,13 @@ static int virtnet_probe(struct virtio_device *vdev)
 	if (virtio_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF))
 		vi->mergeable_rx_bufs = true;

+	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_INTR_COAL)) {
+		vi->rx_usecs = 0;
+		vi->tx_usecs = 0;
+		vi->tx_frames_max = 0;
+		vi->rx_frames_max = 0;
+	}
+
 	if (virtio_has_feature(vdev, VIRTIO_NET_F_HASH_REPORT))
 		vi->has_rss_hash_report = true;

@@ -3786,7 +3868,7 @@ static struct virtio_device_id id_table[] = {
 	VIRTIO_NET_F_CTRL_MAC_ADDR, \
 	VIRTIO_NET_F_MTU, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS, \
 	VIRTIO_NET_F_SPEED_DUPLEX, VIRTIO_NET_F_STANDBY, \
-	VIRTIO_NET_F_RSS, VIRTIO_NET_F_HASH_REPORT
+	VIRTIO_NET_F_RSS, VIRTIO_NET_F_HASH_REPORT, VIRTIO_NET_F_INTR_COAL

 static unsigned int features[] = {
 	VIRTNET_FEATURES,
diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
index 3f55a4215f1..b65a4295270 100644
--- a/include/uapi/linux/virtio_net.h
+++ b/include/uapi/linux/virtio_net.h
@@ -56,7 +56,7 @@
 #define VIRTIO_NET_F_MQ	22	/* Device supports Receive Flow
 					 * Steering */
 #define VIRTIO_NET_F_CTRL_MAC_ADDR 23	/* Set MAC address */
-
+#define VIRTIO_NET_F_INTR_COAL	55	/* Guest can handle Interrupt coalescing */
 #define VIRTIO_NET_F_HASH_REPORT  57	/* Supports hash report */
 #define VIRTIO_NET_F_RSS	  60	/* Supports RSS RX steering */
 #define VIRTIO_NET_F_RSC_EXT	  61	/* extended coalescing info */
@@ -355,4 +355,36 @@ struct virtio_net_hash_config {
 #define VIRTIO_NET_CTRL_GUEST_OFFLOADS   5
 #define VIRTIO_NET_CTRL_GUEST_OFFLOADS_SET        0

+/*
+ * Control interrupt coalescing.
+ *
+ * Request the device to change the interrupt coalescing parameters.
+ *
+ * Available with the VIRTIO_NET_F_INTR_COAL feature bit.
+ */
+#define VIRTIO_NET_CTRL_INTR_COAL		6
+/*
+ * Set the rx-usecs/tx-usecs patameters.
+ * rx-usecs - Number of microseconds to delay an RX interrupt after packet arrival.
+ * tx-usecs - Number of microseconds to delay a TX interrupt after a sending a packet.
+ */
+struct virtio_net_ctrl_coal_usec {
+	__u32 tx_usecs;
+	__u32 rx_usecs;
+};
+
+#define VIRTIO_NET_CTRL_INTR_COAL_USECS_SET		0
+
+/*
+ * Set the rx-max-frames/tx-max-frames patameters.
+ * rx-max-frames - Number of packets to delay an RX interrupt after packet arrival.
+ * tx-max-frames - Number of packets to delay a TX interrupt after sending a packet.
+ */
+struct virtio_net_ctrl_coal_frames {
+	__u32 tx_frames_max;
+	__u32 rx_frames_max;
+};
+
+#define VIRTIO_NET_CTRL_INTR_COAL_FRAMES_SET		1
+
 #endif /* _UAPI_LINUX_VIRTIO_NET_H */
--
2.32.0

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