[PATCH] net: virtio_net: notifications coalescing support

* [PATCH] net: virtio_net: notifications coalescing support
@ 2022-07-11 11:28 Alvaro Karsz
  2022-07-12  3:36 ` Jakub Kicinski
  0 siblings, 1 reply; 3+ messages in thread
From: Alvaro Karsz @ 2022-07-11 11:28 UTC (permalink / raw)
  To: netdev
  Cc: Alvaro Karsz, Michael S. Tsirkin, Jason Wang, David S. Miller,
	Eric Dumazet, Jakub Kicinski, Paolo Abeni

New VirtIO network feature: VIRTIO_NET_F_NOTF_COAL.

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

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

- VIRTIO_NET_CTRL_NOTF_COAL_TX_SET:
  Ask the network device to change the following parameters:
  - tx_usecs: Maximum number of usecs to delay a TX notification.
  - tx_max_packets: Maximum number of packets to send before a
    TX notification.

- VIRTIO_NET_CTRL_NOTF_COAL_RX_SET:
  Ask the network device to change the following parameters:
  - rx_usecs: Maximum number of usecs to delay a RX notification.
  - rx_max_packets: Maximum number of packets to receive before a
    RX notification.

VirtIO spec. patch:
https://lists.oasis-open.org/archives/virtio-comment/202206/msg00100.html

Signed-off-by: Alvaro Karsz <alvaro.karsz@solid-run.com>
---
 drivers/net/virtio_net.c        | 110 ++++++++++++++++++++++++++++----
 include/uapi/linux/virtio_net.h |  34 +++++++++-
 2 files changed, 130 insertions(+), 14 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 356cf8dd416..a163beeabf3 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_max_packets;
+	u32 rx_max_packets;
+
 	unsigned long guest_offloads;
 	unsigned long guest_offloads_capable;
 
@@ -2594,19 +2600,76 @@ static int virtnet_set_coalesce(struct net_device *dev,
 {
 	struct virtnet_info *vi = netdev_priv(dev);
 	int i, napi_weight;
+	struct scatterlist sgs_tx, sgs_rx;
+	struct virtio_net_ctrl_coal_tx coal_tx;
+	struct virtio_net_ctrl_coal_rx coal_rx;
+	bool update_napi,
+	notf_coal = virtio_has_feature(vi->vdev, VIRTIO_NET_F_NOTF_COAL);
+
+	/* rx_coalesce_usecs/tx_coalesce_usecs are supported only
+	 * if VIRTIO_NET_F_NOTF_COAL feature is negotiated.
+	 */
+	if (!notf_coal && (ec->rx_coalesce_usecs || ec->tx_coalesce_usecs))
+		return -EOPNOTSUPP;
+
+	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_NOTF_COAL)) {
+		coal_tx.tx_usecs = ec->tx_coalesce_usecs;
+		coal_tx.tx_max_packets = ec->tx_max_coalesced_frames;
+		sg_init_one(&sgs_tx, &coal_tx, sizeof(coal_tx));
+
+		if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_NOTF_COAL,
+					  VIRTIO_NET_CTRL_NOTF_COAL_TX_SET,
+					  &sgs_tx))
+			return -EINVAL;
+
+		/* Save parameters */
+		vi->tx_usecs = ec->tx_coalesce_usecs;
+		vi->tx_max_packets = ec->tx_max_coalesced_frames;
+
+		coal_rx.rx_usecs = ec->rx_coalesce_usecs;
+		coal_rx.rx_max_packets = ec->rx_max_coalesced_frames;
+		sg_init_one(&sgs_rx, &coal_rx, sizeof(coal_rx));
+
+		if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_NOTF_COAL,
+					  VIRTIO_NET_CTRL_NOTF_COAL_RX_SET,
+					  &sgs_rx))
+			return -EINVAL;
+
+		/* Save parameters */
+		vi->rx_usecs = ec->rx_coalesce_usecs;
+		vi->rx_max_packets = 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 notifications coalesing feature is not negotiated,
+	 * and we can't update NAPI, return an error
+	 */
+	if (!notf_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 notifications coalescing feature is not negotiated,
+				 * return an error, otherwise exit without changing
+				 * the NAPI paremeters.
+				 */
+				if (!notf_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 +2679,25 @@ 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 notf_coal = virtio_has_feature(vi->vdev, VIRTIO_NET_F_NOTF_COAL);
+
+	/* Add notifications coalescing settings */
+	if (notf_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_max_packets;
+		ec_default.rx_max_coalesced_frames = vi->rx_max_packets;
+	} else {
+		ec_default.rx_max_coalesced_frames = 1;
+	}
 
 	memcpy(ec, &ec_default, sizeof(ec_default));
 
-	if (vi->sq[0].napi.weight)
+	if (!notf_coal && vi->sq[0].napi.weight)
 		ec->tx_max_coalesced_frames = 1;
 
 	return 0;
@@ -2743,7 +2817,8 @@ 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,
@@ -3411,6 +3486,8 @@ 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_NOTF_COAL,
 			     "VIRTIO_NET_F_CTRL_VQ"))) {
 		return false;
 	}
@@ -3546,6 +3623,13 @@ 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_NOTF_COAL)) {
+		vi->rx_usecs = 0;
+		vi->tx_usecs = 0;
+		vi->tx_max_packets = 0;
+		vi->rx_max_packets = 0;
+	}
+
 	if (virtio_has_feature(vdev, VIRTIO_NET_F_HASH_REPORT))
 		vi->has_rss_hash_report = true;
 
@@ -3780,7 +3864,7 @@ 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_NOTF_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..31724f8c920 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_NOTF_COAL	53	/* Guest can handle nofitications 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 notifications coalescing.
+ *
+ * Request the device to change the notifications coalescing parameters.
+ *
+ * Available with the VIRTIO_NET_F_NOTF_COAL feature bit.
+ */
+#define VIRTIO_NET_CTRL_NOTF_COAL		6
+/*
+ * Set the tx-usecs/tx-max-packets patameters.
+ * tx-usecs - Maximum number of usecs to delay a TX notification.
+ * tx-max-packets - Maximum number of packets to send before a TX notification.
+ */
+struct virtio_net_ctrl_coal_tx {
+	__virtio32 tx_max_packets;
+	__virtio32 tx_usecs;
+};
+
+#define VIRTIO_NET_CTRL_NOTF_COAL_TX_SET		0
+
+/*
+ * Set the rx-usecs/rx-max-packets patameters.
+ * rx-usecs - Maximum number of usecs to delay a RX notification.
+ * rx-max-frames - Maximum number of packets to receive before a RX notification.
+ */
+struct virtio_net_ctrl_coal_rx {
+	__virtio32 rx_max_packets;
+	__virtio32 rx_usecs;
+};
+
+#define VIRTIO_NET_CTRL_NOTF_COAL_RX_SET		1
+
 #endif /* _UAPI_LINUX_VIRTIO_NET_H */
-- 
2.32.0


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