gve: Add header split data path

Add header buffers and ethtool support to enable header split via the
tcp-data-split flag in ethtool's ringparam config. A coherent dma memory
is allocated for the header buffers. There is one header buffer per ring
entry by calculating the offset to the header-buffers starting address.
The header buffer is always copied directly into the skb and payload is
always added as frags. When there is a header buffer overflow or the
header length is 0, the driver places the whole unsplit packet in frags.

When toggling header split, the driver will call gve_adjust_config to
set its queues appropriately. If header split is enabled by the user and
the max packet buffer size is no less than 4KB, driver will set the
packet buffer size as 4KB to support TCP_ZEROCOPY_RECEIVE. Otherwise the
driver will use the default 2KB as the packet buffer size.

`ethtool -G <dev> tcp-data-split on/off` is the command to toggle header
split.
`ethtool -g <dev>` will show the status of header split with the field
of `tcp-data-split`.

Co-developed-by: Ziwei Xiao <ziweixiao@google.com>
Signed-off-by: Ziwei Xiao <ziweixiao@google.com>
Signed-off-by: Jeroen de Borst <jeroendb@google.com>
Reviewed-by: Praveen Kaligineedi <pkaligineedi@google.com>
Reviewed-by: Harshitha Ramamurthy <hramamurthy@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 57 insertions, 0 deletions

diff --git a/drivers/net/ethernet/google/gve/gve_main.c b/drivers/net/ethernet/google/gve/gve_main.c
index 02d12aa50885..7b89b66adb53 100644
--- a/drivers/net/ethernet/google/gve/gve_main.c
+++ b/drivers/net/ethernet/google/gve/gve_main.c
@@ -1307,9 +1307,13 @@ static void gve_rx_get_curr_alloc_cfg(struct gve_priv *priv,
 	cfg->qcfg = &priv->rx_cfg;
 	cfg->qcfg_tx = &priv->tx_cfg;
 	cfg->raw_addressing = !gve_is_qpl(priv);
+	cfg->enable_header_split = priv->header_split_enabled;
 	cfg->qpls = priv->qpls;
 	cfg->qpl_cfg = &priv->qpl_cfg;
 	cfg->ring_size = priv->rx_desc_cnt;
+	cfg->packet_buffer_size = gve_is_gqi(priv) ?
+				  GVE_DEFAULT_RX_BUFFER_SIZE :
+				  priv->data_buffer_size_dqo;
 	cfg->rx = priv->rx;
 }
 
@@ -1448,6 +1452,9 @@ static int gve_queues_start(struct gve_priv *priv,
 	if (err)
 		goto reset;
 
+	priv->header_split_enabled = rx_alloc_cfg->enable_header_split;
+	priv->data_buffer_size_dqo = rx_alloc_cfg->packet_buffer_size;
+
 	err = gve_create_rings(priv);
 	if (err)
 		goto reset;
@@ -2059,6 +2066,56 @@ out:
 	priv->tx_timeo_cnt++;
 }
 
+u16 gve_get_pkt_buf_size(const struct gve_priv *priv, bool enable_hsplit)
+{
+	if (enable_hsplit && priv->max_rx_buffer_size >= GVE_MAX_RX_BUFFER_SIZE)
+		return GVE_MAX_RX_BUFFER_SIZE;
+	else
+		return GVE_DEFAULT_RX_BUFFER_SIZE;
+}
+
+/* header-split is not supported on non-DQO_RDA yet even if device advertises it */
+bool gve_header_split_supported(const struct gve_priv *priv)
+{
+	return priv->header_buf_size && priv->queue_format == GVE_DQO_RDA_FORMAT;
+}
+
+int gve_set_hsplit_config(struct gve_priv *priv, u8 tcp_data_split)
+{
+	struct gve_tx_alloc_rings_cfg tx_alloc_cfg = {0};
+	struct gve_rx_alloc_rings_cfg rx_alloc_cfg = {0};
+	struct gve_qpls_alloc_cfg qpls_alloc_cfg = {0};
+	bool enable_hdr_split;
+	int err = 0;
+
+	if (tcp_data_split == ETHTOOL_TCP_DATA_SPLIT_UNKNOWN)
+		return 0;
+
+	if (!gve_header_split_supported(priv)) {
+		dev_err(&priv->pdev->dev, "Header-split not supported\n");
+		return -EOPNOTSUPP;
+	}
+
+	if (tcp_data_split == ETHTOOL_TCP_DATA_SPLIT_ENABLED)
+		enable_hdr_split = true;
+	else
+		enable_hdr_split = false;
+
+	if (enable_hdr_split == priv->header_split_enabled)
+		return 0;
+
+	gve_get_curr_alloc_cfgs(priv, &qpls_alloc_cfg,
+				&tx_alloc_cfg, &rx_alloc_cfg);
+
+	rx_alloc_cfg.enable_header_split = enable_hdr_split;
+	rx_alloc_cfg.packet_buffer_size = gve_get_pkt_buf_size(priv, enable_hdr_split);
+
+	if (netif_running(priv->dev))
+		err = gve_adjust_config(priv, &qpls_alloc_cfg,
+					&tx_alloc_cfg, &rx_alloc_cfg);
+	return err;
+}
+
 static int gve_set_features(struct net_device *netdev,
 			    netdev_features_t features)
 {