kernel/files/2102-gve-Add-ethtool-support-for-changing-ring-size.patch

From: Joshua Washington <joshwash@google.com>
Date: Fri, 5 Jun 2026 00:00:01 +0000
Subject: gve: Add ethtool support for changing ring size

Add ethtool -G (set_ringparam) support so the TX/RX ring sizes can
actually be changed within the bounds reported by the device in the
"modify ring" device option.

Requested ring sizes are validated against the device-provided minimums
and maximums and must be a power of two. Changing the ring size tears the
device down, applies the new descriptor counts, and brings it back up.

[Jonathan Wright: backported the upstream modifiable-ring-size support to
 this kernel's gve, using the RHEL 10 / AlmaLinux 10 gve driver
 (kernel 6.12.0-211.7.1.el10_2) as the reference. Adaptations: upstream's
 gve_adjust_ring_sizes() reconfigures via gve_get_curr_alloc_cfgs() /
 gve_adjust_config(), which do not exist in this tree (it predates the
 gve_{tx,rx}_alloc_rings_cfg / queues_mem_alloc refactor). Instead
 gve_adjust_ring_sizes() lives in gve_main.c and follows the existing
 gve_adjust_queues() pattern used by this tree for ethtool -L: teardown
 with gve_close(), set the new descriptor counts, then gve_open(), which
 rebuilds the rings and re-sizes the QPLs from the new ring size via
 gve_update_num_qpl_pages() (1106). It is declared in gve.h because
 gve_close()/gve_open() are static to gve_main.c. Upstream's
 gve_set_ringparam() also handles header-split/tcp_data_split; that
 feature does not exist in this tree, so only the ring-size logic is
 carried over.]
Signed-off-by: Jonathan Wright <jonathan@almalinux.org>
---
diff --git a/drivers/net/ethernet/google/gve/gve.h b/drivers/net/ethernet/google/gve/gve.h
index a3c1caa..acac856 100644
--- a/drivers/net/ethernet/google/gve/gve.h
+++ b/drivers/net/ethernet/google/gve/gve.h
@@ -1074,6 +1074,9 @@ int gve_reset(struct gve_priv *priv, bool attempt_teardown);
 int gve_adjust_queues(struct gve_priv *priv,
 		      struct gve_queue_config new_rx_config,
 		      struct gve_queue_config new_tx_config);
+int gve_adjust_ring_sizes(struct gve_priv *priv,
+			  u16 new_tx_desc_cnt,
+			  u16 new_rx_desc_cnt);
 /* report stats handling */
 void gve_handle_report_stats(struct gve_priv *priv);
 /* exported by ethtool.c */
diff --git a/drivers/net/ethernet/google/gve/gve_ethtool.c b/drivers/net/ethernet/google/gve/gve_ethtool.c
index fb7b477..a8822c9 100644
--- a/drivers/net/ethernet/google/gve/gve_ethtool.c
+++ b/drivers/net/ethernet/google/gve/gve_ethtool.c
@@ -6,6 +6,7 @@
 
 #include <linux/ethtool.h>
 #include <linux/rtnetlink.h>
+#include <linux/log2.h>
 #include "gve.h"
 #include "gve_adminq.h"
 #include "gve_dqo.h"
@@ -482,6 +483,50 @@ static void gve_get_ringparam(struct net_device *netdev,
 	cmd->tx_pending = priv->tx_desc_cnt;
 }
 
+static int gve_validate_req_ring_size(struct gve_priv *priv, u16 new_tx_desc_cnt,
+				      u16 new_rx_desc_cnt)
+{
+	/* check for valid range */
+	if (new_tx_desc_cnt < priv->min_tx_desc_cnt ||
+	    new_tx_desc_cnt > priv->max_tx_desc_cnt ||
+	    new_rx_desc_cnt < priv->min_rx_desc_cnt ||
+	    new_rx_desc_cnt > priv->max_rx_desc_cnt) {
+		dev_err(&priv->pdev->dev, "Requested descriptor count out of range\n");
+		return -EINVAL;
+	}
+
+	if (!is_power_of_2(new_tx_desc_cnt) || !is_power_of_2(new_rx_desc_cnt)) {
+		dev_err(&priv->pdev->dev, "Requested descriptor count has to be a power of 2\n");
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static int gve_set_ringparam(struct net_device *netdev,
+			     struct ethtool_ringparam *cmd,
+			     struct kernel_ethtool_ringparam *kernel_cmd,
+			     struct netlink_ext_ack *extack)
+{
+	struct gve_priv *priv = netdev_priv(netdev);
+	u16 new_tx_cnt, new_rx_cnt;
+
+	if (cmd->tx_pending == priv->tx_desc_cnt && cmd->rx_pending == priv->rx_desc_cnt)
+		return 0;
+
+	if (!priv->modify_ring_size_enabled) {
+		dev_err(&priv->pdev->dev, "Modify ring size is not supported.\n");
+		return -EOPNOTSUPP;
+	}
+
+	new_tx_cnt = cmd->tx_pending;
+	new_rx_cnt = cmd->rx_pending;
+
+	if (gve_validate_req_ring_size(priv, new_tx_cnt, new_rx_cnt))
+		return -EINVAL;
+
+	return gve_adjust_ring_sizes(priv, new_tx_cnt, new_rx_cnt);
+}
+
 static int gve_user_reset(struct net_device *netdev, u32 *flags)
 {
 	struct gve_priv *priv = netdev_priv(netdev);
@@ -667,6 +712,7 @@ const struct ethtool_ops gve_ethtool_ops = {
 	.get_coalesce = gve_get_coalesce,
 	.set_coalesce = gve_set_coalesce,
 	.get_ringparam = gve_get_ringparam,
+	.set_ringparam = gve_set_ringparam,
 	.reset = gve_user_reset,
 	.get_tunable = gve_get_tunable,
 	.set_tunable = gve_set_tunable,
diff --git a/drivers/net/ethernet/google/gve/gve_main.c b/drivers/net/ethernet/google/gve/gve_main.c
index a21df52..e939750 100644
--- a/drivers/net/ethernet/google/gve/gve_main.c
+++ b/drivers/net/ethernet/google/gve/gve_main.c
@@ -1780,6 +1780,44 @@ err:
 	return err;
 }
 
+int gve_adjust_ring_sizes(struct gve_priv *priv,
+			  u16 new_tx_desc_cnt,
+			  u16 new_rx_desc_cnt)
+{
+	int err;
+
+	if (netif_carrier_ok(priv->dev)) {
+		/* To make this process as simple as possible we teardown the
+		 * device, set the new ring sizes, and then bring the device
+		 * up again.
+		 */
+		err = gve_close(priv->dev);
+		/* we have already tried to reset in close,
+		 * just fail at this point
+		 */
+		if (err)
+			return err;
+		priv->tx_desc_cnt = new_tx_desc_cnt;
+		priv->rx_desc_cnt = new_rx_desc_cnt;
+
+		err = gve_open(priv->dev);
+		if (err)
+			goto err;
+
+		return 0;
+	}
+	/* Set the ring sizes for the next up. */
+	priv->tx_desc_cnt = new_tx_desc_cnt;
+	priv->rx_desc_cnt = new_rx_desc_cnt;
+
+	return 0;
+err:
+	netif_err(priv, drv, priv->dev,
+		  "Adjust ring sizes failed! !!! DISABLING ALL QUEUES !!!\n");
+	gve_turndown(priv);
+	return err;
+}
+
 static void gve_turndown(struct gve_priv *priv)
 {
 	int idx;
--
2.43.0