netdev - [PATCH iwl-next v1] ixgbe: preserve RSS indirection table across admin down/up

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Message-ID: <20250824112037.32692-1-enjuk@amazon.com>
Date: Sun, 24 Aug 2025 20:20:01 +0900
From: Kohei Enju <enjuk@...zon.com>
To: <netdev@...r.kernel.org>, <intel-wired-lan@...ts.osuosl.org>
CC: Tony Nguyen <anthony.l.nguyen@...el.com>, Przemek Kitszel
	<przemyslaw.kitszel@...el.com>, Andrew Lunn <andrew+netdev@...n.ch>, "David
 S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, "Jakub
 Kicinski" <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	<kohei.enju@...il.com>, Kohei Enju <enjuk@...zon.com>
Subject: [PATCH iwl-next v1] ixgbe: preserve RSS indirection table across admin down/up

Currently, the RSS indirection table configured by user via ethtool is
reinitialized to default values during interface resets (e.g., admin
down/up, MTU change). As for RSS hash key, commit 3dfbfc7ebb95 ("ixgbe:
Check for RSS key before setting value") made it persistent across
interface resets.

By adopting the same approach used in igc and igb drivers which
reinitializes the RSS indirection table only when the queue count
changes, let's make user configuration persistent as long as queue count
remains unchanged.

Tested on Intel Corporation 82599ES 10-Gigabit SFI/SFP+ Network
Connection.

Test:
Set custom indirection table and check the value after interface down/up

  # ethtool --set-rxfh-indir ens5 equal 2
  # ethtool --show-rxfh-indir ens5 | head -5

  RX flow hash indirection table for ens5 with 12 RX ring(s):
      0:      0     1     0     1     0     1     0     1
      8:      0     1     0     1     0     1     0     1
     16:      0     1     0     1     0     1     0     1
  # ip link set dev ens5 down && ip link set dev ens5 up

Without patch:
  # ethtool --show-rxfh-indir ens5 | head -5

  RX flow hash indirection table for ens5 with 12 RX ring(s):
      0:      0     1     2     3     4     5     6     7
      8:      8     9    10    11     0     1     2     3
     16:      4     5     6     7     8     9    10    11

With patch:
  # ethtool --show-rxfh-indir ens5 | head -5

  RX flow hash indirection table for ens5 with 12 RX ring(s):
      0:      0     1     0     1     0     1     0     1
      8:      0     1     0     1     0     1     0     1
     16:      0     1     0     1     0     1     0     1

Signed-off-by: Kohei Enju <enjuk@...zon.com>
---
 drivers/net/ethernet/intel/ixgbe/ixgbe.h      |  1 +
 drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 37 +++++++++++++------
 2 files changed, 27 insertions(+), 11 deletions(-)

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe.h b/drivers/net/ethernet/intel/ixgbe/ixgbe.h
index 14d275270123..d8b088c90b05 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe.h
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe.h
@@ -838,6 +838,7 @@ struct ixgbe_adapter {
  */
 #define IXGBE_MAX_RETA_ENTRIES 512
 	u8 rss_indir_tbl[IXGBE_MAX_RETA_ENTRIES];
+	u16 last_rss_i;
 
 #define IXGBE_RSS_KEY_SIZE     40  /* size of RSS Hash Key in bytes */
 	u32 *rss_key;
diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index 80e6a2ef1350..dc5a8373b0c3 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -4318,14 +4318,22 @@ static void ixgbe_setup_reta(struct ixgbe_adapter *adapter)
 	/* Fill out hash function seeds */
 	ixgbe_store_key(adapter);
 
-	/* Fill out redirection table */
-	memset(adapter->rss_indir_tbl, 0, sizeof(adapter->rss_indir_tbl));
+	/* Update redirection table in memory on first init or queue count
+	 * change, otherwise preserve user configurations. Then always
+	 * write to hardware.
+	 */
+	if (adapter->last_rss_i != rss_i) {
+		memset(adapter->rss_indir_tbl, 0,
+		       sizeof(adapter->rss_indir_tbl));
+
+		for (i = 0, j = 0; i < reta_entries; i++, j++) {
+			if (j == rss_i)
+				j = 0;
 
-	for (i = 0, j = 0; i < reta_entries; i++, j++) {
-		if (j == rss_i)
-			j = 0;
+			adapter->rss_indir_tbl[i] = j;
+		}
 
-		adapter->rss_indir_tbl[i] = j;
+		adapter->last_rss_i = rss_i;
 	}
 
 	ixgbe_store_reta(adapter);
@@ -4347,12 +4355,19 @@ static void ixgbe_setup_vfreta(struct ixgbe_adapter *adapter)
 					*(adapter->rss_key + i));
 	}
 
-	/* Fill out the redirection table */
-	for (i = 0, j = 0; i < 64; i++, j++) {
-		if (j == rss_i)
-			j = 0;
+	/* Update redirection table in memory on first init or queue count
+	 * change, otherwise preserve user configurations. Then always
+	 * write to hardware.
+	 */
+	if (adapter->last_rss_i != rss_i) {
+		for (i = 0, j = 0; i < 64; i++, j++) {
+			if (j == rss_i)
+				j = 0;
+
+			adapter->rss_indir_tbl[i] = j;
+		}
 
-		adapter->rss_indir_tbl[i] = j;
+		adapter->last_rss_i = rss_i;
 	}
 
 	ixgbe_store_vfreta(adapter);
-- 
2.51.0