[PATCH net 2/2] ionic: limit TSO segments to the Tx ring size

["Nikhil P. Rao" <nikhil.rao@amd.com>]

ionic uses one Tx descriptor per TSO segment, so a GSO skb with more
segments than the ring can hold (num_descs - 1) can never be posted.
The driver never tells the stack this limit, so such skbs are built
and handed to it instead of being segmented in software.

Advertise the ring-derived limit as tso_max_segs, so locally
generated TCP stays within it and the core's gso_max_segs check
catches larger skbs.

The core only ever lowers gso_max_segs when tso_max_segs changes, so after
the ring grows gso_max_segs stays at the old limit until the admin raises
it. The driver leaves it there: it cannot tell a value the core lowered
from one the admin set, so raising it could override the admin's choice,
and the helper that sets gso_max_segs is internal to the core.

ionic_cmb_reconfig() applies the new ring size before it allocates the
queues and restores the old one if that fails, so it updates
tso_max_segs only once the allocation has succeeded, rather than
leaving gso_max_segs lowered after a rollback.

Send a features change event after an ethtool Tx ring resize, so
stacked devices (VLAN, macvlan, bond) pick up the new tso_max_segs
instead of keeping the one copied at their creation.

The firmware-recovery replay runs without RTNL, but always with the
current ring size, so it leaves tso_max_segs and gso_max_segs untouched;
rtnetlink changes them only under RTNL.

Fixes: 0f3154e6bcb3 ("ionic: Add Tx and Rx handling")
Signed-off-by: Nikhil P. Rao <nikhil.rao@amd.com>
Reviewed-by: Brett Creeley <brett.creeley@amd.com>
---
 drivers/net/ethernet/pensando/ionic/ionic_ethtool.c | 12 +++++++++---
 drivers/net/ethernet/pensando/ionic/ionic_lif.c     | 10 +++++++---
 drivers/net/ethernet/pensando/ionic/ionic_lif.h     | 10 ++++++++++
 3 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/pensando/ionic/ionic_ethtool.c b/drivers/net/ethernet/pensando/ionic/ionic_ethtool.c
index 3518fbf5882d..556e17023320 100644
--- a/drivers/net/ethernet/pensando/ionic/ionic_ethtool.c
+++ b/drivers/net/ethernet/pensando/ionic/ionic_ethtool.c
@@ -689,6 +689,7 @@ static int ionic_set_ringparam(struct net_device *netdev,
 			       struct netlink_ext_ack *extack)
 {
 	struct ionic_lif *lif = netdev_priv(netdev);
+	unsigned int ntxq_descs = lif->ntxq_descs;
 	struct ionic_queue_params qparam;
 	int err;
 
@@ -747,11 +748,12 @@ static int ionic_set_ringparam(struct net_device *netdev,
 		netdev_info(netdev, "Changing Rx ring size from %d to %d\n",
 			    lif->nrxq_descs, ring->rx_pending);
 
-	/* if we're not running, just set the values and return */
+	/* if we're not running, just set the values */
 	if (!netif_running(lif->netdev)) {
-		lif->ntxq_descs = ring->tx_pending;
+		ionic_lif_set_ntxq_descs(lif, ring->tx_pending);
 		lif->nrxq_descs = ring->rx_pending;
-		return 0;
+		err = 0;
+		goto out;
 	}
 
 	mutex_lock(&lif->queue_lock);
@@ -760,6 +762,10 @@ static int ionic_set_ringparam(struct net_device *netdev,
 	if (err)
 		netdev_info(netdev, "Ring reconfiguration failed, changes canceled: %d\n", err);
 
+out:
+	if (lif->ntxq_descs != ntxq_descs)
+		netdev_features_change(netdev);
+
 	return err;
 }
 
diff --git a/drivers/net/ethernet/pensando/ionic/ionic_lif.c b/drivers/net/ethernet/pensando/ionic/ionic_lif.c
index 7f0da2b0defd..ce1e51f318e0 100644
--- a/drivers/net/ethernet/pensando/ionic/ionic_lif.c
+++ b/drivers/net/ethernet/pensando/ionic/ionic_lif.c
@@ -2884,6 +2884,10 @@ static int ionic_cmb_reconfig(struct ionic_lif *lif,
 			}
 		}
 
+		if (lif->ntxq_descs != start_qparams.ntxq_descs)
+			netif_set_tso_max_segs(lif->netdev,
+					       lif->ntxq_descs - 1);
+
 		err = ionic_start_queues_reconfig(lif);
 		if (err) {
 			dev_err(lif->ionic->dev,
@@ -3065,7 +3069,7 @@ int ionic_reconfigure_queues(struct ionic_lif *lif,
 
 	/* swap new desc_info and rings, keeping existing interrupt config */
 	if (tx_qcqs) {
-		lif->ntxq_descs = qparam->ntxq_descs;
+		ionic_lif_set_ntxq_descs(lif, qparam->ntxq_descs);
 		for (i = 0; i < qparam->nxqs; i++)
 			ionic_swap_queues(lif->txqcqs[i], tx_qcqs[i]);
 	}
@@ -3284,10 +3288,10 @@ int ionic_lif_alloc(struct ionic *ionic)
 	lif->index = 0;
 
 	if (is_kdump_kernel()) {
-		lif->ntxq_descs = IONIC_MIN_TXRX_DESC;
+		ionic_lif_set_ntxq_descs(lif, IONIC_MIN_TXRX_DESC);
 		lif->nrxq_descs = IONIC_MIN_TXRX_DESC;
 	} else {
-		lif->ntxq_descs = IONIC_DEF_TXRX_DESC;
+		ionic_lif_set_ntxq_descs(lif, IONIC_DEF_TXRX_DESC);
 		lif->nrxq_descs = IONIC_DEF_TXRX_DESC;
 	}
 
diff --git a/drivers/net/ethernet/pensando/ionic/ionic_lif.h b/drivers/net/ethernet/pensando/ionic/ionic_lif.h
index e790f6b9441e..14aaaeb360a2 100644
--- a/drivers/net/ethernet/pensando/ionic/ionic_lif.h
+++ b/drivers/net/ethernet/pensando/ionic/ionic_lif.h
@@ -290,6 +290,16 @@ static inline void ionic_init_queue_params(struct ionic_lif *lif,
 	qparam->cmb_rx = test_bit(IONIC_LIF_F_CMB_RX_RINGS, lif->state);
 }
 
+static inline void ionic_lif_set_ntxq_descs(struct ionic_lif *lif,
+					    unsigned int descs)
+{
+	if (descs == lif->ntxq_descs)
+		return;
+
+	lif->ntxq_descs = descs;
+	netif_set_tso_max_segs(lif->netdev, descs - 1);
+}
+
 static inline void ionic_set_queue_params(struct ionic_lif *lif,
 					  struct ionic_queue_params *qparam)
 {

-- 
2.43.0