Message-ID: <20251027201351.GA8995@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net>
Date: Mon, 27 Oct 2025 13:13:51 -0700
From: Dipayaan Roy <dipayanroy@...ux.microsoft.com>
To: kys@...rosoft.com, haiyangz@...rosoft.com, wei.liu@...nel.org,
	decui@...rosoft.com, andrew+netdev@...n.ch, davem@...emloft.net,
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
	longli@...rosoft.com, kotaranov@...rosoft.com, horms@...nel.org,
	shradhagupta@...ux.microsoft.com, ssengar@...ux.microsoft.com,
	ernis@...ux.microsoft.com, shirazsaleem@...rosoft.com,
	linux-hyperv@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org,
	dipayanroy@...rosoft.com
Subject: [PATCH net-next v2] net: mana: Implement ndo_tx_timeout and
 serialize queue resets per port.

Implement .ndo_tx_timeout for MANA so any stalled TX queue can be detected
and a device-controlled port reset for all queues can be scheduled to a
ordered workqueue. The reset for all queues on stall detection is
recomended by hardware team.

The change introduces a single ordered workqueue
("mana_per_port_queue_reset_wq") with WQ_UNBOUND | WQ_MEM_RECLAIM and
queues exactly one work_struct per port onto it. This achieves:

  * Global FIFO across all port reset requests (alloc_ordered_workqueue).
  * Natural per-port de-duplication: the same work_struct cannot be
    queued twice while pending/running.
  * Avoids hogging a per-CPU kworker for long, may-sleep reset paths
    (WQ_UNBOUND).
  * Guarantees forward progress during memory pressure
    (WQ_MEM_RECLAIM rescuer).

Reviewed-by: Haiyang Zhang <haiyangz@...rosoft.com>
Signed-off-by: Dipayaan Roy <dipayanroy@...ux.microsoft.com>
---
Changes in v2:
  - Fixed cosmetic changes.
---
 drivers/net/ethernet/microsoft/mana/mana_en.c | 82 +++++++++++++++++++
 include/net/mana/gdma.h                       |  6 +-
 include/net/mana/mana.h                       | 15 ++++
 3 files changed, 102 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
index f4fc86f20213..05b7046ae3b5 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_en.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
@@ -258,6 +258,45 @@ static int mana_get_gso_hs(struct sk_buff *skb)
 	return gso_hs;
 }
 
+static void mana_per_port_queue_reset_work_handler(struct work_struct *work)
+{
+	struct mana_queue_reset_work *reset_queue_work =
+			container_of(work, struct mana_queue_reset_work, work);
+	struct mana_port_context *apc = reset_queue_work->apc;
+	struct net_device *ndev = apc->ndev;
+	struct mana_context *ac = apc->ac;
+	int err;
+
+	if (!rtnl_trylock()) {
+		/* Someone else holds RTNL, requeue and exit. */
+		queue_work(ac->per_port_queue_reset_wq,
+			   &apc->queue_reset_work.work);
+		return;
+	}
+
+	/* Pre-allocate buffers to prevent failure in mana_attach later */
+	err = mana_pre_alloc_rxbufs(apc, ndev->mtu, apc->num_queues);
+	if (err) {
+		netdev_err(ndev, "Insufficient memory for reset post tx stall detection\n");
+		goto out;
+	}
+
+	err = mana_detach(ndev, false);
+	if (err) {
+		netdev_err(ndev, "mana_detach failed: %d\n", err);
+		goto dealloc_pre_rxbufs;
+	}
+
+	err = mana_attach(ndev);
+	if (err)
+		netdev_err(ndev, "mana_attach failed: %d\n", err);
+
+dealloc_pre_rxbufs:
+	mana_pre_dealloc_rxbufs(apc);
+out:
+	rtnl_unlock();
+}
+
 netdev_tx_t mana_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 {
 	enum mana_tx_pkt_format pkt_fmt = MANA_SHORT_PKT_FMT;
@@ -762,6 +801,25 @@ static int mana_change_mtu(struct net_device *ndev, int new_mtu)
 	return err;
 }
 
+static void mana_tx_timeout(struct net_device *netdev, unsigned int txqueue)
+{
+	struct mana_port_context *apc = netdev_priv(netdev);
+	struct mana_context *ac = apc->ac;
+	struct gdma_context *gc = ac->gdma_dev->gdma_context;
+
+	netdev_warn(netdev, "%s(): called on txq: %u\n", __func__, txqueue);
+
+	/* Already in service, hence tx queue reset is not required.*/
+	if (gc->in_service)
+		return;
+
+	/* Note: If there are pending queue reset work for this port(apc),
+	 * subsequent request queued up from here are ignored. This is because
+	 * we are using the same work instance per port(apc).
+	 */
+	queue_work(ac->per_port_queue_reset_wq, &apc->queue_reset_work.work);
+}
+
 static int mana_shaper_set(struct net_shaper_binding *binding,
 			   const struct net_shaper *shaper,
 			   struct netlink_ext_ack *extack)
@@ -844,7 +902,9 @@ static const struct net_device_ops mana_devops = {
 	.ndo_bpf		= mana_bpf,
 	.ndo_xdp_xmit		= mana_xdp_xmit,
 	.ndo_change_mtu		= mana_change_mtu,
+	.ndo_tx_timeout     = mana_tx_timeout,
 	.net_shaper_ops         = &mana_shaper_ops,
+
 };
 
 static void mana_cleanup_port_context(struct mana_port_context *apc)
@@ -3218,6 +3278,7 @@ static int mana_probe_port(struct mana_context *ac, int port_idx,
 	ndev->min_mtu = ETH_MIN_MTU;
 	ndev->needed_headroom = MANA_HEADROOM;
 	ndev->dev_port = port_idx;
+	ndev->watchdog_timeo = MANA_TXQ_TIMEOUT;
 	SET_NETDEV_DEV(ndev, gc->dev);
 
 	netif_set_tso_max_size(ndev, GSO_MAX_SIZE);
@@ -3255,6 +3316,11 @@ static int mana_probe_port(struct mana_context *ac, int port_idx,
 
 	debugfs_create_u32("current_speed", 0400, apc->mana_port_debugfs, &apc->speed);
 
+	/* Initialize the per port queue reset work.*/
+	apc->queue_reset_work.apc = apc;
+	INIT_WORK(&apc->queue_reset_work.work,
+		  mana_per_port_queue_reset_work_handler);
+
 	return 0;
 
 free_indir:
@@ -3456,6 +3522,15 @@ int mana_probe(struct gdma_dev *gd, bool resuming)
 	if (ac->num_ports > MAX_PORTS_IN_MANA_DEV)
 		ac->num_ports = MAX_PORTS_IN_MANA_DEV;
 
+	ac->per_port_queue_reset_wq =
+			alloc_ordered_workqueue("mana_per_port_queue_reset_wq",
+						WQ_UNBOUND | WQ_MEM_RECLAIM);
+	if (!ac->per_port_queue_reset_wq) {
+		dev_err(dev, "Failed to allocate per port queue reset workqueue\n");
+		err = -ENOMEM;
+		goto out;
+	}
+
 	if (!resuming) {
 		for (i = 0; i < ac->num_ports; i++) {
 			err = mana_probe_port(ac, i, &ac->ports[i]);
@@ -3528,6 +3603,8 @@ void mana_remove(struct gdma_dev *gd, bool suspending)
 		 */
 		rtnl_lock();
 
+		cancel_work_sync(&apc->queue_reset_work.work);
+
 		err = mana_detach(ndev, false);
 		if (err)
 			netdev_err(ndev, "Failed to detach vPort %d: %d\n",
@@ -3547,6 +3624,11 @@ void mana_remove(struct gdma_dev *gd, bool suspending)
 		free_netdev(ndev);
 	}
 
+	if (ac->per_port_queue_reset_wq) {
+		destroy_workqueue(ac->per_port_queue_reset_wq);
+		ac->per_port_queue_reset_wq = NULL;
+	}
+
 	mana_destroy_eq(ac);
 out:
 	mana_gd_deregister_device(gd);
diff --git a/include/net/mana/gdma.h b/include/net/mana/gdma.h
index 57df78cfbf82..1f8c536ba3be 100644
--- a/include/net/mana/gdma.h
+++ b/include/net/mana/gdma.h
@@ -591,6 +591,9 @@ enum {
 /* Driver can self reset on FPGA Reconfig EQE notification */
 #define GDMA_DRV_CAP_FLAG_1_HANDLE_RECONFIG_EQE BIT(17)
 
+/* Driver detects stalled send queues and recovers them */
+#define GDMA_DRV_CAP_FLAG_1_HANDLE_STALL_SQ_RECOVERY BIT(18)
+
 #define GDMA_DRV_CAP_FLAGS1 \
 	(GDMA_DRV_CAP_FLAG_1_EQ_SHARING_MULTI_VPORT | \
 	 GDMA_DRV_CAP_FLAG_1_NAPI_WKDONE_FIX | \
@@ -599,7 +602,8 @@ enum {
 	 GDMA_DRV_CAP_FLAG_1_DEV_LIST_HOLES_SUP | \
 	 GDMA_DRV_CAP_FLAG_1_DYNAMIC_IRQ_ALLOC_SUPPORT | \
 	 GDMA_DRV_CAP_FLAG_1_SELF_RESET_ON_EQE | \
-	 GDMA_DRV_CAP_FLAG_1_HANDLE_RECONFIG_EQE)
+	 GDMA_DRV_CAP_FLAG_1_HANDLE_RECONFIG_EQE | \
+	 GDMA_DRV_CAP_FLAG_1_HANDLE_STALL_SQ_RECOVERY)
 
 #define GDMA_DRV_CAP_FLAGS2 0
 
diff --git a/include/net/mana/mana.h b/include/net/mana/mana.h
index 0921485565c0..e0b44ae2226a 100644
--- a/include/net/mana/mana.h
+++ b/include/net/mana/mana.h
@@ -67,6 +67,11 @@ enum TRI_STATE {
 
 #define MANA_RX_FRAG_ALIGNMENT 64
 
+/* Timeout value for Txq stall detection & recovery used by ndo_tx_timeout.
+ * The value is chosen after considering fpga re-config scenarios.
+ */
+#define MANA_TXQ_TIMEOUT (15 * HZ)
+
 struct mana_stats_rx {
 	u64 packets;
 	u64 bytes;
@@ -475,13 +480,23 @@ struct mana_context {
 
 	struct mana_eq *eqs;
 	struct dentry *mana_eqs_debugfs;
+	struct workqueue_struct *per_port_queue_reset_wq;
 
 	struct net_device *ports[MAX_PORTS_IN_MANA_DEV];
 };
 
+struct mana_queue_reset_work {
+
+	/* Work structure */
+	struct work_struct work;
+	/* Pointer to the port context */
+	struct mana_port_context *apc;
+};
+
 struct mana_port_context {
 	struct mana_context *ac;
 	struct net_device *ndev;
+	struct mana_queue_reset_work queue_reset_work;
 
 	u8 mac_addr[ETH_ALEN];
 
-- 
2.43.0

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