[PATCH net-next v6 0/2] net: mana: Enforce TX SGE limit and fix error cleanup

[PATCH net-next v6 0/2] net: mana: Enforce TX SGE limit and fix error cleanup

[Aditya Garg]

Add pre-transmission checks to block SKBs that exceed the hardware's SGE
limit. Force software segmentation for GSO traffic and linearize non-GSO
packets as needed.

Update TX error handling to drop failed SKBs and unmap resources
immediately.

---
Changes in v6:
* Replace #if logic with constant expression in if().

Changes in v5:
* Drop skb_is_gso() check for disabling GSO in mana_features_check().
* Register .ndo_features_check conditionally to avoid unnecessary call.

Changes in v4:
* Fix warning during build reported by kernel test robot
---
Aditya Garg (2):
  net: mana: Handle SKB if TX SGEs exceed hardware limit
  net: mana: Drop TX skb on post_work_request failure and unmap
    resources

 .../net/ethernet/microsoft/mana/gdma_main.c   |  6 +--
 drivers/net/ethernet/microsoft/mana/mana_en.c | 47 ++++++++++++++++---
 .../ethernet/microsoft/mana/mana_ethtool.c    |  2 +
 include/net/mana/gdma.h                       |  8 +++-
 include/net/mana/mana.h                       |  2 +
 5 files changed, 53 insertions(+), 12 deletions(-)

-- 
2.43.0

[PATCH net-next v6 1/2] net: mana: Handle SKB if TX SGEs exceed hardware limit

[Aditya Garg]

The MANA hardware supports a maximum of 30 scatter-gather entries (SGEs)
per TX WQE. Exceeding this limit can cause TX failures.
Add ndo_features_check() callback to validate SKB layout before
transmission. For GSO SKBs that would exceed the hardware SGE limit, clear
NETIF_F_GSO_MASK to enforce software segmentation in the stack.
Add a fallback in mana_start_xmit() to linearize non-GSO SKBs that still
exceed the SGE limit.

Also, Add ethtool counter for SKBs linearized

Co-developed-by: Dipayaan Roy <dipayanroy@linux.microsoft.com>
Signed-off-by: Dipayaan Roy <dipayanroy@linux.microsoft.com>
Signed-off-by: Aditya Garg <gargaditya@linux.microsoft.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
---
Changes in v6:
* Replace #if logic with constant expression in if().

Changes in v5:
* Drop skb_is_gso() check for disabling GSO in mana_features_check().
* Register .ndo_features_check conditionally to avoid unnecessary call.

Changes in v4:
* No change.
---
 drivers/net/ethernet/microsoft/mana/mana_en.c | 40 ++++++++++++++++++-
 .../ethernet/microsoft/mana/mana_ethtool.c    |  2 +
 include/net/mana/gdma.h                       |  8 +++-
 include/net/mana/mana.h                       |  1 +
 4 files changed, 48 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
index 13f47be7aca6..7b49ab005e2d 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_en.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
@@ -11,6 +11,7 @@
 #include <linux/mm.h>
 #include <linux/pci.h>
 #include <linux/export.h>
+#include <linux/skbuff.h>
 
 #include <net/checksum.h>
 #include <net/ip6_checksum.h>
@@ -329,6 +330,21 @@ netdev_tx_t mana_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 	cq = &apc->tx_qp[txq_idx].tx_cq;
 	tx_stats = &txq->stats;
 
+	BUILD_BUG_ON(MAX_TX_WQE_SGL_ENTRIES != MANA_MAX_TX_WQE_SGL_ENTRIES);
+	if (MAX_SKB_FRAGS + 2 > MAX_TX_WQE_SGL_ENTRIES &&
+	    skb_shinfo(skb)->nr_frags + 2 > MAX_TX_WQE_SGL_ENTRIES) {
+		/* GSO skb with Hardware SGE limit exceeded is not expected here
+		 * as they are handled in mana_features_check() callback
+		 */
+		if (skb_linearize(skb)) {
+			netdev_warn_once(ndev, "Failed to linearize skb with nr_frags=%d and is_gso=%d\n",
+					 skb_shinfo(skb)->nr_frags,
+					 skb_is_gso(skb));
+			goto tx_drop_count;
+		}
+		apc->eth_stats.tx_linear_pkt_cnt++;
+	}
+
 	pkg.tx_oob.s_oob.vcq_num = cq->gdma_id;
 	pkg.tx_oob.s_oob.vsq_frame = txq->vsq_frame;
 
@@ -442,8 +458,6 @@ netdev_tx_t mana_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 		}
 	}
 
-	WARN_ON_ONCE(pkg.wqe_req.num_sge > MAX_TX_WQE_SGL_ENTRIES);
-
 	if (pkg.wqe_req.num_sge <= ARRAY_SIZE(pkg.sgl_array)) {
 		pkg.wqe_req.sgl = pkg.sgl_array;
 	} else {
@@ -518,6 +532,25 @@ netdev_tx_t mana_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 	return NETDEV_TX_OK;
 }
 
+#if (MAX_SKB_FRAGS + 2 > MANA_MAX_TX_WQE_SGL_ENTRIES)
+static netdev_features_t mana_features_check(struct sk_buff *skb,
+					     struct net_device *ndev,
+					     netdev_features_t features)
+{
+	if (skb_shinfo(skb)->nr_frags + 2 > MAX_TX_WQE_SGL_ENTRIES) {
+		/* Exceeds HW SGE limit.
+		 * GSO case:
+		 *   Disable GSO so the stack will software-segment the skb
+		 *   into smaller skbs that fit the SGE budget.
+		 * Non-GSO case:
+		 *   The xmit path will attempt skb_linearize() as a fallback.
+		 */
+		features &= ~NETIF_F_GSO_MASK;
+	}
+	return features;
+}
+#endif
+
 static void mana_get_stats64(struct net_device *ndev,
 			     struct rtnl_link_stats64 *st)
 {
@@ -883,6 +916,9 @@ static const struct net_device_ops mana_devops = {
 	.ndo_open		= mana_open,
 	.ndo_stop		= mana_close,
 	.ndo_select_queue	= mana_select_queue,
+#if (MAX_SKB_FRAGS + 2 > MANA_MAX_TX_WQE_SGL_ENTRIES)
+	.ndo_features_check	= mana_features_check,
+#endif
 	.ndo_start_xmit		= mana_start_xmit,
 	.ndo_validate_addr	= eth_validate_addr,
 	.ndo_get_stats64	= mana_get_stats64,
diff --git a/drivers/net/ethernet/microsoft/mana/mana_ethtool.c b/drivers/net/ethernet/microsoft/mana/mana_ethtool.c
index 99e811208683..0e2f4343ac67 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_ethtool.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_ethtool.c
@@ -18,6 +18,8 @@ static const struct mana_stats_desc mana_eth_stats[] = {
 	{"tx_cq_err", offsetof(struct mana_ethtool_stats, tx_cqe_err)},
 	{"tx_cqe_unknown_type", offsetof(struct mana_ethtool_stats,
 					tx_cqe_unknown_type)},
+	{"tx_linear_pkt_cnt", offsetof(struct mana_ethtool_stats,
+				       tx_linear_pkt_cnt)},
 	{"rx_coalesced_err", offsetof(struct mana_ethtool_stats,
 					rx_coalesced_err)},
 	{"rx_cqe_unknown_type", offsetof(struct mana_ethtool_stats,
diff --git a/include/net/mana/gdma.h b/include/net/mana/gdma.h
index 2e4f2f3175e5..a4cf307859f8 100644
--- a/include/net/mana/gdma.h
+++ b/include/net/mana/gdma.h
@@ -486,6 +486,8 @@ struct gdma_wqe {
 #define INLINE_OOB_SMALL_SIZE 8
 #define INLINE_OOB_LARGE_SIZE 24
 
+#define MANA_MAX_TX_WQE_SGL_ENTRIES 30
+
 #define MAX_TX_WQE_SIZE 512
 #define MAX_RX_WQE_SIZE 256
 
@@ -592,6 +594,9 @@ enum {
 #define GDMA_DRV_CAP_FLAG_1_HANDLE_RECONFIG_EQE BIT(17)
 #define GDMA_DRV_CAP_FLAG_1_HW_VPORT_LINK_AWARE BIT(6)
 
+/* Driver supports linearizing the skb when num_sge exceeds hardware limit */
+#define GDMA_DRV_CAP_FLAG_1_SKB_LINEARIZE BIT(20)
+
 /* Driver can send HWC periodically to query stats */
 #define GDMA_DRV_CAP_FLAG_1_PERIODIC_STATS_QUERY BIT(21)
 
@@ -605,7 +610,8 @@ enum {
 	 GDMA_DRV_CAP_FLAG_1_SELF_RESET_ON_EQE | \
 	 GDMA_DRV_CAP_FLAG_1_HANDLE_RECONFIG_EQE | \
 	 GDMA_DRV_CAP_FLAG_1_HW_VPORT_LINK_AWARE | \
-	 GDMA_DRV_CAP_FLAG_1_PERIODIC_STATS_QUERY)
+	 GDMA_DRV_CAP_FLAG_1_PERIODIC_STATS_QUERY | \
+	 GDMA_DRV_CAP_FLAG_1_SKB_LINEARIZE)
 
 #define GDMA_DRV_CAP_FLAGS2 0
 
diff --git a/include/net/mana/mana.h b/include/net/mana/mana.h
index d37f4cea0ac3..fb28b3cac067 100644
--- a/include/net/mana/mana.h
+++ b/include/net/mana/mana.h
@@ -377,6 +377,7 @@ struct mana_ethtool_stats {
 	u64 wake_queue;
 	u64 tx_cqe_err;
 	u64 tx_cqe_unknown_type;
+	u64 tx_linear_pkt_cnt;
 	u64 rx_coalesced_err;
 	u64 rx_cqe_unknown_type;
 };
-- 
2.43.0

[PATCH net-next v6 2/2] net: mana: Drop TX skb on post_work_request failure and unmap resources

[Aditya Garg]

Drop TX packets when posting the work request fails and ensure DMA
mappings are always cleaned up.

Signed-off-by: Aditya Garg <gargaditya@linux.microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
---
Changes in v6:
* No change.

Changes in v5:
* No change.

Changes in v4:
* Fix warning during build reported by kernel test robot
---
 drivers/net/ethernet/microsoft/mana/gdma_main.c | 6 +-----
 drivers/net/ethernet/microsoft/mana/mana_en.c   | 7 +++----
 include/net/mana/mana.h                         | 1 +
 3 files changed, 5 insertions(+), 9 deletions(-)

diff --git a/drivers/net/ethernet/microsoft/mana/gdma_main.c b/drivers/net/ethernet/microsoft/mana/gdma_main.c
index effe0a2f207a..8fd70b34807a 100644
--- a/drivers/net/ethernet/microsoft/mana/gdma_main.c
+++ b/drivers/net/ethernet/microsoft/mana/gdma_main.c
@@ -1300,7 +1300,6 @@ int mana_gd_post_work_request(struct gdma_queue *wq,
 			      struct gdma_posted_wqe_info *wqe_info)
 {
 	u32 client_oob_size = wqe_req->inline_oob_size;
-	struct gdma_context *gc;
 	u32 sgl_data_size;
 	u32 max_wqe_size;
 	u32 wqe_size;
@@ -1330,11 +1329,8 @@ int mana_gd_post_work_request(struct gdma_queue *wq,
 	if (wqe_size > max_wqe_size)
 		return -EINVAL;
 
-	if (wq->monitor_avl_buf && wqe_size > mana_gd_wq_avail_space(wq)) {
-		gc = wq->gdma_dev->gdma_context;
-		dev_err(gc->dev, "unsuccessful flow control!\n");
+	if (wq->monitor_avl_buf && wqe_size > mana_gd_wq_avail_space(wq))
 		return -ENOSPC;
-	}
 
 	if (wqe_info)
 		wqe_info->wqe_size_in_bu = wqe_size / GDMA_WQE_BU_SIZE;
diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
index 7b49ab005e2d..1ad154f9db1a 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_en.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
@@ -492,9 +492,9 @@ netdev_tx_t mana_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 
 	if (err) {
 		(void)skb_dequeue_tail(&txq->pending_skbs);
+		mana_unmap_skb(skb, apc);
 		netdev_warn(ndev, "Failed to post TX OOB: %d\n", err);
-		err = NETDEV_TX_BUSY;
-		goto tx_busy;
+		goto free_sgl_ptr;
 	}
 
 	err = NETDEV_TX_OK;
@@ -514,7 +514,6 @@ netdev_tx_t mana_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 	tx_stats->bytes += len + ((num_gso_seg - 1) * gso_hs);
 	u64_stats_update_end(&tx_stats->syncp);
 
-tx_busy:
 	if (netif_tx_queue_stopped(net_txq) && mana_can_tx(gdma_sq)) {
 		netif_tx_wake_queue(net_txq);
 		apc->eth_stats.wake_queue++;
@@ -1687,7 +1686,7 @@ static int mana_move_wq_tail(struct gdma_queue *wq, u32 num_units)
 	return 0;
 }
 
-static void mana_unmap_skb(struct sk_buff *skb, struct mana_port_context *apc)
+void mana_unmap_skb(struct sk_buff *skb, struct mana_port_context *apc)
 {
 	struct mana_skb_head *ash = (struct mana_skb_head *)skb->head;
 	struct gdma_context *gc = apc->ac->gdma_dev->gdma_context;
diff --git a/include/net/mana/mana.h b/include/net/mana/mana.h
index fb28b3cac067..d7e089c6b694 100644
--- a/include/net/mana/mana.h
+++ b/include/net/mana/mana.h
@@ -593,6 +593,7 @@ int mana_set_bw_clamp(struct mana_port_context *apc, u32 speed,
 void mana_query_phy_stats(struct mana_port_context *apc);
 int mana_pre_alloc_rxbufs(struct mana_port_context *apc, int mtu, int num_queues);
 void mana_pre_dealloc_rxbufs(struct mana_port_context *apc);
+void mana_unmap_skb(struct sk_buff *skb, struct mana_port_context *apc);
 
 extern const struct ethtool_ops mana_ethtool_ops;
 extern struct dentry *mana_debugfs_root;
-- 
2.43.0

Re: [PATCH net-next v6 0/2] net: mana: Enforce TX SGE limit and fix error cleanup

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Tue, 18 Nov 2025 03:11:07 -0800 you wrote:
> Add pre-transmission checks to block SKBs that exceed the hardware's SGE
> limit. Force software segmentation for GSO traffic and linearize non-GSO
> packets as needed.
> 
> Update TX error handling to drop failed SKBs and unmap resources
> immediately.
> 
> [...]

Here is the summary with links:
  - [net-next,v6,1/2] net: mana: Handle SKB if TX SGEs exceed hardware limit
    https://git.kernel.org/netdev/net-next/c/934fa943b537
  - [net-next,v6,2/2] net: mana: Drop TX skb on post_work_request failure and unmap resources
    https://git.kernel.org/netdev/net-next/c/45120304e841

You are awesome, thank you!
-- 
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