[PATCH net-next v3 0/2] net: mana: Enforce TX SGE limit and fix error cleanup

[PATCH net-next v3 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.

Aditya Garg (2):
  net: mana: Handle SKB if TX SGEs exceed hardware limit
  net: mana: Drop TX skb on post failure and unmap resources

 .../net/ethernet/microsoft/mana/gdma_main.c   |  1 -
 drivers/net/ethernet/microsoft/mana/mana_en.c | 44 ++++++++++++++++---
 .../ethernet/microsoft/mana/mana_ethtool.c    |  2 +
 include/net/mana/gdma.h                       |  6 ++-
 include/net/mana/mana.h                       |  2 +
 5 files changed, 47 insertions(+), 8 deletions(-)

-- 
2.43.0

[PATCH net-next v3 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>
---
 drivers/net/ethernet/microsoft/mana/mana_en.c | 37 ++++++++++++++++++-
 .../ethernet/microsoft/mana/mana_ethtool.c    |  2 +
 include/net/mana/gdma.h                       |  6 ++-
 include/net/mana/mana.h                       |  1 +
 4 files changed, 43 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
index cccd5b63cee6..67ae5421f9ee 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 +330,20 @@ 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;
 
+	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.linear_pkt_tx_cnt++;
+	}
+
 	pkg.tx_oob.s_oob.vcq_num = cq->gdma_id;
 	pkg.tx_oob.s_oob.vsq_frame = txq->vsq_frame;
 
@@ -442,8 +457,6 @@ 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 +531,25 @@ netdev_tx_t mana_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 	return NETDEV_TX_OK;
 }
 
+static netdev_features_t mana_features_check(struct sk_buff *skb,
+					     struct net_device *ndev,
+					     netdev_features_t features)
+{
+	if (MAX_SKB_FRAGS + 2 > MAX_TX_WQE_SGL_ENTRIES &&
+	    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.
+		 */
+		if (skb_is_gso(skb))
+			features &= ~NETIF_F_GSO_MASK;
+	}
+	return features;
+}
+
 static void mana_get_stats64(struct net_device *ndev,
 			     struct rtnl_link_stats64 *st)
 {
@@ -878,6 +910,7 @@ static const struct net_device_ops mana_devops = {
 	.ndo_open		= mana_open,
 	.ndo_stop		= mana_close,
 	.ndo_select_queue	= mana_select_queue,
+	.ndo_features_check	= mana_features_check,
 	.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 a1afa75a9463..fa5e1a2f06a9 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_ethtool.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_ethtool.c
@@ -71,6 +71,8 @@ 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)},
+	{"linear_pkt_tx_cnt", offsetof(struct mana_ethtool_stats,
+					linear_pkt_tx_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 637f42485dba..84614ebe0f4c 100644
--- a/include/net/mana/gdma.h
+++ b/include/net/mana/gdma.h
@@ -592,6 +592,9 @@ 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)
+
 #define GDMA_DRV_CAP_FLAGS1 \
 	(GDMA_DRV_CAP_FLAG_1_EQ_SHARING_MULTI_VPORT | \
 	 GDMA_DRV_CAP_FLAG_1_NAPI_WKDONE_FIX | \
@@ -601,7 +604,8 @@ enum {
 	 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_HW_VPORT_LINK_AWARE)
+	 GDMA_DRV_CAP_FLAG_1_HW_VPORT_LINK_AWARE | \
+	 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 8906901535f5..50a532fb30d6 100644
--- a/include/net/mana/mana.h
+++ b/include/net/mana/mana.h
@@ -404,6 +404,7 @@ struct mana_ethtool_stats {
 	u64 hc_tx_err_gdma;
 	u64 tx_cqe_err;
 	u64 tx_cqe_unknown_type;
+	u64 linear_pkt_tx_cnt;
 	u64 rx_coalesced_err;
 	u64 rx_cqe_unknown_type;
 };
-- 
2.43.0

[PATCH net-next v3 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>
---
 drivers/net/ethernet/microsoft/mana/gdma_main.c | 1 -
 drivers/net/ethernet/microsoft/mana/mana_en.c   | 7 +++----
 include/net/mana/mana.h                         | 1 +
 3 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/microsoft/mana/gdma_main.c b/drivers/net/ethernet/microsoft/mana/gdma_main.c
index effe0a2f207a..65dd8060c7f4 100644
--- a/drivers/net/ethernet/microsoft/mana/gdma_main.c
+++ b/drivers/net/ethernet/microsoft/mana/gdma_main.c
@@ -1332,7 +1332,6 @@ int mana_gd_post_work_request(struct gdma_queue *wq,
 
 	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");
 		return -ENOSPC;
 	}
 
diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
index 67ae5421f9ee..066d822f68f0 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_en.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
@@ -491,9 +491,9 @@ 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;
@@ -513,7 +513,6 @@ 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++;
@@ -1679,7 +1678,7 @@ 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 50a532fb30d6..d05457d3e1ab 100644
--- a/include/net/mana/mana.h
+++ b/include/net/mana/mana.h
@@ -585,6 +585,7 @@ 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 v3 2/2] net: mana: Drop TX skb on post_work_request failure and unmap resources

[Jakub Kicinski]

On Tue, 11 Nov 2025 00:13:01 -0800 Aditya Garg wrote:
> Drop TX packets when posting the work request fails and ensure DMA
> mappings are always cleaned up.

drivers/net/ethernet/microsoft/mana/gdma_main.c:1303:23: warning: variable 'gc' set but not used [-Wunused-but-set-variable]
 1303 |         struct gdma_context *gc;
      |                              ^
-- 
pw-bot: cr

Re: [PATCH net-next v3 2/2] net: mana: Drop TX skb on post_work_request failure and unmap resources

[kernel test robot]

Hi Aditya,

kernel test robot noticed the following build warnings:

[auto build test WARNING on net-next/main]

url:    https://github.com/intel-lab-lkp/linux/commits/Aditya-Garg/net-mana-Handle-SKB-if-TX-SGEs-exceed-hardware-limit/20251111-162216
base:   net-next/main
patch link:    https://lore.kernel.org/r/1762848781-357-3-git-send-email-gargaditya%40linux.microsoft.com
patch subject: [PATCH net-next v3 2/2] net: mana: Drop TX skb on post_work_request failure and unmap resources
config: arm64-allyesconfig (https://download.01.org/0day-ci/archive/20251112/202511120917.rSwJ1zUm-lkp@intel.com/config)
compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project 996639d6ebb86ff15a8c99b67f1c2e2117636ae7)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251112/202511120917.rSwJ1zUm-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202511120917.rSwJ1zUm-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/net/ethernet/microsoft/mana/gdma_main.c:1303:23: warning: variable 'gc' set but not used [-Wunused-but-set-variable]
    1303 |         struct gdma_context *gc;
         |                              ^
   1 warning generated.


vim +/gc +1303 drivers/net/ethernet/microsoft/mana/gdma_main.c

ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1297  
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1298  int mana_gd_post_work_request(struct gdma_queue *wq,
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1299  			      const struct gdma_wqe_request *wqe_req,
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1300  			      struct gdma_posted_wqe_info *wqe_info)
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1301  {
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1302  	u32 client_oob_size = wqe_req->inline_oob_size;
ca9c54d2d6a5ab Dexuan Cui         2021-04-16 @1303  	struct gdma_context *gc;
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1304  	u32 sgl_data_size;
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1305  	u32 max_wqe_size;
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1306  	u32 wqe_size;
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1307  	u8 *wqe_ptr;
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1308  
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1309  	if (wqe_req->num_sge == 0)
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1310  		return -EINVAL;
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1311  
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1312  	if (wq->type == GDMA_RQ) {
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1313  		if (client_oob_size != 0)
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1314  			return -EINVAL;
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1315  
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1316  		client_oob_size = INLINE_OOB_SMALL_SIZE;
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1317  
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1318  		max_wqe_size = GDMA_MAX_RQE_SIZE;
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1319  	} else {
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1320  		if (client_oob_size != INLINE_OOB_SMALL_SIZE &&
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1321  		    client_oob_size != INLINE_OOB_LARGE_SIZE)
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1322  			return -EINVAL;
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1323  
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1324  		max_wqe_size = GDMA_MAX_SQE_SIZE;
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1325  	}
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1326  
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1327  	sgl_data_size = sizeof(struct gdma_sge) * wqe_req->num_sge;
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1328  	wqe_size = ALIGN(sizeof(struct gdma_wqe) + client_oob_size +
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1329  			 sgl_data_size, GDMA_WQE_BU_SIZE);
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1330  	if (wqe_size > max_wqe_size)
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1331  		return -EINVAL;
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1332  
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1333  	if (wq->monitor_avl_buf && wqe_size > mana_gd_wq_avail_space(wq)) {
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1334  		gc = wq->gdma_dev->gdma_context;
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1335  		return -ENOSPC;
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1336  	}
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1337  
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1338  	if (wqe_info)
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1339  		wqe_info->wqe_size_in_bu = wqe_size / GDMA_WQE_BU_SIZE;
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1340  
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1341  	wqe_ptr = mana_gd_get_wqe_ptr(wq, wq->head);
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1342  	wqe_ptr += mana_gd_write_client_oob(wqe_req, wq->type, client_oob_size,
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1343  					    sgl_data_size, wqe_ptr);
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1344  	if (wqe_ptr >= (u8 *)wq->queue_mem_ptr + wq->queue_size)
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1345  		wqe_ptr -= wq->queue_size;
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1346  
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1347  	mana_gd_write_sgl(wq, wqe_ptr, wqe_req);
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1348  
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1349  	wq->head += wqe_size / GDMA_WQE_BU_SIZE;
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1350  
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1351  	return 0;
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1352  }
c8017f5b4856d5 Konstantin Taranov 2025-01-20  1353  EXPORT_SYMBOL_NS(mana_gd_post_work_request, "NET_MANA");
ca9c54d2d6a5ab Dexuan Cui         2021-04-16  1354  

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH net-next v3 2/2] net: mana: Drop TX skb on post_work_request failure and unmap resources

[Aditya Garg]

On 12-11-2025 06:38, Jakub Kicinski wrote:
> On Tue, 11 Nov 2025 00:13:01 -0800 Aditya Garg wrote:
>> Drop TX packets when posting the work request fails and ensure DMA
>> mappings are always cleaned up.
> 
> drivers/net/ethernet/microsoft/mana/gdma_main.c:1303:23: warning: variable 'gc' set but not used [-Wunused-but-set-variable]
>   1303 |         struct gdma_context *gc;
>        |                              ^

Thanks for pointing this out. Will fix this in next revision.

Regards,
Aditya