[dpdk-stable] [PATCH 19.11.9 1/3] net/hns3: fix HW buffer size on MTU update

["Min Hu (Connor)" <humin29@huawei.com>]

From: Chengchang Tang <tangchengchang@huawei.com>

[ upstream commit 25fb790f7868f8eee96f7f051a834dec01b8a369 ]

After MTU changed, the buffer used to store packets in HW should be
reallocated. And buffer size is allocated based on the maximum frame
size in the PF struct. However, the value of maximum frame size  is
not updated in time when MTU is changed. This would lead to a packet
loss for not enough buffer.

This patch update the maximum frame size before reallocating the HW
buffer. And a rollback operation is added to avoid the side effects
of buffer reallocation failures.

Fixes: 1f5ca0b460cd ("net/hns3: support some device operations")
Fixes: d51867db65c1 ("net/hns3: add initialization")
Cc: stable@dpdk.org

Signed-off-by: Chengchang Tang <tangchengchang@huawei.com>
Signed-off-by: Lijun Ou <oulijun@huawei.com>
---
 drivers/net/hns3/hns3_ethdev.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/drivers/net/hns3/hns3_ethdev.c b/drivers/net/hns3/hns3_ethdev.c
index 3a799ed..952538d 100644
--- a/drivers/net/hns3/hns3_ethdev.c
+++ b/drivers/net/hns3/hns3_ethdev.c
@@ -2418,21 +2418,35 @@ hns3_set_mac_mtu(struct hns3_hw *hw, uint16_t new_mps)
 static int
 hns3_config_mtu(struct hns3_hw *hw, uint16_t mps)
 {
+	struct hns3_adapter *hns = HNS3_DEV_HW_TO_ADAPTER(hw);
+	uint16_t original_mps = hns->pf.mps;
+	int err;
 	int ret;
 
 	ret = hns3_set_mac_mtu(hw, mps);
 	if (ret) {
-		hns3_err(hw, "Failed to set mtu, ret = %d", ret);
+		hns3_err(hw, "failed to set mtu, ret = %d", ret);
 		return ret;
 	}
 
+	hns->pf.mps = mps;
 	ret = hns3_buffer_alloc(hw);
 	if (ret) {
-		hns3_err(hw, "Failed to allocate buffer, ret = %d", ret);
-		return ret;
+		hns3_err(hw, "failed to allocate buffer, ret = %d", ret);
+		goto rollback;
 	}
 
 	return 0;
+
+rollback:
+	err = hns3_set_mac_mtu(hw, original_mps);
+	if (err) {
+		hns3_err(hw, "fail to rollback MTU, err = %d", err);
+		return ret;
+	}
+	hns->pf.mps = original_mps;
+
+	return ret;
 }
 
 static int
@@ -2465,7 +2479,7 @@ hns3_dev_mtu_set(struct rte_eth_dev *dev, uint16_t mtu)
 			 dev->data->port_id, mtu, ret);
 		return ret;
 	}
-	hns->pf.mps = (uint16_t)frame_size;
+
 	if (is_jumbo_frame)
 		dev->data->dev_conf.rxmode.offloads |=
 						DEV_RX_OFFLOAD_JUMBO_FRAME;
-- 
2.7.4