net/hns3: fix VF mailbox head field

[ upstream commit 38d5b71 ]

Currently, the VF mailbox synchronization communication is based on
three fields: head/tail/lost, when head equals tail plus lost, it
means the response is received successfully.

The head field indicates the number of requests that are successfully
sent. If the request sending fails, it should not be updated.

This patch fix the above bug by roll back updates when the sending
fails.

Fixes: 463e748 ("net/hns3: support mailbox")

Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
Signed-off-by: Min Hu (Connor) <humin29@huawei.com>

drivers/net/hns3/hns3_mbx.c

@@ -184,6 +184,7 @@ hns3_send_mbx_msg(struct hns3_hw *hw, uint16_t code, uint16_t subcode,
 		hw->mbx_resp.head++;
 		ret = hns3_cmd_send(hw, &desc, 1);
 		if (ret) {
+			hw->mbx_resp.head--;
 			rte_spinlock_unlock(&hw->mbx_resp.lock);
 			hns3_err(hw, "VF failed(=%d) to send mbx message to PF",
 				 ret);