From 784ba0a03ddd16a54b9d23757d587b67b832e2b7 Mon Sep 17 00:00:00 2001
From: Chengwen Feng <fengchengwen@huawei.com>
Date: Thu, 11 Apr 2024 12:04:08 +0000
Subject: [PATCH] ethdev: fix strict aliasing lead to link cannot be up

Fix a problem introduced by a compiler upgrade (from gcc10 to gcc12.3),
which will lead the hns3 NIC can't link up. The root cause is strict
aliasing violation in rte_eth_linkstatus_set() with hns3 driver, see
[1] for more details.

This commit use union to avoid such aliasing violation.

[1] Strict aliasing problem with rte_eth_linkstatus_set()
    https://marc.info/?l=dpdk-dev&m=171274148514777&w=3

Cc: stable@dpdk.org

Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
Signed-off-by: Dengdui Huang <huangdengdui@huawei.com>
---
 lib/ethdev/ethdev_driver.h | 23 +++++++----------------
 lib/ethdev/rte_ethdev.h    | 16 ++++++++++------
 2 files changed, 17 insertions(+), 22 deletions(-)

diff --git a/lib/ethdev/ethdev_driver.h b/lib/ethdev/ethdev_driver.h
index b482cd1..12a7bfc 100644
--- a/lib/ethdev/ethdev_driver.h
+++ b/lib/ethdev/ethdev_driver.h
@@ -1655,18 +1655,13 @@ static inline int
 rte_eth_linkstatus_set(struct rte_eth_dev *dev,
 		       const struct rte_eth_link *new_link)
 {
-	RTE_ATOMIC(uint64_t) *dev_link = (uint64_t __rte_atomic *)&(dev->data->dev_link);
-	union {
-		uint64_t val64;
-		struct rte_eth_link link;
-	} orig;
-
-	RTE_BUILD_BUG_ON(sizeof(*new_link) != sizeof(uint64_t));
+	struct rte_eth_link old_link;
 
-	orig.val64 = rte_atomic_exchange_explicit(dev_link, *(const uint64_t *)new_link,
-					rte_memory_order_seq_cst);
+	old_link.val64 = rte_atomic_exchange_explicit(&dev->data->dev_link.val64,
+						      new_link->val64,
+						      rte_memory_order_seq_cst);
 
-	return (orig.link.link_status == new_link->link_status) ? -1 : 0;
+	return (old_link.link_status == new_link->link_status) ? -1 : 0;
 }
 
 /**
@@ -1682,12 +1677,8 @@ static inline void
 rte_eth_linkstatus_get(const struct rte_eth_dev *dev,
 		       struct rte_eth_link *link)
 {
-	RTE_ATOMIC(uint64_t) *src = (uint64_t __rte_atomic *)&(dev->data->dev_link);
-	uint64_t *dst = (uint64_t *)link;
-
-	RTE_BUILD_BUG_ON(sizeof(*link) != sizeof(uint64_t));
-
-	*dst = rte_atomic_load_explicit(src, rte_memory_order_seq_cst);
+	link->val64 = rte_atomic_load_explicit(&dev->data->dev_link.val64,
+					       rte_memory_order_seq_cst);
 }
 
 /**
diff --git a/lib/ethdev/rte_ethdev.h b/lib/ethdev/rte_ethdev.h
index 57a9a55..b4b0357 100644
--- a/lib/ethdev/rte_ethdev.h
+++ b/lib/ethdev/rte_ethdev.h
@@ -331,13 +331,17 @@ struct rte_eth_stats {
 /**
  * A structure used to retrieve link-level information of an Ethernet port.
  */
-__extension__
 struct rte_eth_link {
-	uint32_t link_speed;        /**< RTE_ETH_SPEED_NUM_ */
-	uint16_t link_duplex  : 1;  /**< RTE_ETH_LINK_[HALF/FULL]_DUPLEX */
-	uint16_t link_autoneg : 1;  /**< RTE_ETH_LINK_[AUTONEG/FIXED] */
-	uint16_t link_status  : 1;  /**< RTE_ETH_LINK_[DOWN/UP] */
-} __rte_aligned(8);      /**< aligned for atomic64 read/write */
+       union {
+               RTE_ATOMIC(uint64_t) val64; /**< used for atomic64 read/write */
+               struct {
+                       uint32_t link_speed;        /**< RTE_ETH_SPEED_NUM_ */
+                       uint16_t link_duplex  : 1;  /**< RTE_ETH_LINK_[HALF/FULL]_DUPLEX */
+                       uint16_t link_autoneg : 1;  /**< RTE_ETH_LINK_[AUTONEG/FIXED] */
+                       uint16_t link_status  : 1;  /**< RTE_ETH_LINK_[DOWN/UP] */
+               };
+       };
+};
 
 /**@{@name Link negotiation
  * Constants used in link management.
-- 
2.33.0

