ethdev: fix strict aliasing in link 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. Also the
impacted components (cxgbe and qos_sched) have been adapted to the
struct change.

[1] https://inbox.dpdk.org/dev/[email protected]/

Cc: [email protected]

Signed-off-by: Chengwen Feng <[email protected]>
Signed-off-by: Dengdui Huang <[email protected]>
Acked-by: Morten Brørup <[email protected]>
Acked-by: Ferruh Yigit <[email protected]>

2 files changed, 20 insertions, 21 deletions

diff --git a/lib/ethdev/ethdev_driver.h b/lib/ethdev/ethdev_driver.h
index 0dbf2dd6a2..883e59a927 100644
--- a/lib/ethdev/ethdev_driver.h
+++ b/lib/ethdev/ethdev_driver.h
@@ -1674,18 +1674,13 @@ 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;
 }
 
 /**
@@ -1701,12 +1696,11 @@ 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));
+	struct rte_eth_link curr_link;
 
-	*dst = rte_atomic_load_explicit(src, rte_memory_order_seq_cst);
+	curr_link.val64 = rte_atomic_load_explicit(&dev->data->dev_link.val64,
+						   rte_memory_order_seq_cst);
+	rte_atomic_store_explicit(&link->val64, curr_link.val64, rte_memory_order_seq_cst);
 }
 
 /**
diff --git a/lib/ethdev/rte_ethdev.h b/lib/ethdev/rte_ethdev.h
index 147257d6a2..548fada1c7 100644
--- a/lib/ethdev/rte_ethdev.h
+++ b/lib/ethdev/rte_ethdev.h
@@ -332,12 +332,17 @@ struct rte_eth_stats {
 /**
  * A structure used to retrieve link-level information of an Ethernet port.
  */
-__extension__
-struct __rte_aligned(8) rte_eth_link { /**< aligned for atomic64 read/write */
-	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] */
+struct rte_eth_link {
+	union {
+		RTE_ATOMIC(uint64_t) val64; /**< used for atomic64 read/write */
+		__extension__
+		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