[PATCH] ethdev: fix strict aliasing lead to link cannot be up

[Chengwen Feng]

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: sta...@dpdk.org

Signed-off-by: Chengwen Feng <fengcheng...@huawei.com>
Signed-off-by: Dengdui Huang <huangdeng...@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 0dbf2dd6a2..9d831d5c84 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 +1696,8 @@ 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 147257d6a2..0b5d3d2318 100644
--- a/lib/ethdev/rte_ethdev.h
+++ b/lib/ethdev/rte_ethdev.h
@@ -332,12 +332,16 @@ 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 {
+               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
-- 
2.17.1