[dpdk-dev] [PATCH RFC v1 1/6] net/mlx5: relax the barrier for UAR write

[Gavin Hu]

The UAR is part of PCI address space that is mapped for direct access to
the HCA from the CPU. Read-Write accesses to this space are strongly
ordered thus a compiler barrier is sufficient for all arches.

This patch set is based on the following aarch64 architecural facts:
1. The PCI BAR space is mapped as nGnRE device memory, not cachable nor
write-combine.
2. io accesses to a single device is total ordered.

Fixes: 6bf10ab69be0 ("net/mlx5: support 32-bit systems")
Cc: stable at dpdk.org

Signed-off-by: Gavin Hu <gavin.hu at arm.com>
Reviewed-by: Phil Yang <phil.yang at arm.com>
---
 drivers/net/mlx5/mlx5_rxtx.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/mlx5/mlx5_rxtx.h b/drivers/net/mlx5/mlx5_rxtx.h
index 939778aa5..50b3cc3c9 100644
--- a/drivers/net/mlx5/mlx5_rxtx.h
+++ b/drivers/net/mlx5/mlx5_rxtx.h
@@ -546,7 +546,7 @@ __mlx5_uar_write64_relaxed(uint64_t val, void *addr,
 static __rte_always_inline void
 __mlx5_uar_write64(uint64_t val, void *addr, rte_spinlock_t *lock)
 {
-	rte_io_wmb();
+	rte_compiler_barrier();
 	__mlx5_uar_write64_relaxed(val, addr, lock);
 }
 
-- 
2.17.1