From: Joyce Kong <joyce.kong@arm.com>
Date: Mon, 21 Dec 2020 14:23:19 +0000 (+0800)
Subject: net/virtio: replace SMP barrier with IO barrier
X-Git-Url: http://git.droids-corp.org/?p=dpdk.git;a=commitdiff_plain;h=f1b9cf07d3f4fd2111c9044a05188a8a090cfae0

net/virtio: replace SMP barrier with IO barrier

Replace rte_smp_wmb/rmb with rte_io_wmb/rmb as they are the same on x86
and ppc platforms. Then, for function virtqueue_fetch_flags_packed/
virtqueue_store_flags_packed, the if and else branch are still identical
for the platforms except Arm.

Signed-off-by: Joyce Kong <joyce.kong@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---

diff --git a/drivers/net/virtio/virtqueue.h b/drivers/net/virtio/virtqueue.h
index 42c4c9882f..ac3d9e7507 100644
--- a/drivers/net/virtio/virtqueue.h
+++ b/drivers/net/virtio/virtqueue.h
@@ -66,16 +66,15 @@ virtqueue_fetch_flags_packed(struct vring_packed_desc *dp,
 	uint16_t flags;
 
 	if (weak_barriers) {
-/* x86 prefers to using rte_smp_rmb over __atomic_load_n as it reports
+/* x86 prefers to using rte_io_rmb over __atomic_load_n as it reports
  * a better perf(~1.5%), which comes from the saved branch by the compiler.
- * The if and else branch are identical with the smp and io barriers both
- * defined as compiler barriers on x86.
+ * The if and else branch are identical  on the platforms except Arm.
  */
-#ifdef RTE_ARCH_X86_64
-		flags = dp->flags;
-		rte_smp_rmb();
-#else
+#ifdef RTE_ARCH_ARM
 		flags = __atomic_load_n(&dp->flags, __ATOMIC_ACQUIRE);
+#else
+		flags = dp->flags;
+		rte_io_rmb();
 #endif
 	} else {
 		flags = dp->flags;
@@ -90,22 +89,22 @@ virtqueue_store_flags_packed(struct vring_packed_desc *dp,
 			      uint16_t flags, uint8_t weak_barriers)
 {
 	if (weak_barriers) {
-/* x86 prefers to using rte_smp_wmb over __atomic_store_n as it reports
+/* x86 prefers to using rte_io_wmb over __atomic_store_n as it reports
  * a better perf(~1.5%), which comes from the saved branch by the compiler.
- * The if and else branch are identical with the smp and io barriers both
- * defined as compiler barriers on x86.
+ * The if and else branch are identical on the platforms except Arm.
  */
-#ifdef RTE_ARCH_X86_64
-		rte_smp_wmb();
-		dp->flags = flags;
-#else
+#ifdef RTE_ARCH_ARM
 		__atomic_store_n(&dp->flags, flags, __ATOMIC_RELEASE);
+#else
+		rte_io_wmb();
+		dp->flags = flags;
 #endif
 	} else {
 		rte_io_wmb();
 		dp->flags = flags;
 	}
 }
+
 #ifdef RTE_PMD_PACKET_PREFETCH
 #define rte_packet_prefetch(p)  rte_prefetch1(p)
 #else