From b63ad2eec0de94a5e6393baa7630fc3c3866f7ce Mon Sep 17 00:00:00 2001
From: Ben Walker <benjamin.walker@intel.com>
Date: Mon, 18 Mar 2019 11:23:21 -0700
Subject: [PATCH] nvme: Don't do a write memory barrier if we don't ring the
 doorbell

Change-Id: I6766ae96c155e04bc0162aa8d2e21fd096be3221
Signed-off-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-on: https://review.gerrithub.io/c/spdk/spdk/+/448310
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Changpeng Liu <changpeng.liu@intel.com>
---
 lib/nvme/nvme_pcie.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/nvme/nvme_pcie.c b/lib/nvme/nvme_pcie.c
index 6bf282a0d..2837c46a5 100644
--- a/lib/nvme/nvme_pcie.c
+++ b/lib/nvme/nvme_pcie.c
@@ -1195,11 +1195,11 @@ nvme_pcie_qpair_submit_tracker(struct spdk_nvme_qpair *qpair, struct nvme_tracke
 		SPDK_ERRLOG("sq_tail is passing sq_head!\n");
 	}
 
-	spdk_wmb();
 	if (spdk_likely(nvme_pcie_qpair_update_mmio_required(qpair,
 			pqpair->sq_tail,
 			pqpair->sq_shadow_tdbl,
 			pqpair->sq_eventidx))) {
+		spdk_wmb();
 		g_thread_mmio_ctrlr = pctrlr;
 		spdk_mmio_write_4(pqpair->sq_tdbl, pqpair->sq_tail);
 		g_thread_mmio_ctrlr = NULL;