From 3b066930ac02a483540050e84d4caa2ac581409c Mon Sep 17 00:00:00 2001
From: Changpeng Liu <changpeng.liu@intel.com>
Date: Thu, 13 Jan 2022 21:28:31 +0800
Subject: [PATCH] nvmf/vfio-user: add memory barrier after posting a completion

We met an issue that client got a NVMe completion with old SC
bit, so we add a memory barrier here to ensure the NVMe completion
is fully populated.

Fix issue #2323.

Change-Id: I7887d789a0acd3634a10aa7dc8de81a153137ae7
Signed-off-by: Changpeng Liu <changpeng.liu@intel.com>
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/11076
Community-CI: Broadcom CI <spdk-ci.pdl@broadcom.com>
Community-CI: Mellanox Build Bot
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: John Levon <levon@movementarian.org>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
---
 lib/nvmf/vfio_user.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/nvmf/vfio_user.c b/lib/nvmf/vfio_user.c
index 1102076fd..a86541647 100644
--- a/lib/nvmf/vfio_user.c
+++ b/lib/nvmf/vfio_user.c
@@ -939,9 +939,11 @@ post_completion(struct nvmf_vfio_user_ctrlr *ctrlr, struct nvme_q *cq,
 	cpl->status.dnr = 0x0;
 	cpl->status.m = 0x0;
 	cpl->status.sct = sct;
-	cpl->status.p = cq->phase;
 	cpl->status.sc = sc;
+	cpl->status.p = cq->phase;
 
+	/* Ensure the Completion Queue Entry is visible. */
+	spdk_wmb();
 	cq_tail_advance(cq);
 
 	/*