[dpdk-stable] [PATCH v3] net/iavf: fix virtual channel return value error

[Yahui Cao]

In iavf_handle_virtchnl_msg(), it is not appropriate for _clear_cmd()
to be used as a notification to forground thread. So introduce
_notify_cmd() to fix this error. In addition, since _notify_cmd()
contains rte_wmb(), rte_compiler_barrier() is not necessary.

Sending msg from VF to PF is mainly by calling iavf_execute_vf_cmd(),
the whole virtchnl msg process is like,

iavf_execute_vf_cmd() will call iavf_aq_send_msg_to_pf() to send
msg and then polling the cmd done flag as "if (vf->pend_cmd ==
VIRTCHNL_OP_UNKNOWN)"

When reply msg is returned by pf, iavf_handle_virtchnl_msg() in
isr will read msg return value by "vf->cmd_retval = msg_ret" and
immediately set the cmd done flag by calling _clear_cmd() to
notify the iavf_execute_vf_cmd().

iavf_execute_vf_cmd() find the cmd done flag is set and then
check whether command return value vf->cmd_retval is success or
not.

However _clear_cmd() also resets the vf->cmd_retval to success,
overwriting the actual return value which is used for diagnosis.
So iavf_execute_vf_cmd() will always find vf->cmd_retval is
success and then return success.

Fixes: 22b123a36d07 ("net/avf: initialize PMD")
Cc: stable at dpdk.org

Signed-off-by: Yahui Cao <yahui.cao at intel.com>
---
 drivers/net/iavf/iavf.h       | 11 +++++++++++
 drivers/net/iavf/iavf_vchnl.c |  9 +++------
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/drivers/net/iavf/iavf.h b/drivers/net/iavf/iavf.h
index bbd4d75d0..84f821354 100644
--- a/drivers/net/iavf/iavf.h
+++ b/drivers/net/iavf/iavf.h
@@ -173,6 +173,17 @@ struct iavf_cmd_info {
 	uint32_t out_size;      /* buffer size for response */
 };
 
+/* notify current command done. Only call in case execute
+ * _atomic_set_cmd successfully.
+ */
+static inline void
+_notify_cmd(struct iavf_info *vf, uint32_t msg_ret)
+{
+	vf->cmd_retval = msg_ret;
+	rte_wmb();
+	vf->pend_cmd = VIRTCHNL_OP_UNKNOWN;
+}
+
 /* clear current command. Only call in case execute
  * _atomic_set_cmd successfully.
  */
diff --git a/drivers/net/iavf/iavf_vchnl.c b/drivers/net/iavf/iavf_vchnl.c
index 14395fed3..cf0f6458e 100644
--- a/drivers/net/iavf/iavf_vchnl.c
+++ b/drivers/net/iavf/iavf_vchnl.c
@@ -210,12 +210,9 @@ iavf_handle_virtchnl_msg(struct rte_eth_dev *dev)
 							info.msg_len);
 			} else {
 				/* read message and it's expected one */
-				if (msg_opc == vf->pend_cmd) {
-					vf->cmd_retval = msg_ret;
-					/* prevent compiler reordering */
-					rte_compiler_barrier();
-					_clear_cmd(vf);
-				} else
+				if (msg_opc == vf->pend_cmd)
+					_notify_cmd(vf, msg_ret);
+				else
 					PMD_DRV_LOG(ERR, "command mismatch,"
 						    "expect %u, get %u",
 						    vf->pend_cmd, msg_opc);
-- 
2.17.1