[PATCH v1 5/5] idpf: warn on possible ctlq overflow

[Manoj Vishwanathan]

From: Willem de Bruijn <willemb@xxxxxxxxxx>

The virtchannel control queue is lossy to avoid deadlock. Ensure that
no losses occur in practice. Detect a full queue, when overflows may
have happened.

In practice, virtchnl is synchronous currenty and messages generally
take a single slot. Using up anywhere near the full ring is not
expected.

Tested: Running several traffic tests and no logs seen in the dmesg

Signed-off-by: Willem de Bruijn <willemb@xxxxxxxxxx>
Signed-off-by: Manoj Vishwanathan <manojvishy@xxxxxxxxxx>
---
 drivers/net/ethernet/intel/idpf/idpf_virtchnl.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c b/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
index 07239afb285e..1852836d81e4 100644
--- a/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
+++ b/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
@@ -218,6 +218,15 @@ static int idpf_mb_clean(struct idpf_adapter *adapter)
 	if (err)
 		goto err_kfree;
 
+	/* Warn if messages may have been dropped */
+	if (num_q_msg == IDPF_DFLT_MBX_Q_LEN) {
+		static atomic_t mbx_full = ATOMIC_INIT(0);
+		int cnt;
+
+		cnt = atomic_inc_return(&mbx_full);
+		net_warn_ratelimited("%s: ctlq full (%d)\n", __func__, cnt);
+	}
+
 	for (i = 0; i < num_q_msg; i++) {
 		if (!q_msg[i])
 			continue;
-- 
2.46.0.76.ge559c4bf1a-goog