[dpdk-dev] net/netvsc: subchannel configuration failed due to unexpected NVS response

[Min Tang]

Hi Stephen:

I saw the following error messages when using DPDK 18.11.2 in Azure:

hn_nvs_execute(): unexpected NVS resp 0x6b, expect 0x85
hn_dev_configure(): subchannel configuration failed

It was not easy to reproduce it and it only occurred with multiple queues
enabled. In hn_nvs_execute it expects the response to match the request. In
the failed case, it was expecting NVS_TYPE_SUBCH_REQ (133 or 0x85) but
got NVS_TYPE_RNDIS(107 or 0x6b). Obviously somewhere the NVS_TYPE_RNDIS
message had been sent before the NVS_TYPE_SUBCH_REQ message was sent.  I
looked at the code and found that the NVS_TYPE_RNDIS message needs
completion response but it does not receive the response message anywhere.
The fix would be receiving and discarding the wrong response message(s).

I put the following patches and it has fixed the problem.

--- a/drivers/net/netvsc/hn_nvs.c 2020-02-27 11:08:29.755530969 -0500
+++ b/drivers/net/netvsc/hn_nvs.c 2020-02-27 11:07:21.567371798 -0500
@@ -92,7 +92,7 @@
  if (hdr->type != type) {
  PMD_DRV_LOG(ERR, "unexpected NVS resp %#x, expect %#x",
     hdr->type, type);
- goto retry;
+ return -EINVAL;
  }

  if (len < resplen) {