We are observing [0] that some of the CSIT VM VHOST tests starts failing after
upgrading of DPDK from version 19.08 to 20.02 in VPP done in [1].

Failing VHOST VM tests with qemu "mrg_rxbuf=off" configured in Qemu cli on VHOST
link between VPP vswitch and VPP NF running in VM of the same version.

VPP inside VM is crashing after several packet recevied. Issue can be solved
just by removing "mrg_buff=off" without any other change to configuration of
VPP.

• Full VM startup logs can be found in [2].
• Full Qemu startup cli can be found in [2].
• Full VPP vswitch configuration can be found in [3].
• Full VPP nf (in VM) configuration can be found in [2] (both startup and running).
• Full PAPI history dump for VPP vswitch can be found in [4].
• Output of "show vhost" can be found in [5].

[0] https://jenkins.fd.io/view/csit/job/csit-vpp-perf-mrr-daily-master/1111/robot/.
[1] https://gerrit.fd.io/r/c/vpp/+/25456.
[2] https://logs.fd.io/production/vex-yul-rot-jenkins-1/csit-vpp-perf-mrr-daily-master/1111/archives/log.html.gz#s1-s1-s1-s7-s2-t1-k3-k6-k2-k1-k1-k3-k1
[3] https://logs.fd.io/production/vex-yul-rot-jenkins-1/csit-vpp-perf-mrr-daily-master/1111/archives/log.html.gz#s1-s1-s1-s7-s2-t1-k2-k5-k1-k1-k1-k1
[4] https://logs.fd.io/production/vex-yul-rot-jenkins-1/csit-vpp-perf-mrr-daily-master/1111/archives/log.html.gz#s1-s1-s1-s7-s2-t1-k3-k2
[5] https://logs.fd.io/production/vex-yul-rot-jenkins-1/csit-vpp-perf-mrr-daily-master/1111/archives/log.html.gz#s1-s1-s1-s7-s2-t1-k3-k6-k2-k1-k1-k1

In case of any question or additional information please contact @csit-dev.

Thank you.