[ovs-dev] Vhostports drop issue - related to MTU - Qemu version

Kapil Adhikesavalu kapil20084 at gmail.com
Wed Oct 26 13:11:07 UTC 2016


Hi,

Issue Setup:  DPDK 16.07 + OVS 2.6.0 + qemu 2.4.1 : PHY-VM-PHY

I am trying to upgrade from (DPDK16.04 + OVS2.5.9), to (DPDK16.07 +
OVS2.6.0) for jumbo frame support. After the upgrade, all packets are
getting dropped on the vhostuser port.
The dpdk/vhost user ports used here has default MTU of 1500 and packets are
within the MTU size.

Upon few trails, i found configuring the mtu on the vhostuser port is
somehow fixing the drop issue. Command used : ovs-vsctl set interface
vhostuser1 mtu_request=1400(to any value works).
Though even with this, if i reboot the VM, again the drop issue shows up
and mtu has to be reconfigured/changed on the vhost to get the traffic
working.
Seems, modifying the mtu value on vhost is internally triggering something
which resolves the drop issue.

I upgraded the qemu to 2.6.2, which resolves the drop issue in the vhost
ports without any changes to default MTU.
I suspect, if its some interop issue with qemu 2.4.1, after the addition of
jumbo frame support in OVS 2.6.0.

Some input on how to debug this will help. is there any dependency on
dpdk+ovs version with qemu version ?

i wanted to try dpdk or ovs upgrade alone, instead of both, but it has some
build dependencies, so i can't try that.

My earlier mail on this issue - https://www.mail-archive.
com/dev at openvswitch.org/msg71381.html .

Regards
Kapil.



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