can STP (spanning tree) be disable on KVM vms ?

Hi all:
We have several VMS on our RedHat 6.8 server running; they use a trunk link ( 2 x 10GEports) using bridges. The server is linked to two FEX (Cisco Nexus Extenders UP). It's common knowledge that FEX don't do STP, but seems that it depends on the NX-OS version,
This server was working with those FEX and bridged VMS using STP over 9 months.
Recently the FEX OS was upgraded to the last version and reinforces no STP limitation, so our VMS communications stopped.
We tried to disable STP on the RedHat nics and trunk, but found no information about it can disable STP on the VMS.
So this my questions are:
a) can STP be disabled at VMS level?
b) if not; there is another way to use the trunk without bridges?

Thanks a lot!