Unable to create more than 1 guest virtio-net device using vhost-net backend

Sridhar Samudrala
2010-03-19T22:19:27Z

When creating a guest with 2 virtio-net interfaces, i am running
into a issue causing the 2nd i/f falling back to userpace virtio
even when vhost is enabled.

After some debugging, it turned out that KVM_IOEVENTFD ioctl()
call in qemu is failing with ENOSPC.
This is because of the NR_IOBUS_DEVS(6) limit in kvm_io_bus_register_dev()
routine in the host kernel.

I think we need to increase this limit if we want to support multiple
network interfaces using vhost-net.
Is there an alternate solution?

Thanks
Sridhar