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

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On 03/21/2010 11:55 AM, Michael S. Tsirkin wrote:
On Fri, Mar 19, 2010 at 03:19:27PM -0700, Sridhar Samudrala wrote:
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
Nothing easy that I can see. Each device needs 2 of these.  Avi, Gleb,
any objections to increasing the limit to say 16?  That would give us
5 more devices to the limit of 6 per guest.

Increase it to 200, then.

Is the limit visible to userspace?  If not, we need to expose it.

--
error compiling committee.c: too many arguments to function

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