From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: Unable to create more than 1 guest virtio-net device using vhost-net backend Date: Sun, 21 Mar 2010 12:11:33 +0200 Message-ID: <4BA5F0D5.6020801@redhat.com> References: <1269037167.5127.12.camel@w-sridhar.beaverton.ibm.com> <20100321095544.GA6443@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Sridhar Samudrala , netdev , "kvm@vger.kernel.org" , gleb@redhat.com To: "Michael S. Tsirkin" Return-path: In-Reply-To: <20100321095544.GA6443@redhat.com> Sender: kvm-owner@vger.kernel.org List-Id: netdev.vger.kernel.org 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