From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: Unable to create more than 1 guest virtio-net device using vhost-net backend Date: Sun, 21 Mar 2010 11:55:44 +0200 Message-ID: <20100321095544.GA6443@redhat.com> References: <1269037167.5127.12.camel@w-sridhar.beaverton.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev , "kvm@vger.kernel.org" , avi@redhat.com, gleb@redhat.com To: Sridhar Samudrala Return-path: Received: from mx1.redhat.com ([209.132.183.28]:9258 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751993Ab0CUJ7M (ORCPT ); Sun, 21 Mar 2010 05:59:12 -0400 Content-Disposition: inline In-Reply-To: <1269037167.5127.12.camel@w-sridhar.beaverton.ibm.com> Sender: netdev-owner@vger.kernel.org List-ID: 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. -- MST