From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:35108) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ui369-00083h-V2 for qemu-devel@nongnu.org; Thu, 30 May 2013 09:41:02 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Ui365-00025N-9v for qemu-devel@nongnu.org; Thu, 30 May 2013 09:40:57 -0400 Received: from mail-gh0-x22f.google.com ([2607:f8b0:4002:c05::22f]:60574) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ui364-00025D-PM for qemu-devel@nongnu.org; Thu, 30 May 2013 09:40:53 -0400 Received: by mail-gh0-f175.google.com with SMTP id z19so4127ghb.6 for ; Thu, 30 May 2013 06:40:52 -0700 (PDT) From: Anthony Liguori In-Reply-To: References: <20130523085034.GA16142@redhat.com> <519F35B7.6010408@redhat.com> <20130524113542.GA7046@redhat.com> <8738tctrox.fsf@codemonkey.ws> <20130524140024.GA12024@redhat.com> <87li6yodgq.fsf@rustcorp.com.au> <87k3miq6sw.fsf@codemonkey.ws> <87r4gpkplc.fsf@rustcorp.com.au> Date: Thu, 30 May 2013 08:40:47 -0500 Message-ID: <87k3mg60ww.fsf@codemonkey.ws> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Subject: Re: [Qemu-devel] updated: kvm networking todo wiki List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi , Rusty Russell Cc: kvm , "Michael S. Tsirkin" , netdev@vger.kernel.org, Jason Wang , qemu-devel , Linux Virtualization , herbert@gondor.hengli.com.au, Dmitry Fleytman Stefan Hajnoczi writes: > On Thu, May 30, 2013 at 7:23 AM, Rusty Russell wrote: >> Anthony Liguori writes: >>> Rusty Russell writes: >>>> On Fri, May 24, 2013 at 08:47:58AM -0500, Anthony Liguori wrote: >>>>> FWIW, I think what's more interesting is using vhost-net as a networking >>>>> backend with virtio-net in QEMU being what's guest facing. >>>>> >>>>> In theory, this gives you the best of both worlds: QEMU acts as a first >>>>> line of defense against a malicious guest while still getting the >>>>> performance advantages of vhost-net (zero-copy). >>>>> >>>> It would be an interesting idea if we didn't already have the vhost >>>> model where we don't need the userspace bounce. >>> >>> The model is very interesting for QEMU because then we can use vhost as >>> a backend for other types of network adapters (like vmxnet3 or even >>> e1000). >>> >>> It also helps for things like fault tolerance where we need to be able >>> to control packet flow within QEMU. >> >> (CC's reduced, context added, Dmitry Fleytman added for vmxnet3 thoughts). >> >> Then I'm really confused as to what this would look like. A zero copy >> sendmsg? We should be able to implement that today. >> >> On the receive side, what can we do better than readv? If we need to >> return to userspace to tell the guest that we've got a new packet, we >> don't win on latency. We might reduce syscall overhead with a >> multi-dimensional readv to read multiple packets at once? > > Sounds like recvmmsg(2). Could we map this to mergable rx buffers though? Regards, Anthony Liguori > > Stefan