From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: updated: kvm networking todo wiki Date: Thu, 30 May 2013 16:44:49 +0300 Message-ID: <20130530134449.GA31649@redhat.com> 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> <87k3mg60ww.fsf@codemonkey.ws> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm , qemu-devel , Linux Virtualization , herbert@gondor.hengli.com.au, netdev@vger.kernel.org To: Anthony Liguori Return-path: Content-Disposition: inline In-Reply-To: <87k3mg60ww.fsf@codemonkey.ws> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org List-Id: netdev.vger.kernel.org On Thu, May 30, 2013 at 08:40:47AM -0500, Anthony Liguori wrote: > 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 Yes because we don't have to complete buffers in order. > > > > Stefan From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:36385) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ui39r-0002ii-6Y for qemu-devel@nongnu.org; Thu, 30 May 2013 09:44:54 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Ui39k-00040T-NG for qemu-devel@nongnu.org; Thu, 30 May 2013 09:44:47 -0400 Received: from mx1.redhat.com ([209.132.183.28]:10361) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ui39k-0003zy-ER for qemu-devel@nongnu.org; Thu, 30 May 2013 09:44:40 -0400 Date: Thu, 30 May 2013 16:44:49 +0300 From: "Michael S. Tsirkin" Message-ID: <20130530134449.GA31649@redhat.com> 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> <87k3mg60ww.fsf@codemonkey.ws> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87k3mg60ww.fsf@codemonkey.ws> Subject: Re: [Qemu-devel] updated: kvm networking todo wiki List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: kvm , Stefan Hajnoczi , Jason Wang , Rusty Russell , qemu-devel , Linux Virtualization , herbert@gondor.hengli.com.au, netdev@vger.kernel.org, Dmitry Fleytman On Thu, May 30, 2013 at 08:40:47AM -0500, Anthony Liguori wrote: > 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 Yes because we don't have to complete buffers in order. > > > > Stefan