From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57605) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YxrXE-0005Hp-LP for qemu-devel@nongnu.org; Thu, 28 May 2015 02:43:21 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YxrXA-0002xq-Fw for qemu-devel@nongnu.org; Thu, 28 May 2015 02:43:20 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54253) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YxrXA-0002xc-Aj for qemu-devel@nongnu.org; Thu, 28 May 2015 02:43:16 -0400 Message-ID: <5566B8FF.7060905@redhat.com> Date: Thu, 28 May 2015 14:43:11 +0800 From: Jason Wang MIME-Version: 1.0 References: <1425880835-13230-1-git-send-email-pagupta@redhat.com> <314829841.4949261.1432708003823.JavaMail.zimbra@redhat.com> <5565842E.9020901@redhat.com> <20150527135639-mutt-send-email-mst@redhat.com> <5566899C.2030708@redhat.com> <55668D46.9090204@redhat.com> <5566B572.1020008@redhat.com> In-Reply-To: <5566B572.1020008@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] net: Remove vhostforce option in addition to vhost parameter List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Michal Privoznik , "Michael S. Tsirkin" Cc: Pankaj Gupta , qemu-devel@nongnu.org, aliguori@amazon.com On 05/28/2015 02:28 PM, Michal Privoznik wrote: > On 28.05.2015 05:36, Jason Wang wrote: >> >> On 05/28/2015 11:21 AM, Jason Wang wrote: >>> On 05/27/2015 07:57 PM, Michael S. Tsirkin wrote: >>>> On Wed, May 27, 2015 at 04:45:34PM +0800, Jason Wang wrote: >>>>>> On 05/27/2015 02:26 PM, Pankaj Gupta wrote: >>>>>>>> Ping. >>>>>>>> >>>>>>>> Can I get any suggestions on this patch. >>>>>>>> >>>>>>>> Best regards, >>>>>>>> Pankaj >>>>>>>> >>>>>>>>>> vhostforce was added to enable vhost when >>>>>>>>>> guest don't have MSI-X support. >>>>>>>>>> Now, we have scenarios like DPDK in Guest which dont use >>>>>>>>>> interrupts and still use vhost. Also, performance of guests >>>>>>>>>> without MSI-X support is getting less popular. >>>>>>>>>> >>>>>>>>>> Its OK to remove this extra option and enable vhost >>>>>>>>>> on the basis of vhost=ON/OFF. >>>>>>>>>> Done basic testing with vhost on/off for latest guests >>>>>>>>>> and old guests(non-msix). >>>>>>>>>> >>>>>>>>>> Signed-off-by: Pankaj Gupta >>>>>> Looks good. Two questions: >>>>>> >>>>>> - Did libvirt use this? if not, we may want to drop vhostfore option >>>>>> completely. >>>> Yes, it did. >>>> >>> For vhost-user, vhostforce is mandatory. But how about tap? Looks like >>> it was not used, and I could not even find any option in >>> http://libvirt.org/formatdomain.html. >>> >> CC Michal for the answer. >> > No, vhostforce is not used by libvirt at all. Which brings up > interesting question: for vhost-user libvirt constructs merely the > follwing cmd line: > > -chardev socket,id=charnet0,path=/tmp/vhost0.sock,server \ > -netdev type=vhost-user,id=hostnet0,chardev=charnet0 \ > > How does vhostforce fit in? I suppose the cmd line is working even > without libvirt passing vhostforce. Should it do so? Without this patch, it works with normal virtio-net drivers but may not work for guest pmd. Since pmd does not use MSI-X interrupts, so qemu won't start vhost_net. So libvirt needs vhostforce for vhost-user. With this patch, libvirt does not need to care about this. > > Michal >