From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35644) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZZv8W-0004Qm-Dn for qemu-devel@nongnu.org; Thu, 10 Sep 2015 02:15:09 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZZv8Q-00044m-Cx for qemu-devel@nongnu.org; Thu, 10 Sep 2015 02:15:08 -0400 Received: from mga09.intel.com ([134.134.136.24]:52333) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZZv8Q-00043Q-1N for qemu-devel@nongnu.org; Thu, 10 Sep 2015 02:15:02 -0400 Date: Thu, 10 Sep 2015 14:18:25 +0800 From: Yuanhan Liu Message-ID: <20150910061825.GR2925@yliu-dev.sh.intel.com> References: <1441697927-16456-1-git-send-email-yuanhan.liu@linux.intel.com> <1441697927-16456-6-git-send-email-yuanhan.liu@linux.intel.com> <55F0F593.9030408@redhat.com> <20150910035702.GP2925@yliu-dev.sh.intel.com> <55F10B08.1060707@redhat.com> <20150910051735.GQ2925@yliu-dev.sh.intel.com> <55F11A9E.8040303@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <55F11A9E.8040303@redhat.com> Subject: Re: [Qemu-devel] [PATCH 5/7] vhost_net: move vhost_net_set_vq_index ahead at vhost_net_init List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jason Wang Cc: mst@redhat.com, qemu-devel@nongnu.org, changchun.ouyang@intel.com On Thu, Sep 10, 2015 at 01:52:30PM +0800, Jason Wang wrote: > > > On 09/10/2015 01:17 PM, Yuanhan Liu wrote: > > On Thu, Sep 10, 2015 at 12:46:00PM +0800, Jason Wang wrote: > >> > > >> > > >> > On 09/10/2015 11:57 AM, Yuanhan Liu wrote: > >>> > > On Thu, Sep 10, 2015 at 11:14:27AM +0800, Jason Wang wrote: > >>>> > >> > >>>> > >> On 09/08/2015 03:38 PM, Yuanhan Liu wrote: > >>>>> > >>> So that we could use the `vq_index' as well in the vhost_net_init > >>>>> > >>> stage, which is required when adding vhost-user multiple-queue support, > >>>>> > >>> where we need the vq_index to indicate which queue pair we are gonna > >>>>> > >>> initiate. > >>>>> > >>> > >>>>> > >>> vhost-user has no multiple queue support yet, hence no queue_index set > >>>>> > >>> before. Here is a quick set to 0 at net_vhost_user_init() stage, and it > >>>>> > >>> will be set properly soon in the next patch. > >>>>> > >>> > >>>>> > >>> Signed-off-by: Yuanhan Liu > >>>>> > >>> --- > >>>>> > >>> hw/net/vhost_net.c | 16 +++++++--------- > >>>>> > >>> net/vhost-user.c | 1 + > >>>>> > >>> 2 files changed, 8 insertions(+), 9 deletions(-) > >>>>> > >>> > >>>>> > >>> diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c > >>>>> > >>> index f9441e9..141b557 100644 > >>>>> > >>> --- a/hw/net/vhost_net.c > >>>>> > >>> +++ b/hw/net/vhost_net.c > >>>>> > >>> @@ -138,6 +138,11 @@ static int vhost_net_get_fd(NetClientState *backend) > >>>>> > >>> } > >>>>> > >>> } > >>>>> > >>> > >>>>> > >>> +static void vhost_net_set_vq_index(struct vhost_net *net, int vq_index) > >>>>> > >>> +{ > >>>>> > >>> + net->dev.vq_index = vq_index; > >>>>> > >>> +} > >>>>> > >>> + > >>>>> > >>> struct vhost_net *vhost_net_init(VhostNetOptions *options) > >>>>> > >>> { > >>>>> > >>> int r; > >>>>> > >>> @@ -167,6 +172,8 @@ struct vhost_net *vhost_net_init(VhostNetOptions *options) > >>>>> > >>> } > >>>>> > >>> net->nc = options->net_backend; > >>>>> > >>> > >>>>> > >>> + vhost_net_set_vq_index(net, net->nc->queue_index * 2); > >>>>> > >>> + > >>>> > >> This breaks vhost kernel multiqueue since queue_index was not > >>>> > >> initialized at this time. > >>> > > Right, thanks for pointing it out. > >>> > > > >>>> > >> We do this in set_netdev() instead of setting > >>>> > >> it in each kind of netdev. > >>> > > Can we move it to net_init_tap() for setting the right queue_index > >>> > > for each nc? > >>> > > > >>> > > Or, can we call vhost_net_set_vq_index twice, one at vhost_net_init(for > >>> > > vhost-user mq support), another one at vhost_net_start(for vhost kernel > >>> > > mq support)? > >>> > > > >>> > > Or, do you have better ideas? > >> > > >> > I think setting queue_index in net_init_tap() looks ok. > > Good to know. > > > >> > But a question > >> > is that why need we do this at so early stage? ( Even before its peers > >> > is connected.) > > For vhost-user multiple queues support, we will invoke vhost_net_init() > > N times for each queue pair, and hence we need to distinguish which > > queue it is while sending messages like VHOST_SET_VRING_CALL for > > initializing corresponding queue pair. > > > > Does that make sense to you? > > > > Not sure. Since current codes works for vhost-kernel. (vhost_net_init() > was also called N times). We don't want to break existed vhost-kernel > API when developing multiqueue. For each virtqueue TX/RX pair, we have > one vhost net device and it has no knowledge for the others (which was > hide by qemu). So VHOST_SET_VRING_CALL works without any change here. > > For the case here, since you still have multiple instances of vhost_net > structure. Maybe the vhost-user backend can distinguish form this? Yeah, I guess that's the difference between vhost-user and vhost-kernel. Vhost-kernel opens a char device(/dev/vhost-net) for each vhost_dev, hence it's distinguishable. But for vhost-user, all vhost_dev share one char device(a socket) for communication, hence, it's not distinguishable. I was thinking maybe we could export vhost_net_set_vq_index() and invoke it at net/vhost-user.c, so that we break nothing, and in the meantime, it keeps the logic inside vhost-user. What do you think? --yliu