From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yuanhan Liu Subject: Re: [PATCH 2/3] net/virtio_user: fix wrong sequence of messages Date: Tue, 6 Sep 2016 16:20:11 +0800 Message-ID: <20160906082011.GA23158@yliu-dev.sh.intel.com> References: <1470397003-5782-1-git-send-email-jianfeng.tan@intel.com> <1470397003-5782-3-git-send-email-jianfeng.tan@intel.com> <20160906064246.GQ30752@yliu-dev.sh.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: dev@dpdk.org, zhihong.wang@intel.com, lining18@jd.com To: "Tan, Jianfeng" Return-path: Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by dpdk.org (Postfix) with ESMTP id 6FF8B5934 for ; Tue, 6 Sep 2016 10:08:06 +0200 (CEST) Content-Disposition: inline In-Reply-To: List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On Tue, Sep 06, 2016 at 03:54:30PM +0800, Tan, Jianfeng wrote: > Hi Yuanhan, > > > On 9/6/2016 2:42 PM, Yuanhan Liu wrote: > >On Fri, Aug 05, 2016 at 11:36:42AM +0000, Jianfeng Tan wrote: > >>When virtio_user is used with VPP's native vhost user, it cannot > >>send/receive any packets. > >> > >>The root cause is that vpp-vhost-user translates the message > >>VHOST_USER_SET_FEATURES as puting this device into init state, > >>aka, zero all related structures. However, previous code > >>puts this message at last in the whole initialization process, > >>which leads to all previous information are zeroed. > >> > >>To fix this issue, we rearrange the sequence of those messages. > >> - step 0, send VHOST_USER_SET_VRING_CALL so that vhost allocates > >> virtqueue structures; > >Yes, it is. However, it's not that right to do that (you see there is > >a FIXME in vhost_user_set_vring_call()). > > I suppose you are specifying vhost_set_vring_call(). Oh, I was talking about the new code: I have renamed it to vhost_user_set_vring_call :) > > > >That means it need be fixed: we should not rely on fact that it's the > >first per-vring message we will get in the current QEMU implementation > >as the truth. > > > >That also means, naming a function like virtio_user_create_queue() based > >on above behaviour is wrong. > > It's actually a good catch. After a light thought, I think in DPDK vhost, we > may need to create those virtqueues once unix socket gets connected, just > like in vhost-net, virtqueues are created on char file open. Right? There is a difference: for vhost-net and tap mode, IIRC, it knows how many queues before doing setup. While for vhost-user, it doesn't. That means, we have to allocate and setup virtqueues reactively: just like what we have done in vhost_set_vring_call(). What doesn't look perfect is it assume SET_VRING_CALL is the first per-vring message we will get. > > > > >> - step 1, send VHOST_USER_SET_FEATURES to confirm the features; > >> - step 2, send VHOST_USER_SET_MEM_TABLE to share mem regions; > >> - step 3, send VHOST_USER_SET_VRING_NUM, VHOST_USER_SET_VRING_BASE, > >> VHOST_USER_SET_VRING_ADDR, VHOST_USER_SET_VRING_KICK for each > >> queue; > >> - ... > >> > >>Fixes: 37a7eb2ae816 ("net/virtio-user: add device emulation layer") > >> > >>Reported-by: Zhihong Wang > >>Signed-off-by: Jianfeng Tan > >>--- > >> drivers/net/virtio/virtio_user/virtio_user_dev.c | 120 ++++++++++++++--------- > >> 1 file changed, 72 insertions(+), 48 deletions(-) > >That's too much of code for a bug fix. I'm wondering how about just > >moving VHOST_USER_GET_PROTOCOL_FEATURES ahead, to the begining of > >virtio_user_start_device()? It should fix this issue. > > Why does VHOST_USER_GET_PROTOCOL_FEATURES care? Do you mean shifting > VHOST_USER_SET_FEATURES earlier? Oops, right, I meant SET_FEATURES. Sorry about confusion introduced by the silly auto-completion. --yliu