From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Tan, Jianfeng" Subject: Re: [PATCH 2/3] net/virtio_user: fix wrong sequence of messages Date: Tue, 6 Sep 2016 15:54:30 +0800 Message-ID: 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=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: dev@dpdk.org, zhihong.wang@intel.com, lining18@jd.com To: Yuanhan Liu Return-path: Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by dpdk.org (Postfix) with ESMTP id 4AA195901 for ; Tue, 6 Sep 2016 09:54:34 +0200 (CEST) In-Reply-To: <20160906064246.GQ30752@yliu-dev.sh.intel.com> 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" 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(). > > 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? > >> - 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? Thanks, Jianfeng > > --yliu