From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maxime Coquelin Subject: Re: [PATCH] net/vhost: fix segfault when creating vdev dynamically Date: Tue, 27 Mar 2018 13:28:11 +0200 Message-ID: References: <1522166726-42025-1-git-send-email-junjie.j.chen@intel.com> <20388d18-796f-7dd5-e596-f8cc290063d0@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 8bit Cc: "dev@dpdk.org" To: "Tan, Jianfeng" , "Chen, Junjie J" , "mtetsuyah@gmail.com" Return-path: Received: from mx1.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by dpdk.org (Postfix) with ESMTP id 5ABD41E35 for ; Tue, 27 Mar 2018 13:28:14 +0200 (CEST) In-Reply-To: Content-Language: en-US List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On 03/27/2018 11:42 AM, Tan, Jianfeng wrote: > > > On 3/27/2018 5:24 PM, Chen, Junjie J wrote: >>>>> On 3/28/2018 12:05 AM, Junjie Chen wrote: >>>>>> when creating vdev dynamically, vhost pmd driver start directly >>>>>> without checking TX/RX queues ready or not, and thus cause >>>>>> segmentation fault when vhost library accessing queues. This patch >>>>>> add flag to check whether queues setup or not, and add driver start >>>>>> call into dev_start to allow user start it after setting up queue. >>>>> The issue is clear now. But this patch just puts the situation >>>>> before below >>> fix: >>>>> "it doesn't create the actual datagram socket until you call >>>>> .dev_start()." >>>> No, if the queue exist, the datagram socket still get created in >>>> vhost_create >>> API, since the vhost_driver_register still exist in vhost_create. >>> >>> The queue can never be created, as it's still not probed. >> I think we need to separate this into two cases: >>     Statically create vdev, the datagram recreate logical is still >> there since queues are exist already, this patch doesn't change anything. >>     Dynamic create vdev, as you pointed out, queue can never be >> created, while this should be not valid since In normal process of >> creating vdev dynamically, we always need to config queues. Correct me >> if I'm wrong. > > My point is, either vdev is created statically or dynamically, when > probe(), queues are not setup yet definitely, then *the unix socket will > not be created* until we set up the queues and do dev_start(). If the > unix socket is not created, then VM cannot connect to it. FYI, I think I reproduced such an issue with the vdev statically created in the past, while doing some experiments. I didn't went further into the analysis at that time, but it looks like the issue Junjie is trying to address with this patch for dynamically created vdev. Cheers, Maxime >> In summary, I think the previously commit fixes the static code path >> and this patch fixes the dynamic code path (we need to at least setup >> queue once). >