From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Tan, Jianfeng" Subject: Re: [PATCH] net/vhost: fix segfault when creating vdev dynamically Date: Tue, 27 Mar 2018 22:01:21 +0800 Message-ID: <45023f15-9ddd-ec64-8e06-bef74c2ca533@intel.com> 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: 7bit Cc: "dev@dpdk.org" To: Maxime Coquelin , "Chen, Junjie J" , "mtetsuyah@gmail.com" Return-path: Received: from mga18.intel.com (mga18.intel.com [134.134.136.126]) by dpdk.org (Postfix) with ESMTP id 8B43D4CBB for ; Tue, 27 Mar 2018 16:01:24 +0200 (CEST) In-Reply-To: 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 3/27/2018 7:28 PM, Maxime Coquelin wrote: > > > 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. Yes, I have noticed that this issue mostly happens at dynamic case. Just try to suggest a proper way to fix. Please check if my suggestion in another email makes sense. Thanks, Jianfeng > > Cheers, > Maxime