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From: Maxime Coquelin <maxime.coquelin@redhat.com>
To: "Tan, Jianfeng" <jianfeng.tan@intel.com>,
	"Chen, Junjie J" <junjie.j.chen@intel.com>,
	"mtetsuyah@gmail.com" <mtetsuyah@gmail.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH] net/vhost: fix segfault when creating vdev dynamically
Date: Tue, 27 Mar 2018 13:28:11 +0200	[thread overview]
Message-ID: <c10fca40-a071-8678-4d25-88a468fe1eb8@redhat.com> (raw)
In-Reply-To: <bccc2fd8-867a-266e-7c99-8e5bbd79673e@intel.com>



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).
> 

  parent reply	other threads:[~2018-03-27 11:28 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-03-27 16:05 Junjie Chen
2018-03-27  8:56 ` Tan, Jianfeng
2018-03-27  9:02   ` Chen, Junjie J
2018-03-27  9:10     ` Tan, Jianfeng
2018-03-27  9:24       ` Chen, Junjie J
2018-03-27  9:42         ` Tan, Jianfeng
2018-03-27 10:18           ` Chen, Junjie J
2018-03-27 13:54             ` Tan, Jianfeng
2018-03-27 11:28           ` Maxime Coquelin [this message]
2018-03-27 14:01             ` Tan, Jianfeng
2018-03-29 12:35               ` Maxime Coquelin
2018-03-29 15:35 ` [dpdk-dev] [PATCH v2] " Junjie Chen
2018-03-29 13:16   ` Maxime Coquelin
2018-03-30  6:58   ` [dpdk-dev] [PATCH v3] " Junjie Chen
2018-03-30  7:32     ` Yang, Zhiyong
2018-03-30  7:36       ` Maxime Coquelin
2018-03-30  7:35     ` Maxime Coquelin
2018-03-30  7:43     ` Maxime Coquelin
2018-04-09 12:37     ` Jens Freimann
2018-04-10  8:11       ` Chen, Junjie J

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