[dpdk-dev] [PATCH] net/vhost: fix segfault when creating vdev dynamically

[Chen, Junjie J]

> 
> 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.

Yes, I agree this. 
In this patch, it just check whether queue is setup or not and give user a chance to setup queue with dev_start, it doesn't revert the logical from previously commit.

So the logical is change to stop creating unix socket before queue setup, what do you think about this? 
> 
> > 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).