[dpdk-dev] [PATCH] ethdev: fix wrong memset

[Yuanhan Liu]

On Mon, Jan 23, 2017 at 12:44:11PM +0000, Ananyev, Konstantin wrote:
> > On Mon, Jan 23, 2017 at 07:40:50PM +0800, Yuanhan Liu wrote:
> > > On Mon, Jan 23, 2017 at 11:32:23AM +0000, Ferruh Yigit wrote:
> > > > On 1/23/2017 11:24 AM, Yuanhan Liu wrote:
> > > > > On Mon, Jan 23, 2017 at 11:05:25AM +0000, Ferruh Yigit wrote:
> > > > >>>>>>>>  lib/librte_ether/rte_ethdev.c | 2 +-
> > > > >>>>>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > >>>>>>>>
> > > > >>>>>>>> diff --git a/lib/librte_ether/rte_ethdev.c b/lib/librte_ether/rte_ethdev.c
> > > > >>>>>>>> index 4790faf..61f44e2 100644
> > > > >>>>>>>> --- a/lib/librte_ether/rte_ethdev.c
> > > > >>>>>>>> +++ b/lib/librte_ether/rte_ethdev.c
> > > > >>>>>>>> @@ -225,7 +225,7 @@ struct rte_eth_dev *
> > > > >>>>>>>>  		return NULL;
> > > > >>>>>>>>  	}
> > > > >>>>>>>>
> > > > >>>>>>>> -	memset(&rte_eth_devices[port_id], 0, sizeof(*eth_dev->data));
> > > > >>>>>>>> +	memset(&rte_eth_dev_data[port_id], 0, sizeof(struct rte_eth_dev_data));
> > > > >>>>>>>
> > > > >>>>>>> Not directly related to the this issue, but, after fix, this may have
> > > > >>>>>>> issues with secondary process.
> > > > >>>>>>>
> > > > >>>>>>> There were patches sent to fix this.
> > > > >>>>>>
> > > > >>>>>> I mean this one:
> > > > >>>>>> http://dpdk.org/ml/archives/dev/2017-January/054422.html
> > > > >>>>>
> > > > >>>>> d948f596fee2 ("ethdev: fix port data mismatched in multiple process
> > > > >>>>> model") should have fixed it.
> > > > >>>>
> > > > >>>> Think about case, where secondary process uses a virtual PMD, which does
> > > > >>>> a rte_eth_dev_allocate() call, shouldn't this corrupt primary process
> > > > >>>> device data?
> > > > >>>
> > > > >>> Yes, it may. However, I doubt that's the typical usage.
> > > > >>
> > > > >> But this is a use case, and broken now,
> > > > >
> > > > > I thought it was broken since the beginning?
> > > >
> > > > No, memset(&rte_eth_dev_data[port_id], ...) breaks it.
> > >
> > > Oh, you were talking about that particular case Remy's patch meant to
> > > fix.
> > >
> > > > >> and fix is known.
> > > > >
> > > > > And there is already a fix?
> > > >
> > > > http://dpdk.org/ml/archives/dev/2017-January/054422.html
> > >
> > > Yes, it should fix that issue.
> > 
> > Well, few more thoughts: it may fix the crash issue Remy saw, but it
> > looks like more a workaround to me. Basically, if primary and secondary
> > shares a same port id, they should point to same device. Otherwise,
> > primary process may use eth_dev->data for a device A, while the
> > secondary process may use it for another device, as you said, it
> > could be a vdev.
> > 
> > In such case, there is no way we could continue safely. That said,
> > the given patch avoids the total reset of eth_dev->data, while it
> > continues reset the eth_dev->data->name, which is wrong.
> > 
> > So it's not a proper fix.
> > 
> > Again, I think it's more about the usage. If primary starts with
> > a nic device A, while the secondary starts with a nic device B,
> > there is no way they could work well (unless they use different
> > port id).
> 
> Why not?
> I think this is possible.

Yes, it's possible: find another port id if that one is already taken
by primary process (or even by secondary process: think that primary
process might attatch a port later).

> They just need to be initialized properly,
> so each rte_eth_devices[port_id]->data, etc. point to the right place.

My understanding is, as far as they use different port_id, it might
be fine. Just not sure it's enough or not.

	--yliu