-----Original Message-----
From: Yuanhan Liu [mailto:yuanhan.liu@linux.intel.com]
Sent: Monday, January 23, 2017 12:53 PM
To: Ananyev, Konstantin <redacted>
Cc: Yigit, Ferruh <redacted>; dev@dpdk.org; Thomas Monjalon <redacted>; Horton, Remy
[off-list ref]
Subject: Re: [dpdk-dev] [PATCH] ethdev: fix wrong memset

On Mon, Jan 23, 2017 at 12:44:11PM +0000, Ananyev, Konstantin wrote:

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On Mon, Jan 23, 2017 at 07:40:50PM +0800, Yuanhan Liu wrote:

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On Mon, Jan 23, 2017 at 11:32:23AM +0000, Ferruh Yigit wrote:

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On 1/23/2017 11:24 AM, Yuanhan Liu wrote:

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On Mon, Jan 23, 2017 at 11:05:25AM +0000, Ferruh Yigit wrote:

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 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.

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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).

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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.

As I understand, the main problem is that  rte_eth_devices[] is local,
while rte_eth_dev_data points to the shared memory array.
And rte_eth_dev_allocate() assumes that if rte_eth_devices[x] is free,
then rte_eth_dev_data[port_id] is also free.
Which is wrong in case when primary/secondary processes have different devices attached.
Another problem is that inside rte_ethdev.c we manipulate rte_eth_dev_data[]
contents without grabbing any lock.
I think it was an attempt to fix that issue in 16.07 timeframe or so,
but I don't remember what happened with that patch.
Konstantin