DPDK:20.11.1: net/ena crash while fetching xstats

[Amiya Mohakud]

Hi Stephen and Michal

Thanks a lot for all the discussions and progress made on this.Appreciate
it.
Sorry for the late reply. To answer your questions:


*1. Is the application you're using the single-process or multiprocess?If
so, from which process are you probing for the xstats?*
>> System has both primary and secondary processes running. but the stats
are being fetched from the* primary process* only. I'm not sure if the
presence of secondary processes is causing the crash even if we try to
fetch stats from the primary process. Can we confirm this from the code?

*2. Have you tried running latest DPDK v20.11 LTS?*
*>> *It's DPDK v20.11.1. Did not try with the latest 20.11 LTS.

3. What kernel module are you using (igb_uio/vfio-pci)?
>> It's igb_uio.

4. On what AWS instance type it was reproduced?
>> It's c5n.2xlarge. ( 8 cores. 1 primary process and 6 secondary
processes.)

5. Is the Seg Fault happening the first time you call for the xstats?
>> Yes. That's correct.

Regards
Amiya



On Wed, Apr 20, 2022 at 4:39 AM Stephen Hemminger <
stephen at networkplumber.org> wrote:

> On Tue, 19 Apr 2022 22:27:32 +0200
> Michał Krawczyk <mk at semihalf.com> wrote:
>
> > Thanks Stephen, indeed the issue reproduces in the secondary process.
> >
> > Basically ENA v2.2.1 is not MP aware, meaning it cannot be used safely
> > from the secondary process. The main obstacle is the admin queue which
> > is used for processing the hardware requests which can be used safely
> > only from the primary process. It's not strictly a bug, as we weren't
> > exposing 'MP Awareness' in the PMD features list, it's more like a
> > lack of proper MP support.
> >
> > The latest ENA PMD release should be MP safe. We currently don't have
> > PMD backport ready for the older LTS release (but we're planning to do
> > so for ENA v2.6.0 on the amzn-drivers repository:
> >
> https://urldefense.com/v3/__https://github.com/amzn/amzn-drivers/tree/master/userspace/dpdk__;!!Mt_FR42WkD9csi9Y!ZAgIa147k7j0wwnu83K-vq8T9bH0gWwoldqHg9IshR1CSkTYpJOLzT35FhtlVPDkWbN9CZMv469Jj68fwxrqFsQQErwYHNc$
> ).
>
> I wish that ENA did not have its own versioning scheme.
> Driver versions are meaningful only to the driver writer/vendor, they
> don't help the end user.
>
> Since backporting is not part of stable process. I suggest doing what
> XDP did for 21.11 and earlier releases.
>
> diff --git a/drivers/net/ena/ena_ethdev.c b/drivers/net/ena/ena_ethdev.c
> index 634c97acf60d..3778349f3fe9 100644
> --- a/drivers/net/ena/ena_ethdev.c
> +++ b/drivers/net/ena/ena_ethdev.c
> @@ -3212,6 +3212,12 @@ static int ena_rx_queue_intr_disable(struct
> rte_eth_dev *dev,
>  static int eth_ena_pci_probe(struct rte_pci_driver *pci_drv __rte_unused,
>         struct rte_pci_device *pci_dev)
>  {
> +       if (rte_eal_process_type() == RTE_PROC_SECONDARY) {
> +               PMD_INIT_LOG(ERR,
> +                           "Ena PMD does not support secondary
> processes\n");
> +               return -ENOTSUP;
> +       }
> +
>         return rte_eth_dev_pci_generic_probe(pci_dev,
>                 sizeof(struct ena_adapter), eth_ena_dev_init);
>  }
>
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