[ovs-dev] [PATCH v1] netdev-dpdk: Handle ENOTSUP for rte_eth_dev_set_mtu.

[Stokes, Ian]

> >
> > The function rte_eth_dev_set_mtu is not supported for all DPDK drivers.
> > Currently if it is not supported we return an error in
> > dpdk_eth_dev_queue_setup. There are two issues with this.
> >
> > (i) A device can still function even if rte_eth_dev_set_mtu is not
> > supported albeit with the default max rx packet length.
> >
> > (ii) When the ENOTSUP is returned it will not be caught in
> > port_reconfigure() at the dpif-netdev layer. Port_reconfigure() checks
> > if a netdev_reconfigure() function is supported for a given netdev and
> > ignores EOPNOTSUPP errors as it assumes errors of this value mean
> > there is no reconfiguration function. In this case the reconfiguration
> > function is supported for netdev dpdk but a function called as part of
> > the reconfigure (rte_eth_dev_set_mtu) may not be supported.
> >
> > As this is a corner case, this commit warns a user when
> > rte_eth_dev_set_mtu is not supported and informs them of the default
> > max rx packet length that will be used instead.
> >
> > Signed-off-by: Ian Stokes <ian.stokes at intel.com>
> > Co-author: Michal Weglicki <michalx.weglicki at intel.com>
> 
> Tested-by: Ciara Loftus <ciara.loftus at intel.com>
> 
> Hi Ian,
> 
> Thanks for the patch. It needs a rebase.
> 
> PCAP vdevs fall under the (i) category. Before this patch I always
> observed a SEGV on pcap rx. Queues were not setup for pcap devices due to
> the failed mtu_set function, and later polling on those non-existent
> queues caused the SEGV. This patch removes this case and reports the error
> as described instead.
> 
> Thanks,
> Ciara

Thanks for testing Ciara,

I've posted a v2 of the patch for the rebase and some minor changes to comments.

https://mail.openvswitch.org/pipermail/ovs-dev/2018-May/347399.html

Thanks
Ian
> 
> > ---
> >  lib/netdev-dpdk.c | 17 ++++++++++++++---
> >  1 file changed, 14 insertions(+), 3 deletions(-)
> >
> > diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c index
> > 50c7619..e6c483d 100644
> > --- a/lib/netdev-dpdk.c
> > +++ b/lib/netdev-dpdk.c
> > @@ -771,6 +771,7 @@ dpdk_eth_dev_queue_setup(struct netdev_dpdk *dev,
> > int n_rxq, int n_txq)
> >      int diag = 0;
> >      int i;
> >      struct rte_eth_conf conf = port_conf;
> > +    uint16_t conf_mtu;
> >
> >      /* For some NICs (e.g. Niantic), scatter_rx mode needs to be
> explicitly
> >       * enabled. */
> > @@ -804,9 +805,19 @@ dpdk_eth_dev_queue_setup(struct netdev_dpdk *dev,
> > int n_rxq, int n_txq)
> >
> >          diag = rte_eth_dev_set_mtu(dev->port_id, dev->mtu);
> >          if (diag) {
> > -            VLOG_ERR("Interface %s MTU (%d) setup error: %s",
> > -                    dev->up.name, dev->mtu, rte_strerror(-diag));
> > -            break;
> > +            /* A device may not support rte_eth_dev_set_mtu, in this
> case
> > +             * check flag a warning to the user and include the devices
> > +             * configured MTU value that will be used instead. */
> > +            if (-ENOTSUP == diag) {
> > +                rte_eth_dev_get_mtu(dev->port_id, &conf_mtu);
> > +                VLOG_WARN("Interface %s does not support MTU
> configuration, "
> > +                          "max packet size supported is %d.",
> > +                          dev->up.name, conf_mtu);
> > +            } else {
> > +                VLOG_ERR("Interface %s MTU (%d) setup error: %s",
> > +                         dev->up.name, dev->mtu, rte_strerror(-diag));
> > +                break;
> > +            }
> >          }
> >
> >          for (i = 0; i < n_txq; i++) {
> > --
> > 2.7.5
> >
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