Re: [PATCH v2 net] ixgbe: allow to increase MTU to some extent with XDP enabled

[Jason Xing <kerneljasonxing@gmail.com>]

On Fri, Jan 27, 2023 at 11:08 PM Jason Xing <kerneljasonxing@gmail.com> wrote:
>
> On Fri, Jan 27, 2023 at 10:54 PM Jason Xing <kerneljasonxing@gmail.com> wrote:
> >
> > My bad. It's not that right. Please ignore the v2 patch. I need some
> > time to do more studies and tests on this part.
> >
>
> In the meantime, any suggestions and help are appreciated :) I'm still
> working on it.
>

Dear maintainers,  after several tests I did during this time as much
as possible,  I couldn't find anything wrong though I am not that
familiar with the whole ixgbe code. I decided to 'reopen' this patch
v2. Please help me review the current patch.

Thanks,
Jason


>
> > Thanks,
> > Jason
> >
> > On Fri, Jan 27, 2023 at 8:20 PM Jason Xing <kerneljasonxing@gmail.com> wrote:
> > >
> > > From: Jason Xing <kernelxing@tencent.com>
> > >
> > > I encountered one case where I cannot increase the MTU size directly
> > > from 1500 to 2000 with XDP enabled if the server is equipped with
> > > IXGBE card, which happened on thousands of servers in production
> > > environment.
> > >
> > > This patch follows the behavior of changing MTU as i40e/ice does.
> > >
> > > Referrences:
> > > commit 23b44513c3e6f ("ice: allow 3k MTU for XDP")
> > > commit 0c8493d90b6bb ("i40e: add XDP support for pass and drop actions")
> > >
> > > Link: https://lore.kernel.org/lkml/20230121085521.9566-1-kerneljasonxing@gmail.com/
> > > Signed-off-by: Jason Xing <kernelxing@tencent.com>
> > > ---
> > > v2:
> > > 1) change the commit message.
> > > 2) modify the logic when changing MTU size suggested by Maciej and Alexander.
> > > ---
> > >  drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 25 ++++++++++++-------
> > >  1 file changed, 16 insertions(+), 9 deletions(-)
> > >
> > > diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> > > index ab8370c413f3..2c1b6eb60436 100644
> > > --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> > > +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> > > @@ -6777,6 +6777,18 @@ static void ixgbe_free_all_rx_resources(struct ixgbe_adapter *adapter)
> > >                         ixgbe_free_rx_resources(adapter->rx_ring[i]);
> > >  }
> > >
> > > +/**
> > > + * ixgbe_max_xdp_frame_size - returns the maximum allowed frame size for XDP
> > > + * @adapter - device handle, pointer to adapter
> > > + */
> > > +static int ixgbe_max_xdp_frame_size(struct ixgbe_adapter *adapter)
> > > +{
> > > +       if (PAGE_SIZE >= 8192 || adapter->flags2 & IXGBE_FLAG2_RX_LEGACY)
> > > +               return IXGBE_RXBUFFER_2K;
> > > +       else
> > > +               return IXGBE_RXBUFFER_3K;
> > > +}
> > > +
> > >  /**
> > >   * ixgbe_change_mtu - Change the Maximum Transfer Unit
> > >   * @netdev: network interface device structure
> > > @@ -6788,18 +6800,13 @@ static int ixgbe_change_mtu(struct net_device *netdev, int new_mtu)
> > >  {
> > >         struct ixgbe_adapter *adapter = netdev_priv(netdev);
> > >
> > > -       if (adapter->xdp_prog) {
> > > +       if (ixgbe_enabled_xdp_adapter(adapter)) {
> > >                 int new_frame_size = new_mtu + ETH_HLEN + ETH_FCS_LEN +
> > >                                      VLAN_HLEN;
> > > -               int i;
> > > -
> > > -               for (i = 0; i < adapter->num_rx_queues; i++) {
> > > -                       struct ixgbe_ring *ring = adapter->rx_ring[i];
> > >
> > > -                       if (new_frame_size > ixgbe_rx_bufsz(ring)) {
> > > -                               e_warn(probe, "Requested MTU size is not supported with XDP\n");
> > > -                               return -EINVAL;
> > > -                       }
> > > +               if (new_frame_size > ixgbe_max_xdp_frame_size(adapter)) {
> > > +                       e_warn(probe, "Requested MTU size is not supported with XDP\n");
> > > +                       return -EINVAL;
> > >                 }
> > >         }
> > >
> > > --
> > > 2.37.3
> > >