netdev - RE: [net-next 1/6] ixgbe: Do not allow LRO or MTU change with XDP

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Date:   Thu, 26 Jul 2018 21:51:57 +0000
From:   "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>,
        "Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "nhorman@...hat.com" <nhorman@...hat.com>,
        "sassmann@...hat.com" <sassmann@...hat.com>,
        "jogreene@...hat.com" <jogreene@...hat.com>
Subject: RE: [net-next 1/6] ixgbe: Do not allow LRO or MTU change with XDP

> From: Jakub Kicinski [mailto:jakub.kicinski@...ronome.com]
> Sent: Thursday, July 26, 2018 2:47 PM
> On Thu, 26 Jul 2018 14:21:08 -0700, Jakub Kicinski wrote:
> > On Thu, 26 Jul 2018 10:40:45 -0700, Jeff Kirsher wrote:
> > > From: Tony Nguyen <anthony.l.nguyen@...el.com>
> > >
> > > XDP does not support jumbo frames or LRO.  These checks are being
> > > made outside the driver when an XDP program is loaded, however,
> > > there is nothing preventing these from changing after an XDP program is
> loaded.
> > > Add the checks so that while an XDP program is loaded, do not allow
> > > MTU to be changed or LRO to be enabled.
> > >
> > > Signed-off-by: Tony Nguyen <anthony.l.nguyen@...el.com>
> > > Tested-by: Andrew Bowers <andrewx.bowers@...el.com>
> > > Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
> > > ---
> > >  drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 10 ++++++++++
> > >  1 file changed, 10 insertions(+)
> > >
> > > diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> > > b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> > > index 5a6600f7b382..c42256e91997 100644
> > > --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> > > +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> > > @@ -6469,6 +6469,11 @@ static int ixgbe_change_mtu(struct net_device
> > > *netdev, int new_mtu)  {
> > >  	struct ixgbe_adapter *adapter = netdev_priv(netdev);
> > >
> > > +	if (adapter->xdp_prog) {
> > > +		e_warn(probe, "MTU cannot be changed while XDP program is
> loaded\n");
> > > +		return -EPERM;
> >
> > EPERM looks wrong, EINVAL is common.  Also most drivers will just
> > check the bounds like you do in ixgbe_xdp_setup(), allowing the change
> > if new MTU still fits constraints.
> >
> > FWIW are the IXGBE_FLAG_SRIOV_ENABLED and IXGBE_FLAG_DCB_ENABLED
> flag
> > changes also covered while xdp is enabled?  Quick grep doesn't reveal
> > them being checked against xdp_prog other than in ixgbe_xdp_setup().
> 
> Ah, I didn't make the review in time :)  Could you follow up?

Yes, I'll make a follow-on patch to address your comments.