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 14:47:10 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Cc:     davem@...emloft.net, Tony Nguyen <anthony.l.nguyen@...el.com>,
        netdev@...r.kernel.org, nhorman@...hat.com, sassmann@...hat.com,
        jogreene@...hat.com
Subject: Re: [net-next 1/6] ixgbe: Do not allow LRO or MTU change with XDP

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?