netdev - RE: [PATCH net-next v4 4/5] bnx2x: Use NETIF_F_GRO

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Date:   Thu, 14 Dec 2017 07:46:01 +0000
From:   "Chopra, Manish" <Manish.Chopra@...ium.com>
To:     Michael Chan <michael.chan@...adcom.com>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "andrew.gospodarek@...adcom.com" <andrew.gospodarek@...adcom.com>,
        "Elior, Ariel" <Ariel.Elior@...ium.com>,
        Dept-Eng Everest Linux L2 <Dept-EngEverestLinuxL2@...ium.com>
Subject: RE: [PATCH net-next v4 4/5] bnx2x: Use NETIF_F_GRO_HW.

> -----Original Message-----
> From: Michael Chan [mailto:michael.chan@...adcom.com]
> Sent: Thursday, December 14, 2017 2:16 AM
> To: Chopra, Manish <Manish.Chopra@...ium.com>
> Cc: davem@...emloft.net; netdev@...r.kernel.org;
> andrew.gospodarek@...adcom.com; Elior, Ariel <Ariel.Elior@...ium.com>;
> Dept-Eng Everest Linux L2 <Dept-EngEverestLinuxL2@...ium.com>
> Subject: Re: [PATCH net-next v4 4/5] bnx2x: Use NETIF_F_GRO_HW.
> 
> On Wed, Dec 13, 2017 at 1:08 AM, Chopra, Manish
> <Manish.Chopra@...ium.com> wrote:
> >
> > Hi Michael,  There seems a behavioral change here. This driver support
> > two HW aggregation modes [LRO and GRO] With the changes, Interfaces
> come with HW GRO enabled and LRO disabled by default as opposed to earlier
> where interfaces used to come with LRO enabled.
> 
> Right.  Before, you had both NETIF_F_GRO and NETIF_F_LRO set and the code
> looked at NETIF_F_LRO first and turned on LRO.
> 
> Now, we set NETIF_F_GRO and NETIF_F_GRO_HW by default.  NETIF_F_LRO is
> turned off since NETIF_F_GRO_HW is on.
> 
> If you want, I can change it back to the old default.

Yes please, I think we should not make any default behavior change.
Few more comments -

1). This driver uses module param "disable_tpa" also to completely disable TPA [whether it be LRO or HW GRO] along the initialization flow.

For ex. 

/*Set TPA flags*/
if (bp->disable_tpa) {
        bp->dev->hw_features &= ~NETIF_F_LRO;
        bp->dev->features &= ~NETIF_F_LRO;
}

I think we should also disable HW gro here as well, so that device will come up with no TPA at all.

2). In bnx2x_fix_features() we used to do before these changes -

        /* TPA requires Rx CSUM offloading */
        if (!(features & NETIF_F_RXCSUM)) {
                features &= ~NETIF_F_LRO;
                features &= ~NETIF_F_GRO;
        }

I think we should not turn off SW gro here, we should turn off HW gro here now ?
	
> 
> >
> > Also, there seems some problem when turning on LRO even after GRO disable.
> > When I tried to disable GRO and then tried to enable LRO it didn't go well. Not
> sure why ?
> 
> I just put an old BCM57810 card into my machine and it works for me.
> As long as I turn off GRO or GRO_HW, I can turn on LRO.
> 
> [root@...alhost bnx2x]# ethtool -K p1p1 lro on Cannot get device udp-
> fragmentation-offload settings: Operation not supported Cannot get device
> udp-fragmentation-offload settings: Operation not supported Could not change
> any device features [root@...alhost bnx2x]# ethtool -K p1p1 gro off Cannot get
> device udp-fragmentation-offload settings: Operation not supported Cannot get
> device udp-fragmentation-offload settings: Operation not supported Actual
> changes:
> generic-receive-offload: off
> large-receive-offload: on
> rx-gro-hw: off [requested on]
> [root@...alhost bnx2x]# ethtool -K p1p1 lro on Cannot get device udp-
> fragmentation-offload settings: Operation not supported Cannot get device
> udp-fragmentation-offload settings: Operation not supported

Doesn't sound like HW specific.
Probably, I was testing on your older series, I will check again on latest series.