netdev - Re: [PATCH net 4/7] ice: use correct xdp_ring with XDP

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Date:   Tue, 26 Jan 2021 21:33:12 +0000
From:   "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>
To:     "kuba@...nel.org" <kuba@...nel.org>
CC:     "sassmann@...hat.com" <sassmann@...hat.com>,
        "Kuruvinakunnel, George" <george.kuruvinakunnel@...el.com>,
        "Fijalkowski, Maciej" <maciej.fijalkowski@...el.com>,
        "bjorn@...nel.org" <bjorn@...nel.org>,
        "Karlsson, Magnus" <magnus.karlsson@...el.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "Raczynski, Piotr" <piotr.raczynski@...el.com>
Subject: Re: [PATCH net 4/7] ice: use correct xdp_ring with XDP_TX action

On Sat, 2021-01-23 at 19:52 -0800, Jakub Kicinski wrote:
> On Fri, 22 Jan 2021 15:57:31 -0800 Tony Nguyen wrote:
> > From: Piotr Raczynski <piotr.raczynski@...el.com>
> > 
> > XDP queue number for XDP_TX action is used inconsistently
> > and may result with no packets transmitted. Fix queue number
> > used by the driver when doing XDP_TX, i.e. use receive queue
> > number as in ice_finalize_xdp_rx.
> > 
> > Also, using smp_processor_id() is wrong here and won't
> > work with less queues.
> > 
> > Fixes: efc2214b6047 ("ice: Add support for XDP")
> > Signed-off-by: Piotr Raczynski <piotr.raczynski@...el.com>
> > Tested-by: George Kuruvinakunnel <george.kuruvinakunnel@...el.com>
> > Signed-off-by: Tony Nguyen <anthony.l.nguyen@...el.com>
> > ---
> >  drivers/net/ethernet/intel/ice/ice_txrx.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.c
> > b/drivers/net/ethernet/intel/ice/ice_txrx.c
> > index b6fa83c619dd..7946a90b2da7 100644
> > --- a/drivers/net/ethernet/intel/ice/ice_txrx.c
> > +++ b/drivers/net/ethernet/intel/ice/ice_txrx.c
> > @@ -546,7 +546,7 @@ ice_run_xdp(struct ice_ring *rx_ring, struct
> > xdp_buff *xdp,
> >  	case XDP_PASS:
> >  		break;
> >  	case XDP_TX:
> > -		xdp_ring = rx_ring->vsi->xdp_rings[smp_processor_id()];
> > +		xdp_ring = rx_ring->vsi->xdp_rings[rx_ring->q_index];
> 
> But then what protects you from one CPU trying to use the tx ring
> from
> XDP_TX and another from ice_xdp_xmit() ?
> 
> Also why does this code not check queue_index < vsi->num_xdp_txq
> like ice_xdp_xmit() does?

Hi Jakub

I'm still waiting for information from the author. I'm going to drop
this patch from the series and resubmit.

> Let me CC your local XDP experts whose tags I'm surprised not to see
> on
> this patch.

I'll add them to the XDP patches in the future.


Thanks,
Tony