netdev - Re: [PATCH bpf-next 03/10] ice: xsk: terminate NAPI when XSK Rx queue gets full

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Date:   Tue, 5 Apr 2022 14:02:39 +0200
From:   Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To:     Alexander Lobakin <alexandr.lobakin@...el.com>
Cc:     bpf@...r.kernel.org, ast@...nel.org, daniel@...earbox.net,
        magnus.karlsson@...el.com, bjorn@...nel.org,
        netdev@...r.kernel.org, brouer@...hat.com, maximmi@...dia.com
Subject: Re: [PATCH bpf-next 03/10] ice: xsk: terminate NAPI when XSK Rx
 queue gets full

On Tue, Apr 05, 2022 at 01:34:03PM +0200, Alexander Lobakin wrote:
> From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
> Date: Tue, 5 Apr 2022 13:06:24 +0200
> 
> > Correlate -ENOBUFS that was returned from xdp_do_redirect() with a XSK
> > Rx queue being full. In such case, terminate the softirq processing and
> > let the user space to consume descriptors from XSK Rx queue so that
> > there is room that driver can use later on.
> > 
> > Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
> > ---
> >  drivers/net/ethernet/intel/ice/ice_txrx.h |  1 +
> >  drivers/net/ethernet/intel/ice/ice_xsk.c  | 25 +++++++++++++++--------
> >  2 files changed, 17 insertions(+), 9 deletions(-)
> 
> --- 8< ---
> 
> > @@ -551,15 +552,15 @@ ice_run_xdp_zc(struct ice_rx_ring *rx_ring, struct xdp_buff *xdp,
> >  		if (result == ICE_XDP_CONSUMED)
> >  			goto out_failure;
> >  		break;
> > +	case XDP_DROP:
> > +		result = ICE_XDP_CONSUMED;
> > +		break;
> >  	default:
> >  		bpf_warn_invalid_xdp_action(rx_ring->netdev, xdp_prog, act);
> >  		fallthrough;
> >  	case XDP_ABORTED:
> >  out_failure:
> >  		trace_xdp_exception(rx_ring->netdev, xdp_prog, act);
> > -		fallthrough;
> > -	case XDP_DROP:
> > -		result = ICE_XDP_CONSUMED;
> >  		break;
> 
> So the result for %XDP_ABORTED will be %ICE_XDP_PASS now? Or I'm
> missing something :s

Yikes! I generally wanted to avoid the overwrite of result but still go
through the exception path.


Below should be fine if we add it to the current patch, but i'll double
check after the dinner.

Good catch as always, Alex :)

diff --git a/drivers/net/ethernet/intel/ice/ice_xsk.c b/drivers/net/ethernet/intel/ice/ice_xsk.c
index 143f6b6937bd..16c282b7050b 100644
--- a/drivers/net/ethernet/intel/ice/ice_xsk.c
+++ b/drivers/net/ethernet/intel/ice/ice_xsk.c
@@ -559,6 +559,7 @@ ice_run_xdp_zc(struct ice_rx_ring *rx_ring, struct xdp_buff *xdp,
 		bpf_warn_invalid_xdp_action(rx_ring->netdev, xdp_prog, act);
 		fallthrough;
 	case XDP_ABORTED:
+		result = ICE_XDP_CONSUMED;
 out_failure:
 		trace_xdp_exception(rx_ring->netdev, xdp_prog, act);
 		break;


> 
> >  	}
> >  
> > @@ -628,10 +629,16 @@ int ice_clean_rx_irq_zc(struct ice_rx_ring *rx_ring, int budget)
> 
> --- 8< ---
> 
> > -- 
> > 2.33.1
> 
> Thanks,
> Al