From: Maciej Fijalkowski <maciej.fijalkowski@xxxxxxxxx>
Date: Fri, 26 Nov 2021 15:38:48 +0100
> Fix a bug in which the receiving of packets can stop in the zero-copy
> driver. Ice HW ignores 3 lower bits from QRX_TAIL register, which means
> that tail is bumped only on intervals of 8. Currently with XSK RX
> batching in place, ice_alloc_rx_bufs_zc() clears the status_error0 only
> of the last descriptor that has been allocated/taken from the XSK buffer
> pool. status_error0 includes DD bit that is looked upon by the
> ice_clean_rx_irq_zc() to tell if a descriptor can be processed.
>
> The bug can be triggered when driver updates the ntu but not the
> QRX_TAIL, so HW wouldn't have a chance to write to the ready
> descriptors. Later on driver moves the ntc to the mentioned set of
> descriptors and interprets them as a ready to be processed, since
> corresponding DD bits were not cleared nor any writeback has happened
> that would clear it. This can then lead to ntc == ntu case which means
> that ring is empty and no further packet processing.
>
> Fix the XSK traffic hang that can be observed when l2fwd scenario from
> xdpsock is used by making sure that status_error0 is cleared for each
> descriptor that is fed to HW and therefore we are sure that driver will
> not processed non-valid DD bits. This will also prevent the driver from
> processing the descriptors that were allocated in favor of the
> previously processed ones, but writeback didn't happen yet.
>
> Fixes: db804cfc21e9 ("ice: Use the xsk batched rx allocation interface")
> Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@xxxxxxxxx>
Reviewed-by: Alexander Lobakin <alexandr.lobakin@xxxxxxxxx>
Thanks!
> ---
> drivers/net/ethernet/intel/ice/ice_xsk.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/net/ethernet/intel/ice/ice_xsk.c b/drivers/net/ethernet/intel/ice/ice_xsk.c
> index ff55cb415b11..bb9a80847298 100644
> --- a/drivers/net/ethernet/intel/ice/ice_xsk.c
> +++ b/drivers/net/ethernet/intel/ice/ice_xsk.c
> @@ -383,6 +383,7 @@ bool ice_alloc_rx_bufs_zc(struct ice_rx_ring *rx_ring, u16 count)
> while (i--) {
> dma = xsk_buff_xdp_get_dma(*xdp);
> rx_desc->read.pkt_addr = cpu_to_le64(dma);
> + rx_desc->wb.status_error0 = 0;
>
> rx_desc++;
> xdp++;
> --
> 2.31.1
Al
