netdev - Re: [PATCH net] i40e: sync next_to_clean and next_to

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Date: Wed, 4 Oct 2023 15:16:20 +0200
From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To: Tirthendu Sarkar <tirthendu.sarkar@...el.com>
CC: <intel-wired-lan@...ts.osuosl.org>, <jesse.brandeburg@...el.com>,
	<anthony.l.nguyen@...el.com>, <netdev@...r.kernel.org>,
	<bpf@...r.kernel.org>, <magnus.karlsson@...el.com>
Subject: Re: [PATCH net] i40e: sync next_to_clean and next_to_process for
 programming status desc

On Wed, Oct 04, 2023 at 02:04:54PM +0530, Tirthendu Sarkar wrote:
> When a programming status desc is encountered on the rx_ring,
> next_to_process is bumped along with cleaned_count but next_to_clean is
> not. This causes I40E_DESC_UNUSED() macro to misbehave resulting in
> overwriting whole ring with new buffers.
> 
> Update next_to_clean to point to next_to_process on seeing a programming
> status desc if not in the middle of handling a multi-frag packet. Also,
> bump cleaned_count only for such case as otherwise next_to_clean buffer
> may be returned to hardware on reaching clean_threshold.
> 
> Fixes: e9031f2da1ae ("i40e: introduce next_to_process to i40e_ring")
> Suggested-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
> Reported-by: hq.dev+kernel@...fc.xyz
> Reported by: Solomon Peachy <pizza@...ftnet.org>
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217678
> Tested-by: hq.dev+kernel@...fc.xyz

Could you ask for a name of that someone?

> Tested by: Indrek Järve <incx@...tbite.net>
> Signed-off-by: Tirthendu Sarkar <tirthendu.sarkar@...el.com>

Acked-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>

> ---
>  drivers/net/ethernet/intel/i40e/i40e_txrx.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
> index 0b3a27f118fb..50c70a8e470a 100644
> --- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
> +++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
> @@ -2544,7 +2544,14 @@ static int i40e_clean_rx_irq(struct i40e_ring *rx_ring, int budget,
>  			rx_buffer = i40e_rx_bi(rx_ring, ntp);
>  			i40e_inc_ntp(rx_ring);
>  			i40e_reuse_rx_page(rx_ring, rx_buffer);
> -			cleaned_count++;
> +			/* Update ntc and bump cleaned count if not in the
> +			 * middle of mb packet.
> +			 */
> +			if (rx_ring->next_to_clean == ntp) {
> +				rx_ring->next_to_clean =
> +					rx_ring->next_to_process;
> +				cleaned_count++;
> +			}
>  			continue;
>  		}
>  
> -- 
> 2.34.1
>