linux-kernel - Re: [PATCH net] ethernet: ionic: Fix DMA mapping test in `ionic_xdp_post

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Message-ID: <aFF9S1BX8HgY+ihO@mev-dev.igk.intel.com>
Date: Tue, 17 Jun 2025 16:35:55 +0200
From: Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>
To: Thomas Fourier <fourier.thomas@...il.com>
Cc: Shannon Nelson <shannon.nelson@....com>,
	Brett Creeley <brett.creeley@....com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	Stanislav Fomichev <sdf@...ichev.me>,
	Vladimir Oltean <vladimir.oltean@....com>,
	Caleb Sander Mateos <csander@...estorage.com>,
	Taehee Yoo <ap420073@...il.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH net] ethernet: ionic: Fix DMA mapping test in
 `ionic_xdp_post_frame()`

On Tue, Jun 17, 2025 at 11:18:36AM +0200, Thomas Fourier wrote:
> The `ionic_tx_map_frag()` wrapper function is used which returns 0 or a
> valid DMA address.  Testing that pointer with `dma_mapping_error()`could
> be eroneous since the error value exptected by `dma_mapping_error()` is
> not 0 but `DMA_MAPPING_ERROR` which is often ~0.
> 
> Fixes: ac8813c0ab7d ("ionic: convert Rx queue buffers to use page_pool")
> Signed-off-by: Thomas Fourier <fourier.thomas@...il.com>
> ---
>  drivers/net/ethernet/pensando/ionic/ionic_txrx.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/pensando/ionic/ionic_txrx.c b/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
> index 2ac59564ded1..beefdc43013e 100644
> --- a/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
> +++ b/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
> @@ -357,7 +357,7 @@ static int ionic_xdp_post_frame(struct ionic_queue *q, struct xdp_frame *frame,
>  			} else {
>  				dma_addr = ionic_tx_map_frag(q, frag, 0,
>  							     skb_frag_size(frag));
> -				if (dma_mapping_error(q->dev, dma_addr)) {
> +				if (!dma_addr) {
>  					ionic_tx_desc_unmap_bufs(q, desc_info);
>  					return -EIO;

Right, in ionic_tx_map_skb() it is used correctly (like here now).
Thanks for fixing.

Reviewed-by: Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>

>  				}
> -- 
> 2.43.0