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From: Alexander Lobakin <aleksander.lobakin@intel.com>
To: Thomas Fourier <fourier.thomas@gmail.com>
Cc: Shannon Nelson <shannon.nelson@amd.com>,
	Brett Creeley <brett.creeley@amd.com>,
	Andrew Lunn <andrew+netdev@lunn.ch>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	"Jakub Kicinski" <kuba@kernel.org>,
	Paolo Abeni <pabeni@redhat.com>,
	"Alexei Starovoitov" <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	"Jesper Dangaard Brouer" <hawk@kernel.org>,
	John Fastabend <john.fastabend@gmail.com>,
	Stanislav Fomichev <sdf@fomichev.me>,
	Vladimir Oltean <vladimir.oltean@nxp.com>,
	Caleb Sander Mateos <csander@purestorage.com>,
	Taehee Yoo <ap420073@gmail.com>, <netdev@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>, <bpf@vger.kernel.org>
Subject: Re: [PATCH net] ethernet: ionic: Fix DMA mapping test in `ionic_xdp_post_frame()`
Date: Tue, 17 Jun 2025 17:01:14 +0200	[thread overview]
Message-ID: <f977f68b-cec5-4ab7-b4bd-2cf6aca46267@intel.com> (raw)
In-Reply-To: <20250617091842.29732-2-fourier.thomas@gmail.com>

From: Thomas Fourier <fourier.thomas@gmail.com>
Date: Tue, 17 Jun 2025 11:18:36 +0200

> 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.

BTW I remember clearly that Chris wrote that dma_addr == 0 is a
perfectly valid DMA address, that's why ~0 was picked for error checking.
So maybe it's better to fix the driver. I realize that in the real
world, it's almost impossible to get dma_addr == 0 from dma_map_*(), but
still.

> 
> Fixes: ac8813c0ab7d ("ionic: convert Rx queue buffers to use page_pool")
> Signed-off-by: Thomas Fourier <fourier.thomas@gmail.com>

Thanks,
Olek

  parent reply	other threads:[~2025-06-17 15:01 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-06-17  9:18 Thomas Fourier
2025-06-17 14:35 ` Michal Swiatkowski
2025-06-17 15:01 ` Alexander Lobakin [this message]
2025-06-17 16:56 ` Brett Creeley
2025-06-17 18:57   ` [PATCH net,v2] ethernet: ionic: Fix DMA mapping tests Thomas Fourier
2025-06-18 23:15     ` Brett Creeley
2025-06-18 17:05   ` [PATCH net] ethernet: ionic: Fix DMA mapping test in `ionic_xdp_post_frame()` Alexander Lobakin

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