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([2a01:4b00:bd21:4f00:7cc6:d3ca:494:116c]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49fef60da94sm160803085e9.4.2026.09.27.11.21.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 27 Sep 2026 11:21:05 -0700 (PDT) Message-ID: <4bd67243-eccc-4c4d-896e-e88770b1967f@gmail.com> Date: Sun, 27 Sep 2026 19:21:02 +0100 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next 3/3] net: devmem: decode DMA addresses for TX To: Stanislav Fomichev , netdev@vger.kernel.org Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, hawk@kernel.org, ilias.apalodimas@linaro.org, axboe@kernel.dk, sdf@fomichev.me, bobbyeshleman@meta.com, almasrymina@google.com, kaiyuanz@google.com, linux-kernel@vger.kernel.org, io-uring@vger.kernel.org References: <20260922204348.717198-1-sdf@fomichev.me> <20260922204348.717198-4-sdf@fomichev.me> Content-Language: en-US From: Pavel Begunkov In-Reply-To: <20260922204348.717198-4-sdf@fomichev.me> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 9/22/26 21:43, Stanislav Fomichev wrote: > On 32-bit architectures where dma_addr_t is wider than unsigned long, > page_pool_set_dma_addr_netmem() stores page-aligned DMA addresses shifted > by PAGE_SHIFT. The net_iov branch of __skb_frag_dma_map() adds byte offsets > to the encoded value, so the NIC is programmed with an invalid DMA address. > This can trigger an IOMMU fault or DMA from unintended memory. > > Consolidate DMA address encoding, decoding, and representability checks in > netmem helpers. Use the common decoder from the page pool and net_iov TX > paths so both interpret stored addresses consistently. > > Fixes: bd61848900bf ("net: devmem: Implement TX path") > Signed-off-by: Stanislav Fomichev > --- > include/linux/skbuff.h | 7 +++++-- > include/net/netmem.h | 27 +++++++++++++++++++++++++++ > include/net/page_pool/helpers.h | 10 +--------- > net/core/page_pool_priv.h | 14 ++------------ > 4 files changed, 35 insertions(+), 23 deletions(-) > > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h > index 421f6fc45451..3740d4b15b70 100644 > --- a/include/linux/skbuff.h > +++ b/include/linux/skbuff.h > @@ -3833,9 +3833,12 @@ static inline dma_addr_t __skb_frag_dma_map(struct device *dev, > size_t offset, size_t size, > enum dma_data_direction dir) > { > + dma_addr_t addr; > + > if (skb_frag_is_net_iov(frag)) { > - return netmem_to_net_iov(frag->netmem)->desc.dma_addr + > - offset + frag->offset; > + addr = netmem_dma_addr_decode( > + netmem_get_dma_addr(frag->netmem)); > + return addr + offset + frag->offset; Looks like just page_pool_get_dma_addr_netmem(). Just a note, but it'd be nice to rename netmem_get_dma_addr() into something less confusing as well. -- Pavel Begunkov