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Wed, 04 Nov 2026 12:10:04 -0800 (PST) Received: from center.jhjvjihww5qejoy14qwv1cc4td.frax.internal.cloudapp.net ([131.189.143.225]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4b56eb4da1esm15954045e9.6.2026.11.04.12.10.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Nov 2026 12:10:03 -0800 (PST) From: Orgad Shaneh To: Maciej Fijalkowski Cc: Haiyang Zhang , Wei Liu , Dexuan Cui , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , netdev@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-rdma@vger.kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, Wei Hu , Konstantin Taranov , Simon Horman , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , Stanislav Fomichev , Dipayaan Roy , Hamza Mahfooz , Aditya Garg , Erni Sri Satya Vennela , Muhammad Falak R Wani , Jesse Brandeburg Subject: Re: [PATCH net] net: mana: fix XDP_REDIRECT of pre-allocated RX buffers Date: Wed, 4 Nov 2026 20:10:02 +0000 Message-ID: <20261104201002.2215474-1-orgads@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: <20261102064324.806414-1-orgads@gmail.com> X-Mailing-List: bpf@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Wed, Nov 04, 2026 at 05:22:24PM +0100, Maciej Fijalkowski wrote: > On Mon, Nov 02, 2026 at 06:43:24AM +0000, Orgad Shaneh wrote: [...] > > - act = mana_run_xdp(ndev, rxq, &xdp, buf_va, pkt_len); > > + act = mana_run_xdp(ndev, rxq, &xdp, buf_va, from_pool, pkt_len); > > I wonder if it wouldn't be better to work with rxoob objects which seem to > carry the from_pool setting? Thanks for the review. The rxoob no longer describes this buffer when XDP runs. mana_process_one_rx_pkt() calls mana_refill_rx_oob() before mana_rx_skb(), and the refill puts the new buffer into the same rxoob: *old_buf = rxoob->buf_va; *old_fp = rxoob->from_pool; rxoob->buf_va = va; ... rxoob->from_pool = from_pool; So by the time mana_run_xdp() runs, rxoob->from_pool is the flag of the replacement buffer. The flag of the received buffer survives only as old_fp, which is what mana_rx_skb() already gets as its from_pool argument and uses to free the buffer on PASS/TX/DROP. The patch passes that same value one call further down, to mana_run_xdp(). The two can differ. Refills come from the page pool (or from xdp_save_va, which only holds non-pool buffers), so on the first pass over a ring of pre-allocated buffers XDP gets a buffer with from_pool == false while its rxoob already says true. That first pass is exactly where the bug shows. Using the rxoob would mean moving the refill after XDP, which changes what happens when a refill fails: today the packet is dropped and its buffer stays in the ring. I preferred not to touch that in a fix. If you would rather mana_run_xdp() take something other than a bool, I can pass the xdp_rxq_info to use instead, chosen in mana_rx_skb(). Orgad