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Mon, 21 Jul 2025 01:34:02 -0700 (PDT) Received: from KERNELXING-MC1.tencent.com ([111.201.24.59]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-31cb7742596sm7082116a91.27.2025.07.21.01.33.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 21 Jul 2025 01:34:02 -0700 (PDT) From: Jason Xing To: anthony.l.nguyen@intel.com, przemyslaw.kitszel@intel.com, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, bjorn@kernel.org, magnus.karlsson@intel.com, maciej.fijalkowski@intel.com, jonathan.lemon@gmail.com, sdf@fomichev.me, ast@kernel.org, daniel@iogearbox.net, hawk@kernel.org, john.fastabend@gmail.com, mcoquelin.stm32@gmail.com, alexandre.torgue@foss.st.com Cc: linux-stm32@st-md-mailman.stormreply.com, bpf@vger.kernel.org, intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org, Jason Xing Subject: [PATCH net-next 2/2] igb: xsk: solve underflow of nb_pkts in zerocopy mode Date: Mon, 21 Jul 2025 16:33:43 +0800 Message-Id: <20250721083343.16482-3-kerneljasonxing@gmail.com> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20250721083343.16482-1-kerneljasonxing@gmail.com> References: <20250721083343.16482-1-kerneljasonxing@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Jason Xing There is no break time in the while() loop, so every time at the end of igb_xmit_zc(), underflow of nb_pkts will occur, which renders the return value always false. But theoretically, the result should be set after calling xsk_tx_peek_release_desc_batch(). We can take i40e_xmit_zc() as a good example. Returning false means we're not done with transmission and we need one more poll, which is exactly what igb_xmit_zc() always did before this patch. After this patch, the return value depends on the nb_pkts value. Two cases might happen then: 1. if (nb_pkts < budget), it means we process all the possible data, so return true and no more necessary poll will be triggered because of this. 2. if (nb_pkts == budget), it means we might have more data, so return false to let another poll run again. Fixes: f8e284a02afc ("igb: Add AF_XDP zero-copy Tx support") Signed-off-by: Jason Xing --- drivers/net/ethernet/intel/igb/igb_xsk.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/ethernet/intel/igb/igb_xsk.c b/drivers/net/ethernet/intel/igb/igb_xsk.c index 5cf67ba29269..243f4246fee8 100644 --- a/drivers/net/ethernet/intel/igb/igb_xsk.c +++ b/drivers/net/ethernet/intel/igb/igb_xsk.c @@ -482,7 +482,7 @@ bool igb_xmit_zc(struct igb_ring *tx_ring, struct xsk_buff_pool *xsk_pool) if (!nb_pkts) return true; - while (nb_pkts-- > 0) { + while (i < nb_pkts) { dma = xsk_buff_raw_get_dma(xsk_pool, descs[i].addr); xsk_buff_raw_dma_sync_for_device(xsk_pool, dma, descs[i].len); -- 2.41.3 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from smtp3.osuosl.org (smtp3.osuosl.org [140.211.166.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D6BBAC83F1A for ; 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Mon, 21 Jul 2025 01:34:02 -0700 (PDT) Received: from KERNELXING-MC1.tencent.com ([111.201.24.59]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-31cb7742596sm7082116a91.27.2025.07.21.01.33.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 21 Jul 2025 01:34:02 -0700 (PDT) From: Jason Xing To: anthony.l.nguyen@intel.com, przemyslaw.kitszel@intel.com, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, bjorn@kernel.org, magnus.karlsson@intel.com, maciej.fijalkowski@intel.com, jonathan.lemon@gmail.com, sdf@fomichev.me, ast@kernel.org, daniel@iogearbox.net, hawk@kernel.org, john.fastabend@gmail.com, mcoquelin.stm32@gmail.com, alexandre.torgue@foss.st.com Cc: linux-stm32@st-md-mailman.stormreply.com, bpf@vger.kernel.org, intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org, Jason Xing Date: Mon, 21 Jul 2025 16:33:43 +0800 Message-Id: <20250721083343.16482-3-kerneljasonxing@gmail.com> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20250721083343.16482-1-kerneljasonxing@gmail.com> References: <20250721083343.16482-1-kerneljasonxing@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Mailman-Original-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1753086843; x=1753691643; darn=lists.osuosl.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=lbtNVv68Al+8cVNVFbCAZPRp/ZwmAyAvC1F+49a5gy8=; b=M3ZI7xd/VyoVb4jeI6cU3+FgwGXw/iN2XI5cWq/z59doD+YBfDE1OTP0m77JrxF2J6 VY7eghfdifHRcErY5lYRpocilRRil7oucUhRC7lZns0WxkvVAGq6MwIxwkx4aembJ1vg Xlzy2SIexYnQHp/7u8o8e4eDyhliF0viPdESMEVCs2coqGk28XYFf1l5hhWg9n4AIsV8 mPsExmZnr6RteHXWdn42RPSgnVyLN+xxfyr/deQzffO3kBO/k8WKPCm1jVH1+1yMwrgO OCgh85U3SYLBhghhmeiuVW9bWGITD6UBNkjVixBXdudosx3JfKvA4SGEnBrF5/fD+vcS 0T6A== X-Mailman-Original-Authentication-Results: smtp4.osuosl.org; dmarc=pass (p=none dis=none) header.from=gmail.com X-Mailman-Original-Authentication-Results: smtp4.osuosl.org; dkim=pass (2048-bit key, unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20230601 header.b=M3ZI7xd/ Subject: [Intel-wired-lan] [PATCH net-next 2/2] igb: xsk: solve underflow of nb_pkts in zerocopy mode X-BeenThere: intel-wired-lan@osuosl.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Intel Wired Ethernet Linux Kernel Driver Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-wired-lan-bounces@osuosl.org Sender: "Intel-wired-lan" From: Jason Xing There is no break time in the while() loop, so every time at the end of igb_xmit_zc(), underflow of nb_pkts will occur, which renders the return value always false. But theoretically, the result should be set after calling xsk_tx_peek_release_desc_batch(). We can take i40e_xmit_zc() as a good example. Returning false means we're not done with transmission and we need one more poll, which is exactly what igb_xmit_zc() always did before this patch. After this patch, the return value depends on the nb_pkts value. Two cases might happen then: 1. if (nb_pkts < budget), it means we process all the possible data, so return true and no more necessary poll will be triggered because of this. 2. if (nb_pkts == budget), it means we might have more data, so return false to let another poll run again. Fixes: f8e284a02afc ("igb: Add AF_XDP zero-copy Tx support") Signed-off-by: Jason Xing --- drivers/net/ethernet/intel/igb/igb_xsk.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/ethernet/intel/igb/igb_xsk.c b/drivers/net/ethernet/intel/igb/igb_xsk.c index 5cf67ba29269..243f4246fee8 100644 --- a/drivers/net/ethernet/intel/igb/igb_xsk.c +++ b/drivers/net/ethernet/intel/igb/igb_xsk.c @@ -482,7 +482,7 @@ bool igb_xmit_zc(struct igb_ring *tx_ring, struct xsk_buff_pool *xsk_pool) if (!nb_pkts) return true; - while (nb_pkts-- > 0) { + while (i < nb_pkts) { dma = xsk_buff_raw_get_dma(xsk_pool, descs[i].addr); xsk_buff_raw_dma_sync_for_device(xsk_pool, dma, descs[i].len); -- 2.41.3