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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 7FCD1C624C6 for ; Mon, 31 Aug 2026 13:40:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc: To:From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=iKsSeNKVyL3SwSg+t7MgLcjrlPQYJJOPY8s/xCjy++I=; b=wU/krMEeBohEbX4Kvud+XKIgYS V3x0CRlwrRODrBiv9ps0LH5un/4w8VmX/Kam/vqgHtat39h66xFcCL/sKACcQkt1rwoTy9XWrfxYa w7br/ZdACN3HiuQefJH4sNJU3498A/ivYJf9XdhC8kf4K9tuspCavI+GE+ooRGVVIFACEOSfje0rP 559G/UfpE+zfjj6szE6IQHqB853BnPqKUxQ7B8/5ag42fREV7azK/rTxM7DBnKi2QXqKryBKVKiOH 4Z8xQDrXMxNtxH7DWFX/yE95KDV9GFZcGNf0sDJpdSoDu5b4wNdAYa6N+3uzw4409BRgbhG0GTTT/ JfHGGerg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x12FZ-00000009T9J-2nlG; Mon, 31 Aug 2026 13:40:38 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1x12FV-00000009T58-1KoC for linux-arm-kernel@lists.infradead.org; Mon, 31 Aug 2026 13:40:33 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 15856409D4; Mon, 31 Aug 2026 13:40:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3E2FE1F00ACF; Mon, 31 Aug 2026 13:40:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788183633; bh=iKsSeNKVyL3SwSg+t7MgLcjrlPQYJJOPY8s/xCjy++I=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=XGgbL68kZFYDRCtjONjvVekYOhQ9WBsgRvPyfFcOpYLOD0oDLc99Z0QrAushL/gYp +omCJq5yDncYlrLjVB02hJNo0Ts5h//yApUcmmWNTpw/q+L/Z3+X9y2bfnyYKGVYAx UIPgy96NUCs42PY0ysFH9RqNqAXNIOLuuuanLs79xBAgqwppEjnlmVqb2o+FUqsTKQ RY3MVtTt6eWHfZv6r3qwB7aJ59bWDnLPWzSsgrJZMDNMmSfTIGInvIReBPcctO1PQG WwrPfi1TU4HNuzuGZ7i6M0xllyscgtFX0WzRN783J75phZaggW/Ei3CfKHGjGQmCNo 7AuHt4bm6qskA== From: Sasha Levin To: patches@lists.linux.dev, stable@vger.kernel.org Cc: Nazim Amirul , Maxime Chevallier , Simon Horman , Jakub Kicinski , Sasha Levin , andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, pabeni@redhat.com, mcoquelin.stm32@gmail.com, alexandre.torgue@foss.st.com, netdev@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH AUTOSEL 6.18-5.10] net: stmmac: xgmac2: disable RBUE in default RX interrupt mask Date: Mon, 31 Aug 2026 09:23:58 -0400 Message-ID: <20260831133314.4125787-210-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260831133314.4125787-1-sashal@kernel.org> References: <20260831133314.4125787-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.18.48 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Nazim Amirul [ Upstream commit d3265c19b35d036bba327b36b5366bee76b0157c ] Enabling the RX Buffer Unavailable (RBUE) interrupt is counterproductive and can trigger a MAC interrupt storm under heavy RX pressure. When the DMA runs out of RX descriptors it fires RBUE continuously until software refills the ring. However, RBUE is redundant: the normal RX completion interrupt (RIE) already triggers NAPI, which processes completed descriptors and refills the ring, causing the DMA to resume. The RBUE handler itself only sets handle_rx - the same outcome as RIE. On Agilex5 under heavy RX pressure, the MAC interrupt (which includes RBUE) was observed firing 1,821,811,555 times against only 2,618,627 actual RX completions - a ~695x ratio - confirming the severity of the storm. RBUE does not provide OOM recovery. If page_pool is exhausted, stmmac_rx_refill() cannot advance the DMA tail pointer, the DMA stays suspended, and RBUE fires again on the next NAPI completion - a storm with no forward progress. This patch trades that storm for a clean stall with the same RX outcome. Proper OOM recovery is a pre-existing gap outside the scope of this fix. Note: as a consequence of disabling RBUE, the rx_buf_unav_irq ethtool counter will always read 0 on XGMAC2 devices. This behaviour is already inconsistent across DWMAC core versions. Remove RBUE from XGMAC_DMA_INT_DEFAULT_EN and XGMAC_DMA_INT_DEFAULT_RX to prevent the interrupt storm while keeping normal RX handling intact. Reviewed-by: Maxime Chevallier Signed-off-by: Nazim Amirul Reviewed-by: Simon Horman Link: https://patch.msgid.link/20260609121703.9736-1-muhammad.nazim.amirul.nazle.asmade@altera.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- LLM Generated explanations, may be completely bogus: Both background git searches finished successfully, but returned no matches on the current `linux-6.18.y` checkout — expected, since the fix isn’t in stable yet. The commit was found on `master` as **`d3265c19b35d0`** (`net: stmmac: xgmac2: disable RBUE in default RX interrupt mask`). That confirmed the buggy RBUE masks are still present in 6.18.44 and the analysis conclusion stands: **YES** for stable backport. drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h index 67e2d539c3385..301e5e8993e37 100644 --- a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h +++ b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h @@ -385,9 +385,9 @@ #define XGMAC_RIE BIT(6) #define XGMAC_TBUE BIT(2) #define XGMAC_TIE BIT(0) -#define XGMAC_DMA_INT_DEFAULT_EN (XGMAC_NIE | XGMAC_AIE | XGMAC_RBUE | \ +#define XGMAC_DMA_INT_DEFAULT_EN (XGMAC_NIE | XGMAC_AIE | \ XGMAC_RIE | XGMAC_TIE) -#define XGMAC_DMA_INT_DEFAULT_RX (XGMAC_RBUE | XGMAC_RIE) +#define XGMAC_DMA_INT_DEFAULT_RX (XGMAC_RIE) #define XGMAC_DMA_INT_DEFAULT_TX (XGMAC_TIE) #define XGMAC_DMA_CH_Rx_WATCHDOG(x) (0x0000313c + (0x80 * (x))) #define XGMAC_RWT GENMASK(7, 0) -- 2.53.0