From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AA83B5372C9; Thu, 17 Sep 2026 17:02:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789664538; cv=none; b=nR/Yqi80IOllhjIXb6DspBGj1qU+1uFaQJUxbZy1zqp+qmGerzTjojr69nPOR9w71u4aJa/LOb1O0uUGe/fLuxSv/Tsu4C1iI46EMxOLnpi2+ajBLuAvzL5XiIAN4TtwMjkAz9gMPkztSLluyxko7iYViAozaUjeCnaceARrG4Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789664538; c=relaxed/simple; bh=X0HXR3k8pgXn8Xa7RBlHYwueAJxjiX1qUrEg7whcf8M=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ajDHZLcTu13mQjpZFyI6RtIBci3+norSYdXWzjnl5wsObScjsr/fc2Vjq6f+P4katwwH9LnD2IdXBwqCv6Cc2t4i9pKreKP2sBimVnWF6DYp/hUmkKFyZPNN9vDbCTfXoFcI3BgYLNwlOOEgv5xA3/iyC6nWaE2UFXlZdyJ+PzM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=bGTBMHym; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="bGTBMHym" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 01AF11F000FF; Thu, 17 Sep 2026 17:02:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789664537; bh=UWWmRcj0T6RFq2oM96uTPsVzc6aQ4z6tFHURu/NREw8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=bGTBMHymiDwW3R6xoSMoRbJu2BjxjJXVYfBwMYd1y6txo5Iz1Bg98p13EE7w0bn5r 1zFwIqpk5sgyqADHVlXSJnmY9Kauo0NpcCZJJd04iuiFIzeinD4IXCEm7zXImL5/T4 ixRBP9bOcbuodn4pMq5kuARdz72r0xxtYwZca5bw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Maxime Chevallier , Nazim Amirul , Simon Horman , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.18 0406/1250] net: stmmac: xgmac2: disable RBUE in default RX interrupt mask Date: Thu, 17 Sep 2026 16:03:21 +0100 Message-ID: <20260917151603.032380037@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260917151551.901433442@linuxfoundation.org> References: <20260917151551.901433442@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ 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 --- 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