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 64DFA51CF6E; Wed, 30 Sep 2026 16:08:53 +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=1790784539; cv=none; b=qpyXjxDbUJ2Y2I5IvFsWmYufAnnHzSA16r6FjWdXjFFTFBv1eXhvF2ObaiT7FOIYsHT7p0bT/Q5ac4MGbO4iQ2vh6lB0OijXwF77Cgsm6eMVKHOkzqjk3JTnrxt1QKsbuWu3ECus3ZBxwa3y3D/vtePCWfPrq+/l0Dt5ZkL8EJA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790784539; c=relaxed/simple; bh=F6giKY6sqNXd9qiIPZUrwAjXuO/aZGOciv8/vSliXaE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=S67C+jhve69n5ao+2L8HDqmQq6OgeqnSdoGp7x+NYWuw6V1lWi4TGPfp2K5hoNnuuknMkQPaEt2ZgIjlaH4e+ge9rJfbViBSz+ilI0cP4DEhXcOrDXYiNW1xq49jJYDWHoriDDmfGkWvke3sgOmwO1CHnBbNM/aOZhVso5Ic3bU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=HZxeUWKH; 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="HZxeUWKH" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8DE961F000FF; Wed, 30 Sep 2026 16:08:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790784533; bh=9C7QxQYCRWHs6pNXvTTcSewpP25W76ZcYsI85zKDd+Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=HZxeUWKHPj0+Aoxb/5gFZtpjuEbWllaanjIIWW6Ro0mfStj6EU2vO5q5GFBGDqMn7 aIJ+Qn6pl0QtOwKoxo7ZSEFiNfkzX/8v/V8gBRCwqlQWI5Dc3ay/U+4ZKrejHynvWL aTnS60J47ThqpjdZg2x/4cXDAqfeV7CrJGUzKUyU= 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 6.1 189/982] net: stmmac: xgmac2: disable RBUE in default RX interrupt mask Date: Wed, 30 Sep 2026 17:15:25 +0200 Message-ID: <20260930152420.876817513@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152416.775402466@linuxfoundation.org> References: <20260930152416.775402466@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 6.1-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 8748c37e9dac9..f9110e6164843 100644 --- a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h +++ b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h @@ -398,9 +398,9 @@ #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