From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 3E8AA34107C; Wed, 3 Dec 2025 15:57:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764777432; cv=none; b=crNDq+PSFYasvkVcGNk0+2OgbeSdN5NXrMbP+FxaYIHqfvJLF/st+uiEnK5f06jtTA+yHsk5uFEH/ZezjW0IEEEbk8Ny9ZMIlNMgtF9lPsZrH1VVsfpDVz5I5K+Y8s0mI2rw057x40X5O3Z9e1/i19WKNqjTnWO/1+GzP963h6o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764777432; c=relaxed/simple; bh=yWshMHqNyzEelKBM8db/v1uyMFCDs6XrFOzVV9ehBoM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=rIdUCpWQRpP0n+F720AGpACrihiOAFSKU24cMZfNeTgA0T5/Xu0X6duErAZvipcag0B+66BJCs0u2QUypxe9z+LQtkqC8bivlI93W4Ee26B+UJQicr90cXETVUfQr4zNYMXES0OA3f837FvLjXyPoEhlu8jW/zV4u4Zy3jF0w8g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=J6PCuXMd; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="J6PCuXMd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B6743C4CEF5; Wed, 3 Dec 2025 15:57:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1764777432; bh=yWshMHqNyzEelKBM8db/v1uyMFCDs6XrFOzVV9ehBoM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=J6PCuXMd9Piz4IfFD8d75DZzYMwPwUCNjyDSvfmRYw1K17OgKJBwz5VD0+fLLhun6 KwVw0qG6T0ohzIbMxqkyrkH5sP4m22UKw34uadl8w1uhAqscLnzcOUkhEPJVqCNQoQ Q+aH5NgyVkLvE8Cbht1WLM3qq27QX/e2xTVmwsS8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Fabrizio Castro , Lad Prabhakar , =?UTF-8?q?Niklas=20S=C3=B6derlund?= , Jakub Kicinski , Sasha Levin Subject: [PATCH 5.15 036/392] net: ravb: Enforce descriptor type ordering Date: Wed, 3 Dec 2025 16:23:06 +0100 Message-ID: <20251203152415.432089148@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20251203152414.082328008@linuxfoundation.org> References: <20251203152414.082328008@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-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Lad Prabhakar [ Upstream commit 5370c31e84b0e0999c7b5ff949f4e104def35584 ] Ensure the TX descriptor type fields are published in a safe order so the DMA engine never begins processing a descriptor chain before all descriptor fields are fully initialised. For multi-descriptor transmits the driver writes DT_FEND into the last descriptor and DT_FSTART into the first. The DMA engine begins processing when it observes DT_FSTART. Move the dma_wmb() barrier so it executes immediately after DT_FEND and immediately before writing DT_FSTART (and before DT_FSINGLE in the single-descriptor case). This guarantees that all prior CPU writes to the descriptor memory are visible to the device before DT_FSTART is seen. This avoids a situation where compiler/CPU reordering could publish DT_FSTART ahead of DT_FEND or other descriptor fields, allowing the DMA to start on a partially initialised chain and causing corrupted transmissions or TX timeouts. Such a failure was observed on RZ/G2L with an RT kernel as transmit queue timeouts and device resets. Fixes: 2f45d1902acf ("ravb: minimize TX data copying") Cc: stable@vger.kernel.org Co-developed-by: Fabrizio Castro Signed-off-by: Fabrizio Castro Signed-off-by: Lad Prabhakar Reviewed-by: Niklas Söderlund Link: https://patch.msgid.link/20251017151830.171062-4-prabhakar.mahadev-lad.rj@bp.renesas.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/net/ethernet/renesas/ravb_main.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) --- a/drivers/net/ethernet/renesas/ravb_main.c +++ b/drivers/net/ethernet/renesas/ravb_main.c @@ -1668,13 +1668,25 @@ static netdev_tx_t ravb_start_xmit(struc skb_tx_timestamp(skb); } - /* Descriptor type must be set after all the above writes */ - dma_wmb(); + if (num_tx_desc > 1) { desc->die_dt = DT_FEND; desc--; + /* When using multi-descriptors, DT_FEND needs to get written + * before DT_FSTART, but the compiler may reorder the memory + * writes in an attempt to optimize the code. + * Use a dma_wmb() barrier to make sure DT_FEND and DT_FSTART + * are written exactly in the order shown in the code. + * This is particularly important for cases where the DMA engine + * is already running when we are running this code. If the DMA + * sees DT_FSTART without the corresponding DT_FEND it will enter + * an error condition. + */ + dma_wmb(); desc->die_dt = DT_FSTART; } else { + /* Descriptor type must be set after all the above writes */ + dma_wmb(); desc->die_dt = DT_FSINGLE; }