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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (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 8EE94C433FE for ; Tue, 15 Nov 2022 16:38:23 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ouywC-0008NZ-VV; Tue, 15 Nov 2022 11:37:28 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ouywB-0008Kl-MB for qemu-devel@nongnu.org; Tue, 15 Nov 2022 11:37:27 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ouyw9-0002Ol-3S for qemu-devel@nongnu.org; Tue, 15 Nov 2022 11:37:27 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1668530244; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=0V9FW4XgRhJvhlV4mqFDlfCynvDX4A/FbUDSpDmXChc=; b=AFRyQA/QHxmkEADSpdbbzgMTLrcQlm7JSnoG7xOCP/GwGFtUBCr2C0xbPwLCFudivkNFU6 6jVTF4QM2sH3BeBmHApdtZzqu3ZkVBRGwgf7LWOLyLz4chS8ZOL2jvPZWWM6JnpxZD8ZAQ zrQVOXiksoNsD3+W4HgifzAx5FOa0ow= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-549-goINLCQPNi2SEylKk-NQRg-1; Tue, 15 Nov 2022 11:37:20 -0500 X-MC-Unique: goINLCQPNi2SEylKk-NQRg-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id D90CB101A528; Tue, 15 Nov 2022 16:37:19 +0000 (UTC) Received: from localhost (unknown [10.39.192.154]) by smtp.corp.redhat.com (Postfix) with ESMTP id 28D6E40C835A; Tue, 15 Nov 2022 16:37:18 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Cc: jasowang@redhat.com, qemu-stable@nongnu.org, Stefan Hajnoczi , Russell King - ARM Linux , Tobias Fiebig Subject: [PATCH for-7.2] rtl8139: honor large send MSS value Date: Tue, 15 Nov 2022 11:36:59 -0500 Message-Id: <20221115163659.1595865-1-stefanha@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.1 on 10.11.54.1 Received-SPF: pass client-ip=170.10.129.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org The Large-Send Task Offload Tx Descriptor (9.2.1 Transmit) has a Large-Send MSS value where the driver specifies the MSS. See the datasheet here: http://realtek.info/pdf/rtl8139cp.pdf The code ignores this value and uses a hardcoded MSS of 1500 bytes instead. When the MTU is less than 1500 bytes the hardcoded value results in IP fragmentation and poor performance. Use the Large-Send MSS value to correctly size Large-Send packets. This issue was discussed in the past here: https://lore.kernel.org/all/20161114162505.GD26664@stefanha-x1.localdomain/ Reported-by: Russell King - ARM Linux Reported-by: Tobias Fiebig Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1312 Signed-off-by: Stefan Hajnoczi --- hw/net/rtl8139.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) Tobias: Please test this fix. Thanks! diff --git a/hw/net/rtl8139.c b/hw/net/rtl8139.c index e6643e3c9d..ecc4dcb07f 100644 --- a/hw/net/rtl8139.c +++ b/hw/net/rtl8139.c @@ -77,7 +77,6 @@ ( ( input ) & ( size - 1 ) ) #define ETHER_TYPE_LEN 2 -#define ETH_MTU 1500 #define VLAN_TCI_LEN 2 #define VLAN_HLEN (ETHER_TYPE_LEN + VLAN_TCI_LEN) @@ -2151,8 +2150,8 @@ static int rtl8139_cplus_transmit_one(RTL8139State *s) int large_send_mss = (txdw0 >> 16) & CP_TC_LGSEN_MSS_MASK; - DPRINTF("+++ C+ mode offloaded task TSO MTU=%d IP data %d " - "frame data %d specified MSS=%d\n", ETH_MTU, + DPRINTF("+++ C+ mode offloaded task TSO IP data %d " + "frame data %d specified MSS=%d\n", ip_data_len, saved_size - ETH_HLEN, large_send_mss); int tcp_send_offset = 0; @@ -2177,9 +2176,13 @@ static int rtl8139_cplus_transmit_one(RTL8139State *s) goto skip_offload; } - /* ETH_MTU = ip header len + tcp header len + payload */ + /* MSS too small? */ + if (tcp_hlen + hlen >= large_send_mss) { + goto skip_offload; + } + int tcp_data_len = ip_data_len - tcp_hlen; - int tcp_chunk_size = ETH_MTU - hlen - tcp_hlen; + int tcp_chunk_size = large_send_mss - hlen - tcp_hlen; DPRINTF("+++ C+ mode TSO IP data len %d TCP hlen %d TCP " "data len %d TCP chunk size %d\n", ip_data_len, -- 2.38.1