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 3F9A5C4332F for ; Thu, 17 Nov 2022 16:58:07 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1oviBW-0005rH-Ho; Thu, 17 Nov 2022 11:56:18 -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 1oviBU-0005qp-0o for qemu-devel@nongnu.org; Thu, 17 Nov 2022 11:56:16 -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 1oviBS-0007nT-CV for qemu-devel@nongnu.org; Thu, 17 Nov 2022 11:56:15 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1668704173; 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: in-reply-to:in-reply-to:references:references; bh=5yYVLofEmu2NspRaxaIPhn3aTno+moMYuabjvgVu3SU=; b=RHbXiz4nH29VZws3dc0E/0cY5mgw0FpaeWenk6nM9rZEjrLtdJ0XtFYmfxEb5mb00Dc0IX BKISzv+EJgGJASQfPJ++yD3Nthshzia4hQNk8fsI+zhXEloO1Fuvg6LHOS1etygXreQqrt BfZ1cN5183h8sj8RBdz1leuUCStrL/U= 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-49-xadYxSxSM3y5CCy_fE3O8g-1; Thu, 17 Nov 2022 11:56:12 -0500 X-MC-Unique: xadYxSxSM3y5CCy_fE3O8g-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 C6B09882820; Thu, 17 Nov 2022 16:56:11 +0000 (UTC) Received: from localhost (unknown [10.39.193.61]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2B70040C83AA; Thu, 17 Nov 2022 16:56:10 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Cc: Tobias Fiebig , Jason Wang , qemu-stable@nongnu.org, Stefan Hajnoczi , Russell King - ARM Linux Subject: [PATCH for-7.2 v3 3/3] rtl8139: honor large send MSS value Date: Thu, 17 Nov 2022 11:55:54 -0500 Message-Id: <20221117165554.1773409-4-stefanha@redhat.com> In-Reply-To: <20221117165554.1773409-1-stefanha@redhat.com> References: <20221117165554.1773409-1-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: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 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_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham 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. Jason Wang noticed that the Large-Send MSS value mask was incorrect so it is adjusted to match the datasheet and Linux 8139cp driver. 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 | 26 ++++++++++++-------------- 1 file changed, 12 insertions(+), 14 deletions(-) diff --git a/hw/net/rtl8139.c b/hw/net/rtl8139.c index 6dd7a8e6e0..700b1b66b6 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) @@ -1934,8 +1933,9 @@ static int rtl8139_cplus_transmit_one(RTL8139State *s) #define CP_TX_LS (1<<28) /* large send packet flag */ #define CP_TX_LGSEN (1<<27) -/* large send MSS mask, bits 16...25 */ -#define CP_TC_LGSEN_MSS_MASK ((1 << 12) - 1) +/* large send MSS mask, bits 16...26 */ +#define CP_TC_LGSEN_MSS_SHIFT 16 +#define CP_TC_LGSEN_MSS_MASK ((1 << 11) - 1) /* IP checksum offload flag */ #define CP_TX_IPCS (1<<18) @@ -2152,10 +2152,11 @@ static int rtl8139_cplus_transmit_one(RTL8139State *s) goto skip_offload; } - int large_send_mss = (txdw0 >> 16) & CP_TC_LGSEN_MSS_MASK; + int large_send_mss = (txdw0 >> CP_TC_LGSEN_MSS_SHIFT) & + 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; @@ -2180,25 +2181,22 @@ static int rtl8139_cplus_transmit_one(RTL8139State *s) goto skip_offload; } - /* ETH_MTU = ip header len + tcp header len + payload */ int tcp_data_len = ip_data_len - tcp_hlen; - int tcp_chunk_size = ETH_MTU - 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, - tcp_hlen, tcp_data_len, tcp_chunk_size); + "data len %d\n", ip_data_len, tcp_hlen, tcp_data_len); /* note the cycle below overwrites IP header data, but restores it from saved_ip_header before sending packet */ int is_last_frame = 0; - for (tcp_send_offset = 0; tcp_send_offset < tcp_data_len; tcp_send_offset += tcp_chunk_size) + for (tcp_send_offset = 0; tcp_send_offset < tcp_data_len; tcp_send_offset += large_send_mss) { - uint16_t chunk_size = tcp_chunk_size; + uint16_t chunk_size = large_send_mss; /* check if this is the last frame */ - if (tcp_send_offset + tcp_chunk_size >= tcp_data_len) + if (tcp_send_offset + large_send_mss >= tcp_data_len) { is_last_frame = 1; chunk_size = tcp_data_len - tcp_send_offset; @@ -2247,7 +2245,7 @@ static int rtl8139_cplus_transmit_one(RTL8139State *s) ip->ip_len = cpu_to_be16(hlen + tcp_hlen + chunk_size); /* increment IP id for subsequent frames */ - ip->ip_id = cpu_to_be16(tcp_send_offset/tcp_chunk_size + be16_to_cpu(ip->ip_id)); + ip->ip_id = cpu_to_be16(tcp_send_offset/large_send_mss + be16_to_cpu(ip->ip_id)); ip->ip_sum = 0; ip->ip_sum = ip_checksum(eth_payload_data, hlen); -- 2.38.1