From patchwork Fri Jan 3 16:44:59 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Liran Alon X-Patchwork-Id: 1217377 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming-netdev@ozlabs.org Delivered-To: patchwork-incoming-netdev@ozlabs.org Authentication-Results: ozlabs.org; spf=none (no SPF record) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=none dis=none) header.from=oracle.com Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=oracle.com header.i=@oracle.com header.b="nUloNc5r"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 47q9kP4CPTz9sP6 for ; Sat, 4 Jan 2020 03:45:17 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728014AbgACQpQ (ORCPT ); Fri, 3 Jan 2020 11:45:16 -0500 Received: from aserp2120.oracle.com ([141.146.126.78]:51460 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727966AbgACQpP (ORCPT ); Fri, 3 Jan 2020 11:45:15 -0500 Received: from pps.filterd (aserp2120.oracle.com [127.0.0.1]) by aserp2120.oracle.com (8.16.0.27/8.16.0.27) with SMTP id 003GiX7p085534; Fri, 3 Jan 2020 16:45:10 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=from : to : cc : subject : date : message-id : mime-version : content-transfer-encoding; s=corp-2019-08-05; bh=Atq7TR4pl1vuP1qeKg0Jq5pJkC/dq8w+QnAJK3ggn+M=; b=nUloNc5rHN1wzcGrVz0Zju1qBl1lV5KINVfx1r3rBHtjk48A2bsbEyz+CCtTnJUB/mIS XGvcesAlHfBpCU+kl4r6qE1DGIXWiyZGAencqyMiJuD6EiaXuiIWksTFpSPFd1cGR+Gw Eahqpx210PmYqTRzOit17wAz6R7qUlFTwQvbAq/7DkURwHVPbuNdEpXLKFXspOjtL31q u9gtOQhZHlPgecuvYXCrHZKX9hZpfYQPbFRa3aMewmVdbpcp1HE51PlWYwFZ10DmV1BM fQYoLb3Tluvc/6WJPGbUYf/i4q7A3EKYr0mMwkfoTqneXFXf/LleMp38MUfHyPkudUCi 0Q== Received: from aserp3020.oracle.com (aserp3020.oracle.com [141.146.126.70]) by aserp2120.oracle.com with ESMTP id 2x5y0pw5hy-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 03 Jan 2020 16:45:10 +0000 Received: from pps.filterd (aserp3020.oracle.com [127.0.0.1]) by aserp3020.oracle.com (8.16.0.27/8.16.0.27) with SMTP id 003Gd9db073658; Fri, 3 Jan 2020 16:45:09 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by aserp3020.oracle.com with ESMTP id 2xa7ty856v-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 03 Jan 2020 16:45:09 +0000 Received: from abhmp0013.oracle.com (abhmp0013.oracle.com [141.146.116.19]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 003Gj8aC019501; Fri, 3 Jan 2020 16:45:08 GMT Received: from Lirans-MBP.Home (/79.178.220.19) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Fri, 03 Jan 2020 08:45:07 -0800 From: Liran Alon To: csully@google.com, davem@davemloft.net, netdev@vger.kernel.org Cc: sagis@google.com, jonolson@google.com, yangchun@google.com, lrizzo@google.com, adisuresh@google.com, eric.dumazet@gmail.com, Liran Alon , Si-Wei Liu Subject: [PATCH v2] net: Google gve: Remove dma_wmb() before ringing doorbell Date: Fri, 3 Jan 2020 18:44:59 +0200 Message-Id: <20200103164459.71954-1-liran.alon@oracle.com> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9489 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1911140001 definitions=main-2001030153 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9489 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1911140001 definitions=main-2001030154 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Current code use dma_wmb() to ensure Rx/Tx descriptors are visible to device before writing to doorbell. However, these dma_wmb() are wrong and unnecessary. Therefore, they should be removed. iowrite32be() called from gve_rx_write_doorbell()/gve_tx_put_doorbell() should guaratee that all previous writes to WB/UC memory is visible to device before the write done by iowrite32be(). E.g. On ARM64, iowrite32be() calls __iowmb() which expands to dma_wmb() and only then calls __raw_writel(). Reviewed-by: Si-Wei Liu Signed-off-by: Liran Alon --- drivers/net/ethernet/google/gve/gve_rx.c | 2 -- drivers/net/ethernet/google/gve/gve_tx.c | 6 ------ 2 files changed, 8 deletions(-) diff --git a/drivers/net/ethernet/google/gve/gve_rx.c b/drivers/net/ethernet/google/gve/gve_rx.c index edec61dfc868..9f52e72ff641 100644 --- a/drivers/net/ethernet/google/gve/gve_rx.c +++ b/drivers/net/ethernet/google/gve/gve_rx.c @@ -418,8 +418,6 @@ bool gve_clean_rx_done(struct gve_rx_ring *rx, int budget, rx->cnt = cnt; rx->fill_cnt += work_done; - /* restock desc ring slots */ - dma_wmb(); /* Ensure descs are visible before ringing doorbell */ gve_rx_write_doorbell(priv, rx); return gve_rx_work_pending(rx); } diff --git a/drivers/net/ethernet/google/gve/gve_tx.c b/drivers/net/ethernet/google/gve/gve_tx.c index f4889431f9b7..d0244feb0301 100644 --- a/drivers/net/ethernet/google/gve/gve_tx.c +++ b/drivers/net/ethernet/google/gve/gve_tx.c @@ -487,10 +487,6 @@ netdev_tx_t gve_tx(struct sk_buff *skb, struct net_device *dev) * may have added descriptors without ringing the doorbell. */ - /* Ensure tx descs from a prior gve_tx are visible before - * ringing doorbell. - */ - dma_wmb(); gve_tx_put_doorbell(priv, tx->q_resources, tx->req); return NETDEV_TX_BUSY; } @@ -505,8 +501,6 @@ netdev_tx_t gve_tx(struct sk_buff *skb, struct net_device *dev) if (!netif_xmit_stopped(tx->netdev_txq) && netdev_xmit_more()) return NETDEV_TX_OK; - /* Ensure tx descs are visible before ringing doorbell */ - dma_wmb(); gve_tx_put_doorbell(priv, tx->q_resources, tx->req); return NETDEV_TX_OK; }