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 X-Spam-Level: X-Spam-Status: No, score=-17.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 69726C433DB for ; Mon, 22 Feb 2021 04:16:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 29F8464EB4 for ; Mon, 22 Feb 2021 04:16:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230115AbhBVEP5 (ORCPT ); Sun, 21 Feb 2021 23:15:57 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:34082 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230083AbhBVEPy (ORCPT ); Sun, 21 Feb 2021 23:15:54 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1613967267; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=E+x2TUELl7mIVGk/ohyT3Fe+rS53LsnETTro7AaKiEY=; b=HHwaiOd87D7gzCq9keJmrraERvauRvKr9QgTSV20O9rmMV4rtRXvYPJy4n2lZlRvahy+29 peEAiywqXUCzne1Ax/TsNI5lEP/zqeKP7IIaVs8cLPEFjQnQnZQydszeflYxKluzCDcCg6 clrbtVbbEG6JvHOZ9AJdApAvBGgvhiE= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-182-kMsuTl1_NKemZuv_UIhDrw-1; Sun, 21 Feb 2021 23:14:25 -0500 X-MC-Unique: kMsuTl1_NKemZuv_UIhDrw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 702D18030BB; Mon, 22 Feb 2021 04:14:24 +0000 (UTC) Received: from wangxiaodeMacBook-Air.local (ovpn-13-112.pek2.redhat.com [10.72.13.112]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7D41660C5C; Mon, 22 Feb 2021 04:14:19 +0000 (UTC) Subject: Re: [PATCH] vdpa/mlx5: set_features should allow reset to zero To: Si-Wei Liu , mst@redhat.com, elic@nvidia.com Cc: linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org References: <1613735698-3328-1-git-send-email-si-wei.liu@oracle.com> From: Jason Wang Message-ID: <605e7d2d-4f27-9688-17a8-d57191752ee7@redhat.com> Date: Mon, 22 Feb 2021 12:14:17 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.16; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: <1613735698-3328-1-git-send-email-si-wei.liu@oracle.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-GB X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 2021/2/19 7:54 下午, Si-Wei Liu wrote: > Commit 452639a64ad8 ("vdpa: make sure set_features is invoked > for legacy") made an exception for legacy guests to reset > features to 0, when config space is accessed before features > are set. We should relieve the verify_min_features() check > and allow features reset to 0 for this case. > > It's worth noting that not just legacy guests could access > config space before features are set. For instance, when > feature VIRTIO_NET_F_MTU is advertised some modern driver > will try to access and validate the MTU present in the config > space before virtio features are set. This looks like a spec violation: " The following driver-read-only field, mtu only exists if VIRTIO_NET_F_MTU is set. This field specifies the maximum MTU for the driver to use. " Do we really want to workaround this? Thanks > Rejecting reset to 0 > prematurely causes correct MTU and link status unable to load > for the very first config space access, rendering issues like > guest showing inaccurate MTU value, or failure to reject > out-of-range MTU. > > Fixes: 1a86b377aa21 ("vdpa/mlx5: Add VDPA driver for supported mlx5 devices") > Signed-off-by: Si-Wei Liu > --- > drivers/vdpa/mlx5/net/mlx5_vnet.c | 15 +-------------- > 1 file changed, 1 insertion(+), 14 deletions(-) > > diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c > index 7c1f789..540dd67 100644 > --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c > +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c > @@ -1490,14 +1490,6 @@ static u64 mlx5_vdpa_get_features(struct vdpa_device *vdev) > return mvdev->mlx_features; > } > > -static int verify_min_features(struct mlx5_vdpa_dev *mvdev, u64 features) > -{ > - if (!(features & BIT_ULL(VIRTIO_F_ACCESS_PLATFORM))) > - return -EOPNOTSUPP; > - > - return 0; > -} > - > static int setup_virtqueues(struct mlx5_vdpa_net *ndev) > { > int err; > @@ -1558,18 +1550,13 @@ static int mlx5_vdpa_set_features(struct vdpa_device *vdev, u64 features) > { > struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev); > struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev); > - int err; > > print_features(mvdev, features, true); > > - err = verify_min_features(mvdev, features); > - if (err) > - return err; > - > ndev->mvdev.actual_features = features & ndev->mvdev.mlx_features; > ndev->config.mtu = cpu_to_mlx5vdpa16(mvdev, ndev->mtu); > ndev->config.status |= cpu_to_mlx5vdpa16(mvdev, VIRTIO_NET_S_LINK_UP); > - return err; > + return 0; > } > > static void mlx5_vdpa_set_config_cb(struct vdpa_device *vdev, struct vdpa_callback *cb)