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=-17.3 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=ham 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 15366C433DB for ; Wed, 24 Feb 2021 06:57:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9655664EC3 for ; Wed, 24 Feb 2021 06:57:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234293AbhBXG5I (ORCPT ); Wed, 24 Feb 2021 01:57:08 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:57386 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230434AbhBXG4u (ORCPT ); Wed, 24 Feb 2021 01:56:50 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1614149723; 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=//VjBrrX+diVQv6GNcoSTqGXAnitFixElwDMOSM+paQ=; b=BX6JADwZsPAAcZWb8oQR16gnxPybgBHjv0eGWzhGFiGVNXrJpljpbKJFnSkKKWAuVtSdaP kVLVL90rlbuk4o0SQPGtGL0COtLayJpiONLdfZ67nIFRYSuOFrlDlDctslZnkZtvvWhiaW 8WDR6dy7f1kkCpHN2VLutDVnZmZ9gz0= 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-365-n7LCUzJENcSl-At0g7dlDQ-1; Wed, 24 Feb 2021 01:55:21 -0500 X-MC-Unique: n7LCUzJENcSl-At0g7dlDQ-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id D73C6801965; Wed, 24 Feb 2021 06:55:19 +0000 (UTC) Received: from wangxiaodeMacBook-Air.local (ovpn-13-96.pek2.redhat.com [10.72.13.96]) by smtp.corp.redhat.com (Postfix) with ESMTP id CB2DE72F84; Wed, 24 Feb 2021 06:55:14 +0000 (UTC) Subject: Re: [PATCH] vdpa/mlx5: set_features should allow reset to zero To: "Michael S. Tsirkin" , Eli Cohen Cc: Si-Wei Liu , 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> <605e7d2d-4f27-9688-17a8-d57191752ee7@redhat.com> <20210222023040-mutt-send-email-mst@kernel.org> <22fe5923-635b-59f0-7643-2fd5876937c2@oracle.com> <20210223082536-mutt-send-email-mst@kernel.org> <3ff5fd23-1db0-2f95-4cf9-711ef403fb62@oracle.com> <7e6291a4-30b1-6b59-a2bf-713e7b56826d@redhat.com> <20210224000528-mutt-send-email-mst@kernel.org> <20210224064520.GA204317@mtl-vdi-166.wap.labs.mlnx> <20210224014700-mutt-send-email-mst@kernel.org> From: Jason Wang Message-ID: Date: Wed, 24 Feb 2021 14:55:13 +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: <20210224014700-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-GB X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 2021/2/24 2:47 下午, Michael S. Tsirkin wrote: > On Wed, Feb 24, 2021 at 08:45:20AM +0200, Eli Cohen wrote: >> On Wed, Feb 24, 2021 at 12:17:58AM -0500, Michael S. Tsirkin wrote: >>> On Wed, Feb 24, 2021 at 11:20:01AM +0800, Jason Wang wrote: >>>> On 2021/2/24 3:35 上午, Si-Wei Liu wrote: >>>>> >>>>> On 2/23/2021 5:26 AM, Michael S. Tsirkin wrote: >>>>>> On Tue, Feb 23, 2021 at 10:03:57AM +0800, Jason Wang wrote: >>>>>>> On 2021/2/23 9:12 上午, Si-Wei Liu wrote: >>>>>>>> On 2/21/2021 11:34 PM, Michael S. Tsirkin wrote: >>>>>>>>> On Mon, Feb 22, 2021 at 12:14:17PM +0800, Jason Wang wrote: >>>>>>>>>> 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 >>>>>>>>> And also: >>>>>>>>> >>>>>>>>> The driver MUST follow this sequence to initialize a device: >>>>>>>>> 1. Reset the device. >>>>>>>>> 2. Set the ACKNOWLEDGE status bit: the guest OS has >>>>>>>>> noticed the device. >>>>>>>>> 3. Set the DRIVER status bit: the guest OS knows how to drive the >>>>>>>>> device. >>>>>>>>> 4. Read device feature bits, and write the subset of feature bits >>>>>>>>> understood by the OS and driver to the >>>>>>>>> device. During this step the driver MAY read (but MUST NOT write) >>>>>>>>> the device-specific configuration >>>>>>>>> fields to check that it can support the device before accepting it. >>>>>>>>> 5. Set the FEATURES_OK status bit. The driver MUST NOT accept new >>>>>>>>> feature bits after this step. >>>>>>>>> 6. Re-read device status to ensure the FEATURES_OK bit is still set: >>>>>>>>> otherwise, the device does not >>>>>>>>> support our subset of features and the device is unusable. >>>>>>>>> 7. Perform device-specific setup, including discovery of virtqueues >>>>>>>>> for the device, optional per-bus setup, >>>>>>>>> reading and possibly writing the device’s virtio configuration >>>>>>>>> space, and population of virtqueues. >>>>>>>>> 8. Set the DRIVER_OK status bit. At this point the device is “live”. >>>>>>>>> >>>>>>>>> >>>>>>>>> so accessing config space before FEATURES_OK is a spec >>>>>>>>> violation, right? >>>>>>>> It is, but it's not relevant to what this commit tries to address. I >>>>>>>> thought the legacy guest still needs to be supported. >>>>>>>> >>>>>>>> Having said, a separate patch has to be posted to fix the guest driver >>>>>>>> issue where this discrepancy is introduced to >>>>>>>> virtnet_validate() (since >>>>>>>> commit fe36cbe067). But it's not technically related to this patch. >>>>>>>> >>>>>>>> -Siwei >>>>>>> I think it's a bug to read config space in validate, we should >>>>>>> move it to >>>>>>> virtnet_probe(). >>>>>>> >>>>>>> Thanks >>>>>> I take it back, reading but not writing seems to be explicitly >>>>>> allowed by spec. >>>>>> So our way to detect a legacy guest is bogus, need to think what is >>>>>> the best way to handle this. >>>>> Then maybe revert commit fe36cbe067 and friends, and have QEMU detect >>>>> legacy guest? Supposedly only config space write access needs to be >>>>> guarded before setting FEATURES_OK. >>>> >>>> I agree. My understanding is that all vDPA must be modern device (since >>>> VIRITO_F_ACCESS_PLATFORM is mandated) instead of transitional device. >>>> >>>> Thanks >>> Well mlx5 has some code to handle legacy guests ... >>> Eli, could you comment? Is that support unused right now? >>> >> If you mean support for version 1.0, well the knob is there but it's not >> set in the firmware I use. Note sure if we will support this. > Hmm you mean it's legacy only right now? > Well at some point you will want advanced goodies like RSS > and all that is gated on 1.0 ;) So if my understanding is correct the device/firmware is legacy but require VIRTIO_F_ACCESS_PLATFORM semanic? Looks like a spec violation? Thanks > >>>>> -Siwie >>>>> >>>>>>>>>>> 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)