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=-3.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no 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 0C2B0C64E8A for ; Wed, 2 Dec 2020 03:30:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9C5BA20705 for ; Wed, 2 Dec 2020 03:30:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728221AbgLBDac (ORCPT ); Tue, 1 Dec 2020 22:30:32 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54018 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728162AbgLBDac (ORCPT ); Tue, 1 Dec 2020 22:30:32 -0500 Received: from mail-ej1-x644.google.com (mail-ej1-x644.google.com [IPv6:2a00:1450:4864:20::644]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2A512C0613CF for ; Tue, 1 Dec 2020 19:29:46 -0800 (PST) Received: by mail-ej1-x644.google.com with SMTP id 7so398764ejm.0 for ; Tue, 01 Dec 2020 19:29:46 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=mC7NATN5fdjUhjEcui+zCZKWukwACRp2Fb9GN0WZCDg=; b=me5p8I+uyXoIsbQ/KL71p7oysbM8P0Wqqg0/1JzIOGM/Nkiw3o3zWnB/hQtz/gDk/F YLvZ4Gn8mabeiXzsXXBFviafILt6sbalJ5TylI35x98jotBeu0G6BG/5lL/2eQZODZ3C HIUj00JYMJJE5NidSQvnaOneZ9tvRpvvxQbEaqKX8JVGlQjnEnZdZl3zlh8vb/yu95dF qLTk79vHtXPhZSwI9EseNb7GQjZHeJBAnmsyB9HnHh/Bh8awG6Q0H6CWZeJ36wVfRiLI K8EaY7FCtKNEOZOR7I80azPmGRj/IEtGjlpARFl05rQcsf5mt6dWsIEbCVW705WuBuYv NL7w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=mC7NATN5fdjUhjEcui+zCZKWukwACRp2Fb9GN0WZCDg=; b=fDjvqPyg8ZBQ83bkXardWx2Zj27QLne1VLLLCu35QkNsilO8YCEQYYFie4FdTK0jgX PYW8QIYdvD5eESzzHvTT4HEDsAGV40xzYaXmh2AQ9YqwYXWTNJG/8Aa0gE+YZ1eXQq/A U2MevhTfJo1B2mmD/a4HGj64dbUngqz8BIVMudQE1E65N5ZKt1+1lUwHyOwLayTIwI3H Ljgll3e4FyMCGkxGH/Y+zfcgbH5pIhGUSe2UfljDuO0/RmRqdcvYNkVtCAm1Olr5FJvH ZNlWBY2e7Rh7isTUsH6PJkCs6M174ADuciWk2dLigFvdSKBYro5ieptW580atgIyDSCA pdFQ== X-Gm-Message-State: AOAM531Oe/cN1EVm+ph7weeypBP9700gyA/2HizGef3bxeN1KFd4wWID TQZunhzQ8ysCMj5UisO7sAOa7hLoyKR/+uewVUfD X-Google-Smtp-Source: ABdhPJwPlpVRdNERy6bI0HedMqzM8eoaBzbgYZVjAe5T+QHfLIhsoPs3ig04m0syH3IwUOd2D5XMZiMrnc+PQ6AeROw= X-Received: by 2002:a17:906:591a:: with SMTP id h26mr458720ejq.174.1606879784766; Tue, 01 Dec 2020 19:29:44 -0800 (PST) MIME-Version: 1.0 References: <20201112064005.349268-1-parav@nvidia.com> <5b2235f6-513b-dbc9-3670-e4c9589b4d1f@redhat.com> <182708df-1082-0678-49b2-15d0199f20df@redhat.com> <7f80eeed-f5d3-8c6f-1b8c-87b7a449975c@redhat.com> In-Reply-To: From: Yongji Xie Date: Wed, 2 Dec 2020 11:29:33 +0800 Message-ID: Subject: Re: [External] Re: [PATCH 0/7] Introduce vdpa management tool To: Parav Pandit Cc: Jason Wang , "virtualization@lists.linux-foundation.org" , "Michael S. Tsirkin" , Eli Cohen , "netdev@vger.kernel.org" Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, Dec 1, 2020 at 11:59 PM Parav Pandit wrote: > > > > > From: Yongji Xie > > Sent: Tuesday, December 1, 2020 7:49 PM > > > > On Tue, Dec 1, 2020 at 7:32 PM Parav Pandit wrote: > > > > > > > > > > > > > From: Yongji Xie > > > > Sent: Tuesday, December 1, 2020 3:26 PM > > > > > > > > On Tue, Dec 1, 2020 at 2:25 PM Jason Wang > > wrote: > > > > > > > > > > > > > > > On 2020/11/30 =E4=B8=8B=E5=8D=883:07, Yongji Xie wrote: > > > > > >>> Thanks for adding me, Jason! > > > > > >>> > > > > > >>> Now I'm working on a v2 patchset for VDUSE (vDPA Device in > > > > > >>> Userspace) [1]. This tool is very useful for the vduse device= . > > > > > >>> So I'm considering integrating this into my v2 patchset. But > > > > > >>> there is one problem=EF=BC=9A > > > > > >>> > > > > > >>> In this tool, vdpa device config action and enable action are > > > > > >>> combined into one netlink msg: VDPA_CMD_DEV_NEW. But in > > vduse > > > > > >>> case, it needs to be splitted because a chardev should be > > > > > >>> created and opened by a userspace process before we enable th= e > > > > > >>> vdpa device (call vdpa_register_device()). > > > > > >>> > > > > > >>> So I'd like to know whether it's possible (or have some plans= ) > > > > > >>> to add two new netlink msgs something like: > > > > > >>> VDPA_CMD_DEV_ENABLE > > > > and > > > > > >>> VDPA_CMD_DEV_DISABLE to make the config path more flexible. > > > > > >>> > > > > > >> Actually, we've discussed such intermediate step in some early > > > > > >> discussion. It looks to me VDUSE could be one of the users of = this. > > > > > >> > > > > > >> Or I wonder whether we can switch to use anonymous inode(fd) > > > > > >> for VDUSE then fetching it via an VDUSE_GET_DEVICE_FD ioctl? > > > > > >> > > > > > > Yes, we can. Actually the current implementation in VDUSE is > > > > > > like this. But seems like this is still a intermediate step. > > > > > > The fd should be binded to a name or something else which need > > > > > > to be configured before. > > > > > > > > > > > > > > > The name could be specified via the netlink. It looks to me the > > > > > real issue is that until the device is connected with a userspace= , > > > > > it can't be used. So we also need to fail the enabling if it does= n't > > opened. > > > > > > > > > > > > > Yes, that's true. So you mean we can firstly try to fetch the fd > > > > binded to a name/vduse_id via an VDUSE_GET_DEVICE_FD, then use the > > > > name/vduse_id as a attribute to create vdpa device? It looks fine t= o me. > > > > > > I probably do not well understand. I tried reading patch [1] and few = things > > do not look correct as below. > > > Creating the vdpa device on the bus device and destroying the device = from > > the workqueue seems unnecessary and racy. > > > > > > It seems vduse driver needs > > > This is something should be done as part of the vdpa dev add command, > > instead of connecting two sides separately and ensuring race free acces= s to > > it. > > > > > > So VDUSE_DEV_START and VDUSE_DEV_STOP should possibly be avoided. > > > > > > > Yes, we can avoid these two ioctls with the help of the management tool= . > > > > > $ vdpa dev add parentdev vduse_mgmtdev type net name foo2 > > > > > > When above command is executed it creates necessary vdpa device foo2 > > on the bus. > > > When user binds foo2 device with the vduse driver, in the probe(), it > > creates respective char device to access it from user space. > > > I see. So vduse cannot work with any existing vdpa devices like ifc, mlx5= or netdevsim. > It has its own implementation similar to fuse with its own backend of cho= ice. > More below. > > > But vduse driver is not a vdpa bus driver. It works like vdpasim driver= , but > > offloads the data plane and control plane to a user space process. > > In that case to draw parallel lines, > > 1. netdevsim: > (a) create resources in kernel sw > (b) datapath simulates in kernel > > 2. ifc + mlx5 vdpa dev: > (a) creates resource in hw > (b) data path is in hw > > 3. vduse: > (a) creates resources in userspace sw > (b) data path is in user space. > hence creates data path resources for user space. > So char device is created, removed as result of vdpa device creation. > > For example, > $ vdpa dev add parentdev vduse_mgmtdev type net name foo2 > > Above command will create char device for user space. > > Similar command for ifc/mlx5 would have created similar channel for rest = of the config commands in hw. > vduse channel =3D char device, eventfd etc. > ifc/mlx5 hw channel =3D bar, irq, command interface etc > Netdev sim channel =3D sw direct calls > > Does it make sense? In my understanding, to make vdpa work, we need a backend (datapath resources) and a frontend (a vdpa device attached to a vdpa bus). In the above example, it looks like we use the command "vdpa dev add ..." to create a backend, so do we need another command to create a frontend? Thanks, Yongji