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 83525C64E8A for ; Wed, 2 Dec 2020 09:23:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 18D5B20C56 for ; Wed, 2 Dec 2020 09:23:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729222AbgLBJWs (ORCPT ); Wed, 2 Dec 2020 04:22:48 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51606 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728306AbgLBJWr (ORCPT ); Wed, 2 Dec 2020 04:22:47 -0500 Received: from mail-ej1-x643.google.com (mail-ej1-x643.google.com [IPv6:2a00:1450:4864:20::643]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F27D3C0613CF for ; Wed, 2 Dec 2020 01:22:06 -0800 (PST) Received: by mail-ej1-x643.google.com with SMTP id ga15so2752240ejb.4 for ; Wed, 02 Dec 2020 01:22:06 -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=zLyMVWmuUt0sNAIE4pEx4EW9+sOWKqUa1L/RrHU1WNI=; b=fFCSNGSm1Fj+yumvHUT+yal2v7tzqbr4JTN1ETEIEcrKXtXjpMcLChUsYH1i87o/Jt YadzjHvJjoK/4T5jM1/42JX0R5e+34f09UvlhqNenJNk40/iqG7khbMqkw/QpMSu7Pf4 9wzANNtAW1lWkaveIJHG34CgSHpPzLaJB+DjpuxBeMKEB0VEwGcsscphXZ+9bSMOLT69 9mpQDwfsklE4sv6zkEsecxupe7W4WFW7X/lvQ6XwKkVdVQAfM29RZVD/UJ7F0mj66ibr Pt3EkNIWUcSa3HvnbdwVo5KKgSDoEZohiSADjS+BOgTtpiG8aALTF3sCjyhGztAljFV5 lx1Q== 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=zLyMVWmuUt0sNAIE4pEx4EW9+sOWKqUa1L/RrHU1WNI=; b=g1GLfMkQht739Igzx/FcDboMB9kL4b1dxfbt7sdxdZbcSML7MkxIsK1hkbQBlVs1H0 ZfmvcerzZnHaQGlHiat/z0zwtK/s/edjCDxcYqnswO8TTBSqHvBa/jW1bPoApGj6eBs1 KCZVkPAK6mTIqO/ZYM9KgU8ZSbBQBhwvKdppYaFC7UCTQNrGGp/q+lRpAVHLAZGJ0v3c tc+mOZ2L0Djql6G6GpyzGvQ5vFB+tO1FvOm7uclbZvlXSbffeEvWMHiQZEmOhbYPboyq XeJMr2y+3gSe3bivJVo1q2fwv7JI7F2oc9M4jxIcpZoXmxOwtP6I2P2x0UzqFbdfzNgC cqrA== X-Gm-Message-State: AOAM530PWjva7s9yPZHtbXbeRxc7sZoQjiiboz2pFYZOIV9GMObFtQcq 8Pocdco+mi7ErpgNjRuvQVXnuKsMKQQEyAG/uaQL X-Google-Smtp-Source: ABdhPJxdITNa0qzyDp825wlCjh4k9jEKH1+h6zLyoeQC29CjR7y5ZFhKYfU1tZM1OoS3UyX5qDhYzLY32I9rF9qozvU= X-Received: by 2002:a17:906:a218:: with SMTP id r24mr1375633ejy.372.1606900925614; Wed, 02 Dec 2020 01:22:05 -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 17:21:54 +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 Wed, Dec 2, 2020 at 12:53 PM Parav Pandit wrote: > > > > > From: Yongji Xie > > Sent: Wednesday, December 2, 2020 9:00 AM > > > > 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 wrot= e: > > > > > > > > > > > > > > > > > > > > > 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 i= n > > > > > > > >>> Userspace) [1]. This tool is very useful for the vduse de= vice. > > > > > > > >>> 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 enabl= e > > > > > > > >>> the 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 flexibl= e. > > > > > > > >>> > > > > > > > >> 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_DEVI= CE_FD > > ioctl? > > > > > > > >> > > > > > > > > Yes, we can. Actually the current implementation in VDUSE i= s > > > > > > > > like this. But seems like this is still a intermediate ste= p. > > > > > > > > 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 doesn't > > > > opened. > > > > > > > > > > > > > > > > > > > Yes, that's true. So you mean we can firstly try to fetch the f= d > > > > > > 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 look= s fine to > > 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 > > > > access 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= choice. > > > 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 spa= ce 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 r= est 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 th= e 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 fronten= d? > > > For block device there is certainly some backend to process the IOs. > Sometimes backend to be setup first, before its front end is exposed. Yes, the backend need to be setup firstly, this is vendor device specific, not vdpa specific. > "vdpa dev add" is the front end command who connects to the backend (impl= icitly) for network device. > > vhost->vdpa_block_device->backend_io_processor (usr,hw,kernel). > > And it needs a way to connect to backend when explicitly specified during= creation time. > Something like, > $ vdpa dev add parentdev vdpa_vduse type block name foo3 handle > In above example some vendor device specific unique handle is passed base= d on backend setup in hardware/user space. > Yes, we can work like this. After we setup a backend through an anonymous inode(fd) from /dev/vduse, we can get a unique handle. Then use it to create a frontend which will connect to the specific backend. > In below 3 examples, vdpa block simulator is connecting to backend block = or file. > > $ vdpa dev add parentdev vdpa_blocksim type block name foo4 blockdev /dev= /zero > > $ vdpa dev add parentdev vdpa_blocksim type block name foo5 blockdev /dev= /sda2 size=3D100M offset=3D10M > > $ vdpa dev add parentdev vdpa_block filebackend_sim type block name foo6 = file /root/file_backend.txt > > Or may be backend connects to the created vdpa device is bound to the dri= ver. > Can vduse attach to the created vdpa block device through the char device= and establish the channel to receive IOs, and to setup the block config sp= ace? > How to create the vdpa block device? If we use the command "vdpa dev add..", the command will hang there until a vduse process attaches to the vdpa block device. Thanks, Yongji