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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 0A6A7C35242 for ; Fri, 14 Feb 2020 03:23:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B82E720661 for ; Fri, 14 Feb 2020 03:23:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="W7uwClEe" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728468AbgBNDXy (ORCPT ); Thu, 13 Feb 2020 22:23:54 -0500 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:27034 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728089AbgBNDXx (ORCPT ); Thu, 13 Feb 2020 22:23:53 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1581650632; 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=WiBwyrz6cX+xE4nXs+94fQKaFw5y/aQb69mQMK4gGl0=; b=W7uwClEemERc8oqUMk4qYGC2Cvjz/RryTBJnVU3EnnQVRa2yOJ6SxEKrWMy5cqe/REoQSl VaoifEFf3xu4qH0nlGRJvK4khLaVdG5AVIVbqIXqsBx+QdYoauKS0PFmBqJL5Nu+ujaOva 36pXuM10anrv0L7OtFQJomoEyY/FK/8= 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-423-fdAi4kdyMtWwFgGd05oe8Q-1; Thu, 13 Feb 2020 22:23:51 -0500 X-MC-Unique: fdAi4kdyMtWwFgGd05oe8Q-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 45C388017CC; Fri, 14 Feb 2020 03:23:48 +0000 (UTC) Received: from [10.72.13.213] (ovpn-13-213.pek2.redhat.com [10.72.13.213]) by smtp.corp.redhat.com (Postfix) with ESMTP id E0CD338A; Fri, 14 Feb 2020 03:23:29 +0000 (UTC) Subject: Re: [PATCH V2 3/5] vDPA: introduce vDPA bus To: Jason Gunthorpe Cc: mst@redhat.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, tiwei.bie@intel.com, maxime.coquelin@redhat.com, cunming.liang@intel.com, zhihong.wang@intel.com, rob.miller@broadcom.com, xiao.w.wang@intel.com, haotian.wang@sifive.com, lingshan.zhu@intel.com, eperezma@redhat.com, lulu@redhat.com, parav@mellanox.com, kevin.tian@intel.com, stefanha@redhat.com, rdunlap@infradead.org, hch@infradead.org, aadam@redhat.com, jiri@mellanox.com, shahafs@mellanox.com, hanand@xilinx.com, mhabets@solarflare.com References: <20200210035608.10002-1-jasowang@redhat.com> <20200210035608.10002-4-jasowang@redhat.com> <20200211134746.GI4271@mellanox.com> <20200212125108.GS4271@mellanox.com> <12775659-1589-39e4-e344-b7a2c792b0f3@redhat.com> <20200213134128.GV4271@mellanox.com> <20200213150542.GW4271@mellanox.com> From: Jason Wang Message-ID: <8b3e6a9c-8bfd-fb3c-12a8-2d6a3879f1ae@redhat.com> Date: Fri, 14 Feb 2020 11:23:27 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20200213150542.GW4271@mellanox.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/2/13 =E4=B8=8B=E5=8D=8811:05, Jason Gunthorpe wrote: > On Thu, Feb 13, 2020 at 10:58:44PM +0800, Jason Wang wrote: >> On 2020/2/13 =E4=B8=8B=E5=8D=889:41, Jason Gunthorpe wrote: >>> On Thu, Feb 13, 2020 at 11:34:10AM +0800, Jason Wang wrote: >>> >>>>> You have dev, type or >>>>> class to choose from. Type is rarely used and doesn't seem to be us= ed >>>>> by vdpa, so class seems the right choice >>>>> >>>>> Jason >>>> Yes, but my understanding is class and bus are mutually exclusive. S= o we >>>> can't add a class to a device which is already attached on a bus. >>> While I suppose there are variations, typically 'class' devices are >>> user facing things and 'bus' devices are internal facing (ie like a >>> PCI device) >> >> Though all vDPA devices have the same programming interface, but the >> semantic is different. So it looks to me that use bus complies what >> class.rst said: >> >> " >> >> Each device class defines a set of semantics and a programming interfa= ce >> that devices of that class adhere to. Device drivers are the >> implementation of that programming interface for a particular device o= n >> a particular bus. >> >> " > Here we are talking about the /dev/XX node that provides the > programming interface. I'm confused here, are you suggesting to use class to create char device=20 in vhost-vdpa? That's fine but the comment should go for vhost-vdpa patch= . > All the vdpa devices have the same basic > chardev interface and discover any semantic variations 'in band' That's not true, char interface is only used for vhost. Kernel virtio=20 driver does not need char dev but a device on the virtio bus. > >>> So why is this using a bus? VDPA is a user facing object, so the >>> driver should create a class vhost_vdpa device directly, and that >>> driver should live in the drivers/vhost/ directory. >> =20 >> This is because we want vDPA to be generic for being used by different >> drivers which is not limited to vhost-vdpa. E.g in this series, it all= ows >> vDPA to be used by kernel virtio drivers. And in the future, we will >> probably introduce more drivers in the future. > I don't see how that connects with using a bus. This is demonstrated in the virito-vdpa driver. So if you want to use=20 kernel virito driver for vDPA device, a bus is most straight forward. > > Every class of virtio traffic is going to need a special HW driver to > enable VDPA, that special driver can create the correct vhost side > class device. Are you saying, e.g it's the charge of IFCVF driver to create vhost char=20 dev and other stuffs? > >>> For the PCI VF case this driver would bind to a PCI device like >>> everything else >>> >>> For our future SF/ADI cases the driver would bind to some >>> SF/ADI/whatever device on a bus. >> All these driver will still be bound to their own bus (PCI or other). = And >> what the driver needs is to present a vDPA device to virtual vDPA bus = on >> top. > Again, I can't see any reason to inject a 'vdpa virtual bus' on > top. That seems like mis-using the driver core. I don't think so. Vhost is not the only programming interface for vDPA.=20 We don't want a device that can only work for userspace drivers and only=20 have a single set of userspace APIs. Thanks > > Jason >