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=-2.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,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 74984C432C0 for ; Tue, 19 Nov 2019 04:08:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 416ED20730 for ; Tue, 19 Nov 2019 04:08:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="OgEkU7+0" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727588AbfKSEIn (ORCPT ); Mon, 18 Nov 2019 23:08:43 -0500 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:31529 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727538AbfKSEIn (ORCPT ); Mon, 18 Nov 2019 23:08:43 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1574136522; 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=4KHnBphqylub5AyGngwSZIrs22cExMLF/6Fas0WmnvQ=; b=OgEkU7+0aIyvooI55kRm0zklnwbMKuvz/Q/9kLoQ7M+yjt5EW98pEfZpA9kllzJJK44jS8 vY1a79PhqxQRyfm6qcmbsOwWfmlOYdi6MbSJO8HB6EarYSEF9bb3hQG/6JhGWdxhULcOFW igqDGpDWAaZnPrsiRKusi41ASSHUykQ= 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-192-9KDg-R-QMyC7gJzz-rja_w-1; Mon, 18 Nov 2019 23:08:39 -0500 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 619B71005500; Tue, 19 Nov 2019 04:08:37 +0000 (UTC) Received: from [10.72.12.132] (ovpn-12-132.pek2.redhat.com [10.72.12.132]) by smtp.corp.redhat.com (Postfix) with ESMTP id DA718608E2; Tue, 19 Nov 2019 04:08:16 +0000 (UTC) Subject: Re: [net-next v2 1/1] virtual-bus: Implementation of Virtual Bus To: Parav Pandit , Jeff Kirsher , "davem@davemloft.net" , "gregkh@linuxfoundation.org" Cc: Dave Ertman , "netdev@vger.kernel.org" , "linux-rdma@vger.kernel.org" , "nhorman@redhat.com" , "sassmann@redhat.com" , "jgg@ziepe.ca" , Kiran Patil , "Michael S. Tsirkin" , Alex Williamson , "Bie, Tiwei" References: <20191115223355.1277139-1-jeffrey.t.kirsher@intel.com> From: Jason Wang Message-ID: Date: Tue, 19 Nov 2019 12:08:15 +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: Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-MC-Unique: 9KDg-R-QMyC7gJzz-rja_w-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable Sender: linux-rdma-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org On 2019/11/16 =E4=B8=8A=E5=8D=887:25, Parav Pandit wrote: > Hi Jeff, > >> From: Jeff Kirsher >> Sent: Friday, November 15, 2019 4:34 PM >> >> From: Dave Ertman >> >> This is the initial implementation of the Virtual Bus, virtbus_device an= d >> virtbus_driver. The virtual bus is a software based bus intended to sup= port >> lightweight devices and drivers and provide matching between them and >> probing of the registered drivers. >> >> The primary purpose of the virual bus is to provide matching services an= d to >> pass the data pointer contained in the virtbus_device to the virtbus_dri= ver >> during its probe call. This will allow two separate kernel objects to m= atch up >> and start communication. >> > It is fundamental to know that rdma device created by virtbus_driver will= be anchored to which bus for an non abusive use. > virtbus or parent pci bus? > I asked this question in v1 version of this patch. > > Also since it says - 'to support lightweight devices', documenting that i= nformation is critical to avoid ambiguity. > > Since for a while I am working on the subbus/subdev_bus/xbus/mdev [1] wha= tever we want to call it, it overlaps with your comment about 'to support l= ightweight devices'. > Hence let's make things crystal clear weather the purpose is 'only matchi= ng service' or also 'lightweight devices'. > If this is only matching service, lets please remove lightweight devices = part.. Yes, if it's matching + lightweight device, its function is almost a=20 duplication of mdev. And I'm working on extending mdev[1] to be a=20 generic module to support any types of virtual devices a while. The=20 advantage of mdev is: 1) ready for the userspace driver (VFIO based) 2) have a sysfs/GUID based management interface So for 1, it's not clear that how userspace driver would be supported=20 here, or it's completely not being accounted in this series? For 2, it=20 looks to me that this series leave it to the implementation, this means=20 management to learn several vendor specific interfaces which seems a burden= . Note, technically Virtual Bus could be implemented on top of [1] with=20 the full lifecycle API. [1] https://lkml.org/lkml/2019/11/18/261 > > You additionally need modpost support for id table integration to modifo,= modprobe and other tools. > A small patch similar to this one [2] is needed. > Please include in the series. > > [..] And probably a uevent method. But rethinking of this, matching through a=20 single virtual bus seems not good. What if driver want to do some=20 specific matching? E.g for virtio, we may want a vhost-net driver that=20 only match networking device. With a single bus, it probably means you=20 need another bus on top and provide the virtio specific matching there.=20 This looks not straightforward as allowing multiple type of buses. Thanks