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[209.132.180.67]) by mx.google.com with ESMTP id m17si1341221otk.109.2020.02.13.07.00.24; Thu, 13 Feb 2020 07:00:36 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=ODyxmkzu; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727575AbgBMO7I (ORCPT + 99 others); Thu, 13 Feb 2020 09:59:08 -0500 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:33322 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727347AbgBMO7I (ORCPT ); Thu, 13 Feb 2020 09:59:08 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1581605946; 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=CHiRb+twyxpf3W0EcmM5/eTdbL/em0EAL1gxZi7gnIQ=; b=ODyxmkzurI+RWNGd+/OIwxeJjG1L4pTuUGH1jQfymp/gttxA02ui7rXZ1+IZCxrC0tXYAj xRlqJHiiVY1i6mh3TkhgNrlN/bkMslrSRx+Rl6lB1CRaF9IEI/mAJd2gL8XJniUKYjeB+C 14N2XgAPwY5LTyRp6BbIgGNNgI+ZpcQ= 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-407-q6vGNjygM1KilbmYGgqpcw-1; Thu, 13 Feb 2020 09:59:05 -0500 X-MC-Unique: q6vGNjygM1KilbmYGgqpcw-1 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 4B6948EC825; Thu, 13 Feb 2020 14:59:02 +0000 (UTC) Received: from [10.72.12.120] (ovpn-12-120.pek2.redhat.com [10.72.12.120]) by smtp.corp.redhat.com (Postfix) with ESMTP id 892AF9008B; Thu, 13 Feb 2020 14:58:46 +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> From: Jason Wang Message-ID: Date: Thu, 13 Feb 2020 22:58:44 +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: <20200213134128.GV4271@mellanox.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 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=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 used >>> by vdpa, so class seems the right choice >>> >>> Jason >> Yes, but my understanding is class and bus are mutually exclusive. So = 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=20 semantic is different. So it looks to me that use bus complies what=20 class.rst said: " Each device class defines a set of semantics and a programming interface that devices of that class adhere to. Device drivers are the implementation of that programming interface for a particular device on a particular 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. This is because we want vDPA to be generic for being used by different=20 drivers which is not limited to vhost-vdpa. E.g in this series, it=20 allows vDPA to be used by kernel virtio drivers. And in the future, we=20 will probably introduce more drivers in the future. > > 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).=20 And what the driver needs is to present a vDPA device to virtual vDPA=20 bus on top. Thanks > > I don't see a reason for VDPA to be creating busses.. > > Jason >