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 B7618C4332B for ; Fri, 20 Mar 2020 09:18:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8732020739 for ; Fri, 20 Mar 2020 09:18:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="cuPLN+gV" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727047AbgCTJSA (ORCPT ); Fri, 20 Mar 2020 05:18:00 -0400 Received: from us-smtp-delivery-74.mimecast.com ([216.205.24.74]:30542 "EHLO us-smtp-delivery-74.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726527AbgCTJR7 (ORCPT ); Fri, 20 Mar 2020 05:17:59 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1584695877; 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=RA5PQJx7YSzfov+hXIk77JXzaA1GFtyaspVCOD3A7E4=; b=cuPLN+gVp+iQr5HEnhjyXe/arLKu7aptkuRpCwT/wo+GikaaKbLSIFTGiQSbrEQeCfC/5v K9uhNjznN+oSd8f+0TxMqlCYabba34HTcrGODyHiSc6VlagP7s2bQuHlbZ4UWMdxtCgv+b rVH8CvNnXAkkgUsabYHbyqBJhdVsmgQ= 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-5-fCe8-lhaPCenFclKrajMdw-1; Fri, 20 Mar 2020 05:17:54 -0400 X-MC-Unique: fCe8-lhaPCenFclKrajMdw-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id E7B6710753FB; Fri, 20 Mar 2020 09:17:50 +0000 (UTC) Received: from [10.72.13.250] (ovpn-13-250.pek2.redhat.com [10.72.13.250]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8A4D210493BD; Fri, 20 Mar 2020 09:17:32 +0000 (UTC) Subject: Re: [PATCH V6 8/8] virtio: Intel IFC VF driver for VDPA 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, maxime.coquelin@redhat.com, cunming.liang@intel.com, zhihong.wang@intel.com, rob.miller@broadcom.com, xiao.w.wang@intel.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, gdawar@xilinx.com, saugatm@xilinx.com, vmireyno@marvell.com, Bie Tiwei References: <20200318080327.21958-1-jasowang@redhat.com> <20200318080327.21958-9-jasowang@redhat.com> <20200318122255.GG13183@mellanox.com> <30359bae-d66a-0311-0028-d7d33b8295f2@redhat.com> <20200319130239.GW13183@mellanox.com> From: Jason Wang Message-ID: <055f10a8-0b7d-ec2b-4fd4-d47ba96ddd5f@redhat.com> Date: Fri, 20 Mar 2020 17:17:31 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20200319130239.GW13183@mellanox.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Content-Transfer-Encoding: quoted-printable Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 2020/3/19 =E4=B8=8B=E5=8D=889:02, Jason Gunthorpe wrote: > On Thu, Mar 19, 2020 at 04:14:37PM +0800, Jason Wang wrote: >> On 2020/3/18 =E4=B8=8B=E5=8D=888:22, Jason Gunthorpe wrote: >>> On Wed, Mar 18, 2020 at 04:03:27PM +0800, Jason Wang wrote: >>>> From: Zhu Lingshan >>>> + >>>> +static int ifcvf_vdpa_attach(struct ifcvf_adapter *adapter) >>>> +{ >>>> + int ret; >>>> + >>>> + adapter->vdpa_dev =3D vdpa_alloc_device(adapter->dev, adapter->de= v, >>>> + &ifc_vdpa_ops); >>>> + if (IS_ERR(adapter->vdpa_dev)) { >>>> + IFCVF_ERR(adapter->dev, "Failed to init ifcvf on vdpa bus"); >>>> + put_device(&adapter->vdpa_dev->dev); >>>> + return -ENODEV; >>>> + } >>> The point of having an alloc call is so that the drivers >>> ifcvf_adaptor memory could be placed in the same struct - eg use >>> container_of to flip between them, and have a kref for both memories. >>> >>> It seem really weird to have an alloc followed immediately by >>> register. >> >> I admit the ifcvf_adapter is not correctly ref-counted. What you sugge= st >> should work. But it looks to me the following is more cleaner since th= e >> members of ifcvf_adapter are all related to PCI device not vDPA itself= . > I've done it both ways (eg tpm is as you describe, ib is using alloc). > > I tend to prefer the alloc method today, allowing the driver memory to > have a proper refcount makes the driver structure usable with RCU and > allows simple solutions to some tricky cases. It is a bit hard to > switch to this later.. > >> - keep the current layout of ifcvf_adapter >> - merge vdpa_alloc_device() and vdpa_register_device() >> - use devres to bind ifcvf_adapter refcnt/lifcycle to the under PCI de= vice > This is almost what tpm does. Keep in mind the lifecycle with devm is > just slightly past the driver remove call, so remove still > must revoke all external references to the memory. > > The merging alloc and register rarely works out, the register must be > the very last thing done, and usually you need the subsystem pointer > to do pre-registration setup in anything but the most trivial of > subsystems and drivers. > >> If we go for the container_of method, we probably need >> >> - accept a size of parent parent structure in vdpa_alloc_device() and >> mandate vdpa_device to be the first member of ifcvf_adapter >> - we need provide a way to free resources of parent structure when we >> destroy vDPA device > Yep. netdev and rdma work this way with a free memory callback in the > existing ops structures. > > Jason Ok, I get your points now. Will go for way of container_of in next versio= n. Thanks