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=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 53D11C17444 for ; Mon, 11 Nov 2019 03:46:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 29E482075C for ; Mon, 11 Nov 2019 03:46:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=netronome-com.20150623.gappssmtp.com header.i=@netronome-com.20150623.gappssmtp.com header.b="SOIlwK5m" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726912AbfKKDqH (ORCPT ); Sun, 10 Nov 2019 22:46:07 -0500 Received: from mail-pf1-f196.google.com ([209.85.210.196]:44609 "EHLO mail-pf1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726749AbfKKDqG (ORCPT ); Sun, 10 Nov 2019 22:46:06 -0500 Received: by mail-pf1-f196.google.com with SMTP id q26so9697475pfn.11 for ; Sun, 10 Nov 2019 19:46:06 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=netronome-com.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:in-reply-to:references :organization:mime-version:content-transfer-encoding; bh=AqhM9u1bzCnw7qhUa4mHnqgFKW6TzFtxLFQ8BM/epMs=; b=SOIlwK5mjoyFW/tXHeVmYa4IK11qYjcalG4RreXwkjwE6o05256yuTEZ4tqlNqlfGD shDyAVTcAHfRAPjk0HgUUKt78RLGstgu/5t3Xt/YTXXdCjfzs9mSIpOwHV2fBRUr4arr AimZYIbgl6d67DxMbwVkHuQhEjqCZvV6SfPQ8uDxtE9RoCr+xi1KecnA+sD5oHcnju5t dFGKlm2zNCLvQWMxLDvuJZZCdRP6iqrhDPSdCZijkrYJ/JogxXmCgPyhTq2g5iRb3//X 4ZXSpxzZA92++uyYySNgIfmELbtXgsdpqUoyYO5dKpkYYGsBdF1TrYchrVlxN9pAY8EW +iRA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:in-reply-to :references:organization:mime-version:content-transfer-encoding; bh=AqhM9u1bzCnw7qhUa4mHnqgFKW6TzFtxLFQ8BM/epMs=; b=rRrlec3pqTg8H5aKg+gmIEkCPc/bE76tkhuXkr2OuKqEXcK2ipEdquWEBfTkUIfYtF wQzhRLu6KEycwP5816ryfD6KUK90QoiIWUquFLRyYEb25tHVyArIp1YxgezNac0y91HT X01OulWbKMkLYHE9NLt7Uh+5gOmSfh4vHlU9vJ5OG/xuOH5qdHkngHnYraWGlPGdoGY8 /rfvXVa5eA9HrDduNrd/Dd1kMD9feqMbinHlRsYrpDZ2UTgkbuU1veAVR9jTahmsdpKD 4SwhA1FxI4On97ufIAKuLT8YSiHNfW44noTFZMGARbJ+13Vr+atTp30661iDVE+/b/yR 35xg== X-Gm-Message-State: APjAAAU9uaEiVFVqTgS+4U77Qv/wjObK5Xcnc5QyP3thDWqcsi1m3G+M fuYhtk6QBb4YkFba7qnvqIWEMg== X-Google-Smtp-Source: APXvYqyvsmmGRubdY0eCp6Hd53IA2QHIUdVnV/J9ottQSlb0FTBMpy9oBY7rLSA0rhkW3bsD3dRtVQ== X-Received: by 2002:a63:86c6:: with SMTP id x189mr25278222pgd.341.1573443966052; Sun, 10 Nov 2019 19:46:06 -0800 (PST) Received: from cakuba (c-73-202-202-92.hsd1.ca.comcast.net. [73.202.202.92]) by smtp.gmail.com with ESMTPSA id w8sm12009631pfi.60.2019.11.10.19.46.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 10 Nov 2019 19:46:05 -0800 (PST) Date: Sun, 10 Nov 2019 19:46:01 -0800 From: Jakub Kicinski To: "gregkh@linuxfoundation.org" Cc: Jason Gunthorpe , Parav Pandit , Jiri Pirko , David M , "alex.williamson@redhat.com" , "davem@davemloft.net" , "kvm@vger.kernel.org" , "netdev@vger.kernel.org" , Saeed Mahameed , "kwankhede@nvidia.com" , "leon@kernel.org" , "cohuck@redhat.com" , Jiri Pirko , "linux-rdma@vger.kernel.org" , Or Gerlitz Subject: Re: [PATCH net-next 00/19] Mellanox, mlx5 sub function support Message-ID: <20191110194601.0d6ed1a0@cakuba> In-Reply-To: <20191110091855.GE1435668@kroah.com> References: <20191107160448.20962-1-parav@mellanox.com> <20191107153234.0d735c1f@cakuba.netronome.com> <20191108121233.GJ6990@nanopsycho> <20191108144054.GC10956@ziepe.ca> <20191108111238.578f44f1@cakuba> <20191108201253.GE10956@ziepe.ca> <20191108134559.42fbceff@cakuba> <20191109004426.GB31761@ziepe.ca> <20191109092747.26a1a37e@cakuba> <20191110091855.GE1435668@kroah.com> Organization: Netronome Systems, Ltd. MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Sun, 10 Nov 2019 10:18:55 +0100, gregkh@linuxfoundation.org wrote: > > What I'm missing is why is it so bad to have a driver register to > > multiple subsystems. > > Because these PCI devices seem to do "different" things all in one PCI > resource set. Blame the hardware designers :) See below, I don't think you can blame the HW designers in this particular case :) > > For the nfp I think the _real_ reason to have a bus was that it > > was expected to have some out-of-tree modules bind to it. Something > > I would not encourage :) > > That's not ok, and I agree with you. > > But there seems to be some more complex PCI devices that do lots of > different things all at once. Kind of like a PCI device that wants to > be both a keyboard and a storage device at the same time (i.e. a button > on a disk drive...) The keyboard which is also a storage device may be a clear cut case where multiple devices were integrated into one bus endpoint. The case with these advanced networking adapters is a little different in that they are one HW device which has oodles of FW implementing clients or acceleration for various networking protocols. The nice thing about having a fake bus is you can load out-of-tree drivers to operate extra protocols quite cleanly. I'm not saying that's what the code in question is doing, I'm saying I'd personally like to understand the motivation more clearly before every networking driver out there starts spawning buses. The only argument I've heard so far for the separate devices is reloading subset of the drivers, which I'd rate as moderately convincing.