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=-4.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 8F016C4742C for ; Mon, 16 Nov 2020 15:37:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 53FF72076E for ; Mon, 16 Nov 2020 15:37:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="o536oL+2" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731323AbgKPPhY (ORCPT ); Mon, 16 Nov 2020 10:37:24 -0500 Received: from mail.kernel.org ([198.145.29.99]:57200 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730415AbgKPPhX (ORCPT ); Mon, 16 Nov 2020 10:37:23 -0500 Received: from mail-oo1-f41.google.com (mail-oo1-f41.google.com [209.85.161.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B2B9522265; Mon, 16 Nov 2020 15:37:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605541042; bh=E8sdLeoXIzuGmOa5OnMrHgj2yXn2UCzO0W2afC9rPuk=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=o536oL+2jBT8rxRsfC+tXAjv5gHqLzcLVB31sbOHhgsVNlS+Geq0O1pZzwyVYAlX4 GcZhqkXekHID+qw9bCtRwibJo7SFgfT6j9ItPu+Fa1fhCIF5rtMtt7ew3966SBrfZm m5K3fr6EQlAfSWBq4AZpKRR5x+KLsMvCxrsC9Ots= Received: by mail-oo1-f41.google.com with SMTP id l10so3989210oom.6; Mon, 16 Nov 2020 07:37:22 -0800 (PST) X-Gm-Message-State: AOAM531TRRKbqJjhGfBD9H0VB0Ksuk0lNNuP9cISV0ejm7vWjTjyKjMm SqnQvXEnG3ZQbVHavpnusNzh9qudSMII0mUPVZM= X-Google-Smtp-Source: ABdhPJwM0C/5+mYGkprp6MGo45Jg+Y4cMg6i4Udv3mmMRAH/nnzs8rxK08SMGeEcf0ooEr/jW8gZH1jSiUBbnEh2gOI= X-Received: by 2002:a4a:a217:: with SMTP id m23mr10462852ool.26.1605541041921; Mon, 16 Nov 2020 07:37:21 -0800 (PST) MIME-Version: 1.0 References: <20200930153519.7282-16-kishon@ti.com> <30c8f7a1-baa5-1eb4-d2c2-9a13be896f0f@ti.com> <5a9115c8-322e-ffd4-6274-ae98c375b21d@ti.com> In-Reply-To: From: Arnd Bergmann Date: Mon, 16 Nov 2020 16:37:05 +0100 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v7 15/18] NTB: Add support for EPF PCI-Express Non-Transparent Bridge To: Kishon Vijay Abraham I Cc: Sherry Sun , "bhelgaas@google.com" , Jonathan Corbet , "lorenzo.pieralisi@arm.com" , "arnd@arndb.de" , "jdmason@kudzu.us" , "dave.jiang@intel.com" , "allenbh@gmail.com" , "tjoseph@cadence.com" , Rob Herring , "gregkh@linuxfoundation.org" , "linux-pci@vger.kernel.org" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-ntb@googlegroups.com" Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 16, 2020 at 6:19 AM Kishon Vijay Abraham I wrote: > On 12/11/20 6:54 pm, Arnd Bergmann wrote: > > > > This looks very promising indeed, I need to read up on the whole > > discussion there. I also see your slides at [1] that help do explain some > > of it. I have one fundamental question that I can't figure out from > > the description, maybe you can help me here: > > > > How is the configuration managed, taking the EP case as an > > example? Your UseCase1 example sounds like the system that owns > > the EP hardware is the one that turns the EP into a vhost device, > > and creates a vhost-rpmsg device on top, while the RC side would > > probe the pci-vhost and then detect a virtio-rpmsg device to talk to. > > That's correct. Slide no 9 in [1] should give the layering details. > > > Can it also do the opposite, so you end up with e.g. a virtio-net > > device on the EP side and vhost-net on the RC? > > Unfortunately no. Again referring slide 9 in [1], we only have > vhost-pci-epf on the EP side which only creates a "vhost_dev" to deal > with vhost side of things. For doing the opposite, we'd need to create > virtio-pci-epf for EP side that interacts with core virtio (and also the > corresponding vhost back end on PCI host). Ok, I see. So I think this is the opposite of drivers/misc/mic and the bluefield driver were using, so we would probably end up needing both. Then again, I guess the NTB driver would give us the functionality for free, if it shows a symmetric link? Arnd