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 E0E7CC55ABD for ; Tue, 10 Nov 2020 14:59:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7D328206B2 for ; Tue, 10 Nov 2020 14:59:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="O/3QTe6U" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730981AbgKJO7a (ORCPT ); Tue, 10 Nov 2020 09:59:30 -0500 Received: from mail.kernel.org ([198.145.29.99]:49562 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730917AbgKJO72 (ORCPT ); Tue, 10 Nov 2020 09:59:28 -0500 Received: from mail-ot1-f53.google.com (mail-ot1-f53.google.com [209.85.210.53]) (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 768D7216C4; Tue, 10 Nov 2020 14:59:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605020367; bh=qvUn9qNX1M1Qx2QeznJUHEO4kgcTe0+DelhXJxEE0dw=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=O/3QTe6UPGl4+UBnrvNNeMglzQW4NaG0atUAknJXGKmiKlQ3jFAg466x/NwQrKu8/ gBOWhF2e4nqsUJikfZBNK85TbHjpqqfBqGUI/fPV3Q4vo0VU27Kg9mYaa1UZ+CPmR7 m6tDvxeghc9snLMuu1GE+vc1t3kZ5zdJ+r04K2GU= Received: by mail-ot1-f53.google.com with SMTP id f16so12745658otl.11; Tue, 10 Nov 2020 06:59:27 -0800 (PST) X-Gm-Message-State: AOAM530/6H67dDL5PAJL3KAeHijbr+1XU2zLAQyWMFDyoERLp8rObvxD Spis/dV5AB9DWng0pGXDXiFUAN1Kt1LNhA2hImg= X-Google-Smtp-Source: ABdhPJxoTX+rWXC9j2qbuOi17pSMpsm+frJ8yNOwZPIBGWBUEPxRNPsSN2Sgb5QTmR2TPMukZYJ0UGj/XW9Ewao913I= X-Received: by 2002:a9d:23a6:: with SMTP id t35mr13613677otb.210.1605020366593; Tue, 10 Nov 2020 06:59:26 -0800 (PST) MIME-Version: 1.0 References: <20200930153519.7282-16-kishon@ti.com> <30c8f7a1-baa5-1eb4-d2c2-9a13be896f0f@ti.com> In-Reply-To: <30c8f7a1-baa5-1eb4-d2c2-9a13be896f0f@ti.com> From: Arnd Bergmann Date: Tue, 10 Nov 2020 15:59:08 +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-pci@vger.kernel.org On Tue, Nov 10, 2020 at 3:20 PM Kishon Vijay Abraham I wrote: > On 10/11/20 7:55 am, Sherry Sun wrote: > > But for VOP, only two boards are needed(one board as host and one board as card) to realize the > > communication between the two systems, so my question is what are the advantages of using NTB? > > NTB is a bridge that facilitates communication between two different > systems. So it by itself will not be source or sink of any data unlike a > normal EP to RP system (or the VOP) which will be source or sink of data. > > > Because I think the architecture of NTB seems more complicated. Many thanks! > > yeah, I think it enables a different use case all together. Consider you > have two x86 HOST PCs (having RP) and they have to be communicate using > PCIe. NTB can be used in such cases for the two x86 PCs to communicate > with each other over PCIe, which wouldn't be possible without NTB. I think for VOP, we should have an abstraction that can work on either NTB or directly on the endpoint framework but provide an interface that then lets you create logical devices the same way. Doing VOP based on NTB plus the new NTB_EPF driver would also work and just move the abstraction somewhere else, but I guess it would complicate setting it up for those users that only care about the simpler endpoint case. Arnd