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=-2.3 required=3.0 tests=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 5D2F1C7618B for ; Mon, 29 Jul 2019 16:15:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 34E402067D for ; Mon, 29 Jul 2019 16:15:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727036AbfG2QPJ (ORCPT ); Mon, 29 Jul 2019 12:15:09 -0400 Received: from mail-pg1-f193.google.com ([209.85.215.193]:44212 "EHLO mail-pg1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726190AbfG2QPJ (ORCPT ); Mon, 29 Jul 2019 12:15:09 -0400 Received: by mail-pg1-f193.google.com with SMTP id i18so28499042pgl.11; Mon, 29 Jul 2019 09:15:08 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=2/uoNs6vHyO3yeTHZpt1irIA1A/s4WXB9GVkMSlWRRE=; b=h58UnGsdoWIrRoq/ZAAp4VoChpO8eIQk9rqeN8VPi42Fd7QkGPpt/VMHw02eMUiwLv yGPFQ6YZkPFFYZbwRRIsjLyI1AZ7aypNV4E6QzzWNSBT6qb7OjVI0tw3i1dvA1Pd0d1k NKnRzHu0va81fzsXhTbKWQWAKKKXEOHFxNTUoLM9NvzpQegQThYFJWmX6FgZyIUEfIXV +G7H8nUE3uCsAruKc/B+j2xVloXlQ1wVjQFf6dkP2w3orXZ3R31O1f6HhYpzjsXKhawP uymJyvnxMIbaGAsQtnIyXfuhAq95EVVFrncF/cTkIntk6IjDasN4x/kXlHjzS4H5n2sq 5t2g== X-Gm-Message-State: APjAAAXHgg5rIvziXlalP272ld/DoNXBLf3auPA45esoY55hHTIEYpgN DMsiN6rkEP9isa9VSYwna6EuR6yI X-Google-Smtp-Source: APXvYqxvmRfMLtWjctTI+NBPENOugc0Re1KJKbTr0Q9VzZj2iX3jBmqvW9TdNQgLxS05uGk+p9MGBQ== X-Received: by 2002:a17:90a:8985:: with SMTP id v5mr111210220pjn.136.1564416908477; Mon, 29 Jul 2019 09:15:08 -0700 (PDT) Received: from ?IPv6:2601:647:4800:973f:68b1:d8a0:b9e3:285e? ([2601:647:4800:973f:68b1:d8a0:b9e3:285e]) by smtp.gmail.com with ESMTPSA id b36sm93895852pjc.16.2019.07.29.09.15.06 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 29 Jul 2019 09:15:07 -0700 (PDT) Subject: Re: [PATCH v6 00/16] nvmet: add target passthru commands support To: Stephen Bates , Logan Gunthorpe , Hannes Reinecke , "linux-kernel@vger.kernel.org" , "linux-nvme@lists.infradead.org" , "linux-block@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" Cc: Christoph Hellwig , Keith Busch , Jens Axboe , Chaitanya Kulkarni , Max Gurtovoy References: <20190725172335.6825-1-logang@deltatee.com> <1f202de3-1122-f4a3-debd-0d169f545047@suse.de> <8fd8813f-f8e1-2139-13bf-b0635a03bc30@deltatee.com> <175fa142-4815-ee48-82a4-18eb411db1ae@grimberg.me> <76f617b9-1137-48b6-f10d-bfb1be2301df@deltatee.com> <1260e01c-6731-52f7-ae83-0b90e0345c68@deltatee.com> <6DF00EEF-5A9D-49C9-A27C-BE34E594D9A9@raithlin.com> From: Sagi Grimberg Message-ID: <322df1b1-dbba-2018-44da-c108336f8d55@grimberg.me> Date: Mon, 29 Jul 2019 09:15:06 -0700 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: <6DF00EEF-5A9D-49C9-A27C-BE34E594D9A9@raithlin.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org >> This is different from multipath on say a multi-controller PCI device >> and trying to expose both those controllers through passthru. this is >> where the problems we are discussing come up. > > I *think* there is some confusion. I *think* Sagi is talking about network multi-path (i.e. the ability for the host to connect to a controller on the target via two different network paths that fail-over as needed). I *think* Logan is talking about multi-port PCIe NVMe devices that allow namespaces to be accessed via more than one controller over PCIe (dual-port NVMe SSDs being the most obvious example of this today). Yes, I was referring to fabrics multipathing which is somewhat orthogonal to the backend pci multipathing (unless I'm missing something). >> But it's the multipath through different ports that >> seems important for fabrics. ie. If I have a host with a path through >> RDMA and a path through TCP they should both work and allow fail over. > > Yes, or even two paths that are both RDMA or both TCP but which take a different path through the network from host to target. > >> Our real-world use case is to support our PCI device which has a bunch >> of vendor unique commands and isn't likely to support multiple >> controllers in the foreseeable future. > > I think solving passthru for single-port PCIe controllers would be a good start. Me too.