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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 EEA5FC07E95 for ; Tue, 20 Jul 2021 15:48:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C740061164 for ; Tue, 20 Jul 2021 15:48:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238458AbhGTPHt (ORCPT ); Tue, 20 Jul 2021 11:07:49 -0400 Received: from mail-pf1-f171.google.com ([209.85.210.171]:35341 "EHLO mail-pf1-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240016AbhGTOgO (ORCPT ); Tue, 20 Jul 2021 10:36:14 -0400 Received: by mail-pf1-f171.google.com with SMTP id d12so19855359pfj.2; Tue, 20 Jul 2021 08:15:33 -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=FxHKIA6d476YSwGem4oYqSqtuJwfzxZyIwIAv3Y/bLc=; b=cNWLJLJguton8860X+8Yfy8TPhGNLPdE+Ur2H/KNUTa0G/4TOgtQE5adQ9T1jxiONA O+/XAiOGuUCWqPcFXr330V8B8BXsnEui5hFfPId9sRkCYBt1ng+u7ccIlvrky4nf83Ot z/U32vnwus+Vb8Gh7SOoKPiLLD4kPxqF/eRkMNFyK0QMe7MAEWCAyG1wP6MnKz5g6+dd qD6CW8XO1dGtTT2v3E+O685Xx04rvZjeXTaP9e2JYTqX20HaBEpcrO2L4l8Y+3Kr2JjW 5YyjDYPo4gMI1OFq+XRFHuy8G+3NHx7SiBg7oY/mwZP4rpBBK75FdJNaafH5KQh80BwJ PGJA== X-Gm-Message-State: AOAM533h/TRUindxCnjylgoLD32VB01eWWfnLznrfyx/Y2ShXQAjJhAB Hko/w99dJxZcJCeO3MzsiMQ= X-Google-Smtp-Source: ABdhPJy9ELkMjd5dPxR/F99Bfm30AEv+7kHZdDzhtxub0LmnQYuoV9ZE9dN82yJxawaDDQZBuJfcsA== X-Received: by 2002:a63:3dcb:: with SMTP id k194mr31004732pga.202.1626794133080; Tue, 20 Jul 2021 08:15:33 -0700 (PDT) Received: from ?IPv6:2601:647:4000:d7:9fa9:39d2:8b59:76ce? ([2601:647:4000:d7:9fa9:39d2:8b59:76ce]) by smtp.gmail.com with ESMTPSA id n12sm25307625pgr.2.2021.07.20.08.15.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 20 Jul 2021 08:15:32 -0700 (PDT) Subject: Re: [Patch v4 0/3] Introduce a driver to support host accelerated access to Microsoft Azure Blob To: Long Li , Christoph Hellwig Cc: "longli@linuxonhyperv.com" , "linux-fs@vger.kernel.org" , "linux-block@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-hyperv@vger.kernel.org" , "gregkh@linuxfoundation.org" References: <1626751866-15765-1-git-send-email-longli@linuxonhyperv.com> <82e8bec6-4f6f-08d7-90db-9661f675749d@acm.org> From: Bart Van Assche Message-ID: <115d864c-46c2-2bc8-c392-fd63d34c9ed0@acm.org> Date: Tue, 20 Jul 2021 08:15:30 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 7/20/21 12:05 AM, Long Li wrote: >> Subject: Re: [Patch v4 0/3] Introduce a driver to support host accelerated >> access to Microsoft Azure Blob >> >> On Mon, Jul 19, 2021 at 09:37:56PM -0700, Bart Van Assche wrote: >>> such that this object storage driver can be implemented as a >>> user-space library instead of as a kernel driver? As you may know vfio >>> users can either use eventfds for completion notifications or polling. >>> An interface like io_uring can be built easily on top of vfio. >> >> Yes. Similar to say the NVMe K/V command set this does not look like a >> candidate for a kernel driver. > > The driver is modeled to support multiple processes/users over a VMBUS > channel. I don't see a way that this can be implemented through VFIO? > > Even if it can be done, this exposes a security risk as the same VMBUS > channel is shared by multiple processes in user-mode. Sharing a VMBUS channel among processes is not necessary. I propose to assign one VMBUS channel to each process and to multiplex I/O submitted to channels associated with the same blob storage object inside e.g. the hypervisor. This is not a new idea. In the NVMe specification there is a diagram that shows that multiple NVMe controllers can provide access to the same NVMe namespace. See also diagram "Figure 416: NVM Subsystem with Three I/O Controllers" in version 1.4 of the NVMe specification. Bart.