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=-0.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 DD97DC04A6B for ; Wed, 8 May 2019 12:39:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B8B1020989 for ; Wed, 8 May 2019 12:39:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728616AbfEHMjX (ORCPT ); Wed, 8 May 2019 08:39:23 -0400 Received: from mail-wr1-f66.google.com ([209.85.221.66]:40093 "EHLO mail-wr1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728599AbfEHMjW (ORCPT ); Wed, 8 May 2019 08:39:22 -0400 Received: by mail-wr1-f66.google.com with SMTP id h4so7749487wre.7 for ; Wed, 08 May 2019 05:39:21 -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=4Rmas8gcFMGufmlR3c5DQmI8ZQrCroMRQQbwgTv6K0o=; b=DVjJI9GLM0wGMGsW8NcrWxaNTRSWQUQT/e2HemxV6gKKszBdt71XgKMcsPAQWygPf7 94aouo1wkHPxev0xOu8X/pZu8Ut268zcYV3wVE7giNpDBw6oajvEj1jFy3jXPzR3Oag7 FNhM5+XhhI/r0lbFR4uf/tzoZ9CjgfvzDCVhKRvVsboM3k1ZQxt/Yzv9y5xbdmJqUuc8 zxVte/v+qKcUESpHMks+PQ4Lp84DWNd95IWbWcvIkTjrTQdpSFA+/TO/ENNYDmflQ3yt 8OKHXbix+B3g4J3NlRhk8OlA7kL23wkG4g0WWFTbYmTMMOyQdpPp0CVTMrQQKkIzdPgY dPWA== X-Gm-Message-State: APjAAAXQMHCz8ygOv26aKQf4Kwskpet0xMhX/PGqKcUfYocxA/arzgQs 9QHuUBGnPqiZmByWnFM0OmuT0w== X-Google-Smtp-Source: APXvYqwuyoFh7G+bUNBJPQbUYqVHJhmvLVup6b4hVfQDP/ku/Jv9N/UUoJIUxNspRHbGoU418ffKdw== X-Received: by 2002:adf:dc8a:: with SMTP id r10mr10988770wrj.15.1557319160335; Wed, 08 May 2019 05:39:20 -0700 (PDT) Received: from [10.201.49.229] (nat-pool-mxp-u.redhat.com. [149.6.153.187]) by smtp.gmail.com with ESMTPSA id a9sm2110131wmm.48.2019.05.08.05.39.16 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 08 May 2019 05:39:19 -0700 (PDT) Subject: Re: [PATCH v2 00/10] RFC: NVME MDEV To: Christoph Hellwig , Maxim Levitsky Cc: Fam Zheng , Keith Busch , Sagi Grimberg , kvm@vger.kernel.org, Wolfram Sang , Greg Kroah-Hartman , Liang Cunming , Nicolas Ferre , linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, "David S . Miller" , Jens Axboe , Alex Williamson , Kirti Wankhede , Mauro Carvalho Chehab , Liu Changpeng , "Paul E . McKenney" , Amnon Ilan , John Ferlan References: <20190502114801.23116-1-mlevitsk@redhat.com> <20190503121838.GA21041@lst.de> <20190506125752.GA5288@lst.de> From: Paolo Bonzini Message-ID: Date: Wed, 8 May 2019 14:39:13 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190506125752.GA5288@lst.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/05/19 07:57, Christoph Hellwig wrote: > > Or to put it into another way: unless your paravirt interface requires > zero specific changes to the core nvme code it is not acceptable at all. I'm not sure it's possible to attain that goal, however I agree that putting the control plane in the kernel is probably not a good idea, so the vhost model is better than mdev for this usecase. In addition, unless it is possible for the driver to pass the queue directly to the guests, there probably isn't much advantage in putting the driver in the kernel at all. Maxim, do you have numbers for 1) QEMU with aio 2) QEMU with VFIO-based userspace nvme driver 3) nvme-mdev? Paolo