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=unavailable 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 C071DC04A6B for ; Wed, 8 May 2019 12:39:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9CC1E20989 for ; Wed, 8 May 2019 12:39:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728607AbfEHMjW (ORCPT ); Wed, 8 May 2019 08:39:22 -0400 Received: from mail-wr1-f67.google.com ([209.85.221.67]:44049 "EHLO mail-wr1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726515AbfEHMjV (ORCPT ); Wed, 8 May 2019 08:39:21 -0400 Received: by mail-wr1-f67.google.com with SMTP id c5so1774031wrs.11 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=W9Z4LWnY4a1ElppfrNA4VALiFVMisNlfo39aDauSiw2ZXu1wCWDQPW3MsW8lP0FScV gA8bysTbAfXpc5jzI+gY72k2dhVy1xSImqi5cMxQCZqqpvLW3uGoqAAAMQNYoSOv2r+o qWBl28HEfK1BSX5eRwUIkRb71OMFH8Fs4E30z8V0Fg4KNV5RtHTPGSgkp7hDnnQsnfY7 NZWsluhS10DRRhgWf9Af60ZtOV2idP/mHtXJRc86kkMCXDWpdV+pslKwq8CbTqx9uhZs zlj6lBH+dARhFi3DTZAUmX+Oqajy0EBJEfut3HB4oAHa0hQ8BeP8cm7UBctYM9hvBo5c 3fHg== X-Gm-Message-State: APjAAAXF+l1phXfw4yF316KxWkT6Sv+40tuaZ8N0KEspZkaP3eW4+Ze5 9rKbjkjEdafpcbQUQHo64/d2nA== 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: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@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