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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 E665AC0650E for ; Thu, 4 Jul 2019 06:35:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C9ECB21850 for ; Thu, 4 Jul 2019 06:35:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727378AbfGDGfk (ORCPT ); Thu, 4 Jul 2019 02:35:40 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46426 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725945AbfGDGfk (ORCPT ); Thu, 4 Jul 2019 02:35:40 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 83BE830917AC; Thu, 4 Jul 2019 06:35:37 +0000 (UTC) Received: from [10.72.12.202] (ovpn-12-202.pek2.redhat.com [10.72.12.202]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4247B17CCB; Thu, 4 Jul 2019 06:35:22 +0000 (UTC) Subject: Re: [RFC v2] vhost: introduce mdev based hardware vhost backend To: Tiwei Bie Cc: mst@redhat.com, alex.williamson@redhat.com, maxime.coquelin@redhat.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, dan.daly@intel.com, cunming.liang@intel.com, zhihong.wang@intel.com References: <20190703091339.1847-1-tiwei.bie@intel.com> <7b8279b2-aa7e-7adc-eeff-20dfaf4400d0@redhat.com> <20190703115245.GA22374@___> <64833f91-02cd-7143-f12e-56ab93b2418d@redhat.com> <20190703130817.GA1978@___> <20190704062134.GA21116@___> From: Jason Wang Message-ID: Date: Thu, 4 Jul 2019 14:35:20 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20190704062134.GA21116@___> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.41]); Thu, 04 Jul 2019 06:35:39 +0000 (UTC) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 2019/7/4 下午2:21, Tiwei Bie wrote: > On Thu, Jul 04, 2019 at 12:31:48PM +0800, Jason Wang wrote: >> On 2019/7/3 下午9:08, Tiwei Bie wrote: >>> On Wed, Jul 03, 2019 at 08:16:23PM +0800, Jason Wang wrote: >>>> On 2019/7/3 下午7:52, Tiwei Bie wrote: >>>>> On Wed, Jul 03, 2019 at 06:09:51PM +0800, Jason Wang wrote: >>>>>> On 2019/7/3 下午5:13, Tiwei Bie wrote: >>>>>>> Details about this can be found here: >>>>>>> >>>>>>> https://lwn.net/Articles/750770/ >>>>>>> >>>>>>> What's new in this version >>>>>>> ========================== >>>>>>> >>>>>>> A new VFIO device type is introduced - vfio-vhost. This addressed >>>>>>> some comments from here:https://patchwork.ozlabs.org/cover/984763/ >>>>>>> >>>>>>> Below is the updated device interface: >>>>>>> >>>>>>> Currently, there are two regions of this device: 1) CONFIG_REGION >>>>>>> (VFIO_VHOST_CONFIG_REGION_INDEX), which can be used to setup the >>>>>>> device; 2) NOTIFY_REGION (VFIO_VHOST_NOTIFY_REGION_INDEX), which >>>>>>> can be used to notify the device. >>>>>>> >>>>>>> 1. CONFIG_REGION >>>>>>> >>>>>>> The region described by CONFIG_REGION is the main control interface. >>>>>>> Messages will be written to or read from this region. >>>>>>> >>>>>>> The message type is determined by the `request` field in message >>>>>>> header. The message size is encoded in the message header too. >>>>>>> The message format looks like this: >>>>>>> >>>>>>> struct vhost_vfio_op { >>>>>>> __u64 request; >>>>>>> __u32 flags; >>>>>>> /* Flag values: */ >>>>>>> #define VHOST_VFIO_NEED_REPLY 0x1 /* Whether need reply */ >>>>>>> __u32 size; >>>>>>> union { >>>>>>> __u64 u64; >>>>>>> struct vhost_vring_state state; >>>>>>> struct vhost_vring_addr addr; >>>>>>> } payload; >>>>>>> }; >>>>>>> >>>>>>> The existing vhost-kernel ioctl cmds are reused as the message >>>>>>> requests in above structure. >>>>>> Still a comments like V1. What's the advantage of inventing a new protocol? >>>>> I'm trying to make it work in VFIO's way.. >>>>> >>>>>> I believe either of the following should be better: >>>>>> >>>>>> - using vhost ioctl,  we can start from SET_VRING_KICK/SET_VRING_CALL and >>>>>> extend it with e.g notify region. The advantages is that all exist userspace >>>>>> program could be reused without modification (or minimal modification). And >>>>>> vhost API hides lots of details that is not necessary to be understood by >>>>>> application (e.g in the case of container). >>>>> Do you mean reusing vhost's ioctl on VFIO device fd directly, >>>>> or introducing another mdev driver (i.e. vhost_mdev instead of >>>>> using the existing vfio_mdev) for mdev device? >>>> Can we simply add them into ioctl of mdev_parent_ops? >>> Right, either way, these ioctls have to be and just need to be >>> added in the ioctl of the mdev_parent_ops. But another thing we >>> also need to consider is that which file descriptor the userspace >>> will do the ioctl() on. So I'm wondering do you mean let the >>> userspace do the ioctl() on the VFIO device fd of the mdev >>> device? >>> >> Yes. > Got it! I'm not sure what's Alex opinion on this. If we all > agree with this, I can do it in this way. > >> Is there any other way btw? > Just a quick thought.. Maybe totally a bad idea. It's not for sure :) > I was thinking > whether it would be odd to do non-VFIO's ioctls on VFIO's device > fd. So I was wondering whether it's possible to allow binding > another mdev driver (e.g. vhost_mdev) to the supported mdev > devices. The new mdev driver, vhost_mdev, can provide similar > ways to let userspace open the mdev device and do the vhost ioctls > on it. To distinguish with the vfio_mdev compatible mdev devices, > the device API of the new vhost_mdev compatible mdev devices > might be e.g. "vhost-net" for net? > > So in VFIO case, the device will be for passthru directly. And > in VHOST case, the device can be used to accelerate the existing > virtualized devices. > > How do you think? If my understanding is correct, there will be no VFIO ioctl if we go for vhost_mdev? Thanks > > Thanks, > Tiwei >> Thanks >>