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 5B604C0650E for ; Thu, 4 Jul 2019 07:04:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 33BC52133F for ; Thu, 4 Jul 2019 07:04:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727232AbfGDHEJ (ORCPT ); Thu, 4 Jul 2019 03:04:09 -0400 Received: from mga07.intel.com ([134.134.136.100]:57426 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725920AbfGDHEJ (ORCPT ); Thu, 4 Jul 2019 03:04:09 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 04 Jul 2019 00:04:08 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.63,449,1557212400"; d="scan'208";a="339529062" Received: from npg-dpdk-virtio-tbie-2.sh.intel.com (HELO ___) ([10.67.104.151]) by orsmga005.jf.intel.com with ESMTP; 04 Jul 2019 00:04:06 -0700 Date: Thu, 4 Jul 2019 15:02:42 +0800 From: Tiwei Bie To: Jason Wang 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 Subject: Re: [RFC v2] vhost: introduce mdev based hardware vhost backend Message-ID: <20190704070242.GA27369@___> 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@___> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Thu, Jul 04, 2019 at 02:35:20PM +0800, Jason Wang wrote: > 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 :) Thanks! > > > > 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? Yeah, exactly. If we go for vhost_mdev, we may have some vhost nodes in /dev similar to what /dev/vfio/* does to handle the $UUID and open the device (e.g. similar to VFIO_GROUP_GET_DEVICE_FD in VFIO). And to setup the device, we can try to reuse the ioctls of the existing kernel vhost as much as possible. Thanks, Tiwei > > Thanks > > > > > > Thanks, > > Tiwei > > > Thanks > > >