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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 CCBCDC4360C for ; Sun, 29 Sep 2019 07:39:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A44B621882 for ; Sun, 29 Sep 2019 07:39:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728900AbfI2HjV (ORCPT ); Sun, 29 Sep 2019 03:39:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57164 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725906AbfI2HjV (ORCPT ); Sun, 29 Sep 2019 03:39:21 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 812D485360; Sun, 29 Sep 2019 07:39:20 +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 3F877600D1; Sun, 29 Sep 2019 07:39:06 +0000 (UTC) Subject: Re: [PATCH] vhost: introduce mdev based hardware backend To: "Michael S. Tsirkin" Cc: Tiwei Bie , 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, lingshan.zhu@intel.com References: <20190926045427.4973-1-tiwei.bie@intel.com> <20190926042156-mutt-send-email-mst@kernel.org> <20190926131439.GA11652@___> <8ab5a8d9-284d-bba5-803d-08523c0814e1@redhat.com> <20190927053935-mutt-send-email-mst@kernel.org> <20190927084408-mutt-send-email-mst@kernel.org> <20190927092219-mutt-send-email-mst@kernel.org> From: Jason Wang Message-ID: <1aba781c-d776-422d-2629-86b11990a9b5@redhat.com> Date: Sun, 29 Sep 2019 15:39:05 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190927092219-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Sun, 29 Sep 2019 07:39:20 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019/9/27 下午9:23, Michael S. Tsirkin wrote: > On Fri, Sep 27, 2019 at 09:17:56PM +0800, Jason Wang wrote: >> On 2019/9/27 下午8:46, Michael S. Tsirkin wrote: >>> On Fri, Sep 27, 2019 at 08:17:47PM +0800, Jason Wang wrote: >>>> On 2019/9/27 下午5:41, Michael S. Tsirkin wrote: >>>>> On Fri, Sep 27, 2019 at 11:27:12AM +0800, Jason Wang wrote: >>>>>> On 2019/9/26 下午9:14, Tiwei Bie wrote: >>>>>>> On Thu, Sep 26, 2019 at 04:35:18AM -0400, Michael S. Tsirkin wrote: >>>>>>>> On Thu, Sep 26, 2019 at 12:54:27PM +0800, Tiwei Bie wrote: >>>>>>> [...] >>>>>>>>> diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h >>>>>>>>> index 40d028eed645..5afbc2f08fa3 100644 >>>>>>>>> --- a/include/uapi/linux/vhost.h >>>>>>>>> +++ b/include/uapi/linux/vhost.h >>>>>>>>> @@ -116,4 +116,12 @@ >>>>>>>>> #define VHOST_VSOCK_SET_GUEST_CID _IOW(VHOST_VIRTIO, 0x60, __u64) >>>>>>>>> #define VHOST_VSOCK_SET_RUNNING _IOW(VHOST_VIRTIO, 0x61, int) >>>>>>>>> +/* VHOST_MDEV specific defines */ >>>>>>>>> + >>>>>>>>> +#define VHOST_MDEV_SET_STATE _IOW(VHOST_VIRTIO, 0x70, __u64) >>>>>>>>> + >>>>>>>>> +#define VHOST_MDEV_S_STOPPED 0 >>>>>>>>> +#define VHOST_MDEV_S_RUNNING 1 >>>>>>>>> +#define VHOST_MDEV_S_MAX 2 >>>>>>>>> + >>>>>>>>> #endif >>>>>>>> So assuming we have an underlying device that behaves like virtio: >>>>>>> I think they are really good questions/suggestions. Thanks! >>>>>>> >>>>>>>> 1. Should we use SET_STATUS maybe? >>>>>>> I like this idea. I will give it a try. >>>>>>> >>>>>>>> 2. Do we want a reset ioctl? >>>>>>> I think it is helpful. If we use SET_STATUS, maybe we >>>>>>> can use it to support the reset. >>>>>>> >>>>>>>> 3. Do we want ability to enable rings individually? >>>>>>> I will make it possible at least in the vhost layer. >>>>>> Note the API support e.g set_vq_ready(). >>>>> virtio spec calls this "enabled" so let's stick to that. >>>> Ok. >>>> >>>> >>>>>>>> 4. Does device need to limit max ring size? >>>>>>>> 5. Does device need to limit max number of queues? >>>>>>> I think so. It's helpful to have ioctls to report the max >>>>>>> ring size and max number of queues. >>>>>> An issue is the max number of queues is done through a device specific way, >>>>>> usually device configuration space. This is supported by the transport API, >>>>>> but how to expose it to userspace may need more thought. >>>>>> >>>>>> Thanks >>>>> an ioctl for device config? But for v1 I'd be quite happy to just have >>>>> a minimal working device with 2 queues. >>>> I'm fully agree, and it will work as long as VIRTIO_NET_F_MQ and >>>> VIRTIO_NET_F_CTRL_VQ is not advertised by the mdev device. >>>> >>>> Thanks >>> Hmm this means we need to validate the features bits, >>> not just pass them through to the hardware. >>> Problem is, how do we add more feature bits later, >>> without testing all hardware? >>> I guess this means the device specific driver must do it. >>> >> That looks not good, maybe a virtio device id based features blacklist in >> vhost-mdev. Then MQ and CTRL_VQ could be filtered out by vhost-mdev. >> >> Thanks > Two implementations of e.g. virtio net can have different > features whitelisted. I meant for kernel driver, we won't blacklist any feature, but for vhost-mdev, we need to do that. > So I think there's no way but let > the driver do it. We should probably provide a standard place > in the ops for driver to supply the whitelist, to make sure > drivers don't forget. For 'driver' do you mean userspace driver of  the mdev device? Thanks >