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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 C69E4CA9EAE for ; Wed, 30 Oct 2019 01:26:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9ECB12086A for ; Wed, 30 Oct 2019 01:26:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726853AbfJ3B0k (ORCPT ); Tue, 29 Oct 2019 21:26:40 -0400 Received: from mga06.intel.com ([134.134.136.31]:60961 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726108AbfJ3B0k (ORCPT ); Tue, 29 Oct 2019 21:26:40 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 29 Oct 2019 18:26:39 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.68,245,1569308400"; d="scan'208";a="203039462" Received: from dpdk-virtio-tbie-2.sh.intel.com (HELO ___) ([10.67.104.74]) by orsmga003.jf.intel.com with ESMTP; 29 Oct 2019 18:26:36 -0700 Date: Wed, 30 Oct 2019 09:27:28 +0800 From: Tiwei Bie To: Jason Wang Cc: "Michael S. Tsirkin" , 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 Subject: Re: [PATCH v2] vhost: introduce mdev based hardware backend Message-ID: <20191030012728.GA29333@___> References: <20191024091839.GA17463@___> <20191025080143-mutt-send-email-mst@kernel.org> <20191028015842.GA9005@___> <5e8a623d-9d91-607a-1f9e-7a7086ba9a68@redhat.com> <20191029095738.GA7228@___> <146752f4-174c-c916-3682-b965b96d7872@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <146752f4-174c-c916-3682-b965b96d7872@redhat.com> 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 Tue, Oct 29, 2019 at 06:48:27PM +0800, Jason Wang wrote: > On 2019/10/29 下午5:57, Tiwei Bie wrote: > > On Mon, Oct 28, 2019 at 11:50:49AM +0800, Jason Wang wrote: > >> On 2019/10/28 上午9:58, Tiwei Bie wrote: > >>> On Fri, Oct 25, 2019 at 08:16:26AM -0400, Michael S. Tsirkin wrote: > >>>> On Fri, Oct 25, 2019 at 05:54:55PM +0800, Jason Wang wrote: > >>>>> On 2019/10/24 下午6:42, Jason Wang wrote: > >>>>>> Yes. > >>>>>> > >>>>>> > >>>>>>>   And we should try to avoid > >>>>>>> putting ctrl vq and Rx/Tx vqs in the same DMA space to prevent > >>>>>>> guests having the chance to bypass the host (e.g. QEMU) to > >>>>>>> setup the backend accelerator directly. > >>>>>> That's really good point.  So when "vhost" type is created, parent > >>>>>> should assume addr of ctrl_vq is hva. > >>>>>> > >>>>>> Thanks > >>>>> This works for vhost but not virtio since there's no way for virtio kernel > >>>>> driver to differ ctrl_vq with the rest when doing DMA map. One possible > >>>>> solution is to provide DMA domain isolation between virtqueues. Then ctrl vq > >>>>> can use its dedicated DMA domain for the work. > >>> It might not be a bad idea to let the parent drivers distinguish > >>> between virtio-mdev mdevs and vhost-mdev mdevs in ctrl-vq handling > >>> by mdev's class id. > >> Yes, that should work, I have something probable better, see below. > >> > >> > >>>>> Anyway, this could be done in the future. We can have a version first that > >>>>> doesn't support ctrl_vq. > >>> +1, thanks > >>> > >>>>> Thanks > >>>> Well no ctrl_vq implies either no offloads, or no XDP (since XDP needs > >>>> to disable offloads dynamically). > >>>> > >>>> if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS) > >>>> && (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO4) || > >>>> virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO6) || > >>>> virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_ECN) || > >>>> virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_UFO) || > >>>> virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM))) { > >>>> NL_SET_ERR_MSG_MOD(extack, "Can't set XDP while host is implementing LRO/CSUM, disable LRO/CSUM first"); > >>>> return -EOPNOTSUPP; > >>>> } > >>>> > >>>> neither is very attractive. > >>>> > >>>> So yes ok just for development but we do need to figure out how it will > >>>> work down the road in production. > >>> Totally agree. > >>> > >>>> So really this specific virtio net device does not support control vq, > >>>> instead it supports a different transport specific way to send commands > >>>> to device. > >>>> > >>>> Some kind of extension to the transport? Ideas? > >> So it's basically an issue of isolating DMA domains. Maybe we can start with > >> transport API for querying per vq DMA domain/ASID? > >> > >> - for vhost-mdev, userspace can query the DMA domain for each specific > >> virtqueue. For control vq, mdev can return id for software domain, for the > >> rest mdev will return id of VFIO domain. Then userspace know that it should > >> use different API for preparing the virtqueue, e.g for vq other than control > >> vq, it should use VFIO DMA API. The control vq it should use hva instead. > >> > >> - for virito-mdev, we can introduce per-vq DMA device, and route DMA mapping > >> request for control vq back to mdev instead of the hardware. (We can wrap > >> them into library or helpers to ease the development of vendor physical > >> drivers). > > Thanks for this proposal! I'm thinking about it these days. > > I think it might be too complicated. I'm wondering whether we > > can have something simpler. I will post a RFC patch to show > > my idea today. > > > Thanks, will check. > > Btw, for virtio-mdev, the change should be very minimal, will post an > RFC as well. For vhost-mdev, it could be just a helper to return an ID > for DMA domain like ID_VFIO or ID_HVA. > > Or a more straightforward way is to force queues like control vq to use PA. Will check. Thanks! > > > > > > Thanks, > > Tiwei > > >