From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: <bruce.richardson@intel.com> Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by dpdk.org (Postfix) with ESMTP id E5A295961 for <dev@dpdk.org>; Mon, 19 Oct 2015 11:46:55 +0200 (CEST) Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga101.fm.intel.com with ESMTP; 19 Oct 2015 02:46:55 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.17,701,1437462000"; d="scan'208";a="796786264" Received: from bricha3-mobl3.ger.corp.intel.com ([10.237.208.63]) by orsmga001.jf.intel.com with SMTP; 19 Oct 2015 02:45:33 -0700 Received: by (sSMTP sendmail emulation); Mon, 19 Oct 2015 10:45:32 +0025 Date: Mon, 19 Oct 2015 10:45:32 +0100 From: Bruce Richardson <bruce.richardson@intel.com> To: "Loftus, Ciara" <ciara.loftus@intel.com> Message-ID: <20151019094532.GB11324@bricha3-MOBL3> References: <1440993326-21205-1-git-send-email-mukawa@igel.co.jp> <1440993326-21205-2-git-send-email-mukawa@igel.co.jp> <20151016125254.GA9980@bricha3-MOBL3> <56244C84.4090309@igel.co.jp> <74F120C019F4A64C9B78E802F6AD4CC24F7A881E@IRSMSX106.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <74F120C019F4A64C9B78E802F6AD4CC24F7A881E@IRSMSX106.ger.corp.intel.com> Organization: Intel Shannon Ltd. User-Agent: Mutt/1.5.23 (2014-03-12) Cc: "dev@dpdk.org" <dev@dpdk.org>, "ann.zhuangyanying@huawei.com" <ann.zhuangyanying@huawei.com> Subject: Re: [dpdk-dev] [RFC PATCH v2] vhost: Add VHOST PMD X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK <dev.dpdk.org> List-Unsubscribe: <http://dpdk.org/ml/options/dev>, <mailto:dev-request@dpdk.org?subject=unsubscribe> List-Archive: <http://dpdk.org/ml/archives/dev/> List-Post: <mailto:dev@dpdk.org> List-Help: <mailto:dev-request@dpdk.org?subject=help> List-Subscribe: <http://dpdk.org/ml/listinfo/dev>, <mailto:dev-request@dpdk.org?subject=subscribe> X-List-Received-Date: Mon, 19 Oct 2015 09:46:56 -0000 On Mon, Oct 19, 2015 at 10:32:50AM +0100, Loftus, Ciara wrote: > > On 2015/10/16 21:52, Bruce Richardson wrote: > > > On Mon, Aug 31, 2015 at 12:55:26PM +0900, Tetsuya Mukawa wrote: > > >> The patch introduces a new PMD. This PMD is implemented as thin > > wrapper > > >> of librte_vhost. It means librte_vhost is also needed to compile the PMD. > > >> The PMD can have 'iface' parameter like below to specify a path to > > connect > > >> to a virtio-net device. > > >> > > >> $ ./testpmd -c f -n 4 --vdev 'eth_vhost0,iface=/tmp/sock0' -- -i > > >> > > >> To connect above testpmd, here is qemu command example. > > >> > > >> $ qemu-system-x86_64 \ > > >> <snip> > > >> -chardev socket,id=chr0,path=/tmp/sock0 \ > > >> -netdev vhost-user,id=net0,chardev=chr0,vhostforce \ > > >> -device virtio-net-pci,netdev=net0 > > >> > > >> Signed-off-by: Tetsuya Mukawa <mukawa@igel.co.jp> > > > With this PMD in place, is there any need to keep the existing vhost library > > > around as a separate entity? Can the existing library be > > subsumed/converted into > > > a standard PMD? > > > > > > /Bruce > > > > Hi Bruce, > > > > I concern about whether the PMD has all features of librte_vhost, > > because librte_vhost provides more features and freedom than ethdev API > > provides. > > In some cases, user needs to choose limited implementation without > > librte_vhost. > > I am going to eliminate such cases while implementing the PMD. > > But I don't have strong belief that we can remove librte_vhost now. > > > > So how about keeping current separation in next DPDK? > > I guess people will try to replace librte_vhost to vhost PMD, because > > apparently using ethdev APIs will be useful in many cases. > > And we will get feedbacks like "vhost PMD needs to support like this usage". > > (Or we will not have feedbacks, but it's also OK.) > > Then, we will be able to merge librte_vhost and vhost PMD. > > I agree with the above. One the concerns I had when reviewing the patch was that the PMD removes some freedom that is available with the library. Eg. Ability to implement the new_device and destroy_device callbacks. If using the PMD you are constrained to the implementations of these in the PMD driver, but if using librte_vhost, you can implement your own with whatever functionality you like - a good example of this can be seen in the vhost sample app. > On the other hand, the PMD is useful in that it removes a lot of complexity for the user and may work for some more general use cases. So I would be in favour of having both options available too. > > Ciara > Thanks. However, just because the libraries are merged does not mean that you need be limited by PMD functionality. Many PMDs provide additional library-specific functions over and above their PMD capabilities. The bonded PMD is a good example here, as it has a whole set of extra functions to create and manipulate bonded devices - things that are obviously not part of the general ethdev API. Other vPMDs similarly include functions to allow them to be created on the fly too. regards, /Bruce