From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dpdk.org (dpdk.org [92.243.14.124]) by inbox.dpdk.org (Postfix) with ESMTP id 7A6ABA2EEB for ; Tue, 10 Sep 2019 15:56:09 +0200 (CEST) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id 585091EF42; Tue, 10 Sep 2019 15:56:09 +0200 (CEST) Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by dpdk.org (Postfix) with ESMTP id AC00F1EF42; Tue, 10 Sep 2019 15:56:07 +0200 (CEST) Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 09F9F309BF1C; Tue, 10 Sep 2019 13:56:07 +0000 (UTC) Received: from [10.36.112.35] (ovpn-112-35.ams2.redhat.com [10.36.112.35]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2F7866092F; Tue, 10 Sep 2019 13:56:02 +0000 (UTC) To: Shahaf Shuler , "tiwei.bie@intel.com" , "zhihong.wang@intel.com" , "amorenoz@redhat.com" , "xiao.w.wang@intel.com" , "dev@dpdk.org" , "jfreimann@redhat.com" Cc: "stable@dpdk.org" , Matan Azrad References: <20190829080000.20806-1-maxime.coquelin@redhat.com> From: Maxime Coquelin Openpgp: preference=signencrypt Autocrypt: addr=maxime.coquelin@redhat.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.45]); Tue, 10 Sep 2019 13:56:07 +0000 (UTC) Subject: Re: [dpdk-stable] [dpdk-dev] [PATCH 00/15] Introduce Virtio vDPA driver X-BeenThere: stable@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches for DPDK stable branches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: stable-bounces@dpdk.org Sender: "stable" On 9/10/19 3:44 PM, Shahaf Shuler wrote: > Tuesday, September 10, 2019 10:46 AM, Maxime Coquelin: >> Subject: Re: [dpdk-dev] [PATCH 00/15] Introduce Virtio vDPA driver >> >> Hi Shahaf, >> >> On 9/9/19 1:55 PM, Shahaf Shuler wrote: >>> Hi Maxime, >>> >>> Thursday, August 29, 2019 11:00 AM, Maxime Coquelin: >>>> Subject: [dpdk-dev] [PATCH 00/15] Introduce Virtio vDPA driver >>>> >>>> vDPA allows to offload Virtio Datapath processing by supported NICs, >>>> like IFCVF for example. >>>> >>>> The control path has to be handled by a dedicated vDPA driver, so >>>> that it can translate Vhost-user protocol requests to proprietary >>>> NICs registers accesses. >>>> >>>> This driver is the vDPA driver for Virtio devices, meaning that >>>> Vhost-user protocol requests get translated to Virtio registers >>>> accesses as per defined in the Virtio spec. >>>> >>>> Basically, it can be used within a guest with a para-virtualized >>>> Virtio-net device, or even with a full Virtio HW offload NIC directly on >> host. >>> >>> Can you elaborate more on the use cases to use such driver? >>> >>> 1. If the underlying HW can support full virtio device, why we need to work >> w/ it w/ vDPA mode? Why not providing it to the VM as passthrough one? >>> 2. why it is preferable to work w/ virtio device as the backend device to be >> used w/ vDPA v.s. working w/ the underlying HW VF? >> >> >> IMHO, I see two uses cases where it can make sense to use vDPA with a full >> offload HW device: >> 1. Live-migration support: It makes it possible to switch to rings >> processing in SW during the migration as Virtio HH does not support >> dirty pages logging. > > Can you elaborate why specifically using virtio_vdpa PMD enables this SW relay during migration? > e.g. the vdpa PMD of intel that runs on top of VF do that today as well. I think there were a misunderstanding. When I said: " I see two uses cases where it can make sense to use vDPA with a full offload HW device " I meant, I see two uses cases where it can make sense to use vDPA with a full offload HW device, instead of the full offload HW device to use Virtio PMD. In other words, I think it is preferable to only offload the datapath, so that it is possible to support SW live-migration. >> >> 2. Can be used to provide a single standard interface (the vhost-user >> socket) to containers in the scope of CNFs. Doing so, the container >> does not need to be modified, whatever the HW NIC: Virtio datapath >> offload only, full Virtio offload, or no offload at all. In the >> latter case, it would not be optimal as it implies forwarding between >> the Vhost PMD and the HW NIC PMD but it would work. > > It is not clear to me the interface map in such system. > From what I understand the container will have virtio-user i/f and the host will have virtio i/f. then the virtio i/f can be programmed to work w/ vDPA or not. > For full emulation I guess you will need to expose the netdev of the fully emulated virtio device to the container? > > Am trying to map when it is beneficial to use this virtio_vdpa PMD and when it is better to use the vendor specific vDPA PMD on top of VF. I think that with above clarification, I made it clear that the goal of this driver is not to replace vendors vDPA drivers (their control path maybe not even be compatible), but instead to provide a generic driver that can be used either within a guest with a para-virtualized Virtio- net device or with HW NIC that fully offloads Virtio (both data and control paths).