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From: Shahaf Shuler <shahafs@mellanox.com>
To: Maxime Coquelin <maxime.coquelin@redhat.com>,
	"tiwei.bie@intel.com" <tiwei.bie@intel.com>,
	"zhihong.wang@intel.com" <zhihong.wang@intel.com>,
	"amorenoz@redhat.com" <amorenoz@redhat.com>,
	"xiao.w.wang@intel.com" <xiao.w.wang@intel.com>,
	"dev@dpdk.org" <dev@dpdk.org>,
	"jfreimann@redhat.com" <jfreimann@redhat.com>
Cc: "stable@dpdk.org" <stable@dpdk.org>, Matan Azrad <matan@mellanox.com>
Subject: Re: [dpdk-stable] [dpdk-dev] [PATCH 00/15] Introduce Virtio vDPA driver
Date: Wed, 11 Sep 2019 05:15:46 +0000
Message-ID: <AM0PR0502MB379542B09EC7252A2BEC096DC3B10@AM0PR0502MB3795.eurprd05.prod.outlook.com> (raw)
In-Reply-To: <9edf9ca8-6ecf-ff24-2db6-311c00e678ce@redhat.com>

Tuesday, September 10, 2019 4:56 PM, Maxime Coquelin:
> Subject: Re: [dpdk-dev] [PATCH 00/15] Introduce Virtio vDPA driver
> 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,
> >>
> >>
> >> 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).

Thanks Maxim, It is clearer now. 
From what I understand this driver is to be used w/ vDPA when the underlying device is virtio. 

I can perfectly understand the para-virt ( + nested virtualization / container inside VM) use case. 

Regarding the fully emulated virtio device on the host (instead of a plain VF) - for me the benefit still not clear - if you have HW that can expose VF why not use VF + vendor specific vDPA driver.

Anyway - for the series,
Acked-by: Shahaf Shuler <shahafs@mellanox.com>


  reply index

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-29  7:59 [dpdk-stable] " Maxime Coquelin
2019-08-29  7:59 ` [dpdk-stable] [PATCH 01/15] vhost: remove vhost kernel header inclusion Maxime Coquelin
2019-09-02  6:03   ` Tiwei Bie
2019-09-03  7:24     ` Maxime Coquelin
2019-08-29  7:59 ` [dpdk-stable] [PATCH 02/15] vhost: configure vDPA as soon as the device is ready Maxime Coquelin
2019-09-02  8:34   ` Ye Xiaolong
2019-09-02  9:02     ` Wang, Xiao W
2019-09-03  7:34       ` Maxime Coquelin
2019-09-03 10:58         ` Wang, Xiao W
2019-08-29  7:59 ` [dpdk-stable] [PATCH 03/15] net/virtio: move control path fonctions in virtqueue file Maxime Coquelin
2019-09-02  6:05   ` Tiwei Bie
2019-08-29  7:59 ` [dpdk-stable] [PATCH 04/15] net/virtio: add virtio PCI subsystem device ID declaration Maxime Coquelin
2019-09-02  6:14   ` Tiwei Bie
2019-09-03  7:25     ` Maxime Coquelin
2019-08-29  7:59 ` [dpdk-stable] [PATCH 05/15] net/virtio: save notify bar ID in virtio HW struct Maxime Coquelin
2019-09-02  6:17   ` Tiwei Bie
2019-08-29  7:59 ` [dpdk-stable] [PATCH 06/15] net/virtio: add skeleton for virtio vDPA driver Maxime Coquelin
2019-09-02  6:27   ` Tiwei Bie
2019-09-03  7:25     ` Maxime Coquelin
2019-08-29  7:59 ` [dpdk-stable] [PATCH 07/15] net/virtio: add vDPA ops to get number of queue Maxime Coquelin
2019-09-02  6:32   ` Tiwei Bie
2019-08-29  7:59 ` [dpdk-stable] [PATCH 08/15] net/virtio: add virtio vDPA op to get features Maxime Coquelin
2019-09-02  6:43   ` Tiwei Bie
2019-09-03  7:27     ` Maxime Coquelin
2019-08-29  7:59 ` [dpdk-stable] [PATCH 09/15] net/virtio: add virtio vDPA op to get protocol features Maxime Coquelin
2019-09-02  6:46   ` Tiwei Bie
2019-08-29  7:59 ` [dpdk-stable] [PATCH 10/15] net/virtio: add vDPA op to configure and start the device Maxime Coquelin
2019-09-03  5:30   ` Tiwei Bie
2019-09-03  7:40     ` Maxime Coquelin
2019-09-03  8:49       ` Tiwei Bie
2019-09-04  4:06         ` Jason Wang
2019-09-04  6:56           ` Maxime Coquelin
2019-09-05  2:57             ` Tiwei Bie
2019-08-29  7:59 ` [dpdk-stable] [PATCH 11/15] net/virtio: add vDPA op to stop and close " Maxime Coquelin
2019-09-02  7:07   ` Tiwei Bie
2019-09-03  7:30     ` Maxime Coquelin
2019-08-29  7:59 ` [dpdk-stable] [PATCH 12/15] net/virtio: add vDPA op to set features Maxime Coquelin
2019-08-29  7:59 ` [dpdk-stable] [PATCH 13/15] net/virtio: add vDPA ops to get VFIO FDs Maxime Coquelin
2019-09-03  4:47   ` Tiwei Bie
2019-08-29  7:59 ` [dpdk-stable] [PATCH 14/15] net/virtio: add vDPA op to get notification area Maxime Coquelin
2019-09-03  5:02   ` Tiwei Bie
2019-09-03  7:36     ` Maxime Coquelin
2019-09-03  8:40       ` Tiwei Bie
2019-08-29  8:00 ` [dpdk-stable] [PATCH 15/15] doc: add documentation for Virtio vDPA driver Maxime Coquelin
2019-09-09 11:55 ` [dpdk-stable] [dpdk-dev] [PATCH 00/15] Introduce " Shahaf Shuler
2019-09-10  7:46   ` Maxime Coquelin
2019-09-10 13:44     ` Shahaf Shuler
2019-09-10 13:56       ` Maxime Coquelin
2019-09-11  5:15         ` Shahaf Shuler [this message]
2019-09-11  7:15           ` Maxime Coquelin
2019-10-24  6:32 ` [dpdk-stable] " Maxime Coquelin

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