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From: Maxime Coquelin <maxime.coquelin@redhat.com>
To: Shahaf Shuler <shahafs@mellanox.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: Tue, 10 Sep 2019 09:46:26 +0200
Message-ID: <e32aa43e-d90e-1cf0-d3ca-4f6d1a281fcd@redhat.com> (raw)
In-Reply-To: <AM0PR0502MB3795700E1F290A6107AE840DC3B70@AM0PR0502MB3795.eurprd05.prod.outlook.com>

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.

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.

> Is nested virtualization is what you have in mind?

For the para-virtualized virtio device, either nested virtualization,
or container running within the guest.

Maxime

  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 [this message]
2019-09-10 13:44     ` Shahaf Shuler
2019-09-10 13:56       ` Maxime Coquelin
2019-09-11  5:15         ` Shahaf Shuler
2019-09-11  7:15           ` Maxime Coquelin
2019-10-24  6:32 ` [dpdk-stable] " Maxime Coquelin

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