Re: [dpdk-dev] [PATCH 00/15] Introduce Virtio vDPA driver

[Shahaf Shuler <shahafs@mellanox.com>]

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? 

Is nested virtualization is what you have in mind?

> 
> Amongst the main features, all currently supported Virtio spec versions are
> supported (split & packed rings, but only tested with split ring for now) and
> also multiqueue support is added by implementing the cotnrol virtqueue in
> the driver.
> 
> The structure of this driver is heavily based on IFCVF vDPA.
> 
> Maxime Coquelin (15):
>   vhost: remove vhost kernel header inclusion
>   vhost: configure vDPA as soon as the device is ready
>   net/virtio: move control path fonctions in virtqueue file
>   net/virtio: add virtio PCI subsystem device ID declaration
>   net/virtio: save notify bar ID in virtio HW struct
>   net/virtio: add skeleton for virtio vDPA driver
>   net/virtio: add vDPA ops to get number of queue
>   net/virtio: add virtio vDPA op to get features
>   net/virtio: add virtio vDPA op to get protocol features
>   net/virtio: add vDPA op to configure and start the device
>   net/virtio: add vDPA op to stop and close the device
>   net/virtio: add vDPA op to set features
>   net/virtio: add vDPA ops to get VFIO FDs
>   net/virtio: add vDPA op to get notification area
>   doc: add documentation for Virtio vDPA driver
> 
>  config/common_linux                |   1 +
>  doc/guides/nics/index.rst          |   1 +
>  doc/guides/nics/virtio_vdpa.rst    |  45 ++
>  drivers/net/ifc/ifcvf_vdpa.c       |   1 +
>  drivers/net/virtio/Makefile        |   4 +
>  drivers/net/virtio/meson.build     |   3 +-
>  drivers/net/virtio/virtio_ethdev.c | 252 --------
>  drivers/net/virtio/virtio_pci.c    |   6 +-
>  drivers/net/virtio/virtio_pci.h    |   2 +
>  drivers/net/virtio/virtio_vdpa.c   | 918 +++++++++++++++++++++++++++++
>  drivers/net/virtio/virtqueue.c     | 255 ++++++++
>  drivers/net/virtio/virtqueue.h     |   5 +
>  lib/librte_vhost/rte_vdpa.h        |   1 -
>  lib/librte_vhost/rte_vhost.h       |   9 +-
>  lib/librte_vhost/vhost_user.c      |   3 +-
>  15 files changed, 1243 insertions(+), 263 deletions(-)  create mode 100644
> doc/guides/nics/virtio_vdpa.rst  create mode 100644
> drivers/net/virtio/virtio_vdpa.c
> 
> --
> 2.21.0