Re: [dpdk-dev] [RFC 0/3] net/virtio: add vdpa device config support

[Adrian Moreno <amorenoz@redhat.com>]

On 3/18/21 11:35 PM, Maxime Coquelin wrote:
> This patch adds vDPA device config space requests support.
> For now, it only adds MAC address get and set. It may be
> extended in next revision to support other configs like
> link state.
> 
> Regarding the MAC selection strategy, if devargs MAC address
> is set by the user and valid, the driver tries to store it
> in the device config space, then it reads the MAC address
> back from the device config, which will be used. If not set
> in devargs or invalid, it tries to read it from the device.
> If it fails, a random MAC will be used.
> 
> I'm interrested to know your feedback on this strategy.

In general, I think it's a reasonable strategy. Once we have cq support, things
will be a bit easier.

Some questions:
How should we interpret failure to configure the mac (i.e: after set and get,
they still don't match)? Should we fail virtio_user_dev_init if the
configuration provided by devargs is not successfully applied?

Should a zero mac be treated differntly as qemu does? [1]

[1]
https://patchwork.ozlabs.org/project/qemu-devel/patch/20210302142014.141135-3-mst@redhat.com/


> It has been tested with vDPA simulator, which only supports
> getting the MAC address, and witch CX6 which supports neither
> getting or setting MAC address (and so devarg or random MAC is
> used). IFCVF driver seems to support both getting and setting
> the MAC, I have a try with it before next revision.

Does cx6 negotiate VIRTIO_NET_F_MAC?

> 
> Maxime Coquelin (3):
>   net/virtio: keep device and frontend features separated
>   net/virtio: add device config support to vDPA
>   net/virtio: add MAC device config getter and setter
> 
>  drivers/net/virtio/virtio_user/vhost.h        |  3 +
>  drivers/net/virtio/virtio_user/vhost_vdpa.c   | 69 +++++++++++++++
>  .../net/virtio/virtio_user/virtio_user_dev.c  | 88 +++++++++++++++----
>  .../net/virtio/virtio_user/virtio_user_dev.h  |  2 +
>  drivers/net/virtio/virtio_user_ethdev.c       | 12 ++-
>  5 files changed, 151 insertions(+), 23 deletions(-)
> 

-- 
Adrián Moreno