Re: [dpdk-dev] [PATCH] net/virtio-user: add unsupported features mask

["Liu, Yong" <yong.liu@intel.com>]

> -----Original Message-----
> From: Maxime Coquelin [mailto:maxime.coquelin@redhat.com]
> Sent: Tuesday, June 26, 2018 4:08 PM
> To: Liu, Yong <yong.liu@intel.com>; Bie, Tiwei <tiwei.bie@intel.com>
> Cc: Wang, Zhihong <zhihong.wang@intel.com>; dev@dpdk.org
> Subject: Re: [PATCH] net/virtio-user: add unsupported features mask
> 
> 
> 
> On 06/25/2018 03:10 PM, Marvin Liu wrote:
> > This patch introduces unsupported features mask for virtio-user device.
> > For virtio-user server mode, when reconnecting virtio-user will
> > retrieve vhost devcie features as base and then unmask unsupported
> s/devcie/device/
> > features.
> 
> I am not sure to understand why you are doing it like this.
> 
> Shouldn't you just:
>   1. Don't advertise features you don't want to support
>   2. In server mode, save the negotiated features, and re-use it when
>      reconnect happens?
> 
Maxime,
I think our vhost reconnect design is following qemu vhost-user server mode. Virtio-user will try to support connected vhost device.
So device_features of virtio user just retrieve from vhost device. 
And in server mode, we have recorded previous feature bits and used it for later negotiation. But virtio user device_features which may has changed by vdev parameters. This mask will guaranty device_features correct.

Thanks,
Marvin

> Also, I find "unmask" a bit misleading, why not something like "unsupp"
> or "unsupported"?
> 
> Thanks,
> Maxime