RE: [virtio-dev] Re: [virtio-comment] Re: [PATCH v7] virtio-net: support inner header hash

[Parav Pandit <parav@nvidia.com>]

> From: Heng Qi <hengqi@linux.alibaba.com>
> Sent: Thursday, February 9, 2023 12:21 AM

> >>>> Thanks for your reply.
> >>> I had one last question. Why do we need to inform the
> >> hash_report_tunnel_type of the outer header in the virtio_net_hdr?
> >>> Is this for debug? Or is there a use case that will process this value?
> >> The driver may use it to do some statistical information, or do some
> >> rx classification based on the rx hash, and we'd better not hide
> >> information from the driver.
> >>
> > Statistical information is better gathered via stats, instead of adding such code
> in driver data path.
> 
> A cautionary note : the source of hash_report_tunnel comes from the
> discussion here
> https://lists.oasis-open.org/archives/virtio-dev/202211/msg00063.html

> If I understand correctly, if virtio-net-hdr also has hash_report_tunnel, how
> does the driver do statistics?
I am asking to avoid having hash_report_tunnel in virtio_net_hdr if it is only for the statistics purpose.
If it has more use than just statistics, I like to understand its use in rx packet processing flow, if there is any and to describe in commit log too.

Below [1] says about driver doing some rx classification. It is unclear on inner or outer.
The response is not very clear to me, about how this field is useful.

[1] https://lists.oasis-open.org/archives/virtio-dev/202211/msg00063.html

If driver needs to know the statistics of it, it can query them from the device by introducing statistics cmd.