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

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Feb 08, 2023 at 05:18:32AM +0000, Parav Pandit wrote:
> > From: Heng Qi <hengqi@linux.alibaba.com>
> > Sent: Tuesday, February 7, 2023 10:25 PM
> 
> [..]
> > >>
> > >> Do you think we need both hash_types and hash_tunnel_types?
> > > In struct virtio_net_config we need two fields.
> > > a. supported_hash_types (already exists) b. supported_hash_tunnel_type
> > > -> bitmap indicating for which outer headers, inner hash calculation is
> > supported.
> > 
> > Thanks for the suggestion, we seem to have reached an agreement.
> > 
> > >
> > > In struct virtio_net_hdr we need two fields.
> > > a. hash_report (already exists)
> > > b. hash_tunnel_type 8 bits -> absolute value indicating which outer header
> > exists when inner header hash calculated.
> > > You already have it in your patch named as hash_report_tunnel.
> > > May be better to name as hash_report_tunnel_type to make it clearer that its
> > type.
> > 
> > Sure.
> > 
> > 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?

Well we have hash_report which is kind of similar (and also kind of
pointless but I think it's there because WHQL wants it). Maybe we can steal
some bits from there instead of a new field?


I have a follow up question though: are we only hashing the inner header
or both inner and outer header? Somewhat confused on this.

In fact, CC Yuri for thoughts and suggestions from windows side of
things.

-- 
MST