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From:   Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Date:   Sun, 31 Oct 2021 11:37:51 -0400
Message-ID: <CA+FuTScP-LcRO5PXjohzDS8NXmF6j6u5nxprtnj89q6Cucmgbw@mail.gmail.com>
Subject: Re: [RFC PATCH 3/4] drivers/net/virtio_net: Added basic RSS support.
To:     Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Cc:     Andrew Melnychenko <andrew@daynix.com>, mst@redhat.com,
        jasowang@redhat.com, davem@davemloft.net, kuba@kernel.org,
        virtualization@lists.linux-foundation.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, yuri.benditovich@daynix.com,
        yan@daynix.com
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> > +               hdr_hash = (struct virtio_net_hdr_v1_hash *)(hdr);
> > +
> > +               switch (hdr_hash->hash_report) {
> > +               case VIRTIO_NET_HASH_REPORT_TCPv4:
> > +               case VIRTIO_NET_HASH_REPORT_UDPv4:
> > +               case VIRTIO_NET_HASH_REPORT_TCPv6:
> > +               case VIRTIO_NET_HASH_REPORT_UDPv6:
> > +               case VIRTIO_NET_HASH_REPORT_TCPv6_EX:
> > +               case VIRTIO_NET_HASH_REPORT_UDPv6_EX:
> > +                       rss_hash_type = PKT_HASH_TYPE_L4;
> > +                       break;
> > +               case VIRTIO_NET_HASH_REPORT_IPv4:
> > +               case VIRTIO_NET_HASH_REPORT_IPv6:
> > +               case VIRTIO_NET_HASH_REPORT_IPv6_EX:
> > +                       rss_hash_type = PKT_HASH_TYPE_L3;
> > +                       break;
> > +               case VIRTIO_NET_HASH_REPORT_NONE:
> > +               default:
> > +                       rss_hash_type = PKT_HASH_TYPE_NONE;
> > +               }
>
> Is this detailed protocol typing necessary? Most devices only pass a bit is_l4.
> > +static void virtnet_init_default_rss(struct virtnet_info *vi)
> > +{
> > +       u32 indir_val = 0;
> > +       int i = 0;
> > +
> > +       vi->ctrl->rss.table_info.hash_types = vi->rss_hash_types_supported;
>
> Similar to above, and related to the next patch: is this very detailed
> specification of supported hash types needed? When is this useful? It
> is not customary to specify RSS to that degree.

My bad. This is also implemented by bnxt, for one. I was unaware of
this feature.