RE: [PATCH v19] virtio-net: support inner header hash

[Parav Pandit <parav@nvidia.com>]

> From: Jason Wang <jasowang@redhat.com>
> Sent: Wednesday, June 28, 2023 1:38 AM

[..]
> > Provisioning is far simpler thing to do in device specific way than asking device
> to store this value in onchip area which is rarely accessed.
> 
> Are you suggesting to not place any new fields in the config space?
> 
Yes.

> struct virtio_net_config {
>         u8 mac[6];
>         le16 status;
>         le16 max_virtqueue_pairs;
>         le16 mtu;
>         le32 speed;
>         u8 duplex;
>         u8 rss_max_key_size;
>         le16 rss_max_indirection_table_length;
>         le32 supported_hash_types;
> };
> 
> Which of the above do you think can be accessed frequently and which part of
> the spec says it must be stored in the onchip area?
> 
Most are not accessed frequently.
The fact that they are in MMIO a device needs to place in a memory with tight latency budget.
Spec is not going to talk on onchip area, it is the reflection of spec that forces certain inefficient implementation .