Re: [RFC PATCH net 0/3] virtio-net: allow usage of small vrings

[Alvaro Karsz]

> > This patchset follows a discussion in the mailing list [1].
> >
> > This fixes only part of the bug, rings with less than 4 entries won't
> > work.
> 
> Why the difference?
> 

Because the RING_SIZE < 4 case requires much more adjustments.

* We may need to squeeze the virtio header into the headroom.
* We may need to squeeze the GSO header into the headroom, or block the features.
* At the moment, without NETIF_F_SG, we can receive a skb with 2 segments, we may need to reduce it to 1.
* We may need to change all the control commands, so class,  command and command specific data will fit in a single segment.
* We may need to disable the control command and all the features depending on it.
* We may need to disable NAPI?

There may be more changes..

I was thinking that it may be easier to start with the easier case RING_SIZE >= 4, make sure everything is working fine, then send a follow up patchset with the required adjustments for RING_SIZE < 4.