RE: [virtio-comment] RE: [PATCH v3 2/2] content: Support enabling virtqueue after DRIVER_OK stage

[Parav Pandit <parav@nvidia.com>]

> From: Cornelia Huck <cohuck@redhat.com>
> Sent: Friday, October 27, 2023 5:16 PM

> "config registers" are transport specific. If they aren't an efficient method, then
> the transport needs to come up with something else -- but it's the task of the
> *transport* to provide something useful. The device should not need to do
> anything beyond specifying that it can support adding vqs dynamically, and
> exposing the upper boundary to the number of queues.
>
You are welcome to propose to PCI-SIG such enhancements. :)
We cannot keep blind eye to transport and say, virtio will expand infinity registers without caring about underlying transport limitations and efficiencies.

There have been many discussions in past across many device + cpu vendors in various virtio and non virtio forums.
I would like to share that the industry does not prefer to put things as infinite set of registers unless its most fundamental thing needed to bootstrap the device.

> >
> > Out of 19 devices, 6 devices already has cvq.
> > Out of remaining 13 devices, 12 devices have fixed number of queues as they
> small enough in functionality that won't need a scale and dynamism either.
> > So for dynamic resource management reusing the existing cvq is more
> efficient for the devices.
> 
> They have a device-specific cvq, which is used in a device-specific way for
> device-specific purposes. I don't see how turning them into frankencvqs is
> "efficient".
Sure, they are device specific, but we can define generic set of commands in basic facilities, which each device type can send via their cvq.
It is only matter of drafting it.