Linux Virtualization - Oct 2023 - [PATCH vfio 10/11] vfio/virtio: Expose admin commands over virtio device

On Mon, Oct 02, 2023 at 12:13:20PM -0300, Jason Gunthorpe
wrote:
> ??? This patch series is an implementation of changes that OASIS
> approved.
I think you are fundamentally missing my point.  This is not about
who publish a spec, but how we struture Linux code.

And the problem is that we trea vfio as a separate thing, and not an
integral part of the driver.  vfio being separate totally makes sense
for the original purpose of vfio, that is a a no-op passthrough of
a device to userspace.

But for all the augmented vfio use cases it doesn't, for them the
augmented vfio functionality is an integral part of the core driver.
That is true for nvme, virtio and I'd argue mlx5 as well.

So we need to stop registering separate pci_drivers for this kind
of functionality, and instead have an interface to the driver to
switch to certain functionalities.

E.g. for this case there should be no new vfio-virtio device, but
instead you should be able to switch the virtio device to an
fake-legacy vfio mode.

Assuming the whole thing actually makes sense, as the use case seems
a bit fishy to start with, but I'll leave that argument to the virtio
maintainers.

Similarly for nvme.  We'll never accept a separate nvme-live migration
vfio driver.  This functionality needs to be part of the nvme driver,
probed there and fully controlled there.