Re: [RFC 03/20] vfio: Add vfio_[un]register_device()

[Jason Gunthorpe]

On Wed, Sep 22, 2021 at 09:23:34AM +0000, Tian, Kevin wrote:

> > Providing an ioctl to bind to a normal VFIO container or group might
> > allow a reasonable fallback in userspace..
> 
> I didn't get this point though. An error in binding already allows the
> user to fall back to the group path. Why do we need introduce another
> ioctl to explicitly bind to container via the nongroup interface? 

New userspace still needs a fallback path if it hits the 'try and
fail'. Keeping the device FD open and just using a different ioctl to
bind to a container/group FD, which new userspace can then obtain as a
fallback, might be OK.

Hard to see without going through the qemu parts, so maybe just keep
it in mind

Jason