Currently, VFIO device initialization depends upon checking if VFIO is enabled. That code looks like this:

> int
> rte_vfio_is_enabled(const char *modname)
> {
>     const int mod_available = rte_eal_check_module(modname) > 0;
>     return default_vfio_cfg->vfio_enabled && mod_available;
> }

The `default_vfio_cfg->vfio_enabled` is set at initialization time with `rte_vfio_enable` function, and is never rechecked afterwards. This makes it so that if `vfio` driver was not loaded at EAL initialization time, any subsequent VFIO device initialization will fail.

To fix that, we would have to re-check the existence of a `vfio` driver every time, however the current API gets in the way, because even though it stores global state, it is implemented in a way that looks like it is supposed to be generic and support multiple driver names (and is never used that way - the only time this API is used is in the EAL initialization when checking for a specific `vfio` driver - i think it's a safe assumption to make that whatever implementation of VFIO is in use, it will depend upon the `vfio` kernel module).

So, current API will need to be changed (it makes no sense anyway) before this bug can be fixed.