Re: [libvirt PATCH 01/15] util: properly deal with module vs. driver when binding device to driver

When we recently gained the ability to manually specify a driver to bind to with virsh nodedev-detach, the fragility of this system became apparent - if a user gives the driver name as "vfio_pci", then we would modprobe the module, but then erroneously believe it hadn't been loaded because /sys/bus/pci/drivers/vfio_pci didn't exist. For manual specification of the driver name, this could be dealt with by telling the user "always use the correct name for the driver, don't assume that it is the same as the modulename", but it would still end up confusing people, especially since some drivers do use underscore in their name (e.g. the mlx5_vfio_pci driver/module).

c) All of this is conveniently ignoring the possibility of a VFIO variant driver that is statically linked in the kernel. The entire design of variant driver auto-detection is based on doing a lookup in modules.alias, and that only lists *loadable modules* (not drivers), so unless I'm missing something, it would be impossible to auto-detect a VFIO variant driver that was statically linked. This is beyond libvirt's ability to fix; the best that could be done would be to manually specify the driver name in the libvirt config, which I suppose is better than nothing :-)