Re: [dpdk-dev] [PATCH] VFIO: Avoid to enable vfio while the module not loaded

["Burakov, Anatoly" <anatoly.burakov@intel.com>]

Hi Michael

> But indeed, when try to unload both vfio and vfio_iommu_type1,
> /dev/vfio/vfio still there, I'm also surprise.
> 
> My ENV is fedora20, kernel version 3.6.7-200 X86_64.
> 
> Believe or not, you can have a try, it seems a kernel issue.
> 
> When you unload both two modules, then open /dev/vfio/vfio, you will find
> it can be opened with no errors(but this time both two modules loaded
> automatically, strange enough)
> 

Thanks to Sergio, we found a most likely cause for this. This patch to Linux kernel by Alex Williamson of Red Hat:

https://lkml.org/lkml/2013/12/12/421

it seems, however, that it has been merged into 3.14. Your kernel, by your own admission, is 3.6. Are you sure this is the right kernel version? Because my own machine has Fedora 18 with a 3.11 kernel, and it (correctly) does not display this behavior. So unless Fedora 20 backported those changes to kernel 3.6, this shouldn't happen on your set up. (but it doesn't really matter, just FYI - the patch still should be fixed and resubmitted, just as we discussed)

Thanks,
Anatoly