Re: xl/SR-IOV: disposition of VFs when PF disappears?

[Ian Campbell <Ian.Campbell@eu.citrix.com>]

On Mon, 2014-10-27 at 12:36 +0000, Jan Beulich wrote:
> All,
> 
> Intel reports that the sequence
> 
> - xl pci-assignable-add <VF>
> - briefly run guest using that device [not sure whether that's really a
>   necessary step]
> - xl pci-assignable-add <PF of VF>
> 
> results in both VF and PF being listed as assignable (the fact that as a
> result the PF handed to a guest doesn't work is secondary here, as I
> think this is a driver issue). Is that really how it should be? Shouldn't
> instead all VFs get removed when the PF device (e.g. due to the
> PF driver getting unloaded, which is a necessary part of making it
> assignable) goes away? Or is it required for the admin to manually
> remove the assignable VFs prior to making the PF go away?

xl is just controlling/exposing the set of devices which are bound to
pciback here. (pci-assignable-list is literally a readdir loop over the
relevant sysfs dir).

I'm not sure if it should be up to (lib)xl, pciback or the core Linux
pci stuff to handle the creation/destruction of VF devices when the PF
driver is unbound/assigned. In fact I'm not even sure if VF lifetime is
in any way tied to the PF driver state.

I've added Konrad for a kernel-size pciback perspective.

Ian.