Re: [Xen-devel] xl/SR-IOV: disposition of VFs when PF disappears?

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 27.10.14 at 13:57, <Ian.Campbell@xxxxxxxxxxxxx> wrote:
> 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).

Ah, good to know. In that case yes, pciback ought to be honoring
device removal.

> 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.

Yes, it is (at least in practice on the NICs I've seen, but iirc the spec
also says so) - VFs won't work without a PF driver in place.

Jan


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