Re: [PATCH v2] PCI: Introduce flag for detached virtual functions

Matthew Rosato
2020-08-13T13:11:35Z

On 8/13/20 8:34 AM, Niklas Schnelle wrote:
>
>
> On 8/13/20 12:40 PM, Niklas Schnelle wrote:
>>
>>
>> On 8/13/20 11:59 AM, Oliver O'Halloran wrote:
>>> On Thu, Aug 13, 2020 at 7:00 PM Niklas Schnelle <schnelle@linux.ibm.com> wrote:
>>>>
>>>>
>>>> On 8/13/20 3:55 AM, Oliver O'Halloran wrote:
>>>>> On Thu, Aug 13, 2020 at 5:21 AM Matthew Rosato <mjrosato@linux.ibm.com> wrote:
>>>>>> *snip*
>>>>>> diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c
>>>>>> index 3902c9f..04ac76d 100644
>>>>>> --- a/arch/s390/pci/pci.c
>>>>>> +++ b/arch/s390/pci/pci.c
>>>>>> @@ -581,6 +581,14 @@ int pcibios_enable_device(struct pci_dev *pdev, int mask)
>>>>>> {
>>>>>> struct zpci_dev *zdev = to_zpci(pdev);
>>>>>>
>>>>>> + /*
>>>>>> + * If we have a VF on a non-multifunction bus, it must be a VF that is
>>>>>> + * detached from its parent PF. We rely on firmware emulation to
>>>>>> + * provide underlying PF details.
>>>>>> + */
>>>>>> + if (zdev->vfn && !zdev->zbus->multifunction)
>>>>>> + pdev->detached_vf = 1;
>>>>>
>>>>> The enable hook seems like it's a bit too late for this sort of
>>>>> screwing around with the pci_dev. Anything in the setup path that
>>>>> looks at ->detached_vf would see it cleared while anything that looks
>>>>> after the device is enabled will see it set. Can this go into
>>>>> pcibios_add_device() or a fixup instead?
>>>>>
>>>>
>>>> This particular check could go into pcibios_add_device() yes.
>>>> We're also currently working on a slight rework of how
>>>> we establish the VF to parent PF linking including the sysfs
>>>> part of that. The latter sadly can only go after the sysfs
>>>> for the virtfn has been created and that only happens
>>>> after all fixups. We would like to do both together because
>>>> the latter sets pdev->is_virtfn which I think is closely related.
>>>>
>>>> I was thinking of starting another discussion
>>>> about adding a hook that is executed just after the sysfs entries
>>>> for the PCI device are created but haven't yet.
>>>
>>> if all you need is sysfs then pcibios_bus_add_device() or a bus
>>> notifier should work
>>
>> So this might go a bit off track but the problem is that
>> on s390 a VF can be disabled and reenabled with disable_slot()/enable_slot().
>> In this case pcibios_bus_add_device() is not called again but
>> the PF/VF link needs to be reestablished.
>
> Scratch that I must have made some stupid mistake last time I tried
> this, with your suggestion I tried again and it works perfectly
> moving the setup into pcibios_bus_add_device().
> Thank you, this is actually much nicer!
>

OK, and I can likewise relocate the setting of detached_vf to
pcibios_bus_add_device().