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

[Matthew Rosato]

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@xxxxxxxxxxxxx> wrote:
> > > > On 8/13/20 3:55 AM, Oliver O'Halloran wrote:
> > > > > On Thu, Aug 13, 2020 at 5:21 AM Matthew Rosato <mjrosato@xxxxxxxxxxxxx> 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().