Re: [Qemu-devel] [PATCH v2 1/4] pci: Make use of the devfn property when registering new devices

[Knut Omang <knut.omang@oracle.com>]

On Tue, 2014-09-02 at 16:03 +0300, Michael S. Tsirkin wrote:
> On Tue, Sep 02, 2014 at 01:00:03PM +0200, Knut Omang wrote:
> > Without this, the devfn argument to pci_create_*()
> > does not affect the assigned devfn.
> > 
> > Needed to support (VF_STRIDE,VF_OFFSET) values other than (1,1)
> > for SR/IOV.
> > 
> > Signed-off-by: Knut Omang <knut.omang@oracle.com>
> 
> Sorry, I don't understand the explanation exactly.
> pci_dev->devfn is not set correctly? why?

This probably has been broken by some of the qom adaptation if I
understand it right: The devfn parameter in pci_create_multifunction()
is only used to set the "addr" property, which in turn is not used
anywhere as far as I can see. So the pci_dev->devfn has it's default
value.

What I observe is that when I enable VFs with the igb example device,
now with stride = 2 and offset 0x80 (as my real lab hardware implements)
and enable some VFs, this yields devfn's of 0x80, 0x82, 0x84... sent as
parameters to pci_create..(), I still end up with this (eg. 
the "natural" next function will be selected instead of the provided
devfn):

01:00.0 Ethernet controller: Intel Corporation 82576 Gigabit Network Connection (rev 01)
01:00.1 Ethernet controller: Intel Corporation 82576 Virtual Function (rev 01)
01:00.2 Ethernet controller: Intel Corporation 82576 Virtual Function (rev 01)
01:00.3 Ethernet controller: Intel Corporation 82576 Virtual Function (rev 01)
01:00.4 Ethernet controller: Intel Corporation 82576 Virtual Function (rev 01)

With this patch applied, I get the expected:

01:00.0 Ethernet controller: Intel Corporation 82576 Gigabit Network Connection (rev 01)
01:10.0 Ethernet controller: Intel Corporation 82576 Virtual Function (rev 01)
01:10.2 Ethernet controller: Intel Corporation 82576 Virtual Function (rev 01)
01:10.4 Ethernet controller: Intel Corporation 82576 Virtual Function (rev 01)
01:10.6 Ethernet controller: Intel Corporation 82576 Virtual Function (rev 01)

> > ---
> >  hw/pci/pci.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> > index daeaeac..6b21dee 100644
> > --- a/hw/pci/pci.c
> > +++ b/hw/pci/pci.c
> > @@ -1757,7 +1757,7 @@ static int pci_qdev_init(DeviceState *qdev)
> >      bus = PCI_BUS(qdev_get_parent_bus(qdev));
> >      pci_dev = do_pci_register_device(pci_dev, bus,
> >                                       object_get_typename(OBJECT(qdev)),
> > -                                     pci_dev->devfn);
> > +                                     object_property_get_int(OBJECT(qdev), "addr", NULL));
> >      if (pci_dev == NULL)
> >          return -1;
> >  
> > -- 
> > 1.9.0