Re: [Qemu-devel] [PULL 15/17] spapr_pci: Advertise access to PCIe extended config space

[David Gibson <david@gibson.dropbear.id.au>]

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On Fri, Mar 10, 2017 at 04:25:21PM +0100, Andrea Bolognani wrote:
> On Fri, 2017-03-03 at 14:25 +1100, David Gibson wrote:
> > The (paravirtual) PCI host bridge on the 'pseries' machine in most
> > regards acts like a regular PCI bus, rather than a PCIe bus.  Despite
> > this, though, it does allow access to the PCIe extended config space.
> > 
> > We already implemented the RTAS methods to allow this access.. but
> > forgot to put the markers into the device tree so that guest's know it
> > is there.  This adds them in.
> > 
> > With this, a pseries guest is able to view extended config space on
> > (for example an e1000e device.  This should be enough to allow guests
> > to use at least some PCIe devices.
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  hw/ppc/spapr_pci.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> > index 2a3499e..919d3c2 100644
> > --- a/hw/ppc/spapr_pci.c
> > +++ b/hw/ppc/spapr_pci.c
> > @@ -1321,6 +1321,10 @@ static int spapr_populate_pci_child_dt(PCIDevice *dev, void *fdt, int offset,
> >      _FDT(fdt_setprop(fdt, offset, "assigned-addresses",
> >                       (uint8_t *)rp.assigned, rp.assigned_len));
> >  
> > +    if (pci_is_express(dev)) {
> > +        _FDT(fdt_setprop_cell(fdt, offset, "ibm,pci-config-space-type", 0x1));
> > +    }
> > +
> >      return 0;
> >  }
> 
> I've just realized that this is not tied to the pseries-2.9
> machine type, which means existing guests will suddenly get
> access to the Extended Config Space after upgrading QEMU.
> 
> I'm not sure this will cause any issue in practice, but it
> seems like it would be safer to enable the Extended Config
> Space only for pseries-2.9 and newer machine types.

That's a good point.  I've put a fix into ppc-for-2.9, will send a
pull request shortly.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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