Re: [Qemu-devel] [PATCH v2] vfio/igd: handle q35 machine type

[Gerd Hoffmann]

On Mo, 2016-03-07 at 14:41 -0700, Alex Williamson wrote:
> On Fri,  4 Mar 2016 09:41:53 +0100
> Gerd Hoffmann <address@hidden> wrote:
> 
> > Basically skip the lpc quirks with -M q35.
> > Applies on top of the vfio-igd patch series by alex.
> > 
> > Signed-off-by: Gerd Hoffmann <address@hidden>
> > ---
> >  hw/vfio/pci-quirks.c | 15 +++++++++++++++
> >  1 file changed, 15 insertions(+)
> > 
> > diff --git a/hw/vfio/pci-quirks.c b/hw/vfio/pci-quirks.c
> > index 5828362..1757e3d 100644
> > --- a/hw/vfio/pci-quirks.c
> > +++ b/hw/vfio/pci-quirks.c
> > @@ -12,6 +12,7 @@
> >  
> >  #include "qemu/osdep.h"
> >  #include "hw/nvram/fw_cfg.h"
> > +#include "hw/i386/ich9.h"
> >  #include "pci.h"
> >  #include "trace.h"
> >  #include "qemu/range.h"
> > @@ -1410,6 +1411,7 @@ int vfio_pci_igd_lpc_init(VFIOPCIDevice *vdev,
> >                             struct vfio_region_info *region)
> >  {
> >      DeviceClass *dc = DEVICE_GET_CLASS(vdev);
> > +    PCIBus *bus;
> >      PCIDevice *lpc_bridge;
> >      int ret;
> >  
> > @@ -1423,6 +1425,19 @@ int vfio_pci_igd_lpc_init(VFIOPCIDevice *vdev,
> >  
> >      dc->hotpluggable = false;
> >  
> > +    bus = pci_device_root_bus(&vdev->pdev);
> > +    lpc_bridge = pci_find_device(bus, 0, PCI_DEVFN(0x1f, 0));
> > +    if (lpc_bridge) {
> > +        const char *type = object_get_typename(OBJECT(lpc_bridge));
> > +        if (strcmp(type, TYPE_ICH9_LPC_DEVICE) == 0) {
> > +            /*
> > +             * q35 lpc present, leave it as-is.
> > +             * linux kernel 4.5+ can deal with this.
> 
> What about anything older?  I assume we want to support current
> distributions.  Based on this patch it seems like we also want to test
> first if the lpc device is present, create it if not, then probably
> copy host data into it.  Thanks,

q35 already has a isa bridge @ 1f.0, and it's not a dummy device but
emulates the ich9 lpc.  Just overwriting the identity of that device
isn't a good idea I think.

cheers,
  Gerd