Re: [Qemu-devel] [v5][PATCH 0/5] xen: add Intel IGD passthrough support

[Chen, Tiejun]

On 2014/6/25 18:09, Michael S. Tsirkin wrote:
> On Wed, Jun 25, 2014 at 11:59:21AM +0200, Paolo Bonzini wrote:
> > Il 25/06/2014 11:55, Michael S. Tsirkin ha scritto:
> > > > You're saying we will reserve a free BAR to address those information to
> > > > expose to guest, but which device does this free BAR belong to? The video
> > > > device? Or PCH/MCH?
> > >
> > > If you just want to pass a couple of IDs, then don't, it's a waste.
> > > But I still don't know what problem you are trying to solve,
> > > looking at guest driver did not help.
> >
> > It's not just a couple of IDs, it's also random fields of the MCH
> > configuration space.  Grep drivers/gpu/drm/i915 for bridge_dev.
> >
> > Paolo
>
> I did, it seems to look for device at 0,0:
>
>         static int i915_get_bridge_dev(struct drm_device *dev)
>         {
>                 struct drm_i915_private *dev_priv = dev->dev_private;
>
>                 dev_priv->bridge_dev = pci_get_bus_and_slot(0, PCI_DEVFN(0, 0));
>                 if (!dev_priv->bridge_dev) {
>                         DRM_ERROR("bridge device not found\n");
>                         return -1;
>                 }
>                 return 0;
>         }
>
> are you sure this is the ISA bridge device? these patches put it at 1f.

:) The IGD is too complex to understand.

The i915 driver needs to access that host bridge at 00:00.0, and this is 
addressed in patch #3.

Also the i915 needs that ISA bridge at 00:1f.0, this is just what we're 
discussing now.

Thanks
Tiejun