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

["Michael S. Tsirkin" <mst@xxxxxxxxxx>]

On Wed, Jun 25, 2014 at 06:15:29PM +0800, Chen, Tiejun wrote:
> 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.

You mean patch #4.

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

Yea. That vile thing seems to mostly be safe to ignore.

-- 
MST

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