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

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.


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.


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