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- The guest drivers had to have access to the VGA IO ports at 0x3C0 (see http://wiki.osdev.org/VGA_Hardware#Port_0x3C0). Pci-dm-helper make it available to guests using xc_domain_ioport_permission.
- The guest drivers had to have access to the IGD Opregion MMIO region. The base address is fetched from the IGD device's config space. Pci-dm-helper used to fetch the location and make it available to guests using xc_domain_iomem_permission.
- The actual VGABios of the IGD card had to be loaded into the guest at the legacy OROM slot 0xC0000. As noted above, pci-dm-helper did this.
- The guest drivers got a filtered list of IGD device capabilities. This was done in IOEMU (IIRC?). The functionality was probably dropped in the QEMU 1.4 uprev.
- The guest drivers needed access to the IGD device and platform's vendor capabilities stored as a vendor specific capability on the host bridge device (00:0.0). This was done in IOEMU pass-through code. The functionality dropped in the QEMU 1.4 uprev.
- The guest drivers expected to see a legacy ISA bridge surfaced at 00:1f.0 on the PCI bus. A dummy device was surfaced by IOEMU. The functionality dropped in the QEMU 1.4 uprev.
- The QEMU support patch 0007-pci-reserve-igd-slot.patch is gone.
Several versions of IGD passthrough were posted for inclusion in Xen/QEMU. If IGD passthrough were brought back, it should be based on this work.
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