VGA: VBIOS image corrupt (bad pcioffset field)?

[Mogens Jensen <mogens-jensen@xxxxxxxxxxxxxx>]

I'm trying to passthrough the Intel IGD on an Intel Ivy Bridge system
with Xen 4.13 installed.

00:02.0 VGA compatible controller: Intel Corporation 3rd Gen Core
processor Graphics Controller

Booting the DomU fails with this error message:

VGA: VBIOS image corrupt (bad pcioffset field)

"dmesg" prints these messages:

---
pciback 0000:00:02.0: timeout during reset

resource sanity check: requesting [mem 0x000c0000-0x000dffff], which
spans more than PCI Bus 0000:00 [mem 0x000c0000-0x000c3fff window]
caller pci_map_rom+0x6a/0x17d mapping multiple BARs

pciback 0000:00:02.0: Invalid PCI ROM data signature: expecting
0x52494350, got 0xe938aa55
---

"xl dmesg" shows that the entire ring buffer is filled with this
message:

---
(XEN) [VT-D]DMAR:[DMA Read] Request device [0000:00:02.0] fault addr
93b2f5000
---

The system firmware is coreboot configured to use libgfxinit.

Does anyone have an idea how to solve this?

Thanks.


Regards,
Mogens Jensen