Xen 4.0.0-rc7 problem/hang with vt-d DMAR parsing

["Pasi Kärkkäinen" <pasik@iki.fi>]

Hello,

Just when I wrote that Xen 4.0.0-rc7 works fine for me.. :)
Ok, so I went to BIOS and enabled VT-d. I haven't used VT-d earlier on this system.

Without serial console (normal VGA text console) I noticed that Xen takes 
long time (25-30 seconds) to check for VT-d stuff, and then in the end 
IO virtualization gets disabled with "Failed to parse ACPI DMAR" message.

When I add iommu=verbose for Xen (dunno if it's related to this new flag),
then Xen just displayes the same messages repeatedly and doesn't start.
(or it takes very long to boot).

Full Xen log from serial console here:
http://pasik.reaktio.net/xen/debug/xen-400-rc7-vt-d-dmar.txt

XEN) Enabling APIC mode:  Flat.  Using 3 I/O APICs
(XEN) ACPI: HPET id: 0xffffffff base: 0xfed00000
(XEN) [VT-D]dmar.c:656: Host address width 36
(XEN) [VT-D]dmar.c:666: found ACPI_DMAR_DRHD:
(XEN) [VT-D]dmar.c:384:   dmaru->address = 0
(XEN) [VT-D]dmar.c:666: found ACPI_DMAR_DRHD:
(XEN) [VT-D]dmar.c:384:   dmaru->address = 0
(XEN) [VT-D]dmar.c:666: found ACPI_DMAR_DRHD:
(XEN) [VT-D]dmar.c:384:   dmaru->address = 0
(XEN) [VT-D]dmar.c:666: found ACPI_DMAR_DRHD:
(XEN) [VT-D]dmar.c:384:   dmaru->address = 0
(XEN) [VT-D]dmar.c:666: found ACPI_DMAR_DRHD:
(XEN) [VT-D]dmar.c:384:   dmaru->address = 0
(XEN) [VT-D]dmar.c:666: found ACPI_DMAR_DRHD:
(XEN) [VT-D]dmar.c:384:   dmaru->address = 0
..
..
..

same stuff continues for a very long time.. I didn't bother waiting 
so I just power cycled the machine in the end.

I'm using Supermicro X7SB4 motherboard with BIOS version 1.2a (the latest available).

-- Pasi