Current git fails to boot with VT-D enabled due to flood of DMARerrors

[Robert Hancock]

On an Asus P7P55D Pro-based system (Lynnfield CPU), with Intel VT-d 
enabled in the BIOS, on 2.6.30.5 (the previous version I tested) I get 
these lines in dmesg:

DMAR:Host address width 36
DMAR:DRHD (flags: 0x00000001)base: 0x00000000fed90000
DMAR:RMRR base: 0x00000000000e4000 end: 0x00000000000e7fff
DMAR:RMRR base: 0x00000000bf7ec000 end: 0x00000000bf7fffff
Not all IO-APIC's listed under remapping hardware

In current -git, I get these lines as well, but then I get this:

DRHD: handling fault status reg ffffffff
DMAR:[DMA Read] Request device [ff:1f.7] fault addr fffffffffffff000
DMAR:[fault reason 255] Unknown

The last two lines repeat in a continuous flood and the system doesn't 
boot. This happens even if I pass "intel_iommu=off" (which seems like 
it's already the default).

Could be a kernel bug or a BIOS bug, but in the latter case we should 
probably deal with it better. The registers all reading FF seems like 
maybe the registers are disabled or something..
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