INTR-REMAP error with UDD driver

Jeff Webb jeff.webb at
Fri Mar 8 02:35:52 CET 2019

I have implemented a simple UDD mini-driver (interrupt handler) and an associated Xenomai userspace test program.  This pair of programs works as intended on one machine.  When I tried running the same programs on another machine, I got this error when the first interrupt occurred:

kernel: [   75.122305] DMAR: DRHD: handling fault status reg 2
kernel: [   75.123175] DMAR: [INTR-REMAP] Request device [f0:1f.0] fault index ee00 [fault reason 37] Blocked a compatibility format interrupt request

I would guess that the [f0:1f.0] in the message is a PCI bus address, but I don't see this via lspci.  The closest match is:

00:1f.0 ISA bridge [0601]: Intel Corporation Q67 Express Chipset LPC Controller [8086:1c4e] (rev 05)

After the first attempt, I see no more of these messages until I reboot, but the UDD driver never receives an interrupt in any case.

I tried moving my PCI card to five different slots, and finally found one where everything work properly on the second machine.  I can at continue to make progress using the working slot, but I would really like to resolve the issue with the other slots.  Does anyone have any idea what to try next?

I am using these sources:


I have attached the boot log, config, and cpu information.


-Jeff Webb
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