INTR-REMAP error with UDD driver

Per Oberg pero at
Thu Mar 28 20:15:58 CET 2019

----- Den 28 mar 2019, på kl 18:10, xenomai xenomai at skrev:

> Hey guys, I was wondering if there is an update on the INTR-REMAP UDD driver
> issue. We have not had any troubleshooting breakthroughs on our end.

> Best Regards,

> Jim Elliott

> ________________________________
> From: Xenomai <xenomai-bounces at> on behalf of Jeff Webb via Xenomai
> <xenomai at>
> Sent: Friday, March 8, 2019 8:07 AM
> To: Jan Kiszka
> Cc: xenomai at
> Subject: Re: INTR-REMAP error with UDD driver

> On Friday, March 8, 2019 1:14 AM, Jan Kiszka <jan.kiszka at> wrote:

> > On 08.03.19 02:35, Jeff Webb via Xenomai wrote:

>> > 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

> > This means the device is under IOMMU interrupt remapping regime, but it was
> > programmed to use a standard MSI/MSI-X request, rather than requesting that
> > parameters (address/data tuple) from the Linux interrupt management layer that
> > will assign a remapping slot and hand out the right values. Now you interrupt is
> > stuck in the filter.

> > Before suggesting the workaround/hack to disable interrupt remapping: How did
> > you program MSI/-X? Via proper Linux pci_* helpers?

> The PCI card I am working with does not implement MSI interrupts, but just uses
> the legacy interrupt pin A. It's confusing to me that this error is associated
> with MSI. Since this behavior is slot-dependent, I figured at first that the
> error is from another device on the same interrupt line, but I get the same
> error on several different slots. There is only one slot where things work as
> expected.

When I read this I realize I have a similar or the same issue. When I moved from 4.9.38 to 4.9.90 the xenomai_peak_pci driver stopped getting interrupts and I got a note about io-remapping and a blocked compability interrupt. It worked on another motherboard. 

The kernel-configs were not equal, and I haven't had time to troubleshoot this. When I switched to the new Peak driver it worked so I focused on other things instead. 

I may be able to contribute in the future.

Best regards
Per Öberg 

> Thanks for the response,

> -Jeff

> > Jan

>> > 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:
> > > linux-4.14.89.tar
> > > ipipe-core-4.14.89-x86-2.patch
> > > xenomai-3.0.8.tar
> > > I have attached the boot log, config, and cpu information.
> > > Thanks,
> > > -Jeff Webb

> > --

> > Siemens AG, Corporate Technology, CT RDA IOT SES-DE
> > Corporate Competence Center Embedded Linux

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