Booting kernel-rt-3.2.20-rt32.44 on some servers floods the console with messages like this: ---------------------------------------------- [01:0DRHD: handling fault status reg 2 DMAR:[DMA Rt entry is clear <3>DRHD: handlinentry is clear DRHD: handling fault status reg 2 DMAR:[DMA Read] Request device [01:00.2] fault addr edfe4000 DMAR:[fault reason 02] Present bit in context entry is clear DRHD: handling fault status reg 2 DMAR:[DMA Read] Request device [01:00.2] fault addr edfe4000 DMAR:[fault reason 02] Present bit in context entry is clear DRHD: handling fault status reg 2 ----------------------------------------------
A common issue a couple of boxes is this warning: ------------------------------------------------------------------ DMAR: DRHD base: 0x000000fed90000 flags: 0x1 IOMMU fed90000: ver 1:0 cap c9008020660262 ecap f010da DMAR: RMRR base: 0x000000f1ffd000 end: 0x000000f1ffffff DMAR: No ATSR found IOAPIC id 8 under DRHD base 0xfed90000 Your BIOS has requested that x2apic be disabled. This will leave your machine vulnerable to irq-injection attacks. Use 'intremap=no_x2apic_optout' to override BIOS request. Enabled IRQ remapping in x2apic mode Enabling x2apic Enabled x2apic ------------------------------------------------------------------
Notes from David: > btw ... the DMAR issue ... that's present on upstream 3.2.20 kernel as well ... that's the source from kernel.org without PREEMPT_RT patch but with our config > and intel_iommu=off "removes" this issue ... so we have something to poke further on
Looking at beaker test run on system intel-s3ea2-04.rhts.eng.bos.redhat.com, looks like this might be a system affected by the DMAR issue. Console log: http://beaker-archive.app.eng.bos.redhat.com/beaker-logs/2012/06/2555/255532/544410/console.log
Technical note added. If any revisions are required, please edit the "Technical Notes" field accordingly. All revisions will be proofread by the Engineering Content Services team. New Contents: * Cause: intel-iommu.ko driver has interrupt handling problems with some Sandy Bridge hardware * Consequence: Console gets flooded at boot with DMAR interrupt messages * Fix: default intel-iommu to off and allow loading with kernel command line 'intel_iommu=on' * Result: No DMAR interrupt message flood
from the changelog of 3.2.22-rt34.46, - [mrg] turned off INTEL_IOMMU_DEFAULT_ON (DMAR flood issue) [BZ# 834583]
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. http://rhn.redhat.com/errata/RHSA-2012-1282.html