Re: Kernel panic with intel_iommu=on

[Valdis . Kletnieks]

On Wed, 12 Oct 2011 10:19:55 PDT, Dave Hansen said:
> I'm seeing this all of a sudden on 3.1 kernels.  It might be because of
> the firefox upgrade to 5.0 that others were talking about.  But, it's
> quite easy to trigger.  Seems to happen in the first 10 minutes of using
> the system.  I was only able to capture this with netconsole.

I was seeing DMAR issues as well, but I figured it was self-inflicted because
it was due to the NVidia binary driver. Rebooted with 'intel_iommu=off' and it
behaved itself.  Basically, I got a flood of messages like these:

Oct 12 17:20:09 turing-police kernel: [  301.401157] DRHD: handling fault status reg 2
Oct 12 17:20:09 turing-police kernel: [  301.401164] DMAR:[DMA Read] Request device [01:00.0] fault addr d5b76000
Oct 12 17:20:09 turing-police kernel: [  301.401166] DMAR:[fault reason 01] Present bit in root entry is clear

Oct 12 17:20:13 turing-police kernel: [  305.615039] DRHD: handling fault status reg 2
Oct 12 17:20:13 turing-police kernel: [  305.615047] DMAR:[DMA Read] Request device [01:00.0] fault addr 110de9000
Oct 12 17:20:13 turing-police kernel: [  305.615048] DMAR:[fault reason 01] Present bit in root entry is clear

Oct 12 17:20:14 turing-police kernel: [  306.056109] DRHD: handling fault status reg 2
Oct 12 17:20:14 turing-police kernel: [  306.056116] DMAR:[DMA Read] Request device [01:00.0] fault addr ca861000
Oct 12 17:20:14 turing-police kernel: [  306.056117] DMAR:[fault reason 01] Present bit in root entry is clear

Oct 12 17:20:14 turing-police kernel: [  306.059950] DRHD: handling fault status reg 2
Oct 12 17:20:14 turing-police kernel: [  306.059959] DMAR:[DMA Read] Request device [01:00.0] fault addr ca861000
Oct 12 17:20:14 turing-police kernel: [  306.059960] DMAR:[fault reason 01] Present bit in root entry is clear

Oct 12 17:20:14 turing-police kernel: [  306.064171] DRHD: handling fault status reg 2
Oct 12 17:20:14 turing-police kernel: [  306.064179] DMAR:[DMA Read] Request device [01:00.0] fault addr ca861000
Oct 12 17:20:14 turing-police kernel: [  306.064180] DMAR:[fault reason 01] Present bit in root entry is clear

If that tells the iommu people something, fine.  If it doesn't, that's OK too, I'll
take it up with NVidia.

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