[Intel-gfx] i915-related and general system freezes with specific kernel config // IOMMU

[Mihai Moldovan]

* On 21.01.2013 07:11 PM, Mihai Moldovan wrote:
> I'm also currently testing a kernel without the Intel IOMMU feature
> [CONFIG_INTEL_IOMMU=n, but CONFIG_IOMMU_SUPPORT=y]. [...] At least
> not seeing USB and PCI(e) issues. I'll leave the box running for some
> more [time] [...]

No freezes for >22h, seems to be fine.


> [...] and will afterwards disable IOMMU as a whole to see if I hit
> USB and PCI(e) issues again with that combination.

The systems seems to run stable with CONFIG_IOMMU_SUPPORT=n set, too. This is
expected.
However: unlike during earlier tests when I disabled IOMMU and Intel IOMMU via
kernel/boot parameters, I am not seeing any DMA mapping errors.

There seems to be a difference between disabling IOMMU/Intel IOMMU statically in
the kernel compared to disabling it via kernel parameter. Is this another bug?

I've attached both kernel ring buffer logs (minus the timings for easier diffing.)

  [*] kern-new-iommu_off.log.bz2 disables IOMMU and Intel IOMMU via boot parameter
  [*] kern-iommu_static_off.log.bz2 has CONFIG_IOMMU_SUPPORT=n set and any IOMMU
support statically disabled (also consequently DMAR)



Mihai

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