linux-kernel - Re: i915-related and general system freezes with specific kernel config // IOMMU

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Date:	Tue, 22 Jan 2013 19:15:05 +0100
From:	Mihai Moldovan <ionic@...ic.de>
To:	Daniel Vetter <daniel.vetter@...ll.ch>
CC:	LKML <linux-kernel@...r.kernel.org>,
	David Woodhouse <dwmw2@...radead.org>,
	intel-gfx <intel-gfx@...ts.freedesktop.org>,
	dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: i915-related and general system freezes with specific kernel
 config // IOMMU

* 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


Download attachment "kern-new-iommu_off.log.bz2" of type "application/x-bzip2" (16365 bytes)

Download attachment "kern-iommu_static_off.log.bz2" of type "application/x-bzip2" (16854 bytes)

Download attachment "smime.p7s" of type "application/pkcs7-signature" (4506 bytes)