Re: PCI-DMA: high address but no IOMMU

[Nishanth Aravamudan <nacc@us.ibm.com>]

On 30.10.2005 [15:59:15 +0100], Andi Kleen wrote:
> On Sunday 30 October 2005 15:29, Nishanth Aravamudan wrote:
> 
> > 
> > Ah, silly me, I set IOMMU_DEBUG to Y at some point without realizing.
> > Taking that away removed the issues and I now only get:
> > 
> > [    0.000000] Checking aperture...
> > [    0.000000] CPU 0: aperture @ 4000000 size 32 MB
> > [    0.000000] Aperture from northbridge cpu 0 too small (32 MB)
> > [    0.000000] No AGP bridge found
> > 
> > ...
> > 
> > [   47.737770] PCI-DMA: Disabling IOMMU.
> > 
> > Which makes a lot more sense.
> 
> And everything works when you disable IOMMU_DEBUG? Is that the case
> with the other reporters of this problem too?

Sorry, I realize in retrospect that my post may have been misleading. I
was only commenting that I was seeing the same messages (but not the
same "Kernel panic - not syncing: PCI-DMA: high address but no IOMMU.")
So it works with either IOMMU_DEBUG (which I guess forces the IOMMU on?
-- hence the output of "PCI-DMA: More than 4GB of RAM and no IOMMU"?) or
not. Also note that I only have 2 GB of RAM, so I believe the kernel
made the right decision in disabling the IOMMU (which is used with more
than 3 GB of RAM?) Still, if Michael has IOMMU_DEBUG enabled, it might
change things.

Thanks,
Nish