Re: PCI-DMA: Disabling IOMMU

[Sebastian Biallas]

Prakash Punnoor wrote:
> Am Mittwoch 18 Oktober 2006 17:03 schrieben Sie:
>> Linux ouputs some strange "PCI-DMA: Disabling IOMMU" on booting. It's a
>> ALiveNF4G motherboard with an Athlon64 X2 running vanilla Linux 2.6.18.1
>> (which supports all hardware out of the box, pretty cool).
>>
>> Should I worry about this IOMMU-disabling? All other Linux/IOMMU stuff I
>> found had AGP or BIOS messages nearby, but I only get this single
>> "PCI-DMA: Disabling IOMMU" line, without any hint.
> 
> Unless you have >=4GB of RAM using IOMMU makes no sense, thus it gets 
> disabled.

Thanks for the answer (I thought that IOMMU is also used by VMMs like
XEN, for direct hardware access of the guest. But I might have
misunderstood this).

So maybe this message should read:
PCI-DMA: Not more than 4GiB RAM: Disabling IOMMU
so that people like me don't have to worry.

Regards,
Sebastian

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