amd64 iommu causing corruption? (was Re: data corruption with nvidia chipsets and IDE/SATA drives // memory hole mapping related bug?!)

[Chris Wedgwood]

On Mon, Dec 11, 2006 at 10:24:02AM +0100, Karsten Weiss wrote:

> We could not reproduce the data corruption anymore if we boot the
> machines with the kernel parameter "iommu=soft" i.e. if we use
> software bounce buffering instead of the hw-iommu. (As mentioned
> before, booting with mem=2g works fine, too, because this disables
> the iommu altogether.)

I can confirm this also seems to be the case for me, I'm still doing
more testing to confirm this.  But it would seem:

nforce4, transfer of a large mount of data with 4GB+ of RAM I get some
corruption.  This is present on both the nv SATA and also Sil 3112
connected drives.

Using iommu=soft so far seems to be working without any corruption.



I still need to do more testing on other machines which have less
memory (so the IOMMU won't be in use there either) and see if there
are problems there.
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