AMD IOMMU causing filesystem corruption

[Samuel Sieb]

I filed a bug in bugzilla, but I wasn't sure what category to put it in, 
so I suspect I ended up picking one that doesn't get looked at much.

https://bugzilla.kernel.org/show_bug.cgi?id=195051

The issue is that on a specific Acer laptop with a dual-core A9, if I 
don't disable the IOMMU using iommu=off, it has immediate and rapidly 
fatal filesystem corruption by the time a user logs into the desktop. 
What led me to try that was at one point I noticed an error message 
about the iommu in the logs.  However, I did not have a chance to save 
that due to the corruption obliterating the log files.