On Sun, Jan 20, 2013 at 12:25:07PM +0100, Udo van den Heuvel wrote: > Hello Jörg, > > Hardware issue? What is wrong c.q. happening?
I think it falls under Erratum 455 (which does not mention IOMMU specifically). Point is, there is a hardware workaround for this to make the IOMMU work, but your BIOS does not enable it. > > I have this: > > # dmesg|grep IOMMU > [ 0.000000] ACPI: IVRS 000000009dd12420 00070 (v02 AMD AMDIOMMU > 00000001 AMD 00000000) > [ 0.000000] Please enable the IOMMU option in the BIOS setup > [ 1.125636] AMD-Vi: Found IOMMU at 0000:00:00.2 cap 0x40 > > So kernel says I have no IOMMU but still one is found? (!?) The "Please enable IOMMU ..." line tells you about the GART, not the AMD IOMMU. This is a frequent source of confusion, we probably should remove that line. Trinity has no GART, so there is nothing to find :) > In PC-BIOS I assume? > I did not yet find an option, but this is the first occurrence. > Can the BIOS vendor fix this? If so: please explain so I cna contact > Gigabyte (motherboard manufacturer) Yes, the BIOS vendor can fix this issue. They need to disable NB clock gating for the IOMMU. > What is the impact of disabling the IOMMU? Well, it has some security impact and if you have more than 4GB of RAM maybe also some slight performance impact due to DMA bounce buffering. But thats still better as a system that stops working after some time. Joerg -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/