On Tue, Aug 04, 2015 at 10:05:45PM +0500, Valentine Sinitsyn wrote:
> Not directly related to the issue David discovered, but as we
> discuss IVRS handling: the specification says that ACPI tables data
> overrides what's in hardware registers (Sect. 5). To the best of my
> understanding, this means e.g. I should take HATS value not from EFR
> but from IVHD Type 10 block. However, amd_iommu driver code checks
> for features directly - for what reason? I'm not suggesting this is
> a bug, but rather asking your opinion here.
In my experience the hardware is more trustable than the ACPI table. We
had several issues with broken BIOSes that screw up the IVRS ACPI table,
so my trust in the values there is limited.
Joerg
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