[kernel] powerpc/npu: Do not try invalidating 32bit table when 64bit table is enabled

[Michael Ellerman]

On Tue, 2018-02-13 at 05:51:35 UTC, Alexey Kardashevskiy wrote:
> GPUs and the corresponding NVLink bridges get different PEs as they have
> separate translation validation entries (TVEs). We put these PEs to
> the same IOMMU group so they cannot be passed through separately.
> So the iommu_table_group_ops::set_window/unset_window for GPUs do set
> tables to the NPU PEs as well which means that iommu_table's list of
> attached PEs (iommu_table_group_link) has both GPU and NPU PEs linked.
> This list is used for TCE cache invalidation.
> 
> The problem is that NPU PE has just a single TVE and can be programmed
> to point to 32bit or 64bit windows while GPU PE has two (as any other PCI
> device). So we end up having an 32bit iommu_table struct linked to both
> PEs even though only the 64bit TCE table cache can be invalidated on NPU.
> And a relatively recent skiboot detects this and prints errors.
> 
> This changes GPU's iommu_table_group_ops::set_window/unset_window to make
> sure that NPU PE is only linked to the table actually used by the hardware.
> If there are two tables used by an IOMMU group, the NPU PE will use
> the last programmed one which with the current use scenarios is expected
> to be a 64bit one.
> 
> Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/d41ce7b1bcc3e1d02cc9da3b83c0fe

cheers