[PATCH kernel] powerpc/powernv/ioda2: Gracefully fail if too many TCE levels requested

[Benjamin Herrenschmidt]

On Mon, 2017-02-27 at 22:00 +1100, Michael Ellerman wrote:
> > The alternative would be allocating TCE tables as big as PAGE_SIZE
> > but
> > only using parts of it but this would complicate a bit bits of code
> > responsible for overall amount of memory used for TCE table.
> > 
> > Or kmem_cache_create() could be used to allocate as big TCE table
> > levels
> > as we really need but that API does not seem to support NUMA nodes.
> 
> kmem_cache_alloc_node() ?

Is that 55 bits of address space (ie, 3 indirect levels + 64k pages) ?
Or only 39 (2 indirect level + 64k pages) ?

In the former case, I'm happy to limit the levels to 3 for 64K pages,
55 bits of TCE space is more than enough. 39 isn't however.

Cheers,
Ben.