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Subject: Re: [PATCH kernel] powerpc/powernv/ioda2: Gracefully fail if too
 many TCE levels requested
From: Benjamin Herrenschmidt <benh@au1.ibm.com>
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To: Alexey Kardashevskiy <aik@ozlabs.ru>, Michael Ellerman
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Date: Mon, 06 Mar 2017 14:36:09 +1100
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On Mon, 2017-03-06 at 12:28 +1100, Alexey Kardashevskiy wrote:
> 8192*8192*8192*65536>>40 = 32768TB of addressable memory (but there is no
> good reason not to use huge pages);

No, 39 bits is half a TB. That's not enough.

> 8192*8192*8192*4096>>40 = 2048TB or addressable memory (even with 2
> indirect levels but we can have all 5 levels with 4K IOMMU pages).
> 
> Looks enough to me...
> 
> And in this particular patch I am not limiting anything, I just replace
> already existing EEH condition with -EINVAL. If it is this important to
> have all 5 levels, then we can switch from alloc_pages_node() to
> kmem_cache_alloc_node(), in a separate patch.
> 
> 
> --