# Re: \[PATCH kernel v12 27/34\] powerpc/powernv: Implement multilevel TCE tables

- From: David Gibson \<hidden\>
- Date: 2015-06-09 04:57:45 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2015/06/4511586
- Thread: https://ratatoskr.run/linuxppc-dev/2015/06/4509623/t.md

```text
On Fri, Jun 05, 2015 at 04:35:19PM +1000, Alexey Kardashevskiy wrote:
> TCE tables might get too big in case of 4K IOMMU pages and DDW enabled
> on huge guests (hundreds of GB of RAM) so the kernel might be unable to
> allocate contiguous chunk of physical memory to store the TCE table.
> 
> To address this, POWER8 CPU (actually, IODA2) supports multi-level
> TCE tables, up to 5 levels which splits the table into a tree of
> smaller subtables.
> 
> This adds multi-level TCE tables support to
> pnv_pci_ioda2_table_alloc_pages() and pnv_pci_ioda2_table_free_pages()
> helpers.
> 
> Signed-off-by: Alexey Kardashevskiy <redacted>

Reviewed-by: David Gibson <redacted>

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson
```

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