Re: [Qemu-devel] [PATCH qemu v7 06/14] spapr_iommu: Introduce "enabled" state for TCE table

[David Gibson]

On Tue, May 26, 2015 at 01:05:56AM +1000, Alexey Kardashevskiy wrote:
> Hi Paolo,
> 
> I have had a conversation with Mike and it turns out I am not allowed to
> create/remove memory regions dynamically (docs/memory.txt:101); otherwise
> "destroying regions during reset causes assertion in RCU thread during
> PHB/IOMMU unplug/unparent". Is it because patch just missing some
> unref()/unparent() call or it is totally wrong and I have to implement
> subregions (on a PCI bus address space) myself if I want dynamic DMA
> windows? Thanks!

So, the sentences after that one note an exception for alias and
container regions.  I think iommu regions should behave similarly - in
a sense they're just a procedurally generated collection of alias
regions.

If it's not true now that they can be unparented at any time like
alias regions, we should probably try to make it true.

-- 
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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