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

From: David Gibson
Subject: Re: [Qemu-devel] [PATCH qemu v7 06/14] spapr_iommu: Introduce "enabled" state for TCE table
Date: Tue, 26 May 2015 12:46:28 +1000
User-agent: Mutt/1.5.23 (2014-03-12)

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

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_!

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