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

[Alexey Kardashevskiy]

On 05/26/2015 08:16 PM, Paolo Bonzini wrote:
> On 26/05/2015 12:15, Alexey Kardashevskiy wrote:
> > There was a "[RFC PATCH 00/15] spapr: add support for PHB hotplug"
> > patchset from Mike, this patch added "unrealize" for spapr_phb:
> >
> > [RFC PATCH 05/15] spapr_pci: add PHB unrealize
> >
> > I believe I am dealing with the fixed version of this patch so I'll ask
> > Mike to respin it.
> >
> >
> > > > 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.
> > >
> > > The difference is that containers and aliases are resolved at the time
> > > the memory region tree is flattened, while IOMMU regions are resolved
> > > at run time.
> >
> > So they are not parts of flattened view and I should be able to
> > add/remove these IOMMU subregions any time I like?
>
> Yes.


I got lost here:

>>> 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.
>>
>> Unfortunately it's not so easy...


Uff. Tricky :)

memory_region_del_subregion() is not unparenting but just a wrapped 
object_unref(), right? But since iommu MR are resolved dynamically, the 
whole conversation we are having here now has nothing to do with my&Mike 
concern what we can and cannot do with DMA windows here. Is this correct?



--
Alexey