Re: [Qemu-devel] [PATCH 1/7] vfio: Remove unneeded union from VFIOContainer

[David Gibson <david@gibson.dropbear.id.au>]

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On Thu, Sep 24, 2015 at 10:01:55AM -0600, Alex Williamson wrote:
> On Thu, 2015-09-24 at 14:33 +1000, David Gibson wrote:
> > Currently the VFIOContainer iommu_data field contains a union with
> > different information for different host iommu types.  However:
> >    * It only actually contains information for the x86-like "Type1" iommu
> >    * Because we have a common listener the Type1 fields are actually used
> > on all IOMMU types, including the SPAPR TCE type as well
> >    * There's no tag in the VFIOContainer to tell you which union member is
> > valid anyway.
> 
> FWIW, this last point isn't valid.  The IOMMU setup determines which
> union member is active and the listener and release functions are
> specific to the union member.  There's no need whatsoever for a tag to
> keep track of the union member in use.  The only problem is that the
> union solved a problem that never really came to exist, so we can now
> remove it and simplify things.

I could argue some of the details there, but none of them are really
important.

> I'll remove this last bullet point unless there's some objection.
> Thanks,

That's fine.

-- 
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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