Re: [Qemu-devel] [PATCH 3/4] vfio: Move container list to iommu MemoryRegion

[Paolo Bonzini]

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Il 26/04/2013 13:31, David Gibson ha scritto:
>> You need to add this capability to VFIO's MemoryListener (either
>> the one that's already there, or a new one), looking for IOMMU
>> regions in the region_add callback.
> 
> Putting it in the MemoryListener doesn't work.  First, there could
> be multiple listeners if there are multiple containers attached to
> the MemoryRegion - the information we have here needs to be per 
> MemoryRegion.

There's no fundamental reason for VFIO to use multiple
MemoryListeners.  It could use one for all VFIO instances.

> More importantly, what I'm working towards here is vfio support for
> guest visible IOMMUs that don't have all of guest RAM mapped into
> them initially.  In that case there won't (and can't) be any
> MemoryListener at all.

Why?  All you want here is to look for appearance of an IOMMU
MemoryRegion in the flat representation of the AddressSpace.  That's
exactly what the MemoryListener does---of course that's a different
MemoryListener implementation than VFIO's current one.

The MemoryListener is used for a lot of different things, I find it
hard to believe that this is not a variation on one of them.

Paolo

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