On Wed, May 15, 2013 at 01:32:50PM +1000, David Gibson wrote: > On Tue, May 14, 2013 at 08:51:08PM -0600, Alex Williamson wrote: > > On Wed, 2013-05-15 at 11:33 +1000, David Gibson wrote: > > > On Tue, May 14, 2013 at 11:15:26AM -0600, Alex Williamson wrote: > > > > On Tue, 2013-05-14 at 19:13 +1000, David Gibson wrote: [snip] > > Trying to make sure I understand why guest_iommus is a list. We can > > have multiple guest iommus, but in the majority of those cases I would > > expect only one iommu per VFIOAddressSpace. So if the listener is for > > this space, we only add the relevant iommu and not all of the iommus in > > the machine. > > That's what we do - we only add notifiers for iommu regions that > appear within the relevant address space. It's a list because at > least theoretically there could be more than one iommu region in the > AS, although I don't know of any real cases where that would be true. > > > > Actually maybe two guest iommu ranges are common for spapr > > per space, a 32bit and a 64bit range? > > I think 64-bit DMA windows on PAPR are usually just mapped to RAM with > a fixed offset, rather than having TCEs (page table). That might well > introduce some extra complexities in how we mirror that into VFIO, but > it's not directly relevant to this point.
So, since I wrote that I've heard from Ben that while current machines
don't have multiple (translated) iommu windows, this could well be
found on future machines.
--
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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