On Tue, 2014-10-21 at 11:07 +0200, Alexander Graf wrote: > > > > Am 21.10.2014 um 07:26 schrieb Knut Omang <knut.om...@oracle.com>: > > > >> On Tue, 2014-10-21 at 01:29 +0200, Alexander Graf wrote: > >> > >> > >>> Am 21.10.2014 um 00:34 schrieb Knut Omang <knut.om...@oracle.com>: > >>> > >>> This patch set changes the data structure used to handle address spaces > >>> within > >>> the emulated Intel iommu to support traversal also if bus numbers are > >>> dynamically > >>> allocated, as is the case for devices that sit behind root ports or > >>> downstream switches. > >>> This means that we cannot use bus number as index, instead a QLIST is > >>> used. > >>> > >>> This requires a change in the API for setup of IOMMUs which is taken care > >>> of by > >>> the first patch. The second patch implements the fix. > >> > >> Are you sure that this works on real hardware? How does that one > >> communicate sub-bridge liodns to the iommu? How do they get indexed > >> from software? > > > > I do not claim to fully understand the details of how this is > > implemented in hardware, but I believe the implementation I propose here > > should be functionally equivalent to what the Intel IOMMU offers, and > > similar to the original implementation here, except that the data > > structure is valid also before enumeration when behind buses. > > Can you please give me a pointer to the vt-d spec's section that explains > iommu behavior behind bridges? > > I've also added Alex W who has played with PCI bridges behind iommus quite a > bit recently. > > > > > After enumeration, the only difference would be that during > > invalidation, there is a list search for the right bus rather than an > > index lookup as before, slightly less efficient but at the benefit of > > being independent of bus numbering during setup. > > I don't think the implementation is bad, I'm just not sure that it follows > the spec, > so I want to confirm :).
http://www.intel.com/content/dam/www/public/us/en/documents/product-specifications/vt-directed-io-spec.pdf Knut > Alex > > > > > Wrt the currently implemented IOMMUs for other architectures, they were > > all ignoring the bus argument anyway, so the API change did not make > > much difference. > > > > Knut > > > >> Alex > > > >
